The urinary system

This process will produce waste products

- If accumulate in the cells, these products could reach toxic concentration and threaten homeostasis
- These waste products must be excreted from the cells
- What is excretion? Is it different from elimination?
– Excretion: Removal of metabolic wastes
– Elimination: the discharge of undigested or unabsorbed food from the digestive tract


Learning objectives:
– Identify the principal metabolic waste product and the organs that excrete them
– Label a diagram of the urinary system and give the function of each structure
– Describe a nephron and give the functions of the following structures:
Bowman’s capsules
Glomerulus
Renal tubules
Collecting ducts
Afferent arterioles
Efferent arterioles
– Label a diagram of a nephron
– Trace a drop of filtrate from glomerulus to urethra, listing in sequence each structure through which it passes
– Describe the process of urin formation and give the composition of urine
– Summarize the regulation of urine volume including the role of ADH
– Summarize the functions of the kidney in maintaining homeostasis
– Describe the process of urination

Introductions

In order to live properly, cells of our body carry on metabolic activities
This process will produce waste products
If accumulate in the cells, these products could reach toxic concentration and threaten homeostasis
These waste products must be excreted from the cells
What is excretion? Is it different from elimination?
– Excretion: Removal of metabolic wastes
– Elimination: the discharge of undigested or unabsorbed food from the digestive tract
The principal of metabolic wastes:
– Water
– Carbon dioxide
– Wastes that contain nitrogen
Amino acids and nucleic acids contain nitrogen
If excess amino acids are broken down, the nitrogen-containing amino group is removed
The amino group is chemically converted to amonia and then to urea.
Nucleic acid is broken down to uric acids
Both urea and uric acids are transported from the liver to the kidney by the circulatory system
Metabolic wastes are excreted mainly by urinary system
Other systems involved in the disposal of metabolic wastes are:
– The skin
Via the sweat glands
Only 5-10% secreted through the skin
Sweat contains: the same substances as urine (water, salt, and nitrogen wastes) but much more dilute
– The lungs
CO2 and water (in the form of water vapor)
– Digestive system
Liver secretes bile pigments (leave the body with the feses)

The urinary system

The principal of the urinary system consists of:
– Kidney
A pair of kidneys
Remove waste from the blood
Produce urine
– Urinary bladder
The site storage for urine (temporary)
– Ureters
Conduct urine from the kidneys to the urinary bladder
– Urethra
Discharge urine from the body
This is a single urethra

Kidneys

There are two of them
Located behine the peritoneum lining the abdominal cavity (described as retroperitoneal)
They are located exactly near the posterior body just below the diapgragm
They are protected by the lower ribs
Each kidney receives blood from a renal artery and is drained by a renal vein
Their shape is like a large, dark red lima bean (about the size of a fist)
The kidneys are connected with the blood vessels and urethra at the hilus
They are covered by a strong capsule of connective tissue called renal capsule
The kidney consists of:
Outer renal cortex
Inner renal medula
Contais between 5 – 18 renal pyramids (triangular structures)
The tip of each pyramid is called a renal papilla
Each renal papilla extend into a small tube called a calyx
Each papilla has pores (the openings of collecting ducts through which urine passes into the calyx)
These calyces join to form a large cavity called renal pelvis
As urine produced, it flows through the renal pelvis and into the ureter

The Nephrons

These are microscopic units of Kidney
Each kidney contains > 1 million nephrons
These structures filter the blood and produce urine
The main structure of each nephron:
– Renal corpuscle
– Renal tubule
– Renal corpuscle
The site of blood filtration
Consists of glomerulus (a network of capillaries)
This glomerulus is surrounded by Bowman’s capsule (cuplike structure) (Figure 16.4)
The blood flows into the glomerulus through a small afferent arteriole and leave it through efferent arteriole
This arteriole conduct blood to a second set of capillaries called peritubular capillaries
Bowman’s capsule has an opening in its bottom
This opening is the way through which the filtrate passes into the renal tubule
– Renal tubule
Tube through which the filtrate flows
Along this long tube, substances needed by the body are returned to the blood
Wastes, excess water, and others not needed by the body pass into the collecting duct as urine
The first part of the renal tubule is called proximal convulated tubule
This continous with loop of Henle
This loop continous with distal convulated tubule
Urine from this distal convulated tubule of several nephron drain into a collecting duct
Part of distal convulated tubule curves upward and contact the afferent arteriole
The cells that make this contact form juxtaglomerular apparatus (Fig. 16.5)
This structure secretes enzyme renin (activator of a hormone called angiotensin that regulate blood pressure)
Note that:
– The renal corpuscle, the proximal convoluted tubule, and distal covoluted tubule of each nephron are located within the renal cortex
– Loop of Henle dip down into the medulla

The process of urine production

This process involves three processes:
– Glomerular filtration
– Tubular reabsorption
– Tubular secretion

Glomerular filtration

This is the first step of urine production
The process itself:
– The diameter of afferent arteriole is larger than that of efferent arteriole
– Resulting in the volume of blood enters the glomerulus is more rapidly than it can leave
– This cause the blood pressure in the glomerular capillaries become higher than other capillaries
– This pressure will force plasma and dissolved substances out of the capillaries and into the Bowman’s capsule
– Therefore, the filtrate consists of blood plasma that concains small dissolved molecules
– This can be considered that the glomerular filtration is not a selective process
– Some useful substances present in the filtrate:
Glucose
Amino acids
Salts
– Blood cells and proteins are too large to pass through the wall of the capillaries and the capsule
– If those two components present in the urine, it means that a problem occurs with the glomerular filtration

Rate of filtration

Each minutes, 25% of the cardiac output is delivered to the kidneys
So, every 4 minutes, the kidney receives a volume of blood equal to the total volume of blood circulates in the body
Or this is equal to 180 L of filtrate produced per day
Common senses suggests that we could not excrete 180 L urine per day
If we were loosing fluid that quickly, dehydration would become a life threatening problem within a few moment

Tubular reabsorption

About 99% of the filtrate will be returned to the blood by tubular reabsorption
This leaves only 1.5 L to be excreted as urine within 24 hours period
This process is the job of the renal tubules and collecting duct
This process will prevent dehydration to occur
This process is a highly selective process
– Waste, surplus salts, and excess water are kept as part of the filtrate
– Glucose, amino acids, and other needed substances are reabsorbed into the blood
A few substances are actively secreted from the blood in the peritubular capillaries into the renal tubules
This tubular secretion is important in regulating the potassium and hydrogen ion concentration in the blood
Some toxic substances and certain drugs (penicillin) are remove from the body by this tubular secretion


Composition of urine

The composition of filtrate that reaches the ureter has been carefully adjusted
– The useful materials have been returned to the blood while waste and excess materials have been cleared from the blood
The adjusted filtrate is then called urine.
The urine composed of:
– App. 96% water
– 2.5% nitrogen waste (mainly urea)
– 1.5% salts
– Traces of other substances
Healthy urine is sterile
However, it rapidly decomposes when exposed to bacterial action, forming ammonia and other product
The ammonia causes diaper rush in infants

The role of ADH to regulate the urine volume

The volume of urine produced by the kidney is proportionally related to the amount of water intake
In this case:
– Water is absorbed from the digestive tract into the blood
– Excess water is removed from the blood by the kidneys
– By regulating urine volume, the body maintains a steady volume and composition of blood
– The kidneys receive information about the state of the blood indirectly (Fig. 16.7)
In the case of low fluid intake, the body begins to dehydrate
This will causethe volume of blood decrease, and the conc. of dissolved salt is greater
This results in an increase in the osmotic pressure of the blood
This changes will cause the specialized receptors in the brain, heart, and in certain blood vessels to respond
Besides that, the posterior of pituitary glands responds by releasing antidiuretic hormone (ADH)
ADH serve as chemical messenger carrying information from the brain to the distal convoluted tubules and collecting ducts of the kidney
The effect of this signal is to cause the wall of ducts to become more permeable to water.
Therefore, more water is reabsorbed into the blood
This will cause the volume of the blood to increase and the homeostasis of fluid volume is restored
Only a small amount of concentrated urine is produced

– In the case of large amount of water intake
The blood become dilluted and its osmotic pressure falls
Release of ADH by the pituitary gland decreases
This reduces the amount of water reabsorbed from the distal convoluted tubules and collecting ducts
As a result, a large volume of dilluted urine is produced

Possible dissorders:
– Not sufficient of ADH produced
Water is not efficiently reabsorbed from the ducts
This results in large volume of urine produced
This condition is called diabetes insipidus
A person with this dissorder may excrete up to 25 quarts of urine per day
He/she must drink almost continually to offset this fluid loss
– It is clear that ADH regulates excretion of water by the kidney
– Salts excretion is regulated by hormones (mainly aldosteron produced by the adrenal glands

Diuretics

These are chemicals compounds contained in coffee, tea, alcoholic beverage
These can increase the volume of urine by inhibiting the reabsorption of water
Some inhihit secretion of ADH
Some act directly on the tubules in the kidneys

The role of kidneys in maintaing homeostasis

Their functions include:
– Excretion of metabolic wastes, such as water, urea, and uric acid
– Disposal of excess water and salts
– Regulation of acid-base (pH level of the blood and body fluids. Acid and base that are not needed are excreted in the urine
– Secretion of regulatory substances
The kidney secretes the enzyme renin
This enzyme is important in regulating blood pressure
Kidney also secretes a hormone (erythropoietin) that regulates the production of blood cells

Transport of urine to the bladder

Urine passes from kidneys through the paired ureter
– These are ducts about 25 cm long
– Conduct the kidneys to the urinary bladder
The urine is forced along through the ureter by peristaltic contraction
Once reach the bladder, it is temporary stored there
Urinary Bladder:
– It is lined with a mucous membrane
– The membrane has folds called rugae
– With this rugae, the bladder has the capacity of 800 ml of urine
The urine leaves the body through the urethra
Urethra:
– A duct leading to the outside of the body
– In male, it is lengthy and passes through the prostate gland and the penis
– In female, it is short and transport the urine only
Its opening is just above the opening into the vagina
Because it is short, it is more susseptible to bacterial infection than male urethra

