Sucession and Inheritance Flashcards
What is succession?
Change in an ecosystem over time.
What is primary succession?
What is secondary succession?
When species colonise a new land surface.
When there is already a soil layer. The pioneer species are larger plants.
What is a climax community?
The final stage in ecological succession when the environment is stable.
What is a climactic climax?
A single type of community that forms the final stage of ecological succession for a particular region, e.g. Most of Britain’s climatic climax is oak woodland.
What is a plagioclimax?
When succession is stopped artificially by human activities.
What is the difference between homozygous and heterozygous?
Heterozygous: having two different alleles for a particular gene (Bb).
Homozygous: having two identical alleles for a particular gene (BB or bb).
What are the Hardy-Weinberg equations?
p + q = 1
p^2 + 2pq + q^2 = 1
What is stabilising selection?
Where individuals with alleles for characteristics towards the middle of the range are more likely to survive and reproduce. Occurs when environment isn’t changing.
What is directional selection?
When individuals with alleles for extreme characteristics are more likely to survive and reproduce. Could be in response to environmental change.
What is disruptive selection?
Individuals with extreme alleles are selected leading to bimodal distribution and two phenotype groups. If the two groups become unable to interbreed they may give rise to two different populations.
What does the Hardy-Weinberg principle predict about allele frequency? What are the conditions?
That it won’t change as long as the population is large, there is no immigration, emigration, mutations or natural selection. There also needs to be random mating.
How does a population evolve adaptions? Use knowledge of selection.
There will be natural variation in original colonisers, some of the organisms will we better adapted than others, these organisms will have greater reproductive success causing allele frequencies to change in a population.
Why do the species that are present change during succession?
Different species change the environment and add nutrients to the soil. This makes the habitat less hostile. This allows new species and plants that may be better competitors to grow.
What is a dominant allele?
If it’s present it’s characteristic is always expressed/ shown in the phenotype.
What does the Hardy–Weinberg principle predict?
The frequency/proportion of alleles (of a particular gene), will stay constant from one generation to the next, no genetic change over time, providing no mutation/no selection/population large/population genetically isolated/mating at random/no migration.
