bio exam 3 vocab

Homozygous

An individual with the same allele of a gene on both homologous chromosomes

Heterozygous

An individual with different alleles of a gene on each homolgous chromosomes

Incomplete dominance

One allele is not fully dominant over the other, so the expressed phenotype is a blend of two homozygous phenotypes (red + white = pink)

Codominance

Two alles are fully expressed in heterozygotes; neither allels is dominant or recessive (red + white = spotted)

Pleiotropy

A single gene affects multiple traits

Polygenic inheritance

Alleles of two ro more genes collectively affect a single trait

Mendelian inheritance

• One gene gives rise to one trait

• Alleles are either dominant or recessive

• Alleles of different genes assor independently

Evolution

A change in the line of descent

Biogeography

The study of patterns in the geographic distribution of species and communities

Comparative morphology

The study of anatomical patterns among the body plans of organisms

Fitness

The degree of adaptation to a specific environment

Natural selection

Differential survival and reproduction of individuals of a population based on differences in shared, heritable traits

Homologous Characters

Characters that are similar due to a shared common ancestry

Phylogentic trees

Show hypithesized evolutionary relationships

Trace fossils

Remains or traces of organisms that lived long ago

Half-life

The time it take for half of the atoms in a sample of a radioisotope to decay

Divergent evolution

Evolutionary pattern in which lineages descended from a common ancestor diverge (goes with homologous structures)

Homologous structures

Body structures that may appear different in different lineages, but are dervied from a common ancestral form (goes with divergent evolution)

Convergent evolution

An evolutionary pattern in which similar body parts evolve separately in different lineages (goes with analogous structures)

Analogous structures

Similar body parts that evolved independently in different lineges (goes with convergent evolution)

Gene pool

All alleles of all genes in a population

Allele frequency

The abundance of a particular allele in a gene pool

Microevolution

The change in allele frequency in a population over time

Genetic drift

A chnage in allele frequency due to chance alone

Fixed allele

An allele for which all emembers of a population are homozygous for

Population bottleneck

A drastic reduction in the population size

Founder effect

After a small group of individuals found a new population, allele frequencies in the new population differ from those in the original

Gene flow

The movement of alleles between populations

Macroevolution

Chnage in taxa above the species level

Specieation

The emergence of new species

Reproductive isolation

The end of gene flow between populations

Allopatric speceiation

When gene flow between two populations ends because of a physical barrier

Sympatric speciation

Genetic changes come baout about in populatios without a physical barrier