Populations and Change Flashcards
Define “Population”
All organisms of a single species living in a specified area.
Define ‘Sample”
A group of organisms selected as an indicator for the whole population.
Define “Variation”
Differences amongst organisms both between different species and within the same species. Is the result of mutations, natural and artificial selection and is found in genes.
Give the three types of natural selection and define each one.
Directional: One extreme (type of variation) is selected against. Average amount of organisms changes. (Mean)
Stabilizing: Both extremes are selected against, mean doesn’t change.
Disruptive: Mean is selected against and the rarest are the most fit to survive.
What is a mutation?
A change in the genetic make-up. May be helpful but generally isn’t.
Define “Genetic Drift”
A change in allele frequencies due to chance.
What is the Founder Effect?
A small population leaves and migrates to another area to establish a new population.
What is speciation?
Formation of a new species. Usually caused by geographical isolation.
What is Hardy-Weinberg Principle?
Indicates that the gene frequency will remain relatively unchanged unless natural selection occurs.
What are the conditions of Hardy-Weinberg Principle?
Large population, random mating, no migration, no mutations, no evolution.
What are the 4 factors of Population Growth?
Natality (birth rate), Mortality (death rate), Immigration and Emigration.
What is the Law of Minimum?
The essential factor with the smallest concentration controls the population size.
What are the two types of limiting factors?
Density-dependent and density-independent
What are 2 forces controlling population density?
Environmental resistance (the sum of the limiting factors) Biotic potential (optimal rate of reproduction and ideal conditions)
What are the phases of population growth?
Lag phase, growth phase, stationary phase and 1. equilibrium stage or 2. death phase.
