Organism Interactions and Population Dynamics 1. Which of the following interactions is an example of symbiosis? A. a population of hummingbirds migrates during the summer B. a mother bear feeds and protects her cubs C. a tropical bird performs a courtship dance for a mate D. an insect acts as a pollinator for a plant species 2. Populations of typical prey animals, such as deer, might exceed the carrying capacity of an ecosystem if top predators, such as mountain lions, are removed. Without the mountain lions, increased numbers of deer may reduce the food supply available to other herbivores, such as field mice and crickets. As a result, populations of deer, mice, and crickets might decline, causing a population decrease in species that feed on these organisms as well. This example implies that properly functioning predator/prey relationships A. harm all of the organisms in an ecosystem. B. can throw an ecosystem out of balance. C. maintain balance within an ecosystem. D. result in food shortage for the entire ecosystem. 3. If sunlight were suddenly limited in an ecosystem, what might result? A. Plants and animals will flourish because the ecosystem is not so hot. B. There will be less chemical energy available in that particular ecosystem. C. Plants will die, but animal diversity in that ecosystem will increase. D. Nothing will change.
4. Two populations of birds in the same ecosystem begin to compete for the same food resources. What will most likely be the result of this interspecific competition? There will be an increase in the population size of one or both species. A. One or both species will emigrate to a new ecosystem. B. One or both species will stop utilizing the shared food resources. C. There will be a reduction in the population size of one or both species. D. 5. Which of the following events would most likely contribute to lowering the carrying capacity of a population? A. a decrease in habitats due to human development or natural disasters B. an increase in the number of predators who eat the animal C. an increase in the water supply in the habitat D. a decrease in the number of females in the population 6. Technology Enhanced Questions are not available in Word format. 7. Theoretically, living organisms are capable of producing populations of infinite size. However, this never occurs because population sizes are limited by. A. organism interactions and behaviors B. the availability of resources C. environmental conditions D. all of these
8. Almost no species ever reaches its biotic potential the population size that the species could produce if all individuals survived and produced offspring. Anything that prevents the species from reaching its biotic potential is called a A. producer. B. limiting factor. C. capacity limiter. D. symbiote. 9. Technology Enhanced Questions are not available in Word format. 10. Plants require nitrogen and phosphorous but cannot efficiently absorb these nutrients from the soil. Instead, they obtain the nutrients through fungi that live in their roots. In return, the fungi have access to carbohydrates manufactured by the plants. Without the fungi, plants would not be healthy and abundant, and the food supply of all of the organisms in the ecosystem would be in danger. This is an example of how relationships maintain balance within an ecosystem. A. divergent B. competitive C. symbiotic D. abiotic 11. Technology Enhanced Questions are not available in Word format. 12. Technology Enhanced Questions are not available in Word format.
13. Which of the following is an example of predation? a tapeworm lives in the intestine of a cat and absorbs nutrients for energy A. an owl hunts, catches, and consumes a field mouse for energy B. a white-tailed deer consumes a plant in the forest for energy C. a tick attaches to the flesh of a dog and consumes its blood for energy D. 14. Which of the following is an abiotic factor that limits the carrying capacity of animal species? A. a competing species B. breathable gases C. increasing number of predators D. disease-causing bacteria 15. Which of the following statements is true of all organisms in every environment? A. They must consume other organisms for energy. B. They must compete for essential resources. C. They avoid interaction as much as possible. D. They are able to produce their own food. 16. The main predators of field mice in a certain ecosystem are rattlesnakes and foxes. Suppose humans begin building neighborhoods in the ecosystem, driving out many of the indigenous rattlesnakes and foxes. What will most likely happen to the field mice's population? A. The population will increase in size. B. The population will occupy an entirely new niche. C. The population will not be affected by the change. D. The population will decrease in size. 17. Which of the following is a biotic factor that limits the number of deer in an ecosystem? A. temperature B. a predator C. drought D. flooding 18. Technology Enhanced Questions are not available in Word format.
19. The graph below shows population data for two species. What can be said about the relationship between species 1 and species 2? A. When the population of species 1 increases, the population of species 2 decreases. B. The population of species 1 is not influenced by the population of species 2. C. When the population of species 1 increases, the population of species 2 increases. D. The populations of species 1 and species 2 stay the same over the time period shown.
20. All organisms must be able to obtain nutrients from their environment. Which of the following terms describes the process of one organism killing another organism in order to obtain nutrients? A. secondary trophism B. coevolution C. symbiosis D. predation 21. Chemicals can affect an ecosystem. Which of the following is a result of pesticide application? Pesticide application does not affect ecosystems. This is why it is widely used on farms and ranches. A. It always leaves a residue on plant leaves, reducing photosynthesis. B. C. Pesticide kills all kinds of insects, including predatory insects, which in turn can increase the population of insects for which the pesticide was intended. Pesticide application improves soil fertility, increasing the diversity of plants in the ecosystem. D. 22. A population includes every member of a particular species. The growth of this population is limited by the availability of water in the ecosystem. The population has many food sources available to it. This species might become extinct if A. food became the limiting factor for the population. B. a disease eliminated one of the population's food sources. C. a new food source was introduced to the ecosystem. D. a long drought caused water to become scarce.
