Evolution Flashcards
(115 cards)
1
Q
Evolution
A
● Change in allelic frequencies in a population
2
Q
Radiometric dating
A
● Based on the dcay of radioactive isotopes and half-life
● However, there is inadquate rock or fossils available to measure
3
Q
Paleomagnetic dating
A
● Uses the fact that Earth’s magnetic poles shift and sometimes even reverse
● These changes are recorded in rock layers
4
Q
Fossil record
A
● Reveals the existence of species that have become extinct or have evolved into other species
● Radiometric dating and half-life are used to measure the age of fossils
5
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Comparative anatomy
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● The study of different structures contributes to scientists’ understanding of the evolution of anatomical structures and of evolutionary relationships
6
Q
Homologous structures
A
● Have a common origin and reflect a common ancestry
● The function might vary
● Ex) Wing of a bat, the lateral fin of a whale, and hte human arm
7
Q
Analogous structures
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● Serve the same function
● Similarity is superficial and reflects an adaptation to similar environments, not descnet from a recent common ancestor
● Ex) Bat’s wing and a fly’s wing
8
Q
Vestigial structures
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● Evidence that structures have evolved
● Ex) appendix–a vestige of a structure needed when human ancestors ate a very different diet
9
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Comparative biochemiestry
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● Organisms that have a common ancestor will have common biochemical pathways
● The more closely related the organisms are to each other, the more similar their biochemistry is
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Comparative embryology
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● Closely related organisms go through similar stages in their embryonic development
● Ex) All vertebrate embryos go through a stage in which they have gill pouches on the sides of hteir throats
- In fish, the gill pouches develop into gills
- In mammals, they develop into eustachian tubes in the ears
11
Q
Molecular biology
A
● Since all aerobic organisms contain cells that carry out aerobic cell respiration, they all contain the polypeptide cytochrome c
● A comparison of the amino acid sequence of cytochrome c among diferent organisms hows which organisms are most closely related
● The cytochrome c in human cells is almost idntical to that of our closest relatives, the chimpanzee and gorilla, but differs from that of a pig
12
Q
Biogeography
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● According to the theory of plate tectonics, continents and oceans rest on giant plates of the Earth’s crust that float on top of the hot mantle
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Continental drift
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● The slow, continuous movement of the plates
● Causes mountains to form as plates collide
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Convection currents
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● Responsible for continental drift
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Pangea
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Supercontinent that include all the land masses together
16
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Aristotle
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● Spoke for the ancient worl with his theory of Scala Natura
17
Q
Scala Natura
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● All life-forms can be arranged on a ladder of increasing complexity, each with its own allotted rung
● The species are permaent and do not evolve
● Humans are at the pinnacle of this ladder of increasing complexity
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Q
Carolus Linnaeus/Carl von Linne
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● Specialized in taxonomy
● Belived that scientists should study life and htat a classification system would reveal a divine plan
● Developed the naming system binomail nomenclature
19
Q
Cuvier
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● Studied fossils and realized that each stratum of earth is characterized by different fossils
● Belived that a series of catastrophes was responsible for the changes in the organisms on earth and was a strong opponent of evolution
20
Q
James Hutton
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● One of the most influential geologists of his day
● Published his theory of gradualism
21
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Gradualism
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● Stated that the earth had been molded, not by sudden, violent events, but by slow, gradual change
● They were based on the idea that the earth had a very long history and that change is the normal course of events
22
Q
Lyell
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● Stated that geological change results from slow, continuous actions
● His text, Principles of Geology, was a great influence on Darwin
23
Q
Lamarck
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● Ideas of inheritance of acquired characteristics and use and disuse
24
Q
Inheritance of acquired characteristics/use and disuse
A
● Individual organisms change in response to their environment
● The giraffe developed a long neck because it ate leaves of hte tall acacia tree for nourishment and had to stretch to reach them
● Then animals stretched their necks and passed the acquired trait of an elongated neck onto their offspring
25
Wallace
● Published an essay discussing the process of natural selection identical to Darwin's
● Many people credit Wallace, along with Darwin, for hte theory of natural selection
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Darwin
● Worked out his theory of natural selection or descent with modification as the mechasniism for how populations evolve
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Darwin's theory of natural selection
● Generally states that natural selection is a major mechanism of evolution
● It acts on phenotypic variation in populations
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Selective advantage
● Phenotype or traits that allow the organism to become more fit in the environemnt comparin to individuals in the same population
● Often results in directional selection
