Natural selection Flashcards
fitness
the relative chance that an individual will contribute to the gene pool of the next generation
environmental slection pressure
a factor in the environment that impacts an organisms ability to survive and reproduce
selective advantage
a phenotype that makes an individual more likely to survive
natural selection
the differential survival and reproduction of individuals in a species due to selective advantages and disadvantages conferred by heritable differences their phenotype
evolution
the continual process of change in species of living things, key mechanism is natural selection
acquireed characteristic
a characteristic that an individual develops during its lifetime
are selection pressures allows favoured to one phenotype
no, slective pressures only interact with the organism to provide opposition to its continual survival, some slection pressures will be neutral and no individuals will be favoured
examples of selective pressure
co2 concentration, light avaliablity, predators
selection agent
the elements of the environment that exerts a selection pressure
selection pressure
the environmental factor which causes differential death in members of a species due to phenotypic variation
how does natural selection result in evolution
favourable phenotypes are more likely to survive, reproduce and pass on alleles to offspring than those with less favourable phenotypes, over many generations, the genotypes associated with the favourable phenotype will increase in frequency
how many steps involved in natural selection
5
first step of natural selection
phenotypic variation exists within a population
second step of natural selection
selective pressures influence or act on these variations
third step of natural selection
organisms with phenotypes that are selected foor will survive more, reproduce more, have moore offspring and pass their alleles to their offspring
fourth step of natural selection
less favourable phenotypees will reproduce less
fifth step of natural selection
over many generations the selected for trait will increase in frequency
words to remember steps in natural selection
- variation 2. selective pressure 3. favourable reproduce 4. non-favourable dont reproduce 5. frequency over generations
4 darwin observattion
- phenotypic variation exists within a species 2. offspring inherit the trait of their offspring 3. species priduce more offspring than required to replace themselves 4. there is a struggle to survive
darwins inferences
individuals whose give them more chance to survive and reproduce, produce more offspring than other individuals
the unequal chance of reproduction will lead to accumulation of favourable traits in the population over generations
sexual selection
a form of natural selection in which the selection pressure is the ability to obtain a mate
what causes sexual dimorphism
sexual selection
why is sexual selection harmful
attributes that give an individual more liklihood to obtain a mate can be a threat to survival (e.g attrcat predators)
4 requirements of natural selection
variation, slection pressure, selective advantage and heritability
directional selection
when a selection pressure changes to result ina selective advantage for individuals which are less common in a population
what does directional selection result in
shift in allele and phenotype frequency
what effect does natural selection have on genetic diveristy
reduces it by eliminating alleles that give individuals a selective disadvanteg
result of natural selection on allele frequencies
stabilicies them by reducing the frequencies of traits at either extreme range of phenotypes ina populationdis
disruptive selection
change in selection pressure that changes the selective advantage to be for either end of a distribution but a disaddvantage for the most common phenotype
