Evolution- Ch 15 and 16 – Flashcards
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Darwin used the phrase "descent with modification" to mean that
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new species descended from preexisting species and species must be able to change over time
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According to Darwin's theory of natural selection
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organisms that have more favorable traits tend to leave more offspring
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In an evolutionary sense, an individual organism has high fitness if it
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reproduces more successfully than other individuals
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Wing of a bat and a foreleg of an alligator are
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homologous features
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Embryological comparisons reveal that..
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many vertebrate embryos look similar at early stages of development
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Fossils are
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remains or traces of preexisting organisms
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What is the process called by which different species evolve similar traits?
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convergent evolution
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Fossils found in deeper layers of rock are..
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older than those found in shallower layers
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Absolute dating involves..
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radioactive decay
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Process by which a species becomes better suited to its environment..
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adaptation
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Species that share a common ancestor..
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have few amino acid sequence differences
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Natural Selection
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improved fitness of certain individuals in the population that allows for survival and reproduction.
The primary mechanisms by which populations change over time.
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Artificial selection
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effect of humans purposefully breeding animals to select for desirable traits
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Different Species
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Offspring is INFERTILE or reproductive isolation- cannot pass on genetic code through reproductive for several generations.
differing morphology (appearance/body structure) and how much DNA the organisms share show whether or not two animals are the same species or not.
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Directional Selection
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favors individuals with an extreme value of a trait and selects against both avg individuals and those at the opposite extreme. (smaller or bigger)
-SHIFTS CHARACTER TRAITS IN A SPECIFIC DIRECTION
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Stabilizing Selection
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favors those with the avg value of a trait and selects against those with EXTREME values
-ACTS AGAINST THOSE WHO DEVIATE TOO FAR FROM THE AVG
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Disruptive Selection
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favors those at both extremes of a trait and selects against individuals with intermediate values.
-ADAPTS THOSE WITHIN A POPULATION TO DIFFERENT HABITATS
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T/F: Changes we seen in an individual are NOT evolutionary.
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TRUE; evolution occurs in a POPULATION
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Population
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a group that includes all members of a species living in a given area. Evolution alters the gene pool of a population
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Inheritance
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link between the individuals and the evolution of populations
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Alleles
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different nucleotide sequences (a form of a gene)
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Gene pool
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set that contains all of the alleles of all of the genes from all of the individuals in a population.
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Number of copies of each allele
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(# people carry only one copy of the allele) + (twice the # people that carry two copies)
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Allele Frequency
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an allele's proportion in a gene pool
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Evolution is also known as..
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the change over time in the allele frequencies of a gene pool
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Hardy Weinberg Principle
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under these conditions, allele/genotype frequencies in a population will remain CONSTANT no matter how many generations pass. AKA Equilibrium Population
1) no mutations
2) no gene flow (no one leaves/enters)
3) large population
4) random-mating/no tendency to mate certain groups with each other
5) no natural selection. Must reproduce with equal success.
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T/F: Most populations are at equilibrium.
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FALSE
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Based on H-W conditions, five major causes of evolution:
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1) mutations
2) gene flow
3) natural selection
4) NONrandom mating
5) SMALL population
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Mutations
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changes in DNA sequence. Will cause VERY small changes but still causes evolutionary change because of more possibilities. But some are neutral and do not affect the fitness of an organism
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Gene Flow
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Increase the genetic similarity of diff populations of a species. It changes the gene pool of the DESTINATION population so that it is more similar to the SOURCE population. Genes are mixed, which prevents large differences or else one will become a new species
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Genetic Drift
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process by which chance events change allele frequencies; more effective in small populations
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T/F: Changing the genetic composition in a LARGE population will not have great effect.
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TRUE
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What two things cause genetic drift?
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Population bottleneck and founder effect
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Population bottleneck
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population is drastically reduced by a natural catastrophe or overhunting. Only a few are left to contribute genes.
-Rapidly changes allele frequencies and reduces genetic variability
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Founder effect
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when isolated colonies are founded by a small number of organisms
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Nonrandom mating
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can play a huge role because organisms cannot mate strictly randomly. Can also arise if some prefer/biased towards certain mates.
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Assortative mating
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preference for mates that are similar
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Inbreeding
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sexual reproduction between relatives. This can increase occurrence of genetic diseases or defects because everyone is inheriting the same alleles. It increases the odsd of producing homozygous offspring with two copies of the harmful allele.
