Life Science

The Biosphere: The portion of the Earth in which living organisms are found (Living
organisms exist 8km above and below the Earth’s surface-that has the best
conditions for life, and has most living organisms existing in this portion)

The Biosphere is made up of:

1. Atmosphere, layer of gases surrounding the Earth
2. Lithosphere, soil and rock forming the upper layers of the Earth’s surface
3. Hydrosphere, the waters, seas, large bodies of water
Biomes
As Earth has different climates, hot and dry or cold with snow or generally hot and
rainy, so different organisms may be suited to live in different climates. We say that
these animals are adapted to survive in these regions. There aren’t distinct
boundaries that separate biomes, making it hard to classify
Biome: Any regions with a distinct climate together with all organisms that live in this
region

Savannah Biome
 SA’s largest biome(46%), occurs in Mpumalanga, Limpopo, KZN and Eastern
Cape
 Summers are hot and wet, winters are cool with little rain
 Soil is largely sandy, with moderate nutrients
 Vegetation- grasses, shrubs and trees-low rainfall and regular fires prevent
trees dominating
-ideal for grazing animals
-bushveld houses the marula tree,
-baobab also occurs here
 Animals: the big 5, birds of prey-attracts alot of revenue through tourism

Grassland Biome
 Gauteng, Mpumalanga, KZN, Eastern Cape, Free State, Lesotho and Swaziland,
and North-West Province
 Summers are hot with high rainfall, winters are cold with frost
 Grasslands have high humus content, high rainfall areas have leached soil that
becomes acidic
 Vegetation: dominated by grass
-sweet grasses, grow on fertile soil and are preferred by animals as they have
good value throughout the year
 -sour grasses, grown on infertile soil and are avoided by animals as they don’t
have much food value
 Animal Life: bok, blesbok, springbok, birds, sungazer lizards

Nama Karoo Biome

 Northern Cape
 Semi-desert with little rain, summers are very hot and winters are very cold
 The soil is rich in nutrients
 Vegetation: dominated by grasses and shrubs, stone plants
 Animal Life: those that can survive in extreme weathers, fox, hare, jackals,
dassies

Succulent Karoo Biome

 Northern Cape, Western Cape
 Hot summers, cold winters, low rainfall
 Soil is fertile, with red clay and shake and quartz pebbles occur between rocks
 Vegetation: -dominated by dwarf shrubs
-40% are endemic plants
-colourful plants during spring
-annual plants, avoid dry periods by germinating, growing, flowering, during
moist seasons, then die, surviving the seeds so they can germinate in the next
moist winter
-perennial plants tolerate dry periods by using water stored in leaves and
stems, succulent plants
-non succulent plants, have small leaves to reduce waterloss or drop leaves to
reduce waterloss through transpiration
 Animal Life: meerkat, gecko, bat eared fox

Fynbos Biome
 Western Cape
 Cold and wet Winters, hot and dry Summers
 By the coast, soil is sandy and alkaline. Inward, sand is more acidic. Lowlands,
soil is fertile, kinda neutral. Mountain top soil are acidic and poor quality
 Vegetation:-dwarf shrubs-fynbos
-80% of species are endemic here
-because of the variety of soil, allows for a variety of plants to grow
 Animal Life: geometric tortoise, bok, 250 bird species, zebra
Forest Biome
 Occurs in patches, Mossel bay, KZN, Eastern Cape, Limpopo, Mpumalanga
 Rainfall differs, temperature vary from 20-30⁰C
 Thick layer of soil, mixed with fallen leaves, droppings etc, so the soil is rich
enough to support tall trees, climbing plants and shrubs
 Vegetation:-large shrubs and trees dominate, Quentica yellowwood, forming a
canopy for a layer of shrubs, ferns underneath
 Animal Life: Bushpig, baboon, duiker, monkey, leopard, fruit bat, many
endemic birds, knysna woodpecker and lourie

