Evolution Quiz

Six Stages of the Scientific Method

1. Observe/Question 2. Forming hypotheses 3. Make predictions 4. Test hypotheses 5. Conduct controls to eliminate hypotheses 6. Form conclusions from the remaining hypotheses.

What does a gene code for?

Protein.

3 Requirements for evolution by natural selection

1. Individuals are different (variation) 2. Differences are heritable 3. Differences lead to higher or lower fitness

Hardy Weinberg Requirements

1. Large population 2. Random Mating 3. No Immigration/emigration 4. No mutation 5. No selection This is what needs to happen for allele frequencies to stay the same over time.

Bottleneck Effect

A change in allele frequency following a dramatic reduction in the size of a population; decreases genetic variation Ex: natural disaster wipes out a large portion of a bird population hunting of cheetah population causes drastic reduction of cheetah species

How do different versions of a gene (alleles) change the function of a protein?

Alleles differ in their base sequences. The difference in base sequence causes the alleles to make different versions of a protein, resulting in different phenotypes.

How does independent assortment and crossing over create variation in gametes produced by a single individual?

In meiosis, homologous chromosomes are randomly distributed to daughter cells and different chromosomes segregate independently. This results in unique combinations of chromosomes.

Meiosis produces 4 ___ cells Mitosis produces 2 ____ cells

Meiosis produces 4 haploid cells Mitosis produces 2 diploid cells

Pre-Zygotic Reproductive Isolation

before fertilization - behavioral (ie two frogs do not recognize each other's mating call) - Temporal (ie one frog mates in summer, one mates in spring) - Habitat Isolation: populations live in different habitats and do not meet -Mechanical Incompatibility: genitalia of one species only fits that of the same species -Gametic Isolation: Female and male gametes fail to unite in fertilization

founder effect

change in allele frequencies as a result of the migration of a small subgroup of a population

Does natural selection act on phenotype or genotype?

Phenotype! Natural selection acts on an organism's characteristics (phenotype), not directly on its alleles (genotype). Natural selection favors a particular physical trait or behavioral characteristic over another.

Does an individual or a population evolve?

Population evolves. This is because individuals in a population vary, and some in the population are better able to survive and reproduce given a particular set of environmental conditions

Explain how and why individuals with different phenotypes might have different fitness in different environments

The environment in which a population of organisms lives is integral to the selection of traits. Some differences introduced by mutations may help an organism survive in one setting but not in another—for example, resistance to a certain bacteria is only advantageous if that bacteria is found in a particular location and harms those who live there.

sympatric speciation

The formation of new species in populations that live in the same geographic area Ex: speciation due to pollinator -> red flower attractive to hummingbird, while blue flower is attractive to bees

Phenotype

The observable expression of the genotype or trait

Example of how a selective agent can cause evolution to occur

The selective pressure of competition caused long neck and legs in giraffes. Food sources became low (subject to large competition) so, selection pressures favored the specimens in the population with longer legs and necks. Taller giraffes could reach higher vegetation, and would have a stronger possibility to survive any struggle for existence and pass on their traits to their offspring. This meant that only the healthiest and longest giraffes reproduced many offspring, resulting in the common image of the giraffe that is known today since the genetic variation lived on through the generations.

In a species of goose, the white body form (the snow goose) and the blue body form (the blue goose) occasionally coexist. In these areas.of contact, white by white and blue by blue matings are much more common than white by blue mating. What H-W principle does this violat?

There is no random mating.

Example of a monophyletic group

Turtles, Lizards&snakes, crocodiles&alligators, and birds.

Meiosis Function

Used for reproduction and thus, genetic diversity. Sexual reproduction for gametes and spore

Mitosis Function

Used to reproduce somatic cells for growth and metabolism. Asexual reproduction for single-celled organisms. Development and tissue regeneration or multicellular organisms

Explain how a mutation occurs and spreads through a population by natural selection

Variations often alter gene activity or protein function, which can introduce different traits in an organism. If a trait is advantageous and helps the individual survive and reproduce, the genetic variation is more likely to be passed to the next generation (a process known as natural selection). Over time, as generations of individuals with the trait continue to reproduce, the advantageous trait becomes increasingly common in a population, making the population different than an ancestral one. Sometimes the population becomes so different that it is considered a new species.

