Natural Selection and Evolution

Linnaeus

Came up with the science of taxonomy (naming and classifying organisms based on observations and similarities) binomial nomenclature

Cuvier

Father of paleontology (study of fossils) and came up with catastrophism (all the main layers of fossils are there because of large catastrophes throughout history)

Gradualism

Slow change over time to a population or species

Uniformitarianism

The same geologic processes from millions of years ago are also occurring today.

Lamarck

Early biologist who came up with two theories: use and disuse; inheritance of acquired characteristics

Use and disuse

If a body part is used more, it will adapt to fit that habitat better.

Inheritance of acquired characteristics

The modifications made in “use and disuse” can be passed on to offspring. Buff baby is wrong.

Darwin

Came up with descent with modification and natural selection.

Descent with modification

All organisms are related. All organisms could be placed on a “tree of life” and observations of ancestors can be made. Most branches are dead ends because 99% of all known species are now extinct

Natural selection

Evolutionary adaptation is the accumulation of inherited characteristics. 5 observations and 3 inferences.

Observation 1

A population will continue to increase exponentially if reproduction is successful.

Observation 2

Populations usually remain at a steady size

Observation 3

Resources are limited

Inference 1

An increase in population size will result in in competition for limited resources

Observation 4

Characteristics in a population vary between individuals

Observation 5

Most of the variation in a population is heritable

Inference 2

Survival of an individual will have something to do with the traits that were inherited. Individuals more fit for a habitat are more likely to survive, win resources, and reproduce.

Inference 3

Gradual change in a population where favorable traits accumulate will occur.

Micro evolution

The change in genetic makeup from generation to generation (individuals are selected, populations evolve)

Gene pool

All alleles at all loci of a population

Point mutation

A few different nucleotides. Change in phenotype.

Chromosomal mutation

Half of the chromosome is missing. Change in the whole body.

Alter allele frequency and cause the most evolutionary change

Natural selection (traits) and genetic drift

Genetic drift

Fluctuation in allele frequency based on a finite population size and chance. Genes lean towards one phenotype.

Bottleneck effect

Sudden change in environment reduces size and only several individuals survive. These individuals may not be reflective of the original gene pool.

Founder effect

Individuals become isolated from a population and establish a new population. Galapagos swimming bird.

Gene flow

Genetic additions/subtractions from a population resulting in a movement of a trait. Ex. Pollen from one island flower moves to another island and spreads its genes to that new location.

Phenotypic polymorphism

Two or more distinct phenotypes are the most common. Black and brown hair.

Average heterozygosity

Average heterozygous loci in a population. 1920 of 13700 of a certain loci are heterozygous = 17%

Geographic variation

Differences in gene pools of separated populations

Clines

Graduated change in trait along a geographic axis

Fitness

The contribution an individual makes to the gene pool of the next generation. 0% = none of the next generation has your genes. 100% = the whole next generation has your genes.

Directional selection

Environmental change or migration shifts the frequency curve.

Disruptive selection

Favors variants (the extremes) and removes intermediates

Stabilizing selection

Removes extreme variants and favors intermediates.

Sexual selection

Natural selection for mating success

Intrasexual selection

Males fighting males for the right to breed with females.

Intersexual selection

Mate choice. Usually female choosing the best male. (“Unfortunate looking”doesn’t get accepted and their genes don’t get passed on)

Sexual reproduction

Inferior to asexual but creates good genetic diversity

Allopatric speciation

Geographical separation leads to creation of a new species

Sympatric speciation

Ecological and behavioral separation. Ex. A plant’s genes change just enough so they can’t breed with other plants of their kind so they create a new species without having to be geographically separated.

Prezygotic isolation

Isolation of an individual from being able to reproduce before a zygote is formed.

Postzygotic isolation

Isolation of an individual from being able to reproduce after a zygote is formed. Zygote fails or offspring dies early in age.