Evolution + Speciation

Vocabulary:

• Evolution: Basically, change over time

• Biological evolution: a change in an organism’s characteristics over time

• Natural Selection: Requires variation, inheritance, population growth, and differential survival and reproduction

• Variation: The traits among different organisms vary, can be behavioral or physical

• Inheritance: Different traits are passed down from parent to offspring

• Population growth: Overproduction of offspring

• Differential survival and production: Better traits mean an organism is more likely to survive and reproduce

• Phenotypic plasticity: Variation among individuals as a result of environmental influences, rather than a change in genetics. The expression of the phenotypes is what changes

• Heritability: Proportion of phenotypic variation is attributable to genetic variation, this gives the range of phenotypic variation offspring can have, think height in humans. h²=Vg/Vp, where Vg is genetic variance and Vp is phenotypic variance. Its the alleles rather than the genotype that influences this. The higher allele frequency the more likely it is to be passed on.

• Fitness: The number of offspring or genes contributed by an individual

• Sexual selection: Non-random mating or differential reproduction, where mates are chosen based on characteristics. This leads to some non-survival related genes being preferred and therefore focused on by evolution, the frequency will increase over time

• Sexual dimorphism: The difference in appearance between males and females, often as a result of sexual selection

• Survival of the fittest: Different organisms will live based on their traits, the best traits survive to reproduce and the frequency of the trait will increase over time

• Mutation: The basis of all new traits, occurs in sex cells and is heritable. Most are harmful and cause the embryo to die. A couple are just there and don’t have a lot of effect, and a tiny percentage give the offspring an advantage

• Migration: The lack of evolution due to immigration and emigration between different populations. This allows alleles to mix between populations, this causes gene flow and less change due to adaptation

• Genetic drift: A fluxuation in the frequencies of the genes in the population due purely to chance. This happens typically due to mass die offs. More prevalent in smaller populations. Also known as the bottle neck effect with a parent population, a bottleneck disaster, and then the next generation being formed from the surviving individuals.

• Neutral theory: Yes natural selection has a small role, but most of the changes in evolution are due to random chance and not caused by selection. If two alleles are both advantageous the same amount, they have no effect. This has some evidence. Different versions of genes are drifting in different directions due to random chance rather than natural selection. This is a newer theory, that goes along with natural selection doing the fine tuning of evolution.

• Allele frequency: The relative abundancy of alleles in a population (how many of the total alleles are a specific allele)

• Genetic equilibrium: No change in allele frequencies between populations

• Hardy Weinberg equation: p²+2pq+q²=1, and p+q=1. Assumes the following. This is rarely true in the real world, having it apply means there is no evolution

  • Large population with random mating

  • No migration in or out

  • No mutations of genes

  • All allele combinations have the same chance of reproducing

  • No genetic drift

• Directional selection: One end of an allele distribution does well and the other end doesn’t and dies when a selective pressure is applied, the shift goes one direction

• Stabilizing selection: When a selective pressure is applied to a population and the distribution of alleles, and both ends are reduced giving a larger spike

• Disruptive selection: When a selective pressure is applied to a population and the middle distribution of alleles isn’t fit, making the ends have more individuals in the following generation.

• Speciation: The process of two species diverging from a single parent species. This happens due to isolation of different groups of the parent species. Allele frequencies change and may mutate. The separations can be based on spatial location or time of breeding

• Allopatric speciation: When speciation occurs due to separation of geographic location

• Sympatric speciation: When speciation occurs due to different breeding times

• Different species concepts are used to distinguish one species from another as compared to two different populations of the same species

• Biological species concept: Two populations can interbreed and have fertile offspring with each other

• Phylogenetic approach: Different species are based on emerging from common ancestors in a family tree, each tip is a new species

• Morphological/Phenetic species concept: Physical traits distinguish a species, based on characteristics and fossils and such

Mechanisms of evolution:

• Mutation

• Migration

• Genetic drift

• Natural selection

In frog breeding, those who breed in fall tend to be breeding later into the year, and those who breed in late winter tended to be breeding earlier, all due to climate change.

Organisms produce more offspring and seeds than they know will survive for higher chances