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Macroevolution is the formation of a new species.

Microevolution is the gradual change in allele frequency within a population. (resistance to a particular substance in one specie)





Natural selection: when characteristics of a population change because individuals with certain inherited traits survive specific local environment conditions and pass down those traits to their offspring. 


Selective advantage: when a mutation enables an organism to survive in its environment better. Mutations that once were a disadvantage could become an advantage. A trait that is beneficial in one environment may be harmful in another.


Selective pressure: Selective pressure refers to any factor in the environment that influences the survival and reproduction of individuals with certain traits, leading to changes in the frequency of those traits within a population over time.



Artificial selection: It is used to produce a particular plant or animal variety that expresses a desirable trait. Ex: breeding dogs, horses… (it may select for unhealthy traits as well as desirable ones.





A mutation can cause a variation in a population. It can also cause natural selection. If the trait is beneficial it is more likely to be passed on to the next generation and overtime create a population where the common trait is the original mutation.





A variation is a visible or invisible difference among some members of a population. It can be an advantage, a disadvantage or have no effect on an individual. These variations occur through sexual reproduction and crossing over or through mutations. A variation can become an adaptation if it is an advantage towards the organism, this variation will become more common within a population and will eventually become an adaptation.





Plato and Aristotle: Life existed in a perfect and unchanged form. 


LeClerc: Noted similarities between humans and apes, speculated about common ancestor.

Suggested that earth was older than 6000 years old.


Mary Anning: Discovered remains of a prehistoric fish that did not live during her time. Her discoveries led people to question if all forms of life came to existence at the same time.


Cuvier: Considered the father of paleontology. Discovered that each layer of rock is characterized by a unique group of fossil species. The older the layer, the more dissimilar the species were. He believed in CATASTROPHISM, the idea that catastrophic events were violent enough to have killed numerous species each time they occured. 


Charles Lyell: UNIFORMITARIANISM, states that geological processes operate at the same rate today as they always did. Suggested that the Earth was millions of years old. Slow, subtle processes could happen over a long period of time and result in substantial changes.


Lamark: He believed in the inheritance of acquired characteristics. (not true)


Darwin: He developed the theory of evolution by natural selection.


Russel Wallace: Independently reached conclusions similar to darwins. 


Malthus: supply and demand in population.




● Fossil evidence:


  • Index fossils: Indicate the approximate age of the rock in which they are found.

  • Radiometric dating: Uses measurements of certain radioactive isotopes to calculate the absolute age in years of rocks and minerals.

  • Transitional fossils: Show intermediary links between groups of organisms.


● Biogeography: Study of past and present geographical distribution of different types of organisms.


● Comparative anatomy:


  • Homologous structures: same origin, different function.


  •  Analogous structures: different origin, same function.


  •  Vestigial structures: were functional in ancestors but have no current function.


● Comparative embryology: Embryos of different groups of organisms show similar stages of embryonic development.


● Molecular Biology: how closely species are related by comparing sequences in amino acids, RNA, DNA or chromosomes as a whole.






Transition fossils are the ones that show intermediary links between groups of organisms, while index fossils indicate the approximate age of the rock in which they are found.




• Geographic barriers: Geographical elements that physically prevent interbreeding and result in speciation because they keep populations physically separated. 

• Biological barriers: Keep populations reproductively isolated.




Prezygotic:

• Behavioral isolation: species specific signals or behaviours prevent interbreeding with closely related species.


• Temporal isolation: timing barriers prevent species from interbreeding. Ex: diurnal or nocturnal…


• Mechanical isolation: closely related species have incompatible reproductive structures.


• Habitat isolation: Species live in same general area but use different habitats and rarely encounter each other.


• Gametic isolation: chemical marker on egg prevents egg and sperm from different species fusing to form zygote.





Post zygotic


▪ Hybrid inviability:  genetic incompatibility of interbred species. Stops development of hybrid zygote during development.


▪ Hybrid sterility: can mate and produce hybrid offspring,offspring is sterile.


▪ Hybrid breakdown: first generation hybrids mate and offspring ar either sterile or weak.




▪ Transformation: a new species results from accumulated changes within a population over time. Old species is gradually replaced.


▪ Divergence: one or more species arise from a parent species that continues to exist. The diversification of a common ancestral species into a variety of species that are differently adapted is called adaptive radiation.




• Co-evolution: when the evolution of one species depends on the evolution of the other. FActors that affect that species may indirectly affect another.


• Divergent evolution: Adaptive radiation is an example. Divergent evolution is a process where two or more related species become more dissimilar over time as they adapt to different environmental conditions or ecological niches.


• Convergent evolution: Convergent evolution is when unrelated species independently evolve similar traits due to similar environmental pressures.




• Gradualism: evolutions happens at a slow and steady pace with the accumulation of small gradual changes that result in large changes.


• Punctuated equilibrium: long periods of stasis interrupted by periods of rapid change.





• Know how to calculate genotypic, phenotypic and allelic frequencies.


CONDITIONS:

  1. Population is large enough that chance events will not alter allele frequencies.

  2. Mates are chosen on a random basis.

  3. No net mutations

  4. No migrations

  5. No natural selection against any phenotypes






• Gene flow: Gene flow refers to the transfer of genetic material, such as alleles or genes, between populations of the same species through interbreeding or migration.


• Mutations: An inheritable mutation can affect the entire gene pool. The more genetic variation, the greater the chance a variation will provide a selective advantage in changing the environment

.

• Non-random mating: unable to predict which males will mate with which females.

  •  Preferred phenotypes

  •  Inbreeding: closely related individuals breed together


• Genetic drift: change in allele frequencies in small breeding population due to chance events.

  • Founder effect: a few individuals start a new isolated population. Not much diversity.

  • Bottleneck effect: quick reductions in populations lead gene pool to lose diversity.


• Natural selection

  •  Directional selection: favors genotype on one extreme over the other.

  • Stabilizing selection: favors intermediate phenotype

  • Disruptive selection: favors extremes of a range of phenotypes.