ebio exam 4

Part complete Interspecific interactions can be categorized by whether each species in the interaction benefits, is harmed, or is neither helped nor harmed. Competition is a -/- interaction, meaning that it has a negative effect on both species. Mutualism, parasitism, and commensalism are types of interspecific interactions in which at least one species benefits. Three examples of symbiosis are epiphytic orchids and trees, hookworms and humans, and rumen bacteria and cows. Epiphytic orchids are plants that live on the branches or trunks of trees. The trees supply the orchids with space, and the orchids (which are autotrophs) do not appear to affect the tree. Human hookworms live in human intestines and eat blood. Rumen bacteria allow for digestion of cellulose in the cow's diet; in turn, the bacteria are supplied with nutrients. Categorize mutualism, parasitism, and commensalism as either +/-, +/0, or +/+. Also select the correct definition and example for each interaction.

+/- interaction: -parasitism -one species benefits by harming another -hookworms and humans +/0: -commensalism -one species benefits; the other is unaffected -spiphytic orchids and trees +/+ interaction -mutualism -both species benefit -rumen bacteria and cows Parasitism is a +/- relationship, in which one organism benefits by harming another organism. For example, some species of hookworms enter a human host and eat blood. The hookworm benefits and the host is harmed by the loss of blood. Commensalism is a +/0 relationship, in which one organism benefits and the other organism neither benefits nor is harmed. For example, epiphytic orchids live on tree branches or tree trunks. The trees provide habitat for the orchids but usually are not affected by the orchids. Mutualism is a +/+ relationship in which both organisms benefit. For example, rumen microbes allow cows to digest grass, and the microbes benefit from a steady supply of nutrients.

Consider the following food chain: grass → grasshopper → mouse → snake → hawk How much of the chemical energy fixed by photosynthesis of the grass (100%) is available to the hawk?

.01%

In the 250 years from 1500 to 1750, the atmospheric concentration of methane (CH4) hovered around 700 parts per billion. What was the approximate concentration of methane 250 years later, in 2000?

1,800 parts per billion

A hypothetical bat species (species 1) lives in a city. Another hypothetical bat species (species 2) established a population in the same city after a number of individuals escaped from a zoo. In isolation, each species prefers to roost in buildings that are three or more stories tall. After species 2 became established in the city, species 1 began roosting only in buildings less than three stories tall, whereas species 2 roosted in buildings three or more stories tall. Observers determined that the bright streetlights at ground level had previously deterred most bats from roosting in shorter buildings. Over many generations of existing in the same city with species 2, species 1 showed changes in eye size and retina structure. Complete the following statements about the two bat species.

1. Roosting areas in buildings of any height are the fundamental niche of species 1 2. Interspecific competition between the two bat species occurs because both species prefer the same roosting areas. 3. In parts of the city with only tall buildings (over two stories), competitive exclusion of species 1 may occur. 4. Roosting areas in buildings that are one to two stories tall are the realized niche of species 1 when species 2 is present. 5. The change in the roosting habits of species 1 after species 2 became established in the city is an example of resource partitioning. 6. The competition between the species for roosting areas is an example of a -/- interaction. 7. The changes in the eyes of species 1 are examples of character displacement. Two species that have identical niches cannot coexist in the same area. Competition between the species may cause them to use different niches (resource partitioning). In this example, resource partitioning is shown by bat species 1 roosting in short buildings (one to two stories) and bat species 2 roosting in tall buildings (three or more stories) when both species are present in the city. In the absence of resource partitioning, the inferior competitor may become locally extinct (competitive exclusion). Over many generations, competition may also cause a change in the characteristics of competing species (character displacement), as illustrated by the changes in eye structure of species 1.

What was the approximate atmospheric concentration of CO2 at year 0?

275 parts per million

Which of the following describes a proximate cause of a behavior?

A female bird lays its eggs because the amount of daylight is decreasing slightly each day, which causes the release of maternal hormones.

Which of the following statements is supported by the graph?

All of the computer-generated forecasts predict some global warming, but reducing the level of CO2 emissions will significantly slow the rate of increase.

Which of the following is an ultimate cause for a bird's behavior?

Birds who breed in the spring produce the most surviving offspring.

