Populations, ecosystems, evolution Flashcards
What is a population?
A group of organisms of the same species occupying a particular space at a particular time
What is a gene pool?
Total number of alleles that are present in a population
What is the Hardy Weinberg equation used for?
estimate the frequency of allles in a population
What is assumed when using the Hardy-weinberg principle?
-No mutations occur
-No migration
-Population is large
-No selection pressures
-Mating is random
What are the 3 reasons for variation in alleles or genes?
-Random fertilistaion
-Meiosis
-Mutation
could also be environmental influences
What is a niche?
Species specific role within the environment, how it fits into the ecosystem
What happens to species within the same niche?
Compete with each other, natural selection
What are Abiotic factors?
Non-living aspects of an ecosystem e.g. temp, light intensity, moisture, soil pH, O2 levels
What is an adaptation?
Feature of an organism that increases its chance of survival.
What is Allopatric speciation?
When two populations become geographically isolated
Define biodiversity
The variety of genes, species, and habitats within a particular area
What are biotic factors?
The living components of an ecosystem e.g. pathogens, predators
What is the ‘carrying capacity’?
The average size of a population that can be supported by an ecosystem over extended periods of time.
Anything above this is not sustainable
What is the chi-squared test?
Stats test used to determine whether a pattern of inheritence is statistically significant
What is a climax community?
The stable community of organisms that exists at the final stage of ecological succession
What is a community?
All of the populations of different species living together in a habitat
What is conservation?
Maintenance of ecosystems and biodiversity by humans in order to preserve the Earth’s resources
What is directional selection?
Favours an extreme phenotype and selects against all other phenotypes
-Change in the environment
-e.g. resistant bacteria
What is disruptive selection?
Favours both individuals with extreme phenotypes and selects against phenotypes close to the
mean
e.g. large animals survive due to increased body fat, and small animals also survivre as they dont need as much food
What is an ecosystem?
Community of living and non-living components of an area and their interactions.
What is evolution?
Gradual change in allele frequencies within a population over time
What is genetic drift?
Change in the frequency of an existing allele in a population
-due to genetic bottleneck or founder effect
What is genetic variation?
Differences in genotypes between members of a population which may occur due to meiosis, mitosis, or random fertilisation
What is a habitat?
The region where an organism normally lives
What is Interspecific competition?
Takes place between members of different species
What is Intraspecific competition?
Takes place between members of the same species
What is ‘Mark-release-recapture’?
Method of estimating the population size of motile organisms.
Involves capturing a sample, marking them, then releasing them. At a later date, another sample is captured
What is a pioneer species?
Species that can survive in hostile environments and colonise bare rock or sand, e.g. lichens
Define predator
An organism that eats other organisms
Define prey
An organism that is eaten by predators
What are selection pressures
Environmental factors that drive evolution by natural selection and limit population sizes e.g. competition
Define Speciation
The formation of a new species due to population being separated and cannot interbreed
2 forms:
allopatric
sympatric
What is a species?
A group of similar organisms that are able to breed with one another to produce fertile offspring
What is stabilising selection?
A type of selection that favours individuals with phenotypes close to the mean, and selects against extreme phenotypes.
-successful characteristics are preserved, does not occur due to a change in environment
What is succession?
Describes changes in the community of organisms occupying a certain area over time.
What is sympatric speciation?
Occurs when two populations within the same area become reproductively isolated.
What is variation?
The differences between individuals due to genes, the environment, or a combination of both.
What happens if organisms have an unsustainably large number of offspring?
They cannot all survive due to limited resources, so have to compete, natural selection
Briefly summarise the process of evolution via natural selection
-Variety of phenotypes within a population
-Environmental change occurs, selection pressures change
-Some have advantageous alleles so a selective advantage, allow them to survive and reproduce
-Advantageous alleles are passed onto offspring
-Frequency of alleles in a population changes
What is selection?
Process by which individuals who are better adapted to their environment are more likely to survive and breed.
What is Predation?
When the prey is caught and eaten by the predator , the ‘predator-prey relationship’
What is primary succession?
When an area previously devoid of life is colonised by communities of organisms, for example the eruption of a volcano which would lead to the formation of a rock surface
Explain the process of succession
-The area is first colonised by pioneer species such as lichens, on bare rock.
-As organisms die, they are decomposed by microorganisms, which turns into soil, where more organisms can grow.
-Over time the soil becomes more rich in minerals, so larger plants and shrubs survive.
-Eventually, a climax community is established, a self-sustaining and stable community of organisms.
What is secondary succession?
When a previously colonised area in which an existing community has been cleared e.g a forest fire, and a soil layer is already present
