NATURAL SCIENCE 4º (UNIT 5 - ECOSYSTEMS)

UNIT 5:  ECOSYSTEMS

■ What is an ecosystem?

● Living things and their surroundings

Where living things live is their habitat.

Each habitat has different physical conditions.

Living things have characteristics and adaptations which permit them to survive in their habitat.

An ecosystem is the combination of a habitat, the living things which live there, and the interaction between them.

● Protecting Ecosystems

In an ecosystem everything is connected and in equilibrium. To protect ecosystems we create protected areas. In these areas is forbidden to pick the plants and flowers, hunt the animals, steal the baby animals, drop litter, etc.

This means that the equilibrium of the ecosystem is not broken.

■ Survival in an ecosystem

● Living things must feed

Living things in and ecosystem must feed to obtain energy and carry out their vital functions.

Living things in food chains:

1. The producers of food

Plants and algae are the producers which use the light from The Sun to transform inorganic substances (water, carbon dioxide) into organic substances, which are their food. This process is photosynthesis.

2. The consumers of food.

They are animals. They feed on plants and algae and other animals. They use the food to obtain energy and grow.

3. The decomposers of food.

They are fungi and bacteria. They obtain energy to live and grow by decomposing the organic substances of other living things. They release inorganic substances which can be used again by the producers of food.

  

● Living things and their adaptations

Every living thing has adaptations which help it to survive and reproduce in its ecosystem.

Adaptations like:

*  A cactus is adapted to living in a desert with little water. Its stem is thick and contains lots of water. It loses little water through evaporation because its leaves are prickles, which are impermeable.

*  A fish is adapted to breathe underwater because of its gills. The gills take oxygen from the water. It is also adapted to swim underwater, because its limbs are fins.

*  A mantis is adapted to live and feed in plants. It is the same colour as the plant and it has spines on its legs to help catch its food.

*  A seal is adapted to live in the polar seas. It has a thick layer of fat to keep it warm and feet like fins to swim.