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Directional selection
● One phenotype replaces another in the genepool
● One extreme end is favoured
● Can produce raid shifts in allelic frequencies
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Stabilizing selection
● Sometimes called purifying selection
● Eliminates the extremes and favors the more common intermediate forms
● Many mutant forms are weeded out in this way
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Disruptive/diversifying selection
● Increases the extreme types in a population at the expense of intermediate forms
● May result in balanced polymorphism
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Balanced polymorphism
● The presence of two or more phenotypically distinct forms of a tait in a single popualtion of a species
● Each morph is better adapted in a different area, but both varieties continue to exist
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Sexual selection
● Selection based on variation in secondary sexual characcteristics related to competing for and attracting mates
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Sexual dimorphism
Differences in appearance between males and females
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Artificial selection
● Humans breed plants and animals by seeking inidividuals with desired traits as breeding stock
- Racehorses are bred for speed, and laying hens are bred to produce more and larger eggs
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Geographic variation
● Two different varieties of a species continue to exist in two different regions
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North-south cline
● The variation in appearance is due to differences in northern and southern environments
● A type of geographic variation
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Cline
Graded variation in the phenotype of an organism
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Sexual reproduction
● Provids variation due to the shuffling and recombination of alleles during meiosis and fertilization
- Independne tassortment of chromosomes
- Crossing over
- Random fertilization
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Independent assortment of chromomes
● During metaphase I
| ● eulsts in the recombination of unlinked genes
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Corssing over
● Exchange of genetic material of homologous chromoosmes and occurs during meiosis I
● Produces individual chromosomes that combine genes inherited from two parents
● In human, two ro three crossover events occur per homologous pair
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Random fertilization
● One ovum by one sperm out of millions results in enormous variety among the offspring
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Outbreeding
● Mating of organisms within one species that are not closely related
● opposite of inbreeding--mating of closely related individuals
● Maintinas both variation within a species and a strong gene pool
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Diploidy
● The 2n condition
● Maintinas nad hides a huge pool of alleles that may be harmful in teh present environment but that could be advantageous when conditions change in the future
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Heterozygote advantage
● Preserves multiple alleles in a population
● Phenomenon in which the hybrid individual is selected for because it has greater reproductivve success
● The hybrids are sometimes better adapted than the homozygotes
● It is defined in terms of genotype not phenotype
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Frequency-Dependnent selection
● aka minority advantage
| ● This acts to decrease the frequency of the more common phenotypes and increase hte frequency of the less common ones
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Search image
Standard representation of prey that enables predators to hunt a particular kind of prey effectively
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Evolutionary neutral traits
● Traits that seem to have no selective advantage
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Genetic drift
● Change in the gene pool due to chance
● Fluctuation in frequency of alleles from one generation to another and is unpredictable
● Tends to limit diversity
● Two examples are bottleneck effect and founder effect
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Bottleneck effect
● Natural disasters such as fire, earthquake, and flood reduce the size of a population unselectively, resulting in a loss of genetic variation
● The resulting population is much smaller and not representative of the original one
● Certain alleles may b under or overrepresented compared with the original population
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Founder effect
● When a small population breaks away from a larger one to colonize a new area, it is most likely not genetically representative of the original larger population
● Rare alleles may be overrepresented
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Gene flow
● The movement of alleles into or out of apopulation
● Can occur as a result of the migration of fertile individuals or gametes betwen population
● Ex) pollen from one valley can be carried by the wind across a moutnain to another valley
● Tneds to increase diversity
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Mutations
● Changes in genetic material and are the raw material for evolutionary change
● Increase diversity
● A single point mutation can introduce a new allele into a population
● Although mutations at one locus are rare, the cumulative effect of mutations at all loci in a population can be significant
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Nonrandom mating
● Individuals choose their mates for a specific reason
| ● The selection of a mate serves a eliminate the less-fit individuals
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Natural selection
● Major mechanism of evolution in any population
● Those individuals who are better adapted in a particular environment exhibit better reproductive success
● They have more offspring that survive and pass their genes on to more offspring
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Hardy-Weinberg equilibrium
● Characteristics of stable populations
| ● When a population achieve equilibrium, the allelic frequencies do not change
