One of the obvious ways in which plants and animals interact is that some are food for others.

All living things need to eat in order to obtain:

  • materials to build and repair their bodies
  • energy to live and grow.

 

 

 

 

 

 

Concept Check: Plants and photosynthesis

Plants are able to change the energy of sunlight into food energy through a process called photosynthesis. Not even the cleverest scientists working in the most advanced laboratories have ever managed to do what grasses, herbs and trees do every day.

Plants provide almost all the animals on Earth with food. Without leaves, there would be no caterpillars or cows, without flowers there would be no bees or butterflies, and without fruits there would be no birds or baboons. Without plants, there would be no bread, milk, cabbages or chicken. Without plants we would not exist.

 

 

 

 

 

 

Concept Check: Food pyramids

To find out “who eats whom” in Cape Town’s lowlands, click on the  Food Pyramid. It sorts some of the plants and animals from the poster into different feeding levels, depending on whether they produce (make) or consume (use) food energy:
  • Plants are called Producers because they can produce food energy.
  • Animals are called Consumers because they can only consume food energy.
  • Animals that eat plants are called Herbivores or Primary Consumers.
  • Animals that eat other animals are called Carnivores. They can be Secondary, Tertiary or higher level Consumers.
  • Animals that eat both animals and plants are called Omnivores.

Move you mouse over the pyramid to find the different plants and animals at the different levels in the pyramid.

 

 

 

 

 

 

 

Why use a pyramid?

The size of each of the levels in a food pyramid represents either the number of plants or animals, or the mass of these plants and animals at each level in a particular ecosystem.

Questions

  • Why do you think a triangular shape like a pyramid was chosen to represent the number or mass of plants and animals at each of these levels?

  • Did you find the ant on the pyramid. Why do you think the artist has drawn it between two levels of the food pyramid?

Discuss these question in a small group and share your ideas with the class.

 

 

 

 

 

 

Concept Check: Food chains and food webs

In Ecology, we use simple Food Chains and more complex Food Webs to show “who eats whom”. These diagrams show us how food energy flows from one organism to another in an ecosystem. The arrows represent energy. They link the plants to the herbivores, and the herbivores to the carnivores.

We can use the plants and animals on the poster to build food chains and food webs. Below is an example of a simple lowlands food chain.

 

 

 

 

 

 

 

 

A lowland food web:

Food webs and food chains show us clearly that plants and animals need one another to survive. If a certain species disappears from an ecosystem, this will have an impact on the other plants and animals that interact with that species.

Question

Read the descriptions of the plants and animals in the poster key and draw up your own lowland food chains and food webs.
Fynbos food web key:
  Producer   Herbivore   Carnivore

 

 

 

 

 

 

 

 

Feeding relationships in wetlands

Most of the plants and animals on the poster are terrestrial. This Wetland Food Web shows feeding relationships between plants, animals and micro-organisms in an aquatic ecosystem.

Wetland food web key:
  Producer   Herbivore   Omnivore   Carnivore

 

 

 

 

 

 

 

 

Aquatic food webs are more complicated than terrestrial food webs:

  • The most obvious wetland plants like bulrushes and reeds are so tough that very few animals can eat them while they are alive. Instead, the most important producers in wetlands are microscopic algae and pondweed.
  • In wetlands, microscopic organisms play a very important role in the food web. These include bacteria, algae, protozoa and tiny crustaceans .
  • Small fish, some insect larvae, ducks and flamingoes are able to feed on these microscopic organisms by straining or filtering them out of the water. We call this filter-feeding.
  • Many animals in aquatic ecosystems feed on rotting plant and animal matter called detritus. This is the organic sludge that forms at the bottom of wetlands.