Exam 3 Study Questions Bio 121 PDF

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Lecture #19: Patterns of Population Growth 1. You were given two equations in lecture which both describe exponential growth in biological populations. Why is there a need for 2 different equations? Under what conditions would you use each equation? When are these equations equal? Discrete: equation: N=NoRo^t, Ro= net reproductive rate (number of females produced/number of females currently) N= future popualiton size No= initial pop size T= number of time periods Use this equation when an organism only breads once during a specific breeding season, non-overlapping generations Continuous : overlapping generations, humans Equation: Delta N/Delta T=rN Rate is the change in number of individuals in unit time (delta N/Delta t) r= intrinsic rate of increase, equal to the average birth rate minus the average death rate N=Noe^rt, used to figure out future population growth over time Equations are equal when

2. Can a population maintain exponential growth forever? What about the human population? Explain. ~resource limitations over time ~ birth rates are going to drop and death rates are going to rise and there is restricted growth, grow for awhile and then slow down to maximum pop size called carry capacity (K) of the environment

3. Compare and contrast Ro and r. What do they describe? What is the value of each of these when the population is increasing? Decreasing? Stable? Both are similar when it comes to how population size changes although they represent different factors of population growth such as Ro= the number of females produced while r is the number of births and deaths. When the population is increasing= Ro= less than 1, r= less than zero When the population is decreasing= Ro= 1 and r= 0 When population is increasing= Ro= greater than one and r = greater than zero

4. When biologists grow cultures of cells to study, the cells reproduce rapidly at first. However, as the population of cells gets larger, the cells begin to divide more slowly. What type of growth curve does this represent? What factors do you think cause population growth to slow down? Would this be an example of density-dependent or density-independent population regulation? Logistic growth, the population reached carrying capacity (K) causing the growth to level off, this is an example of density dependent regulation.

5. How does logistic growth differ from exponential growth? Under what conditions would each type of growth occur? At what size is a population's rate of increase greatest? Least? ~logistic growth depends on carrying capacity and will level off at K while exponential does not have this S shaped curve. If the population size is near zero than you would get exponential growth and if N=K or N>K then you get logistic growth. Population rate is highest when k/2=N and is the least when the population has low or high density 6. In the future, 500 humans colonize a beautiful but tiny planet in another star system. This planet can support a total of 10,000 people. Assuming the intrinsic rate of increase per year is 0.3, what is the yearly rate of population increase? At what population size would the growth rate be highest? ~so you would use continuous growth so your yearly rate is .3(500)= 150 per year And your population growth would be the highest at 10,000/2 so 5,000

7. Hurricane season was really bad this year. Are hurricanes an example of density-dependent or density-independent population regulation? What are other examples of density-dependent regulation? Density-independent? -Density independent, another example is fire or climate or flood -density dependent is competition disease, crowding stress

8. You are brewing a batch of lager beer. You introduce hops, grains, wort and 10,000 yeast. Assuming your intrinsic rate of increase is 0.4 per hour, what is the hourly rate of growth in the yeast population? ~.4(10,000)= 4,000 per hour

Lecture #20: Demography and Life History Strategies

1. Describe how survivorship and fecundity interact to produce a population's growth parameter. How does a life table present this interaction? ~fecundity and suviroship interact because to get the Ro (net reproductive factor) you have to find the sum of the fecundity (Mx) times survivorship (lx), which = is why a life table is made

2. What can an age distribution tell you about survivorship and fecundity? How is this done? - Age distribution can tell you about can tell you about can tell you about the mortality or surivorhsip of the population whether it is at old, constant, or young. Graphs show whether growing, stable, or declining and you can figure out the growth rate due to the abundance of reproductive and non-reproductive individuals and it matters on whether they are surviving or not.

