Evolution notes

Theory of Evolution

the process by which organisms have changed over time through descent from common ancestors.

Adaptation

any heritable characteristic that increases and organism's ability to survive and reproduce

Fitness

a measure of how well an organism survives and reproduces. Differences in adaptations affect and organism’s fitness

Natural selection

the process by which individuals with higher fitness survive and leave behind a greater number of offspring

What 3 observations did Darwin make

Species vary globally, Species vary locally

Species vary globally

Different but similar animals inhabit separated yet ecologically similar habitats. For example, large flightless birds in grassland biomes

Species vary locally

Different but related species often occupy different habitats within a local area

Species vary over time 

Collected fossils and noted that many extinct animals were very similar to living species

Descent with modification

how over many generations adaptations drive species to evolve in to new ones. All species, living and extinct are descended from common ancestors

Radioactive dating

uses radioactive isotopes to determine age, shows earth is approx 4.5 billion yrs old

Fossil record

shows evolution of modern species from extinct ancestors

Homologous structures

structures shared by related species that were inherited from a common ancestor

Analogous structure

share common function but not common structure. For example, wings in bird and insects evolved separately

Vestigial structure

structures inherited from a common ancestor that are no longer functional. If a structure does not increase fitness, it will not be selected for and will evolve away over time. For example the tailbone in humans

Embryology

early stages of vertebrate embryo developments are very similar. Cells divide and migrate in the same order and patterns

DNA as evidence of evolution

all living things use DNA as their genetic material, transcribed RNA from DNA, and translate proteins from RNA. The triplet genetic code is nearly universal

Divergent evolution

process in which species that descend from a common ancestor become dissimilar

Convergent evolution

process in which certain traits are selected for , interdependent of common ancestry

Homologous proteins

Proteins share similar structures and functions. For example cytochrome c, a protein in the electron transport chain.

Population

a group of individuals in the same species that interbreed to produce offspring

Gene Pool

all the genes and various alleles that are present in a population

Allele frequency

the number of times an allele is present in a population, divided by the total number of alleles present. This is not dependent on dominant vs. recessive; the recessive allele may be more frequent in the gene pool.

Evolution at a genetic level

Change in allele frequencies in a population over time

Genetic equilibrium

if a population is not evolving than the allele frequencies in that population remain constant

Hardy-Weinberg Principle

allele frequencies remain constant unless one or more factors cause them to change

Factors that affect genetic equilibrium

Non random mating/sexual selection, Mutation, Immigration or emigration, Genetic drift, natural selection

Genetic Drift

random change in allele frequencies

Bottleneck affect

type of genetic drift where a large portion of the population dies, leaving behind a population with different allele frequencies.

Founder effect

type of genetic drift where a large portion of a population leaves for a new habitat

2 categories of evidence for evolution

comparative/ observational evidence, biochemical evidence

examples of comparative/observational evidence

Fossil records (homologous, analogous, vestigial structures)

Species variability (locally, over time, across the world)

examples of biochemical evidence

Radioactive dating

DNA

Homologous proteins

embryology

Directional Selection

curve shifts towards the end with higher fitness.

Stabilizing Selection

individuals in the middle are the most fit, so the curve narrows.

Disruptive Selection

the extreme phenotypes are most fit and the median is selected against.

three main ways for populations to become reproductively isolated

Behavioral isolation

Geographical isolation

Temporal isolation

behavioral isolation

there are differences in courtship rituals such as mating songs by birds or insects.

geographical isolation

geographical barriers (rivers, lakes, mountains, etc.) can keep two populations physically separated.

temporal isolation

 two populations reproduce at different times. This is a common cause of reproductive isolation in plants, who tolerate hybrids well.

Species

A population or group of populations whose members can interbreed and produce fertile offspring.

Speciation

The formation of new species

Reproductive Isolation

a mechanism that prevents species from interbreeding, thus maintaining distinct species