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Hardy-Weinberg equation
● Enables us to calculate frequencies of allels in a population
● p stand for the dominant allel
● q stand for the recessive allele
● p2 + 2pq + q2 = 1 or p + q = 1
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Species
● A population whose memebrs have the potential to interbreed in nature and produce viable, fertile offspring
- Lions and tigers can be induced to interbreed in captivity but would not do so naturally--they are considered separate species
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Speciation
● One group of genes becomes isolated from antoher to begin a separate genetically udner the pressure of different selective forces in different environments
● IF enough time elapses and differing selective forces are sufficiently great, the two populations may become so different that interbreeding would not naturally occur
● At this point, speciation have taken place
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Allopatric speciation
● Caused by geographic isolation
| - Separation by mountain ranges, canyons, rivers, lakes, glaciers, altitude, or longitude
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Sympatric speciation
● Udner certain circumstances, speciation may occur without geographic isolation
● Examples are polyploidy, habitat isolation, behavioral isolation, temporal isolation and reproductive isolation
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Polyploidy
● Condition where a cell has more than two complete sets of chromosomes
● It is common in plants and can occur natural or through breeding
● It results from nondisjunction during meiosis when gametes with the 2n chromosome number are fertilized by another abnormla (2n) gamete, resulting in a daughter cell with 4n chromosomes
● Plants that are polyploid cannot breed with others of the same species that are not polyploid and are functionally isolated from them
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Habitat isolation
● Two organisms live in the same area but encounter each other rarely
● Two species of one genus of snake can be found in the same geographic area, but one inhabits the water while the other is mainly terrestrial
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Behavioral isolation
● Different behaviors, especially during mating season, resulting in two species
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Temporal isolation
● Temoral refers to time
● A flwoering plant colonizes a region with areas that are warm and sunny and areas that are cool and shady
● Flowers in the regions that are warmer become sexually mature sooner thatn flowers in the cooler areas
● This separates flowers in the two different environments into two separate populations
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Reproductive isolation
● Closely related species may be unable to mate because of a variety of reasons
● Differences in teh structuer of genitalia may prevent insemination
● Difference in flower shape may prevent pollination
● Prezygotic barriers and postzygotic barriers
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Prezygotic barriers
● Things that prevent mating
● Ex) A small male dog and a large female dog cannot mate because of the enormous size differences between the two animals
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Postzygotic barriers
● Things that prevent hte production of fertile offspring, once mating has occured
● Ex) A particular zygot is not viable
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Divergent evolution
● Occurs when a population becomes isolated from the rest of hte species, becomes exposed to new selective pressures, and evolves into a new species
● All the examples of allopatric and sympatric speciation are examples of divergent evolution
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Convergent evolution
● When unrelated species occupy the same environment, they are subjected to similar selective pressures and show similar adaptations
● The classic example is the whale, which has the streamlined appearance of a large fish because the two evovled in teh same environment
- The underlying bone structuer of the whale, however, reveals,= an ancestry common to mammals, not fish
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Parallel evolution
● Describes two related species that have made similar evolutionary adpatations after their divergence from a common ancestor
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Coevolution
● Reciprocal evolutionary set of adaptations of two interacting species
● All predator-prey relationships are examples
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Adaptive radiation
● Emergence of numerous species from a common ancestor introdcued into an environment
● Each enwly emerging form specializes to fill an ecological niche
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Gradualism
● Theory that organisms descend from a common ancestor gradually, over a long period of time, in a linear or branching fashion
● Big changes occur by an accumulaion of many small ones
● According to this theory, fossils should exist as evidence of every stage in the evolution of every species with no missing links
● However, the fossil record is at odds with this theory because scientists rarely find transitional forms or missing links
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Punctuated equilibrium
● The favored theory of evolution
● Proposes that new species appear suddenly after long periods of stasis
● A new species changes most as it buds from a parent species and then changes little for the rest of its existence
● The sudden appearance of the new species can be explained by the allopatric model of speciation
- A new species arises in a different place and expands its range, outcompeting and replacing the ancestral species
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Anaerobic heterotrophic prokaryotes
● The first cells on earth
| ● Simply absorbed organic moleucles from the surrounding primordial soup to use as a nutrient source
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Theory of endosymbiosis
● States that mitochondria and chloroplasts were once free-living prokaryotes that took up residence inside larger prokaryotic cells
● The mutually beneficial symbiotic relationship worked out so well that it became permanent
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What do you determine the absolute age of rocks?