Urination or micturation

The process of emptying the bladder and expelling urine
The process:
– When the volume of the bladder reach 300 mL, special nerve endings in the bladder wall are stimulated
– These receptors send send neural messages to the spinal cord
– This initiates a urination reflex
– This reflex contract the bladder wall and also relaxes the internal urethral sphincter (a ring of smooth muscle at the upper end of the urethra)
– This stimulate a concious desire to urinate
At appropriate time and place, the external urethral sphincter is voluntarily relaxed
This allows urination to occur
This voluntary control cannot occur in immature nervous system
That’s why most babies under the age of 2 automatically urinate everytime the bladder fills

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Our Skin

– The skin is the outer protective covering of the body
– It has a tough structure
– It form integumentary system together with:
Its glands
Its hair
Nails
– This part of our body (the skin) is the most familiar for us
– Attentions normally given to the skin + components:
We scrub, cream, and coat it with make up
We cut, shave, and curl its hair
We manicure its nails


Learning Objectives
– List the 6 functions of the skin and explain how each is important in homeostasis
– Compare the structure and functions of the epidermis with that of the dermis
– Describe the subcutaneus layer
– Describe the functions of sweat glands and sebaceous glands
– Give the functions of hair and nails and describe the structure of hair
– Explain the function of melanin
Introduction
– The skin is the outer protective covering of the body
– It has a tough structure
– It form integumentary system together with:
Its glands
Its hair
Nails
– This part of our body (the skin) is the most familiar for us
– Attentions normally given to the skin + components:
We scrub, cream, and coat it with make up
We cut, shave, and curl its hair
We manicure its nails
The skin is important in communication.
– You may shake hands, stroke, kiss, and squeeze
Involuntary change in the skin reflect emotional state
– You may blush with embarrassment
– You may blanch with fear or rage
– You may redden with excertion
– You may sweat excessively when anxious
Skin can also be used as general health indicators
– Appearance
– Coloration
– Temperature
– Feel

The six functions of the skin

To protect the body against injury and against disease organisms
– The skin is the body’s first line of defense against harmful bacteria & other agents of disease
To receive the information about the outside world
– Within the skin there are sensory receptors
– These receptors detect touch, pressure, heat, cold, and pain
To prevent drying out
– The skin prevent loss of body fluid so that the cells do not dry out
To help maintain body temperature
– Involves the role of capillary network and sweat glands in the skin
– Sweating is a mechanism to maintain the body temperature (regulating the body’s temperature system)
The skin has sweat gland
– Function in excreting waste and excessive water from the body
The skin contains important compound for Vit D
– It is converted into vit D if exposed to the UV rays of the sun

The anatomy of the skin

The skin consists of two main layers:
– The outer epidermis
– The inner dermis
Beneath the skin is an underlaying subcutaneous layer

(gambar)


The epidermis

The thickness of the epidermis over the body is about a piece of paper
However, it consists of several sublayers
It consists of stratified epithelial tissue
The outer cells are continuously wear off
They are immediately replaced by new cells
New epidermal cells are constantly produced in the deepest sublayer of the epidermis
Each cell is mostly filled with a tough waterproofing protein called keratin
The cells at the surface of the skin resemble dead scales
They are closely packed together and serve as a waterproof protective covering for the body

The dermis

This is a thick layer of skin beneath the epidermis (Fig. 3.1)
It consists of dense connective tissue (mainly composed of collagen fiber)
The functions of collagen fiber:
– Responsible for mechanical strength of the skin
– Resposible for skin plasticity
Components found in the dermis:
– Blood vessels
– Nerve system
– Follicles
– Glands
The upper portion of the dermis, has many small finger-like elevations
These project into the epidermal tissue
In these elevations, extensive network of capillaries functions:
– To deliver O2 and nutrients to the cells of epidermis
– In regulating temperature


The subcutaneous layer

The subcutaneous layer beneath the dermis is also called superfisial fascia
This layer consists of:
– Loose conective tissue
– A lot of adipose (fat) tissue
Help protect underlaying organs from mechanical shock
Insulate body (conserve heat)
As food source
Responsible for characteristic male and female body shape
This layer attach the skin to the muscle and other tissues beneath

Sweat glands and sebaceous glands


Sweat glands
– Each gland is a tiny coiled tube in the dermis or subcutaneous
– It has a duct that extend up through the skin and opens onto the surface (Fig 3.1)
– In all area of the skin, there are 3 millions of them
– These glands help to maintain the body temperature
An increase in body temperature is caused by muscle contraction and metabolic activity
Heat is needed for evaporation
The body become cooler as the sweat evaporates from the body
– Sweat glands excrete water, salts, and small amount of nitrogen wastes
– Certain sweat glands are sometimes associated with hair
– These are concentrated in a few specific areas of the body, such as:
Armpits
Genital area
– These glands discharge into the folicle
– Their secretion is thick, sticky, and mainly odorless
– However, some bacteria that inhabit the skin surface are able to decompose this secretion
– This bacterial activity cause the secretes become odorous
– That’s why we need deodorant and antiperspirant to replace the odor and reduce moisture
– Emotional stress or sexual stimulation promote secretion of these glands
Sebaceous glands:
– Also known as oil glands
– Generally attach to hair follicles
– They are connected to each hair follicle by little ducts (the site through which the glands release their secretes or an oily substance called sebum)
– They are found numeously on the face and sculps
– The functions of this sebum:
Lubricate the surface of the skin
Oils the hairs
Prevent water loss
Inhibit bacterial growth
As antifungal
– During childhood, the glands are relatively inactive
– At puberty, they are activated by increased secretion of male hormone (both in male and females)
– The hormon activity can lead to acne
– This condition is very common during adolescence

– In some cases:
The sebum accumulates in the duct of the subaceous glands and hair folicle and block it, forming a blackhead (comedo)
In a blackhead, sebum and dead cells contaning the dark pigmen melanin block the duct
The Melanin cause black color of the skin
Sometimes the ducts of the sebaceous gland ruptures
This allowing the sebum spill into the dermis
This cause the skin to become inflamed and a pimple may form

Hair and nails

Hair is found on all skin surfaces, except the palm and soles
It serves a protective function
The components of hair:
– The shaft: the hair that we see
– The root: the portion below the skin surface
Hair follicle (fig. 3.2): the root + epithelial and connective tissue
– Get supply of nutrients from connective tissue that contains capillaries
Hair:
– Each hair consists of cells
– The cells multiply, manufacture keratin as they move outward, and die
The shaft:
– Consists of dead cells and their products
– We can cut it without any sensation of pain
The hair follicle
– Control the growth of hair
– As long as it remains intact, new hair will continue to grow
– The follicle is associated with tiny bundles of smooth muscle
– It contract in response to cold or fear hair stand up
Nails:
– Help protect the end of the fingers and toes
– They develop from horny epidermal cells
– Consists mainly of a closely compressed, tough keratin
– The actively growing area is the white crescent (lanula) at the base of the nails
– Beneath the nails, capillaries are found (make the to look pink)


Melanin

At the lowest layer of the epidermis, there are cells that produce pigment granules distributed scatteredly
These pigment granules are composed of a type of protein called melanin
The melanin gives color to hair and skin
Skin color is inherited
A person with dark skin, the pigment cells are more active and produce more melanin
Melanin is an important protective screen against the sun as it absorb UV
When the melanin is not able to absorb all the UV rays, the skin become inflame or sunburned
Excessive exposure to the sun rays can cause:
Skin cancer
Wrinkles
Dark-skinned people have more melanin
They are more resistance to sun rays that can cause wrinkles, sunburn, or even cancer
Other type of skin pigment:
Carotene (yellowish pigment found in asian people)

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The Reproductive System

 The testis produces sperm and testosterone
 Enclosed in a hanging sac called the scrotum
 Sperm need cooler temperature to develop
 Spermatogenesis occurs in the seminiferous tubules
 Sperm are then transferred to the epididymis for storage and maturation
 From there to the vas deferens & its ampulla
 At ejaculation they pass into the urethra which empties through the penis
 Accessory sex glands:
 Empty their secretions into the ducts during ejaculation
 Include the seminal vesicles, prostate gland, and bulbourethral glands


 Modified sweat glands consisting of 15-25 lobes that radiate around and open at the nipple
 Areola – pigmented skin surrounding the nipple
 Suspensory ligaments attach the breast to underlying muscle fascia
 Lobes contain glandular alveoli that produce milk in lactating women
 Compound alveolar glands pass milk to lactiferous ducts, which open to the outside

Sexually Transmitted Diseases

 STDs are diseases that are spread from one person to another through sexual contact
 They include:
 Acquired Immune Deficiency Syndrome (AIDS)
 Caused by the human immunodeficiency virus (HIV)
 Gonorrhea
 Caused by the bacterium Neisseria gonorrhoeae
 Chlamydia
 Caused by the bacterium Chlamydia trachomatis
 Syphilis
 Caused by the bacterium Treponema pallidum
 Genital Herpes
 Caused by the herpes simplex virus type 2 (HSV-2)
 Most common STD in the US
 Genital Human Papillomavirus (HPV)
 Some types cause genital warts
 HPV is a key factor in virtually all types of cervical cancer
Structure of Lactating Mammary Glands
 Fertilization of the egg occurs high in the Fallopian tubes (also called uterine tubes or oviducts)
 The fertilized egg is now called a zygote
 It is transported to the uterus
 A muscular pear-shaped organ about the size of a fist
 It narrows to a muscular ring called the cervix
 Leads to the vagina
 The fertilized egg is pushed down the oviducts by the rhythmic contraction of its smooth muscles
 The journey takes 5-7 days
 The uterus is lined with a stratified epithelial membrane called the endometrium
 The zygote attaches to this layer and begins embryonic development!
 If the egg is not fertilized, the surface layer of the endometrium is shed during menstruation
 The underlying layer generates a new surface layer during the next cycle

