4.1 Different ecosystems

The flowers and fruit borne by some trees are a source of food for many creatures.

The resin emitted by some trees is also important for certain animals.

When leaves or fruit fall from the trees and collect at the feet of the trees, another series of organisms can appear. The decomposers , such as micro-organisms that cause the dead material to decay and decompose, contribute to the decomposition of the nutrients so that they may return to the soil. Humus is formed in this way. Humus is dead organic material. Other creatures that live off decayed organic material, namely the detrivores , also promote this process of decomposition.

• Poster to illustrate the Role-players in a Tree Ecosystem

• Bring pictures of animals, trees and other plants to class. The teacher will divide the class into groups.
• Each group will prepare a poster to illustrate the mutual dependence of the trees, other plants and animals. Each group must present its poster to the rest of the class.
• Answer the following questions / follow the instructions arising from the class discussion:

QUESTIONS / INSTRUCTIONS

1. Supposing the tree on your poster were to fall over.

1.1 Which organisms would die?

1.2 Which organisms would move away?

1.3 Which organisms would increase in number?

2. Describe the role played by trees in an ecosystem.

3. Ecologically speaking, why is it bad practice to rake up leaves under trees?

4. Name three more examples where humans harm ecosystems.

Assessment of POSTER and interpretation of related questions:

Were you able to use the joint information in order to answer the questions?

[LO 1.2; LO1.3]

Activity:

To discuss rock pool ecosystems

[lo 2.1; lo2.2; lo2.3]

This ecosystem is extremely sensitive. The main factor that plays a role here, is TIDES.

The tide changes twice every 24 hours. As a result of the wave action, cold, oxygen-rich sea water washes over the rock pool communities. During low tide the water in the rock pools heats up and evaporation takes place. These changes contribute to the adaptation of the organisms that live in the rock pools so that they may survive the various challenges of nature.

1. Describe what you understand by “a rock pool”.

2. List all the abiotic factors that have an impact on rock pools.

Plants in rock pools

The most common plants are sea-weeds or sea-algae. They are red, green or brown.

Although they are not always green, they can also produce nutrients through photosynthesis. Therefore they are also producers.

They also provide nutrition for a wide range of other organisms that live off them, such as mussels and some sea-snails.

1. Do research in order to describe what each of the following is:

(a) filter feeders:

(b) scavengers:

2. What would the purpose of tentacles be in sea-anemones?

3. What kind of mutual dependence exists between the organisms in a rock pool?

Assessment of the interpretation of the SKETCHES

Could you distinguish the basic rock pool components?

[LO 2.1; LO 2.2; LO 2.3]

Assessment

LO 1: Scientific investigations:

The learner will be able to act confidently on curiosity about natural phenomena, and to investigate relationships and solve problems in scientific, technological and environmental contexts.

This is evident when the learner:

• plans investigations;
• conducts investigations and collects data;
• evaluates data and communicates findings.

LO 2: Constructing Science Knowledge:

The learner will know and be able to interpret and apply scientific, technological and environmental knowledge.

This is evident when the learner:

• recalls meaningful information;
• categorises information;
• interprets information;

2.4 applies knowledge.

Memorandum

Activity: Discussing the value of a grassland ecosystem

Activity: Discussing a forest / tree ecosystem

Questions

1. Suppose the tree depicted in your poster were to topple over;

a. Plants that grow in the shade and have no resistance against direct sunlight.

b. Some creatures like birds and squirrels.

c. Decomposers like bacteria and fungi.

2. Accept the answers offered by learners, but ensure that the following are listed: habitat, shelter, source of food, shade.

3. Decomposition and the formation of humus are retarded: raw materials are not returned to the soil and the soil is impoverished.

4. Overgrazing, introduction of exotic plants, pollution.

Activity: Discussing a rock pool ecosystems

1. Accept the descriptions offered by learners. The following must form part of the information provided: saltwater, shallow water, high tide and low tide, extreme variations in a biotic conditions.

2. Wave action, wind, drying out, solar heating, pollution by people.

Questions

1. Research:

(a) Feeders that use filtering: mussels: minute food particles are filtered out of the water that flows through delicate structures.

(b) Carrion eaters: eaters of dead animals, e.g. crabs.

2. Tentacles: These grab bits of food from all directions and stuff it into the mouth in the absence of the senses of sight and smell.

3. Food-related aspects as touched on in earlier questions.

4. Shelter: plants provide shelter against predators.