Thicket Biome
 Along the coasts of KZN, Eastern Cape, valleys
 Occurs in high rainfall areas, but it is not constant, so vegetation isn’t allowed
to develop into forests, and lots of fog occurs
 Thick layer of soil, mixed with fallen leaves,, so there is rich soil to support
woody plants
 Vegetation:- short trees and shrubs, vines. Spekboom, cape honeysuckle,
 Animal Life: monkeys, birds, kudu, elephants

The Desert Biome

 West Coast of Namibia, Namib Desert
 Temp above 30*C with low unpredictable rainfall, this keeps the air dry
increasing its evaporating power
 Problems: unpredictable rainfall, save as much water, reduce water-loss
through evaporation
 Vegetation: when theres rainfall, seeds germinate quickly, resulting in an
explosion of grasses, Welwitschia grow, camelthorn, moringo and mustard
trees. Lichen feed on moisture from logs
 Animals: reptiles, lizards, snakes, geckos, beetles

Ecosystems
Any well defined area in which there is a close interaction between the plants,
animals and their environments is the Ecosystem

Ecotourism: SA’s climate is not all the same and the topography, low lying areas of
the coast and escarpments and the plateaus, of the country varies So as a result of
these 2 factors; many different types of vegetation occur and to each supports its
own animal life
The mountainous areas of South Western Cape, have poor soils and Mediterranean
Climates to support its ‘fynbos’ vegetation.
The coastal regions support dense forest-like vegetation with its own wildlife,
especially adapted to this environment
The great diversity of life forms within a variety of natural geographic setting is one
of the main reasons why parts of our country have become extremely popular
attraction for both local and international tourists.

Ecotourism: the attraction of visitors to ecologically sensitive areas

Ecotourism is beneficial to the visitor, environment and the local people.
Benefits to the visitors: They enjoy the natural beauty of the environment.
Thousands of local and international tourists visit ecotourism sites every year.
Benefits to the Locals: Ecotourism is one of the fastest growing industries,
creates job opportunities as tour guides, ticket sellers and vendors of clothes,
gifts and curios. Also creates business opportunities for travel agencies. So
ecotourism is a major contribution o the economy
It promotes knowledge and awareness of environmental issues like global
warming and sustainable use of natural resources. Some money obtained
from ecotourism could be used to build more protected areas, nature
reserves, and to re-introduce species threatened with extinction and poaching
of animals .

Ethical issues
Responsible ecotourism promotes knowledge and understanding of the environment
and reduces poverty through job creation. Respects human rights and ensures that
its impact on the environment is reduced to the lowest possible level
But, some tour operators simply abuse the public interest into the environment to
promote their businesses, they show little concern for the environment shown by:
 Local people, women, are given lowest level, poor paying jobs, with operators
securing managerial jobs
 Accommodation and catering facilities and curios are run by large companies,
owned by foreigners, so less income from these aspects goes to the locals
 There are less attempts to include exploration and culture of the locals into
the tourist programmes
 There’s no attempts to make sure that their programmes do not negatively
impact the environment, like littering, lighting fires, as noise level increases
the animal stress level increases
 Less profit goes to protecting our biodiversity
 Ecotourism reduces poverty through job creation and business opportunities, but
can lead to exploitation of people and the environment, so ecotourism may crash

Ecology

-the study of all the interactions or relationships within ecosystems

Firstly the relationships amongst all living organisms, includes
plant and plant, animal and animal, animal and plant.
Secondly, ecology involves the relationship between the biotic
and abiotic factors, their interactions.

Biotic Factors
Include Animals, Plants and even micro-organisms. Some of these micro
organisms cause diseases(germs) and are called microbes. Decomposers
are microorganisms that bring about decay and decomposition of dead
plants and animals

Producers-living organisms that contain chlorophyll and manufacture their

own food via photosynthesis, using energy from the sun

Consumers-living organisms that aren’t able to manufacture their own

food as they don’t have chlorophyll to trap light to make their own food.
They obtain their food and energy from feeding on plants-Herbivores.
Some consumer obtain their energy from feeding on animals-Carnivores.
Consumers that get their energy from feeding on plants and animals-
Omnivores.

