Legend;

ADH – Antidiuretic Hormone FSH – Follicle

Stimulating Hormone
TSH – Thyroid Stimulating Hormone

Diagram showing diff locations glands

Function of Insulin
- Insulin reduces the blood glucose level when it’s high (regulates the amount of glucose
level in the blood) by stimulating the liver cells to take up glucose from the blood &
convert it to glycogen & stored.

Function of glucagon
- It raises the blood glucose level when it’s low by stimulating the liver cells to convert the
stored glycogen to glucose.

Functions of adrenaline
This is commonly known as Flight or Fight hormone because it prepares the body for action. It
has the following affects;
- It increases the rate & depth of breathing.
- It increases the rate of heart beat
- Constricts the blood vessels carrying the blood to the gut & skin hence diverting more
blood to the muscles
- It also promotes the conversion of the stored glycogen to glucose.

The above mentioned effects help to provide more glucose & more oxygen to the working
muscles.

Function of testosterone
- It controls the production & development of sperms
- Regulates the development of the male secondary sexual characteristics e.g. enlargement
of sex organs, growth of facial hair (beard), muscle enlargement, deepening of the voice
etc.

Functions of Oestrogen
- It is responsible for the development of secondary sexual characteristics in females, e.g.
armpit & pubic hair, development of breasts, broadening of hips, enlargement of vagina
etc.
- It prepares the uterus for implantation by making its lining thicker & rich in blood vessels
Comparison between the Nervous & the Endocrine Systems

NERVOUS SYSTEM ENDOCRINE SYSTEM

Information passes as electrical impulses Information passes as a chemical
substances (hormone)
Transmission is through the nerves Transmission is through the blood

Rapid Transmission & immediate Slow transmission & usually slow response
responses e.g. blinking of the eye e.g. growth
The response is short lived The response is long lasting

The response is exact since impulses are The response is usually widespread
sent directly to target organs because hormones are dispersed throughout
the body

NEGATIVE FEEDBACK
The Incoming message triggers the release of another message, which brings a negative change
(of opposite effect).
Example;
- When the blood sugar level is high, the pancreas is stimulated to produce insulin which in
term stimulates the liver cells to convert excess glucose to glycogen and reduce the blood
sugar level.
- The Follicle stimulating hormone (FSH) secreted by the pituitary gland stimulates the
ovaries to produce Oestrogen, but the moment the Oestrogen level increases the
production of FSH stops, which in turn will lead to a decrease in Oestrogen level.

HORMONAL CORDINATION
A hormone is a chemical substance produced by a gland carried in the blood, which alters the
activity of one or more specific target organs.

THE DIFFERENCE BETWEEN EXOCRINE & ENDOCRINE GLANDS

The exocrine glands are those glands which have ducts, i.e. their secretions are passed through
ducts onto the epithelial surface e.g. tear gland, salivary gland etc. The endocrine glands are
ductless (do not have ducts) and their secretions are carried by the blood.

EXAMPLES OF ENDOCRINE GLANDS & THE HORMONES THEY PRODUCE

GLAND HORMONE
Thyroid Thyroxin
Adrenal Adrenaline
Pituitary ADH, FSH, TSH
Pancreas Insulin, glucagon
Testis Testosterone
Ovaries Oestrogen,
Progesterone
 Legend;
ADH – Antidiuretic Hormone FSH – Follicle
Stimulating Hormone
TSH – Thyroid Stimulating Hormone

Diagram showing diff locations glands

Function of Insulin
- Insulin reduces the blood glucose level when it’s high (regulates the amount of glucose
level in the blood) by stimulating the liver cells to take up glucose from the blood &
convert it to glycogen & stored.

Function of glucagon
- It raises the blood glucose level when it’s low by stimulating the liver cells to convert the
stored glycogen to glucose.