Hormones Coordinate the Reproductive Cycle

The female reproductive cycle is composed of two distinct phases separated by ovulation

Follicular phase
Egg reaches maturation

Ovulation
Ovary ruptures and releases the egg

Luteal phase
Body continues to prepare for pregnancy

A family of hormones coordinates these phases

Follicular Phase

 Development of the egg within the ovary
 The oocyte and its surrounding mass of tissue is called the follicle
 FSH secretion triggers the maturation of several follicles and resumption of meiosis in their oocytes
 But only one achieves full maturity
 FSH also causes the ovary to secrete estrogen
 Negative feedback by estrogen, causes the hypothalamus to stop the pituitary’s FSH output
Luteal Phase

 The body is prepared for fertilization
 Hypothalamus causes the anterior pituitary to begins secreting luteinizing hormone (LH)
 LH inhibits further estrogen production
 It also causes the wall of the follicles to burst
 Oocyte is ovulated into oviducts
 LH directs the repair of the ruptured follicle, which becomes the corpus luteum
 The corpus luteum begins to secrete the hormone progesterone
 Progesterone inhibits FSH
 It also thickens the endometrium preparing for fertilization
 If fertilization does not occur, progesterone production stops and the luteal phase ends
 Thickened endometrial layer sloughs off
 This causes the bleeding associated with menstruation
 If fertilization does occur, the corpus luteum is maintained by human chorionic gonadotropin (hCG)
 hCG is a hormone produced by the embryo
 It is tested for in all pregnancy tests
 Two other hormones are of importance
 Prolactin
 Stimulates milk production
 Oxytocin
 Initiates milk release
 Induces labor
Fertilization and Fate of the Zygote
The Ovary and Formation of an Ovum

 At birth, a female’s ovaries contains all the oocytes she will ever produce
 ~ 2 million oocytes are arrested in prophase I of the first meiotic division
 At puberty, the release of FSH causes the resumption of meiosis I in a few oocytes
 However, only one becomes dominant and is ovulated
 Mature egg cells are called ova (singular, ovum)
 This cycle is repeated about every 28 days
Events of Oogenesis

 Production of female sex cells by meiosis
 In the fetal period, oogonia (2n ovarian stem cells) multiply by mitosis and store nutrients
 Primordial follicles appear as oogonia are transformed into primary oocytes
 Primary oocytes begin meiosis but stall in prophase I
 At puberty, one activated primary oocyte produces two haploid cells
 The first polar body
 The secondary oocyte
 The secondary oocyte arrests in metaphase II and is ovulated
 If penetrated by sperm the second oocyte completes meiosis II, yielding:
 One large ovum (the functional gamete)
 A tiny second polar body
Mechanism and Effects of Testosterone Activity

 Testosterone is synthesized from cholesterol
 It must be transformed to exert its effects on some target cells
 Prostate – it is converted into dihydrotestosterone (DHT) before it can bind within the nucleus
 Neurons – it is converted into estrogen to bring about stimulatory effects
 Testosterone targets all accessory organs and its deficiency causes these organs to atrophy
 Male hormones make their appearance at puberty and induce changes in nonreproductive organs, including
 Appearance of pubic, axillary, and facial hair
 Enhanced growth of the chest and deepening of the voice
 Skin thickens and becomes oily
 Bones grow and increase in density
 Skeletal muscles increase in size and mass
 Testosterone is the basis of libido in both males and females

Female Reproductive Organs

 Ovaries are the primary female reproductive organs
 Make female gametes (ova)
 Secrete female sex hormones (estrogen and progesterone)
 Accessory ducts include uterine tubes, uterus, and vagina
 Internal genitalia – ovaries and the internal ducts
 External genitalia – external sex organs
 Labia major (homologous to male scrotum)
 Labia minor (homologous to ventral penis)
 Clitoris (homologous to the penis)
 Erectile tissue hooded by the prepuce
 The exposed portion is called the glans
Male Reproductive Organs

 The testis produces sperm and testosterone
 Enclosed in a hanging sac called the scrotum
 Sperm need cooler temperature to develop
 Spermatogenesis occurs in the seminiferous tubules
 Sperm are then transferred to the epididymis for storage and maturation
 From there to the vas deferens & its ampulla
 At ejaculation they pass into the urethra which empties through the penis
 Accessory sex glands:
 Empty their secretions into the ducts during ejaculation
 Include the seminal vesicles, prostate gland, and bulbourethral glands
Evolution of Reproduction Among the Vertebrates

Vertebrate sexual reproduction evolved in the ocean before vertebrates colonized land
Most marine bony fish use external fertilization
Male and female gametes are released into the water where fertilization occurs
Most other vertebrates use internal fertilization
Male gametes are introduced into the female reproductive tract

 There are three strategies for internal fertilization
1. Oviparity
 Fertilized eggs are deposited outside mother’s body to complete their development
2. Ovoviviparity
 Fertilized eggs are retained within the mother to complete their development
 Young obtain nourishment from egg yolk
3. Viviparity
 Fertilized eggs are retained within the mother to complete their development
 Young obtain nourishment from mother’s blood

Mammalian Breeding Patterns

 Some mammals are seasonal breeders
 Others have reproductive cycles
 Periodic release of a mature ovum (ovulation)
 Most female mammals have estrous cycles
 Females sexually receptive to males only around time of ovulation (estrus)
 Apes and humans have menstrual cycles
 Females bleed when shedding inner lining of the uterus
 Can copulate at any time in their cycle
 Cats and rabbits are induced ovulators
 Ovulation only after copulation due to LH secretion

Three Types of Mammalian Development

 Monotremes are oviparous
 Lay eggs
 Young hatchlings obtain milk by licking mammary glands (they lack nipples)

 Marsupials are viviparous
 Give birth to incompletely developed fetuses
 Complete development in mother’s pouch
 Obtain food from nipples in mammary glands

 Placentals are viviparous
 Retain young in uterus for long periods of development
 Fetuses are nourished by the placenta

How Sex is Determined in Mammals

 In mammals, sex is determined early in embryonic development
 Embryonic gonads are indifferent
 Y chromosome converts them to testes
 Responsible gene is SRY
 Sex-determining region of the Y chromosome

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Pollution

INTRODUCTION

Pollution, contamination of Earth’s environment with materials that interfere with human health, the quality of life, or the natural functioning of ecosystems (living organisms and their physical surroundings). Although some environmental pollution is a result of natural causes such as volcanic eruptions, most is caused by human activities.


There are two main categories of polluting materials, or pollutants. Biodegradable pollutants are materials, such as sewage, that rapidly decompose by natural processes. These pollutants become a problem when added to the environment faster than they can decompose (see Sewage Disposal). Nondegradable pollutants are materials that either do not decompose or decompose slowly in the natural environment. Once contamination occurs, it is difficult or impossible to remove these pollutants from the environment.
Nondegradable compounds such as dichlorodiphenyltrichloroethane (DDT), dioxins, polychlorinated biphenyls (PCBs), and radioactive materials can reach dangerous levels of accumulation as they are passed up the food chain into the bodies of progressively larger animals. For example, molecules of toxic compounds may collect on the surface of aquatic plants without doing much damage to the plants. A small fish that grazes on these plants accumulates a high concentration of the toxin. Larger fish or other carnivores that eat the small fish will accumulate even greater, and possibly life-threatening, concentrations of the compound. This process is known as bioaccumulation.
II. IMPACTS OF POLLUTION
Because humans are at the top of the food chain, they are particularly vulnerable to the effects of nondegradable pollutants. This was clearly illustrated in the 1950s and 1960s when residents living near Minamata Bay, Japan, developed nervous disorders, tremors, and paralysis in a mysterious epidemic. More than 400 people died before authorities discovered that a local industry had released mercury into Minamata Bay. This highly toxic element accumulated in the bodies of local fish and eventually in the bodies of people who consumed the fish. More recently research has revealed that many chemical pollutants, such as DDT and PCBs, mimic sex hormones and interfere with the human body’s reproductive and developmental functions. These substances are known as endocrine disrupters. See Occupational and Environmental Diseases.
Pollution also has a dramatic effect on natural resources. Ecosystems such as forests, wetlands, coral reefs, and rivers perform many important services for Earth’s environment. They enhance water and air quality, provide habitat for plants and animals, and provide food and medicines. Any or all of these ecosystem functions may be impaired or destroyed by pollution. Moreover, because of the complex relationships among the many types of organisms and ecosystems, environmental contamination may have far-reaching consequences that are not immediately obvious or that are difficult to predict. For instance, scientists can only speculate on some of the potential impacts of the depletion of the ozone layer, the protective layer in the atmosphere that shields Earth from the Sun’s harmful ultraviolet rays.
Another major effect of pollution is the tremendous cost of pollution cleanup and prevention. The global effort to control emissions of carbon dioxide, a gas produced from the combustion of fossil fuels such as coal or oil, or of other organic materials like wood, is one such example. The cost of maintaining annual national carbon dioxide emissions at 1990 levels is estimated to be 2 percent of the gross domestic product for developed countries. Expenditures to reduce pollution in the United States in 1993 totaled $109 billion: $105.4 billion on reduction, $1.9 billion on regulation, and $1.7 billion on research and development. Twenty-nine percent of the total cost went toward air pollution, 36 percent to water pollution, and 36 percent to solid waste management.
In addition to its effects on the economy, health, and natural resources, pollution has social implications. Research has shown that low-income populations and minorities do not receive the same protection from environmental contamination as do higher-income communities. Toxic waste incinerators, chemical plants, and solid waste dumps are often located in low-income communities because of a lack of organized, informed community involvement in municipal decision-making processes.
III. TYPES OF POLLUTION
Pollution exists in many forms and affects many different aspects of Earth’s environment. Point-source pollution comes from specific, localized, and identifiable sources, such as sewage pipelines or industrial smokestacks. Nonpoint-source pollution comes from dispersed or uncontained sources, such as contaminated water runoff from urban areas or automobile emissions.
The effects of these pollutants may be immediate or delayed. Primary effects of pollution occur immediately after contamination occurs, such as the death of marine plants and wildlife after an oil spill at sea. Secondary effects may be delayed or may persist in the environment into the future, perhaps going unnoticed for many years. DDT, a nondegradable compound, seldom poisons birds immediately, but gradually accumulates in their bodies. Birds with high concentrations of this pesticide lay thin-shelled eggs that fail to hatch or produce deformed offspring. These secondary effects, publicized by Rachel Carson in her 1962 book, Silent Spring, threatened the survival of species such as the bald eagle and peregrine falcon, and aroused public concern over the hidden effects of nondegradable chemical compounds.

