Advanced higher biology key area 2.2 ( evolution)

Absolute fitness

The ratio between the number of individuals of a particular genotype after selection to those before selection

Bottleneck effect

A sharp reduction in the size of a population due to environmental events or human activities

Co-evolution

The process by which two or more species evolve in response to selection pressures imposed by each other

Commensalism

Symbiosis in which only one of the species benefits ( +/0)

Evolution

The change over time in the proportion of individuals in a population differing in one or more inherited traits

Female choice

A mechanism of sexual selection in which females assess males fitness and choose one to mate with

Fitness

A measure of the tendency of some organisms to produce more surviving offspring than competiting members of the same species

Founder effects

When the gene pool of a new population is not representative of that in the original gene pool ( through isolation of a few members)

Gene pool

The total number of genes and their alleles in a population of one species

Hardy-weinburg ( HW ) principle

In the absence of evolutionary influences, allele and genotype frequencies in a population will remain constant over the generations

Male-male rivalry

A mechanism of sexual selection in which males fight for females ( often with alters or tusks)

Mutualism

Both species in the interaction are interdependent on each other for resources or services

Natural selection

The non-random increase in the frequency of advantageous alleles and the non random decrease in the frequency of deleterious alleles

Parasitism

Symbiosis in which the parasite benefits in terms of energy or nutrients and the host is harmed as a result of the loss of these resources

Red queen hypothesis

States that in co-evolutionary relationship, change in the traits of one species can act as a selection pressures imposed on another species

Relative fitness

The ratio of the number of surviving offspring per individual of a particular genotype to the number of surviving offspring per individual of the most successful genotype

Selection pressures

The environmental factors that influence which individuals in a population pass on their alleles

Sexual dimorphism

Females are generally inconspicuous and males usually have more conspicuous markings and behaviours

Sexual selection

The non-random process involving the the selection of alleles that increase the individuals chances of mating and producing offspring

Symbiosis

Co-,evolved intimate relationships between members of two different species