Decomposers-micro-organisms that feed on dead plants and animals, they

break down the bodies of the dead into simpler substances, water, CO2,
heat, mineral salts. These released substances are re-absorbed by the
green plants to manufacture their own food.

Abiotic Factors
3 Groups: Climatic Factors, Edaphic Factors, Physiographic Factors
Climatic: temperature, light, water, atmospheric gases(wind)
Edaphic: affects the soil, soil type, acidity and alkalinity
Physiographic: slope of the land in relation to the sun, altitude

Temperature
Places that are closer to the equator or warmer than those nearer to the poles. So plants
in the equatorial region are different from plants near the poles
 Summer temps are higher than in Winter. So animals that cant control their body
temps(ectothermic) become inactive during Winter to overcome the low
temperatures, hibernate. Some animals become dormant in Summer, during
drought, so they aestivate
The animals can control their body temps(endothermic) also react to changes in
temps by displaying different behaviours.
High temps can cause excessive water-loss in plants through transpiration. Many
plants can survive at such temps through their adaptations that reduce water-
loss, thick cuticles, thick epidermis, small leaves.

Light
Lights required by green plants to make food through photosynthesis. So
plants will compete to obtain light, in crowded areas they grow thin and
tall to reach sunlight
Some animals have developed pigments in their skins to prevent UV rays
from damaging the innerlying tissues

Water
Water is essential for physiological processes in plants and animals,
plants-photosynthesis, animals for digestion and transportation of food
and waste
So plants will be adapted to absorb as much water as possible, and
animals and plants alike will need to conserve water
Some plants are adapted to live in water, called hydrophytes or
aquatic plants, their roots and stems absorb the water so there’s no
root hairs present. Water doesn’t need to be transported within, so
no xylem is present
They are already supported by water, so don’t need supporting
tissues, parenchyma etc
There’s no need for these plants to reduce water-loss through
transpiration, so cuticles are absent, allowing the leaves to absorb
water from their surroundings
Land/terrestrial plants are adapted to dry conditions, called
Xerophytes, they’re adapted by: having deep rooting system to
absorb the little water in the soil
Leaves are covered in cuticles to reduce water-loss through
transpiration
Stomata are deeply sunken to create pockets of moist air to reduce
water-loss through transpiration
Some plants have thorns etc, to reduce the surface area of exposure
to the sun, reducing water-loss through transpiration
Mesophyte, terrestrial plants that grow in areas neither too wet nor
dry
 Animals have adaptations according to water availability. Some are
adapted to live in water, aquatic animals with gills to absorb the
oxygen from the water, but dolphins, whales and seals must come
to the surface to breath via their lungs.
Some animals are adapted to live in dry habitats like:
-kangaroo rat never drinks water, but gets it from the food it eats.
Camels can go long periods without water. Insects have hard
exteriors to prevent evaporation from their body surfaces. Reptiles
are covered by a hard-scales that reduces water-loss through
evaporation.

Atmospheric Gases
Air in the atmosphere is a mixture of gases, 21% O2,
0.03% CO2, 78% N2 and water vapour. Both animals
and plants use oxygen for respiration, during which
energy is released while performing activities. CO2 is
used by plants during photosynthesis to manufacture
food. Nitrogen is needed by plants and animals to
manufacture proteins, but first it needs to be
converted into to Nitrates to be used.
Plants and animals are adapted to take in
atmospheric gases by:
-plants have stomata on their stems and leaves for
gaseous exchange, and woody plants have lenticels
for gaseous exchange
-the amount of O2 and CO2 (dissolved) in water is
less than that in the atmosphere, so plants living in
water need to maximise the absorption of gases. The
absence of a cuticle in water plants(hydrophytes)
allows a greater surface area for absorption of gases.
-aquatic animals have various adaptations for
gaseous exchange, large gill surfaces to maximise
gas absorption from the water, water beetles carry air
bubbles underwater to use for gaseous exchange.
Edaphic Factors: Soil Types, Soil acidity/alkalinity

