UNIT 5: ECOSYSTEMS

1.1 Ecosystems

Living things live in places with different characteristics. They are part of an ecosystem because they depend on one another to live.  A forest, a desert or a river are different ecosystems.

Ecosystems have three important elements:

• The habitat is the place where the living things of an ecosystem live. The characteristics of the habitat decide what ecosystems exist there.

• The living things that live in an ecosystem.

• The relationships that exist between living things and their habitat.

All ecosystems need a source of energy that comes from the Sun.

1.2 The habitat

The characteristics of a habitat, like its water, terrain, humidity or sunlight, decide what kind of ecosystem it is and the kind of living things that can live there.  There are two large groups of ecosystems based on land or water:

·         Aquatic ecosystems.  Water is the main element of these ecosystems.  The water can be freshwater or saltwater.  In these ecosystems, important characteristics are the water’s temperature, its transparency or how much oxygen it has.

·         Terrestrial ecosystems. Land is the main element of these ecosystems.  Important characteristics are how many hours of sunlight the terrain gets, how high it is above sea level or how much precipitation it gets.

1.3 Living things

An ecosystem can have living things from many different species.  We can group them in different ways:

·         Population.  This is a group of living things of the same pecies that live in an ecosystem.

·         Community.  This is a group of different populations living together in an ecosystem.