Processes of Evolution
Individuals of a population are selected for because of the genetic phenotype
Populations evolve because of the individual phenotypes that are selected for.
Only the members of the same species can produce viable, fertile offspring in the next generation. This is a method of establishing if individuals are of the same species.
Natural Selection: Genetic phenotypes interact with the environment around them, either; surviving and producing viable, fertile offspring in the next generation or not. Natural selection guides which genes will be passed on and therefore, bottlenecks genetic variation.
Reproductive Isolation: (Genetic drift,founder effect, sampling error): Is an isolated population that as no in flowing genetic contributions. Genetic traits tend to be passed through the population quickly. Limits variation in the gene pool.
Genetic recombination: Members of the same species, but opposite sex combine genetic material. Yes in a word ‘sex’. Adds variation to the gene pool.
Gene Migration: The flow into or out of a population. A split off population given enough time for natural selection to work can become another species. Adds variation to the gene pool.
Gene Mutation: Change in the genetic code resulting ina mutated phenotype. The majority of mutations are not viable and do not survive. Blindness, Missing limbs, other physical and mental abnormalities are negative mutations. Not all mutations are negative, but most do not survive without cultural assistance. Not to be confused with variation. Adds variation to the gene pool.
Sexual Selection: Within a speciesone sex (usually female) act as a limiting force for the other. Competition for the limiting sex results in sexual selection
Indirect effect
Genetic Drift
Sexual selection
Genetic
Recombination
Migration
Mutation
Decrease gene variability
Increase gene variability
The above diagram illustrates how the five basic processes of evolution: interact to produce a genetic change in the population, which keep certain beneficial traits that allow adaptation to the changing environment.
Chart by Lisa Rodriguez
Geological Time Scale
ERA / PERIOD / EPOCH / MILLIONS OF YEARS AGO / FORMS OF LIFE/ Quaternary / Holocene
(recent)
Pleistocene / 10,000 B.P.
1.8-2 / Dominance of Homo sapiens. (Domestication)
Numerous fossil types of human appear: Homo habilis; Homo erectus: four glacial periods.
(Tool use and use of fire)
CENOZOIC
(Age of mammals) / Tertiary / Pliocene
Miocene
Oligocene
Eocene
Paleocene / 5
7-6
25
35
53
65 / Australopithecines (bipedality)
Sahelanthropus (genus)
True anthropoid apes
Anthropoidea and appearance of Hominoidea
Spread of modern mammalian forms; prosimians flourish.
Appearance of Prosimii.
MESOZIC
(Age of Reptiles) / Cretaceous
Jurassic
Triassic / 136
190
225 / Rise of archaic mammals and birds. Extinction of dinosaurs, pterodactyls, toothed birds. Insectivores appear.
Spread of primitive mammals, pterodactyls first toothed birds. Great age of dinosaurs.
Rise of primitive mammals; pterodactyls; dinosaurs appear; reptiles dominant
PALEOZOIC
(Age of Ancient Life) / Permian
Carboniferous
Devonian
Silurian
Ordovician
Cambrian / 280
345
395
430
500
570 / Spread of amphibians and insects. Reptilian radiation. Mammal-like reptiles.
Primitive reptiles, insects; fern and moss forests.
Rise of fishes and amphibians; spread of forests.
Rise of Ostracoderms. First land plants.
Earliest fishes. Possible land plants.
Trilobites, mollusks, brachiopods and other invertebrates. No land life yet.
PRECAMBRIAN / Periods difficult to define / A few soft multicellular invertebrates.
First known fossils- 3.8 b.y.a.
Life begins?
Formation of the Earth? 5.0 b.y.a.