Ecosystem

Ecosystem:

Ecology

Abiotic

Biotic

Micro-organism

Producers

Consumers

Photosynthesis

Decomposers

herbivores

Carnivores

Omnivores

Ectodermic

Endothermic

Transpiration

Terrestrial

Aquatic

Xerophytes

Mesophytes

Hydrophytes

Acidity

Alkalinity

Aspect

Altitude

Hibernation

Aestivation

An ecosystem is an area in which there exists

relationships between living organisms

themselves and the living organisms and

the non-living environment.

Some examples of ecosystems are: a river, a

grassland, a fallen rock.

The study of all the relationships in an

ecosystem is called ecology.

From it is clear that the ecosystem is made up of 2 components.

These 2 components are living and non-living components.

The living components are also called biotic components or factors.

Examples of the biotic factors are plants and animals.

The non-living components are also called abiotic components or factors.

Water, air, soil and temperature are some examples of abiotic factors.

Feed

Respire

Grow

Respond

Excrete wastes

Reproduce

Movement

The biotic components are the plants and

animals.

It also includes organisms such as the fungi

and lichens as well as the very small

organisms like bacteria.

The bacteria are so small that it can be

seen only with a microscope.

Such organisms that are invisible to the

naked eye are called micro-organisms.

Some algae and fungi are also examples of

micro-organisms.

Producers:

These are biotic factors that have the ability

to make their own food (autotrophic).

They are able to do this by absorbing energy

from the sun.

The process by which they are able to

manufacture their own food by using the

radiant energy is called photosynthesis.

Consumers:

These are organisms that are unable to

manufacture their own food

(heterotrophic).

Are you able to tell why?

There are 3 categories of consumers.

These 3 categories are:

Herbivores: these are organism

that obtain their food from plant

matter.

Can you list some examples?

Carnivores: these are the organism that

feed on animal matter only. Name some

examples.

Omnivores: these are organisms that feed

on both plant and animal matter.

List some examples.

These are organisms that feed on dead organic matter.

They are usually micro-organisms .

But some decomposers can be macroscopic e.g. worms.

Give some examples of decomposers.

As they break down the bodies of the dead organic matter they release important substances back into the environment.

These substances then can be used by green plants.

Water, carbon dioxide, mineral salts and energy in the form of heat are some of the substances that are released by decomposers.

Answer this question in your book.

Explain why decomposers are important to the

environment.

They are important because they release

important nutrients e.g. carbon dioxide, heat

energy, water and mineral salts back into the

soil so that it can be used by other green

plants.

Abiotic factors can be placed into 3 groups.

These 3 groups are :

Climatic factors.

Edaphic factors (soil factors)

Physiographic factors (aspect, slope, altitude)

We shall look at all these factors.

Climatic factors include: light, temperature, water and atmospheric gases.

Temperature:

The temperature of an area can determine the plant life growing in that area.

Remember the places closer to the equator are warmer than those places near the poles.

Animals are also affected by the temperature.

Some animals like the exothermic animals become inactive in the cold winter months because the temperatures are so low.

Some of these animals hibernate to overcome the cold weather.

Some animals like the snail also become dormant when the weather is very dry.

Tabulate the difference between aestivation

and hibernation

aestivation hibernation

Animals become dormant during

very dry periods

Animals become dormant during

very cold periods

Some plants experience excessive water loss

as a result of the high temperature.

The process responsible for this high water loss

is called transpiration.

However plants have many adaptations to

reduce the water loss.

The picture alongside shows

some of these adaptations.

Can you explain these adaptations

in your book.

Adaptation of plants to reduce water loss

Leaves are long and thin to reduce the surface area to reduce water loss.

Leaves are covered with a thick cuticle to reduce water loss.

Leaves have more stomata on the lower surface to reduce water loss by transpiration and these stomata may be sunken.

Leaves may be covered by tiny white hairs to reflect the sunlight so that water loss can be reduced.

