lesson14.5-14.6[1].pptx, modern theory of....

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1. Lesson 14.5 Modern theory of evolution

2. Today, we know that the only way for traits to be passed on is through genes, which cannot be affected by the outside world Only the gene sets are affected and those are determined by which individuals die and which ones live.

3. Alteration to the genes in the germ cells--the cells that give rise to sperm and egg—produce inheritable variations. This rule first proposed by the G erman evolutionary biologist August Weismann in 1893. Weismann experimented on 901 mice; cut their tails and allow them to mate

4. August removed the tails of parent mice and let them breed. After 22 trials, an offspring had tails, a fact that supported the theory that acquired characteristics are not inherited.

5. Lesson 14.6 Development of new species

6. Gene flow refers to the movement of genes from one generation to the next, or one region to another Example: A male donkey can mate with a female horse to produce a mule However, a mule is sterile and therefore cannot facilitate gene flow between horse and donkey. Therefore, mules are considered as a different species altogether.