A. Air Pollution
Human contamination of Earth’s atmosphere can take many forms and has existed since humans first began to use fire for agriculture, heating, and cooking. During the Industrial Revolution of the 18th and 19th centuries, however, air pollution became a major problem. As early as 1661 British author and founding member of the British Royal Society John Evelyn reported of London in his treatise Fumifugium, “… the weary Traveller, at many Miles distance, sooner smells, than sees the City to which he repairs. This is that pernicious Smoake which fullyes all her Glory, superinducing a sooty Crust or Furr upon all that it lights.…”
Urban air pollution is commonly known as smog. The dark London smog that Evelyn wrote of is generally a smoky mixture of carbon monoxide and organic compounds from incomplete combustion (burning) of fossil fuels such as coal, and sulfur dioxide from impurities in the fuels. As the smog ages and reacts with oxygen, organic and sulfuric acids condense as droplets, increasing the haze. Smog developed into a major health hazard by the 20th century. In 1948, 19 people died and thousands were sickened by smog in the small U.S. steel-mill town of Donora, Pennsylvania. In 1952, about 4,000 Londoners died of its effects.
A second type of smog, photochemical smog, began reducing air quality over large cities like Los Angeles in the 1930s. This smog is caused by combustion in car, truck, and airplane engines, which produce nitrogen oxides and release hydrocarbons from unburned fuels. Sunlight causes the nitrogen oxides and hydrocarbons to combine and turn oxygen into ozone, a chemical agent that attacks rubber, injures plants, and irritates lungs. The hydrocarbons are oxidized into materials that condense and form a visible, pungent haze.
Eventually most pollutants are washed out of the air by rain, snow, fog, or mist, but only after traveling large distances, sometimes across continents. As pollutants build up in the atmosphere, sulfur and nitrogen oxides are converted into acids that mix with rain. This acid rain falls in lakes and on forests, where it can lead to the death of fish and plants, and damage entire ecosystems. Eventually the contaminated lakes and forests may become lifeless. Regions that are downwind of heavily industrialized areas, such as Europe and the eastern United States and Canada, are the hardest hit by acid rain. Acid rain can also affect human health and man-made objects; it is slowly dissolving historic stone statues and building facades in London, Athens, and Rome.
One of the greatest challenges caused by air pollution is global warming, an increase in Earth’s temperature due to the buildup of certain atmospheric gases such as carbon dioxide. With the heavy use of fossil fuels in the 20th century, atmospheric concentrations of carbon dioxide have risen dramatically. Carbon dioxide and other gases, known as greenhouse gases, reduce the escape of heat from the planet without blocking radiation coming from the Sun. Because of this greenhouse effect, average global temperatures are expected to rise 1.4 to 5.8 Celsius degrees (2.5 to 10.4 Fahrenheit degrees) by the year 2100. Although this trend appears to be a small change, the increase would make the Earth warmer than it has been in the last 125,000 years, possibly changing climate patterns, affecting crop production, disrupting wildlife distributions, and raising the sea level.
Air pollution can also damage the upper atmospheric region known as the stratosphere. Excessive production of chlorine-containing compounds such as chlorofluorocarbons (CFCs) (compounds formerly used in refrigerators, air conditioners, and in the manufacture of polystyrene products) has depleted the stratospheric ozone layer, creating a hole above Antarctica that lasts for several weeks each year. As a result, exposure to the Sun’s harmful rays has damaged aquatic and terrestrial wildlife and threatens human health in high-latitude regions of the northern and southern hemispheres.
B. Water Pollution
The demand for fresh water rises continuously as the world’s population grows. From 1940 to 1990 withdrawals of fresh water from rivers, lakes, reservoirs, and other sources increased fourfold. Of the water consumed in the United States in 1995, 39 percent was used for irrigation, 39 percent was used for electric power generation, and 12 percent was used for other utilities; industry and mining used 7 percent, and the rest was used for agricultural livestock and commercial purposes.
Sewage, industrial wastes, and agricultural chemicals such as fertilizers and pesticides are the main causes of water pollution. The U.S. Environmental Protection Agency (EPA) reports that about 37 percent of the country’s lakes and estuaries, and 36 percent of its rivers, are too polluted for basic uses such as fishing or swimming during all or part of the year. In developing nations, more than 95 percent of urban sewage is discharged untreated into rivers and bays, creating a major human health hazard.
Water runoff, a nonpoint source of pollution, carries fertilizing chemicals such as phosphates and nitrates from agricultural fields and yards into lakes, streams, and rivers. These combine with the phosphates and nitrates from sewage to speed the growth of algae, a type of plantlike organism. The water body may then become choked with decaying algae, which severely depletes the oxygen supply. This process, called eutrophication, can cause the death of fish and other aquatic life. Agricultural runoff may be to blame for the growth of a toxic form of algae called Pfiesteria piscicida, which was responsible for killing large amounts of fish in bodies of water from the Delaware Bay to the Gulf of Mexico in the late 1990s. Runoff also carries toxic pesticides and urban and industrial wastes into lakes and streams.
Erosion, the wearing away of topsoil by wind and rain, also contributes to water pollution. Soil and silt (a fine sediment) washed from logged hillsides, plowed fields, or construction sites, can clog waterways and kill aquatic vegetation. Even small amounts of silt can eliminate desirable fish species. For example, when logging removes the protective plant cover from hillsides, rain may wash soil and silt into streams, covering the gravel beds that trout or salmon use for spawning.
The marine fisheries supported by ocean ecosystems are an essential source of protein, particularly for people in developing countries. Yet pollution in coastal bays, estuaries, and wetlands threatens fish stocks already depleted by overfishing. In 1989, 260,000 barrels of oil spilled from the oil tanker Exxon Valdez into Alaska’s Prince William Sound, a pristine and rich fishing ground. In 1999 there were 8,539 reported spills in and around U.S. waters, involving 4.4 billion liters (1.2 billion gallons) of oil.
C. Soil Pollution
Soil is a mixture of mineral, plant, and animal materials that forms during a long process that may take thousands of years. It is necessary for most plant growth and is essential for all agricultural production. Soil pollution is a buildup of toxic chemical compounds, salts, pathogens (disease-causing organisms), or radioactive materials that can affect plant and animal life.
Unhealthy soil management methods have seriously degraded soil quality, caused soil pollution, and enhanced erosion. Treating the soil with chemical fertilizers, pesticides, and fungicides interferes with the natural processes occurring within the soil and destroys useful organisms such as bacteria, fungi, and other microorganisms. For instance, strawberry farmers in California fumigate the soil with methyl bromide to destroy organisms that may harm young strawberry plants. This process indiscriminately kills even beneficial microorganisms and leaves the soil sterile and dependent upon fertilizer to support plant growth. This results in heavy fertilizer use and increases polluted runoff into lakes and streams.
Improper irrigation practices in areas with poorly drained soil may result in salt deposits that inhibit plant growth and may lead to crop failure. In 2000 BC, the ancient Sumerian cities of the southern Tigris-Euphrates Valley in Mesopotamia depended on thriving agriculture. By 1500 BC, these cities had collapsed largely because of crop failure due to high soil salinity. The same soil pollution problem exists today in the Indus Valley in Pakistan, the Nile Valley in Egypt, and the Imperial Valley in California.
D. Solid Waste
Solid wastes are unwanted solid materials such as garbage, paper, plastics and other synthetic materials, metals, and wood. Billions of tons of solid waste are thrown out annually. The United States alone produces about 200 million metric tons of municipal solid waste each year (see Solid Waste Disposal). A typical American generates an average of 2 kg (4 lb) of solid waste each day. Cities in economically developed countries produce far more solid waste per capita than those in developing countries. Moreover, waste from developed countries typically contains a high percentage of synthetic materials that take longer to decompose than the primarily biodegradable waste materials of developing countries.
Areas where wastes are buried, called landfills, are the cheapest and most common disposal method for solid wastes worldwide. But landfills quickly become overfilled and may contaminate air, soil, and water. Incineration, or burning, of waste reduces the volume of solid waste but produces dense ashen wastes (some of which become airborne) that often contain dangerous concentrations of hazardous materials such as heavy metals and toxic compounds. Composting, using natural biological processes to speed the decomposition of organic wastes, is an effective strategy for dealing with organic garbage and produces a material that can be used as a natural fertilizer. Recycling, extracting and reusing certain waste materials, has become an important part of municipal solid waste strategies in developed countries. According to the EPA, more than one-fourth of the municipal solid waste produced in the United States is now recycled or composted. Recycling also plays a significant, informal role in solid waste management for many Asian countries, such as India, where organized waste-pickers comb streets and dumps for items such as plastics, which they use or resell.
Expanding recycling programs worldwide can help reduce solid waste pollution, but the key to solving severe solid waste problems lies in reducing the amount of waste generated. Waste prevention, or source reduction, such as altering the way products are designed or manufactured to make them easier to reuse, reduces the high costs associated with environmental pollution.
E. Hazardous Waste
Hazardous wastes are solid, liquid, or gas wastes that may be deadly or harmful to people or the environment and tend to be persistent or nondegradable in nature. Such wastes include toxic chemicals and flammable or radioactive substances, including industrial wastes from chemical plants or nuclear reactors, agricultural wastes such as pesticides and fertilizers, medical wastes, and household hazardous wastes such as toxic paints and solvents.