Functions of adrenaline
This is commonly known as Flight or Fight hormone because it prepares the body for action. It
has the following affects;
- It increases the rate & depth of breathing.
- It increases the rate of heart beat
- Constricts the blood vessels carrying the blood to the gut & skin hence diverting more
blood to the muscles
- It also promotes the conversion of the stored glycogen to glucose.

The above mentioned effects help to provide more glucose & more oxygen to the working
muscles.

Function of testosterone
- It controls the production & development of sperms
- Regulates the development of the male secondary sexual characteristics e.g. enlargement
of sex organs, growth of facial hair (beard), muscle enlargement, deepening of the voice
etc.

Functions of Oestrogen
- It is responsible for the development of secondary sexual characteristics in females, e.g.
armpit & pubic hair, development of breasts, broadening of hips, enlargement of vagina
etc.
- It prepares the uterus for implantation by making its lining thicker & rich in blood vessels
Comparison between the Nervous & the Endocrine Systems

NERVOUS SYSTEM ENDOCRINE SYSTEM

Information passes as electrical impulses Information passes as a chemical
substances (hormone)
Transmission is through the nerves Transmission is through the blood

Rapid Transmission & immediate Slow transmission & usually slow response
responses e.g. blinking of the eye e.g. growth
The response is short lived The response is long lasting

The response is exact since impulses are The response is usually widespread
sent directly to target organs because hormones are dispersed throughout
the body

NEGATIVE FEEDBACK
The Incoming message triggers the release of another message, which brings a negative change
(of opposite effect).
Example;
- When the blood sugar level is high, the pancreas is stimulated to produce insulin which in
term stimulates the liver cells to convert excess glucose to glycogen and reduce the blood
sugar level.
- The Follicle stimulating hormone (FSH) secreted by the pituitary gland stimulates the
ovaries to produce Oestrogen, but the moment the Oestrogen level increases the
production of FSH stops, which in turn will lead to a decrease in Oestrogen level.

THE USE AND ABUSE OF DRUGS

 ECOLOGY

- Study of living things in relation to their natural environment.

- Where organisms live and the size of their populations are affected by interactions with
other organisms and with the non living parts of their environment.

ECOLOGICAL TERMS

The following are some of the mostly used ecological terms.

1. Biosphere – the zones of the air, land and water at the surface of the earth occupied by living
things.

2. Ecosystem – a stable, settled unit of nature consisting of a community of organisms,

interacting with each other and with their surrounding’s physical and chemical environment.
Examples of ecosystems are;

- Ponds
- Lakes
- Woods
- Forests
- Sea shores
- Salt marshes
- Grassland
- Savanna etc

Ecosystems may be very variable in size.

3. Population – a group of individuals of the same species occupying a given area at the same
time.

4. Community – populations of organisms inhabiting a common environment and interacting

with one another.

5. Habitat – the place in which individuals of a particular species can usually be found.

6. Species – a group of organisms that actually interbreed in nature and are reproductively
isolated from all other such groups.

7. Niche – the way in which an organism interacts with all of the biotic and abiotic factors in its
environment.

8. Biotic factors – the living components of an ecosystem.

9. Abiotic factors – nonliving components of an ecosystem.

10. Competition – interaction between members of the same population or of two or more
populations using the same resource, often present in limited supply.

11. Intraspecific competition – competition between individuals of the same species.

12. Interspecific competition – competition between individuals of different species.

13. Environment – the surrounding of an individual.

ENERGY FLOW

- The ultimate source of energy in an ecosystem is the sun.

- All biological systems rely either directly or indirectly on the sun for energy.
- The amount of energy from the sun reaching the earth’s surface in one year ranges from
two million to eight million kilojoules per square kilometer depending on latitude.

The following is a figure on utilization of energy by producers and consumers.

Sunlight reaching vegetation

20 % reflected
39% transpiration
40% warm up plants, soil and air
1% used in photosynthesis

Vegetation eaten by herbivore

60% un - digested
30% used in respiration
10% new growth

- Energy flow in an ecosystem occurs through feeding relationships.

