Evolution Flash Cards

3 important elements to an organism's fitness 322

1. An individual's fitness is measured relative to other genotypes or phenotypes in the population. 2. Fitness depends on the specific environment in which the organism lives. 3. Fitness depends on an organism's reproductive success compared with other organisms in the population.

Four ways in which evolution can occur. 310

1. Mutation 2. Genetic Drift 3. Migration 4. Natural Selection

According to Charles Darwin, what are the 3 conditions that are necessary for natural selection to occur?

1. There must be variation for the trait within a population 2. That variation must be heritable (that is, capable of being passed from parents to offspring). 3. Individuals with one version of the trait must produce more offspring than those with a different version of the trait.

What did Darwin noticed 2 important and unexpected patterns on his voyage? 306

1. Traits exhibited by species 2. Throughout his voyage, at every location there was a striking similarity between the fossils of extinct species and the living species in that same area.

Define Disruptive Selection 327

3rd kind of Natural Selection in which individuals with extreme phenotypes experience the highest fitness, and those with intermediate phenotypes have the lowest.

Define Natural Selection 310

A change in allele frequencies that occurs when individuals with one version of a heritable trait have greater reproductive success than individuals with a different version of the trait.

Define Evolution 302

A genetic change in the population of an organism.

What is the term "population" in biology? 300

A group of organisms of the same species living in a particular geographic region.

Natural Selection 324

A process by which, in each generation, the alleles that cause organisms to have the traits that make them most fit in that environment tend to increase in frequency. If the environment changes, the alleles that are most favored may change too.

Define Genetic Drift 313

A random change in allele frequencies in a population. Unrelated to the alleles influence on reproductive success A significant cause of evolutionary change Primarily in small population

Define Genetic Drift 310

A random change in allele frequencies, unrelated to any allele's influence on reproductive success.

Define Bottleneck 314

A rapid environmental change causes the deaths of a large proportion of individuals in a population.

What is the evidence that natural selection can cause evolution of complex traits and behaviors? 329

An experiment in 1954, in which rats was put in maze. The experimenter bred the fastest mouse to escape with another fastest mouse. And the slowest mouse with the slowest. As a result, after generations, the experimenter found that the mouse that was bred from faster parents are more likely to finish the maze easily than the other.

Convergent Evolution 336

Analogous structures all developed from different original structures.

Why do trait does not decrease in frequency? 320

Because it is inactive.

Why is the fossil record a very incomplete record? 331

Because parts of an organism tend to decay rapidly and completely after death, but bones teeth and shells can be preserved for thousands or even millions of years.

Why is Artificial Selection is considered a special case of natural selection? 326

Because the differential reproductive success is being determined by humans rather than by nature. Example: Apple growers, use artificial selection to produce the wide variety available. What is important is that it is still differential reproductive success, and the results are no different.

What is important to remember regarding evolution by natural selection? 329

Changing the allele frequencies for traits, whenever: 1. There is a variation for the trait 2. That variation is heritable 3. There is differential reproductive success based on that trait.

Why is it that all organisms of populations will never be perfectly adapted to their environment? 324

Example, beak size of Galapagos finches. Over the course of a multi-decade study, biologists closely monitored the average size of the finches' beaks. During dry years when the finches had to eat large, hard seeds, bigger and stronger beaks become the norm. During the wet years, smaller-beaked birds were more successful, since there was a surplus of small soft seeds.

Define Founder effect 314

Founder effect is the loss of genetic variation that occurs when a new population is established by a very small number of individuals from a larger population. Lecture: Small number of individuals become the founding members of a new, isolated population. Founders may have different allele frequencies than original population. Particularly if they are a small sample

What does organism have in similarity in terms of genetic code? 337

Four simple bases, arranged in an almost unlimited variety of sequences. In short, all living organisms share the same genetic code.

What is another name for Migration? 315

Gene Flow

Gene Flow or Migration in detail 316

If migrating individuals survive and reproduce in the new population, and if they carry a different proportion of alleles than the individuals in their new home, then the recipient population experience a change in allele frequencies and, consequently, experiences evolution. and because alleles are simultaneously lost from the population, too, will experience a change in its allele frequencies and, thus, will evolve.

Laboratory and fields studies 331

Implementation of the scientific method to observe and study evolutionary mechanisms

Define Directional Selection 326

In Directional Selection, individuals with one extreme of the range of variation in the population have higher fitness. Milk production in cows is an example. There is a lot of variation in milk production from cow to cow. As you might expect, farmers select for breeding those cow with the highest milk production and have done so for many decades. The result of such selection is not surprising: it increased the milk production by 50% between 1920s and 1945.

What is Differential Reproductive Success? 319

Individuals with the version of a trait most suited to reproduction in their environment generally leave more offspring than individuals with other versions of the trait. Example: In the fruit fly experiment, we saw that the flies that inherit the ability to pack on fat when food is available end up leaving more offspring than those inheriting a poor ability to pad their little fruit fly frames with fat deposits. The portly fruit flies have greater reproductive success than other individuals in the population.

What is Artificial Selection 326

Is the process by which humans breed other animals and plants for particular traits.

How can mutation occur? 311

It can be induced by a variety of environmental factors including: 1. Radiation 2. Chemical

What can Fossils provide to us? 331

It can be used to reconstruct what organisms must have looked like long ago.

What is Fixation? and how does it occur? 313

It occurs when an allele's frequency in a population reaches 100% (and the frequency of all other alleles of that gene becomes 0%) If this occurs, there is no longer genetic variation for the gene.

Define Stabilizing Selection 327

Occurs when individuals with intermediate phenotypes are the most fit. Example: Death rate of babies is lowest between 7 and 8 pounds, increasing for both lighter and heavier babies. This outcome has kept the average weight if a baby constant over many generations; but at the same time, the variation in birth weight has decreased as stabilizing selection has reduced the frequencies of genes associated with high and low birth weights.

Biogeography 331

Patterns in the geographic distribution of living organisms

Define Adaptation 323

Refers both to the process by which organisms become better matched to their environment and to the specific features that make an organism more fit. Example: Bats have an extremely accurate type of hearing for navigating and finding food, even in complete darkness Porcupine quills make porcupines almost impervious to predation. Mosquitoes produce strong chemicals that prevent blood from clotting, so that they can extract blood from other animals.

Q> Why doesn't natural selection lead to perfect organism? 325

Several Factors: 1. Environment change quickly. Natural selection may be too slow to adapt the organisms in a population to such a constantly moving target. 2. Variation is needed as the raw material of selection - remember, it is the first necessary condition for natural selection to occur. If a mountain creating a new, "perfect" version of a gene never occurs, the individuals within a population will never be perfectly adapted. 3. There may be a different alleles for a trait, each causing individuals to have the same fitness. In this case, each allele represents an equally fit "solution" to the environmental challenges.

What does molecular biology reveal in terms of evolution? (Fourth line of evidence) 336

That common genetic sequences link all life forms.

What did the fossil led to conclusion in Cuvier? 303

That extinction was a fact.

What is the important factor that distinguishes genetic drift from natural selection? 313

The change in allele frequencies is not related to the allele's influence on reproductive success. A cleft chin does not affect an individual's ability to reproduce.

Sometimes, homologous structures come to have little or no function at all. What do you call this evolutionary leftovers? 336

Vestigial Structures.

Can Natural selection change the traits in a population? 326

Yes, Natural selection can change the traits in a population in several ways.