Biology questions

allele frequency is calculated by:

# of copies of an allele/Total # of alleles for the same gene in the population

Gene flow may... 1. Promote evolutionary change 2. Reduce evolutionary change 3. Introduces new alleles to a population 4. Maintains Hardy- Weinberg conditions 5. Removes alleles from population

1,2,3,5

Lamarck

Accepted the principle of evolution Linked the great diversity of life to the environment More complex organisms evolved from less complex (fossil record) Inheritance of acquired traits EX: The giraffe ancestor lengthened its neck by stretching to reach tree leaves, then passed the change to offspring.

Survival of the fittest: how does it work?

Because there is variation among organisms, some variants are better suited to survive in their environment than are others. The stronger organisms will reproduce and pass genes on to the next generation to a greater degree than weaker organisms: differential reproduction

Constraining gene flow

Can impede adaptation by continual flow of inferior alleles from other populations

Genetic Drift

Change in gene pool (frequency of alleles) in a population that occurs by chance Magnitude of genetic drift is negatively related to population size

____ mating is a type of nonrandom mating where phenotypically different individuals mate`

Disassortative

Which type of selection acts to eliminate individuals which are intermediate on a phenotypic range?

Disruptive selection

What is true about evolutionary forces in natural populations?

Evolutionary forces can alter allele frequencies in natural populations.

Positive frequency-dependent selection

Favors common form Tends to eliminate variation "Oddballs" stand out

Frequency-dependent selection

Fitness of a phenotype depends on its frequency within the population

Which of the following agents of evolutionary change occurs when alleles move from one population to another?

Gene flow

Speciation depends on two factors...

Genetic Isolation: there is little to no gene flow between populations Genetic divergence: in reproductive isolation, they evolve sufficient genetic differences and are no longer able to produce fertile offspring

What can result to bottleneck effect? (2)

Genetic diversity of a surviving population is usually lower than the genetic diversity of original population The surviving members of the population may have different allele frequencies than the original population

Bottleneck Effect

Genetic drift can lead to the loss of alleles in isolated populations majority of phenotypes not involved in production of next gen. Alleles that initially are uncommon are particularly vulnerable May be due to natural disaster or near extinction by some other factor (man)

What did Hardy and Weinberg explain?

Genetic variation in a population

Prezygotic barriers

Habitat Isolation,Temporal Isolation,Behavioral Isolation,Mechanical Isolation,Gametic Isolation

What may result in genetic drift? (3)

Harmful alleles may increase in frequency Beneficial alleles may increase in frequency Favorable allele may be lost

Heterozygote advantage

Heterozygotes are favored over homozygotes Works to maintain both alleles in the population Sickle cell anemia Hereditary disease affecting hemoglobin Causes severe anemia Homozygotes for sickle cell allele usually die before reproducing (without medical treatment)

Mutations and genetic drift may counter selection

In nature, mutation rates are rarely high enough to counter selection Selection is nonrandom but genetic drift is random Drift may decrease an allele favored by selection Selection usually overwhelms drift except in small populations

List components of fitness (3)

Individual survival Production of viable, numerous offspring Reproductive success

Fitness

Individuals with one phenotype leave more surviving offspring in the next generation than individuals with an alternative phenotype Relative concept; the most fit phenotype is simply the one that produces, on average, the greatest number of offspring

What conditions must be met for a Hardy-Weinberg equilibrium? (3)

Mating is random No new mutations occur Population is LARGE!

Gene Flow

Movement of individuals (alleles) from one population to another by the migration of breeding individuals Mating of individuals from adjacent populations This contributes new genetic information to a population May increase variation in a population due to new alleles If continued, may decrease genetic diversity among populations and the populations become more similar

Limits of selection

Multiple phenotypic effects of alleles Larger clutch size leads to thinner shelled eggs Lack of genetic variation Gene pool of thoroughbreds limited and performance times have not improved for more than 50 years Phenotypic variation may not have genetic basis Interactions between genes - epistasis Selective advantage of an allele at one gene may vary from one genotype to another

What is the ultimate source of new alleles?

Mutation

The processes that lead to evolutionary change are...(5)

Mutations Natural Selection genetic drift gene flow non-random mating

Evolutionary change can result from which of the following? (3)

Natural Selection Migration Mutations

Natural selection and evolution are not the same

Natural selection is a process Only one of several processes that can result in evolution Evolution is the historical record, or outcome, of change through time Result of evolution driven by natural selection is that populations become better adapted to their environment

______selection is a process that can be lead to change, and _______is the outcome or record of change over time

Natural, Evolution

List all the following that can cause changes in allele or genotype frequencies in populations...(5)

Non-random mating Mutations Genetic Drift Gene Flow Natural Selection

The smallest unit of evolution is a

POPULATION!

Disassortative mating

Phenotypically different individuals mate Produces excess of heterozygotes

Assortative mating

Phenotypically similar individuals mate Increases proportion of homozygous individuals

Polyploidy

Produces individuals that have more then two sets of chromosomes

Hardy-Weinberg equilibrium

Proportions of genotypes do not change in a population if No mutation takes place No genes are transferred to or from other sources (no immigration or emigration) Random mating is occurring The population size is very large No selection occurs

Negative frequency-dependent selection

Rare phenotypes favored by selection Rare forms may not be in "search image"

Postzygotic

Reduced Hybrid Viability, Reduced Hybrid Fertility,Hybrid Breakdown

Oscillating selection

Selection favors one phenotype at one time and another phenotype at another time Effect will be to maintain genetic variation in the population Medium ground finch of Galápagos Islands Birds with big bills favored during drought Birds with smaller bills favored in wet conditions

What type of selection affects traits that influence an individual's chances to find a mating partner or to be chosen by a partner?

