Mechanisms Of Evolution Flashcards
Define stablishing Selection
Acts against individuals who deviate too far from the average, favours the average
What is an example of Stabilizing selection?
A plant that is too short may not be able to compete with other plants for sunlight, whereas tall plants may be susceptible to wind damage. Combined, these two selection pressures select to maintain plants of a medium height.
Define natural selection
Traits in different forms of life that better enable them to adapt to specific environmental pressures. For example, predators, changes in climates or competition for food or mates. Some traits will survive an reproduce in greater numbers thus ensuring the perpetuation of these favourable traits in succeeding generations.
What are the 3 types of natural selection?
Stabilising selection
Distrusting selection
Directional selection
What is Darwin’s theory
Natural selection- traits change over time
Define evolution
The change of something over time
Define speciation
The making of new species- a process in which two populations become reproductively isolated from eachother
Without isolating groups in a population, any new genes will be spread through the entire population
New genes allow for a survival advantage then the whole population would gradually change
By preventing the mixing of new genes, different species can develop from a common ancestor.
Speciation requires reproductive isolation
Reproductive isolation
Occurs when two members of two populations - but from the same species- can not interbreed. At that point, they have different gene pools.
What is geographic isolation
Physical barriers (rivers, oceans, mountains) preventing mixing of populations
What is habitat isolation
Species found in the same region but prefer different habitats eg. lizards in swamps as opposed to forests
What is temporal isolation
Species breed at different times of the year
Western shrunk = summer
Eastern shrunk = winter
(Overlap but seperate species)
Behavioural isolation
Two populations capable of interbreeding, but have differences in courtship/mating rituals or other types of behaviour (different bird songs, mating colours or dances, etc.)
What are the different types of speciation?
Divergent:
Gradual accumulation of many small genetic changes through differential natural selection with sub populations existing simultaneously
Phyletic:
Abrupt mutations in a few regulatory genes occur after the species has survived for a long time to produce entirely new species
The pattern of evolution?
Gradualism:
Accumulation of small genetic differences over millions of years without reproductive isolation driven by natural selection
Punctuated Equilibrium:
Small number of genetic changes occur rapidly after years of morphological stability, possibly due to the mutations of a few important genes
Sexual selection
Mode of natural selection where members of one biological sex choose mates of the other sex to make with
Compete with members of the same sex for members of the opposite sex
Mutation?
Mutation is the permanent alteration of the nucleotide sequence of the genome of an organism, virus, DNA or other genetic elements
Gene flow
The transfer of alleles or genes from one population to another
Genetic drift?
Mechanism of evolution where allele frequencies of a population change over generations due to chance
Convergent evolution
Organisms that aren’t closely related independently evolve similar traits
Due to adapting to similar environments or ecological niches
Divergent evolution
Differences between groups of a population of organisms which can usually lead to the formation of new species
Usually a result of living in isolated environments
Parallel evolution
Independent evolution of similar traits starting from a similar ancestral condition
Co-evolution
Occurs when two or more species reciprocally affect each other’s evolution
Such as a bee and flower
Viability
Ability to work sucessfully
Directional selection
Extreme phenotype is favoured over others causing the allele frequency to shift in favour of phenotype
Distruptive selection
Describes changes in population genetics in which extreme values for a trait are favoured
In this case the variance of the trait increases and the population is divided into two distinct groups
Allopatric speciation
Geographic speciation
Sympatric speciation
Process though new species evolve through a single ancestral species inhabiting from the same geographic region
Mechanical isolation
Prezygotic reproductive barrier when different species are isolated by different genitalia
Population bottleneck
Sharp reduction in size of a population due to environmental events such as fire or floods
Analogous structure
Various structures having the same function but have evolved separately thus not sharing the same common ancestor