3. Some organisms (e.g. humans, maple trees, many birds) will have multiple reproductive events throughout their life. However, they will only produce a few offspring during each reproductive event. Other organisms (e.g. century plants, insects, salmon) can produce a huge number of offspring during one reproductive event, but then they die. What is this an example of? Explain why it is not possible for an organism to be the best at everything – why it can’t live the longest AND have the most reproductive events AND produce the most offspring during each reproductive event. ~ these are examples of r- selected and k-selected groups. An organism can’t be the best at everything because there are life-history trade offs

4. Define r- and K-selection strategies. Under which environmental conditions are each of these strategies favored? What types of organisms possess each of the strategies? r- selected strategy is productivity and k-selected is efficiency r-selected is for unpredictable or variable environments while k-selected is for more stable environments mussles are r-selected and humans are k-selected

5. Last summer your family built a new shed in your backyard, which was promptly colonized by deer mice. In this population, 30% of the females survive to breed each year. Females produce an average of 12 offspring a year (half female, half male), except when lx = 1. This breeding schedule continues until females reach their 4th year, at which point they die. Compute the net reproductive rate for this population (Ro). Is the population growing, decreasing or stable? ~2.502 so this population is increasing because Ro is greater than 1

Lecture #21: Human Population Growth

1. How is doubling time for a population calculated? What countries have the highest and lowest growth rates? What social and economic characteristics favor each of these patterns? ~ doubling rate is calculated by ln2/r and developing countries have highest growth rates and developed countries have lowest. The more economically stable and developed the lower the growth rate 2. Describe the age structure and demographic transition of developing and developed nations. How are these characteristics related to r and K? Demographic transition changes as sanitation, nutrition and medicine increase. These correlate to r and k because as the increase in growth rate happens that need for more children decreases as the death rates decrease to new better developments.

3. As Czar of the World, you decree that every couple can only have 2 kids. (Since we’re pretending that you are czar of the world, we’ll also pretend that everyone gets married and nobody gets divorced.) Will the global population stop increasing immediately? Explain. Not entirely because the kids at that time will eventually reach reproductive age and have kids and will increase the growth rate even though there is a limit.

4. In developing nations, we see that death rates decline over time. Eventually birth rates begin to decline, as well, but not as quickly as death rates. Explain why death rates decrease before birth rates decrease. ~ Death rates decline before birth rates because of the increase in better technology such as medicine also there is historical views about having children, free labor of kids, no birth control, desire to increase group, and children might equal prestige in the area

5. Ten years from now, the president of a developing nation discovers that you took BIOL 121 with Dr. Minchella and he knows that you learned about human population growth. He wants to get your advice on how to facilitate sustainable development in his country – in return he will make you very wealthy. If you could give him one piece of advice concerning women on how to achieve this, what would it be? (Aren’t you glad you took 121!!!) ~ Have to increase education for women

6. Vampire ants siphon nutrients from the hemolymph of their own larvae. Imagine a population of vampire ants that doubles in 20 years. What was the intrinsic rate of increase per year? ~ln2/20=r

Lecture #22: Interactions among Populations

26. Which of the three types of interactions between populations can be grouped together under the vague term "symbiosis"? Give an example of each type of interaction. ~mutualism, parasitism, commensalism Mutualism- acacia and ants Parasitism- hookworm Commensailism-barnacles and a rock

27. What is the difference between a fundamental niche and a realized niche? (Hint: "One is smaller than the other" is NOT a complete answer.) Are they always different? Give an example of an organism with both a fundamental and realized niche. ~ fundamental niche is what could be used or all possible resources in an environment but a realized ncihe is the actual amount used by the species. They are not always different such as with the mussles when competition is taken away some species can consume all the resources or all the rock in this case.

28. How might intraspecific competition lead to adaptation? ~concept of natural selection on in between a species to reproduce and survive

29. Interspecific competition does not always lead to local extinction of one of the competitors. What two phenomena might lead to stable coexistence?\ Resource portioning and character displacement

Lecture #23: Coevolution

1. There were nine different avoidance mechanisms described for prey species. Given all these different defenses, how does predation occur at all? ~predation occurs still because predators can change morphologically and behaviorally to increase their chances of getting prey and compete with the arms race between predators and prey.

