Evolution

Classified in Biology

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Evolution- a change in a population over time (results in new organisms or extinction)

Homologous structures- similar structure in two organisms that show they have a common ancestor

Jean Baptiste Lamarck

Hypothesis-

1.Organisms strive to improve themselves

2.Inheritance of acquired characteristics

-He thought children of blacksmiths naturally inherited muscles.

-If an organism lost or acquired a particular trait during its lifetime, it could be passed to its offspring.

3.Use and disuse

-Body parts that were used were developed, and those that were not used were wasted away.

-Lamarck's hypotheses were proved wrong by August Weismann, who cut off the tails of mice and recorded how their children were not born tailless.

Charles Darwin-

-Traveled on the H.M.S. Beagle to the Galapagos Islands and observed life there.

-He noticed how finches on different islands had different beak sizes.

Points of Natural Selection-

1.Populations have variations.

-Variations caused by recombination, mutation, sexual reproduction

2.Some variations are favorable.

3.More offspring are produced than survive.

4.Those that survive have the favorable trait.

5.The population will change over time and all will have the favorable trait.

Natural Selection & Evolution- natural selection causes evolution

-When the environment changes, some organisms are more prepared than others, so they survive (natural selection), and the population evolves to the more prepared (evolution).

-Antibiotic resistance illustrates natural selection because bacteria that can resist antibiotics will survive (bacteria are a good model because they grow fast).


Selection Graphs

Stabilizing


The intermediate is selected for and the extremes are selected against.

Directional


One extreme is selected for and the other extreme is selected against.

Disruptive


The extremes are selected for and the intermediate is selected against.


Genetic Equilibrium-

-When a population becomes stable, it reaches genetic equilibrium.

-Four (five) conditions are required for a population to reach genetic equilibrium.

1.Random mating.

2.Large population.

3.No mutations.

4.No immigration/emigration.

5.(No natural selection.)

Speciation

Species- breed and produce viable and fertile offspring

Reproductive Isolation

Behavioral Isolation-

-Populations can’t reproduce because of different mating rituals.

Geographical Isolation-

-Populations can’t reproduce because they are physically separated.

Temporal Isolation-

-Populations can’t reproduce because they have different reproduction times.

Patterns of Evolution

1.Extinction- every member of a species dies and can no longer reproduce

-Extinction is caused by natural selection.

2.Adaptive radiation- one common species evolves into many diverse life forms

3.Convergent evolution- animals with different ancestors look alike because of their environment

4.Coevolution- closely connected organisms will evolve together

5.Gradualism- organisms change gradually over time steadily and constantly

6.Punctuated equilibrium- there are random rapid changes in a species over a short amount of time

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Evolution