Unit 11 : Evolution
georges couvier
produced “catastrophism” in which he said a series of catastrophes account for the different strata of fossils
jean-baptiste lamarck
proposed “inheritance of acquired characteristics”, an incorrect theory for a mechanism of evolution. believed that through the use and disuse, organisms can pass on non-heritable characteristics to their offspring. NOT a part of modern evolutionary theory
charles darwin
proposed “natural selection” as a mechanism of evolution. IS a part of modern evolutionary theory
james hutton
proposed “uniformitarianism” in which he said that geological processes are generally slow and take a long time. all theories about geology, must take into account that these processes are slow. said that the earth is much older than many had previously suggested.
charles lyell
popularized hutton’s work
thomas malthus
proposed that war, famine, and disease help to control population growth in people. darwin extended that idea to understanding competition for resources for all organisms
adaptation example—darwin’s finches
inherited characteristics that increase an organism’s chance for survival and reproduction
adaptation
they arise through mutation (randomly) but are selected for by the environment (not randomly)
both physical and behavioral
survival of the fittest
the ability of an individual to survive and reproduce in its specific environment
types of evidence for evolution
fossils, homology, direct observation, biogeography
principle of superposition
in geology, the oldest fossils are the most simple and are the deepest. the youngest fossils are the most complex and are found in the youngest strata.
examples of homologous structures, vestigial structures, and analogous structures
homologous structures: structures that may have different mature forms in different organisms but develop from the same embryonic tissues. comes from common descent
vestigial structures: homologous organs/structures of many animals that are so reduced in size that they are just vestiges, or traces, of homologous organs in other species
analogous structures: structures that share similar function but NOT common ancestry
modern definition of evolution
a change in the relative frequency of alleles in a population over time
two sources of genetic variation
in sexually reproducing organisms: mutation and gene shuffling in sexual reproduction. (gene shuffling is a more important source of variation)
4 mechanisms that change relative frequency
mutation—any change in the sequence of nucleotides
natural selection—the process in which individuals that have certain heritable traits survive and reproduce at a higher rate in their particular environment than other individuals because of those favorable traits
migration (gene flow)—the transfer of genes from one population to another
genetic drift—variation in the relative frequency owing to the chance disappearance of particular genes as individuals die or do not reproduce. (most clearly seen in small populations)
evolution of single gene traits versus polygenic traits
natural selection of single gene traits can be easily graphed as a bar graph. natural selection of polygenic traits (traits that are controlled by more than one gene) are graphed by a bell curve
directional selection, stabilizing selection, and disruptive selection
directional selection: organisms in a population on one or the other end of the bell curve have the highest fitness. the entire bell curve shifts in that direction
stabilizing selection: organisms in a population in the center of a bell curve have the highest fitness. the entire bell curve stays centered in the same area but narrow
disruptive selection: organisms in a population on both ends of the bell curve have the highest fitness. the curve splits into two different bell curves.
definitions
conserved genes/proteins: genes or proteins that are similar/the same across many different but related species
evolution: change in relative frequency of alleles in a population over time
population: a group of individuals of the same species that interbreed
theory: a well-substantiated explanation of same aspect of the natural world that is acquired through the scientific method, and repeatedly confirmed through observation and experimentation
inheritance of acquired characteristics: lamarck’s theory for a mechanism of evolution. incorrect theory for a mechanism for evolution. stated that through use and disuse, organisms can pass on non-heritable characteristics to their offspring. NOT a part of modern evolutionary theory
adaptation: inherited characteristics that increase an organism’s chance for survival and reproduction
descent with modification: each living species has descended, with changes, from other species over time
artificial selection: also called selective breeding; the process by which humans breed other animals and plants for particular traits
natural selection: the process in which individuals that have certain heritable traits survive and reproduce at a higher rate in their particular environment than other individuals because of those favorable traits
fitness: the ability of an individual to survive and reproduce in its specific environment
fossil: the preserved remains or traces of animals, plants, and other organisms from the remote past
homology: similarity resulting from common ancestor
homologous structure: structures that have different mature forms in different organisms but develop from the same embryonic tissues; arise from common descent
embryology: study of organisms’ embryos; evidence for evolution
vestigial structure: homologous organs/structures of many animals are so reduced in size that they are just vestiges, or traces, of homologous organs in other species
convergent evolution: the independent evolution of similar features in different lineages
analogous structures: structures that share similar function but NOT common ancestry
gene pool: consists of all genes, including all the different alleles, that are present in a population
relative frequency: the number of times the allele occurs in a gene pool, compared with the number of times other alleles for the same gene occur; usually expressed as a percentage