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T/F: Inbreeding and assortative mating will alter allele frequencies.
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FALSE; but they can impact distribution of diff geno/phenotypes in a population
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T/F: All genotypes are equally beneficial.
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FALSE; some alleIles are superior over others
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How does natural selection work?
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Survival of the fittest; favors traits that increase their possessors' survival only to the extent that improved survival leads to improved reproduction. The reproductive success determines future.
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What is the main driver of natural selection?
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differences in reproduction: individuals bearing certain alleles leave more offspring who inherit those alleles than do other individuals with different alleles.
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Fitness
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Individuals with greater lifetime reproductive success have greater fitness than do individuals with lower reproductive success. Only the FITTEST phenotypes pass traits on.
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Adaptations
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characteristics that help an individual survive and reproduce in a particular environment. Successful phenotypes have these.
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Competition
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interaction among individuals who attempt to utilize a resource that is limited relative to the demand for that resource.
-Occurs most intensely among members of the same species
-Coevolution can occur
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Coevolution
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process in which species mutually affect one another's evolution
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Predation
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any interaction in which one organism consumes another.
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3 Key points about natural selection
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1) Natural selection does not cause genetic changes in individuals
2) Natural selection acts on individuals, but it is populations that evolve
3) Evolution by natural selection is not progressive; it does not make organisms "better"
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Sexual selection
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special kind of selection that acts on traits that help an animal get a mate.
sexual contests or female preference for a particular male phenotype (elaborate and extravagant)
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Balanced polymorphism
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two or more phenotypes are maintained in a population because each is favored by a separate environmental factor
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p
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frequency of dominant allele (T)
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q
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frequency of recessive allele (t)
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Two H-W equations you have to know
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p² + 2pq + q²= 1
p + q=1
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p²
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frequency of homozygous DOMINANT (TT)
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q²
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frequency of homozygous RECESSIVE (tt)
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2pq
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frequency of heterozygous (Tt)
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OCVANS
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Overpopulation- more individuals in an area than can survive
Competition-fight it out and see which one survives
Variation- differences between the individuals in an interbreeding population
Adaptation- some characteristic that an individual has that allows it to survive; it's favorable in the environment
Natural Selection- environment determines which variations are adaptations∴advantageous
Speciation- an accumulation of these differences to the point when they cannot interbreed so they separate into distinct populations
By Isolation... (different types)
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Species
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a group of populations that evolve independently
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Biological species concept
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groups of actually or potentially inter-breeding natural populations, which are reproductively isolated from other such groups.
BUT:
1) does not help us determine species boundaries among asexually reproducing organisms
2) not always practical/possible to directly observe whether members of two different groups interbreed.
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Reproductive isolation
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inability to successfully breed outside the group; ensures evolutionary independence
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Cystic fibrosis is a recessive, inherited disease who victims die before they can reproduce. Which H-W condition would NOT be met under these circumstances?
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Gene flow since people leave the population
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In the graph we created with the trilobite fossils, what were the graphs like?
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They were both bell curves; over time, the fossils became shorter ∴ more advantageous
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Could directional selection lead to creation of new species?
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Possibly, if the bigger ones get geographically separated from the littler ones
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Could disruptive selection lead a new species?
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Yes, because it favors both extremes
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Could stabilizing selection lead to creation of new species?
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No, because majority of original population is still majority of new population.
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Isolating Mechanisms
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traits that prevent interbreeding and maintain reproductive isolation
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Premating isolating mechanisms
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mechanisms that prevent mating between species: geographic, ecological, temporal, behavioral, mechanical incompatibility
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Postmating isolating mechanisms
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factors that prevent organisms of two species from producing vigorous, fertile offspring after mating: gametic incompatibility, hybrid inviability, hybrid infertility
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Geographic isolation
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prevents interbreeding between populations that do not come into contact because they live in different, physically separated places .
-ALLOWS NEW SPECIES TO FORM
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Ecological isolation
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species do not interbreed even if they are within the same area because they occupy diff habitats
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Temporal isolation
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species do not interbreed because they breed at diff times.
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Behavioral isolation
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species do not interbreed because they have different mating rituals
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Mechanical incompatibility
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species do not interbreed because their reproductive structures are incompatible
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T/F: Production of hybrids are possible
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TRUE; offspring of parents of diff species like ligers... mules..
