Evolution of Populations Summary
A. Issues in Biology (P.403)
Natural selection is happening in antibiotic's bacteria resistance, drugs that are specifically intended to kill bacteria are evolving. Bacteria population had a few individuals with strong traits that defeated and resisted antibiotics. As the time passed, evolution occurred and these individuals reproduced, now antibiotics are practically useless in certain cases. Some people think antibiotics should be restricted but doctors love to use them in humans because there is a high demand. They will not change their practice unless forced to do so.
B. Isolating Mechanisms (P.404)
Individuals that are in the same species share a common gene pool. Therefore, if a genetic change increases the allele will be found in a lot of individuals of that specie or population. In order for the gene pools of two population to become new species they need to become separated. Populations become reproductively isolated from eachother in other words, when members of two populations cannnot interbreed and get fertile offspring it is called reproductive isolation.
VARIETY WAYS OF REPRODUCTIVE ISOLATION
VARIETY WAYS OF REPRODUCTIVE ISOLATION
- Behavioral Isolation
- Geographic Isolation
- Temporal Isolation
Behavioral Isolation
Behavioral Isolation is basically when two individuals of populations are able to interbreed but have different ways of attracting strategies or rituals that have to do with behavior. For example, when birds don't get attracted to members of other specie because they use different songs to attract.
Geographic Isolation
Geographic Isolation occurs when two populations are separated by geographical barriers like rivers, lakes, mountains or bodies of water. Certain types of organism may separate by the power of these barriers but some don't get separated. For example, birds are species that don't get affected because they fly.
Temporal Isolation
Temporal Isolation is when two or more species reproduce at different times. A good example, species that are similar of orchid in a rain forest release pollen only once a day. All species release pollen at different times of the day so they can't pollinate.
C. Testing Natural Selection in Nature (P.406)
The mechanisms of evolutionary change can be observed in nature. Darwin observed in the Galapagos Islands finches; those finches looked really different from each other that when Darwin saw them he didn’t realize they were finches. Once he discovered all this birds were finches, his hypothesis said that they had descended from a common ancestor. He proposed natural selection shaped the beaks of different bird population as they adapted to eat different foods. The work of Peter and Rosemary Grant from Princeton University realized that Darwin’s hypothesis relied on two testable assumptions. First, in order for beak size and shape to evolve, there must be enough heritable variation in those traits to provide raw material for natural selection. Second, differences in beak size and shape must produce differences in fitness that cause natural selection to occur.
Variation
The Grants first identified and measured as many individual birds as possible on the island. The data they recorded indicates that there is great variation of heritable traits among the Galapagos finches.
Natural Selection The Grants discovered that individual birds with different sized beaks had different chances of survival during a drought. When food for the finches was scarce, individuals with the largest beaks were more likely to survive. The Grants provided evidence of the process of evolution. The next generation of finches had larger beaks than the generation before.
Natural Selection The Grants discovered that individual birds with different sized beaks had different chances of survival during a drought. When food for the finches was scarce, individuals with the largest beaks were more likely to survive. The Grants provided evidence of the process of evolution. The next generation of finches had larger beaks than the generation before.