AP Bio Unit 7 Topics 1-5 & 12

No dimples (D) is dominant to dimples (d). If there are 350 people with no dimples in a population of 500 people: What is the predicted frequency of heterozygotes? What is the predicted frequency of homozygous dominant? What is the predicted frequency of homozygous recessive?

49.5% 20.5% 30%

How did artificial selection influence Darwin's thinking?

Darwin compared natural selection to artificial selection to help prove his research on natural selection to other scientists.

Why is evolution a theory?

Evolution is a theory because it is an explanation of a natural phenomenon that is largely supported by scientific evidence.

What factors contribute to phenotypic variation in a population?

Factors that can contribute to phenotypic variation in a population can be genetic variation, different environmental effects on individuals, microevolution, and interaction between individuals in a population.

True or false: natural selection acts on genotypes.

False; Acts on phenotypes.

True or false: organisms can adapt to their environments if they try to.

False; Adaptability is random, not an acquired skill.

How does species diversity correlate to the survival of the species?

Genetic diversity leads to a species having greater stability. The species is less at risk of catastrophic events, unhealthy mutations, and other stresses when it is genetically diverse.

Why is genetic variation important to survival?

Genetic variation is important to survival because it enables natural selection which is the primary cause of evolution. Variation of genes in a gene pool is healthy because it leads to greater stability in a population.

What is the difference between genotype frequencies and phenotype frequencies in a population?

Genotypic frequencies distinguish between the actual genetic makeup of an individual such as homozygous dominant, heterozygous, and homozygous recessive. Phenotype frequencies distinguish between physical characteristics such as long hair (dominant), and short hair (recessive).

If a new disease were to be introduced into the cheetah population, what effect could it have? Why? Be specific.

If a new disease were introduced to the cheetah population it would wipe out the species. Since this population has almost zero genetic diversity there is no way the species would survive the disease because no one cheetah would have adapted differently to help fitness.

Research an example of natural selection and identify the selective pressure.

In a dense rainforest, plants on the forest floor reproduce best if they are able to gather the most amount of light they can. These plants can do this by having larger leaves. The selective pressure in this example of natural selection is light availability.

Organisms of the same species with different genotypes will always have different phenotypes. Do you agree with this statement? Why or why not?

No, I do not agree with this statement because if a trait is dominant the homozygous dominant, and heterozygous genotypes will display that dominant phenotype.

Natural selection only does what is best for the species. Do you agree with this statement? Why or why not?

No, I do not agree with this statement because natural selection is entirely random. Just because a trait is good for survival does not mean it is good for the species. An example would be an over-adaption of a predator that eats all of the prey.

Is the Hardy-Weinberg model realistic?

No, the HW model is not realistic because in real populations allele and genotype frequencies vary over time. It is not realistic because no microevolution can occur.

What does the phrase "non-selective pressures" mean?

Non-selective pressures are all the pressures in an organism's environment that do not impact the gene pool.

How is sexual selection similar to directional selection?

Oftentimes female organisms are attracted to the flashy characteristics of male organisms when looking for a mate. This is similar to directional selection because the females are selecting a partner based on extreme traits.

Research an endangered species of your choosing. Identify the species chosen. How many individuals are currently living? What caused the species to become endangered? How does the low number affect the species' genetic diversity? Why are species with low numbers at a higher risk of going extinct? Think back to the review question about cheetahs. How does genetic diversity affect the ability of a species to survive environmental pressures (like the introduction of a new disease into the population)?

Red Panda 10,000 Habitat loss/degradation, human interference, and poaching. The very low genetic diversity leads to the red pandas' population carrying a high level of potentially unhealthy mutations. The lower numbers a species has can lead to reduced genetic diversity and greater susceptibility to catastrophic events. The more diverse the gene pool a species has, the better its chances of resisting disease, prevailing over other stresses, and adapting to changing conditions.

Research the bottleneck effect on cheetahs. What has happened to their population? How has this affected their genetic diversity?

The Cheetah population has depleted due to human interaction in the form of poaching, illegal pet trade, and habitat disruption. According to scientists, cheetahs were the organism with some of the worst genetic variation. Their genetic diversity heavily decreased because most alleles have become fixed.

