Exam II - Intro to Evolution

What is a phenotype?

What is a phenotype?

Observable or measurable characteristic or trait

True or False: Phenotypes can only be caused by one gene

False: Phenotypes can be caused by one or few or many genes. They can also be influenced by the environment.

What is a genotype?

The genetic makeup of an individual or an individual’s DNA sequence

What are categorical variations caused by?

small number of genes

Give 3 examples of categorical variation

Blood type; coat color; white clover cyanogenesis

What are numerical/quantitative variations caused by?

many genes

Provide 3 examples of numerical variations

Hair length; number of flowers produced; disease risk

Why is there a lack of perfect mid-parent offspring correlation with traits that have numerical variation?

Since numerical variations are caused by many genes, meaning they are polygenic there is greater “noise" in heritability correlations

What is the only aspect of variation that is passed onto offsprings?

DNA

What is heritability?

Measurement of a trait in a population to see the degree to which genetics is causing offsprings to resemble their parents

What do midparent-offspring correlations indicate?

heritability

What does a midparent-offspring value of m=0 indicate?

Phenotype is not heritable and offsprings do not resemble parents

What does a midparent-offspring value of m=0.3-0.6 indicate?

Phenotype is moderately heritable and somewhat influenced more by the environment

What does a midparent-offspring value of m=1 indicate?

Perfect correlation. Phenotype is almost entirely heritable with very little contribution by environmental factors.

List 2 causes for a lack of perfect midparent-offspring calculations

1. Potentially complex gene-environment interactions; 2. Many genes/alleles interacting to determine phenotype

True or False: High heritability leads to constant traits overtime

False: High heritability does not mean traits are constant over time )Ex. Galapagos finches between 1978 and 1976; Trait of beak depth is highly heritable; Finches depth significantly increased over the two years)

True or False: Non-heritable traits can be under selection

True (Ex. Salmon pink color change due to greater consumption of beta carotene; Leads to better health and more offsprings; Salmon offsprings do not have pink color)

State a source of new variation in organisms

mutations

State the connection between mutations and selection

Random mutations generate phenotypic variation → non-random selection chooses from the available variations

True or False: Mutations are more likely to occur if they are advantageous

False: Mutations are not “directed” and are random

What are the two types of mutations and their types?

Genetic mutations (insertion; deletion; substitution); chromosomal mutations (duplications; inversions; translocations; deletions)

What is the difference between mutations and recombination?

Recombination is the making of new genetic combinations (New source of variation); Mutations are a change in genetic code (New genetic combinations)

Recombination only happens in these species

Sexual species

What are the 3 components of fitness?

1. Survival; 2. Mating Success; 3. Reproduction

What is the difference between meiosis and mitosis?

Meiosis is the production of sex cells (gametes); Mitosis makes identical body cells for growth and repair

Only these types of mutations are potentially heritable

Mutations that occur during meiosis

What is a chromosome?

Tightly packed DNA during production of new cells

What are homologous chromosomes?

Two chromosomes with the same genes in the same order but potentially different alleles

What occurs during recombination or crossing over?

Homologous chromosomes exchange genetic information

When does recombination occur?

During meiosis

How does recombination contribute to evolution?

Recombination can speed up evolution by providing more trait variations that can lead to differential fitness

What 2 factors cause variation?

mutations; sexual reproduction (recombination)

Why are asexual speices at an evolutionary disadvatnage?

Asexual speices need to unqieuly evolve each allele (instead of crossing over)

Is evolution a theory; fact; or hypothesis and why?

Theory because it is a collection of five interdependent but related set of ideas

True or False: Individual organisms evolve within a lifetime

False: individuals do not evolve within a lifetime

What was wrong with the “Typology Paradigm”?

It believed species did not change over time

Who was the first scientists to refute the “Typology Paradigm”?

Lamarck

What idea did Lamarck put forth and what was wrong with it?

Lamark believed organisms could change overtime and “evolve as such”; However organisms won’t change traits when needed to meet the environment.

True or False: Changes that occur within an individual’s lifetime are passed onto offsprings

False: changes that occur within an individual’s lifetime are NOT passed (ex. Sun tan; dying hair; etc.)

Who influenced Charles Darwin and what was their idea?

Malthusian ideas

What did Charles Darwin publish?

“Origin of Species” in 1859

What did young Charles Darwin study?

“William Paley’s Natural Theory of 1802

How did the “Typology Paradigm” and the theory of evolution differ?

The “Typology Paradigm” focused on similarities; Evolution focused on variation between organisms

What were Malthus’s 2 ideas?

1. Increase in population is necessarily limited by resources; 2. Populations grow when they are increased resources

What did Darwin conclude from Malthus?

favorable variations would be preserved and unfavorable destroyed

Who also independently but later came up with the theory of natural selection?

Alfred Russel Wallace

Which species do island species resemble?

largest nearby continental population

What did Darwin conclude about island species?

diverse inhabitants on islands weren’t created but colonizers

What inference supports the struggle for existence?

not all individuals in a population survive to reproduce (differential survival)

What are the 3 facts that lead to a struggle for existence?

