Biology evolution




Biology evolution


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Biology evolution


Topic 4.3 - Evolution

4.3.1 Define evolution.

  • Evolution is the process of cumulative change in the heritable characteristics of a population, the descent of modern organisms from preexisting life forms.

4.3.2 State that populations tend to produce more offspring than the environment can support.

  • Populations tend to produce more offspring than the environment can support.

4.3.3 Explain that the consequence of the potential overproduction of offspring is the struggle for survival.

  • The world has limited resources. Organisms produce many more offspring than can live off of these limited resources. Therefore, there is a struggle to survive between offspring. This allows for natural selection, because those best suited for thier environment survive and pass on thier better-suited genes.

4.3.4 State that the members of a species show variation.

  • The members of a species show variation.


4.3.6 Explain how natural selection leads to the increased reproduction of individuals with favorable heritable variations

  • Combining the ideas of the struggle to survive, and the great variation in organisms, we can see that a group of different organisms are all fighting to occupy a certain niche (a place in the ecosystem). If organism A is better suited for this environment than organism B, organism A will survive and reproduce more than organism B. It is very important to understand that longer life is not a "goal" of natural selection. An organism that is better suited to an environment will be able to reproduce and pass on thier superior genes. The ability of better sutied organisms to reproduce more than other organisms that are not as suited for thier environment allows for the better suited organisms to produce more organisms with those same genes. These organisms have inherited the superior genes, so the amount of organisms with superior genes has increased.

4.3.7 Discuss the theory that species evolve by natural selection

  • In order to answer this question, the ideas aforementioned should be used.
  • If more organisms are produced that have "superior" genes, genes that make the organisms more suited for their environment, then they are able to produce more organisms with superior genes. This causes the population become more and more made of these superior organisms. When a population of a species changes as a result of natural selection, the species has evolved.

4.3.8 Explain two examples of evolution in response to environmental change; one must be multiple antibiotic resistance in bacteria

  • Example 1: Two varieties of the moth Biston betularia exist in the forms of different body color. One is black, the other is speckled. The black moth is easily seen by predators while the speckled one is camoulflaged. When on a tree covered in lichens, the peppered moth blends in very well. The number of speckled moths was greater than the number of black moths, because the speckled genes made the speckled moths more suitable for thier environment of lichenous trees. Because they were able to camouflage, they could evade predators more than black moths could, which allowed them to reproduce more moths with the genes for speckled color. Then, the trees began to get covered in suit due to the industrialization, and the black moth was able to be more camouflaged than the speckled moths. Because of this more black moths than speckled moths evaded predators, allowing them to produce more black moths. So the population of black moths then increased and the speckled moth population decreased.

    Example 2: Resistance to antibiotics in bacteria. If a culture of bacteria is sprayed with antibiotics, most of the bacteria is killed. A small number that naturally have genes resistant to antibiotics, will remain. It is important to note that these bacteria did not "learn" to resist antibiotics. These bacteria has mutated genes that somehow allowed them to resist antibiotics. These bacteria will reproduce and pass on thier resistant genes. Natural selection chose the antibiotic resistant ones, so those are the only ones to exist. This can become a problem when trying to kill a bacterial infection in a patient, because if the bacteria is resistant to the antibiotics given, then they can't be killed. Someone would have to come up with a new antibiotic that it is not resistant to, which can be difficult.

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Biology evolution