About 400 million metric tons of hazardous wastes are generated each year. The United States alone produces about 250 million metric tons—70 percent from the chemical industry. The use, storage, transportation, and disposal of these substances pose serious environmental and health risks. Even brief exposure to some of these materials can cause cancer, birth defects, nervous system disorders, and death. Large-scale releases of hazardous materials may cause thousands of deaths and contaminate air, water, and soil for many years. The world’s worst nuclear reactor accident took place near Chernobyl’, Ukraine, in 1986 (see Chernobyl’ Accident). The accident killed at least 31 people, forced the evacuation and relocation of more than 200,000 more, and sent a plume of radioactive material into the atmosphere that contaminated areas as far away as Norway and the United Kingdom.
Until the Minamata Bay contamination was discovered in Japan in the 1960s and 1970s, most hazardous wastes were legally dumped in solid waste landfills, buried, or dumped into lakes, rivers, and oceans. Legal regulations now restrict how such materials may be used or disposed, but such laws are difficult to enforce and often contested by industry. It is not uncommon for industrial firms in developed countries to pay poorer countries to accept shipments of solid and hazardous wastes, a practice that has become known as the waste trade. Moreover, cleaning up the careless dumping of the mid-20th century is costing billions of dollars and progressing very slowly, if at all. The United States has an estimated 217,000 hazardous waste dumps that need immediate action. Cleaning them up could take more than 30 years and cost $187 billion.
Hazardous wastes of particular concern are the radioactive wastes from the nuclear power and weapons industries. To date there is no safe method for permanent disposal of old fuel elements from nuclear reactors. Most are kept in storage facilities at the original reactor sites where they were generated. With the end of the Cold War, nuclear warheads that are decommissioned, or no longer in use, also pose storage and disposal problems.
F. Noise Pollution
Unwanted sound, or noise, such as that produced by airplanes, traffic, or industrial machinery, is considered a form of pollution. Noise pollution is at its worst in densely populated areas. It can cause hearing loss, stress, high blood pressure, sleep loss, distraction, and lost productivity.
Sounds are produced by objects that vibrate at a rate that the ear can detect. This rate is called frequency and is measured in hertz, or vibrations per second. Most humans can hear sounds between 20 and 20,000 hertz, while dogs can hear high-pitched sounds up to 50,000 hertz. While high-frequency sounds tend to be more hazardous and more annoying to hearing than low-frequency sounds, most noise pollution damage is related to the intensity of the sound, or the amount of energy it has. Measured in decibels, noise intensity can range from zero, the quietest sound the human ear can detect, to over 160 decibels. Conversation takes place at around 40 decibels, a subway train is about 80 decibels, and a rock concert is from 80 to 100 decibels. The intensity of a nearby jet taking off is about 110 decibels. The threshold for pain, tissue damage, and potential hearing loss in humans is 120 decibels. Long-lasting, high-intensity sounds are the most damaging to hearing and produce the most stress in humans.
Solutions to noise pollution include adding insulation and sound-proofing to doors, walls, and ceilings; using ear protection, particularly in industrial working areas; planting vegetation to absorb and screen out noise pollution; and zoning urban areas to maintain a separation between residential areas and zones of excessive noise.
IV. HISTORY
Much of what we know of ancient civilizations comes from the wastes they left behind. Refuse such as animal skeletons and implements from stone age cave dwellings in Europe, China, and the Middle East helps reveal hunting techniques, diet, clothing, tool usage, and the use of fire for cooking. Prehistoric refuse heaps, or middens, discovered by archaeologists in coastal areas of North America reveal information about the shellfish diet and eating habits of Native Americans who lived more than 10,000 years ago.
As humans developed new technologies, the magnitude and severity of pollution increased. Many historians speculate that the extensive use of lead plumbing for drinking water in Rome caused chronic lead poisoning in those who could afford such plumbing. The mining and smelting of ores that accompanied the transition from the Stone Age to the Metal Age resulted in piles of mining wastes that spread potentially toxic elements such as mercury, copper, lead, and nickel throughout the environment.
Evidence of pollution during the early Industrial Revolution is widespread. Samples of hair from historical figures such as Newton and Napoleon show the presence of toxic elements such as antimony and mercury. By the 1800s, certain trades were associated with characteristic occupational diseases: Chimney sweeps contracted cancer of the scrotum (the external sac of skin enclosing the testes, or reproductive glands) from hydrocarbons in chimney soot; hatters became disoriented, or “mad,” from nerve-destroying mercury salts used to treat felt fabric; and bootblacks suffered liver damage from boot polish solvents.
During the 20th century, pollution evolved from a mainly localized problem to one of global consequences in which pollutants not only persisted in the environment, but changed atmospheric and climatic conditions. The Minamata Bay disaster was the first major indication that humans would need to pay more attention to their waste products and waste disposal practices, in particular, hazardous waste disposal. In the years that followed, many more instances of neglect or carelessness resulted in dangerous levels of contamination. In 1976 an explosion at a chemical factory in Seveso, Italy, released clouds of toxic dioxin into the area, exposing hundreds of residents and killing thousands of animals that ate exposed food. In 1978 it was discovered that the Love Canal housing development in New York State was built on a former chemical waste dump. The development was declared uninhabitable. The world’s worst industrial accident occurred in Bhopal, India, in 1984. A deadly gas leaked from an American chemical plant, killing more than 3,800 people and injuring more than 200,000.
The 1986 Chernobyl’ nuclear reactor accident demonstrated the dangerous contamination effects of large, uncontained disasters. In an unprecedented action, pollution was used as a military tactic in 1991 during the conflict in the Persian Gulf. The Iraqi military intentionally released as much as 1 billion liters (336 million gallons) of crude oil into the Persian Gulf and set fire to more than 700 oil wells, sending thick, black smoke into the atmosphere over the Middle East.
V. CONTROLLING POLLUTION
Because of the many environmental tragedies of the mid-20th century, many nations instituted comprehensive regulations designed to repair the past damage of uncontrolled pollution and prevent future environmental contamination. In the United States, the Clean Air Act (1970) and its amendments significantly reduced certain types of air pollution, such as sulfur dioxide emissions. The Clean Water Act (1977) and Safe Drinking Water Act (1974) regulated pollution discharges and set water quality standards. The Toxic Substances Control Act (1976) and the Resource Conservation and Recovery Act (1976) provided for the testing and control of toxic and hazardous wastes. In 1980 Congress passed the Comprehensive Environmental Response, Compensation, and Liability Act (CERCLA), also known as Superfund, to provide funds to clean up the most severely contaminated hazardous waste sites. These and several other federal and state laws helped limit uncontrolled pollution, but progress has been slow and many severe contamination problems remain due to lack of funds for cleanup and enforcement.
International agreements have also played a role in reducing global pollution. The Montréal Protocol on Substances that Deplete the Ozone Layer (1987) set international target dates for reducing the manufacture and emissions of the chemicals, such as CFCs, known to deplete the ozone layer. The Basel Convention on the Control of Transboundary Movements of Hazardous Wastes and Their Disposal (1989) serves as a framework for the international regulation of hazardous waste transport and disposal.
Since 1992 representatives from more than 160 nations have met regularly to discuss methods to reduce greenhouse gas emissions. In 1997 the Kyōto Protocol was devised, calling for industrialized countries to reduce their gas emissions by 2012 to an average 5 percent below 1990 levels. At the end of 2000 the Kyōto Protocol had not yet been ratified; negotiators were still working to find consensus on the rules, methods, and penalties that should be used to enforce the treaty.
Regulations and legislation have led to considerable progress in cleaning up air and water pollution in developed countries. Vehicles in the 1990s emit fewer nitrogen oxides than those in the 1970s did; power plants now burn low-sulfur fuels; industrial stacks have scrubbers to reduce emissions; and lead has been removed from gasoline. Developing countries, however, continue to struggle with pollution control because they lack clean technologies and desperately need to improve economic strength, often at the cost of environmental quality. The problem is compounded by developing countries attracting foreign investment and industry by offering cheaper labor, cheaper raw materials, and fewer environmental restrictions. The maquiladoras, assembly plants along the Mexican side of the Mexico-U.S. border, provide jobs and industry for Mexico but are generally owned by non-Mexican corporations attracted to the cheap labor and lack of pollution regulation. As a result, this border region, including the Río Grande, is one of the most heavily polluted zones in North America. To avoid ecological disaster and increased poverty, developing countries will require aid and technology from outside nations and corporations, community participation in development initiatives, and strong environmental regulations.
Nongovernmental citizen groups have formed at the local, national, and international level to combat pollution problems worldwide. Many of these organizations provide information and support for people or organizations traditionally not involved in the decision-making process. The Pesticide Action Network provides technical information about the effects of pesticides on farmworkers. The Citizen’s Clearinghouse for Hazardous Waste, established by veterans of the Love Canal controversy, provides support for communities targeted for hazardous waste installations. A well-organized, grassroots, environmental justice movement has arisen to advocate equitable environmental protections. Greenpeace is an activist organization that focuses international attention on industries and governments known to contaminate land, sea, or atmosphere with toxic or solid wastes. Friends of the Earth International is a federation of international organizations that fight environmental pollution around the world.

