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Speciation and Evolutionary Processes, Exams of Advanced Education

Harvard University Advanced Education

A comprehensive overview of various speciation and evolutionary processes, including anagenesis, cladogenesis, spatial/geographic isolation, ecological isolation, temporal isolation, behavioral isolation, mechanical isolation, gametic incompatibility, hybrid inviability, hybrid sterility, and hybrid breakdown. It also discusses the concepts of extrinsic and intrinsic barriers, nodes in a phylogenetic tree, monophyletic, paraphyletic, and polyphyletic clades, reinforcement, sympatric speciation, mass extinctions, the history of oxygen, the effects of human hunting, and the cambrian explosion. A wide range of topics related to evolutionary biology and speciation, making it a valuable resource for students and researchers in the field.

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BIS 2b Final Exam (All Material)

Questions With 100% Correct Answers |

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ecology - Correct Answer-study of organisms + physical environment, organisms +

organisms

evolution - Correct Answer-change over time in the properties of populations

assumption of total number of species - Correct Answer-- 1.8 million described/identified

- 5 to 100 million estimated

- through extrapolating of known info (flora and fauna in Great Britain): 4.9 million

insects, maybe 10 million species total

Terry Irwin - Correct Answer-sampled species of beetles in a certain tropical forest tree;

came to the conclusion of 30 million tropical arthropod species; calculation was

completely wrong but is testable and can be refined

species-area relationship - Correct Answer-S = cA^z

S: number of species

c: constant depending on taxonomic group

A: area

z: constant determining shape and slope of the curve

threats to biodiversity - Correct Answer-- habitat alteration and destruction

- harvesting, fishing

- climate change

- introduced species

biodiversity hotspot - Correct Answer-many endemic species (don't occur anywhere

else)

morphological species - Correct Answer-grouped based on similar physical appearance

PROS:

- practical

- simple

- reflects evolution (shared genes)

CONS:

- genetic variation within populations

- changes due to the environment (plasticity)

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ecology - Correct Answer-study of organisms + physical environment, organisms + organisms evolution - Correct Answer-change over time in the properties of populations assumption of total number of species - Correct Answer-- 1.8 million described/identified

5 to 100 million estimated
through extrapolating of known info (flora and fauna in Great Britain): 4.9 million insects, maybe 10 million species total Terry Irwin - Correct Answer-sampled species of beetles in a certain tropical forest tree; came to the conclusion of 30 million tropical arthropod species; calculation was completely wrong but is testable and can be refined species-area relationship - Correct Answer-S = cA^z S: number of species c: constant depending on taxonomic group A: area z: constant determining shape and slope of the curve threats to biodiversity - Correct Answer-- habitat alteration and destruction
harvesting, fishing
climate change
introduced species biodiversity hotspot - Correct Answer-many endemic species (don't occur anywhere else) morphological species - Correct Answer-grouped based on similar physical appearance PROS:
practical
simple
reflects evolution (shared genes) CONS:
genetic variation within populations
changes due to the environment (plasticity)

some species can have similar physical traits but have very separate evolutionary histories biological species - Correct Answer-groups of individuals actually or potentially capable of reproducing fertile offspring PROS:
clear bio / evolutionary meaning CONS:
difficult to apply in practice phylogenetic species - Correct Answer-similarities in phylogeny, but DNA can be considered morphology climate - Correct Answer-avg. and annual variation in temp. and precipitation in a given region over a long period of time
affects type of vegetation which affects which types of animals that live there (formation of different biomes) factors determining climate / Hadley cell patterns - Correct Answer-1. solar radiation

