Chapter 9 - Grade 11 Bio Evo

Mutation: Description

randomly introduces new alleles into a population

Mutation: Effect

changes allele frequencies m

Gene flow (migration): Description

occurs between two different interbreeding populations that have different allele frequencies (increasing variation)

Gene flow (migration): Effect

may change allele frequencies in either or both populations through a “flow” or movement, of genes (alleles) (increase variation)

Non-random mating: Description

Individuals in a population select mates, often on the basis of their phenotypes

Non-random mating: Effect

Increases proportion of homozygous individuals in a population

Genetic drift: Description

random change in genetic variation from generation to generation due to chance (decreasing variation)

Genetic drift: Effect

Changes frequencies of alleles g (decreasing variation)

Natural selection: Description

result of the environment selecting for individuals in a population with certain traits that make them better suited to survive and reproduce than others in the population

Natural selection: Effect

Over many generations, frequencies of alleles of many different genes may change, resulting in significant changes in the characteristics of a population

Gene flow textbook def

Net movement of alleles from one population to another due to the migration of individuals (increasing variation)

Non random mating textbook def

mating among individuals on the basis of a mate selection for a particular phenotype due to inbreeding

Genetic drift textbook def

the change in frequencies of alleles due to chance events in a breeding populatiion

Founder effect

a change in a gene pool that occurs when a few indiivduals start a new isolated population

Genetic drift example

Coin flip 1000 times, might not be 50 50 in some sample sizes

Bottleneck effect

changes in gene distribution that result from a rapid decrease in population size (often seen in a species driven to the edge of extinction)

Bottleneck effect example

one big bottle = population, pour a few balls into a cup, this cup is now the surviving individuals, the next generation will have a very different gene pool and may not have some of the previous alleles that were in the original population and the ratios will be different

Stabalizing selection

Natural selection that favours intermediate phenotypes and acts against extreme variants (distribution gets narrower) (selection for mid-size individuals)

directional selection

Natural selection that favours the phenotypes at one extreme over another, resulting in the distribution curve of phenotypes shifting in the direction of that extreme (Peak shifts) (selection for mid size individuals) peppered moths

distruptive (diversifying) selection

Natural selection that favours the extremes of a range of phenotypes rather than intermediate phenotypes; this type of selection can result in the elimination of intermediate phenotypes (two peaks form) (selection for small and large individuals)

Sexual selection

Natural selection for mating based, in general, on comeptition between males and choices made by females (ex, peacocks)

Speciation

the formation of new species from existing species. (formation of new species is also sometimes called macroevolution)

Pre-zygotic isolating mechanism

a barrier that either impedes mating between species or prevents fertilization of the eggs if individuals from different species attempt to mate; also called pre-fertilization barrier

Behavioural isolating Mechanism example

The songs of birds, the courtship rituals of elk, the chemical signals (pheromones) of insects

Habitat Isolating Mechanisms

two species may live in the same general region but in different habitats, so they may encounter each other rarely

Temporal Isolating Mechanisms

Many species are kept seperate by timing barriers, ex, may occupy same habitat but mate or flower at different times of day or seasons or years

Mechanical Isolating Mechanisms

Species that are closely related attempt to mate but as they are anatomically incompatible, ex, genitals, flower structure

Gametic Isolating Mechanisms

If gametes do meet, gamete isolation ensures they will rarely fuse to form a zygote. diff methods among species: sperm may not be able to survive in reproductive tract.

Post-zygotic Isolating Mechanisms

A barrier that prevents hybrid zygotes from developing into viable, fertile individuals; also called post fertilization barrier

Hybrid inviability

Gene incompatibility of interbred species may stop development of hybrid zygote during its developement

Hybrid Sterility

two species can mate and produce hybrid offspring, ex, mule. However hybrid may still be sterile due to chromosomes of parents differing in number or structure

Hybrid Breakdown

Every generation of the offspring of the hybrid gets less fit

Sympatric Speciation

Speciation in which populations within the same geographical areas diverge and become reproductively isolated

Allopatric speciation

speciation in which a population is split into two or more isolated groups by a geographical barrier; also called geographical speciation

Example of allopatric speciation

A glacier or lava flow that isolates populations, fluctuations in ocean levels that turn a peninsula into an island, etc. Finches being blown off course during a tropical storm (Darwin’s)

Example of sympatric speciation

Chromosomal changes (in plants), and non random mating (in animals)

Ecological niche

the ecological role and physical distribution of a species in its environment

Adaptive Radiation

the diversification of a common ancestral species into a variety of different adapted species (form of allopatric speciation)

Divergent evolution

a pattern of evolution in which species that were once similar to an acnestral species diverge, or become increasingly distinct

Convergent evolution

a pattern of evolution in which similar traits arise because different species have independently adapted to similar environmental conditions

Gradualism

a model of evolution that views evolutionary change as slow and steady, before and after a divergence

Punctuated equilibrium

a model of evolution that views evolutionary history as long periods of stasis, or equilibrium, that are interrupted by periods of divergence