2.2 Evolution Flashcards
(25 cards)
what is evolution?
Is the change over time in proportion of a population with 1 or more differing inherited traits.
Name the 3 processes of allele frequency changing and if they are non-random or random?
Natural selection - Non-random
Sexual selection - Non-random
Genetic Drift - Random
Explain mutations.
Cause variation, original source of new sequences of DNA, either deleterious or neutral and rarely advantageous to the fitness of the individual.
Explain natural selection.
Populations produce more offspring than the environment can support, individuals better suited to their environment tend to survive and reproduce passing on favourable alleles. Resulting in the non-random increase in frequency of advantageous alleles and the decrease of deleterious alleles.
What is the term for differences between male and females as a result of sexual selection?
Sexual Dimorphism.
Describe sexual selection.
Non-random process selecting alleles that increase individuals chance of mating and reproducing.
Sexual selection can be due to what two things?
Male-Male rivalry- large size, weaponry increases access to females through conflict
Female choice - females assess fitness of males.
When does genetic drift occur?
When chance events cause random fluctuations in allele frequency from one generation to the next.
Why is genetic drift more important in small populations?
More likely alleles will be lost from the gene pool.
Explain the bottleneck effect.
Genetic drift that can occur when population size is reduced for at least one generation.
Explain the founder effect.
Genetic drift that occurs when a few members of a population are isolated from the larger population and new gene pool isn’t representative of original.
A gene pool is altered by genetic drift because….
Certain alleles may be under or over represented.
What are section pressures?
Environmental factors which influences which individuals pass on their alleles. Can be biotic or abiotic.
What happens when election pressures are strong?
Rate of evolution can be rapid.
The HW principle states what?
In the absence of evolutionary influences allele and genotype frequencies in a population will remain constant over generations.
What are the conditions to m maintain the HW principle?
No natural selection, random mating, no mutations, large population size, no gene flow through migration.
Explain fitness.
Fitness indicates an individuals ability to survive and reproduce, measure of tendency of some organisms to produce more surviving offspring than others. Also refers to contribution to the gene pool by individual genotypes.
What is the absolute fitness?
Ratio between frequency of individuals of a particular genotype after selection to those before selection. If absolute fitness = 1 then genotype stable greater than 1 is increase, less than 1 is decrease.
What is the relative fitness?
Ratio of number of surviving offspring per individual of a particular genotype to the number of surviving offspring per individual with most successful genotype.
What does the term co-evolution mean?
Two or more species evolve in response to selection pressures imposed by each other. (A change in traits of one species acts as a selection pressure on other species.) Often seen in symbiotic relationships.
What is symbiosis?
Co-evoloved intimate relationship between 2 different species.
Explain mutualism.
Both species gain from interaction.
Explain commensalism.
One species is benefitted and one is not effected.
Explain parasitism.
Host is harmed but parasite benefits.
