Ecology

1. Explain how birth, death, immigration, and emigration influence a population size. 2. Draw and explain exponential growth of populations. 3. Draw and explain logistic growth of populations. 4. Explain carrying capacity and what determines its value. 5. Explain how energy flows through an ecosystem. (10% law, trophic levels, biomass, Law of Conservation of Energy) Use an energy pyramid to illustrate this. 6. Use a food web to identify and distinguish producers, consumers and decomposers. 7. Explain the transfer of energy through the trophic levels of a food web. 8. Identify factors in an ecosystem that influence fluctuations in population sizes. 9. Analyze changes in population sizes and biodiversity resulting from natural causes, changes in climate, human activity, or introduction of a non-native species. 10. Explain how water, carbon, and nitrogen cycle between biotic and abiotic in an ecosystem, and how oxygen cycles between photosynthesis and cellular respiration. 11. Distinguish between five ecological relationships, including three types of symbiotic relationships. 12. State the characteristics of biomes and how these are organized on the planet.
 * Objectives**

Abiotic factor Biome Biotic factor Carbon cycle Carnivore Carrying capacity (K) Community Consumer Decomposer or Detritivore Ecological relationships Ecology Ecosystem Exponential growth Food chain Food web Glucose Growth rate (r) Habitat Herbivore Limiting factor Logistic growth Niche Nitrogen cycle Oxygen cycle Population Producer Ten Percent (10%) Principle Symbiosis Water cycle
 * Vocabulary**
 * Desert, Forest, Freshwater, Grassland/Prairie, Marine, Tundra
 * Photosynthesis, cellular respiration, combustion
 * Predation, Competition, Parasitism, Commensalism, Mutualism
 * ∆N = rN
 * r = (Pe-Ps)/Ps = b - d + i - e
 * Birth rate, death rate, immigration rate, emigration rate
 * ∆N = rN((K - N)/K)
 * Legume plant, nitrogen-fixing bacteria, nitrogen fixation, denitrification
 * Photosynthesis, cellular respiration
 * Transpiration, evaporation, condensation, precipitation, runoff

1. A simple food web is shown below. Which of the following is most likely to lead to the greatest decrease in the deer mouse population? A. an increase in the owl population B. an increase in the grass population C. an increase in the pine tree population D. an increase in the cottontail population
 * Sample MCAS Questions**

2. Which of the following is ALWAYS a result of immigration into a population? A. New individuals are added to the population. B. Some individuals are forced to leave the population. C. The survival rate of the individuals in the population increases. D. The genetic diversity among the individuals in the population decreases.

3. Part of a food web for a marine kelp forest is shown. Which of the following statements correctly describes the transfer of energy that **initially** enters this system? A. The sea urchin gets energy from the sea otter. B. The shark receives most of the energy that enters the ecosystem. C. The crab transfers less energy to the next trophic level than does the rockfish. D. The kelp converts energy into a form that can be used by other organisms.

4. The diagram below represents a food web. Which of the following are consumers in this ecosystem? A. apples B. clover C. mice D. nuts

5. In which of the following ways do most plants obtain the nitrogen they need? A. They break down the proteins in dead animals. B. They absorb nitrogenous compounds from the soil. C. They take nitrogen gas directly from the atmosphere. D. They produce nitrogenous compounds in photosynthesis.

6. During the growing season, 5000 square meters of corn plants transpires approximately 1.85 million liters of water. The water lost from the plants via transpiration goes directly to which of the following? A. Insects B. The soil C. Streams D. The atmosphere

7. Black terns are a species of bird living in marshes, ponds, and marshy lakes. They feed on insects, fish, and crustaceans. They usually make their nests on loose, floating vegetation. Which of the following environmental changes would **most likely** decrease the size of the black tern population? A. A competing bird population decreases in size. B. Fish species have a more successful breeding season than usual. C. A new plant species invades the environment and creates a dense cover of vegetation. D. Insect larvae experience lower than average rates of predation and survive to adulthood.

8. Carbon moves through the environment via the carbon cycle. Some carbon exists as carbon dioxide in the atmosphere. Scientists believe that increased amounts of atmospheric carbon dioxide significantly contribute to the greenhouse effect and global warming. a. Identify two carbon cycle processes that add carbon dioxide to the atmosphere. b. Identify one carbon cycle process that removes carbon dioxide from the atmosphere. c. Describe one action that humans could take to reduce levels of carbon dioxide in the atmosphere. Explain how the action would reduce carbon dioxide levels.