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Gametic incompatiblity
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sperm from one species cannot fertilize eggs of another species
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Hybrid inviability
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hybrid offspring fail to survive.
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Hybrid infertility
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hybrid offspring are sterile or have low fertility
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Speciation
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process by which new species form- depends on isolation and genetic divergence
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Allopatric speciation
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two populations are geographically separated from one another
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Sympatric speciation
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two populations share the same geographic area
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Polyploidy
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acquisition of multiple copies of each chromosome AKA cause of sympatric speciation. They cannot mate successfully with normal diploids. So they are genetically isolated from its parent species.
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T/F: Speciation by polyploidy is more common in animals than plants.
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FALSE; it's actually more common in plants because plants gametes can fly around and mate with anything. There's more flexibility.
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Adaptive radiation
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populations of one species invade a variety of new habitats and evolve in response to the differing environmental pressures in those habitats.
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Extinction
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death of the last of its members; At least 99.9% of all the species that have ever existed are extinct.
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T/F: The natural course of evolution is that old species will become extinct to allow new ones to arise
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TRUE; and the immediate cause of this is environmental changes
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T/F:Wide-ranging species will not succumb to local environmental catastrophes.
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TRUE
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What increases the risk of extinction?
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Over specialization and localized distribution; Sometimes competition and predation too
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What are the frequencies of the dominant and recessive alleles in a population of 100 cattle, of which 36 show the recessive trait? How many of the cattle are heterozygous? If natural selection eliminated all the cattle with the recessive phenotype what would the gene frequencies be?
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q²=0.36
q=0.6 (recessive)
p=0.4 (dominant)
2(0.4)(0.6)=0.48 (heterozygous)
48 are heterozygous
second part:
64 total
40 dominant/64 total= 0.625
24 heterozygous/64=0.375
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About 0.04% of the population of the United States has cystic fibrosis. Cystic fibrosis is a recessive disorder, so only people with a pair of alleles for this disorder are affected. What percentage of the population are carriers for this disease and what percentage don't carry even one allele for this disease?
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q²=0.0004
q=0.02 so p=0.98 so p²=0.9604
0.9604 + 2pq + 0.0004=1
2pq=0.0392
96.04% do not carry any alleles for disease
3.92%= carriers
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The idea put forward by Lamarck, which stated that organisms could pass on to their offspring physical changes that the parents developed during their own lifetimes, is known as
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inheritance of acquired characteristics
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Which of the following is one of the main points of Darwin's theory of evolution?
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Contemporary species share a common descent.
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T/F: Evolution is rapid and discontinuous.
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FALSE; it's gradual and continuous over long periods of time
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Which of the following is a basic requirement for natural selection to be an effective evolutionary force?
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A population exhibits some genetic variability.
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In Africa, there is a species of bird called the yellow-throated longclaw. It looks almost exactly like the meadowlark found in North America, but they are not closely related. This is an example of
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convergent evolution
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Which of the following is an INCORRECT statement about mutation?
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Mutations that are favored by selection are more likely to occur. (this is wrong)
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For cockroaches to have rapidly evolved resistance to an insecticide...
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some cockroaches must have had a mutation, causing them to be resistant to the ingredients
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Behavioral geneticists have found that the ability of house mice to squeak is determined by a single gene. If squeaky mice are more likely to be dropped by startled predators...
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the mouse population will consist of more and more squeakers over time since the non-squeakers will be eaten by predators
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What contribution(s) did Darwin make to science?
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Darwin recognized and described the process of natural selection and the pattern of evolution.
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You are a biologist studying a natural population of mice, and you observe that, in one area, the proportion of darker-colored mice is greater than the proportion of lighter-colored mice. In another area, the opposite is true. You find that only the area with more dark mice has predators. Therefore, you hypothesize that darker mice are favored in areas with predators, perhaps because they are more difficult to see. If your hypothesis is true, what would you expect to happen in the few generations after predators are introduced to an area with a population of mice that previously did not have predators?
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The proportion of darker-colored mice will increase
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Four postulates of natural selection?
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differential survival or reproduction, selection, variation among individuals in a population, heritable variation
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All organisms share the same genetic code. This commonality is evidence that..
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all organisms are descended from a common ancestor
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Which of the following lines of evidence support(s) the idea that evolution occurs?