- In ecology organisms are classified by their feeding relationships.
- Green plants are producers, animals are consumers and in the process of feeding energy
is transferred
- Energy enters a food chain or pyramid through the producers when they carryout
photosynthesis.
- Herbivores feed directly and exclusively on plants, hence are referred to as primary
consumers.
- Animals that feed exclusively on other animals are called carnivores.
- Carnivores feeding on primary consumers are known as secondary consumers.
- Carnivores that feed on secondary consumers are known as tertiary consumers.
- When producers and consumers die decomposers or detritivores feed on the dead plant
and animal materials, releasing inorganic nutrients from the dead organic matter.
- The inorganic nutrients are then reabsorbed by green plants for reuse.

FOOD CHAIN

- Relationship describing which carnivore eats an herbivore that has eaten plants.
E.g.; Grass → insect → lizard → bird

- The plants at the start of a food chain are frequently small in size and very numerous.
- At the end of the food chain the animals are often large and relatively few in numbers.
- The food chain can thus be represented as a pyramid of numbers in which the horizontal
widths of the bands represent the numbers or sometimes the mass (biomass) of the
organisms.

FOOD PYRAMID

- In fact most food chains interconnect with other chains.

- This is because most prey has more than one predator.
- The interconnected food chains form a food web.

FOOD WEB
NB: If the population of one of the animals in a food web is altered all the others are affected.

- The level at which an organism feed in a food chain is called its feeding or trophic level.
- The producers are designated as trophic level 1, because their energy has been transferred
once from sun to plants.
- All the herbivores comprise level 2 because the energy has been transferred twice etc.

NB: Between each trophic level there is an energy transfer.

NUTRIENT CYCLES

- Movement of elements or compounds through living organisms and the non living
environment.
- Nutrients are used and retained in the ecosystem.
- All nutrients flow from the non living to the living and back to the non living components
of the ecosystem in a less cyclic path.
- Green plants build the nutrients in to biologically useful compounds.
- Decomposers return compounds to their simple elemental state.
- Air and water transport nutrients between the biotic and the abiotic components of the
ecosystem.

CARBON CYCLE

- Carbon is a basic constituent of all organic compounds and is involved in the fixation of
energy by photosynthesis.
- The source of all carbon in both living organisms and fossil deposits is carbon dioxide in
the atmosphere and in the waters of earth.
- Photosynthesis draws carbon dioxide from the air and water in to the living component of
the ecosystem.
- Carbon passes to herbivores and then to carnivores through the food chains.
- Primary producers and consumers release carbon dioxide back to the atmosphere in form
of carbon dioxide by respiration.
- The carbon in plant and animal tissues eventually goes to the dead organic matter
reservoir.
- Decomposers release the carbon in the organic matter by respiration.
- Over geologic time build up of partially decomposed organic matter in swamps and
marshes form fossil fuels (oil, coal and natural gas).
- Carbon is released from the fuel through combustion.
- In fresh water and marine environments phytoplankton uses the carbon dioxide that
diffuses in to the upper layers of water or is present as carbonates and converts it in to
plant tissue.
- The carbon then passes from the primary producers through the aquatic food chain.
- The carbon dioxide produced through respiration is either reutilized or reintroduced to the
atmosphere by diffusion from the water surface to the surrounding air.
- Some carbon is bound as carbonates in the bodies of mollusks and foraminifers.

NITROGEN CYCLE
 - Nitrogen is an essential constituent of protein, the building block of all living tissue.
- It is also the major constituent (79%) of the atmosphere.
- In its gaseous state nitrogen is unavailable to most life.
- For nitrogen to be used it has to be fixed first.

Nitrogen fixation is of two types.

1. Cosmic radiation, meteorite trails and lightning produce high energy needed to combine
nitrogen with oxygen and hydrogen of the water.
The resulting ammonia and nitrates are carried to earth’s surface in rain water.

