Bio 112 Exam 1

Intersexual selection

- Between members of the opposite sex - Female choice Often results in showy characteristics for males - Cryptic female choice - Genital tract or egg selects against genetically related sperm -Inhibits inbreeding

intrasexual selection

- Between members of the same sex -Horns in male sheep, antlers in male moose, male fiddler crab enlarged claws -Males directly compete for mating opportunities or territories

Founder Effect

- Small group of individuals separates from a larger population and establishes a new colony - Relatively small founding population expected to have less genetic variation than original population - Allele frequencies in founding population may differ markedly from an original population

Modern description of natural selection

- Within a population, allelic variation arises from random mutations that cause differences in DNA sequencess - Some alleles encode proteins that enhance an individual's survival or reproductive capability compared to other members of the population -Individuals with beneficial alleles are more likely to survive and contribute their alleles to the gene pool of the next generation -Over the course of many generations, allele frequencies of many different genes may change through natural selection, thereby significantly altering the characteristics of a population

Gene Pool

-All of the alleles for every gene in a given population -Study genetic variation within the gene pool and how variation changes from one generation to the next - Emphasis is often on variation in alleles between members of a population3

Genetic Drift

-Changes allelic frequency due to random chance -Random events unrelated to fitness - Favors either loss or fixation of an allele -Frequency reaches 0% or 100% Faster in smaller populations

Inbreeding

-Choice of mate based on genetic history -Does not favor any particular allele but does increase the likelihood the individual will be homozygous - May have negative consequences with regard torecessive alleles -Lower mean fitness of a population if homozygousoffspring have a lower fitness value -Inbreeding depression

Natural selection patterns

-Directional selection - Stabilizing selection -Disruptive/Diversifying selection -Balancing selection

Disassortative mating

-Dissimilar phenotypes mate preferentially - Favors heterozygosity

Disruptive/Diversifying selection

-Favors the survival of two or more different genotypes that produce different phenotypes -Likely to occur in populations that occupy heterogeneous environments -Members of the populations can freely interbreed

Population

-Group of individuals of the same species that occupy the same environment and can interbreed with one another -Some species occupies a wide geographic range and are divided into discrete populations

Ecological factors

A biologist discovers two populations of wolf spiders whose members appear identical. Members of one population are found in the leaf litter deep within the woods. Members of the other population are found in the grass at the edge of the woods. The biologist decides to designate the members of the two populations as two separate species. Which characteristics is this biologist most closely utilizing to distinguish species?

geographic isolation

A defining characteristic of allopatric speciation is ______. Multiple choice question.

prezygotic; postzygotic

A reproductive isolating mechanism that prevents the formation of a zygote is called ______, whereas ______ isolating mechanisms come into play after the zygote is formed.

sexual dimorphism

A significant difference in the appearance of the two sexes within a species, and which is often the result of sexual selection, is called

bacteria

A vast number of species have yet to be classified. This is especially true among , which are difficult to categorize into distinct species.

Globin genes

Allows for specialized function, expression at different times or in different tissues

Mean fitness of population

Average reproductive success of members of a population As individuals with higher fitness values become more prevalent, natural selection increases the mean fitness of the population20

Microevolution

Changes in a population's gene pool from generation to generation

Adaptions

Changes in populations of living organisms that promote their survival and reproduction in a particularenvironment14Natural Selection

cladogenesis

Consider a population of sexually-reproducing organisms that splits into two or more species. This phenomenon is referred to as ______.

Stabilizing selection

Favors the survival of individuals with intermediate phenotypes Extreme values of a trait are selected against

genotype

Fitness is the relative likelihood that a ______ will contribute to the gene pool of the next generation.

gene families

Gene duplication can lead to what?

Evolution

Heritable change in one or more characteristics of a population or species from one generation to the next

allele; total number of all alleles

The allele frequency is calculated by dividing the number of copies of a specific ______ in a population by the ______ for that gene in that population.

