Unit 10.3 Theory of Natural Selection – Flashcards

The process by which humans change a species by breeding it for certain traits.

Yes

The trait must be heritable.

It is the ability of a trait to be passed down from one generation to the next. (Break down Heritability into Heredity and Ability.)

Humans

The Enivironment

A mechanism by which individuals that have inherited beneficial adaptations show differential reproductive success. In other words- they tend to produce more offspring on average than do other individuals.

They are selected by the environment, through process of evolution and by adaptation, such that resulting in characteristics that only give advantages to the organisms getting the trait to help them survive (relate to slogan: Survival of the Fittest).

No, *Remember that *desirable* traits are only found in Selective Breading, and *advantageous* traits are generally found in Natural Breading.

Thomas Malthus (Relate to HGAP)

It is all of the individuals of a species that live in an area.

Descent with modification is the term Darwin used for evolution. It explains both the unity of life and the diversity of life. The unity of life comes from descent; offspring resemble their parents, even over many generations. But organisms are not identical to their parents, they are also modified in the process; and this - over long periods of time - explains the diversity of life. So for example, the homology between the forelimbs of a human, a bat, a porpoise, and a horse are explained by descent with modification. They have the same pattern of bones because all of those animals descended from a common ancestor, but the bones are not identical because they were modified for different functions -- grasping, flight, swimming, and running.

Alfred Russel Wallace

1. Variation 2. Overproduction 3. Adaptation 4. Descent with Modification

The heritable differences, or variations, that exist in every population are the basis for natural selection. The differences among individuals result from differences in the genetic material of the organisms, whether inherited from a parent or resulting from genetic mutation.

While having many offspring raises the chance that some will survive, it ALSO results in competition between offspring for resources.

A certain variation that allows an organism to survive better than other organisms it competes against in its environment. More successful individuals are "naturally selected" to live longer and to produce more offspring that share those adaptations for their environment.

Think of this as when organisms get "modified"/get a variation and they remain "descent" with the variation. Natural Selection will result in species with adaptation that are well suited for survival and reproduction in their environment. Most individuals will have the trait in every following generation, as long as environmental conditions continue to remain beneficial for that trait.

A measure of the ability to survive and produce more offspring relative to other members of the population in a given environment.

Natural Selection acts on the Phenotype (physical traits).

They are made by genetic mutations, NOT by natural selection.

No, Natural Selection can act ONLY on traits that already exist. In other words, Natural Selection acts only on existing variation.

Yes, as Ecologists Peter and Rosemary Grants discovered when they observed the affects of a drought in 1977 in the Galapagos Islands on finches with large and small beaks. The finches with the large beaks survived whereas the finches with small beaks didn't. And so, the trait gets passed down. *In this case it was a change in the environment.* This caused the large beak finches population to sour. However, an unusually wet period caused the supply of large seeds to go down. On the contrary, these conditions favored the production of small,soft seeds and small beaked birds. And this caused this caused the small beak finches population to rise. Remember: that a trait that is an advantage today may be a disadvantage in the future.

He wanted to learn whether you can possibly change the whole species following that specific pigeon into a new species of pigeon.

Because if there is no variation, there is no survival of the fittest. if all organisms are the same, it makes no difference which ones are killed, the gene pool stays the same. If there is variance, only the organisms with better genes survive and the inferior ones are killed off.

Its because the phenotype or physical characteristics is what actually determines if the organism is able to reproduce and pass along its genotype to the next generation. Natural selection acts on the phenotype of the organism because the phenotype represents the alleles that are actually expressed in an organism. If an allele is not expressed (part of the phenotype) it can not be selected for or against. If there is a trait that is controlled by a recessive allele, then there can be normal individuals that don't have the allele at all (NN), as well as normal individuals that don't have the trait but do carry the allele for the trait (Nn). Natural selection will treat these two phenotypes the same, even though their genotypes are different. The genotype, or the genetic makeup of an organism , is what is responsible for the phenotype or the look of the organism. So, the genotype must be changed for the phenotype to be changed, unless the organism had an injury. The phenotype of the organism is the physical characteristics that is displays rather on what two alleles it has for that characteristic. Nature selects the best suited organisms to survive so it does not matter what the genotype is, only the phenotype. For instance if color blindness is recessive to normal vision and a color blind person would be selected against a person being color blind would not survive. That is a person with the genotype cc. Now a person who is not color blind would be selected for and would survive. This person could have the genotype CC or Cc. You can see that nature does not select in this case based on what genes the organisms has but rather what physical traits is possesses.