air circulation

driven by solar radiation and earth's rotation
sunlight strikes equator intensely and as you move away you get less heat
air rises in heated areas, cools as it rises, cool air holds less moisture --> precipitation
as warm air rises, it displaces air to the north and south, which gets very dry due to the high altitude and the heavy precipitation in warm areas, so deserts form at 30deg N and S surface wind patterns / Coriolis force - Correct Answer-result of moving air or water masses due to earth's spin
winds deflected to the L in S hemisphere, to the R in N hemisphere
our weather patterns in N hemisphere generally come from westerlies, which affect rainshadow due to the mountain ranges on the west coast ITCZ - Correct Answer-intertropical convergence zone where the N and S Hadley cells meet; zone of max heating
moves to different latitudes, meaning diff areas of the earth receive the max radiation from the sun at diff times of the year
during the equinoxes (spring, fall) the ITCZ is closest to the equator
during the summer solstice, the sun is hitting most directly in the N hemisphere so the ITCZ is farther north
during the winter solstice, the sun is hitting most directly in the S hemisphere so the ITCZ is farther south
ITCZ aligns with areas of mass rainfall surrounded by deserts (when referring to maps showing precipitation levels)

detrivore - Correct Answer-consume dead plant or animal matter (adaptations to subsist on low quality food) suspension feeder - Correct Answer-remove suspended particles from the water deposit feeder - Correct Answer-consume dead organic matter symbiont - Correct Answer-live in, with, or on another organism and obtain nutrition from that organism (their host) specialized vs. generalized feeding - Correct Answer-- trade offs for both

specialized organisms have access to resources that few do, but also have limited options
generalized organisms have balanced diets and reduced search cost, but high competition goals besides finding max energy intake per unit time - Correct Answer-- avoid predators
find mates
obtain specific micronutrients or vitamins greenhouse effect - Correct Answer-key to life on earth, but an increase in the greenhouse gases has caused an increase in temperature
CO2, N2O, and CH4 naturally present in the atmosphere, but when there is too much (manmade) they prevent heat from escaping into space and more is reemitted into earth different carbon isotopes - Correct Answer-fossil fuels are depleted in C14 since it has decayed over time (half life is about 5,730 years), so as fossil fuels are burned the concentration of C14 in the atmosphere decreases --> proof that global warming is human caused plant productivity vs CO2 - Correct Answer-- plants prefer to take up light isotopes, so they take up more C
still, plant growth is not enhanced by increased CO2 concentration; if it is, it's minor and temporary (Duke Forest experiment)
other limiting factors such as lack of nutrients or changes in precipitation
plant productivity will not counteract the negative impacts of carbon emission Liebig's Law of the Minimum - Correct Answer-production only occurs at the rate permitted by the most limiting factor (sunlight or water/nutrients) root to shoot ratio (tradeoff) - Correct Answer-- more roots, less shoots: obtain more water and N, less C
more shoots, less roots: obtain more C, less N and water

adaptation vs acclimation - Correct Answer-adaption is an evolutionary, genotypic change that occurs slowly over generations, while acclimation is a phenotypic change that can occur in an organism's lifetime and is usually reversible (snowshoe hare turning white in winter) thermal stress - Correct Answer-biochemical processes are often temp dependent, and enzymes can denature at extreme temps; maximal reaction rate occurs at an intermediate temp endotherms vs ectotherms - Correct Answer-endotherms primarily determine body temp with metabolic energy (internally generated heat)

high benefit, high cost: only works when fuel for producing heat is predictably abundant ectotherms primarily determine body temp with external factors evaporative cooling - Correct Answer-common way to regulate heat, but causes dehydration (tradeoff) transpiration - Correct Answer-plants release water from stomata to prevent overheating plant adaptations to reduce water loss / heat stress - Correct Answer-- waxy covering on leaves to reflect sunlight
small, vertical leaves
low SA/V ratio
wilting reduces SA and heat
shedding leaves in dry periods
reduced stomatal density or opening
deep tap roots
storage of water (succulent stems, bulbous roots) TRADEOFF: reducing water loss (closing stomates) also reduces rate of photosynthesis (CO2 can't enter) C3 photosynthesis - Correct Answer-CO2 combines with rubisco to form PGA in the mesophyll cells
rubisco has a weak affinity for CO2, so stomates have to stay open for a long time and much water is lost C4 photosynthesis - Correct Answer-CO2 is initially fixed by PEP carboxylase in the mesophyll cells, then is transported in a temporarily fixed state to the bundle sheath cells to be fixed by rubisco to form PGA
PEP carboxylase grabs CO2 more efficiently, so C4 plants keep stomates open for less time
costly since additional enzyme systems and anatomical structures are needed
inefficient at low light and have a higher temp optima than C3 plants

