Evolution Vocab Review

Darwin was the first scientist to publish the idea that 1)___________ _____________ could account for evolution of populations. He proposed that populations 2)______________ offspring beyond what can survive in the environment. Within this population there are differences called 3)________________. Because there are more individuals than the environment can hold, there is a 4)_________________ for resources. Individuals of the population that are most suited to the environment 5)__________________. They are therefore chosen by the environment and have the opportunity to 6)____________________ and pass on their successful traits. As the environment changes, populations with the least variation are more likely to go 7)________________. As variation increases in a population, so does that population's chances of survival. Without variation, 8)________________ (or change) is not possible.

There are three things that increase a populations variation and create the bell curve of trait frequencies:

9)_______________ are genetic mistakes that change dna and chromosomes.

10)___________________ reproduction results in endless shuffling of genetic material so that the recombining of the chromosomes in the zygote produce an individual different from either parent.

11)________________ is the moving of individuals from one population to another and bringing of new genes to the new population.

Once variation exists in the population, the environment can act on the population to cause evolution in 3 ways.

12)______________ selection is when the bell curve of trait frequencies moves to one extreme. For instance, a redtailed hawk population's vision has continued to get more sharp over the last 10,000 years as the ones with the best eye sight are 13)_______ likely to hunt successfully and the ones with poor eyesight starve.

14)_____________ selection occurs when extremes of the bell curve are eliminated and the middle survives. This happens when cottontail rabbits with longer legs are 15)______ likely to survive because they cannot easily dive into thickets. Cottontails with shorter legs are 16)______ likely to survive because they are too slow. Cottontails with average sized legs are 17)_____ likely to survive because they can run fast enough, cut sharp enough, and dive into brush piles when being chased by predators such as coyotes.

18)_____________ selection occurs when the middle of the bell curve is eliminated. This happens to clams when predators such as starfish prey on them. Clams that are very small are 19)______ likely to survive because starfish will not bother with them. Clams that are very large are 20)_____ likely to survive because they are stronger and can survive starfish attempts to open them. Clams that are medium sized are 21)_____ likely to survive because they are just right for starfish to open and eat.

Natural selection can produce rapid results when populations are isolated and cannot share their genetic changes with the other populations. If this occurs because of mountain ranges or on islands, it is called 22)__________________ isolation. If it occurs because of changes in mating rituals, other behaviors, odors, size, color, or shape of the organisms, it is 23)_______________________isolation.

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natural selection