Measure by radiometric dating
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What do you determine the relative age of rocks?
Study sedimentary rock layers and the fossils within them
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What are some evidences for evolution?
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● Fossil record
● Comparative anatomy
● Comparative biochemistry
● Comparative embryology
● Molecular biology
● Biogeography
```
81
What do fossil records tell us about evolution?
● Prokaryotes were hte first organisms to develop on earth and they are hte oldest fossils
● Paleontologists have discovered many transitional forms tha link older fossils to modern specidies
- Eohippus to the modern hose, Equus
- Archaeopteryx is a fossil that links repties and birds
● All the organisms alive today are only a tiny fraction of all the organisms that ever lived
82
How did continental drift change the distributions of life on Earth?
● Marsupials are located almost exclusively in Australia, while other continents are home to eutherians, the true placental mammals
● Fossil evidence suggests that maarsupials originated in what is now Asia and reached Australia via South America and Antarctica while the continents were still jioned
● When the continents broke apart and moved to different climates, Australia was set afloat like a giant raft, carrying both marsupials and eutheirans
● THe marsupials diversified, filling every available niche while the true placental mammals, which were not adapted to the Australian environment and climate, went extinct
83
What are the five things stated in Darwin's teory of natural selection?
1. Populations tend to grow exponentially, overpopulate, and exceed their resources
- Organisms give birth to more offsprings than that can actually survive
2. Overpupolation results in competition and a struggle for existence
- One that survives passes their genes down
3. In any population, there is variation and an unequal ability of individuals to survive and reproduce
4. Only the best-fit individuals survive and get a pass on their traits to offspring
5. Evolution occurs as advantaeous traits accumulate in a population
- No individual organism changes in response to pressure from the environment
- Rather, the frequency of an allel wthin a population changes
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What's an example of Darwin's theory regarding to giraffe?
● Ancestral giraffes were short-necked animals although neck length varied from individual to individual
● As the population of animals competing for the limited food supply increased, the taller individuals had a better chance of surviving than those with shorter necks
● Over time, the proportion of giraffes in the population with longer necks increased until only long-necked giraffes existed
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What are the five types of selection?
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● Stabilizing
● Diversifying
● Directional
● Sexual
● Artificial
```
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What give rise to directioanl selection?
Changing environmental conditions
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What is an example of directional selection relating to moths?
● In the past, most peppered moths were light; a few individuals were found to be dark
● With increasing industrialization, smoke and soot polluted the environment, making all the plants and rocks dark
● All moths in the industrialized regions became dark because dark moths were camouflaged and had the selective advantage
- Whereas before industrializing, white moth had the advantage
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What is an example of directional selection relating to bacteria?
● Soon after hte discovery of antibiotics, bacteria appeared htat were resistant to these drugs
● The genes for antibiotic resistance are carried on plasmids, small DNA molecules, which can be transferred from one bacterial cell to another and which can spread the mutation for antibiotic resistance very rapidly
● THe appearance of antibiotics themselves deso not induce mutations for resistance; it merely selects against susceptible bacteria by killing them
● Since only resistnat individuals survive to reporduce, the next generation will all be resistant
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What are two examples of stabilizing selection?