23. Predation is the act of one organism killing another for food. Which of the following sets of organisms list a predator and its prey? A. scorpion, beetle B. deer, rabbit C. lion, beaver D. cod fish, squid 24. If a disease killed all of the frogs in the above food web, which population would be most directly affected in a negative way? A. insects B. owls C. hawks D. mice
25. Organisms in an ecosystem must either produce their own energy or receive energy from other organisms. The biological interaction in which one organism hunts, kills, and eats another organism for energy is known as. A. commensalism B. mutualism C. predation D. parasitism 26. Technology Enhanced Questions are not available in Word format. 27. A farmer plants two species of grass with similar nutrient needs on the same small plot of land. What kind of interaction will most likely occur between the two species? A. parasitism B. competition C. mutualism D. commensalism
28. An algal bloom is a sudden and dramatic increase in the population of certain microorganisms such as algae or cyanobacteria in a body of water. When there are high levels of nutrients in the water, microorganisms will reproduce rapidly until they have used all the available resources. At that point, the algae dies off in tremendous quantities, vastly reducing the amount of oxygen in the water as it dies and begins to decompose. The image to the far left is a photograph of an algal bloom using visible light. The image to the immediate left shows the concentrations of chlorophyll present in the water, which is an indication of the amount of algae present. Image from NASA's Earth Observatory What impact, if any, would an algal bloom be likely to have on its local ecosystem? It would have no effect on the ecosystem because ecosystems are self-balancing. A. It would have no significant effect on the ecosystem since the algae dies off by itself after a time. B. It would help the ecosystem by providing extra algae for primary consumers to eat. C. It would kill many other organisms in the ecosystem by removing oxygen and nutrients from the water. D. 29. White-tailed deer are considered to be an overpopulated species in the central United States. Which of these events probably contributed the most to white-tailed deer exceeding their carrying capacity? A. a large increase in available grassland B. the occurrence of a genetic mutation that prevented breeding C. the water supply in the habitat remained steady D. a decrease in natural predation of white-tailed deer
30. The mouse population in a forest ecosystem becomes too large, and many individuals die from disease. Disease is a(n) limiting factor in this ecosystem. A. intolerance B. independent C. biotic D. abiotic Answers 1. D 2. C 3. B 4. D 5. A 6. -- 7. D 8. B 9. -- 10. C 11. -- 12. -- 13. B 14. B 15. B 16. A 17. B 18. -- 19. A 20. D 21. C 22. D 23. A 24. B 25. C 26. -- 27. B 28. D 29. D 30. C Explanations 1. Symbiosis is an interaction between individuals of different biological species. At least one of the organisms receives a benefit from the interaction. The other organism can either receive a benefit, be harmed, or not be affected in any way. An insect acting as a pollinator for a plant species is an example of symbiosis because organisms of two different species are involved. Flowering plants and their pollinators have a special type of symbiotic relationship known as mutualism because both organisms involved receive a benefit. 2. Predator/prey relationships help maintain balance within an ecosystem.
When one species that usually participates in a predator/prey relationship is removed, populations of the other species can quickly exceed the available food supply. This could also cause decreases in populations of other organisms. 3. Plants use energy from the sun and, through photosynthesis, convert solar energy into chemical energy that can be used by other organisms. Logically, there will be less chemical energy available if plants do not have enough sunlight to perform photosynthesis. 4. Competition between two or more species for the same resources limits the population size of at least one, if not both, of the species involved in the competition. 5. Carrying capacity describes the number of organisms that can be supported by a given habitat within its limits of space, food, water, and other resources. Long-term changes to available resources affects the carrying capacity. When the availability of any of these factors declines, the carrying capacity will also decline. These are a few of the possible events that could contribute to a decrease in carrying capacity. a decrease in space in the habitat due to human development or natural disasters a decrease in the availability of water due to the construction of a dam a decrease in the amount of sunlight in the habitat, which affects the growth of producers 6. -- 7. Even though living organisms are capable of producing populations of infinite size, they are ultimately limited by organism interactions and behaviors (e.g., cooperation, competition, etc.) the availability of resources, such as food, water, and shelter environmental conditions, which, in turn, may be affected by natural causes (e.g., tornado, fire, flood) or human causes (e.g., pollution, deforestation) 8. Generally, the population size of species in an ecosystem is kept in check by biotic and abiotic elements called limiting factors. Biotic limiting factors could be predators, disease, or the absence of an adequate food supply. Abiotic (nonliving) limiting factors include inhospitable temperatures, a limited supply of breathable gas (oxygen for animals and carbon dioxide for plants), and a limited water supply. 9. -- 10. Symbiotic relationships are essential for maintaining balance in an ecosystem. Over time, species have developed beneficial or cooperative relationships. As a result, other species that can take advantage of those relationships have developed. For instance, all animals take advantage of the beneficial relationship between plants and the fungi that live in plant roots. 11. -- 12. -- 13. The biological interaction in which one organism (the predator) hunts, kills, and eats another organism (the prey) for energy is known as predation. Predators use their prey as a source of food. Predation is different from parasitism because the prey is killed immediately for consumption. During parasitism, the host is kept alive for a long period of time so that the
