EVOLUTION

Concepts/Ideas/Notes:

1. hypothesis that life evolved from simple organic compounds first proposed by Russian scientist Alexander I. Operin (1894 –1980)
2. Miller and Urey tested Oparin’s hypothesis in1953 with an experiment duplicating the Earth’s early atmosphere and producing amino acids.
3. Glycolysis, an anerobic process to create energy, was probably used by the first prokaryotes
4. when allele frequency change, the range of traits in a population will change and evolution will occur.
5. isolation leads to speciation

Definitions:

1. Spontaneous Generation – concept that living organisms can arise from non-living matter.  Francesco Redi’s (1626 –1697) experiment with flies and maggots and Lazzaro Spallanzano (1729-1799) experiment with boiled broth disproved the theory of spontaneous generation.  Any doubt about spontaneous generation was squelched by Louis Pasteur (1822-1895) by his experiment using a curved neck flask, which prevented air particles from entering a sterile broth.
2. Biogenesis – theory that living organisms come only from other living organisms.
3. Fossils – remains or traces of once-living organisms
1. Imprint – type of fossil in which a film of carbon remains after the other elements of an organism have decayed.
2. Mold – type of fossil in which an impression of the shape or track of an organism has survived.
3. Cast – occurs when sediments fill in a cavity left by a fossil mold.
4. Frozen specimen
5. Specimen trapped in hardened resin
6. Specimens trapped in tar pits
7. Remains of actual shell, bone, and teeth
4. Coacervates – enclosed collections of irregular-shaped droplets of complex organic compounds and molecules which can grow larger.
5. Microspheres – enclosed collections of round-shaped droplets consisting of usually only one type of molecule which has the ability to “bud” forming smaller microspheres.
6. Endosymbiosis – theory that prokaryotic intracellular parasites evolved into various cell organelles.
7. Homologous Structures –structures that are embryologically similar, but have different functions.  Animals with homologous structures suggest that these animals evolved from a common ancestor.
8. Analogous Structures – structures that serve similar functions but differ in structure (eg. wings of a bird and the wings of a fly)
9. Vestigial Organs – functionless structure that may be homologous to useful structures in other species which may be viewed as evidence for evolution: organisms having vestigial structures probably share a common ancestry with organisms in which the homologous structure is functional.
10. Evolution – theory that species change over time
11. Half-Life – the period of time it takes for one-half of a radioactive isotope to decay
12. Adaptation – an inherited variation that increases an organism’s chance of survival in a particular environment.
13. Mutation – physical change in a gene or chromosome.  Gene mutations affect gene equilibrium by producing totally new alleles for a trait.
14. Natural Selection – process by which nature chooses surviving progeny and by which evolution occurs.  It is the process by which organisms with more favorable characteristics with respect to their environment leave more surviving progeny.  Natural selection does not cause significant changes leading to the formation of a new species.
1. Stabilizing Selection – type of natural selection in which individuals with the average form of a trait have an advantage in terms of survival and reproduction.  The extreme forms of the trait confer a disadvantage to the organism.  Stabilizing Selection is most effective in a population that has become well adapted to its environment.  It is the most common type of natural selection.
2. Directional Selection – type of natural selection in which individuals with one of the extreme forms of a trait have an advantage in terms of survival and reproduction.  Directional selection occurs in changing environments.
3. Disruptive Selection – type of natural selection in which individuals with either of the extreme forms of a trait have an advantage in terms of survival and reproduction.  Disruptive selection eliminates the intermediate form and favors the extreme forms.
4. Sexual Selection – the preferential choice of a mate based on the presence of a specific trait.  Sexual selection may be stabilizing, directional, or disruptive.
15. Artificial Selection – the process by which breeders of domesticated animals and plants deliberately change the characteristics of the strains or races in which they are interested by mating those organisms that suit a particular trait.
16. Selection – describes the non-random reproduction of genotypes.