● In humans, stabilizing selection keeps the majority of birth weights in the 6-8 pound range
- for babies much smaller and much larger, infant mortality is greater
● In Swiss starlings, genotypes that lead to a clutch size (the umber of eggs a bird lays) of up to five will have more surviving young than birds of the same species htat lay a larger or smaller number of eggs
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What are the examples of sexual selection?
● In males, the evolution of horns, antlers, large stature, and great strength are the result of sexual selection
- Male elephant seals fight for supremacy of a haren that may conssit of as many as fifty females
- In baboons, long canines are important for male-male competition
● In many species of birds, the females are colored in a way to blend in with their surroundings, thus protecthing them an their young
- The males have bright plumage because they must compete for the attention of the females
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Why is variation in a population important?
● Allowing the population to evolve as the environment changes
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What are the eight mechanisms that preserve diversity or variation in a gene pool or population?
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● Balanced polymorphism
● Geographic variation
● Sexual reproduction
● Outbreeding
● Diploidy
● Heterozygote superiority
● Frequency-dependnet selection
● Evolutionary neutral traits
```
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What is an example of balanced polymorphism?
● The shells of one genus of land snail exhibit a wid range of colors and banding patterns
● Banded smails living on dark, mottled groundare less visible than unbanded ones and therefore are preyed upon less frequently
● In areas where hte background is fiarly uniform, unbanded snails have hte selective advantage
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What is an example of geographic variation especially north-south cline?
● Rabbits in the cold, snowy northern regions are camouflaged with white fur and have short ears to conserve body heat
● Rabbits living in warmer, southern regions hae mottled fur to blend in with surrounding woodsy areas and long ears to radiate off excess body heat
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Why does inbreeding weaken the gene pool?
● Interbreeding between organisms that are closely related tend to have a higher chance of detrimental recessive traits in homozygous recessive individuals
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How does lion prevent inbreeding?
● The dominant male of a pride chases away the young maturing males before they become sexually mature
● Ensures that these young males will not inbreed with their female siblings
● These young male lions roam the land, often over great distances, looking for another pride to join
- If one can successfully overthrow the king of another pride, he will inseminate all the females of htat new pride and develop his own lineage
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What is an example of heterozygot advantage?
● Sickle cell anemia in West Africa
● People who are hybrid (Ss) for the sickle cell trait have normal hemoglobin and do not suffer from sickle cell disease
- They are resistant to malaria, which is endemic in Africa
● Those who are homozygous (ss) are at a greater disadvantage because htey have abnormal hemoglobin and suffer from an amay die of sickle cell disease
● Those with homozygous normal hemoglobin (SS) are susceptible to and may die of malaria
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What's an example of frequency-dependnet selection?
● Predators dvelop a search image
● If the prey individuals differ, the most common type will be preyed upon disproportionately while the less common individuals will be preyed upon to a lesser extent
● Since these rare individuals have the selective advantage, they will become more common for a time, will lost their selective advantage, and will eventually be selected against
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What is an example of evolutionary neutral traits?
● Different blood types in human
| - Scientists do not understand where they evolved from or why they have remained in the human population
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What are the five things that cause evolution?
```
● Genetic drift
● Gene flow
● Mutations
● Nonrandom mating
● Natural selection
```
101
What is an example of the bottleneck effect about Jews?
● The high rate of Tay-Sachs disease among Eastern European Jews is attributed to a population bottleneck eperienced by Jews in the Middle Ages
● During that period, many Jews were persecuted and killed, and the popualtion was reduced to a small fraction of its original size
● Of the individuals who remained alive, there happen to have been a disproportionate percentage of people who carried the Tay-Sachs gene
● Scine then, the incidence of the trait remained unusually high in that population
102
What is an example of the bottleneck effect about elephant seal?
