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Biology Chapter 17 Questions

Terms in this set (64)

How do genes make evolution possible
allele frequency changes in a gene pool; that causes evolution and populations to change over time
How do new species form
formation of a new species is called speciation; this can happen when populations become reproductively isolated
what can genes tell us about an organism's evolutionary history
A molecular clock uses mutations rates in DNA to estimate the time that two species have been evolving independently
Darwin's original ideas can now be understood in genetic terms. Researchers discovered that traits are controlled by ___________ and that many genes have at least two forms, or __________. The combination of different alleles is an individuals's _______________. Natural selection acts on _______________.
genes
alleles
genotype
phenotype
Genetic variation and evolution are studied in populations. Members of a population share a common group of genes called a ________________. ____________ is the number of times an allele occurs in a gene pool compared with the number of times other alleles for the same gene occur. In genetic terms, evolution is any change in the _____________ in a population
gene pool
allele frequency
allele frequency
What are the three main sources of genetic variation
mutations, genetic recombination during sexual reproduction, and lateral gene transfer
A __________ is any change in a sequence of DNA. Most heritable differences are due to genetic ______________ during sexual reproduction. This occurs during _____________ when each chromosome in a pair moves independently. Genetic recombination also occurs during crossing-over in meiosis. _________________________ is the passing of genes from one organism to another organism that is not its offspring
mutation
recombination
meiosis
lateral gene transfer
The number of different ____________ for a given trait depends on how many genes control the trait. A __________________ is controlled by one gene. A example in snails is the presence or absence of dark bands on their shells. A _________________ is controlled by two or more genes, and each gene often has two or more alleles. An example is human height
phenotypes
single gene trait
polygenic trait
A gene pool typically contains different ____________ for each heritable trait. The number of times that an allele occurs in a gene pool compared with the number of times other alleles for the same gene occur is called the ___________ of the population. Natural selection works on an organism's ____________ rather than its ___________. A _______________ consists of all the genes, including the alleles for each gene, that are present in a population
allele
allele frequency
phenotype
genotype
gene pool
Describe how a geneticist might be able to tell that this population is evolving
frequency of alleles change
Can you determine whether an allele is dominant or recessive on the basis of the ratio of phenotypes in the population
no because the frequency of alleles doesn't have to do with whether the allele is dominant or recessive. Phenotype ratios depend on the allele frequencies of the dominant and recessive alleles
What are mutations and when do they affect evolution
any change in the genetic material of a cell; they affect evolution if they occur in the germ line cells that produce eggs or sperm. They can produce change in phenotype that affects fitness
Identify two ways in which genes can be recombined during meiosis
-gene swapping during meiosis
-independent assortment of chromosomes
How does sexual reproduction affect a population's genetic variation
Genetic recombination during sexual reproduction produces different phenotypes through the production of new/unique genetic combinations
What is lateral gene transfer and how does it affect variaiton
Lateral gene transfer is the passing of genes from one organism to another that is not its offspring. It occurs between organisms of the same or different species. It increases genetic variation in any species that picks up the "new" genes
Each gene of a polygenic trait often has two or more ____________. Height in humans is an example of a _____________ trait. A single polygenic trait often has many possible __________
alleles
polygenic
genotypes
A symmetrical bell-shaped graph is typical of _________ traits. The number of _____________ produced for a given trait depends on how many genes control the trait
polygenic
phenotypes
Compare and contrast single-gene traits and polygenic traits
Single Gene Traits= controlled by only one gene; may have just 2 or 3 distinct phenotypes
Polygenic Traits- controlled by two or more genes; many different phenotypes, they're not clearly distinct from one another
Both- controlled by genes
Why is genetic variation important to the process of evolution
Genetic variation is the raw material of evolution. This leads to different members of populations have different fitness levels. Variations enable species to adapt to changing environments. The population would not evolve without variaitons
Natural selection on a _________ trait can lead to changes in allele frequencies and changes in phenotype frequencies. For _________ traits, populations often exhibit a range of phenotypes for a trait. When graphed this range usually forms a _______ curve, with fewer individuals exhibiting the extreme phenotypes than those the average (in the case of beak size, the extremes may be tiny and large beaks). Natural selection on polygenic traits can cause _______ to the bell curve depending upon which phenotype is selected for
single-gene
polygenic
bell
shifts
________________ takes place when individuals at one end of the bell curve have higher fitness than those near the middle or at the other end of the curve. For example,when large seeds are plentiful the larger-beaked birds in a population may be selected for. ___________________ takes place when individuals near the middle of the curve have higher fitness than individuals at either end. _______________ takes place when individuals at the upper and lower ends of the curve have higher fitness than individuals near the middle
directional selection
stabilizing selection
disruptive selection
In small populations, alleles can become more or less common simply by chance. This kind of change in allele frequency is called ______________. The ________________ is a change in allele frequency following a dramatic reduction in the size of a population. The _______________ is a change in allele frequency that may occur when a few individuals from a population migrate to and colonize a new habitat
genetic drift