9. Which of the following processes releases primarily oxygen into the atmosphere? A. combustion B. osmosis C. photosynthesis D. respiration

10. A food web is shown below. Which of the following is most likely to lead to an **increase** in the number of foxes over time? A. a decrease in owls B. an increase in hawks C. an increase in mountain lions D. a decrease in raspberry bushes

11. The diagram below shows part of the carbon cycle. If many trees are removed from a forest by logging, what is the most immediate effect on the carbon cycle in that forest? A. increased rates of decomposition B. decreased use of atmospheric CO2 C. decreased combustion of fossil fuels D. increased production of organic compounds

12. Populations of Caribbean coral have decreased significantly over the past 30 years due to disease. Which of the following is most likely a major factor leading to the increased amount of disease in the coral? A. Symbiotic algae are living in the coral cells B. Several different species of fish live on the coral reefs C. Levels of spawning have decreased and lowered reproductive rates. D. Water temperatures have increased and favored the growth of microorganisms.

13. The diagram below shows a food web for an ecosystem. a. Identify the producers and the consumers in this food web. b. In this ecosystem, is more energy available to the field mouse population from eating spiders or from eating oats? Explain your answer.

14. A partial food web for a coastal ecosystem is shown below. Which of the following organisms in this food web obtains energy from both producers and consumers? A. anchovy B. mysid shrimp C. weakfish D. sand shrimp

15. Which of the following environmental conditions makes water **less** available to plants for growth? A. Soil in the area is organically rich B. Ground cover is effective at slowing erosion C. High humidity lowers the rates of transpiration D. Cold temperatures freeze the water in and on the ground

16. There is a limit to how large any given population can grow. Which of the following statements **best** explains why a population must eventually stop growing? A. A low female-to-male ratio develops in the population as it grows. B. Old individuals outnumber juveniles in the population as it grows. C. The resources available are fully used by the population as it grows. D. Natural selection changes the gene pool of the population as it grows.

17. On remote islands, immigration and emigration usually do not have a large effect on population sizes. A bird population on a remote island remains at a relatively constant size year after year. Which of the following **most likely** describes the birth rate and death rate for this population? A. Birthrate and death rate are both zero. B. Birth rate and death rate are close to equal. C. Birth rate is significantly less than death rate. D. Birth rate is significantly greater than death rate.

18. The diagrams below show a marine food web and an incomplete terrestrial food web. The organism in the terrestrial food web that corresponds to the krill in the marine food web is labeled X. Which of the following organisms is **most likely** organism X? A. B. C. D.

19. A hurricane sweeps across a small Caribbean island, killing 50% of the herbivore species on the island. Which of the following is the most immediate result? A. a reduction in biodiversity B. an acceleration of the carbon cycle C. an increase in predator populations D. a decline in decomposer populations

20. A graph of atmospheric carbon dioxide concentration over time is shown below. Scientists are investigating the cause of the large increase in atmospheric carbon dioxide concentration since about 1800. Which of the following provides the best explanation for the increase? A. eruptions of large volcanoes B. use of fossil fuels by humans C. natural fluctuations of climate D. photosynthesis by phytoplankton

21. The water cycle would NOT occur if which of the following were missing? A. animals B. bacteria C. ice caps D. solar energy

22. Part of a tundra food web is shown below. Which of the following describes the relationship between the sedge and the arctic hare? A. competition B. host-parasite C. mutualism D. producer-consumer

23. Which of the following explains why legume plants are less likely than other terrestrial plants to experience nitrogen limitation? A. Legume plants need less nitrogen than other plants do. B. Legume plants have nitrogen-fixing bacteria on their roots. C. Legume plants catch insects to supply themselves with nitrogen. D. Legume plans can absorb nitrogen directly from the atmosphere.

Questions 24-26 A partial food web for organisms in Yellowstone National Park is shown below.

24. Which of the following organisms is a secondary consumer in this food web? A. yellow-bellied marmot B. strawberry plant C. least chipmunk D. king bolete

25. Which of the following releases oxygen into this food web ecosystem? A. elk respiration B. Idaho fescue photosynthesis C. sweet cicely root decomposition D. migratory grasshopper reproduction

26. Assume the elk population in Yellowstone National Park increases. Discuss how this increase in elk will most likely affect each of the following populations: Be sure to include specific reasons to support each of your responses.
 * Idaho fescue
 * Migratory grasshopper
 * Grizzly bear

27. Which of the following lists identifies organisms that are producers in food webs? A. Algae, ferns, sunflowers B. Mushrooms, bacteria, earthworms C. Termites, red foxes, shrews D. Woodpeckers, cardinals, grasshoppers

28. Which of the following lemurs would be classified as a secondary consumer? A. A mouse lemur eating insects B. A Verreaux's sifaka eating leaves C. A ring-tailed lemur eating fruits D. A red-bellied lemur eating flowers

29. A builder is proposing a new housing development in an area of western Massachusetts. Construction of the housing development will destroy wetland habitat in the area. Which of the following would be the **most likely** consequence of the wetland's destruction? A. The wetland plant species would disperse to adjacent meadow habitats. B. The populations of wetland animals would be unable to survive in that area. C. The wetland animal species would survive by interbreeding with non-wetland animal species. D. The populations of wetland plants would evolve to disperse seeds by wind rather than by water.

