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
