Macroevolution

3C

Genetic Drift

Random chance causes some genes to disappear when individuals die or do not reproduce

Non-random mating

Individuals choose which individuals to mate with. Traits that increases chances of reproduction (not necessarily survival) will increase over time

Mutations

New alleles can be created and added to the gene pool

Gene flow

Individuals move from location to location so as individuals enter and leave populations, their alleles will be added or removed from a gene pool- changing the frequency.

Natural selection

organisms that are more fit for the environment survive and reproduce more than those that are less fit and increase in the population

Bottleneck effect

When a species is subjected to near extinction because of a natural disaster. Prevents majority of genotypes from participating in the next generation

Founder Effect

Rare alleles or combinations of alleles occur at a higher frequency in a population isolated from the general population

Species

Group of similarly constructed organisms capable of interbreeding and producing fertile offspring

Speciation

Process by which new species form

Prezygotic Isolating Mechanism

Prevent reproductive attempts and make it unlikely that fertilization will be successful if mating is attempted

Postzygotic Isolating Mechanism

Prevent hybrid offspring from developing or breeding, even if reproductive attempts have been successful

Allopatric Speciation

A population forms a new species while geographically isolated from its parent population

Sympatric Speciation

A subset of population forms a new species without geographic speciation

Ecological isolation

Species at same loacel occupy different habitats

Temporal Isolation

Species reproduce at different seasons or time of day

Behavioral Isolation

courtship behavior differes or individuals respond to different songs, calls, pheromones, or other signals

Mechanical Isolation

Genitalia between species are unsuitable for one another

Gamete Isolation

Sperm cannot reach or fertilize egg

Biological Species Concept

Species can interbreed and create fertile offspring

• Relies on reproductive isolation

• Does not work well for fossils or asexual organisms

• Does not work well if individuals are geographically isolated (but still could potentially mate)

Evolutionary Species Concept

A single lineage has its own evolutionary history and future

• Relies on traits (tricky because of differences in male and female traits)

• Says two populations that look similar but have been evolving separately are different species

• Works for fossils and asexual organisms

• Hard to determine when one lineage actually separates (scientists may debate)

Zygote Mortality

A hybrid zygote may not be viable, and so it dies

Hybrid Mortality

Hybrid offspring dies shortly before or after birth

Hybrid Sterility

The hybrid zygote may develop into a sterile adult (cannot have children)

F2 Fitness (Hybrid Breakdown)

Even if hybrids can reproduce, their offspring may be unable to reproduce.

Chromosomal Mismatch

Species that have DNA that is too different from each other cannot reproduce

Physiological Rejection

The female reproductive system of one species may kill the sperm of another species, stopping reproduction from occuring

Gradualism

Change in a species occurs gradually over time

Punctuated Equilibrium

Changes happen quickly through sudden events. Horizontal lines represent rapid evolutionary change while vertical lines are periods of equilibrium where minimal change occurs.

Molecular Clock

When nucleic acid changes are neutral (not tied to an adaptation) and accumulate at a fairly constant rate, these changes can be used as a kind of molecular clock. Looks at rate of mutation in DNA or proteins to estimate time of divergence, assuming constant rate of evolution.