30. Which of the following relationships is an example of mutualism? A. A lion eats a gazelle. B. A viruses uses both a bird and a horse as hosts. C. A bacterium breaks down dead plant materials. D. A bird eats food particles from a crocodile's teeth.

31. The graph below shows changes in the birth rate and death rate for a large population of deer over a 20-year study period. a. Describe and explain **two** factors that can affect the birth rate in the deer population. b. Describe and explain **two** factors that can affect the death rate in the deer population. c. Identify **one** time period on the graph during which the deer population was increasing. Explain your answer.

32. Which of the following human activities reduces biodiversity? A. Prohibiting hunting in wildlife preserves B. Taking tissue samples from members of endangered species C. Planting only native grass species to prevent erosion beside highways D. Planting only red pine trees to replace native hardwood forests cut for lumber

33. The graph below shows the levels of acidity that different kinds of freshwater fish can tolerate. Low pH values mean the water is more acidic. Based on the data, which of the following fish would most likely experience the largest population declines due to acid rain pollution? A. brown trout B. smallmouth bass C. fathead minnow D. yellow perch

34. In July, a student tested the soil in two plots and calculated the concentration of nitrogen compounds present in each plot. The student then planted 20 seedlings in the first plot and allowed them to grow. Nothing was planted in the second plot. The student tested the soil in both plots again after one month. The concentration of nitrogen compounds had decreased in the first plot but had remained the same in the second plot. Which of the following **best** explains the decrease in nitrogen compounds in the first plot? A. The nitrogen compounds had broken down into elements. B. The nitrogen compounds were absorbed by the seedlings for growth. C. The nitrogen compounds escaped through air pockets created by the seedlings' roots. D. The nitrogen compounds had evaporated because of warm summer temperatures.

35. Leaves fall from deciduous trees in autumn. The carbon in these leaves is returned to the atmosphere through which of the following processes? A. condensation B. decomposition C. photosynthesis D. transpiration

36. A marine food web is shown below. Which of the following diagrams correctly represents an energy pyramid from this web? A. B. C. D.

37. A student takes the following notes about an ecosystem. a. Use these notes to construct a food web for this ecosystem. b. In your food web, identify one organism **each** at the following trophic levels: Producer, primary consumer, secondary consumer, higher-order consumer.

38. Air samples taken in Canada since 1986 show that atmospheric carbon dioxide concentration is higher on average in winter than in summer. Which of the following statements best explains the difference in carbon dioxide concentrations? A. The rate of decomposition is slower in winter than in summer. B. The greenhouse effect is more pronounced in winter than in summer. C. The number of animals that are active is less in winter than in summer. D. The amount of photosynthesis by plants is lower in winter than in summer.

39. The table below shows data on reproduction for mouse populations at various population densities.
 * **Average number of Mice per Cubic Meter** || **Average Percent of Pregnant Females** || **Average Number of Mice Per Litter** ||
 * 34 || 58.3 || 6.2 ||
 * 118 || 49.4 || 5.7 ||
 * 350 || 51.0 || 5.6 ||
 * 1600 || 43.3 || 5.1 ||

Based on the data, which of the following statements **best** describes an effect of population density on mouse populations? A. High population density increases the birthrate. B. High population density decreases the birthrate. C. High population density increases the male to female ratio. D. High population density increases the number of successful matings.

40. When spring and summer conditions are warm and rainy, mosquito populations often become quite large. Which of the following statements **best** helps to explain this relationship? A. Mosquito larvae eat organic debris. B. Adult male mosquitoes feed on plant nectar. C. Mosquitoes are attracted to warm-blooded animals. D. Female mosquitoes lay their eggs in pools of water.

41. A student set up a terrarium, watered the soil, and covered the terrarium tightly with a lid. The next day, the student observed water droplets on the inside of the lid. The droplets provide evidence that which of the following steps of the water cycle had occurred in the terrarium? A. runoff and evaporation B. precipitation and runoff C. evaporation and condensation D. condensation and precipitation

42. Some species of penguins, such as chinstrap penguins, depend on open water for their survival. Other species of penguins, such as Adelie penguins, depend on ice. Over the last 20 years, the population size of chinstrap penguins has increased and the population size of Adelie penguins has decreased. Which of the following **most likely** caused these changes in population size? A. an increase in landmass and shorelines B. an increase in global air and water temperatures C. a decrease in the number of leopard seal predators D. a decrease in the length of time before chicks take to sea

43.

1. A 2. A 3. D 4. C 5. C 6. D 7. C 8. Sample responses found at: 9. C 10. A 11. B 12. D 13. Sample responses found at: [] 14. D 15. D 16. C 17. B 18. A 19. A 20. B 21. D 22. D 23. B 24. C 25. B 26. Sample responses found at: [] 27. A 28. A 29. B 30. D 31. Sample responses found at: [] 32. D 33. D 34. B 35. B 36. C 37. Sample student responses found at: [] 38. D 39. B 40. D 41. C 42. B
 * Answers**