What are the five conditions that must be met for a population to be in Hardy-Weinberg equilibrium?

The five conditions that must be met for a population to be in HW equilibrium are random mating, no mutations, no natural selection, an extremely large population size, and no gene flow.

What is the purpose of calculating Hardy- Weinberg equilibrium?

The purpose of calculating HW equilibrium is to determine if the population is experiencing microevolution (criteria not met) or if it is truly just mendelian genetics and recombination (criteria met).

White fur color (w) is recessive to black fur color (W) in mice. 22 mice have a white coat in a population of 200. Knowing this, calculate the frequency of the r allele.

The recessive allele's frequency is 33.16%.

The frequency of individuals who express a recessive disease in a population is 5%. What variable in the Hardy-Weinberg equations does the 5% refer to? Why?

This 5% would refer to the variable q^2 in the HW equations. It would refer to variable q^2 because that variable represents the percentage of homozygous recessive individuals.

How is our general understanding of the phrase "survival of the fittest" misleading?

This phrase is misleading because survival is only one part of natural selection, and it is not always the most important. Reproduction is often the more important aspect of natural selection.

True or false: mutations can lead to new alleles.

True

How does artificial selection differ from natural selection?

With natural selection, nature selects traits that are best suited for survival and reproduction, while with artificial selection humans select desirable traits.

Can an organism's physical environment influence evolutionary change? Why or why not?

Yes, selective pressures are these external agents that influence an organism's evolutionary change in a given environment.

Population

a group of individuals of the same species that live in the same area and interbreed to produce fertile offspring

Gene Pool

a population's genetic makeup; consists of all copies of every type of allele

Natural Selection

a process in which individuals that have certain traits tend to survive and reproduce at higher rates than other individuals because of those traits

Sexual Selection

a type of natural selection that explains why many species have unique/showy traits; males often have useless structures (ie colorful male peacock feathers) simply because females choose that trait; can produce traits that are harmful to survival

Genetic Drift

chance events that cause a change in allele frequency from one generation to the next

Evolution

change in the genetic makeup of a population over time; descent with modification

Mutation

changes in the genetic material of a cell that alter phenotypes; the primary source of genetic variation (large scale: chromosomal changes, small scale: nucleotide substitutions, insertions, or deletions)

Descent with Modification

evolution; the idea that species change over time, give rise to new species, and share a common ancestor

Selective Pressures

external agents which affect an organism's ability to survive in a given environment

Fixed

if there is only one allele present for a particular locus in the population; many fixed alleles = less genetic diversity

Adaptations

inherited characteristics of organisms that enhance their survival and reproduction

Competition

limited resources, which results in differential survival

Biotic Factors

living things within an ecosystem

Hardy-Weinberg Equilibrium

no mutations, random mating, no natural selection, extremely large population size, no gene flow, If any of these conditions are not met, then microevolution occurs (i.e. mutation, gene flow, genetic drift, natural selection, and non-random mating)

Abiotic Factors

nonliving components in an ecosystem

Fill in the blank: Evolutionary fitness is measured by ________ success.

reproductive

Disruptive Selection

selection against the mean; both phenotypic extremes have the highest relative fitness

Directional Selection

selection towards one extreme phenotype

Stabilizing Selection

selection towards the mean and against the extreme phenotypes

Fill in the blank: If an organism has a more favorable trait, then it will be more likely to ______ and _______.

service and reproduce

Fitness

the ability to survive and reproduce; measured by reproductive success

Genotype

the genetic makeup of an organism; describes an organism's complete set of genes

Biogeography

the geographic distribution of species

Phenotype

the observable characteristics in an individual resulting from the expression of genes

Artificial Selection

the selective breeding of domesticated plants and animals to encourage the occurrence of desirable traits

Differential Survival

the traits that lead to survival ("favorable" traits) will accumulate in the population

Gene Flow

the transfer of alleles into or out of a population due to fertile individuals or gametes; alleles can be transferred between populations

Founder Effect

when a few individuals become isolated from a large population and establish a new small population with a gene pool that differs from the large population; lose genetic diversity

Bottleneck Effect

when a large population is drastically reduced by a non-selective disaster; some alleles may become overrepresented, underrepresented, or absent