survivorship curves - Correct Answer-- type I: low mortality until later stages of life (humans)

type II: probability of surviving independent of age (birds)
type III: high juvenile mortality but low adult mortality, many die early but those who survive have low mortality (trees) Ro - Correct Answer-net reproductive rate: avg. number of offspring produced by an individual during its entire lifetime (product of survival and fecundity, summed over all age classes --> Σlxmx) can never be negative if Ro<1, population is decreasing if Ro=1, population stays the same if Ro>1, population is increasing typological/essentialist species concept - Correct Answer-- organisms tend toward some ideal type for their species
deviations from the ideal type are mistakes (no evolution) variational species concept - Correct Answer-- there is no "ideal" type
variation is the norm, and all species are variants
evolution is possible as different variants increase or decrease in frequency
each type is specialized based on their role (tradeoffs dominate) Aristotle's scala naturae - Correct Answer-based on religious pre-ordained concepts of order, all forms are stuck on a step and there is no evolution God -- Angels -- Demons -- Humans -- Animals Al-Jahiz - Correct Answer-pre-Darwinian scholar who understood environmental influences on traits, the struggle for existence, and differential survival / reproduction Al-Biruni - Correct Answer-pre-Darwinian scholar who understood the relationship between overproduction and competition, but didn't understand evolution and instead proposed the existence of a divine creator Ibn Khaldun - Correct Answer-pre-Darwinian scholar who wrote that the higher stage of man is reached from the world of monkeys; understood the concept of evolution but not the actual process Alexander von Humboldt - Correct Answer-understood patterns of global climate zones and distributions of plants and animals through global exploration (biomes and biogeography)

Mary Anning - Correct Answer-English paleontologist who found through layers of fossils that organisms change over time Georges Cuvier - Correct Answer-- paleontologist, anatomist, anti-evolutionist

found that the older fossil layers were more uniform over greater spans of time
theory of catastrophism: explained sequential changes in fossils in diff layers through natural catastrophes (floods, earthquakes, etc.)
thought new species appeared in more recent layers by repopulating from elsewhere
recognized extinction, but not evolutionary change
scientific racism: measuring human skulls could tell you their race (disproved by his own student Tiedemann)
believed there was an unknown designer / creator who used one base blueprint to create all organisms, explaining the similarities homology - Correct Answer-shared ancestry and inheritance (descent w modification); many building blocks / underlying features correspond among species vestigial structures - Correct Answer-- Cuvier believed they have an unknown function
evolutionary perspective: relicts since organisms are built on their ancestor's body plans (example: appendix seems useless in humans but koalas can't digest without them) bad design - Correct Answer-- drinking giraffe, inguinal hernias
evidence for evolution since if there was some divine creator, why didn't they do a better job? catastrophism in geology - Correct Answer-Cuvier; volcanoes, floods, and earthquakes are catastrophic events that caused mass extinctions and the formation of all landforms uniformitarianism in geology - Correct Answer-Hutton & Lyell; geological features formed slowly over time by gradual processes accumulating
evidence for evolution since it is the same concept (small changes accumulating over time, cannot be observed but it still occurred) Lord Kelvin - Correct Answer-estimated the age of the earth based on heat loss gradients (100 mill y/o) but didn't know about radioactive decay adding heat (discovered by Marie Curie) so he was off (earth is actually 4.4-4.6 bill y/o) principle of use and disuse - Correct Answer-Lamarck; disuse leads to vestigial organs, use leads to adaptations (such as the giraffe's neck)
inaccurate but initially a believable hypothesis since it could be seen in nature (heterophylly--aquatic buttercups have different leaf forms for their aerial leaves vs. their submerged leaves)