Contributed By:
Paul Engelking
Microsoft ® Encarta ® 2006. © 1993-2005 Microsoft Corporation. All rights reserved.















Conservation
I INTRODUCTION
Conservation, sustainable use and protection of natural resources including plants, animals, mineral deposits, soils, clean water, clean air, and fossil fuels such as coal, petroleum, and natural gas. Natural resources are grouped into two categories, renewable and nonrenewable. A renewable resource is one that may be replaced over time by natural processes, such as fish populations or natural vegetation, or is inexhaustible, such as solar energy. The goal of renewable resource conservation is to ensure that such resources are not consumed faster than they are replaced. Nonrenewable resources are those in limited supply that cannot be replaced or can be replaced only over extremely long periods of time. Nonrenewable resources include fossil fuels and mineral deposits, such as iron ore and gold ore. Conservation activities for nonrenewable resources focus on maintaining an adequate supply of these resources well into the future.
Natural resources are conserved for their biological, economic, and recreational values, as well as their natural beauty and importance to local cultures. For example, tropical rain forests are protected for their important role in both global ecology and the economic livelihood of the local culture; a coral reef may be protected for its recreational value for scuba divers; and a scenic river may be protected for its natural beauty.
Conservation conflicts arise when natural-resource shortages develop in the face of steadily increasing demands from a growing human population. Controversy frequently surrounds how a resource should be used, or allocated, and for whom. For example, a river may supply water for agricultural irrigation, habitat for fish, and water-generated electricity for a factory. Farmers, fishers, and industry leaders vie for unrestricted access to this river, but such freedom could destroy the resource, and conservation methods are necessary to protect the river for future use.
Conflicts worsen when a natural resource crosses political boundaries. For example, the headwaters, or source, of a major river may be located in a different country than the country through which the river flows. There is no guarantee that the river source will be protected to accommodate resource needs downstream. In addition, the way in which one natural resource is managed has a direct effect upon other natural resources. Cutting down a forest near a river, for instance, increases erosion, the wearing away of topsoil, and can lead to flooding. Eroded soil and silt cloud the river and adversely affect many organisms such as fish and important aquatic plants that require clean, clear freshwater for survival.
II METHODS OF CONSERVATION
The challenge of conservation is to understand the complex connections among natural resources and balance resource use with protection to ensure an adequate supply for future generations. In order to accomplish this goal, a variety of conservation methods are used. These include reducing consumption of resources; protecting them from contamination or pollution; reusing or recycling resources when possible; and fully protecting, or preserving, resources.
Consumption of natural resources rises dramatically every year as the human population increases and standards of living rise. Between 1950 and 1990 the world population doubled to 5.3 billion, with nearly 80 percent living in developing, or poorer, nations. The large, developed nations, however, are responsible for the greatest consumption of natural resources because of their high standards of living. For instance, in 1992 the average American consumed as much energy as 27 Filipinos or 370 Ethiopians. Conservation education and the thoughtful use of resources is necessary in the developed countries to reduce natural-resource consumption. For example, reducing the high demand for tropical hardwoods such as teak and mahogany in the United States and Japan would slow the rate of tropical forest destruction.
To protect natural resources from pollution, individuals, industries, and governments have many obligations. These include prohibiting or limiting the use of pesticides and other toxic chemicals, limiting wastewater and airborne pollutants, preventing the production of radioactive materials, and regulating drilling and transportation of petroleum products. Failure to do so results in contaminated air, soil, rivers, plants, and animals. For example, if governments required that all oil tankers be fitted with double-layered hulls, the damages to fisheries and wildlife from the many oil spills of the 20th century, such as the 1967 Torrey Canyon oil spill in the English Channel, may have been reduced.
In many cases it is possible to reuse or recycle resources to reduce waste and resource consumption and conserve the energy needed to produce consumer products. For example, paper, glass, freon (a refrigerant gas), aluminum, metal scrap, and motor oil can all be recycled. A preventative measure called precycling, a general term for designing more durable, recyclable products such as reusable packaging, encourages reuse. Many states in the United States have established mandatory recycling laws in an attempt to reduce waste and consumption.
Some resources are so unique or valuable that they are protected from activities that would destroy or degrade them. For example, national parks and wilderness areas are protected from logging or mining in the United States because such activities would reduce the economic, recreational, and aesthetic values of the resource. Forests and wetlands (areas with high soil moisture or surface water) may be protected from development because they enhance air and water quality and provide habitat for a wide variety of plants and animals. Unfortunately, these areas are often threatened with development because it is difficult to measure the economic benefits of cleaner air, cleaner water, and the many other environmental benefits of these ecosystems (the plants and animals of a natural community and their physical environment).
III CURRENT TYPES OF CONSERVATION ISSUES
There are a variety of basic conservation methods used to protect global natural resources. Although each resource has a unique set of conservation problems and solutions, all resources are interconnected in a complex and little-understood web. Scientists have learned that damaging one thread of the web may weaken the entire structure. It is important that this connectivity be addressed in the search for solutions to resource shortages. It would be impractical to work toward the conservation of soil, for instance, without considering the needs and effects of nearby water and vegetation resources (see Environment).
A Biodiversity Conservation
Biodiversity, or biological diversity, denotes the number and variety of different organisms and ecosystems in a certain area. Preserving biodiversity is essential for ecosystems to respond flexibly to damage or change. For example, a single-species corn crop may be quickly destroyed by a certain insect or disease, but if several different species of corn are planted in the field, some of them may resist the insect or disease and survive. The same principle applies to natural areas, which adapt to natural environmental changes such as wildfire, drought, or disease because of the biodiversity that has evolved in the area over thousands, or even millions, of years. For example, many forests, such as those that burned in the 1988 fires in Yellowstone National Park in Wyoming, are able to quickly regenerate because many of the plants that thrive there have adapted to fire. Some trees, such as lodgepole pine, may even require fire to aid in reproduction. These trees produce cones that are opened by extreme heat. The fire opens the cones and the seeds are then released into the soil.
Humans benefit greatly from the many medicines, crops, and other products that biodiversity provides. As many as 40 percent of our modern pharmaceutical medicines are derived from plants or animals. For instance, a small plant from Madagascar, the rosy periwinkle, produces substances that are effective in fighting two deadly cancers, Hodgkin’s disease and leukemia.
Unfortunately, human activities have greatly reduced biodiversity around the world. The 20th century encompasses one of the greatest waves of extinction, or elimination of species, to occur on the planet. The greatest threat to biodiversity is loss of habitat as humans develop land for agriculture, grazing livestock, industry, and habitation. The most drastic damage has occurred in the tropical rain forests, which cover less than seven percent of the Earth’s surface but contain well over half of the planet’s biodiversity. Only 8 percent of the rain forests in Madagascar, home of the rosy periwinkle, remain intact.
Several nations have laws protecting endangered species. An international treaty, the Convention on International Trade in Endangered Species of Wild Fauna and Flora (CITES), went into effect in 1975 and outlawed trade of endangered animals and animal parts. In the United States, the Endangered Species Act (ESA) was enacted in 1973 to protect endangered or threatened species and their habitats. A new scientific field, conservation biology, studies ways to stop the destruction of biodiversity and restore natural habitats.
B Forest Conservation
Forests provide many social, economic, and environmental benefits. In addition to timber and paper products, forests provide wildlife habitat and recreational opportunities, prevent soil erosion and flooding, help provide clean air and water, and contain tremendous biodiversity. Forests are also an important defense against global climate change. Through the process of photosynthesis, forests produce life-giving oxygen and consume huge amounts of carbon dioxide, the atmospheric chemical most responsible for global warming. By decreasing the amount of carbon dioxide in the atmosphere, forests may reduce the effects of global warming.
However, huge areas of the richest forests in the world have been cleared for wood fuel, timber products, agriculture, and livestock. These forests are rapidly disappearing. The tropical rain forests of the Brazilian Amazon River basin were cut down at an estimated rate of 14 million hectares (35 million acres) each year—an area about the size of the state of Wisconsin—in the 1990s. The countries with the most tropical forests tend to be developing and overpopulated nations in the southern hemisphere. Due to poor economies, people resort to clearing the forest and planting crops in order to survive. While there have been effective efforts to stop deforestation directly through boycotts of multinational corporations responsible for exploitative logging, the most effective conservation policies in these countries have been efforts to relieve poverty and expand access to education and health care.
In the United States and Canada, forests are threatened by extensive logging, called clear-cutting, which destroys plant and animal habitat and leaves the landscape bare and unproductive if not properly reforested. Small pockets of ancient forests from 200 to 1,200 years old still exist but are threatened by logging interests. Until the 1990s, the U.S. Forest Service was directed by Congress to maximize the harvest of timber in order to provide jobs. In the late 1980s and early 1990s, however, environmentalists sued the government for violating the National Environmental Policy Act (NEPA), and heavy logging was deemed nonsustainable. As a result, the timber harvest was reduced and foresters were directed to follow a more sustainable policy called ecosystem management. This policy required foresters to focus on conserving natural habitats rather than maximizing tree harvest. Despite this change, many ancient forests remain unprotected.
C Soil Conservation
Soil, a mixture of mineral, plant, and animal materials, is essential for most plant growth and is the basic resource for agricultural production. Soil-forming processes may take thousands of years, and are slowed by natural erosion forces such as wind and rain. Humans have accelerated these erosion processes by developing the land and clearing away the vegetation that holds water and soil in place. The rapid deforestation taking place in the tropics is especially damaging because the thin layer of soil that remains is fragile and quickly washes away when exposed to the heavy tropical rains (see Desertification). Globally, agriculture accounts for 28 percent of the nearly 2 billion hectares (5 billion acres) of soil that have been degraded by human activities; overgrazing is responsible for 34 percent; and deforestation is responsible for 29 percent.
