BIS 2B Final Study Questions exam questions and answers correct and verified 100%

BIS 2B Final Study Questions exam questions and answers correct and verified 100%BIS 2B Final Study Questions exam questions and answers correct and verified 100%BIS 2B Final Study Questions exam questions and answers correct and verified 100% What is the biological species concept, and what are its main criteria for defining a species? - correct answers-a group of actually or potentially interbreeding natural populations which are reproductively isolated from other such groups. Contains breeding units (Populations, gene pools, etc.) "species are breeding units that are evolutionarily independent from other breeding units." Explain why application of the biological species concept is difficult or impossible in each of the following situations: (a) examples of natural hybridization, (b) the existence of strictly asexual organisms, and (c) disjunct (allopatric) distributions of species. - correct answers-(a): the mating of two genetically different populations make it hard to tell if the offspring produced will be relatively fit and fertile. (horse + zebra , wolves + coyotes) (b): because asexual organisms do not reproduce with other individuals it is impossible to apply the biological species concept. (c): allopatric species rarely breed with one another due to the isolation of breeding units. Two closely related grasshopper species occur sympatrically. No hybrids have been reported in nature. However, when an evolutionary biologist brings the two species into the lab, she discovers that they can hybridize to produce fertile offspring. How can you explain these observations? Should the grasshoppers be considered separate species? - correct answers-the species are isolated from geologically or behaviorally each other so that is why it is not common to see the hybrid species in nature. They should be considered a different species because they do not reproduce with each other in nature. How does natural selection versus genetic drift act to promote the evolution of intrinsic barriers to gene exchange in allopatric (both vicariance and peripatric/dispersal modes) versus parapatric versus sympatric models of speciation? (What is an intrinsic barrier to genetic exchange, and how does it differ from an extrinsic barrier?) - correct answers-Intrinsic barriers are circumstances such as behavioral isolation or the infertility of two species offspring. Extrinsic barriers are physical barriers that separate two species from each other and prevents genetic exchange. Why have island archipelagoes played such an important role in the development of the science of speciation? What lessons have we learned from studies of speciation in places like the Hawaiian or Galápagos Islands? - correct answers-They have played an important role in the development of speciation because they are isolated from other climates allowing them to allopatrically diverge from one another despite being on the same island. Founder effects and diversifying selection are important for the evolution of new species within an island. Why do most evolutionary biologists agree that allopatric speciation is common but sympatric speciation is not? Focus your discussion on the fundamental difference between these two alternatives, and why that difference is likely to be important for divergence and the evolution of reproductive isolation. - correct answers-Allopatric: the splitting of species into two or more repoductivly isolated groups due to a geological barrier or change making it impossible to interact. Sympatric: the splitting of an ancestral species into two or more reproductively isolated groups without geographical isolation of those groups. Most biologist will agree with this because sympatric speciation is very rare in nature as it requires the species to behaviorally isolate themselves from one another to the point where they are genetically different. Sympatric speciation is generally thought to be a rare event because sympatry should promote gene flow. Explain clearly the evidence that speciation occurred sympatrically in the crater lake cichlid fish inhabiting Barombi Mbo in Cameroon. In particular, explain how the phylogenetic relationships of the 11 species of cichlids in this lake support the argument for sympatric speciation. How does this contrast with the phylogenetic evidence for vicariant allopatric speciation in snapping shrimp? - correct answers-Based on lecture it was said that sympatric speciation within the lake following a singe initial colonization of the lake shows how green species migrates into the lake and then the green species gives rise to the blue species and so on. Genetic variants w/i a population use specific microhabitats or consume diff prey that select for diff traits. 4 speciation of cichlids must have been sympatric because daughter species equally speciated, meaning that the majority of divergent lake species came from a single river ancestor. Define monophyletic, paraphyletic, and polyphyletic clades/taxa - correct answers-Monophyletic: a taxonomic group (relative level of a group of organisms in a taxonomic hierarchy) that includes all of the taxa species descended from a specific common ancestor. Paraphyletic: A taxonomic group that excludes some of the descendants from a specific common ancestor Polyphyletic: A taxonomic group that does not contain the most recent common ancestor of its members Taxonomic groups - correct answers-refer to picture... Pre-zygotic - correct answers-Prezygotic isolation prevents the fertilization of eggs Post-zygotic - correct answers-Postzygotic isolation prevents the formation of fertile offspring Why do most evolutionary biologists agree that allopatric speciation is common, but sympatric speciation is rarer? a) Because reproductive isolation CANNOT evolve in sympatry. b) Because sympatric species cannot occupy separate niches. c) Because there is no extrinsic barrier to gene flow in sympatry. d) Because inbreeding is too common in sympatry and populations go extinct. e) Because disruptive selection can only act on allopatric populations. - correct answers-c) Because there is no extrinsic barrier to gene flow in sympatry. The main