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