Allele

Versions of a gene

Natural Selection

When certain phenotypes are more successful than others, so they go on to survive and reproduce more successfully than others

Vicariance Speciation

a geographic barrier arrises within a single population, separating it into 2 or more isolated populations Ex: road

Biological Fitness

a measure of the ability to survive and reproduce relative to other members of the population greater fitness = greater chance of survival = greater chance of producing offspring = evolution

Prior to the Mongolian invasions that occurred between the 6th and 16th centuries, the frequency of blood type B across Europe was close to zero. The frequency of blood type B among the Mongols was relatively high. Today, it is possible to see fairly high frequencies of blood type B as one moves from the Eastern European countries to the Western European countries. What H-W principle is being violated? What is the name of the evolution mechanism occuring?

Immigration/emigration, the Mongols moved into the European population. This is gene flow.

Speciation

the process that produces new and distinct forms of life reproductive isolation!!

Allopatric Dispersion Speciation

when a few members of a species move to a new geographical area far from the main source populations

Gene-by-environment interactions

when the environment influences gene expression Ex: a child of a professor may be pre-disposed to intelligence, and being raised in an intellectually stimulating household will push the child to their full potential

Does mitosis more closely resemble meiosis I or meiosis II?

meiosis II bc sister chromatids separate during this process

Gene Flow

movement of alleles from one population to another; reduces strong differences between the two populations

Ploidy

number of sets of chromosomes in a cell Humans are 2n (diploid) aka 2 copies of each chromosome per cell n= # of different chromosomes Ex: Humans are 2n=46, n=23

Incomplete Dominance

occurs when a heterozygous genotype results in a phenotype between the two homozygous genotypes Ex: a white rabbit and a black rabbit make a gray rabbit

Co-Dominance

occurs when both alleles are present and represented in the offspring EX: A white cow and black cow have a white cow with black spots

Somatic Cell Mutations

take place in an organism's body cells and can therefore affect the organism; does not affect evolution as changes are not passed down to the offspring

monohybrid cross

a cross in which only one characteristic is tracked

Genetic Drift

A change in the allele frequency of a population as a result of chance events rather than natural selection.; reduces genetic variation. More pronunced in small populations Ex: Overtime the coat color in a population rabbits randomly moves between more brown morphs and more white morphs. (I .e., no selection pressure one way or another).

dihybrid cross

A cross between two individuals, concentrating on two definable traits

phylogenetic tree

A family tree that shows the evolutionary relationships thought to exist among groups of organisms species are aligned if they all still exist

What is the difference between a prediction and a hypothesis?

A hypothesis is a testable, tentative, and falsifiable explanation for an observed phenomenon in nature (what you think will happen because of a reason) A prediction is very specifically what is going to be tested (what you can observe or measure) Ex: Hypothesis: When planted alongside asparagus, marigolds will deter asparagus beetles. Prediction: If marigolds deter asparagus beetles, then asparagus plants planted alongside marigolds will host fewer asparagus beetles than asparagus plants planted on their own.

replicated vs nonreplicated chromosomes for a cell of given ploidy

A nonreplicated chromosome contains one double-strand -DNA molecule. A replicated chromosome contains two identical double-strand -DNA- molecules, the chromatids, that are joined at their centromere. 2n=8 breakdown: 2n means haploid (2 complete sets of chromosomes) and 8 is the number of chromosomes Ex: humans 2n=46. Diploid, 46 chromosomes, 23 pairs

Mutation

A random change in genetic sequencing in DNA that brings about new alleles. Can be beneficial, harmful, or neutral. Ex: a base pair in a DNA sequence changing from G to T causes a mutation.

peripatric speciation

A specific kind of allopatric speciation in which a few individuals from a mainland population (small pop!!) disperse to a new location remote from the original population and evolve separately. More divergence faster bc of small population size

Epistasis

A type of gene interaction in which one gene alters the phenotypic effects of another gene that is independently inherited. --> genes that modify phenotypic ratios Ex: an offspring with tall parents may have the mutation for dwarfism.