Gradualism

The concept of __________ suggests that each new species evolves continuously over long spans of time

Macroevolutions

The evolutionary changes that create new species and groups that include many new species are described by the term

allele frequency

The number of copies of an allele in a population divided by the total number of all alleles for that gene in a population is the ______.

cladogenesis

The splitting or diverging of a population into two or more species is known as

Allele frequency

number of copies of a specific allele in a population ---------------------- Total number of gene in the population

Directional selection Stabilizing selection Disruptive/Diversifying selection Balancing selection

-Individuals at one extreme of a phenotypic range have greater reproductive success in a particular environment - Initiators -New allele with higher fitness introduced -Prolonged environmental change

Balancing selection

-Maintains genetic diversity -balanced polymorphism -two ways --For a single gene heterozygote favored --Negative frequency

Clutch size

-Too many eggs and offspring - die due to lack of care and food -Too few eggs - does not contribute enough to nextgeneration

Assortative mating

-individuals with similar phenotypes are more likely to make -Increases the proportion of homozygote individuals

Single nucleotide polymorphisms (SNPs)

-smallest type of genetic change in a gene -most common -90% of variation in human gene sequences

Population Genetics

-study of genes and genotypes in a population -Want to know extent of genetic variation, why itexists, how it is maintained, and how it changesover the course of many generations -Helps us understand how genetic variation isrelated to phenotypic variation

Polymorphism

-traits display variation within a population -Due to two or more alleles that influence phenotype

Migration

-what tends to reduce differences in allele frequencies between the two populations -Tends to enhance genetic diversity within apopulation44Migration and Non random Mating

Species

Group of related organisms that share a distinctive form Among species that reproduce sexually, members of the same species are capable of interbreeding to produce viable and fertile offspring

16

In a Hardy-Weinberg population with two alleles, A and a, that are in equilibrium, the frequency of the allele a is 0.4. What is the percentage of the population that is homozygous for this allele?

random chance

In genetic drift, allele frequencies change due to ______.

Their are fewer males that are brightly colored

In places where predators are abundant what observable traits to the males have

they are brightly colored

In places with few predators what observable trait do males have

Reproductive success

Likelihood of an individual contributing fertile offspringto the next generation Attributed to two categories of traits Certain characteristics make organisms better adaptedand more likely to survive to reproductive age Traits directly associated with reproduction, such asability to find a mate and ability to produce viablegametes and offspring15

Population

Members of the same species that are likely to encounter each other and thus have the opportunity to interbreed

Neutral variation

Much of the variation seen in natural populations is caused by genetic drift Does not preferentially select for any particular allele

Genotype frequency

Number of individuals with a particular genotype in a population ----------------------- Total number of individuals in the population

1859 Darwin

On the Origin of Species is published detailing his ideas with observational support (who and when)

Whales Dolphins Porpoises

Order cetacea

Bottleneck

Population reduced dramatically and then rebuilds -Randomly eliminates members without regard to genotype -Surviving members may have allele frequencies different from original population -Allele frequencies can drift substantially when population is small -New population likely to have less genetic variation different

Natural Selection

Process in which beneficial traits that are heritable become more common in successive generations

Fitness

Relative likelihood that a genotype will contribute to the gene pool of the next generation as compared to other genotypes Measure of reproductive success Hypothetical gene with alleles A and a AA, Aa, aa

Empirical thought

Relies on observation to form an idea or hypothesis, rather than trying to understand life from a non-physical or spiritual point of view

Prezygotic, postzygotic

Reproductive isolating mechanisms fall into two main categories ____________________ isolating mechanisms and ____________________ isolating mechanisms.

adaptation

Some genetic changes make some individuals in a population become better suited to their environment and therefore more likely to survive and reproduce. This phenomenon is termed

T

T or F Neutral mutations do not affect phenotype so they are not acted upon by natural selection

allele; total number of all alleles

The allele frequency is calculated by dividing the number of copies of a specific ______ in a population by the ______ for that gene in that population

Anatomical Developmental Molecular

Types of homologies

Fixation of an allele Loss of an allele

What are the possible outcomes of genetic drift?