1. Populations naturally tend to increase exponentially when resources are unlimited 2. Populations are subject to limiting factors in nature 3. Populations do not grow exponentially for extended periods and ultimately experience logistic growth

What is the 4th fact?

There is variation between individuals in populations/species

What is the 5th fact?

Some variation is genetically heritable

What determines variation/phenotypes/fitness/traits between individuals?

genetics and environment

What is a the difference between a theory and hypothesis?

A theory is an integrated set of ideas based on multiple well supported hypothesis while a hypothesis is a proposition or conjecture

What is a fact?

hypothesis supported by a large body of accumulated evidence

What are the 5 parts of Darwinian Evolution?

1. Evolution per se (lineages of organisms change over time); 2. Common descent (organisms share a common ancestor); 3. Multiplication of species (one species can give rise to 2 or more species); 4. Natural selection (evolution leads to adaptations); 5. Gradualism (evolution happens slowly over long periods of time)

What are the 3 conditions needed for natural selection?

1. Variation; 2. Heritability; 3. Differential survival (and reproduction)

How are mutations random?

Where(genomic position); who(first individuals); how(fitness effects); and when(timing) mutations occur leads to them being random

What are the 3 modes of selection?

directional; disruptive; stabilizing

In which mode of selection does mean increase/decrease and SD never increases?

directional

In which mode of selection does the mean stay the same and SD increases?

disruptive

In which mode of selection does mean stay the same and SD decreases?

stabilizing

How does natural selection cause evolution?

Increasing frequency of beneficial traits that led to a higher reproduction in the previous generation

True or False: Populations change traits because they need to

False: populations cannot change traits because they need to

True or False: Changes in a population occur through gradual change in all members of a population

False: all members of a population do not change

True or False: The environment directly causes change and/or mutations that will be inherited by offsprings

False: mutations are not inherited (unless mutation occurred during meiosis)

True or False: Mutations are intentional adaptive resources

False: mutations are random

True or False: Offsprings only inherit traits that are beneficial

False: offsprings do not inherit only beneficial traits

True or False: Traits/characteristics acquired during an organism’s lifetime are heritable

False: traits acquired during an organism's lifetime are not heritable

What component of fitness does sexual selection impact?

mating success

What is sexual selectoin?

selection on traits that enhance mating success

What is the selecting agent in sexual selection?

Females

What are the expected behaviors in sexual selection?

Females should resist mating unless presented with the “right” stimulus; males will tend to compete for mating opportunities

Why do males compete and females choose?

reproduction costs females more than males and they are available to mate less

What are the types of sexual selection and their difference?

intrasexual selection(male-male competition… females still choose at the end); intersexual selection(female choice)

Why can sexual selection be detrimnetal to males?

what is attractive to a female could be harmful to the male therefore increased mating success can lead to decreased survival

True or False: sexual selection and natural selection dont always act in the same direction

True: sexual selection can be harmful to males

How should you determine which mode of selection is present?

draw arrows down on what is being selected against

What are alleles?

different versions of genes

What are the types of alleles?

Homozygous genotype(same allele twice); heterozygous genotype(two different allele)

True or False: There are always more than two alleles present in a population for every gene

True: A single individual can only have at most 2 unique alleles but a population can have more

Who is Gregor Mendel?

monk who bred pea plants for which classical genetics is named after

What is complete dominance?

two different alleles but only one phenotype is present

True or False: The dominant allele is always better in terms of fitness

False: Dominant does not mean bigger; faster; stronger; better; higher fitness; or more common in the population

What is codominance?

Co=both; both alleles expressed separately

What is an example of codominance?

blood type

What is incomplete dominance?

incomplete=in between; both alleles are partially expressed resulting in an intermediate phenotype

How do you calculate relative fitness?

survival rate/largest survival rate in population (survival reproductive rate of a genotype relative to maxim survival reproduction rate of other genotypes in the population)

What do you calculate selection coefficient?

1-relative fitness

What is the selection coefficient?

measure of relative strength of selection against a genotype

What matters more relative or absolute fitness?

relative fitness because individuals with highest relative fitness will have their genes overrepresented

What is the difference between relative and absolute fitness?

absolute fitness is the total number of offsprings; while relative fitness is the offsprings you have relative to other individual sin the population

Which allele frequencies will change more quickly?

the ones with the largest difference in fitness between alleles

How do you determine fitness advantages?

compare relative fitness between species

What two scientists traveled voyaged around the world?

Charles Darwin and Alfred Russel Wallace

What is the difference between a manipulative and observational experiment?

An observational study is when the researcher observes the effect of a specific variable as it occurs naturally, without making any attempt to intervene. In an experiment, the researcher manipulates the situation and observes the effect in a more controlled setting.

What are the 3 conditions needed for natural selection?

1. Variation; 2. Heritability; 3. Differential survival (and reproduction)