BIO 191 CH 41 HW

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. Drag the labels to their appropriate locations on the table. Use blue labels for the blue targets, pink labels for the pink targets, and white labels for the white targets.

+/- Interaction: a. parasitism b. one species benefits by harming another c. hookworms and humans +/0 Interaction: d. commensalism e. one species benefits; the other is unaffected f. epiphytic orchids and trees +/+ Interaction: g. mutualism h. both species benefit i. 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.

During which period were forest fires most extensive? 1700-1750 1750-1800 1800-1850 1850-1900

1700-1750

In 1770, how much of the landscape did the thinning stage occupy? 15% 25% 50% 50 square miles

50%

You have selected the following prediction to test: Previously thinned forests will have higher tree survival than adjacent forests that were not thinned. Now you need to define the key variables that you will use to test this prediction. For the following variables, sort them as independent variables, dependent variables, or variables that should be controlled (held constant). See the hints for more information about variables.

Independent: -thinning or no thinning before the fire Dependent: -tree survival rate after the fire Controlled Variable: -elevation of the site -dominant tree species Now that you have a specific, testable hypothesis and a clear understanding of the variables that you will use in your study, you are ready to start developing a detailed experimental design.

Which of the following is the most likely explanation for how prescribed burning reduces fire severity? It lowers the oxygen concentration in that part of the forest so that a wildfire never reaches the critical heat required to kill most of the trees. It stimulates the tree to produce thicker bark that is more fire resistant. It kills off shrubs, allowing young trees to establish and grow.It deposits a layer of ash on the forest floor that insulates it from future wildfires. It reduces the amount of fuel on the ground so that a wildfire never reaches the critical heat required to kill most of the trees.

It reduces the amount of fuel on the ground so that a wildfire never reaches the critical heat required to kill most of the trees. Prescribed fires burn along the ground, consuming "forest fuels" such as ground vegetation and twigs, smaller branches, and bark from fallen trees. This reduces the amount of fuel available to a subsequent wildfire. As a result, a wildfire in a previously prescribed burned area never reaches the critical heat required to kill most of the trees.Think of a campfire. If you throw on an armful of branches and twigs, the flames might tower above you. In contrast, a few sticks would keep the fire small and manageable.The final and most important step of your study is to disseminate the results to forest managers so they can work to reduce the likelihood of future large, out-of-control wildfires that kill nearly all of the trees. Based on your study, thinning alone is not effective in reducing wildfire severity. To capture the full benefit of thinning, they will need to also use prescribed burning to reduce forest fuels.

Drag the images of the left half of the rock (white) and right half of the rock (blue) to indicate which barnacle species (if any) would be present at the end of the summer if niche differentiation had occurred between Chthamalus and Balanus.

Left: -Balanus only Right: -no barnacles

Rank each of the following forests by how much they would benefit from a prescribed burn.

Low Benefit -Trees -Trees / small trees -Trees / small tress / logs -Trees / small trees / logs / dead trees High Benefit

Which of the following best describes the Yellowstone Plateau landscape in 1900? More than half of the landscape was covered by forests made up of mature shade-tolerant trees. Most of the landscape was occupied with forests made up of young lodgepole pines. All of the forest stages occupied about the same amount of area. More than half of the landscape was occupied by forests in which shade-tolerant trees were becoming established.

More than half of the landscape was occupied by forests in which shade-tolerant trees were becoming established.

An interesting observation made by the firefighters was that some parts of the forest seemed to escape the flames. The crown fire would drop down into a ground fire in these areas, and then jump back up into the canopy as the fire burned into adjacent areas. They observed that many of these areas had previously been thinned, which means that some of the trees were cut down and hauled away to be used as timber. In other areas, thinned forests burned with as much severity as the unthinned forest. Your objective is to design an observational study to help answer the question: What was the determining factor for areas that escaped the worst impacts of the fire, compared to areas that were severely burned? Select the best hypothesis and prediction that follow from the question you're trying to answer. For help getting started, see the hints.

Question: Why were some areas severely burned while others were not? Hypothesis: Thinning accounts for observed differences in the rates of tree survival. Prediction: Previously thinned forests will have higher tree survival than adjacent forests that were not thinned. A fundamental tenet of the scientific method is to develop hypotheses based on careful observations and/or previous research. In this case, observations during and after the Tripod fires provided a sound foundation for hypothesizing that thinning accounts for the tree mortality differences observed in different areas of the forest.It is easy to think you see a pattern, but you may be fooled by only looking at a few examples. You cannot know for certain whether an observed pattern is representative until you perform rigorous testing using a carefully designed, replicated study.

Which of the following choices would be the most logical third step in Connell's experimental procedure, permitting him to either accept or reject his hypothesis of competitive exclusion?

Remove Balanus from one half of the transplanted rocks

Based on this graph, what is the best conclusion about the effect of thinning on fire severity? For help understanding the error bars, see the hints. For help understanding the error bars, see the hints. It is impossible to tell whether thinning has an effect or not. Thinning significantly reduces the tree survival rate compared to the control plots. Thinning appears to have no significant effect compared to the control plots. Thinning significantly increases the tree survival rate compared to the control plots.

Thinning appears to have no significant effect compared to the control plots.

