Chapter 11 Changes in a Population Over TIme (copy)

Adaptive value

a measure of how well used a particular phenotype is to a particular environmental condition. Phenotypes with high, tend to persist and increase in frequency compared to those with low

Allele

A different form of a gene. Have different DNA sequences, sometimes resulting in different forms of a phenotype. For example, the gene that codes for hairline shape in humans has two alleles - straight and widow’s peak

Allele frequency

The relative proportion of a particular allele in a gene pool. It is typically presenting as a decimal or percentage of the allele of that gene in the gene pool

Antibiotic resistance

The ability of a microbe to survive in the presence of an antimicrobial drug

Artificial selection/ selective breeding

The artificial selection of individuals with desired traits to be interbred. Humans selective breed both plant and animal species, creating specific strains or breeds

Biological fitness

An organism’s ability to survive and reproduce in its natural environment

Bottleneck effect

The impact of substantial population reduction on the smaller remaining population. The remaining population has reduced genetic diversity and is more likely to lose alleles through genetic drift and experience inbreeding

Evolution

A change in the inheritable traits of a population (or species) over successive generations

Founder effect

Occurs when a small group of individuals is genetically isolated from a larger population. The smaller population only has a small portion of the alleles of the original population and usually has lower genetic diversity

Gene flow

The movement if alleles between individuals  of different populations; includes the dispersal of pollen and seeds in plants

Gene pool

All of the alleles in a population

Genetic diversity

The variety of genes or alleles in a population or species

Genetic drift

Random changes to allele frequencies in a gene pool as the result of a chance event. This has a more significant impact on smaller populations, as the chance of death of one individual could eliminate an alleles from the gene pool

Geneotype

The genetic composition of an individual. Contrast with phenotype

Germline mutation

A mutation that can affect gamete formation and can therefore be inherited by offspring

Horizontal gene transfer

The transfer of genes between cells, sometimes of different species, such as transfer of bacteria. Contrasts with inheritance of genes from parent to daughter cell through cell division (vertical gene transfer).

Mutagen

Any substance or condition that causes mutation. Some chemicals and radiation are common types

Mutation

A permanent change in a genetic sequence, including changes to the nucleotide sequence of DNA or chromosomal arrangement. Mutations can have a beneficial effect, a harmful effect or to no effect at all on the survival ability of the individual

Natural selection

A mechanism of evolution. Phenotypes that are well-suited to the environment are more likely to survive and reproduce and pass their alleles onto the next generation

Phenotype

The observable trait; expression of a genotype in an individual for a particular trait. The dominance of the alleles and the environmental conditions influence this. For example, nutrient availability may influence pigment synthesis in flower petals or hair holicals in animals

Reproductive stress

A measure of how many offspring an individual produces, reflecting the likelihood of their alleles being passed on to the next generation

Selection pressures

An environmental factor that affects the survival and reproductive success of an individual based on their phenotype

Somatic mutation

A mutation that occurs in somatic, or non-gamerte, cells of an organism. These types of mutations may affect the individual, but cannot be passed onto offspring. Cancer is a form of this

Trait

A particular characteristic of feature of an organism

Vertical gene transfer

The transfer of genetic material from parents to offspring