UNIT 5. ECOSYSTEMS (NATURAL SCIENCE)

UNIT 5. ECOSYSTEMS

Ecosystems include a physical environment, living things who  live there and the interaction between them. Each ecosystem is unique  although they sometimes have similar characeristics.

WHAT MAKES UP AN ECOSYSTEM?

·        Ecosystem organisation

-          Ecosystem: marine ecosystems are one of the largest because they include many different: coral reefs, open oceans, etc. There are a lot of living things.

-          Habitat: place where an organism lives. For example, marine hábitats are varied.

-          Population: organisms of the same species within an ecosystem. For example, bacteria, algae (big population) or mammals (small number).

-          Community: Different populations which interact with each other.  For example, mammals, fish and invertebrates living together.

DIFFERENT ECOSYSTEMS AND HABITATS

·         Tropical rainforests

They are found at equatorial latitudes (river basins of the Amazon and Congo Rivers and the islands of Indonesia). There are 12 hours of sunshine  and warm wet climate, that encourages biodiversity.

1.       Emergent layer: tres about 50 – 60 metres tall which are adapted to survive in hot temperaturas and strong winds.

2.       Canopy layer: more tan 30 metres tall and many mmamals, birds, insects and reptiles live there.

3.       Understory layer:  trunks, branches, bushes and shrubs Predatoris and snakes live here and some mmmals, reptiles and amphibians too.

4.       Forest floor: Invertebrates, fungi and bacteria . It is dark, with Little light.

·         Tundra

The ecosystems of Tundra are in the areas around the Artic Circle and some parts of the Antarctica. It has low temperatures , permafrost (layer of frozen soil), Little rainfall and short summer seson.  There are few trees, just some mosses, lichens and shrubs. There are some animals like: arctic foxes, arctic hares, reindeer, polar bears.

FOOD CHAINS AND FOOD WEBS

Some organisms make their own food (plants) and others, feed on other organisms. These relationships between different species form food webs and they are made up of many food chains. In a food chain there are three levels:

1.       Producers (autotrophs): are the basis of a food chain and make their food, for example plants and some protists.

2.       Consumers (heterotrophs): feed on other living things. There are three types:

§  Primary consumers: feed on plants. Herbivores are primary consumers, for example, giraffes.

§  Secondary consumers: feed on primary consumers. They can be carnivores and omnivores. A predator is the animal who eats other animal and a prey is the animal who is eaten.

§  Tertiary consumers: feed on secondary consumers. They can be carnivores and omnivores.

3.       Decomposers feed on dead organic matter. Most decomposers are fungi and bacteria.

·         Food webs

Food webs produce energy, it means biomass ( food for the next trophic level). Producers produce most of the biomass, higher levels produce much less biomass. In a healthy food chain there are more plants than herbivores or carnivores. If the food web is damaged, the biomass can decline and the ecosystem can be in danger.