What conclusion can you draw from this graph? Thinning plus prescribed burning appears to have no significant effect compared to the control and thinned treatments. Thinning plus prescribed burning significantly reduces the tree survival rate compared to the control and thinned treatments. Thinning plus prescribed burning significantly increases the tree survival rate compared to the control and thinned treatments. It is impossible to tell whether thinning plus prescribed burning has a significant effect compared to the control and thinned treatments.

Thinning plus prescribed burning significantly increases the tree survival rate compared to the control and thinned treatments. The plots that were thinned and prescribed burned had a significantly lower fire severity compared to the thinned-only and control plots, as measured by tree survival after the wildfire.

When interspecific interactions lead to competitive exclusion, the weaker competitor is forced to retreat to a more restricted niche (its realized niche) than it otherwise would inhabit in the absence of the competition (its fundamental niche). This is what happens between Balanus and Chthamalus. In the following diagram, label the fundamental and realized niches for Chthamalus. Note that one target should be left blank.

a. Chthamalus' realized niche b. Chthamalus' fundamental niche c. blank

An egret eats insects stirred up by grazing animals. Which of these terms applies to the relationship between the egret and the grazing animal? competition mutualism parasitism commensalism predation

commensalism In commensalism, one member of the species pair benefits and the other is unaffected; in this case the egret is getting a meal and the grazing animals are unaffected.

Humans and sharks both eat fish. Which of these terms applies to the relationship between the human and the shark? mutualism competition parasitism predation commensalism

competition The human and the shark are both competing for a resource (fish).

Humans who have pets tend to be healthier than humans who do not have pets. Which of these terms applies to the relationship between a human and a pet? competition mutualism commensalism parasitism predation

mutualism In mutualism, both members of the species pair benefit; in this case the human is healthier and the pet is getting room and board.

Which of these terms applies to the relationship between a dog and a blood-sucking tick? mutualism commensalism predation parasitism competition

parasitism The tick benefits at the expense of the dog; the dog is the host and the tick is the parasite.

A human eats a deer. Which of these terms applies to the relationship between the human and the deer? parasitism commensalism mutualism predation competition

predation The human is the predator and the deer is the prey.

The answer choices below show close-ups of the Tripod area. Which of the following sampling designs would be adequately controlled and most representative of the whole burned area? See the hints to review good sampling practices.

the one that has both control and thinned in both the north and the south goes up to control/thinned 4 Now that you have your hypothesis, your variables, and an experimental design to ensure that your data collection is representative and unbiased, it's time to start sampling.

What does the red graph line represent? establishment stage transition stage thinning stage old-growth stage

thinning stage

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. Drag the terms on the left to the appropriate blanks on the right to complete the sentences. Not all terms will be used. 1. Roosting areas in buildings of any height are the _______ of species 1. 2. _______ 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), ______ of species 1 may occur. 4. Roosting areas in buildings that are one to two stories tall are the _______ 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 _______. 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 ______.

1. fundamental niche 2. interspecific competition 3. competitive exlusion 4. realized niche 5. resource partitioning 6. -/- 7. 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.

Predation is an interspecific interaction in which one species benefits by eating another. Potential prey organisms have various adaptations that allow them to avoid or escape predators. The following examples demonstrate either mimicry, camouflage, mechanical defense, chemical defense, or schooling. Sort the examples based on the type of predator avoidance they demonstrate. Drag each example to the appropriate bin.

Mimicry: -viceroy and monarch butterflies (both unpalatable) look alike -hornet moth (harmless) resembles paper wasp (venomous) Camouflage: -an octopus assumes the color and texture of the seafloor Mechanical Defense: -rosebush thorns -sea urchin spines -snails have shells Chemical Defense: -skunk scent -jimsonweed toxins Schooling/Flocking: -flock of snow geese Camouflage may prevent a predator from noticing potential prey, such as an octopus that changes the color and texture of its skin to match its surroundings. Other species mimic dangerous or distasteful prey; predators avoid both the model and the mimic. Chemical and mechanical defenses include plant toxins and sea urchin spines, respectively. Flocking is a behavioral adaptation in birds and is analogous to schooling or herding in other species; it may reduce the chance that any individual prey animal will be eaten by a predator. Some species use more than one form of defense against predators. For example, deer forage for food in herds, and their young (fawns) have spotted fur that acts as camouflage. Beetles have a hard external skeleton and forewings, which provide a mechanical defense, and many secrete chemicals that make them unpalatable

After the 1988 fires, scientists made careful observations of the changes on the Yellowstone Plateau. The data they collected is not shown on this graph.Which of the following statements is most likely to have described the landscape in 2000? Use the trends shown in the graph to make your prediction. All of the forest stages would have occupied about the same percentage of the landscape. More than half of the landscape would have been occupied by lodgepole pines. More than half of the landscape would have been occupied by old-growth forest. It is not possible to make a prediction based on the data in this graph.

More than half of the landscape would have been occupied by lodgepole pines.

What does the y-axis show? percentage of landscape occupied by a forest stage time, in 50-year intervals relative frequency of forest fires between 1700 and 1988 total area occupied by a forest stage, in square miles

percentage of landscape occupied by a forest stage

Is this statement supported or not supported by the graph? Between 1700 and 1985, the dominant forest stage on the Yellowstone Plateau progressed from establishment stage to old-growth forest, in a pattern typical of secondary succession. supported not supported cannot be determined from the graph

supported