Species Requirements

Ability to interbreed and produce viable offspring

How does a mutation occur and spread through a population by natural selection

As mutations occur, natural selection decides which mutations will live on and which ones will die out. If the mutation is beneficial, the mutated organism survives to reproduce, and the mutation gets passed on to its offspring. If the mutation is harmful, the mutated organism has a decreased chance of surviving and reproducing.

Puffy Stick Model of a Chromosome

Be able to label genes, alleles, centromeres, chromatids, & homologous chromosomes.

Evolution

Change in alleic and/or genotypic frequencies over time in a population. Manifested by changes in inherited characteristics over generations

How and why do individuals with different phenotypes have different fitness in different environments?

Different environments allow certain phenotypes to be more successful than others. For example, a frog living in a cold environment that is used to living in a warm environment will have low fitness in the cold environment and a high fitness in the warm environment. This is because the frogs who had a higher tolerance to warm climate were more present/able to produce more offspring in the warm climate. This lead to frogs with that phenotype, and subsequently the genotype were more successful in reproduction.

diploid versus haploid

Diploid: A cell with 2 complete sets of chromosomes Haploid: A cell with a single set of chromosomes

When are mutations likely to happen?

During replication (i.e. crossing over/recombination & independent assortment) and environemntal cause (i.e. UV radiation)

Post Zygotic Reproductive Isolation

Genetic Incompatibility: two or more groups of a population develop a different number of chromosomes or other gametic differences. Offspring are inviable or infertile Ex: horse + donkey = mule; horse and donkey have diff # of chromosomes and therefore produce an invalid offspring

Ultimate source of new material for evolution?

Genetic Variation, which is caused by random mutations and passed on by reproduction, provides the raw material for evolution

Heterozygous versus Homozygous

Heterozygous means having two different alleles Ex: AB, ab, Aa, Bb, bB Homozygous means having two copies of the same allele Ex: AA, BB, bb, aa

Explain a common misconception concerning evolution and one piece of evidence that refutes the misconception

Misconception: Evolution is a just a theory about the origin of life Two main points here: (1) A scientific theory is no small thing, it indicates that there is so much evidence that supports it that we must accept it. In science, we can never prove something, as we can never witness and record every single incidence of any event/phenomenon. The word "just" seems demeaning. (2) Evolution really focuses on the origin of new species and the change in species over time, NOT the origin of life itself Yes, evolution is a theory, but in order for a scientific hypothesis to become a theory, it has to go through many, many tests, experiments, and observations over time. After so much evidence accumulates, and none of the evidence has disproved the hypothesis, it becomes a theory. A theory then is an accepted explanation of a certain event or practice in nature. In casual talk, theory is thought of as a speculation, but this is very different within the scientific community, and most likely the reason the word "theory" in "the evolution theory" causes some misconception.

What is the origin of variation?

Mutation!!

Germ-Like Mutations

Mutations to the reproductive cells; type of mutation that is relevant to evolution because it can be passed down through generations.

Difference between null and alternative hypothesis

Null Hypothesis: states that a population's parameter has no statistical difference between two variables Alternative Hypothesis: there is a statistically significant relationship between the two variables

3 Types of Selection

directional, stabilizing, disruptive Directional Selection: a mode of natural selection in which a single phenotype is favored, causing the allele frequency to continuously shift in one direction. Ex: Darwin's finches w big beaks did better after the drought bc they were able to eat more seeds with their big beaks and survive and produce more offspring than those with small beaks Stabilizing Selection: a type of natural selection that favors the average individuals in a population Ex: the coats of a species of mice in a forest will all be the best color to act as camouflage in their environment. Disruptive Selection: type of natural selection that selects against the average individual in a population. The makeup of this type of population would show phenotypes (individuals with groups of traits) of both extremes but have very few individuals in the middle. Ex: Light- and dark-colored oysters could also have a camouflage advantage as opposed to their medium-colored relatives. Light-colored oysters would blend into the rocks in the shallows, and the darkest would blend better into the shadows. The ones in the intermediate range would show up against either backdrop, offering those oysters no advantage and make them easier prey. Thus, with fewer of the medium individuals surviving to reproduce, the population eventually has more oysters colored to either extreme of the spectrum.

Genotype

genetic makeup of an organism