Soil Types
3 Types: Sand, Loam and Clay
Plants do not grow well in sandy soil because it has low water holding
capacity.
They don’t grow well in clay as it becomes easily waterlogged, causing roots
to rot
Loam is a good soil for plant growth as it has a good water holding capacity
as its well aerated. But some plants prefer sandy soil, while some prefer soil
with clay

Soil Acidity/Alkalinity
pH scales are used to measure the acidity/alkalinity of the soil. Anything
above 7 is alkaline, anything below 7 is acid and 7 is neutral.
Most plants prefer slightly acidic soil to neutral soils, like ferns, proteas and
azaleas. Other plants, mostly xerophytes, prefer alkaline soils.
Physiographic Factors: Aspect, Altitude

Aspect
The slope of the land get different amounts of sunlight
coverage. Those that are in more sunlight coverage, ‘north
facing slopes’ are warmer and become drier due to increased
evaporation. So shade loving plants are likely to be found in
cool, wetter ‘south facing slopes’. But xerophytic plants will be
found on the warmer slopes. The south facing slopes are
greener with a greater abundance of plants.
Altitude
Higher altitude places are colder as of the lower atmospheric
pressure and are exposed to stronger winds than lower altitude
places. So plants and animals that occur at higher and lower
altitudes will be different from eachother
-pine trees are adapted to grow on mountain slopes, its cone
shaped allowing snow to fall off, roots are developed to obtain
as much water as possible
-Green + Black Mambas prefer the warm coastal areas
although the Berg adder occurs in the cooler mountainous
areas
-Trout prefer cooler waters at high altitude than the low-lying
warmer waters
-Sportsmen+women from the coastal areas have difficulty
performing well at high altitudes because of the lower pressure
and oxygen levels

Seasonal Change
Changes in the seasons show the close relationship
between the abiotic and biotic factors in an
ecosystem
-in Winter, the temp drops and in summer the temp
increases. Ectothermic animals hibernate in the
winter for protection from the cold. Some animals
become dormant(inactive) during Summer to avoid
high temps, they aestivate
-most of SA experience more rain in Summer, but in
some areas like the Western Cape, have most rainfall
in Winter. So in the winter-rainfall areas vegetation
experiences rapid growth in Winter. And in the
Summer rainfall areas vegetation experiences rapid
growth in Summer
-Summer rainfall plants drop their leaves in Autumn
to reduces the amount of water lost during dry-winter
months, called deciduous plants. Plants that keep
their leaves throughout the year are called evergreen
plants
-most parts of the country experience high winds in
early spring, triggers the wind-pollinated plants to
bear flowers
Energy Flow
The sun is our main source of energy. The radiant energy of the sun is
trapped in by the chlorophyll in the green parts of the plant and is used to
make food during photosynthesis. The food and energy are required for:
the plants to grow, production of important organic compounds and for
activities for absorption and chemical reactions.
Animals feed on plants directly/indirectly to obtain food and energy.
animals also use the food and energy for: growth, production of organic
compounds etc. But animals require more energy for their activities as
they are more active. Since there are more plants than animals, plants
can trap and store sufficient energy, not only for their own use but also for
the use of the animals.
Energy is passed from the Sun to Plants to the Animals.
Its first transferred to the herbivore/omnivore, then to lower level
carnivore, then to higher level carnivore. When plants and animals die the
decomposers break up the dead bodies and recycle their energy back into
nature... called the Energy Flow

Food Chains
The path energy takes as it flows directly from one organism to the
next
Green Plants -> Rabbit-> Fox
Food Webs
In nature, the path energy takes is way more complicated than depicted in a food
chain. Generally an organism obtains food from more than one source or it may
provide food for more than 1 type of organism. The relationships look more like a
web rather than a chain.

