Unit 4 core questions

Define habitat

A place where organisms live

Define population

Organisms of one species found in a particular area

Define community

A group of organisms of different species interacting in a

particular area

Define abiotic factors

The non-living parts of an ecosystem

Define biotic factors

The living parts of an ecosystem

Define ecosystem

A community and the non-living components of its environment

Define niche

The role an organism plays in its habitat; 2. Including how it interacts with biotic and abiotic factors in its environment.

Explain the advantage of species occupying different niches.

Less competition for food/resource

Define interspecific competition

Competition for resources between individuals of different species.

Define intraspecific competition

Competition for resources between individuals of the same species.

In succession, what is a pioneer species?

The first species to colonise a bare or newly formed habitat, capable of surviving in harsh conditions

Explain how the change in species composition occurs in a succession.

Pioneer species present change the habitat / named change

Other species able to colonise

New species better competitors;

What term describes the maximum population size an environment can support over time

Carrying capacity

Give two features of a climax community

The same species are present over a long period of time; Abiotic factors are more or less constant over time

Population sizes remain stable around the carrying capacity;

Explain why the percentage sunlight reaching the ground can decrease in later stages of succession

There are taller trees blocking the sunlight

List some abiotic conditions that may change during succession

1. Percentage of bare rock decreases

2. Soil depth increase

3. Soil pH changes as humus is added

4. Soil organic matter/humus increases

5. Soil mineral ion concentration changes

6. Water retention increases

List some biotic conditions that may change during succession

1. Species richness generally increases

2. Population sizes of individual species change over time

3. Biomass generally increases

4. Competition between species changes as the community develops

Describe and explain how succession occurs

1. Pioneer species colonise a hostile environment and are adapted to survive the initial abiotic conditions

2. Pioneer species modify the environment, for example by contributing organic matter/humus and helping soil to develop

3. These changes make the habitat suitable for additional species

4. New species may outcompete earlier species, so community composition changes over time

5. Species richness and biomass increase, creating more habitats and food sources, which can increase animal diversity

6. As biodiversity of plants increases so does the biodiversity of animals

7. Eventually a relatively stable climax community develops, where species composition changes much less over time.

Define selection pressure

An environmental factor that affects survival and reproduction

Define evolution

A change in allele frequency in a population over time

Define allopatric speciation

The formation of new species as a result of a physical barrier leading to geographical isolation between populations

Define sympatric speciation

The formation of new species where individuals of the same species inhabit the same geographical location and there is no physical barrier between populations