1. Ecotypes – genetic races differentiated with respect to particular habitats

17. Cline – a graded series of changes in some characteristics within a species, often correlated with gradual change in climate or another geographical factor.
18. Adaptive Radiation – the evolution from one kind of organism to several divergent forms, each specialized to fit a distinct and diverse way of life.  It most commonly occurs when a species of organisms successfully invades an isolated region where few competing species exist.

2. Punctuated Equilibrium – theory of evolution whereby long periods of gradual change or of no change are punctuated by periods of rapid change in which speciation occurs.
3. Divergent Evolution – process of two or more related species becoming more and more dissimilar.
4. Convergent Evolution – process whereby unrelated species become more and more similar in appearance as they adapt to the same kind of environment.
5. Coevolution – the joint change of two or more species in close interaction.  Predator and prey co-evolve.
6. Species – group of individuals that look similar and whose members are capable of producing fertile offspring in the natural environment
7. Morphology – classification of organisms by the similarities and differences in their internal and external structures.
8. Isomorphic – different in ancestry, but having the same form or appearance.
9. Morphological Species Concept – difference of appearance is used as the major criteria for classifying organisms.
10. Biological Species Concept –the major criteria for classifying organisms is whether or not organisms naturally breed with each other or not and produce fertile offspring..
11. Hybrid – offspring of two morphological dissimilar organisms
12. Populations – groups of individuals, usually of one species, that occur together at a given place.
13. Genotype – genetic make-up of an individual
14. Phenotype  - the outward appearance of and organism
15. Gene Pool – collection of genes from all the traits in a population
16. Allele Frequency – percentage of a specific allele of a gene in a gene pool
17. Genetic Equilibrium – occur when the frequency of a gene does not change from generation to generation.
18. Gene Flow – The movement of genes into or out of a population through migration
19. Speciation – formation of new species
20. Geographic Isolation – the physical separation of members of a population
21. Reproductive Isolation – the inability of formerly interbreeding organisms to produce offspring.  This can arise through disruptive selection.
22. Extinction – species die off and no longer exist.

Disruptions of Genetic Equilibrium:

1. Mutation – physical change in a gene or chromosome.  Gene mutations affect gene equilibrium by producing totally new alleles for a trait.
2. Migration – the movement of individual organisms into or out of a population affects allele frequency.  The movement of genes into or out of a population through migration is called gene flow.
3. Genetic Drift – the phenomenon by which allele frequencies in a population change as a result of random events or chance.  All examples of genetic drift occur in small to medium size populations, which are susceptible to non-random mating.

Evidence of Common Ancestry:

1. Homologous Structures –structures that are embryologically similar, but have different functions.  Animals with homologous structures suggest that these animals evolved from a common ancestor.
2. Vestigial Organs – functionless structure that may be homologous to useful structures in other species which may be viewed as evidence for evolution: organisms having vestigial structures probably share a common ancestry with organisms in which the homologous structure is functional.
3. Biochemistry – similarities based on the same biochemical compounds.
4. Embryonic Development – similarities in early embryonic structures

Hardy-Weinberg Law – states that in a large population in which random mating occurs and in the absence of forces that change the proportions of alleles, the original ration of dominant alleles to recessive alleles will be retained from generation to generation.  The Hardy-Weinberg Law can viewed as predicting a state of “genetic equilibrium.”  The frequency of the dominant allele (p) plus the frequency of the recessive allele (q) must together equal the frequency of the whole, (p + q  = 1).  Calculating the relative proportions of alleles where the frequency of allele  “A” is p and the frequency of  “a” is q then:            p² + 2pq + q²  = 1

The Hardy Weinberg Law states that a population will remain in genetic equilibrium if and only if:            

1. Individuals neither leave nor enter the population through migration
2. The population is large
3. no mutations occur
4. Individuals mate randomly

  Factors Affecting the Harvey-Weinberg Law:

1. population size – small populations skew the statistic because an allele can easily be lost.
2. migration – individuals with a particular characteristic in a different proportion than that of the remaining or existing population may enter or leave a population, skewing the statistics.
3. mutation – if an allele of a particular gene is mutating at a rate higher than that at which the reverse mutation is occurring, the statistics will be skewed.  Mutations are the basis for variability in populations