Revision:Communities and Ecosystems

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Define Ecology

The study of relationships between living organisms and between them and their environment.

Define Ecosystem

A community and its abiotic environment.

Define Population

A group of organisms of the same species living in the same area at the same time and capable of interbreeding.

Define Community

A group of populations living and interacting with each other in a habitat.

Define Species

A group of organisms that could interbreed and produce fertile offspring.

Define Habitat

The environment in which a species normally lives or the location of a living organism.

Explain what is meant by the biosphere

Relatively thin life-supporting stratum of the Earth's surface, extending from a few kilometres into the atmosphere to the deep-sea vents of the ocean. The biosphere is a global ecosystem composed of living organisms (biota) and the abiotic (nonliving) factors from which they derive energy and nutrients.

Describe the fact that photosynthesis involves an energy conversion in which light energy is converted to chemical energy

State that white light from the sun is composed of a range of wavelengths (colours).

State that chlorophylls are the main photosynthetic pigments

Outline the differences in absorption of red, blue, green light by chlorophylls

Pigments absorb certain forms of light depending on their structure. The remaining colours of light are reflected and give rise to the colour perceived by the brain of the observer.

• Chlorophyll A - Purple
• Chlorophyll B - Blue
• Carotenoids - Red

State that light energy is used to split water molecules to produce oxygen and hydrogen, and to produce ATP

State that ATP and hydrogen (derived from the photolysis of water) are used to fix carbon dioxide to make organic molecules

Explain that photosynthesis can be monitored by the production of oxygen, the uptake of carbon dioxide or the increase in biomass

These can be measured via the change in pH, or the flux in gases.

Outline the effects of temperature, light intensity, and carbon dioxide concentration on the rate of photosynthesis

State that respiration involves the breakdown of organic molecules to release energy stored in photosynthesis

Describe what is meant by a food chain giving three examples, each with at least three linkages

An arrangement of the organisms of an ecological community according to the order of predation in which each uses the next usu. lower member as a food source.

Grass ---> Cow ---> Human

Grass ---> Gazelle ---> Tiger

Caplin---> Cod ---> Killer Whale

Grass (producer) ---> mouse (primary consumer) ---> snake (secondary consumer) ---> hawk (tertiary consumer)

Describe what is meant by a food web

The totality of interacting food chains in an ecological community

Define trophic level

The position that an organism occupies in a food chain/pyramid or a group of organisms in a community that occupy the same position in food chains.

Deduce the trophic levels of organisms in a food chain a food web

Draw a food web given appropriate information, containing up to 10 organisms.

Define autotroph

An organism that obtains energy from inorganic matter.

Define heterotroph

An organism that obtains energy and organic matter from other organisms.

Define detritivore

An organism that ingests dead organic matter.

Define Saprotroph

An organism that feeds on dead organic matter using extra-cellular digestion.

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