Notes / Essay questions for Test 3 PDF

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Exam 3 Evolution

Essay questions The most important in Yellow

1)

Are intrinsic or extrinsic barriers to gene exchange more likely to initiate speciation? Why?

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The more likely way to initiate speciation is allopatry, or geographical isolation, which is an extrinsic barrier, where gene flow between populations is reduced by geographic or habitat barriers allowing genetic divergence by natural selection or genetic drift. It’s more effective because intrinsic barriers cause a disruption of mating rituals/timings, which would not increase the overall fitness of organisms. Intrinsic barriers to gene flow can also initiate speciation. However, intrinsic barriers have to evolve in populations that are initially able to reproduce with one another. What are four major problems with the Biological Species Concept?

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Difficulty of determining whether two populations are reproductively separated geographically or temporally. The BSC is not practical for taxonomists working with museum specimens. It is difficult to determine if a species has become another species because there are graded levels of reproductive isolation. Sometimes two populations can hybridize to a limited extent but still have partial barriers to gene exchange It is also a problem for determining whether ancestral species are the same species as their descendants.

3)

What is the difference between prezygotic and postzygotic barriers to gene exchange?

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Prezygotic barriers to gene exchange prevent the exchange of gametes. Prezygotic mechanisms include: habitat isolation, temporal isolation, behavioral isolation, mechanical isolation and gametic isolation.

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Postzygotic barriers to gene exchange allow offspring to be made, but reduces the offspring’s fitness. Mechanisms include reduced viability, reduced fertility, cytoplasmic incompatibility, and backcross breakdown. 4)

What is “backcross breakdown”? When is it likely to occur?

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Backcross breakdown is the reduced fitness found in the F2 generation.

5)

Backcross breakdown can occur when species hybridize. So two different species or subspecies produce a hybrid, and it is that hybrid’s children that receive the reduced fitness from incompatible genes, not the F1 generation.

Contrast antagonistic coevolution, commensalism and mutualism – give examples of each

Antagonistic coevolution is particularly likely to take place between parasites and their hosts. It is easy to imagine how a change in a parasite, which improves its ability to penetrate its hosts, will reciprocally set up selection for a change in the host. Ex: Garter snakes evolve resistance to newt tetrodotoxin Commensalism is am ecological relationship between two organisms in which one benefits and the other it little effected Ex: Anemones and Clownfish.

Exam 3 Evolution

Mutualism is a symbiotic reaction in which both organisms involved benefit by their interaction.

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Ex: Ants and Acacia trees.

6)

What is the difference between reinforcement and ecological character displacement?

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Reinforcement is selection to avoid heterospecific mating. Ecological character displacement is selection to avoid competition for resources.

Both reinforcement and ecological character displacement result in differentiation of closely-related taxa.

7)

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8)

How does the theory of punctuated equilibrium mesh with allopatric speciation at the microevolutionary level? Punctuated equilibrium –pattern of rapid evolutionary change in the phenotype. ( branching out by the process of cladogenesis. ) Allopatric Speciation – is speciation that occurs when biological populations of the same species become isolated from each other to the point where they can’t exchange genetic information anymore, forming a different species in the process. comparing the two ideas of punctuated equilibrium and allopatric speciation, we can see that the two is similar. Allopatric speciation occurs when one species get isolated in its population to form two different species, which fit into the idea of cladogenesis where one species split into two or more distinct species.

** What are some of the causes for potential bias in the fossil record? i. ii. iii. iv. v.

Thickness of sediment – The thicker the sediment layer, the more chance for more fossils to be found during the supposed time frame of that layer. The volume of exposed sediment – if one layer is exposed more at the surface than others, then there is more chance for fossils to be found in the time frame that corresponds to that sediment. Metamorphosed rock – metamorphosed rock causes distortions in the rock layer resulting in fossils being distorted or destroyed in the process. Pull of the recent – extant taxa bias diversity measures to recent end of scale. Sampling effort

9)

What are some key technological and cultural innovations leading to modern humans?

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Bipedal locomotion – 4 mya Early stone tools – 1.8 mya Use of fire, hunting and cave dwelling - < 1.8 mya Art – 18,000 + ya Domestication of animals

Exam 3 Evolution

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Agriculture Leading to settling in one area Civilizations being built Trade between places

10) How does over-use of antibiotics promote antibiotic resistance in bacteria? Over-use of antibiotics kill off all of the non-resistant bacteria and leave only the few resistant ones, which can then reproduce to form more resistant bacteria. It is essentially speeding up the selection process and creating more and more resistant bacteria.

More questions : 11) Is the cladistic species concept typological? -

Cladistic species are phylogenetic, not typological. In Phylogenetic speciation is based on heredity/ organisms sharing a common ancestor

12) Under what circumstances is sympatric speciation likely to occur?

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Sympatric speciation occurs when populations of a species that share the same habitat become reproductively isolated from each other. Requires association between mating preference and ecological preference to allow assortative mating to take place. This speciation phenomenon most commonly occurs through polyploidy, in which an offspring or group of offspring will be produced with twice the normal number of chromosomes.

13) What is a living fossil? Give two examples. ·

“Living fossils” are species that have not changed much at all over the course of millions of years. They look nearly identical to their ancestral state. Examples Coelocanth fish (140 million years old) The tadpole shrimp Triops cacncriformis (170 million years old) The horseshoe crab (550 myo). 14) What are some of the possible causes of the end-Permian mass extinction?

Exam 3 Evolution

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Pangaea could have possibly been a cause of end-Permian mass extinction. This huge landmass created extremely hot, dry conditions across most of the interior. By the Late Permian, global temperatures were the highest they’d ever been.

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Many causes have been proposed for the event: asteroid impact, flood basalt eruptions, catastrophic methane release, a drop in oxygen levels, sea level fluctuations or some combination of these. Also, the extinction of species gave rise to the extinction of other species as food chains were being destroyed

15) What is the significance of “mitochondrial Eve”?

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Mitochondrial DNA is matrilineal, meaning that it is passed down from mothers to their children. It remains the same from generation to generation, except when mutations occur that cause branches in the lineage. With all of the mitochondrial DNA studies that have been conducted, researchers have traced all existing mitochondrial DNA back to “mitochondrial Eve,” who theoretically existed in Africa in a small population of the world’s first humans. The “mitochondrial Eve” idea, therefore, supports the Out-of-Africa theory.

16) What is the “nature vs. nurture” debate? ·

The nature vs. nurture debate discusses whether certain attributes are inherited through genes or are a result of the environment of the individual....