Bio 10

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Evolution

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Genetic change over time.

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Natural selection

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Is the mechanism to achieve evolution.

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Microevolution

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Happening in a small population; change in gene pool

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Macroevolution

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Large scale process; usually the change leads to a new species.

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Adaptations

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Are evolved traits that help an organism become best suited to the conditions presented by its environment

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Mutation

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Alterations to the Dna(substitution, deletions, duplications) that change the expressions of the gene. Cause allele frequencies to change within populations if mutation is passed on.

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Genetic drift

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Changes in population allele frequencies due to random assortment of genes in the gametes; each generation of mating can Alter the allele frequencies.

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Bottleneck effect

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Disaster like a disease, or fire, or complete loss of a resource that kups off significant number of the population causes a drastic change in the allele frequencies.

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Founder effect

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Few individual s leave a population and form a new population of their own, with only a small fraction of the original gene pool

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Gene flow

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Movement of alleles among populations, either by individuals immigrating in our emigrating out, or alleles migrating as gametes when individuals of different populations breed.

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Microevolution, macroevolution

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Two main mechanisms driving evolution.

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Individual variation, inheritance, overproduction, differential fitness

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In order for natural selection to drive evolution of population, the following criteria must be met.

Processes of Evolution- Natural Selection.

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Individual variation

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Organisms within the population are different from one another.

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Inheritance

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Many of the differences are passed to future generations

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Overproduction

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More offspring are produced than will survive.

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Differential fitness

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Individuals that are best adapted to their environment will produce the most offspring, therefore their alleles will be most represented in the population.

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Stabilizing, directional, disruptive.

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Types of natural selection

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Stabilizing selection

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Extreme phenotypes selected against, average types selected for; an advantage when confitiond remain relatively constant.

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Directional selection

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Extreme phenotype becomes the favored one due to a change in environmental conditions; extreme phenotype now has an advantage over more average ones; usually a shift in climate or biome type drives selection-going grassland to forest, a dry climate turns wet, etc.

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Disruptive selection

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2 or more extreme phenotypes favored over intermediates; usually when population occupies different habitats.

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Hardy-weinberg equilibrium

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When population is in a stable state of genetic equilibrium; allele frequencies become static after one generation of tandom mating; population size must be large.

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Speciation

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Splitting of one species into two or more new ones

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Reproductive isolation

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Genetic differences between species prevent viable offspring from being produced.

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Divergence

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Accumulation of genetic differences after isolation from original population; when new population expreriences different selective pressures based on new environment, mutations, and drift; can result in new species.

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Allopatric speciation

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Population becomes separated by a geographic barrier; prevents further gene flow between groups.

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Synpatric speciation

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No barrier, but group becomes isolated from orginal; best illustrated by plants; multiplication of chromosome number prevents successfull reproduc to on with original (polyploidy)

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Adaptive radiation

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Adaptations to a change in environment resulting in a new species; two hypothesis about thid process

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Phylectic gradualism

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Change to organism is slow, steady process

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Punctured equilibrium

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Long periods of stability followed by rapid periods of major changes resulting in speciation

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Extinction

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Permanent loss of a species; over geologic time, species come and go at a fairly steady rate without human interference

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Mass extinction events

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Widespread disappearances of multiple species due to a catastrophic event like a meteor strike, volcano eruption, earthquake, disease epidemic, etc.

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Fitness

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How successful an individual is at reproducing and passing on its genes vs. Another individual of the same species.

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Fossils

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Evidence of evolution. Remains or traces of living organisms, such as bones, teeth, hair, shells, footprints, eggs, seeds, buried sedimentary riocks.

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Archaeopteryx

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Is a famous fossil of what is considered the first bird; shows characteristics of both dinosaurs and birds, teeth claws and a tail and feathers and wings and a I'm beak like nose

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Biogeography

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Evidence of evolution. How organisms are distributed over the earth.

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Homologous structures

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Anatomical structures that are similar due to shared common ancestry. Example. The vertebrae forelimb bones. They evolved from the same species so they have vertebrae, phallenges etc.

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Analogous structures

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Anatomical features that serve the same function but evolves completely separate from each other without common ancestry. Similarities are due to shared functionality. Torpedo shaped fish for swimming.

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Vestigial structures

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Reduced or useless structures that remain in modern organisms which had a purpose and were nore developed in ancestral forms.

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Artificial selection

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Controlling who breeds so that the frequency of certain traits increase.

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Systematics

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Classification and organization of organisms using traits to establish relationships between taxonomic groups.

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Taxonomy

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Naming and classifying organisms using a naming system that follows specific rules.

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Taxonomic groups

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Are hierarchial categories that organisms can be placed in according to their relationship with other members of the group

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Phylogenetics

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A branch of systematics that studies evolutionary relationships of organisms and places then on a "family tree" called a cladogram

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Hominins

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True humans (belonging to genus homo) and speciez closely related. Tendency towards bipedalism.

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Homo habilis

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"Handyman", as they are believed to be first of the group to show tool use.

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Homo ergaster

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Evolved from habilis in africa and emigrated to asia; taller with a larger beain than habilis, but brow ridges and prognathism remain.

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Homo erectus

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"Upright man"; evolved from the ergaster in asia. Direct ancester to modern humans, controlled fire, probably first hunter/gatherers.

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Homo floriensis

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"Hobbit man"

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Homo neandertalensis

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Archaic humans that evolved between 200,000 -28,000 years ago. Brains were actually larger than modern humans.

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Homo sapiens

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Modern humans, earliest skeletal remains of what are considered our species were the cro magnons.

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Multi-regional model

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Is based on homo erectus migrating to different regions and evolving into homo sapiens through similar conditions in each region.

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African emergence model

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Is based on modern humans developing in africa then separating to different regions.