Prezygotic isolating mechanisms Postzygotic isolating mechanisms

What are the two main types of reproductive isolating mechanisms?

Conditions for Hardy-Weinberg Equilibrium

What are these conditions for? -No new mutations occur -No natural selection occurs -The population is so large that allele frequencies do not change due to random sampling error -No migration occurs between different populations - Random mating

Heterozygote advantage

What type of advantage does a single gene have? Hs allele

Sexual selection

What type of selection affects traits that directly influence an individual's ability to mate successfully?

Late 1700s

When (year) did a small number of European scientist suggest life forms are not fixed

Directional selection

Which type of selection favors individuals at one extreme of a phenotypic range who have greater reproductive success in a particular environment?

Jean-Baptiste Lamarck

Who Believed living things evolved upward toward human "perfection" Inheritance of acquired characteristics Example: Giraffe necks

Jean-Baptiste Lamarck

Who realized that some animals remain the same while others change

Thomas Malthus

an economist, says that only a fraction of any population will survive and reproduce

Microevoloution

changes in a single gene in a population over time

Macroevoloution

formation of new species or groups of species

paralog

genes that are related by gene duplication in a genome

orthologs

homologous genes separated by a speciation event

Paralogs

homologous genes within a single species

Endemic

naturally found only in a particular location

Monomorphic

predominantly single allele

artificial selection

selective breeding is also called

Sexual dimorphism

sexual selection can lead to a significant difference in appearance between the two sexes. What is this called?

Evolutionary mechanisms

that alter the prevalence of an allele or genotype (natural selection, random genetic drift, migration, non-random mating) Potential for widespread genetic change13

Polymorphic gene

two or more alleles

new genetic variation

what are the following signs of (mutations, gene duplication, exon shuffling, horizontal gene transfer) Not a major factor dictating allele frequencies

Negative frequency

what type of frequency? Rare individual have a higher fitness

biochemical pathways

what types of pathways are found in nearly all species

Transitional form

what word means provides link between earlier and later forms

•Carolus Linnaeus

who extended the study of the natural world Developed an early classification system Modern species concept

George Buffon

who said that life forms change over time

Alfred Wallace

who sent Darwin an unpublished manuscript proposing many of the same ideas

John Ray

who was the first to carry out a thorough study of the natural world Developed an early classification system Modern species concept

Variation

within a given species •Traits heritable - passed from parent to offspring •Genetic basis was not yet known

Horizontal gene transfer

•Exchange of genetic material among different species •Surprisingly common phenomenon •Can transfer From prokaryotes to eukaryotes From eukaryotes to prokaryotes Between prokaryotes Between eukaryotes •Widespread among bacteria

Evidence of Evolutionary Change

•Fossil record •Biogeography •Convergent evolution •Selective breeding •Homologies Anatomical Developmental Molecular

Homology

•Fundamental similarity due to descent from a common ancestor

Natural selection

•More offspring produced than can survive •Competition for limited resources •Individual with better traits flourish and reproduce

Anatomical homology

•Same set of bones in the limbs of modern vertebrates has undergone evolutionary change for many different purposes •Homologous structures are derived from a common ancestor •Vestigial structures are anatomical structures that have no apparent function but resemble structures of presumed ancestors Ear wiggling muscles

Biogeography

•Study of the geographical distribution of extinct and modern species

Uniformitarianism hypothesis

•from geology Slow geological processes lead to substantial change Earth was much older than 6,000 years

Homologous genes

•two genes derived from the same ancestral gene Orthologs occur in separate species •Reveals molecular details of evolutionary change •Two sequences may be similar, but not identical due to the independent accumulation of different random mutations