Tropic Levels
Plants and animals in each habitat may be
grouped together into feeding or Trophic levels.
-1st Level: The green plants as they manufacture
their own food and have highest total energy
-2nd level: herbivores as they feed on green plants
and have a slight lower energy level than green
plants
-3rd Level: carnivores that feed on herbivores as
they have less energy than herbivores
-4th Level: (top)carnivores that feed on other
carnivores as they have less energy than the
carnivores hat they feed on
(Omnivores may belong to any of the 2-4 trophic
levels, depending on their trophic levels as well as
decomposers can occur at all levels depending on
which organism they’re breaking down)
Ecological Pyramids
Pyramid of Energy- calculating the total amount of energy present in each
trophic level in a balanced ecosystem and represented graphically on
sequence into a triangular shape
This indicates the amount of energy in all the organisms at any given
trophic level is less than the previous level/ the pyramid shape is so
because at each level the organism uses some energy and loses some
heat and energy in the process, like excretion and urinating may waste
some material and energy. (less and less energy becomes available for
those organisms at the higher trophic levels.
There are similar patterns with number of organisms at each trophic level-
Pyramid of Numbers
And with the total mass at each trophic level-Pyramid of Biomass
If the ecosystems becomes unbalanced, the pyramidal structures become
altered. Sometimes the pyramids become inverted, with the lowest level
being the smallest and the highest level the largest, forming an upside
down pyramid

Nutrient Cycles

Nutrients: substances that are essential to living organisms, mineral salts,

CO2, O2 and water.
The supply of these substance aren’t unlimited, they can become
exhausted, so they must be processed in a sustainable way so that these
nutrients can be available for re-use; called Nutrient Recycling.
The energy flow is also part of nutrient recycling

The way the nutrients (and energy from the sun)

undergo nutrient recycling:
- Green plants produce organic compounds
during photosynthesis, using energy from the
Sun, CO2 from the atmosphere and water
and mineral salts from the Soil
- The food(containing energy, CO2, H2O and
mineral salts) from the plants is transferred
to animals(herbivores and omnivores) when
they eat the plants
- When plants, herbivores, carnivores and
omnivores die, their dead bodies are
decomposed by decomposers
- The energy in the form of heat and CO2 are
released into the atmosphere, and the water
 and mineral salts are released back into the
soil
- These nutrients thus become available for re-
use by other plants and animals, the
nutrients are recycled
If nutrient recycling didn’t exist, the nutrients
would remain locked in the dead bodies of
plants and animals and nutrients would be
exhausted
The water cycle, carbon cycle, nitrogen cycle
are examples of nutrient cycles.
Water Cycle
2/3 of the earth is covered in water and makes 70% of
protoplasm in plants and animals. Its an organic Compound, with
2 hydrogen to 1 oxygen, H2O, and can exist in all 3 states of
matter, solid, liquid and gases. It is regarded as a universal
solvent. And is used in the following ways:
- Chemical reactions require water to occur
- Used as a medium of transport in plants and animals
- Forms habitat for aquatic organisms
- Humans use water for recreation(activities)
- Plants split water during photosynthesis to make food
- Plants and animals produce water as a by-product during
respiration
- Animals digest food via hydrolysis
- Water rids the body of poisonous waste products
- Water helps the body secrete substances
- Water cools the body during hot weather

The water cycle plays an important role in moving water through the
organisms and through the environment

Its divided into 2 steps: 1)Precipitation, Distribution and Absorption

2) Evaporation and Condensation
1)-Precipitation occurs when water vapour from the
atmosphere(clouds) fall to the ground as rain, frost, mist and hail,
which reaches the soil and runs off into rivers, seas and lakes.
Some water soaks into the soil, remaining around soil particles as
capillary water or reaches the water table
Plants use their roots to absorb water from the soil, animals
obtain water from drinking it from lakes etc and the food that
 they eat. Plants and animals use the water and some of the water
is released back into the environment again. Plants also lose
water vapour during transpiration, while animals lose water
vapour through breathing and sweating.