A study found higher mortality of old trees at the edges of habitat fragments because the edges of these fragments experienced more wind. More trees were knocked over due to the increased wind. This led to less competition between old trees and young trees for light and water at the edges of these fragments, and, as a result, more young trees were able to grow. Now these fragments have a higher proportion of young trees as compared to non-fragmented habitats. This increase in the proportion of young trees in habitat fragments is due to:

Both abiotic and biotic factors Increased wind is the abiotic factor, and reduced competition with other trees is the biotic factor.

During a field trip, an instructor touched a moth resting on a tree trunk. The moth raised its forewings to reveal large eyespots on its hind wings. The instructor asked why the moth lifted its wings. One student answered that sensory receptors had fired and triggered a neuronal reflex culminating in the contraction of certain muscles that raised the wings. A second student responded that the behavior frightens predators and that this allows the moth to escape. Which statement best describes these explanations?

C) The first explanation refers to proximate causation, whereas the second refers to ultimate causation. It is clear that the first explanation simply describes mechanistically how a wing display is achieved. The second explanation is more of an evolutionary explanation because it assumes that the display is associated with a benefit (which could in theory lead to those that displayed such a trait having more offspring). If the second explanation was a proximate explanation, it would simply state, "the wing spots startled the bat".

In 2050, the atmospheric concentration of CO2 will be 400 ppm.

Cannot be determined from this graph

The energy that flows through most ecosystems comes from the sun. Primary producers convert a fraction of the sun's energy into chemical energy, which can be used by consumers. Food webs describe how energy flows between trophic levels in an ecosystem, and a trophic pyramid represents the amount of energy available at each trophic level.

Detritus: -rotting log -dead animal primary producer: -living maple leaves primary comsumer/decomposer: -fungus -cricket -maggots secondary consumer: -earthworm -millipede both secondary and tertiary consumer: -alligator lizard -robin Primary producers (autotrophs) and detritus, such as decaying plant material, are at the lowest trophic level in a food web. Primary consumers and decomposers (detritivores) rely on primary producers and detritus, respectively, for energy and organic compounds. Secondary consumers eat primary consumers and decomposers, and tertiary consumers eat secondary consumers. When an organism dies, its chemical elements are recycled, becoming available to the food web at low trophic levels once again.

How did the global surface temperature change between 1900 and 2000?

It increased by about 0.7 °C.

The average age of childbearing in country A is 26, whereas the average age in country B is 30. In each country, the average number of offspring per woman is 3. Which of the following statements about the population growth rate in each country must be true?

It is not possible to compare the population growth rates of countries A and B because the death rates in each country are unknown.

According to the Business as Usual scenario, how will the global surface temperature change in the century between 2000 and 2100?

It will increase by about 3.5 °C.

Which gas is plotted using the y-axis on the right?

Methane (CH4)

After 1800, the atmospheric concentration of methane rose dramatically, but concentrations of the other gases remained constant.

Not supported

Which of the following statements about age pyramids is true?

Predictions of a population's future take into account such factors as increasing survivorship and fecundity levels that remain the same. These factors give clues about future public policy concerns in the population.

Carbon dioxide, nitrous oxide, and methane all had relatively stable atmospheric concentrations before 1800.

Supported

From 1900-2000, the atmospheric concentration of CO2 rose from approximately 300 ppm to 350 ppm.

Supported

Fig. 3. (A) Changes in sea otter abundance over time at several islands in the Aleutian archipelago and concurrent changes in (B) sea urchin biomass, (C) grazing intensity, and (D) kelp density measured from kelp forests at Adak Island. Error bars in (B) and (C) indicate 1 SE. The proposed mechanisms of change are portrayed in the marginal cartoons the one on the left shows how the kelp forest ecosystem was organized before the sea otters decline and the one on the right show this ecosystem changed with the addition of killer whales as an apex predator. Heavy arrows represent strong trophic interactions; light arrows represent weak interactions. The declines in the sea otter populations have affected the community of organisms found off the shores of the different islands. From Figure 3 above, what can you conclude? (Follow the arrows) Given Figure 3, what might you expect sea otters to find if they just dispersed to an island from which they had not been present in the last 100 years?