Some leaves maybe reduced to thorns to reduce the surface area exposed to the sunthereby reducing water loss.

Stems may be able to store water to survive the dry months.

Define the following terms:

1. Hibernation

2. Aestivation

3. Transpiration

4. Exothermic

5. Endothermic

Differentiate between the following terms

1. Hibernate and aestivate

2. Exothermic and endothermic

Explain how animals are able to overcome

adverse weather conditions.

Definitions:

1. An inactive state that enables animals survive

the cold winter months.

2. An inactive state that enables animals survive

the hot, dry months.

3. The loss of water in the form of water vapour

from the aerial parts of the plant especially

the stomata.

4. Animals whose body temperature changes

with the temperature of the environment.

5. Animals whose body temperature remains

constant.

Differences

Hibernation is an inactive state to survive the

cold winter months, while aestivation is and

inactive state to survive the hot, dry months.

Exothermic animals are animals whose body

temperature changes with that of the

surrounding while endothermic animals are

those whose body temperature remains

constant.

Adaptations to adverse conditions

Some animals e.g. dog curl up in cold weather

so that the long fur is exposed to the cold

wind keeping them warm.

Animals may aestivate to escape hot, dry

conditions, while others mat hibernate to

survive cold winter conditions.

Some animals go into the burrows to escape

the heat e.g. Ground squirrels.

Light

Light is needed by green plants for the process of photosynthesis and is provided by radiation from the sun.

Plants will always be in competition with each other for light.

Some plants prefer full sun where as others prefer shade. Length of daylight also varies in different countries.

Here are some examples:

When plants are crowded together they will grow thin and tall in the hopes of receiving light.

Some plants will climb on others in an attempt to reach the light. Example: vines

Still others will grow on larger trees to reach the sunlight. Example: epiphytes

This is an example of an epiphyte.It grows on the larger tree only to get to the sunlight.It does not depend on the tree for any nutrients.All nutrients and water comes from the rainwater.It only uses the tree for support.

Vines also only use the other

plant for support.

It is not dependent on the

tree for food, it only uses

the tree to reach the

sunlight.

Water is used by both plants and animals for

many different physiological processes.

Plants need water for photosynthesis.

While animals need water for digestion and

transport.

Therefore plants will adapted to absorb and

retain as much water as possible while

animals try to retain as much water as

possible.

Hydrophytes are plants that live in water or around large amounts of water.

These plants are adapted to live in water in the following ways:

They do not have root hairs because water is absorbed through the roots, stems and leaves.

They do not have conducting tissue because each organ is able to absorb water.

Supporting tissue is also absent because the plant is supported by the water.

Since water loss by transpiration is not a problem these plants lack some the adaptations of terrestrial plants, for example the leaves of these plants do not have cuticles.

Try this question:

Explain the value of the hydrophytes not having a cuticle

Here are two pictures of hydrophytes

As you can see some of them have

only their roots in water, while the

others have only their leaves and

flowers floating on the surface.

Some

Hydrophytes are also submerged in

the

water.

Terrestrial plants are plants that live on land.

The biggest problem facing these plants is the lack of water.

These plants have to be able to absorb water and keep the water they absorb.

Terrestrial plants can be grouped according to their water needs.

So these plants can be placed into 3 groups.

These 3 groups are the:

a. Hydrophytes: plants that need an abundance of water

b. Mesophytes: plants that need a moderate amount of water

c. Xerophytes.: plants that can live with very little water.

Xerophytes are adapted to live in extremely

dry conditions in the following way:

Some plants have leaves that are very close to

each other. These leaves overlap each other and

reduces the surface area exposed to the

sunlight.

This would reduce water loss.

In some xerophytes like the one

alongside these leaves have been

reduced to thorns. Can you explain

why this is an advantage for this

plant?

Some of these plants have very thick waxy

cuticles. Can you explain the purpose of this

cuticle.