refuge in time: only coming out at times when predators are not present or able to catch, such as nighttime or specific seasons
refuge in size: being large enough to fight off predator or avoid capture Chlorella algae and rotifer predator - Correct Answer-- when predators are abundant, resistant genotypes in prey (make algae toxic to predator) are favored but have lower reproductive rate
predator abundance decreases b/c more prey are resistant
resistant genotype is no longer favored, and prey have a greater reproductive rate
predator abundance increases since the susceptible prey genotypes have increased
both frequency dependent and directional selection lynx and hare - Correct Answer-- could be strictly driven by predator-prey dynamics, or the prey could be limited b/c of food limitations and the predators track and follow these fluctuations
in experiments, reducing both food and predators had a much greater effect on the hare population than either alone
proof that predators and competition act together to stabilize the population positive interaction - Correct Answer-one species is resistant to the stress, so it reduces the stress on the others which are more susceptible to it
can expand the realized niche
strength of facilitation increases with the intensity of the stress
at least one species, neither is harmed fundamental vs. realized niche - Correct Answer-- fundamental niche is the entire set of conditions under which an individual, population, or species can survive and reproduce; does not take external factors such as predation or competition into consideration
realized niche is the set of conditions after interactions with other species have been taken into account; shrunken version of fundamental niche mutualism - Correct Answer-both benefit
obligate mutualism: each species requires the other to survive (yucca moths are the only pollinators of yuccas, and the seeds of yuccas are the only food for yucca moth larvae; lay a limited amount of eggs on each flower since the flower is aborted if there are more than 6 or so eggs)
facultative mutualism: benefits both parties, but not required for either to persist (vascular plants grow better with mycorrhizal fungi, but can survive without them) commensalism / facilitation - Correct Answer-one benefits, one is unaffected parasitism - Correct Answer-one benefits, one is harmed Chthamalus and Balanus - Correct Answer-- chthamalus lived in the higher intertidal zone, which gets submerged for less time at high tide

balanus lived in the lower intertidal zone, so would stay underwater for longer at high tide
balanus can't survive in the higher intertidal zone since they dry out
chthalamus settle in the lower intertidal zone when they are young, then are excluded due to competition and move upwards
partitioning of space resources paramecium and interspecific competition - Correct Answer-- P. caudatum and P. aurelia show competitive exclusion: could not coexist since they use same resources in same way, so P. aurelia won and P. caudatum was driven to extinction
P. caudatum and P. bursaria show resource partitioning: coexist, but live to a lower carrying capacity than they could on their own (have different ways of feeding, but there is still competition which lowers K) keystone species - Correct Answer-have a big effect on the community composition even if they are in low abundance
ex: sea stars prevent competitive exclusion by preying on mussels
often high on food chain foundation species - Correct Answer-have a large effect only when dominant
ex: large trees in forest provide refuge for smaller plants, such as ferns who live in shade) disease - Correct Answer-- caused by pathogens that can be transmitted between hosts either directly or through the environment
organisms resist pathogens either by chemical defenses or through an immune system
immunity can be innate (genetic) or acquired (immune memory)
many pathogens are host specific, infecting only one species or one genotype within a species rabbits and myxoma virus - Correct Answer-- rabbits introduced to Australia and the population increased exponentially
Myxoma virus introduced to control the rabbit population
less mortality over time since strong selection led to the evolution of resistance in the rabbit populations
virus evolves decreasing lethality since when the density of rabbits went down, the virus would not be able to get passed on if the hosts were killed rapidly (transmission rates are lower in low density populations) vaccination - Correct Answer-vaccination prevents the spread of disease since it lowers the number of susceptible individuals
leads to herd immunity if most are vaccinated
if too many refuse to get vaccinated, the number of susceptible individuals can increase and herd immunity can be lost