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the fossil record, genetic and biochemical analysis, comparative anatomy and embryology, and natural selection
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Which of the following would be considered to be an example of analogous structures?
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superficially similar structures in unrelated species
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Antibiotic prescriptions normally specify that one take the entire course of treatment, such as a fixed number of pills, rather than simply taking the medicine until one feels better. In terms of evolution, why is this beneficial?
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Bacteria carrying slight resistance will be killed by the full course but will persist with a lesser dose. Natural selection will favor the slightly resistant forms if you do not complete the entire course of the antibiotic.
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Biologists have shown that some species of fish have genetic variation in their tendency to bite an angler's bait and hook. In professional bass fishing tournaments, all fish caught are returned to the water; therefore,...
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no change in catching success should occur
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In the United States today, about half of the corn crop is genetically engineered with a protein that is toxic to corn borers, an insect pest of corn. Which of the following conditions is necessary for the corn borer to evolve resistance to the toxic protein?
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The corn borer must have heritable variation in the resistance to the toxic protein. The resistant corn borers must survive better or reproduce more than nonresistant corn borers.
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Biologists have shown that some species of fish have genetic variation in their tendency to bite an angler's bait and hook. With repeated fishing and harvesting of caught fish...
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catching fish should become more difficult
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What is the Hardy-Weinberg principle?
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a model of population genetics that shows that evolution will occur if even one of the conditions of the principle is violated
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Which of the five conditions of the Hardy-Weinberg principle describes how new alleles can enter a population?
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mutations
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Mutations....
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provide the basic "raw material" for evolution
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Gene flow makes populations more...
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genetically similar; If two populations share alleles through gene flow, they are more likely to remain genetically similar.
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Which of the following is characterized by random changes in allele frequencies?
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genetic drift
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When alleles increase in frequency because they allow the organism to better survive and reproduce in its environment, this is a result of
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natural selection
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The process by which two species evolve adaptations in response to one another, such that evolutionary change in one species produces an evolutionary change in the other, is called..
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coevolution
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Which of the following selective processes did Darwin suggest to explain the evolution of the conspicuous structures and courtship behaviors that male animals use to attract a mate?
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sexual selection
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An equilibrium population..
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does not evolve
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In a mainland bird population, most individuals are black in color, and gray is a rare variation. A small group of these birds is carried by strong winds to a distant island, where they establish a new population. After three generations, the gray phenotype is very common. What is most likely to be responsible for this?
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founder effect
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Natural selection acts through predation against banded water snakes on certain Lake Erie islands, favoring the uniformly light-colored snakes. The banded form is very common on the nearby mainland. And yet banded snakes are maintained in the island populations and not eliminated completely. This is probably due to,.,,
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gene flow
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The Hardy-Weinberg equilibrium represents an idealized, evolution-free population in which the allele frequencies and genotype frequencies will not change over time. In order for this to happen, five conditions must be met. Suppose that one of the conditions was violated—the population was very small. In this situation, the evolution would probably be due to
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genetic drift
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Genetic drift will tend to ___ genetic variability within populations, but ____ genetic variability between populations.
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decrease; increase
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A large population of birds on an island has a color distribution of 80% green birds and 20% yellow birds. Most of the population is killed by an unusually strong storm; color distribution of the survivors is 60% green birds and 40% yellow birds. The change in the color distribution is probably due to..
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genetic drift
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T/F: Random mating will NOT change allele frequencies in a population
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TRUE; gene flow can change it however
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In populations of snowshoe hares, light coat color is favored over dark coat color. This is because light coat color provides camouflage during the winter snow, when avoiding the predatory lynx is critical to survival. Which of the following is a living component of the environment of the hare?
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the lynx; snow is a nonliving component
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Black-bellied seedcrackers have either small beaks (better for eating soft seeds) or large beaks (better for hard seeds). There are no seeds of intermediate hardness; therefore, __________ acts on beak size in seedcrackers.
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disruptive selection
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Goldenrod gall flies lay their eggs in the goldenrod plant. The fly larvae cause the plant to form a gall, a swollen growth of plant tissue. Large galls tend to be pecked open and their larvae eaten by birds. Small galls are more frequently parasitized by tiny wasps, whose larvae eat the fly larva and take over the gall. This complex situation implies that __________ is acting on gall size.