They also have more stomata on the lower

surface than upper. Why?

The stomata may also be sunken. Can you

explain how this reduces water loss.

The xerophytes have thick cuticles to reduce

water loss by transpiration.

There are more stomata on the lower

surface to reduce water loss by

transpiration

Sunken stomata are present to reduce

transpiration and therefore water loss.

Animals also show adaptations to the

available water.

Animals are adapted to live in water and on

land.

Aquatic animals are those animals that live

in water.

Terrestrial animals are those animals that

live on land.

These animals have special features,

structures and behavior that enables them

to live in their particular habitat.

These animals are adapted to live in water.

They have gills that enable them to extract

oxygen from water.

They also have fins to enable them to swim

and maintain their balance in water.

Some aquatic animals are able

to breathe by means of lungs,

example dolphin, whales and

seals.

Some animals are able to live in dry areas.

Here are some examples:

Camels are able to live for long

periods without water

Insects have exoskeletons

that help to reduce water

loss by evapouration

The kangaroo rat is able to go long

periods without water. It obtains

its water from the food it eats.

Reptiles are able to reduce water loss because

they are covered by dry horny scales

Land that is transitional between terrestrial

and aquatic systems eg. Vlei, mangrove,

estuaries etc

Store water, reduce sediment in rivers,

improve water quality, provide habitats

About 50% of SA’s wetlands have been

destroyed

Water cannot be created or destroyed, but it

can be polluted

97% in the oceans (undrinkable), 2.97% in ice

and snow (unavailable), 0.03% for our use

We are using more and more water

Water cycle (hydrological cycle) pg 244

The atmosphere contains air.

Air is a mixture of gases.

Some of the more important gases that make up the air are: oxygen, carbon dioxide, nitrogen and water vapour.

The composition of these gases are about 78% nitrogen, 21% oxygen and 0.03% carbon dioxide.

Oxygen is required by the both plants and animals for the process of cellular respiration.

During the process of photosynthesis plants absorb carbon dioxide, which is a requirement of photosynthesis.

Nitrogen is required by plants to manufacture proteins.

However plants cannot absorb nitrogen as the N2 gas as it occurs in the atmosphere.

Plants are only able to absorb nitrogen as a nitrate.

Therefore the nitrogen has to be first converted to nitrate before it can be absorbed.

Remember animals get their nitrogen from the plants they eat or other animals that may have eaten plants.

Wind can affect temperature and humidity

Winds are common in some parts of SA

Plants have adapted to prevent water loss

through excessive transpiration

Winds also carry seeds which is important in

pollination.

Young and green plants have stomata on their leaves and stems for gas exchange. Stomata are tiny openings that allow gases to enter

and leave.

Woody plants have tiny pores called lenticels on their stems for gaseous exchange.

Hydrophytes absorb gases through their

entire body surface because there is less

dissolved gases in water than in air.

They are able to do this because their

surface is not covered by cuticle.

Lenticels

Explain how lenticels and stomata are

similar in their function but different in

their structure,

Both the lenticels and stomata are used for

the exchange of gases in plants. But the

stomata are pores that are found in the

stems and leaves of herbaceous plants, while

lenticels are pores found on the stems of

plants that have undergone secondary

thickening.

Aquatic animals have many

different adaptations for

absorbing gases the most

common being the gills of

fish. These gills have a

large surface area therefore as much

oxygen can be absorbed.

Water beetles take air bubbles

under water for gaseous exchange

This is a diagram of the spotted water

beetle the blue bubble at the back is

a part of the air bubble taken under

water for gaseous exchange

There are 3 types of soil.

These 3 types are sand, loam and clay.

Plants grow best in loam soil because it has a good water holding capacity, and is well aerated. It also has a high humus content.

The loam soil has a good water holding capacity because it is made up of medium sized particles.

Plants cannot grow in sandy soil because the soil is very loose and does not offer enough anchorage.