ulva and gigartina - Correct Answer-experiment showed that compared to the control (both growing together), the situation in which ulva was removed allowed the gigartine to grow over a much wider range

inhibition by the ulva intermediate disturbance hypothesis - Correct Answer-- if there are no disturbances, there would be only competitors and no colonizers
if there were frequent disturbances, there would be few species and likely only early successional
intermediate frequency of disturbances leads to the highest diversity, since disturbance mediates competition ecosystem - Correct Answer-the organisms in a place, interacting with their abiotic environment
ecology: movement of energy and nutrients through organisms and their environment vicariance (allopatric speciation) - Correct Answer-barrier divides the population and two species diverge, then the barrier is removed and sympatry is re-established
ex: isthmus of Panama separated pop. of snapping shrimp, so they diverged into new species all with distinct snapping patterns
the snapping shrimp are sister species on the phylogenetic tree, and each pair of sister species has one in the Pacific and one in the Caribbean peripatric (allopatric speciation) - Correct Answer-one colony diverges from the population and forms a new species (founder effect), then range expansion re- establishes sympatry
ex: Hawaiian fruit flies emerged along with the formation of new islands, each of which represents new habitat for the flies to colonize
different species on different kipukas, or residual forests that have not been interrupted by the lava flow, and most species are confined to a single kipuka parapatric speciation - Correct Answer-no obvious extrinsic barrier, but dramatic environmental discontinuities act as barriers to gene flow since migrants from one population to the other will be selected against, so reproductive isolation occurs
ex: difference in growth of pasture grasses due to the sharp environmental discontinuity on and off mine tailings
lead tolerant / late flowering grasses vs. lead intolerant / early flowering grasses trophic transfer - Correct Answer-movement of energy up a food chain; according to Lindeman, about 10% of energy available at one trophic level is transferred to the next variations in trophic efficiency - Correct Answer-- herbivores have to consume more food in order to get the same amount of energy as carnivores (F - defecation pathway is larger)
carnivores spend more energy catching prey (R - respiration pathway is larger)
endotherms spend most assimilated energy on maintaining body temperature

number of trophic levels - Correct Answer-determined by available energy (primary productivity) and energy efficiency

the energy efficiency has a stronger effect on the amount of energy available to top consumers since even if primary available energy is a large amount, this will not reach higher trophic levels if the efficiency of transfer is low biological species concept - Correct Answer-species that is reproductively isolated, and cannot and will not mate with others allopatric vs. sympatric speciation - Correct Answer-allopatric allows the species to diverge separately in different environments, while in sympatric there is no extrinsic barrier to gene flow so the species either needs little dispersal potential or strong positive assortative mating problems with the biological species concept - Correct Answer-1. how do we know if individuals in separate populations could actually or potentially interbreed?

lab experiments are not always accurate to nature, what is considered natural?
what about asexual organisms?
what about fossils? anagenesis - Correct Answer-WITHIN lineage change caused by natural selection, sexual selection, drift, mutation, etc cladogenesis - Correct Answer-the formation of new lineages through speciation spatial / geographic isolation (allopatry) - Correct Answer-- live in different places between which there is little dispersal

weak dispersal abilities
long distance separation or major physical barriers
ex: rise of the isthmus of Panama shut off gene flow between the Pacific and Caribbean, so larva and adult snapping shrimps could no longer swim between ecological isolation - Correct Answer-- utilize (feed in and mate in) different habitats, even if they were reproductively compatible
ex: benthic sticklebacks occupy the littoral, shallow zone, while limnetic sticklebacks occupy the open water zone of the same lake temporal isolation - Correct Answer-- breed at different times, seasons, years, etc.
ex: periodic cicadas emerge on 13- and 17-year cycles behavioral isolation - Correct Answer-- different courtship rituals
ex: fireflies have different flashing patterns depending on their species