2. Why do we expect cyclic oscillations in predator/prey systems? Why are these cycles hard to demonstrate in laboratory experiments? ~Because they have impacts on eachother so as the prey pop drops the the predator pop will eventually drop and as the predator pop increases the prey pop will drop so they are off from eachother, and you can’t demonstrate this in a lab easily because you need a variable environment

3. Thought question: If predators seem to use optimal foraging strategies for the current prey type, how can they hope to cope with future defense adaptations of the prey? ~they have to be able to keep up with the evolutionary arms race and adapt to the other adaptations of the prey.

4. How do keystone predators contribute to community species diversity? Give an example of a keystone predator. ~starfish are a keystone predator and they focus on the main competitor of the prey and allow coevolution and diversity. 5. What level of virulence is favored for insect-transmitted viruses infecting Australian rabbits? Why? Is this an example of directional, disruptive, or stabilizing selection? ~intermediate virulence because it allowed the rabbit to live long enough for the mosquito to get the blood and also gave the mosquitos open sores to get the blood from the rabbit to spread this is an example of stabilizing selection.

6. Gause was responsible for two sets of experiments (discussed in Lectures 22 and 23). What did these sets of experiments demonstrate?

~ one was the predator experiment with the paramecium and f=if he could get acyclic pattern between them but realized it was too homogeneous. He also did another experiment about competition with paramecium too.

7. Today's "Were you listening?" Question: How does the grasshopper mouse counter the stink beetle's defense? ~stick the beetle’s ass in the ground and eat it head first

Lecture #24: Parasitism, Immunity and Disease

1. Parasites and predators both affect other organisms in a negative way to gain some benefit for themselves. How do the short-term effects of parasitism and predation differ? ~ with predation the predator kill the animal and feeds although a parasite lives with the host and is symbiosis with it unlike predation.

2. What can a parasitologist learn from a model of host-parasite dynamics? Which components of the model influence the rate at which infections appear in the population? Or the rates at which infections disappear from the population? ~They can learn the transmissive threshold and how to decrese the infected hosts and susceptible hosts. The parts of the model that affect how fast the population appears by loss of immunity and by birth, while the rate of disappearance is affected by death and getting infected

3. Which of the transmission adaptations (there are more than one) would you expect to find in a species of parasites that infects hosts with very low population densities (e.g., contact between hosts is rare)? Name parasite species that use these transmission adaptations. ~ they could wait and have a resting stage for when the environment changes enough to cause infection levels to raise or they could use behavioral modification to increase the transmission from host to host. Ascaris uses resting stage and Dicrocuelium uses behavioral modification.

4. Thought question: All of the establishment adaptations involve hiding from the immune system. Which ones involve hiding temporally, and which ones involve hiding spatially? Name parasite species that use these transmission adaptations. The ones that hide temporarily are the hit and run parasites such as ascaris which stimulates the immune system and then moves to the gut. Taxoplasma also live in the immune system inside a macrophage that doesn’t destroy them.

5. The "were you listening" question: If you handle dollar bills without washing your hands, what are your chances of picking up an ascaris egg? ~very high

Lecture #25: Birds and the Bees and the Virus

1. Why is HIV called a "retrovirus"? Describe the life cycle of HIV. ~HIV is called a retrovirus because it attaches to the host cell and transmits RNA and reverse transcriptase into host cell to turn RNA to cDNA

2. How does HIV recognize a host cell? ~It recognizes the host cell, T-helper cells, because the virus has a matching protein to the receptor of the t-cells allowing it to match perfectly and open the cell like a doorknob

3. What are some examples of opportunistic infections which become established after infection with HIV? ~LTBI and Pneumonia

4. Why can't a single vaccine effectively cure someone of HIV? (Hint: Remember that reverse transcriptase has a high error rate.) ~A single vaccine wouldn’t work because there are so many mutations in the virsus that it would become too difficult for the vaccine to match the mutated virsus

5. Nucleoside analogs and protease inhibitors are two classes of drugs used to treat AIDS. How does each work? The nucleoside analogs try and block the RNA and DNA synthesis by resembling the nucleotides of the DNA and protease inhibitors act on inhibiting HIV Protease which prevents the proteins from being cut up into the correct sizes.

6. "Were you listening...?" How many people die of AIDS each hour in the US? 1...