That an increase in sea otter numbers strongly reduces the biomass of urchins which reduces the grazing intensity of urchins on kelp It would be a habitat with many urchins but with little to no kelp forest

The flow of energy through an animal is directly related to the flow of energy through the trophic levels of an ecosystem. Energy flow through trophic levels is shown using a diagram called the pyramid of net production, where net production is the amount of energy that is converted to new biomass at each trophic level. The figure below shows an idealized pyramid of net production in an imaginary ecosystem. In this ecosystem, primary producers convert 1% of the sunlight energy available to them to net production. Then, 10% of the net production of primary producers is transferred to the net production of primary consumers -- that is, the trophic efficiency is 10%. Similarly, 10% of the net production of primary consumers is transferred to the net production of secondary consumers, and so on. What does a pyramid of net production look like in a real ecosystem, and what are the trophic efficiencies? The pyramid below represents the data collected from H. T. Odum's work on the Silver Springs ecosystem in north-central Florida. (Note that Odum used the units kilocalories [kcal] instead of joules [J].)

The idealized pyramid of net production uses the typical values of 1% for the conversion of sunlight energy to net primary production and 10% for trophic efficiency. In real ecosystems, trophic efficiencies usually vary from about 5% to about 20%. The numbers for the Silver Springs ecosystem fall within this range.

In 1970, the average age of childbearing was 28, and the average number of offspring per woman was 3 in a certain country. In 1980, the average age of childbearing was still 28, but the average number of offspring per woman was 2 in that country. If the death rate in the country remained constant during those years, how did the population growth rate change from 1970 to 1980?

The population growth rate decreased. Reducing the average number of offspring per woman decreases the population growth rate. Return to Assignment

What does the yellow line represent?

Today's World: The amount of global warming that is likely to occur if CO2 emissions cease immediately and CO2 concentrations continue at their current level.

The carbon cycle describes the cycling of carbon between Earth's biotic (living) and abiotic (nonliving) reservoirs. Identify the major reservoirs and processes in the carbon cycle by labeling the diagram below.

a) CO2 in atmosphere b) photosynthesis on land c) photosynthesis in ocean d) cellular respiration e) plants f) burning fossil fuels g) consumers h) decomposers The carbon cycle describes the cycling of carbon between Earth's abiotic and biotic reservoirs.Photosynthesis is the main process that transfers carbon from abiotic reservoirs to living organisms.Cellular respiration is the main process that transfers carbon from living organisms back to abiotic reservoirs.However, the burning of carbon-containing materials (such as fossil fuels and wood) also returns significant amounts of carbon to the atmosphere.

If an ecologist was interested in how changes in dryness, temperature and soil chemistry in certain habitats impact survival of juvenile lizards, they are studying the effects of __________________ factors.

abiotic Dryness, temperature and soil chemistry are abiotic factors.

What are population dynamics?

changes in populations through time

A graduate student is studying how multiple species of ants respond to the fragmentation of their habitat. Ants compete for food and territory but are also affected by abiotic factors such as solar radiation, which warms their bodies and nests to different degrees depending on body size and coloration. The student has hypothesized that increased solar radiation in smaller habitat fragments will favor one particular ant species, increasing their ability to outcompete the other ant species in that same area. This question focuses on what subfield of ecology?

community This study is community ecology because it focuses on multiple species of ants that interact via competition for resources and territory.

A post-doctoral researcher is studying how the rate of nutrient cycling of nitrogen and carbon is different in small Eucalyptus forests as compared to much larger Eucalyptus forests. This question focuses on what subfield of ecology?

ecosystem Ecosystem ecology focuses on the interaction between communities and the abiotic environment, and particularly focuses on nutrient cycling and energy flow.

What information is presented on the y-axis of the graph?

global surface warming, in °Celsius

For a hypothetical mouse population, determine whether the actions described will increase K, decrease K, or not affect K.

k increases: -a main competitor for food is eliminated increasing food availability -an abandoned building creates more nesting areas k decreases: -wetlands are drained, decreasing the amount of available water -a parking lot is built, shrinking the habitat -a species with the same food requirements is introduced no effect on k: -offspring live longer

An ecology research project aims to understand how reducing habitat size impacts extinction rates of a beetle species. Relevant data include the number of beetles that are captured over time in habitats of different sizes. This question focuses on what subfield of ecology?

population It is population ecology because the study focuses on how the number of individuals in a population changes in time and ultimately whether the number decreases to zero (extinction).

Which line is not a computer-generated forecast?

the black line representing 20th century data

True or false? The growth rate of a certain population increases very quickly for a time and then levels off to zero. The most likely reason that the growth rate leveled off to zero is that the population reached the carrying capacity of that environment.

true The resources available to any population are always limited; once a population reaches the carrying capacity of its environment, its growth rate will level off to zero.