Ecology Exam 2 Chapters 13,14,15 Flashcards
How could you experimentally test whether herds of African antelope affect the abundance of plants on which they graze
BLOT: FENCE OFF THE AREAS OF PLANTS ONE WITH ANTELOPE AND THE OTHER WITHOUT. CHECK TO SEE HOW ANTELOPES AFFECT IT. THE PLANTS LEFT OVER R THE ONES THE ANTELOPES PREFER NOT TO EAT
Fence off areas of plants with antelope and areas without antelope. This way we can compare how antelopes influence how many plants and the types of plant species available. The remaining plant species left in the area with the antelopes are the ones the antelopes prefer not to eat.
Explain why an herbivore that consumes many different species of plants might be less successful at regulating the abundance of a well-defended plant species compared to an herbivore that specializes on eating a single species of plant.
Herbivores that consume a lot of plant species are less successful at regulating the abundance of well-defended plants because they are more likely to just eat what is most convenient to them. There is a less of a trade off cost when they do so because they dont waste extra energy trying to get the well-defended food when they can get something else. Herbivores who specialize in eating just a single species are much less flexible, so they will eat that plant no matter how well defended. In this case the herbivore that only eats one kind plant will be more effective than herbivores who eat anything when it comes to regulating well-defended plant species.
How do the results of the classic experiments of C. F. Huffaker using mites and oranges in the lab inform us about how predator and prey populations are able to persist in nature?
Blot: Experiment he had 2 species of mites, one prey and another predator. He had oranges and rubber balls for the experiment. Because the predators had to walk from one orange to another and avoid Vaseline barriers, the prey stayed one step ahead of the predators. This experiment demonstrated that they can both persist in nature as long as there is suitable refuges for the prey.
Huffaker’s experiment demonstrates that predators and prey cannot coexist in the absence of suitable refuges for the prey. However, they can coexist in a spatial mosaic of suitable habitats that provide a dispersal advantage to the prey. Two time delays caused the populations to cycle: The predators dispersed more slowly between food patches than did their prey, and the predators needed time to increase their population size through reproduction. From this, we can conclude that stable population cycles can be achieved when the environment is complex enough that predators cannot easily find scarce prey.
In evolutionary terms, explain why introduced species can often have harmful effects on native species but can also be controlled by an enemy that comes from the introduced species’ native region
Blot: When a species is introduced into a new environment the native species is often destroyed. This is because the native species has never lived with the introduced species and thus they will be decimated. For example, when snakes were introduced on Guam the birds, bats, and lizard have never lived with them before and thus hadn’t evolved any defenses against predation so their populations were decimated. However if we introduced an enemy from the introduced species native region we can control the introduced species population. This is because he has lived with the introduced species and evolved ways to hunt and eat them unlike the native species. Example is prickly pear cactus, most herbivores do not eat them but the cactus moths were introduced to limit their population.
The introduced species can disrupt the ecological balance in the ecosystem by becoming a new prey for native predators and a new predator for native prey. For example, a new introduced lizard species appears in a community with wolves and spiders. Wolves are lizards’ predators. Spiders are lizards’ prey. Increase in lizards population causes sudden decline in spider population with an additional predator that spiders have to adapt to. Increase in lizard population, however, provides more food resources for wolves, so wolves population increases. Eventually, the lizard population will decline due to the wolf population, which will cause the spider population to increase, and then the lizard population will increase again. Both populations cycle up and down in abundance, with predator abundance lagging behind prey abundance, while making sure that spiders and wolves don’t go extinct and lizards don’t exceed carrying capacity.
Compare and contrast a predator’s numerical response and functional response.
Blot: it has to do with predator prey relationships.
FUNCTIONAL: HOW MUCH PREY EATEN PER PREDATOR
NUMERIC: CHANGE IN NUMBER OF PREDATORS THRU POP GROWTH OR POP MOVEMENT
The relationship between the density of the prey population and an individual predator’s rate of food consumption is known as the functional response of the predator. While a predator’s functional response tells us how many prey can be consumed by a given predator, the numerical response is a change in the number of predators through population growth or population movement due to immigration or emigration.
Functional Response: Per capita rate of consumption by predator in relation to number of prey.
Numerical Response (number of predators): Increase in consumption leads to an increase in predator reproduction or aggregative numerical response.
How might a type II functional response prevent a predator from controlling a large prey population?
As there is more prey consumed, there is less prey per predator consumed.
The type II functional response occurs when the number of prey consumed slows as prey population density increases and then plateaus. The number of prey consumed slows because as predators consume more prey, they must spend more time handling the prey. A type II response results in a decreasing proportion of prey being consumed, and predators are limited to maximum consumption rate, so there is a smaller prey population that the predators control.
What are the causes of an evolutionary arms race between consumers and the species that they consume?
blot: Pretty much prey find a way to repel predators, but predators adapt leading to this coevolution.
