AP Bio Unit 7 - Natural Selection

What is natural selection?

adaptations will enhance an organism's ability to survive and reproduce in specific environments

How does natural selection lead to evolution?

the organisms that reproduce more due to their adaptations will have allele frequencies that are more common in the population due to more reproductive fitness

What is Darwin's theory of natural selection?

more variation in a population leads to different adaptations, those adaptations that are better suited for the environment are more likely to survive and reproduce causing descent with modification

What does differential survival mean?

some organisms are more likely to survive due to specific adaptations than others

Why do organisms require competition for limited resources to allow for natural selection?

limited resources mean that organisms that occupy the same niche or habitat will have to compete for resources and those that are better suited/adapted will outcompete the others for those resources and have a higher survival rate. they will be more likely to reproduce.

What is evolutionary fitness?

reproductive success

How is evolutionary fitness measured?

the organism's ability to survive and reproduce which will determine the size of its genetic contribution to the next generation

What is reproductive success?

an individual's production of offspring per breeding event or lifetime

How does reproductive success lead to natural selection?

the more often an individual reproduces, they contribute their genetic makeup to the next generation causing allele frequency changes in the next generation

What does biotic and abiotic mean?

biotic means living and abiotic means non living

How does a biotic environment affect the direction of evolution?

competition for food, organisms that can withstand certain diseases, etc. are more likely to survive and and reproduce and pass their traits on to the next generation

How does an abiotic environment affect the direction of evolution?

an organism's ability to withstand changes in climate

How does a biotic environment affect the rate of evolution?

The biotic environment, such as predation and competition for resources, would cause the population to evolve, but probably at a much slower rate than an abiotic factor, given that some organisms will be able to obtain resources in other manners.

How does an abiotic environment affect the rate of evolution?

Things like climate change could potentially make the population evolve much faster because those adapted to changing conditions would be able to survive and reproduce and pass on their traits to the next generation.

What is phenotype?

physical traits

What does natural selection act on? PHENOTYPE or GENOTYPE?

PHENOTYPE

What does natural selection modify? PHENOTYPE or GENOTYPE?

GENOTYPE

How does natural selection act on and modify different levels of genes?

Natural selection can cause microevolution on a small scale with fitness increasing alleles becoming more common in the population, but it can also act on traits that are determined by alternative alleles of a single gene or on polygenic traits.

What are selective pressures?

Interaction between natural variation in a species and factors in its environment that cause a certain form to have an advantage over the others.

How does an environment apply a selective pressure to a population?

Populations change because individuals in a population with a beneficial characteristic for a particular environment will survive and reproduce, increasing the frequency of that characteristic in the population

Identify two examples of a phenotypic variation that increases fitness of an organism in a particular environment.

Antibiotic resistance in bacteria

Rock Pocket mouse with lighter fur color living in sandy desert.

Identify two examples of a phenotypic variation that decreases fitness of an organism in a particular environment.

Sickle cell mutation in someone living in area without mosquitos carrying malaria

Rock Pocket mouse with lighter fur color living on dark lava rock

What is artificial selection?

identification by humans of desirable traits in plants and animals, and the steps taken to enhance and perpetuate those traits in future generations.

How does artificial selection modify the variation in a species?

Organisms with traits human value are chosen for breeding the next generation. Overtime those characteristics become more common in a population

Identify two examples of artificial selection due to humans. How has this modified the species?

dogs, agriculture

Wild mustard is the ancestor of broccoli, cauliflower, cabbage, brussel sprouts, and kale. These traits have all been artificially selected for by humans

What is convergent evolution?

distantly related species resemble one another

Identify two examples of organisms that demonstrate convergent evolution.

sugar glider/flying squirrel, bat/bird wings

How do selective pressures result in similar phenotypic adaptations?

similar environments/problems resulted in similar adaptations being better suited for their environment

What are mutations?

changes to the DNA sequence

Identify two examples of mutations that potentially could affect phenotype.

point mutations, chromosomal mutations

How do mutations affect genetic makeup of a population?

they introduce new alleles/genes into a population that can have new phenotypes

What is genetic drift?

unpredictable fluctuation of alleles from one generation to the next in small population sizes

What is the bottleneck effect?

severe drop in a population size

How does the bottleneck effect modify genetic makeup of a population?

the drop in population size causes certain alleles to be over/under represented in a population

Identify one example of a population that has undergone the bottleneck effect.

cheetahs

What is the founder's effect?

few individuals become isolated from the larger population

How does the founder's effect modify genetic makeup of a population?

whatever genotypes those individuals brought with them will cause certain alleles to be over/under represented in that population

Identify one example of a population that has undergone the founder's effect.