sympatric speciation - Correct Answer-populations have completely overlapping ranges with no obvious geographic barrier, but niche specialization or positive assortative mating can lead to true sympatric speciation (divergence while in sympatry)

ex: crater lake cichlids vary in body shape and mouth shape so could occupy specific microhabitats and a species could exhibit very strong positive assortative mating for individuals with like phenotypes or in the same microhabitat mass extinctions - Correct Answer-generally driven by climate change or extreme events (such as an asteroid impact), and always lead to increased diversity since they opened up empty niches for organisms to fill history of oxygen - Correct Answer-- increased b/c of the evolution of photosynthetic cyanobacteria
marina anoxia occurred at a period, causing a mass extinction
abundance of plants increased the O2 concentration, promoting the growth of many larger, more complex organisms effects of human hunting - Correct Answer-loss of large mammals was observed in Australia, N. America, and Madagascar due to human presence; this did not occur in Africa since humans had a longer history of coexisting and evolving with the organisms on that continent cambrian explosion - Correct Answer-- first
rapid appearance of most modern aquatic animal phyla
caused by presence of oxygen, sexual reproduction, regulatory genes responsible for differences among animal phyla, eyes so animals could evolve to forage different ways, and predation that selected for adaptations in prey mass extinction 1 - Correct Answer-- climate cooling
glaciers
dropping sea levels
75% of species lost devonian era - Correct Answer-- after mass extinction 1
mosses, ferns, trees
symbiotic mycorrhizal fungi were critical since they fixed nitrogen and provided nutritious soil for photosynthetic plants to evolve roots
insects and amphibians mass extinction 2 - Correct Answer-- marine anoxia
climate change carboniferous era - Correct Answer-- after mass extinction 2
swampy plants, giant insects
lots of carbon fixation so many fossil fuels came from this period (as the plant material died, it couldn't decompose in the anoxic waters)

very high atmospheric concentration of oxygen (about 30% vs 20% today) permian era - Correct Answer-- after carboniferous era
reptiles, amphibians, insects diversify
Pangaea supercontinent formed
volcanic activity due to collision of continents mass extinction 3 - Correct Answer-- massive volcanic eruptions
plants died, causing oxygen to drop since decomposing plant material consumed O and not as much was being produced
81-96% of all species go extinct, including giant insects mesozoic era - Correct Answer-- after mass extinction 3
dinosaurs, fish, first flowering plants mass extinction 5 - Correct Answer-- asteroid impact
about 75% of all species go extinct, including all non avian dinosaurs
impact crater is proof (has since been filled by sediment, but imprint is still visible) cenozoic era - Correct Answer-- after asteroid impact
rapid adaptive radiation of insects, birds mammals, flowering plants
many mammal genera able to arise since predator dinosaurs were no longer around
angiosperms: most diverse plant type, over 240,000 species today (flowering, protected seeds since ovary develops into fruit, and hydraulic innovations such as stem vessels and leaf veins foterm-75r more efficient water use)
insect-plant coevolution eld to higher diversity (insects that feed on angiosperms were much greater, such as bees)
after warm, humid beginnings, a cooling trend oligocene-miocene era - Correct Answer-- planet cooling: cooler, drier climate caused rise of grasslands and grazers
grass growth form (basal meristem) allowed quick regrowth after grazing since it grew from the bottom up
C4 plants dominated the grasslands pilocene era - Correct Answer-- after cenozoic era
isthmus of panama forms and changes ocean circulation
himalayas rise
glaciation cycles
as humans spread, large mammals went extinct (except on Africa, since there was coevolution and coexistence of humans and mammals in Africa) anthropocene - Correct Answer-- mass extinction 6?
threats to biodiversity include:

habitat alteration and destruction
harvesting / fishing

vitamin D: essential for calcium metabolism (deficiency can lead to rickets), less UV outside tropics favors light skin since it is necessary to make vitamin D -- north of the 37th parallel, it is difficult to produce enough vitD especially if you are darker skinned
folate / folic acid / vitamin B9: high levels of UV destroy this and reduce serum folate levels, and it is critical for DNA synthesis, protein digestion, red blood cell formation, and normal fetal development -- fair skinned people in the tropics suffer from folate deficiencies
acclimation: tanning in the summer since it can be adaptive to have light skin at some times of the year and darker at others transformational vs. variational - Correct Answer-- transformational: within generations, inherited, and modified by the environment
variational: differential survival or reproduction of individuals with heritable traits, meaning the environment does not cause traits but instead chooses among them blending inheritance - Correct Answer-incorrect theory; hereditary materials mix from parents to form offspring, and this mixture is inseparable Weismann's test - Correct Answer-tested and disproved Lamarckian inheritance and pangenesis -- cut off mice tails each generation to see if they'd start growing shorter, and they didn't particulate inheritance - Correct Answer-Mendel suggested that hereditary particles existed which carry an organism's genetic material; essentially genes gamete - Correct Answer-contains only one particle (haploid, so 1N) zygote - Correct Answer-fusion of two haploid gametes (diploid, so 2N) locus / plural loci - Correct Answer-the position or physical location of a gene on a chromosome; the genotype at a locus is the combo of each pair of alleles for a particular gene allele - Correct Answer-different variants of a gene; different alleles arise through mutations Mendel's First Law: Law of Segregation - Correct Answer-when any individual produces gametes, the two copies of a gene segregate so that each gamete receives only one copy (gametes are haploid, 1N)
odds are 50% that a particular allele will be in any given gamete
diploid gametes (zygotes) contain one maternal and one paternal copy of each allele Mendel's Second Law: Law of Independent Assortment - Correct Answer-1. alleles of different genes assort independently during gamete formation if they are on different chromosomes

genes on the same chromosome are considered to be physically linked and generally do not assort completely independently

multiplication rule: two independent events happening together is the product of P of each
addition rule: event that can occur in two different ways is the sum of the individual Ps linkage - Correct Answer-if a lot more parental phenotypes than recombinants are observed, it is likely that the genes are linked and do not assort independently
when genes are widely separated on the same chromosome, it is possible for crossing over to occur and recombinants to form crossing over and recombination - Correct Answer-- genes may recombine during prophase I of meiosis by crossing over
chromosomes exchange corresponding segments
exchange involves two chromatids in the tetrad, and both become recombinants
crossing over DOES NOT EQUAL recombination
unless both loci are heterozygous, there can be crossing over but there won't be recombination
during metaphase II, the cell divides and gives rise to two cells, each of which carries one pair of each homolog (4 chromatids)
depends on the arrangement of the chromosomes on each side of the metaphase plate polymorphic - Correct Answer-when multiple alleles at a locus segregate in a population; when there are two or more possibilities of a trait on a gene incomplete dominance - Correct Answer-intermediate offspring is formed; red + white flowers = pink codominance - Correct Answer-both alleles are expressed; red + white flowers = red and white spotted pleiotropy - Correct Answer-single allele can have multiple phenotypic effects; the albinism allele in Siamese cats also often produces crossed eyes epistasis - Correct Answer-phenotypic expression of one gene is influenced by another; coat control in Labrador Retrievers, since along with the color alleles there is an allele for pigment deposition and if this recessive is expressed, there is no black or brown pigment deposition and the lab is yellow environmental effects on gene expression - Correct Answer-temperature for point restriction (Max the Siamese -- as he gained weight, the fat insulated melanocytes so he lost his points) biometricians vs. mendelians - Correct Answer-- biometricians believed evolution proceeded by the gradual accumulation of small changes (quantitative variation

Speciation and Evolutionary Processes, Exams of Advanced Education

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