Coevolution is when two or more species affect each other’s evolution. This evolutionary arms race is a result of coevolution because both species are trying to survive. An example would be porcupines. They evolved to have these spikes to scare away predators, but bobcats found a way around this. They flip the porcupine over and attack the belly which has no spikes. Other common predator adaptations include high-speed locomotion to catch their prey and camouflage that allows them to ambush their prey. Some predators can also evolve to handle the toxic chemicals produced by prey.
Compare and contrast the advantages and disadvantages of life as an ectoparasite versus an endoparasite.
BLOT: ENDO – INSIDE OF ORGANISM. ADVANTAGE: HAS ACCESS TO host’s body fluids on which they feed. DISADVANTAGE: HAS DIFFICULTY MOVING FROM HOST TO HOST. ECTO- OUTSIDE, DOES NOT HAVE TROUBLE GOING HOST TO HOST, LOW EXPOSURE TO HOST IMMUNE SYSTEM \
Ectoparasites live on the outside of organisms, whereas endoparasites live inside organisms. Ectoparasites have high exposure to natural enemies and external environment, don’t have difficulty to move to and from host for parasite or its offspring, low exposure to host’s immune system, and easily feed on host. Endoparasites have low exposure to natural enemies and external environment, struggle to move to and from host for parasite or its offspring, high exposure to host’s immune system, and high ease of feeding on host. Living inside the host also gives endoparasites easy access to the host’s body fluids on which they feed.
Why might parasites that are not very harmful to hosts in their native range be useful in controlling non-native hosts in an introduced range?
Blot-the host population in the new region lacks defensive adaptation against foreign parasite.
In native range, hosts evolve defense to fight parasites. The non-nativehost population in the new region would lack defensive adaptation against foreign parasites, so introducing these parasites would keep the population of the hosts in check. While the host will eventually be able to evolve some level of resistance and undergo chemical, morphological, structural or behavioral modifications and adaptations, it takes time, so it would be multiple generations before parasites can’t stabilize non-native host populations anymore.
Given that there is currently no cure for mad cow disease, what is likely to be the most effective action to reduce its transmission?
The most effective action would be to exclude cows from areas rich with ground remains of other cows, so the cows don’t consume the mutated prions from dead cattle and become infected and pass infection to humans ultimately passing on the infection to humans.
Why might we continue to discover new emerging infectious diseases?
New diseases typically emerge when a mutation allows a pathogen to jump to a new host species. For example, Severe Acute Respiratory Syndrome (SARS) is a viral infection that first appeared in China in 2002 and spread to 32 countries; it caused more than 700 people to die. The world has experienced one new emerging infectious disease every year since the 1970s. Shifts in migration and travel patterns, global eating habits and the effects of climate change have created new opportunities for microbes to spread, also new technology makes it quicker to detect.
Compare and contrast horizontal versus vertical transmission of a parasite.
blot: Horizontal parasite moves from parent to someone besides their offspring. Vertical is parent to offspring. For vertical, the parasite must evolve in such a way that it does not cause the death of its host until after the host has reproduced and passed the parasite to its offspring. example horizontal is bird flu, one bird to other
Horizontal transmission occurs when a parasite moves between individuals other than parents to their offspring. For example, horizontal transmission occurs when helminths (parasitic worms) are transmitted from snails to frogs or from frogs to birds. Horizontal transmission can also occur between conspecifics (animals of the same species), such as the transmission of bird flu from one bird to another. Vertical transmission occurs when a parasite is transmitted from a parent to its offspring. In this case, the parasite must evolve in such a way that it does not cause the death of its host until after the host has reproduced and passed the parasite to its offspring.
Using the basic S-I-R model of parasite and host dynamics, explain why the proportion of infected individuals in the population declines over time.
Blot: population of infected individuals declines overtime because more get infected and they build resistance. Also by vaccinating individuals, we reduce the size of the susceptible population.
Susceptible-Infected-Resistant (S-I-R) is the simplest model of infectious disease transmission that incorporates immunity. because the number of infected individuals increases. In such a model, the result is an epidemic that runs its course until all individuals in the population have become resistant or there are too few susceptible individuals remaining to sustain the spread of the disease.
In the S-I-R model of parasite and host dynamics, how will the outcome change if we allow new susceptible individuals to be born into the population?
blot: leads to cyclic fluctuations between number of susceptible and infected; number of resistant continues to increase
the birth of new susceptible individuals can cause cyclic fluctuations. the number of susceptible individuals and infected individuals maintains its level. The number of resistant individuals continues to increase.
When using a t-test, what factors make it more likely that you will find a significant difference?
blot: IF T VALUE IS HIGHER THAN CRITICAL REJECT THE NULL.
The critical value using alpha = 0.05 and t-value indicate if there is a significant difference. If the critical value for P value is less than 0.05, we reject the null hypothesis and can conclude that there is a significant difference between the mean of the groups.