bottleneck effect
founder effect
If allele frequencies in a population do not change, the population is in ____________ ____________. Evolution is not taking place. Populations are rarely in genetic equilibrium. Most of the time, evolution is occurring. For example, many species exhibit _____________ mating patterns. ______________, or the process in which an individual chooses its mate based on heritable traits (such as size or strength), is a common practice for many organisms
genetic equilibrium
non-random
sexual selection
the ______________________ states that allele frequencies in a population should remain constant unless one or more factors cause those frequencies to change. These factors include: _______________ mating, _______ population size, immigration or emigration, ___________, and natural selection
Hardy-Weinburg Principle
non-random
small
mutations
If a trait made an organism less likely to survive and reproduce, what would happen to the allele for that trait
fewer copies of the allele would pass to future generations; the allele could disappear from the gene pool
If a trait had no effect on an organism's fitness, what would likely happen to the allele for that trait
it's frequency would stay about the same, the allele wouldn't be under pressure from natural selection
What effect does stabiliizing selection have on variation in a population
stabilizing selection would reduce variation in a population
In small populations random changes in _______________ is called genetic drift. The __________________ is a change in allele frequency following a dramatic reduction in the size of a population. A situation in which allele frequencies change as a result of the migration of a small subgroup of a population is known as the ___________________
allele frequencies
bottleneck effect
founder effect
Genetic drift can result from Founder Effect and Bottleneck Effect-what are they caused by
Founder= migration of a small subgroup of a population
Bottleneck= dramatic reduction in the size of a population
What does the Hardy-Weinburg principe state
Allele frequencies in a population should remain constant unless one or more factors cause them to change
What is genetic equilibrium
situation in which allele frequencies remain constant
Explain how sexual selection results in non-random mating
when choosing a mate based on heritable traits like size, strength, coloration, an individual is practicing sexual selection. Individuals mate chice is not random
List the five conditions that can disturb genetic equilibrium and cause evolution to occur
nonrandom mating, small population size, immigration or emigration, mutations, natural selection
Suppose a population of insects live in a sandy habitat. Some of the insects have tan bodies and some have green bodies. Over time, the habitat changes to a grass filled meadow. Use the ideas of natural selection to explain how and why the insect population might change
Tan insects may have camouflaged from predators in the original sandy habitat, which makes them more successful than green insects. Green bodies may be more successful hiding from predators in a green, grassy meadow. Green bodied insects will survive and produce more offspring than the tan-bodied insects in the changing environment. Over time the frequency of the green bodied allele would probably increase
_________________ is the formation of new species. For one species to evolve into two new species, the _____ ________ of two populations must become seperated or reproductively isolated. _______ ___________ occurs when members of two populations do not interbreed and produce fertile offspring. This can develop through behavioral, geographic, or temporal isolation
speciation
gene pools
reproductive isolation
_________ __________ occurs when populations have different courtship rituals or other behaviors involved in reproduction. ________ __________ occurs when populations are separated by geographic barriers, such as mountains or rivers. _________ __________ occurs when populations reproduce at different times
behavioral isolation
geographic isolation
temporal isolation
Peter and Rosemary _______ work supports the hypothesis that speciation in the Galapagos finches was, and still continues to be, a result of the ________ effect and ____________ _________
Grant's
founder
natural selection
Speciation in Galapagos finches may have occurred in a sequence of events that involved the founding of a new ___________, __________ isolation, changes in the gene pool, _________ isolation, and ecological competition
population
geographic
behavioral
For example, a few finches may have flown from the mainland of __________ __________to one of the islands. There, they survived and reproduced. Some birds may have crossed to a second island, and the two populations became _____________ isolated. _________ sizes on the second island could have favored birds with larger beaks so the population on the second island evolved into a population with larger beaks. Eventually these large beaked birds became _____________ isolated and evolved into a new species
South America
geographically
seed
reproductively
What is speciation
formation of new species
What does it mean for two species to be reproductively isolated from each other
members of the two species don't interbreed and produce fertile offspring
What must happen in order for a new species to evolve
populations must be reproductively isolated from one another
List three ways that reproductive isolation occurs
behavioral, geographic and temporal isolation
When does geographic isolation occur
geographic isolation occurs when populations are separated by geographic barriers such as rivers, mountains, or bodies of water
When does behavioral isolation occur
when populations have differences in courtship rituals or other behaviors (prevent from interbreeding)
What is an example of temporal isolation
three similar orchids live in the same rain forest releases pollen on different days
Suppose a seamount forms from an underwater volcano. Birds on the mainland colonize the island. How might this lead to speciation
The birds become reproductively isolated mainland birds through geographic isolation. The gene pool of the colonized birds on the island would remain isolated. The birds could evolve and become a new species as they adapt to island habitat
Peter and Rosemary Grant spent years on the Galapagos Islands studying changes in ________ populations. The ancestors of the Galapagos Island finches originally came from the continent of _____________. Many finch characteristics appear in bell-shaped distributions typical of _____________ traits.
