BIO 340 Ch. 21 & 22 (Critical Thinking)

The relationship between bees & plants is mutually beneficial to both species. Why? What does each species gain from the relationship?

Bees gain food in the form of protein-rich pollen & sugary nectar, while the plants gain an efficient mechanism for distributing their pollen for reproduction.

You are tasked with estimating the population size of 3 species of animals occurring in a national park. One occurs in a random distribution pattern, the second in a clumped pattern, and the third in a uniform pattern. Below, list the 3, and for each one describe any problems you might encounter and how you would estimate population size given those problems and that pattern. Finally, comment on how accurate that estimate might be.

1. Random - Individuals may be difficult to find, so the entire park might have to be searched. Alternatively, a large area could be searched and the number then extrapolated to the area of the entire park. This would be the least accurate estimate. 2. Clumped - Individuals may be initially difficult to find, but once found, a very accurate estimate could be obtained. 3. Uniform - Individuals may he initially difficult to find, but once found, the number of animals in a small area could be counted and then that number extrapolated to the entire area over which they occur. This would lead to a fairly accurate estimate.

List 3 types of data sources scientists might use to monitor the health of a population & what each of those sources can tell you.

1. Scat can tell you about diet & yield DNA. 2. Bones can tell you about the presence of arthritis and osteoporosis, while bone-marrow fat can tell you about the nutritional status of the animal. 3. Urine can tell you about the animal's nutritional status.

Which community would support the greatest diversity of species - a community comprised of species with broad ecological niches or a community comprised of species with narrow, specialized ecological niches? Explain.

A community comprised of species with narrow, specialized ecological niches would support the greatest diversity of species because having a narrow niche means there are many niches available for other specialized species.

What is the difference between a community and an ecosystem?

A community consists of interacting populations of different species, while an ecosystem consists of both the living and the non-living components of the environment.

What is the difference between exponential growth and logistic growth? Which type do most populations exhibit?

Exponential growth describes a population that increases by the same percentage in every generation. Logistic growth describes a population that increases quickly at first, then growth slows because the environment has limited resources, and eventually, the population will reach carrying capacity. Most populations exhibit logistic growth.

You are studying 2 populations of rabbits living in similar habitat. The first population has 1000 individuals/km, & the second population has only 100 individuals/km. You notice that when factor A is present, half the rabbits die in each population. When factor B is present, 20% of the first population die & none of rabbits in the second population die. Which factor is density dependent & which factor is density independent? Explain.

Factor A must be density independent because half the rabbits died, regardless of the difference in population density, while factor B must be density dependent because it did not affect the lower-density population.

You are discussing population growth with a colleague who says that once you know how many deer can live in 100 square miles in your area, then you know that's the same number of deer that can live in 100 square miles anywhere in the country. Do you agree or disagree? Explain.

I would disagree because every area differs in the number of resources it can provide. Thus, the carrying capacity of our area can differ from location to location.

Mice eat fruits, nuts, & insects, while foxes eat fruits, nuts, ' insects as well as mice. Speculate on what would happen to the abundance of mice, fruits, nuts, & insects if foxes are removed from the community.

If foxes are removed, then mouse populations will increase & consume more fruits, nuts, & insects causing their abundance to decrease.

What is a keystone species & why are they so important?

Keystone species are species that perform functions that have a great effect on many other species in an ecosystem, either directly or indirectly. Without them, entire communities could collapse.

Humans domesticated dogs 10,000 years ago. Of the 3 types of symbioses possible, which do you think best characterizes this relationship? Explain.

Man's relationship with dogs is mutualistic. The dogs benefit by gaining consistent food & shelter, while man benefits by gaining companionship as well as help in hunting & farming activities & being alerted to danger.

You are interested in the population size of 2 species of caterpillars. One caterpillar has a very specific diet, feeding exclusively on only 3 species of tree, while the other has a very broad diet, feeding on 15 species of tree. Which caterpillar species will be easiest to count? Explain.

The caterpillar that feeds on only 3 species of tree will be easier to count because only those trees provide appropriate habitat. Therefore, fewer trees need to be searched and those that are searched will yield a fairly accurate estimate of population size.

If only 10% of the energy available in a plant is turned into body tissue of a cow, what happens to the other 90%?

The other 90% of the energy is burned as fuel, is given off as heat, or is passed through the cow as indigestible plant fiber.

Two non-native species of bees are introduced into a new ecosystem. One species has a broad ecological niche, while the other has a narrow specialized niche. Which species is most likely to be successful in the new environment? Explain.

The species with a broad ecological nice is more likely to be successful than the species with a specialized niche because the specialized niche may already be occupied by native species already present, while a broad niche will allow a species many opportunities for meeting its requirements for survival & reproduction.

Write M (mutualistic), C (commensalistic), or P (parasitic) for the following symbiotic relationships:

- the varroa mite on a bee (P) - bees in a hollow of a tree (C) - bees and flowering plants (M) - an orchid on a rainforest tree (C) - protists in termites (M) - tapeworm in humans (P) - clown fish & sea anemone (M) - humans & malaria causing Plasmodium (P) - barnacles on a whale (C)

Which do you think would be a more stable ecosystem: one where each species have five connections to other species? Explain.

An ecosystem in which each species have five connections to other species is likely to be more stable than one in which each species is connected to only one other species because the more connections that are present the more resistant the ecosystem is to changes. In an ecosystem where each species is connected to only one other species, any event that happens to break a link will cause the entire ecosystem to fail.

A school of fish demonstrates which pattern of distribution?

Clumped

Explain how temperature, ticks, moose, and wolves are all related.

Warm temperature favors ticks, resulting in high tick populations living on moose. Because of the high tick infestations, moose lose hair and blood. The warm temperatures also mean moose spend a lot of time resting, which means they are not feeding. Between hair loss, blood loss, & little food, moose become weaker & easier for wolves to kill, so the moose population declines while the wolf population increases briefly. However, in a few years, the wolf population also will begin to decline as moose numbers drop.

Many predators have been hunted, trapped, or poisoned & are now absent from many ecosystems they inhabited 100 years ago. Why do conservationists make great efforts to reintroduce predators to these ecosystems? Specifically, what is it about predators that makes for a healthy ecosystem?

When prey animals, such as herbivores, reach high population levels, they limit the ability of their own food, the plants, to grow. The means less food for all species that depend on those plants. By introducing predators, prey populations fall, which in turn allows the plants to recover, grow, & reproduce. Furthermore, the decaying carcasses of dead animals return nutrients to the soil, which the plants then use to increase their own growth rate. Thus, predators help maintain the health of all life forms in an ecosystem.

Predator cycles usually peak shortly after prey cycles peak. Why do you think this is?

When prey are at their most abundant, there is a lot of food for predators whose survival & reproduction rates increase. Then as prey animals are consumed by a large # of predators, prey abundance falls & there is less food for more predators. Predator populations then fall shortly after prey populations fall. Thus, the population cycles are always slightly out of sync.

Given what you know about moose & wolf ecology on Isle Royale, would you consider one of these species to be a keystone species? If so, which one? Explain.

Wolves are keystone species because they keep the moose population down, which means vegetation remains abundant & healthy & able to provide food & shelter to a variety of other animals.