parasite can continue to receive nutrients from the host. An example of predation is an owl hunting, catching, and consuming a field mouse for energy. 14. Biotic factors are all the living things that make up an organism's environment. Abiotic factors are all of the nonliving things in the organism's environment. The availability of food is a biotic factor that limits the carrying capacity of any given animal species in an ecosystem. The presence of breathable gas is an abiotic factor that limits the carrying capacity of a species. 15. In all environments, organisms must compete for essential resources because the quantities of these resources are limited. Examples of essential resources include food, water, sunlight, and shelter. Also, every population must interact with and is linked, directly or indirectly, with many others. For example, some organisms are able to produce their own food, while others must consume other organisms in order to acquire energy. 16. Predators help control the population size of their prey. If there are fewer predators in an area, the size of the prey population will likely increase. 17. Drought, flooding, and temperatures are nonliving (abiotic) weather patterns that could result in a smaller deer population. A predator is a biotic (living) factor that limits the number of deer in an ecosystem. 18. -- 19. The graph shows that as the population of species 1 increases, the population of species 2 decreases. This might imply a predator-prey relationship between the two species. The other possibility is that the two species are competing for food or other resources as they would if they were trying to occupy the same niche. 20. Predation is the act of one organism killing another for food. Common examples of predation include a fox eating a chicken and a cat eating a mouse. 21. Applying pesticide has many effects, including killing the insects for which the pesticide was applied to begin with. It kills insects indiscriminately, including predatory insects that keep the populations of other insects under control. It can also create a strain of pesticide-resistant insects. 22. A limiting factor is a resource that limits the growth of a population. The limiting factor for the population described in the question is water availability. This means that the carrying capacity in the ecosystem for this population is determined by how much water is available, no matter how much food, space, or shelter the population has access to. Since the population has numerous food sources, the elimination of one food source would not likely cause the species to become extinct. A long drought that caused water to become scarce, however, might lead to species extinction. 23. For organisms to be able to interact with one another, they must live in the same ecosystem. While a lion might possibly consume a beaver if it ever encountered one, beavers are not natural prey to lions because they do not cohabit the same environment. Deer and rabbit are both herbivores. Cod fish and squid both eat algae and plankton. Scorpions eat beetles, spiders, and even other scorpions.
24. Every population is linked, directly or indirectly, with many others in an ecosystem. Disruptions in the numbers and types of populations and environmental changes can upset ecosystem stability. In this case, frogs are most directly linked to insects and owls. If a disease killed all of the frogs in the food web, the owl population would be negatively affected since they would no longer be able to feed on frogs. The insect population, on the other hand, would be positively affected since they would no longer be eaten by frogs. 25. The biological interaction in which one organism (the predator) hunts, kills, and eats another organism (the prey) for energy is known as predation. Predators use their prey as a source of food. Predation is different from parasitism because the prey is killed immediately for consumption. During parasitism, the host is kept alive for a long period of time so that the parasite can continue to receive nutrients from the host. An example of predation is a wolf pack hunting, killing, and consuming a deer. 26. -- 27. Competition takes place when two or more organisms or species within an ecosystem seek the same resource. Since the two species of grass have similar nutrient needs, they will be competing with one another for the nutrients available in the soil of the plot of land. Whichever species is better adapted to take in nutrients under the specific conditions present on this plot will most likely outcompete the other species and eventually take over the area. 28. Algae reproduce until they run out of nutrients or sunlight, then remove oxygen from the water when they die and decompose. Since other organisms rely on this same limited supply of oxygen and nutrients for survival, algal blooms result in killing many other organisms in the ecosystem. Algal blooms often kill large numbers of fish. They can destroy other plant life by blocking sunlight and using up the nutrients. In addition, some microorganisms produce toxins that spread through the food chain and poison some of the higher consumers, including humans. 29. White-tailed deer have exceeded their carrying capacity by exceeding the limits of space and food provided by their habitat. A population that exceeds its carrying capacity is considered to be overpopulated. One explanation for the growth of white-tailed deer populations is that the number of predators in the habitats of white-tailed deer have declined over time. 30. A limiting factor is something that prevents a population of organisms from reaching its biotic potential the population size that a species could produce if all organisms survived and produced offspring. Biotic factors are all the living things in an ecosystem. Disease is a biotic limiting factor because it is caused by living microorganisms.