2. The second is a biological fixation accomplished by symbiotic bacteria living in association

with leguminous and root nodule non leguminous plants, by free living aerobic bacteria and
cyanobacteria (blue green algae)

Another source of nitrogen is organic matter.

- Dead organic matter broken down by decomposers releases nitrogen in the ecosystem in
the form of nitrates and ammonia.
- In ammonification decomposers break down amino acids in dead organic material to
release energy.
- Ammonia is then directly absorbed by plant roots and incorporated in to amino acids
which pass through the food chain.
- During nitrification ammonia is oxidized to nitrite and nitrate, yielding energy.
- Nitrogen in the form of nitrate is transformed through denitrification in to gaseous
nitrogen by denitrifiers, e.g. fungi, bacteria etc.

Nitrogen cycle can be constructed from the above mentioned processes.

NITROGEN CYCLE

- In terrestrial ecosystem nitrogen largely in the form of ammonia or nitrates is taken up

by plants which convert it in to amino acids.
- The amino acids are transferred to consumers, which convert them to different types of
amino acids.
- Eventually animal wastes and dead plant and animal tissue are broken down by bacteria
and fungi in to ammonia.
- Ammonia may be lost as gas to the atmosphere, acted upon by nitrifying bacteria or
taken up directly by plants.
- Nitrates may be used by plant, immobilized by microbes, stored in decomposing organic
matter or leached away.
- Leached material runs off to streams, lakes and eventually the sea, where it is available
for use in aquatic ecosystems.
-
EFFECTS OF MAN ON THE ENVIRONMENT

- Ecosystems are self supporting units.

- Most ecosystems have taken hundreds of years to establish a dynamic balance.
- This balance is however disturbed by man’s activities such as agriculture, hunting,
fishing, deforestation and pollution.

AGRICULTURE

a. PLOUGHING
 - Before ploughing a piece of land is cleared.
- So populations of trees, shrubs, wild flowers and grasses are destroyed.
- This trees, shrubs, wild flowers and grasses are habitats and source of food for many
animal species.
- As a result food chains on that piece of land cleared for ploughing is seriously disturbed.

b. MONOCULTRE
- The practice of continuously ploughing the same crop on the same piece of land year
after year.
- Populations of trees, shrubs, wild flowers and grasses are replaced with a dense
population of only one species. E.g. maize, rice etc.

Monoculture leads to;

- Use of same nutrients which gets depleted with time.
- Balanced life of a natural plant and animal community being displaced from farm land
and left to survive only in small areas of wood land.

c. USE OF FERTILIZERS AND EUTOPHICATION

- In natural conditions soil fertility is maintained by the activities of organisms living in it.
- Plant roots maintain the soil crumb structure and animal burrows enhance drainage,
mineral salts removed by the plants are replaced by the death and decomposition of plant
and animal tissues.
- The practice of agriculture interrupts natural cycles by removing the crops at harvest time
and not returning dead remains to the soil.
- In addition monoculture leads to the depletion of the same nutrients that are used again
and again.
- As a result artificial fertilizers or animal manure should be added to the soil so as to
improve its fertility.
- Use of artificial fertilizers greatly contributes to pollution.
- The rate at which plants grow is often limited by how much nitrates and phosphates they
can obtain.
- In recent years the amount of nitrates and phosphates in lakes and rivers has greatly
increased due to use of artificial fertilizers, leading to eutrophication.
- Eutrophication is the enrichment of natural waters with nutrients which allow water to
support an increasing amount of plant life.
- Excessive enrichment leads to an overgrowth of microscopic algae.
- Extra nitrates and phosphates enable algae to increase so rapidly that they cannot be kept
in check by the microscopic animals which normally eat them.
- So algae die and fall to the bottom of the river or lake.
- Their bodies are broken down by bacteria.
- Bacteria need oxygen to carryout this break down and oxygen is taken from the water.
- So much oxygen is taken that the water becomes deoxygenated and can no longer support
animal life.
- Fish and other organisms die from suffocation.
d. USE OF PESTCIDES
- Pesticides are chemicals which destroy agricultural pests or competitors.
- Monocultures with their dense populations of single species and repeated planting are
very susceptible to attack by insects or the spread of fungus.
- The trouble with most pesticides is that they kill indiscriminately.
- For example, insecticides kill not only harmful insects, but the harmless and beneficial
ones, such as the bees which pollinate flowering plants and lady birds which eat aphids.