● THe norhtern elephant seal was hunted almost to extinction along the California coast
● Since then, when the seal was placed udner government protection, the population has increased ot about 35,000; all are descendants from that original group and have little genetic variation
103
What is an example of the founder effect?
● All the colonists descended from a small group of settlers who came to the US from Germany in the 1770s in Pennsylvania
● Apparently one or more of the settlers carried the rare but dominant gene for polydactyly, having extra fingers and toes
● Due to the extreme isolation and intermarriage of the close community, this population now has a high incidence of polydactyly
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What is an example of nonrandom mating?
● Snow geese exist in two phenotypically distinct forms, white and blue
● Blue snow geese tend to mate with blue geese, and white geese tend to mate with white geese
● If, for some reason, the blue geese became mroe attractive and both blue and hwite geese began mating with only blue geese, the population would evolve quickly, favoring blue geese
105
What five things must be true if the population is stable?
1. The population must be very large
- A small change in the gene pool willbe diluted by the sheer number of individuals and no change in the frequency of alleles will occur
2. The population must be isolated from other populations
- There must be no migration of organisms into or out of the gene pool because that could alter allelic frequencies
3. There must be no mutations in the population
- A mutation in the gene pool could cause a change in allelic frequency by introducing a new allele
4. Mating must be random
- If individuals select mates, then those individuals that are better adapted will have a reproductive advantage and the population will evolve
5. No natural selection
- Natural selection causes chagnes in relative frequencies of alleles in a gene pool
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What may cause speciation?
Anything that fragments a population and isolates small gropus of individuals may cause speciation
107
What is an example of behavioral isolation about fish?
● Sticklebacks, small saltwater fish, have elaborate mating behavior
● At breeding time, in response to increased sunlight, the males change in color and develop a red underbelly
● The male builds a nest and courts hte female with a dance that triggers a complex set of movements between the partners
● If neither partner fails in any step of the mating dance, no mating occurs and no young are produced
108
What is an example of behavioral isolation about fireflies?
● Male fireflies of various species signal to females of their kind by blinking the lights on their tails in a particualr pattern
● Females respond only to characteristics of their own species, flashing back to attract males
● If, for any reason, the female does not respond with the correct blinking pattern, no mating occures
● The two animals become isolated from each other
109
What are the five patterns of evolution?
```
● Divergent
● Convergent
● Parallel
● Coevolution
● Adaptation radiation
```
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What is an example of parallel evoluation?
● The marsupial mammals in Australia and the placental mammals of North America
● There are striking similarities between some placental mammals like the gray wolf of NA and the marsupial Tasmanina worlf of Austarlia because they share a common ancestor and evovled in similar environments
111
What is an example of coevolution?
● The relationship between the monarch butterfly and milweek plant
● Milkweed platn contains poisons that deter herbivores from eating them
● The butterfly lays its eggs in the milkweed platn and when the larvae (caterpillars) hatch, they feed on the milkweed and absorb the poisonous from the plant
- They store the poison in their tissues
● This poison, which is present in the adult butterfly, makes the butterfly toxic to any animal who tries to eat it
● THe butterfly exhibits bright conspicuous waning colors that der predators
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What are the two modern theories of evolution?
● Gradualism
| ● Punctuated equilibrium
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What gas did ancient atmosphere consist of?
```
● CH4
● NH3
● CO
● CO2
● N2
● H2O
● No O2
```
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Why wasn't oxygen in the ancient atmosphere?
● Oxygen is corrosively reactive moleculre that will react with and degrade organic molecules
● Wihtout them, organic molecules coudl form and remain
115
What are the three points to prove that mitochondria and chloroplasts are endosymbionts?
● Chloroplasts and mitochondria have their own DNA
● DNA is more like prokaryotic DNA than eukaryotic DNA
- It is not wrpaped with histones
● These organelles have double membrane
- The inner one belongs to the symbiont; hte outer one belongs tot he ost plasma membrane
- The theory states that the chloroplast and mitochondria were taken up by thehost cell by some sort of endosymbiosis process, such as phagocytosis
