There are multiple types of natural selection; stabling, directional and disruptive. Stabling selection favors the Intermediate variants. Directional selection shifts the overall makeup of the population by acting against Individuals at one of the extremes. Disruptive Selection favors individuals at both extremes. Evolution occurs in different rates, one, Gradualism is when change occurs slowly but continuous, and two, by punctuated equilibrium when populations experience little change and when speciation occurs, it’s rapid.
Another key part in evolution is miscalculation (evolution that focuses on change at or above the level of species). Which leads to speciation… Here are ways a species are formed, there’s allophonic where speciation occurs because of a geographic barrier so there is no gene flow (when a population gains or loses alleles by breeding with individuals from another population). There’s symmetric speciation where species arise without geographic separation. Adaptive radiation shows that surviving individuals adapt to a new environment.
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The protocol barriers prevent fertilization between species. There are five Isolations: Temporal, Habitat, Behavioral, Mechanical and Genetic. Temporal occurs when two species breed at different times. Habitat occurs when two species live in the same general area but not in the same kind of places, ex. Garner snakes. Behavioral, there is little or no sexual attraction between male and female individuals of different species. Mechanical occurs when a female and male sex organs are not compatible.
Lastly, genetic occurs when a male and female from two species may breed, but the gametes do not form a zygote. Posthypnotic barriers operate after hybrid zygotes are formed. Some cases there is hybrid inability where the hybrids don’t survive. On the contrary, there Is hybrid sterility where the hybrids do survive, but they cannot reduce offspring.. Ex. Mules. There’s also hybrid breakdown. This is where the first couple generations are fertile, but when they start to breed with other hybrids or parent species, the offspring become sterile.
B. (1) Scientists can use bacterial resistance to antibodies as evidence for evolution because It shows that the bacteria used in the antibodies, and therefore that immune individual can reproduce more and more until that bacteria is immune to the antibody. (2) Scientists can use comparative biochemistry as evidence for evolution because it compares the molarities in different species that are signs that those species evolved from a common ancestor, known as homology.
For example, bats, cats, whales, and humans all have similar forelimbs. They may differ in functions, but are homologous structures. (3) Scientists can use the fossil record as evidence for evolution because fossils are left behind in layers of sedimentary rock. So as you move from the bottom layer of the rock (the oldest part) you can gradually see changes in species from over time. Ex. Amphibians appear after fish, mammals appear after reptiles.