2)Heating of the air, ground/surface results in water changing

from a liquid to a vapour, the vapour rises into the
atmosphere(evaporation occurs) as the warm air rises. As the air
and water rise to higher altitudes, cooling occurs followed by
condensation of the water-vapour to liquid
This results in cloud formation, and as more water accumulates
at this level, the air becomes more saturated, the clouds are now
holding the maximum amount of water and it begins to fall as
precipitation. Then the cycle begins again

Carbon Cycle

The normal concentration of CO2 in the atmosphere is 0.03% and

also some occurs dissolved in water. Plants use CO2 to make
organic compounds(food) during photosynthesis. Both animals and
plants break down organic compounds during cellular respiration
and release CO2.these 2 processes go hand in hand and maintain
the balance of gases in the atmosphere.
- Carbon from the CO2 become a part form a part of glucose first and
then other organic compounds during photosynthesis
- Animals feed on plants and obtain food(organic compounds)
- Carbon is present in the plants and animals in their organic
compounds(carbs, lipids, chlorophyll, haemoglobin etc)
- Plants and Animals release Carbon in C02 as a product of cellular
respiration., into the water or atmosphere
- When plants and animals die, decomposers break down their bodies
and release more CO2 into the soil or atmosphere
- Sometimes the dead bodies don’t break down completely and the
Carbon becomes locked in; these organisms become compressed
and form fossil fuels
- When these fossil fuels are burnt during combustion, CO2 is
released back into the atmosphere
- The cycle starts again

Oxygen Cycle
The normal concentration of Oxygen in the atmosphere is about 21%.
Some of it is dissolved in waters

The food that plants manufacture during photosynthesis and which

animals eat, all contain energy. This energy is required for growth of
the organisms and for their activities. To release this energy, they need
to undergo cellular respiration, during which oxygen is used from the
atmosphere or water(for aquatic organism). Oxygen from the
atmosphere is also used during combustion of fossil fuels
 Cellular Respiration and combustion release CO2 and energy. This CO2
enters the atmosphere or may diffuse into the water for aquatic
organisms. Plants use the CO2 to make food during photosynthesis, in
which plants release oxygen into the atmosphere or water and the
cycle begins again.

Nitrogen Cycle
Plants and animals require Nitrogen for the formation of Proteins and
for the specialised proteins called enzymes. 79% of atmosphere is
Nitrogen, but plants can’t make use of it unless it is in the form of
Nitrates.

Nitrogen is converted into Nitrates in 2 ways: 1) lightning and rain.

2)Nitrogen fixing Bacteria
Then the roots of plants absorb the nitrates to form the organic
compounds proteins and enzymes. Animals obtain Nitrogen by feeding
on plants directly or by feeding on animals that have eaten
plants(indirectly)

When plants and animals die, the proteins in their bodies become
converted into nitrates in 2 steps. Step 1, some bacteria converts the
proteins into nitrites. Step 2, other bacteria convert nitrites into
nitrates. These nitrates may choose 2 paths, they may be used by
plants to form proteins and enzymes or they may be converted back
into atmospheric nitrogen via denitrifying bacteria

Environmental Concerns and Nutrient Recycling

The greenhouse Effect & Global Warming
CO2 released by all living organisms during cellular respiration and from the
combustion of fossil fuels is absorbed by plants for photosynthesis. So the CO2
concentration should be fairly less and not changing much.
But studies have shown that the CO2 in the atmosphere is steadily rising, as of 2
reasons. 1, there are large-scale destruction of forests to make way for factories
etc, results in a reduced number of plants to absorb all the CO2 released in the
atmosphere. 2, there is an increase of vehicles and no. of power stations, which
means that more fossil fuels are used and more CO2 is released.
When the Earths atmosphere has a normal concentration of CO2, a large amount
of heat energy from the sun bounces back into space. But when the CO2
concentration increases, this high concentration absorbs the heat energy and
reflects the heat in all directions, so it acts like a blanket trapping and preventing
heat from reaching outer space causing Earth’s temp to Rise, called Global
Warming. We also say the increased Co2 concentration brings about a
greenhouse effect.
Causes: melting polar ice caps, coastal flooding, droughts, hurricanes, fewer
crops, increase in disease and extinction of organism
One way of reducing CO2 levels in the atmosphere is to reduce the burning of
fossil fuels. The effects of this reduction will only be felt many years later as there
is still a large amount of CO2 looming in the atmosphere. Nuclear energy may be
used in place, but also comes with the harms of radioactive waste