Amish population

What is gene flow?

population gaining/losing alleles due to migration

How does gene flow modify genetic makeup of a population?

new variations of genetic makeups can be brought into a population from another population

Identify one example of a population that has undergone gene flow.

mosquitoes resistant to DDT

What is genetic variation?

differences between individuals in their phenotypic and genotypic frequencies for a specific trait

Why is genetic variation important for a population's survivability?

it is advantageous to that population because it enables some individuals to adapt to the environment to help maintain the survival of the population.

How does a decrease in genetic variation affect a population?

the population may not be able to evolve in response to changing environmental variables and may face increased risk of extinction

When there is a decrease in genetic variation, how does the population compare to other populations of the same species?

they have a decreased chance of survival because of their lack of variation and adaptation ability

What is the effect of mutations on genetic variation?

only source of new genes and new alleles in the population

How does genetic variation lead to a variation in phenotypes?

because natural selection acts directly on phenotypes, ore genetic variation in a population enables more phenotypic variation

Identify two examples of natural selection acting on phenotypes.

rock pocket mice, 3 spined stickleback

What are the three types of selection? Identify an example of each type of selection.

directional - beak sizes of birds during wet/dry seasons in Galapagos

disruptive - small beaks for small seeds; large beaks for large seeds

stabilizing - average human birth weight

What is Hardy-Weinberg equilibrium?

frequencies of alleles and genotypes in a population's gene pool remain constant over generations; describes a population that is NOT evolving

What are the five conditions that must be TRUE for Hardy-Weinberg equilibrium?

no mutations

random mating (no sexual selection)

no natural selection

extremely large population size (no genetic drift)

no gene flow

What is allele frequency?

the frequencies of the dominant allele and recessive allele in the population

What is genotypic frequency?

the frequencies of the homozygous dominant, heterozygous, and homozygous recessive genotypes in the population

What is the equation for Hardy-Weinberg equilibrium? Identify all the variables in the equation.

p2 + 2pq + q2 = 1

p = frequency of dominant alleleq= frequency of recessive allele

p2 = frequency of the homozygous dominant genotype

2pq = frequency of the heterozygous genotype

q2 = frequency of the homozygous recessive genotype

There are three colors of snapdragons, solve for all the values if there are 100 red flowers, 800 pink flowers, and 100 white flowers. Solve for the alleles.

p =200+800/2000=0.5

q =.200+800/2000=0.5

p^2 =(0.5)2 = 0.25

2pq =.2(0.5)(0.5)=0.5

q^2 =(0.5)2 = 0.25

Flowers can either be purple (dominant) or white (recessive). Solve for all the values if 75% of the flowers are purple. Solve for q^2, then solve for other values.

q^2 =1.0-0.75 = 0.25

q = root(0.25) = 0.5

p =1.0 - 0.5 = 0.5

p^2 =(0.5)2 = 0.25

2pq =2(0.5)(0.5)=0.5

What does it mean if the allele frequency changes from one generation to the next?

Evolution is happening

What does it mean if the genotype frequency stays the same from one generation to the next?

No evolution is happening

Why are small populations more susceptible to changes in allele frequency?

Genetic drift is more likely to occur; completely random changes in the population's allele frequency due to which organism's randomly reproduce that generation

What is biogeography?

the geographic distribution of organisms

How does geographical data support evolution? Provide one example geographical data.

species in nearby geographic areas resemble each other

Galapagos finches

How does geological data support evolution? Provide one example of geological data.

fossils in different rock layers can show evolutionary changes that occur over time and the origin of major new groups of organisms

transitional fossils like archaeopteryx

How does physical data support evolution? Provide one example of physical data.

homologous structures can provide evidence of evolution

forelimbs of humans, bats, whales, etc.