In addition to reducing deforestation and overgrazing, soil conservation involves reforming agricultural soil management methods. Some of the most effective methods include strip-cropping, alternating strips of crop and uncultivated land to minimize erosion and water runoff; contour farming, planting crops along the contours of sloping lands to minimize erosion and runoff; terracing, which also reduces erosion and runoff on slopes; growing legumes, such as clover or soybeans, to restore essential nitrogen in the soil (see Nitrogen Fixation); and minimizing tillage, or plowing, to reduce erosion.
D Water Conservation
Clean freshwater resources are essential for drinking, bathing, cooking, irrigation, industry, and for plant and animal survival. Unfortunately, the global supply of freshwater is distributed unevenly. Chronic water shortages exist in most of Africa and drought is common over much of the globe. The sources of most freshwater supplies—groundwater (water located below the soil surface), reservoirs, and rivers—are under severe and increasing environmental stress because of overuse, water pollution, and ecosystem degradation. Over 95 percent of urban sewage in developing countries is discharged untreated into surface waters such as rivers and harbors.
About 65 percent of the global freshwater supply is used in agriculture and 25 percent is used in industry. Freshwater conservation therefore requires a reduction in wasteful practices like inefficient irrigation, reforms in agriculture and industry, and strict pollution controls worldwide.
In addition, water supplies can be increased through effective management of watersheds (areas that drain into one shared waterway). By restoring natural vegetation to forests or fields, communities can increase the storage and filtering capacity of these watersheds and minimize wasteful flooding and erosion. Restoration and protection of wetlands is crucial to water conservation. Like giant sponges, wetlands stabilize groundwater supplies by holding rainfall and discharging the water slowly, acting as natural flood-control reservoirs.
E Energy Conservation
All human cultures require the production and use of energy—that is, resources with the capacity to produce work or power. Energy is used for transportation, heating, cooling, cooking, lighting, and industrial production. The world energy supply depends on many different resources including traditional fuels such as firewood and animal waste, which are significant energy sources in many developing countries. Fossil fuels account for more than 90 percent of global energy production but are considered problematic resources. They are nonrenewable—that is, they can be depleted, and their use causes air pollution. In particular, coal plants have been one of the worst industrial polluters since the beginning of the Industrial Revolution of the 19th century. Moreover, mining or drilling for fossil fuels has caused extensive environmental damage.
There is a global need to increase energy conservation and the use of renewable energy resources. Renewable alternatives such as waterpower (using the energy of moving water, such as rivers), solar energy (using the energy from the sun), wind energy (using the energy of the wind or air currents), and geothermal energy (using energy contained in hot-water deposits within the Earth’s crust) are efficient and practical but largely underutilized because of the ready availability of inexpensive, nonrenewable fossil fuels in industrial countries.
While some countries, such as France and Japan, depend heavily on nuclear energy (energy produced by atomic fission, or splitting of the atom), it is still not a major energy source. Excessive production costs, serious safety concerns, and problems with the handling of the dangerous radioactive wastes have virtually eliminated it as a viable energy source in the United States.
In addition to using alternative energy resources such as solar and wind power, energy conservation measures include improving energy efficiency. For instance, transportation accounts for most of the oil consumption in the United States. Encouraging the expansion and use of public transportation systems and carpooling dramatically increases energy efficiency. In the household, energy can be conserved by turning down thermostats, switching off unnecessary lights, insulating homes, and using less hot water.
IV HISTORY OF CONSERVATION
Until the advent and spread of Christianity and Islam in the 4th and 5th centuries, there were many religions based on animism, the belief that all objects have a spiritual being. This belief led to careful stewardship, or protection, of natural resources out of fear or respect for these spiritual beings. Moreover, early agricultural lifestyles, dependent on nature to provide good crops and growing conditions, also encouraged sound land-use practices. Ancient Phoenicians, Greeks, and Romans developed irrigation, crop rotation, and terraced hillsides as early methods of water, nutrient, and soil conservation.
In Europe, the relationship between humanity and nature became strained with the beginning of the Industrial Revolution in the 19th and early 20th centuries. Industrialization stifled traditional agricultural lifestyles and encouraged urbanization and the marriage of science and technology to control nature and extract resources. The Industrial Revolution led to environmental damage on a grand scale as European technology spread around the globe. Coal-burning and iron-smelting produced waste that contaminated air and water, the concentrated populations in urban areas produced huge amounts of unconfined raw sewage that contaminated drinking water, and vast forests and plains were cleared for agriculture.
The modern conservation movement of the United States began in the mid-19th century when resource depletion and pollution were first becoming serious problems. Westward expansion was encouraged by the government—the Homestead Act of 1862 provided free land to settlers willing to clear it. Because land ownership required land-clearing, the rapid migration often resulted in barren landscapes. The extensive land-clearing and the rapid depletion of wildlife resources such as buffalo and beaver heralded a public outcry. This concern was reflected in the writings of public figures such as American essayist Ralph Waldo Emerson and naturalist author Henry David Thoreau.
As conservation ideas gained support, a wave of conservation activity swept the country. The world’s first national park, Yellowstone National Park, was established in Wyoming in 1872 to protect an area of incredible natural beauty. In 1873, the American Association for the Advancement of Science petitioned Congress to halt unwise use of natural resources, the Forest Reserve Act of 1891 authorized what would become known as National Forests, and the Lacey Act of 1900 established the first wildlife protection measures by restricting commercial hunting and the trade of illegally killed animals.
The administration of President Theodore Roosevelt (1901-1909) was noted for its conservation achievements. Roosevelt set aside a total of almost 94 million hectares (235 million acres) of public lands to protect them from exploitation by private interests. He installed forestry expert Gifford Pinchot as the head of the new U.S. Forest Service in 1905 and adopted Pinchot’s principle of multiple use, the nation’s first formal natural-resource policy. The multiple-use policy advocated scientific management of public lands for a variety of uses, including commercial development.
This conservation policy was not popular among many Americans who backed full preservation of natural areas. Naturalist and author John Muir believed that any commercial development of natural areas was inappropriate. A powerful rift soon developed between multiple-use advocates and preservationists. This rift came to a climax during the 12-year battle over a plan to dam the Tuolumne River in Hetch Hetchy Valley in California, and the controversy still exists today.
A renewed surge of public conservation activity occurred during the Great Depression of the 1930s. In an attempt to encourage conservation and stimulate the economy, President Franklin D. Roosevelt established the Civilian Conservation Corp in 1933, which provided two million jobs planting trees, building dams and irrigation systems, and establishing soil conservation and wildlife protection programs.
The conservation movement rose into the spotlight again in the 1960s as publications such as Silent Spring (1962) by American biologist Rachel Carson raised public concerns about the health and environmental hazards of pesticides and other toxic chemicals used by industry. Several catastrophic events in 1969, including the toxic waste fires on the Cuyahoga River in Cleveland, Ohio and a coastal oil spill in Santa Barbara, California focused media attention on the need for environmental conservation. The estimated 20 million people across the United States who attended the first national Earth Day, a day for recognizing environmental concerns, on April 22, 1970, demonstrated massive public support for conservation issues. Conservation legislation passed in the 1970s included the Endangered Species Act, the Marine Mammal Protection Act, the Clean Air Act, the Clean Water Act, and the Toxic Substance Control Act.
The 1980s experienced a slowdown of the conservation momentum of the 1970s. Resource conservation concerns remained in the public mind, however, due to continued scientific discoveries concerning global warming, acid rain (a harmful mix of precipitation and damaging pollutants), and depletion of the ozone layer (a gaseous layer in the atmosphere that protects Earth from the sun’s harmful ultraviolet rays). Ecological disasters such as the nuclear reactor explosion near the Ukrainian town of Chernobyl’ in 1986 (see Chernobyl’ Accident) and the tanker Exxon Valdez oil spill in Prince William Sound, Alaska in 1989, served as catastrophic reminders of the effects of human carelessness.
The European conservation movement began to grow as the effects of industrialization worsened in the mid-20th century. Clean air legislation was enacted in the United Kingdom in 1956 in reaction to London’s industrial smog, which killed more than 2,000 people in early December 1952. Political parties with environmental or conservation agendas sprang up in New Zealand, Australia, and Europe by the 1970s, and became known as Green Parties in the 1980s. In the 70s and 80s, courageous grassroots organizations such as the Chipko movement in India (a coalition of villagers, mostly women) and the Brazilian rubber tappers (workers who extract chicle, the tree sap used to make rubber) fought for preservation of the forests that provided their livelihood.
In 1972 the United Nations Environment Program was formed to encourage international cooperation in conservation and development strategies. Collaboration on environmental conservation issues included the 1987 Montreal Protocol to protect the ozone layer, the 1992 United Nations Conference on Environment and Development (UNCED) in Rio de Janeiro, Brazil, and the 1994 United Nations Conference on Population and Development in Cairo, Egypt. The United States’ participation in this international movement was weak, while Canadian and European support and participation was strong.
The 1992 UNCED Conference, commonly referred to as the Earth Summit, was the largest international meeting ever held with 178 nations participating. Its proceedings noted the economic and environmental gulf between the northern and southern hemispheres and emphasized a sustainable growth, utilitarian approach to conservation. In the same year an appeal entitled World Scientists’ Warning to Humanity was released. This paper was signed by 1,700 of the world’s leading scientists (including 104 Nobel laureate scientists), 19 national academies of science, and the director general of the United Nations Educational, Scientific, and Cultural Organization (UNESCO). It stated that at the current rate of consumption, the Earth’s resources may soon be reduced to the point at which the living world would be “unable to sustain life in the manner that we know.” In several publications, ecologists and economists agree that despite the immediate benefits of economic growth, infinite growth in material and energy consumption is not compatible with the finite resources of the Earth and will undermine the well-being of both economic and ecological systems. For these reasons, natural resource conservation has become one of the most important challenges to face the human race.