The large particles of sandy soil provides it with a poor water holding capacity.

Clay is made up of very fine particles that become sticky when wet.

Therefore it has a poor water holding capacity.

It is not good for plants because the roots can become waterlogged.

Takes a very long time to form soil

SA has the largest per capita soil loss in the

world!

Soil is composed of sand, silt and clay

Humus (organic matter) gives topsoil its dark

colour

Soils rich in humus are fertile

The pH scale can be used to measure the

acidity or alkalinity of substances in

solution.

An example of a pH scale is shown below.

Different plants require soil with different

pH to survive.

Most plants prefer slightly acidic to neutral

soil while other plants require alkaline soil.

Physiographic factors are those factors that

deal with the physical nature of the area.

Example of such factors are slope of land,

altitude and, for our studies, position of

area in relation to sun.

The physiographic factors that we will

discuss are:

a) Aspect

b) Altitude

c) Slope

Aspect refers to the direction a slope faces (in relation to the sun).

In the southern hemisphere the suns rays come from the north therefore the north facing areas receive more light than the south facing slopes.

The north facing areas would be warmer and drier than south facing slopes.

The north facing areas are drier because of increased evaporation.

Therefore shade loving plants like ferns would be found on the south facing slopes and xerophyteswould be found on the drier, warmer slopes.

The south facing slopes would have more plant and animal life because more water is available.

The slope of a mountain affects the rate of

water run-off.

A steep slope may encourage erosion.

Soil is shallow and infertile with reduced

plant growth.

Plants that grow on slopes are usually

small.

Fewer animals

Altitude refers to the height of the land above sea level.

The climate of areas found at higher altitudes is very different from places at lower altitude due to precipitation, solar radiation, wind and shade.

The areas at higher altitude have lower temperatures, atmospheric pressure and are exposed to stronger winds and more rain.

While those areas at lower altitudes have warmer temperatures, higher atmospheric pressures and lighter winds.

These differences means that the plant and animal life in these areas are very different from each other.

Pine trees that grow on the slopes of mountains are cone shaped to allow the snow to fall off. They have very well developed roots to absorb whatever little water that may be available.

Green and black mambas are found in the warmer coastal areas while the Berg adder is found more commonly in the cooler mountainous areas.

Fish like the trout are found in rivers at high altitude because these waters are colder.

People living in the coastal areas have difficulty in breathing in the higher inland areas because of the lower pressure and therefore less oxygen at the higher altitudes.

Ecosystem: an area in which there are relationships between the living organisms themselves and their non-living environment.

Ecology: a study of all the relationships within an ecosystem.

Abiotic: non living factors of an ecosystem

Biotic: living factors of an ecosystem.

Micro-organism: organisms that are so small that they can only be seen under a microscope.

Producers: organisms that are able to manufacture their own food using the radiant energy of the sun.

Consumers: these are organisms that are unable to manufacture their on own food.

Photosynthesis: process during which green plants use the radiant energy of the sun to make their own food.

Decomposers: organisms that break down dead and decaying matter, releasing nutrients so that they, maybe re-used.

Herbivores: organisms that feed on plant matter only.

Carnivores: organisms that feed on animal matter only.

Omnivores: organisms that feed on both plant and animal matter.

Ectothermic: these are organisms whose body temperature changes with the temperature of the surroundings.

Endothermic: these are organisms whose body temperature remains constant.

Transpiration: process during which plants loose water in the form of water vapour from the stomata.

Terrestrial: these are plants and animals that live on land.

Aquatic: these are plants and animals that live in water.

Xerophytes: these are plants that live in areas with very little or no water.

Mesophytes: these are plants that live in areas of moderate water supply.

Hydrophytes: these are plants that live in areas that contain large amounts of water.

Acidity: substances with a pH less than 7.

Alkalinity: substances in solution that have a pH of more than 7.

Aspect: the direction a slope faces.

Altitude: height of the land above sea level.