Natural Selection Flashcards
What are selection pressures
The environmental factors that limit the population of a species
What do the selection pressures determine and also give examples
The frequency of all alleles within the gene pool
Predation, disease and competition
What is a gene pool
The total number of all the allies of all the genes of all the individuals within a particular population at a given time
What does the process of evolution by natural selection depend on
Organisms produce more offspring than can be supported by available supply of food, light, space etc.
There is genetic variety within the populations of all species
A variety of phenotypes that selection operates against
How do they help maintain population size
High reproductive rates have evolved in many species to ensure a sufficiently large population survives to breed and produce the next generation. This compensates for predation, completion for food, water, extremes of temp, natural disasters
Some species have evolved lower reproductive rates along with a high degree of parental care, lowering death rates to maintain population size
What can it lead to when there are too many offspring available for the resources
Competition amongst individuals for the limited resources available (intraspecific competition)
What happens to the individuals in a population best suited to prevailing conditions?
They will be more likely to survive than those less adapted. These individuals will be more likely to breed and so pass on their more favourable allele combinations to the next generation, which will therefore have a different allele frequency from the previous one
What does the natural selection process depend on
Individuals of a population being genetically different from one another
What does having a wide range of genetically different in a population
It means that some will have the combination of genes needed to survive in almost any new set of circumstances
What are populations showing little genetic variation vulnerable to
New diseases and climate changes
What does variation provide
The potential for a population to revive and adapt to new circumstances