problem with understanding how genes responsible for reproductive isolation could increase in frequency is... a) such genes would reduce the fitness of an individual that carries them. b) such genes would rapidly spread due to sexual selection. c) genetic drift would immediately eliminate them from a population. d) hybrids carrying these genes would be competitively superior to parental genotypes. e) none of the above. - correct answers----- You carefully study adjacent populations of two very similar meadow mice, one from Woodland (about 15 km north of Davis), the other from Davis. You want to know whether the Woodland and Davis populations belong to the same biological species or to two different species. You could most confidently decide this if you could... a) show that where the ranges of the two mice overlap there is no hybridization. b) bring the two types of mice into the laboratory to see if they will mate. c) demonstrate that the natural ranges of the two types of mice are entirely allopatric. d) show that there are statistically significant coat color differences between the two types. e) show that the Woodland mice prefer to eat meat, but the Davis mice prefer to eat tofu. - correct answers-a) show that where the ranges of the two mice overlap there is no hybridization. Two species of wild lettuce grow sympatrically, but one flowers in the early spring, and the other flowers in the summer. This is an example of... a) post-zygotic reproductive isolation b) gametic incompatibility c) behavioral isolation d) temporal isolation e) reinforcement f) hybrid incompatibility - correct answers-d) temporal isolation What is the evidence that natural selection favors the evolution of leg length in cane toads as they expand their range in Australia? If you wanted your toads to win a race, where would you collect them? - correct answers-"Offspring reared in a common environment exhibited similar geographical divergences in morphology as did wild-caught animals, suggesting a genetic basis to the changes. Limb dimensions showed significant heritability (2-17%), consistent with the possibility of an evolved response. Cane toad populations thus have undergone a major shift in sexual dimorphism in relative limb lengths during their brief (81 years) spread through tropical Australia." What is the competitive exclusion principle? What general condition must be met for two potential competitors to avoid competitive exclusion (i.e. to coexist)? - correct answers-The competitive exclusion principle says that two species can't coexist if they occupy exactly the same niche (competing for identical resources). Two species whose niches overlap may evolve by natural selection to have more distinct niches, resulting in resource partitioning. What is ecological character displacement and explain how it can result in low niche overlap between similar competing species? - correct answers-Character displacement occurs when similar species that live in the same geographical region and occupy similar niches differentiate in order to minimize niche overlap and avoid competitive exclusion. Describe how tradeoffs can allow species to coexist even if they use the same resources and one is a vastly superior competitor to the other. Offer a plausible example (there are many possible examples if you look back at your notes from lectures on tradeoffs). - correct answers-Ex: Resource partitioning- species of bumblebees specialized in flying in different altitudes. They also have shorter and longer proboscis (thing used to get nectar from flowers) and can use the same resources in the same niche. Trade-offs are the energy it takes to fly at different heights. Ex: Barnacles and Chthalamus; Although Balanus are better competitors than Chthalamus. they can coexist because of their tradeoffs. Chthalamus is a poor competitor but can withstand stress better (being dried out during low tides) and Balanus is an efficient competitor, therefore, allowing it to live over a broad range but is more sensitive to desiccation (extreme dryness). Explain the difference between exploitative and interference competition and give an example of each. - correct answers-Exploitive competition is when individuals use the same resources but don't come in contact with each other. This is most common between species such as deer and squirrels competing for acorns. Interference competition is when direct contact between individuals competing for the same resource. This is most common with in a species such as red winged blackbird competing for nesting grounds. In the lynx-hare example we discussed in class, explain how changes in predator abundance over time is both a cause and a consequence of the abundance of prey. You need not be able to reproduce the equations, but you should be able to take a graph of predator and prey abundance and explain carefully what causes each population to go up or down in size over time. - correct answers-as the number of prey increase, the predator abundance increases as food supplies increase, as the number of prey decrease, as does the number of predators as food becomes more scarce; it is possible for predators to drive their prey to extinction How does intraspecific competition contribute to stabilization of predator-prey cycles? Or, put another way, how could intraspecific competition actually PREVENT a prey species from going extinct? - correct answers-Infraspecific competition actually helps a population because the competition between individuals keeps the population in check. Without this competition, the resources could be completely consumed causing the population to overshoot their carrying capacity. Then once their resources are gone, the population is at risk of extinction. What is a functional response? Explain what biological processes or phenomena would cause each type of functional response, and what three main shapes can they take? What are the three types of functional responses? Compare how changing from a type I to a type III functional response affects the oscillations of predator and prey populations? - correct answers-the functional response is how the number of prey consumed per predator changes with prey density; we have a linear functional response: number