BIOA02H3 Chapter Notes - Chapter 22: Stabilizing Selection, Gene Flow, Selective Breeding
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BIOA02H3 Full Course Notes
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Some amphibians have evolved chemical defence against predation, becoming poisonous. Tetrodotoxin (ttx) is a neurotoxin that paralyzes nerves and muscles by blocking sodium channels. Some snakes have ttx-resistant sodium channels in nerves and muscles. Ttx-resistant snakes move slowly than ttx non-resistant snake after eating a newt. More vulnerable to their own predators than are ttx-sensitive snakes. Production and resistance to defensive chemicals are evolutionary adaptations. Improvement of performance in one area is reduced performance in some other area, known as trade-off. Darwin found that species were more similar in regions close together than regions that have the same climate. Species on the island were not found in anywhere else, but similar to the surrounding main lands. Proposed explanatory theory for evolutionary change: species are not immutable, they change over time, process that produces these changes is natural selection. Populations of all species have the potential for rapid increase in numbers, but death rate is also high in nature.