Sexual selection

Constructive gene flow

Spread beneficial mutation to other populations

Birds that lay intermediate numbers of eggs have greater fitness than birds that lay either too many or too little. What type of selection is this?

Stabilizing selection

Fitness has many components

Survival Sexual selection - some individuals more successful at attracting mates Number of offspring per mating Traits favored for one component may be a disadvantage for others

List all of the following that can result from assortative mating. (2)

The proportion of heterozygotes in the population decreases The proportion of homozygous in a population increases

What can likely happen to uncommon alleles in small, isolated populations as a result of genetic drift?

They are likely to be lost

Allopatric

Two populations are geographically isolated populations evolve differently

Sympatric Speciation

Two populations share the same geographic region Many varieties Adapt to different factors found in the same area Polyploidy Ecological Isolation

Non-random Mating

Type of self-selection a. Sexual selection (peacocks) -Females choose their mates by the size & shape of, and the number of eye spots on their tails Research shows that # of eye spots correlates with larger offspring and better chance of survival

Darwin

Variation among organisms; this variation is inherited Overproduction of offspring that leads to a struggle for survival - competition Some organisms are better equipped than others - to survive a particular environment The traits that allow them to fit into that environment are called adaptive traits adaptive traits accumulate within a population EX: Over many generations, longer-necked individuals are more successful, perhaps because they can feed on taller trees, and pass the long-neck trait on to their offspring.

3 conditions for natural selection to occur and to result in evolutionary change

Variation must exist among individuals in a population Variation among individuals must result in differences in the number of offspring surviving in the next generation Variation must be genetically inherited

Biological Species Concept

a population or group of populations whose members have the potential to interbreed in nature and produce viable, fertile offspring Do not produce viable, fertile offspring with members of other groups Reproductively isolated Limitation

Gradualism

accumulation of small changes

Autopolyploidy

all of the chromosomes arise from the same species; Error in cell division

(a) Monophyletic group (clade)

all the descendants of a common ancestor and only its descendants

Evolution occurs in a population when______ change from one generation to the next

allele frequencies

Natural Selection favors characteristics that confer a survival advantage because these traits...

are also likely to increase the likelihood of reproduction

Sister taxa

are groups that share an immediate common ancestor

Which evolutionary mechanism changes genotype frequencies but does not change allele frequencies?

assortative mating

Recent evolutionary studies have shown that Darwin was mistaken in his belief that evolution occurred:

at a very slow pace Recently many rapid examples have been described

Migration from one population to another is can....

can introduce new alleles to recipient population change the frequencies of existing alleles in recipient population

biological evolution

change in life forms over time common ancestry simple to more complex (descent with modification in response to the environment and environmental changes

(c) Polyphyletic group

descendent from two or more ancestors

A sudden and permanent change in the environment can lead to a type of natural selection called ___________

directional selection

The term that describes the process in which an allele for a particular gene has different effects depending on alleles at other genes is...

epistasis

The word______is used to refer how an entity, such as a species, changes over time.

evolution

Founder Effect

few individuals establish a new, isolated population even rare alleles become significant

Evolution is detectable by examining the population's...

gene pool

Evolutionary change cannot occur in populations with no_____variation

genetic

Natural populations exhibit significant_____ and phenotypic variation

genotypic

Disruptive selection removes______ phenotypes from a population

intermediate

polytomy

is a branch from which more than two groups emerge

shared ancestral character

is a character (trait) that originated in an ancestor of the taxon

Define Population

is a group of interbreeding organisms of the same species.

Define allele

is an alternate form of a gene.

shared derived character

is an evolutionary novelty unique to a particular clade

Punctuated

long periods of stability followed by relatively rapid change

Phylogeny

look at similarities and differences of organisms

Charles Darwin referred to evolution as " descent with____"

modifications

Natural selection results in a population better adapted to its environment because

only individuals who are well adapted to their environment contribute their alleles to the next generation

Speciation

process by which one species splits into two or more species

Mutation

random changes in genetic material only source of new genes in population mutations passed through gametes NOT somatic can be lethal, advantageous, or neutral Rates generally low Other evolutionary processes usually more important in changing allele frequency

phylogenetic tree

represents a hypothesis about evolutionary relationships

branch point

represents the divergence of two species

Analogy

similarity due to convergent evolution occurs when similar environmental pressures and natural selection produce similar adaptations in organisms from different evolutionary lineages

Homology

similarity due to shared ancestry The more complex two similar structures

Single-base differences between individuals in a population are know as...

single-nucleotide polymorphism

(b) Paraphyletic group

some of the descendants from a common ancestor

Systematics

studies evolutionary history of organisms using Fossils Morphologies Molecular / genetic data

Adaptive radiation

the appearance of many new species with a wide variety of adaptations often occurs when a new habitat becomes available with few other species and many available resources classic example is Darwin's finches on the Galapagos Islands or the honeycreepers in Hawaii

Define gene pool

the entire collection of genes and alleles.

Allopolyploidy

two species hybridize

Molecular systematics

uses DNA and other molecular data to determine evolutionary relationships

Phylogenetic trees do not indicate

when species evolved or how much genetic change occurred in a lineage It shouldn't be assumed that a taxon evolved from the taxon next to it