finch
South America
polygenic
Big-beaked finches that prefer to mate with other big-beaked finches are ___________ isolated from small-beaked finches living on the same island. The populations of finches on separate islands are _____________ isolated from one another by large stretches of open water
behaviorally
geographically
Explain why reproductive isolation must occur for separate populations of the same species to evolve into different speciesq
Reproductive isolation must occur in order for gene pools to be isolated. Changes in one gene pool won't be carried to another gene pool. Accumulated gene pool changes can produce a new species.
A _________ __________ uses mutation rates in DNA to estimate the length of time that two species have been evolving independently. These models assume that ___________ mutations, which do not affect phenotype, accumulate in the DNA of different species at about the same rate. Two species evolving independently from each other will accumulate different neutral mutations through time. the more differences between the DNA, the _________ time has passed since the two species shared an ancestor
molecular clock
neutral
more
New genes evolve through the _________, and then modification of existing genes. Organisms may carry multiple copies of the same gene. The extra copies of a gene may undergo ___________. The mutated gene may have a new function that is different from the original gene. In this way new genes ___________. Multiple copies of a duplicated gene can turn into a gene __________
duplication
mutations
evolve
family
Researchers study the relationship between evolution and _________ development. Some genes called ________ genes control the forms of animals' bodies. Small changes in Hox genes during embryological development can produce major changes in _________ organisms. Some scientists think that changes in Hox genes may contribute to major evolutionary changes
embryological
Hox
adult
What is a molecular clock
model that uses DNA comparisons to estimate the length of time that two species have been evolving independently
Why are only neutral mutations useful for molecular clocks
neutral mutations accumulate in the DNA of different species at about the same rate because they're unaffected by natural selection
Why are there many molecular clocks in a genome instead of just one
some genes accumulate mutations faster than others
Multiple copies of a duplicated gene can turn into a group of related genes called a __________ ___________. A chromosome many get several copies of the same gene during the process of _______________
gene family
crossing-over
How a new change can evolve from a duplicated gene:
Original gene --> _________ in ancestor--> _________ in one copy--> New genes evolved new ____________
duplication
mutation
functions
(OR)How a new change can evolve from a duplicated gene:
Original gene --> _________ in ancestor--> Exact copy of _______ gene--> orginal gene keeps original _________
duplication
original
function
What genetic factor might be responsible for a change in an organism's body plant
a change in Hox gene activity during embryolical development can change an organism's body plant
How can Hox genes help reveal how evolution occurred
Homologous Hox genes establish body plans in species that haven't shared a common ancestor in millions of years. Hox genes may be based on major evolutionary changes. A change can result in major body changes for an animal. Scientists may trace Hox gene changes to determine when certain species developed
All of the genes in a population make up the _______________ of the population. Traits controlled by two or more genes are _____________. _________________ occurs when members of two populations do not interbreed and produce fertile offspring
gene pool
polygenic traits
reproductive isolation
The separation of two populations by barriers such as rivers or mountains results in ________ isolation. The __________ principle states that allele frequencies in a population should remain constant unless one or more factors cause those frequencies to change. ___________ is the formation of new species
geographic
Hardy-Weinberg
speciation
_______________ occurs when the allele frequencies in a population remain constant. For polygenic traits, when individuals near the center of the bell curve have higher fitness than individuals at either end, _______ selection takes place. When researchers us a ________________ they compare stretches of DNA to mark the passage of evolutionary time
genetic equilibrium
stabilizing
molecular clock
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