PESTCIDES IN THE FOOD CHAIN

- The concentration of insecticides often increases as it passes along a food chain.
- For example, clear lake in California was sprayed DDT to kill gnat larvae.
- The insecticide made only a weak solution of 0.015 parts per million (ppm) in the lake
water.
- The microscopic plants and animals which fed in the lake water built up concentrations
of about 5 ppm in their bodies.
- The small fish which fed on the in the lake water built up concentrations of about 5 ppm
in their bodies.
- The small fish were eaten by larger fish which in turn were eaten by birds called grebes.
- The grebes were found to have 1600 ppm of DDT in their body fats and this high
concentration killed many of them.
- A similar build up of pesticides can occur in food chains of land.

OVER STOCKING
- A condition where animals exceed the carrying capacity of the land.

EEFECTS
- Destruction of soil structure, promoting soil erosion.
- Lead to over grazing, thus encouraging soil erosion.
- Eroded soils reduce plant growth and ultimately reduce number of consumers.

DEFORESTRATION
- Cutting down trees for various reasons, including creating space for agriculture, for
timber and furniture, settlements, construction of roads etc.
- Forests have profound effect in climatic water supply and soil maintenance.
- They are known as environmental buffers.
- Forests intercept heavy rain fall and release the water steadily and slowly to the soil
beneath and to the streams and rivers.
- Tree roots hold soil in place.
- Removal of forests allow for soil erosion, silting up of lakes and rivers, devastating
floods and accumulation of carbon dioxide in the atmosphere.
- It also affects the flow of energy in an ecosystem.

FACTORS WHICH CONTRIBUTE TO FAMINE

 - Un-equal distribution of food.
- Natural disasters such as floods, drought and increase in population.

POLLUTION
- The process of making air, soil etc dangerously dirty and not suitable for people to use.
- Releasing substances in to the environment in amounts that cause harmful effects and
which natural biological process cannot easily remove.
- Modern agricultural practices, building and other industries, as well as individual actions
release many pollutants in to the environment.
- Air, land and water are polluted with a range of chemicals and heat.

AIR POLLUTION
- Air is polluted with many gases.
- The main ones are carbon dioxide, carbon monoxide, sulphur dioxide, nitrogen oxides,
methane and chlorofluorocarbons.

1. CARBON DIOXIDE
- Levels of carbon dioxide have been rising for several hundred years.
- Recent rise has been due mainly to the increased burning of fossil fuels.
- Cutting down large areas of tropical rain forests further increased the levels of carbon
dioxide in the atmosphere.
- Increased levels of carbon dioxide contribute to global warming.
- Caron dioxide is one of the green house gases that form a layer in the earth’s atmosphere.
GREEN HOUSE EFFECT AND GLOBAL WARMING
- Short wave radiation from the sun strikes the planet.
- Some is absorbed and some is reflected as longer wave radiation.
- The green house gases absorb then re-emit the radiation towards the earth.
- Some of this long wave radiation, which would otherwise escape in to space come back
to the earths’ surface.
- This is the green house effect and is a major factor in global warming.

A rise in earth’s temperature of only a few degrees will have the following effects,
- Polar ice caps melt and sea level rises.
- It changes the nature of many ecosystems. If species cannot migrate quickly to a new,
appropriate habitat or adapt quickly enough to the changed conditions in the current
habitat they will become extinct.
- Changes in agricultural practices would be necessary as some pests become more
abundant.
- Higher temperatures may allow some pests to complete their life cycles more quickly.
- A change in global rainfall pattern results due to more evaporation from the surface
leading to more rainfall.