Contributed By:
John H. Baldwin
Microsoft ® Encarta ® 2006. © 1993-2005 Microsoft Corporation. All rights reserved.

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Mineral cycles (Biogeochemical cycles)

Look at the above Figure before examining some individual cycle!!!
Most nutrients accumulate in 4 reservoirs, each of which is defined by two characteristics:
- Whether the nutrients contain organics or inorganics
- Whether or not the nutrients are directly available for use by organisms
The first compartment of organic materials is composed of living organisms themselves and detritus (readily available nutrients)
The second one is fossilized deposit of once living organisms (coal, oil, peat that cannot be assimilated directly)
Nutrients also occur in two inorganic compartments (one are available for use and the other are not)


Introduction
– As discussed previously that most of the chemical energy disappear/lost at each trophic level
– However, the energy stored as biomass at each trophic level is not lost
– This biomass actually consists of elements that will undergo cycles in the ecosystem
– Life on earth therefore depend on recycling of essential chemical elements
– This cycle also occurs even while an individual organism alive.
– Example: nutrients are absorbed and the wastes are released, after the nutrients are processed in their body
– All materials including living organisms are composed by the smallest unit of elements called atom
– Especially for living organisms, when they die, all of these element will return as simpler compound to atmosphere, water, or soil through the action of decomposers
– The products of decomposition (inorganic nutrients) can be used by plants or other autotroph to build new organic matters.
– Because this nutrient cycles involves complex biotic and abiotic components in the ecosystem, they then are called Biogeochemical cycles
– Look at the above Figure before examining some individual cycle!!!
Most nutrients accumulate in 4 reservoirs, each of which is defined by two characteristics:
Whether the nutrients contain organics or inorganics
Whether or not the nutrients are directly available for use by organisms
The first compartment of organic materials is composed of living organisms themselves and detritus (readily available nutrients)
The second one is fossilized deposit of once living organisms (coal, oil, peat that cannot be assimilated directly)
Nutrients also occur in two inorganic compartments (one are available for use and the other are not)
In this lesson we will study the water cycle and three important element cycles (Carbon, Nitrogen, and phosphorous cycles)
Bear in mind that chemical cycle in the ecosystem depends on both biological and geological processes

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Movement system in human

This movement system involves two component of body systems:
- Skeletal system
- Muscular system
These two system will be discussed briefly before you are asked to identify those two system in detail
The mechanism of how these two systems generate movement in human body will also be discussed


Skeletal system

The objective of this chapter:
– The students should be able to:
List the 5 functions of the skeletal system
Label a diagram of a long bone and describe the microscopic structure of a bone
Describe the division of the skeletal system
List and describe the bones of axial skeleton and identify each on a diagram or skeleton
List and describe the bones of appendicular skeleton and identify each on a diagram or skeleton
Compare the main types of joints, and describe the structure and functions of a diarthrosis

Functions of the skeletal system

It support the body by serving as a bony framework for the other tissues and organs
It protect delicate vital organs, for examples:
– The skull surround and protect the brain
– The ribs protect the lung and heart
Bones serve as levers that transmit muscular forces
– Muscles are attached to bones by bands of connective tissue called tendons
– When muscles contract, they pull on bones, and in this way they move parts of the body
– Bones are held together at joints by bands of connective tissue called ligaments.
– In this case, Most joints are moveable
The marrow within the bones produces blood cells
Bones serve as bank for the storage and release of minerals, such as calcium and phosphorous

Long bones

The main shaft of the long bones is known as its diaphysis (Fig 4.1)
The expanded end is called epiphysis
The metaphysis (a disc of cartilage located between diaphysis and epiphysis) is found in children
The metaphysis disappear at maturity, becoming a vague epiphyseal lines
Within the long bones is a central marrow cavity which is lined by thin layer of cell (endosteum)
This is filled with fatty connective tissue called the yellow bone marrow


Two types of bone tissue

The compact and the spongy bones
– Compact bones
Note
- The structure is very dense and
hard
-characterized by harvesian sys-
tem (see fig)

– Spongy bone:
Found within the epiphysis
Makes up the inner part of the wall of the diaphysis
Consists of a network of thin strands of bone
The space within the spongy bone is filled with bone marrow:
– Red marrow (found in certain bones): produces blood cells
– Yellow marrow: consists mainly of fat cells



The skeleton division

Axial skeleton consists of:
– The skull
– Vertebral column
– Ribs
– Sternum
Appendicular skeleton consist of:
– Upper and lower limbs (Arms and Legs)
– Shoulder girdle
– Pelvic girdle (except the sacrum)

The skull (the bony framework of the head

This is divided into:
– Cranial bones (consists of 8 cranial bones that enclose the brain)
– Facial bones (consists of 14 bones) Fig. 4.5 – 4.8
Most of the bones of the skull are joined by immoveable joint called sutures:
– The sagittal suture is the joint between the two parietal bones
– The coronal suture joins the parietal bones to the frontal bone
– The lambdoidal suture is the joint between the parietal bones and the Occipital bone


The vertebral column


Support the body and bear its weight
Consists of 24 vertebrae and 2 fused bones (the sacrum and coccyx (Fig 4.9)
The region of vertebral column are:
– The neck (cervical) composed of 7 vertebrae
– Chest (Thoracic) consists of 12 vertebrae
– Back (Lumbar) consists of 5 vertebrae
– Pelvic (Sacral) consist of 5 fused vertebrae
– Coccygeal also consists of fused vertebrae
Certain structural feature of vertebrae is shown in

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The Fungi

Fungi are eukaryotic organisms
Almost all are multicellular organism
They used to be grouped with plant in the two kingdom system
They do not have chlorophyll (heterotrophic)
They are unique organisms that differ from other eukaryotes in term of:
- Nutritional modes
- Structural organization
- Growth and reproduction
Their multicellularity differ fro animal and plant in that partition between nucleated compartment or cell are either absent or partial
In other words, the cytoplasm is continuous
Consequently, each compartment has more than one nucleus
Therefore, for many fungi, the term of multinucleate description is more accurate that multicellular


Nutrition and habitat

All fungi are heterotrophs (lack of chlorophyll)
The aquire their nutrients by absorption (small nutrients are absorbed from the surrounding)
Fungi digest their food outside their body by secreting hydrolytic enzymes into the foods
Based on their absorptive mode fungi can be classified as:
– Saprobic fungi
Absorb nutrients from non living organic materials
Examples of foods: fallen log, waste of live organisms, and animal corpses
– Parasitic fungi
Absorb nutrients from living hosts
Some are pathogenic fungi in human (infect lung)
– Mutualistic fungi
They absorb nutrients from living organisms, but they also give some benefit to their hosts
Example: Mycorhiza
Their habitat is very wide
– Mostly occupy terrestrial environment
– Some of them are associated symbiotically with many organism (such as Lichen: association of fungi and algae)

Structure

Except in yeast, the body of fungi is constructed by a basic building unit called hyphae (singular, hypha)
These hyphae form an interwoven mat called mycelium (the ‘feeding’ network of a fungus)
Most fungal hypha is divided into cells by crosswall called septa (singular septum)
The septa generally have pores large enough to allow ribosome, mitochondria, or nuclei to travel from cell to cell
Their cell wall mainly composed of chitin
Some fungal hyphae are aseptate (their cells are not divided into cells by cross walls)
This type of hyphae are called coenocitic
Some parasitic fungi have their hyphae modified as haustoria
Haustoria is nutrient-absorbing hyphal tips that penetrate the tissue of the host

Growth and reproduction

Fungi reproduce by releasing spores that are produced either sexually or asexually
Their spore come in all shape and size
In the favorable conditions, fungi will produce enormous number of spore asexually
These will be carried by wind or water and germinate when landing on a moist surface
Sexual spores will be produced when there is some change in the environment
– This mode will produce greater genetic diversity among the offsprings (for adaptation in such an environmental condition)
Syngamy (sexual union of cells from two individuals)
This occurs in two stages:
– Plasmogamy
The fusion of cytoplasm
After plasmogamy, the nuclei from each parent pair up but not fuse forming a dikaryon (two nuclei)
– Karyogamy
The fusion of nuclei
Examples of spores produced by sexual mode:
– Ascospores (produced by group of Ascomycota)
Stored in ascus, normally contain 8 spores
– Basidiopores (produced by group of Basidiomycota)
Located in the basidium, normally contain 4 spores

Division of fungi

More than 100,000 species of fungi have been known until recently (thousand is reported yearly)
In this chapter these have been divided into 3 major division based on:
– Structure involved in the plasmogamy
– The time spent as a dikaryon
– The location of caryogamy
The three division are name after the sexual cells in which karyogamy occurs

Division zygomycota

About 600 species have been described
Mostly terrestrial fungi
Live in soils, decaying plants, and animal materials
Some form mycorrhizae (Mutualistic association with plant roots)
Example of this kind of fungi:
– Rhizopus stolonifer
– Pilobolus (decompose animal dung)
The life cycle of Rhizopus

Division Ascomycota

More than 600,000 species have been described
Also called sac fungi
They range in size and complexity
They include some of the most devastating plant pathogens
Many are important saprobes, particularly of plant materials
About a half form symbiotic association with algae (lichen)
Some form mycorrhiza
The defining feature is the production of sexual spore in sac-like asci (singular ascus)
They bear their sexual spores in microscopic fruiting bodies called ascocarp
Their spores are not located in the sporangia (Naked spores or also called conidia)
Examples:
Hypoxylon multiforme
Morchella esculenta (Fig. 28.4c)
Saccharomyces cerevisiae
Neurospora sp.
Penicillium sp.
Trichoderma sp.

Division Basidiomycota

App. 25,000 species have been described
Includes mushroom, shelve fungi, rust fungi, and puffball fungi (Fig. 28.6)
The name derived from basidium
The club shaped of the basidium give rise to common name club fungus
The mycelium can grow into fruiting body called basidiocarp (in certain conditions)
A mushroom is an example of a basidiocarp


(a) Hygrophorous (Mycorrhizal with oak)
(b) Shelve fungi
(c) Puffball fungi (Lycoperdon gemmatum)

Examples of Basidiomycota
– Volvariela volvacea
– Auricularia polytricha
– Pleurotus sp. (edible fungus)
– Amanita phalloides (Poisonous)
– Exobasidium vexans (parasite in tea tree)
– Corticium salmonella (parasite in the tree trunk, especially fruit producer)

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