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stabilizing selection
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Body size varies among individuals in a species of lizard in the genus Aristelliger. Small lizards have a hard time defending a territory, and thus mating, but large lizards are more likely to be preyed on by owls. Therefore, natural selection favors individuals with an average body size. This is an example of
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stabilizing selection
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Long necks make it easier for giraffes to reach leaves high on trees, while also making them better fighters in "neck wrestling" contests. In both cases, __________ appears to have made giraffes the long-necked creatures they are today.
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directional selection
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What phrase best describes the concept of natural selection?
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reproductive success
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If a population is undergoing natural selection, then..
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it is becoming more adapted to its environment
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Biologists sometimes combine two groups previously considered different species into the same species because
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they may be physically divergent, but they are found to interbreed in nature
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Which of the following is most characteristic of populations of DIFFERENT species?
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Fertile members from two different populations cannot mate together and produce fertile offspring.
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Under the biological species concept, the main criterion for identifying a species is
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reproductive isolation
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Incompatibilities that prevent mating between species are called
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premating isolation mechanisms
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A female fig wasp will carry fertilized eggs from a mating that took place within a fig, and then find another fig of the same species, enter it, lay eggs, and die. Her offspring will then hatch, develop, and mate within the fig. Because each species of fig wasp reproduces only in its particular species of fig, each wasp will only have the opportunity to mate with other wasps of its species. This would be considered
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ecological isolation; The wasps are physically able to get to other wasps, so this isn't a geographical barrier, but an ecological one.
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Incompatibilities that prevent the formation of vigorous, fertile hybrids between species are called
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postmating isolation mechanisms
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A likely group of animals in which to look for cases of sympatric speciation would be
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parasitic intestinal worms
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What is NOT an example of speciation?
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A small group from a large mainland population colonizes a remote island.
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Which species is at LEAST risk of extinction?
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The species is composed of one large, continuous, genetically variable population. Its healthy.
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Which of the following is true of the biological species concept?
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Members of the same species must be able to reproduce and have fertile offspring.
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Why is appearance a poor characteristic to use when determining whether two organisms are of the same (or different) species?
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Both organisms of differing appearance may still be able to interbreed and organisms with similar appearance may have mating incompatibilities.
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One ecological barrier that prevents populations from interacting during critical points in their life cycle is
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mating; Two emerging species could feed together, but remain reproductively isolated.
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In many species of fireflies, males flash to attract females. Each species has a different flashing pattern. This is probably an example of
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premating isolation
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Bishop pines and Monterey pines coexist in nature. In the laboratory they produce fertile hybrids, but in the wild they do not interbreed. This is because the two species release pollen at different times of the year. This is an example of
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temporal isolation
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Which of the following ecological barriers was a major factor in the evolution of Rhagoletis pomonella?
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the preference of different females for ovipositing (laying eggs) on different fruits
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A new variety of Rhagoletis pomonella has been discovered infesting cherry trees. What should cherry-producing farmers be told?
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The flies have switched from apple trees and may be evolving into a new "cherry only" species by sympatric speciation.
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What would PREVENT genetic divergence, and thus speciation, from occurring?
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Mating of members of two populations is successful.
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What is a requirement for speciation to occur?
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Populations must be isolated from each other, the isolated populations must become genetically distinct from one another, and exchanges of genetic information must be restricted between populations.
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Genetic drift can contribute to allopatric speciation if...
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one of the separated populations is small enough
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Populations of two species living in the same areas (for example, chorus frogs and wood frogs living in the same ponds of Ohio woodlots) are said to be..
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sympatric
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The rapid speciation of Darwin's finches on the Galapagos Islands is an example of..
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adaptive radiation-the rapid proliferation of species adapting to various habitats after a colonization event by an ancestral species.
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What is the first step in the process of allopatric speciation?
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geographic isolation
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Which of the following is/are likely to promote sympatric speciation?
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both ecological isolation and chromosomal aberrations
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A mechanism by which many plants, but few animal species, have evolved sympatrically is
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polyploidy
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If a haploid egg from a diploid plant is fertilized by a haploid sperm from a diploid plant, and the fertilized egg duplicates its chromosomes but does not divide into two cells, the resulting cell may then divide normally, producing an individual plant that will be
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tetrapoloid; There will be four sets of chromosomes in each cell
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What is the LEADING cause of extinction?
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habitat change/destruction
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T/F: normal changes in the weather will cause extinction.
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FALSE