2. CARBON MONOXIDE
- Is formed when carbon containing substances are burnt in a limited supply of oxygen.
 - Exhaust gases contain significant amount of carbon monoxide.
- Carbon monoxide is a dangerous pollutant as it is colourless, odorless and tasteless.
- If one inhales carbon monoxide for a period of time more and more hemoglobin becomes
bound to carbon monoxide and so cannot bind to oxygen.
- As a result one loses consciousness and may eventually die due to lack of oxygen.

3. SULPHUR DIOXIDE
- Is formed when fossil fuels are burnt.
- Sulphur dioxide can be carried hundreds of miles in the atmosphere before finally
combining with rain water to form acid rain.
- Sulphur dioxide is the major constituent of acid rain.

Acid rain causes problems in the environment including;

- Soils become acidic, causing leaching of minerals and inhibition of decay.
- Water in lakes and rivers collects excess minerals and that leads to death of fish and
invertebrates.
- This disturbs aquatic food chains.

4. NITROGEN OXIDES
- Also contribute to acid rain.
- They are formed from combustion of fossil fuels.

5. METHANE
- Is an organic gas.
- Produced when micro organisms ferment larger organic molecules to release energy.
- Methane is a greenhouse gas with effects similar to carbon dioxide.

WATER POLLUTION
- Human activities sometimes pollute streams, rivers, lakes and even coastal waters.
- This affects the living organisms in water and sometimes poisons humans or infects them
with diseases.
- The main pollutants of water include nitrates from fertilizers, organic waste (sewage) and
detergents.

FERTILIZERS
- Farmers add inorganic fertilizers to soils, to replace mineral ions lost when crops are
removed.
- The ions in these fertilizers are very soluble.
- As a result they are easily leached (carried out with water) from the soils and can enter
water bodies.
- Accumulation of inorganic fertilizers in fresh water sources eventually leads to
eutrophication.
SEWAGE
- Water can sometime be polluted with large amounts of organic matter, for example when
untreated sewage is released in to water sources.
- Bacteria and fungi decay the untreated waste, using up oxygen as they respire.
- So much oxygen is used by the bacteria and fungi and this leads fish and other aquatic
animals dying due to lack of oxygen

OIL
- Oil is another familiar water pollutant.
- When oil is spilled in to water bodies it forms a layer on the surface of the water, hence
interferes with free movement of air.
- As a result there will be insufficient supply of oxygen to aquatic organisms, leading to
suffocation and eventually death.
- Oil also makes birds feathers to stick together and as a result they are not able to fly
efficiently.

CONSERVATION
- Conserving whatever is present now for future generation to be able to use.
- A wise use of natural resources.

Natural resources include

- Plants
- Water
- Fossil fuels
- Soil
- Minerals
- Animals etc.

WILD LIFE CONSERVATION

- Wild life is a major tourist attraction and source of income for Botswana.
- Both plants and animals need to be protected to ensure continued existence.

EXAMPLES OF LOCAL PLANTS THAT ARE INTENSIVELY USED AND NEED TO

BE CONSERVED
- Sengaparile – medicine
- Mosukujane – make tea or to increase tea flavor.
- Monepenepe – medicine
- Mowana and mukwa – timber.

EXAMPLES OF ANIMALS THAT NEED TO BE CONSERVED

- Wild dogs
- Cheetah
- Rhino etc

WAYS OF CONSERVING WILD LIFE

- Re-planting trees as old ones are cut.
 - Using alternative sources of energy such as solar, biogas and coal.
- Setting up game reserves and national parks.

RECYCLING
- Use materials more than once, E.g. cans, bottles, glass, water, paper etc.
- Paper can be recycled to make useable materials, such as toilet paper.
- Used metals can be smelted and used to make products such as corrugated metal sheets.
- Bottles can be recycled in order to cut on the costs of making glass and bottles.
- Sewage water can be recycled and used for irrigation.