6.5 genetics, evolution and ecosytems

Define ecosystem

All the living organisms found in one area and the non living aspects of their environment

What’s an abiotic factor

Non living features of an ecosystem

Light or temperature

What’s a biotic factor

Living features of an ecosystem

Predators or disease

What is a biomass and how is it transferred

The total weight of living matter in a certain area, transferred up tropic levels through consumption

Can be measured in terms of mass of carbon, or dry mass of tissue

Give the formula for efficiency of biomass transfer

Efficiency = biomass transferred % biomass intake X100

How can human activities affect biomass transfer

Light, water, temperature maximised

Increase nutrients in soil

Pests and weeds removed

Growth rates boosted through steroids, selective breeding

Outline the roles of microorganisms in the nitrogen cycle

Nitrogen fixing bacteria converts gaseous nitrogen to ammonia

Nitrifying bacteria converts ammonia to nitrite to nitrate. (A,B)

Outline the role of organisms in the carbon cycle

Respiration of plants and animals add carbon dioxide into the atmosphere

Photosynthesis of plants removed carbon dioxide from the atmosphere

Decomposes decay plant and animal material into carbon dioxide

Define primary succession

Where an area previously devoid of life is colonised by a community of organisms

Summarise primary succession

Pioneer species able to survive harsh conditions, colonise the area

They die, decompose, and add nutrients to the ground

Overtime this allows more complex organisms to survive

What is the climax community and how is it reached

The final stage of succession where the ecosystem is balanced and stable, it is reached when soil is rich enough to support large trees or shrubs and the environment is no longer changing

What’s deflected succession

Where succession is interrupted, usually by human interference

What is sampling

Selecting a group of individuals that will represent the whole target population

Allows us to measure the distribution and abundance of organisms

Give methods of sampling and explain how they’re used

Quadrants- used in small areas, randomly or regularly placed across a habitat, frequency or percent cover calculated

Transects- used in larger areas, sample taken along a line that crosses the habitat. Can be combined with quadrants in the form of a belt transect

Define carrying capacity

The max population size that a habitat can support defined by the presence of limiting factors

factors that limit the max size of a population

Food, water, light, oxygen, nesting sites, shelter, parasites, predators

Define intraspecific competition

Competition between organisms of the same species

Define interspecific

Competition between organisms of different species

Define conservation

Maintains biodiversity of a habitat by allowing a sustainable use of the recourses there

Define preservation

Maintains biodiversity of a habitat by minimising human impact

Why do we conserve and preserve habitats

Economic, food source

Social, many organisms can be used in medicine

Ethical, responsibility to maintain habitats for future generations

Define sustainability

Using resources in a way that also maintains them for future generations

What methods allow sustainable use of an ecosystems recourses

Timber production, replacing felled trees, selective cutting

Fishing, stocks not depleted no overfishing, can continue indefinitely