of prey consumed per predator is an increasing function of prey density; functional response can also appear sigmoidal or logistic in its graphical curve logistic: number of prey eaten per predator increases to a capacity where which the predator is satiated; the predators hit the limit at which they can reproduce and the number of prey eaten per predator evens out (type 2 curve) sigmoidal: type 3 curve; predators under-consume prey at very low densities due to refuges or prey switching (limited prey), when prey is more abundant, the number or prey eaten per predator increases rapidly then levels out at a capacity where the predator is satiated Explain why positive interactions play a prominent role under "stressful" conditions. - correct answers-Under stressful conditions, positive interactions can help mitigate the effects of those negative interactions. These interactions are not preformed in an attempt to help the other species but because without them, their survival is threatened. These interactions can also help shape the size of the fundamental niche. Furthermore, studies show that these types of positive interactions increase as the stress level increases Distinguish between the fundamental and realized niche. - correct answers-Fundamental niche is the entire set of conditions under which an animal (population, species) can survive and reproduce itself. Realized niche is the set of conditions actually used by given animal (pop, species), after interactions with other species (predation and especially competition) have been taken into account. Compare and contrast the processes that drive cycles of measles outbreaks (or other infectious diseases) with cycles of predator-prey as in the lynx-hare example from lecture. - correct answers-When the disease persists in the prey population and the predators have a sufficient feeding efficiency to survive, the disease also persists in the predator population. The spread begins to spread faster in both creating a positive feedback loop. How does vaccination reduce disease frequency and how can small decreases in the number of people being vaccinated lead to large changes in the extent of outbreaks of the disease? - correct answers-Vaccines help the organism who is vaccinated develop an immune response to the disease before it has it. Mutations can occur more easily if people do not get vaccinated. Explain the concept of herd immunity and explain why different fractions of the population must be immune in order to achieve herd immunity for different diseases. - correct answers-Herd immunity - the resistance to the spread of a contagious disease within a population as many individuals are immune. Different fractions of the populations must be immune because it will even out immunity and disease won't shred through particular communities when resources are available. Offer 2 possible ways to reduce disease spread that both involve decreasing the number of susceptible organisms in the population. - correct answers-Vaccination and herd immunity Why might natural selection favor variants of a disease that are LESS virulent? Describe one example of this phenomenon. - correct answers-Natural selection could favor a disease less virulent because it will be easier to transmit. It is a trade off. Covid-19. Name and describe the three "models" or "mechanisms" of succession. B. Be able to relate an example of succession in a real community and explain how successional change in that community is determined by one or more of these mechanisms. - correct answers-Facilitation: when pioneer species is needed for colonization of habitat by modifying environment (Ex: Alder trees fix nitrogen in soil, improving conditions for the growth of spruces). Inhibition: when pioneer species inhibits subsequent colonization of habitat by making environment less suitable (Protection) Tolerance: Early-successional species neither increase nor reduce rates of recruitment and growth of later-successional species. Species sequence is solely a function of life history. Late-successional species arrive, then grow slowly Late-successional spp. are able to grow and reproduce despite the presence of early- successional spp. Succession: Predictable changes in community composition through time. What are the characteristics of typical early successional species and late successional species? Describe the tradeoffs that make it difficult for species to thrive in both early and late successional communities. - correct answers-Early successional species: dominant species in early stages of succession - characteristics: high growth rates, small in size, high degree of dispersal, high rates of population growth - often require or tolerate high light and tolerant of dry conditions Late successional species: dominant species in late stages - characteristics: low growth rate, larger in size, lower degree of dispersal, lower rates of population growth - often shade tolerant and prefer moist conditions - sugar maple is an example Describe the intermediate disturbance hypothesis (IDH) and use this hypothesis to predict how diversity will change throughout the course of succession. - correct answers-1. Facilitation: Ulva could modify the environment to make it more suitable for Gigartina 2. Inhibition: Ulva may be excluding Gigartina but is removed by biotic or abiotic stresses 3. Tolerance: Gigartina is slower growing, and it just takes it longer to dominate the community. Explain how each of the following factors affect local species diversity. Provide an example to illustrate your answer. A. Foundation species B. Productivity (resource availability) C. Habitat complexity D. Competition E. Keystone predators F. Disturbance - correct answers-A. Foundation Species will always make the community less diverse B. Resource availability will lead to organisms either dying or adapting to fit the fundamental niche of the environment C. Habitat complexity will lead to much more diversity (ex. rainforests) D. Competition will push organisms to occupy different niches promoting diversity (beak size) E. A classic keystone species is a predator that prevents a particular herbivorous species from eliminating dominant plant species F. Disturbance commonly destroys