Ecology

2. Students’ answers may vary but could include water availability, temperature, space for home, or inclement weather.

3. A food chain shows the flow of energy through a single feeding path in an ecosystem. A food web is made up of many interconnected food chains.

4. (a) grass => grasshoppers => frogs => snapping turtles

(b) grass => grasshoppers => frogs => snapping turtles

bacteria

(c) Sun => grass => grasshoppers => frogs => snapping turtles

5. Bacteria involved in the nitrogen cycle include: nitrogen-fixing bacteria that convert atmospheric nitrogen gas into ammonia; nitrifying bacteria that convert ammonia into nitrates; denitrifying bacteria that convert nitrates back into nitrogen gas; decomposing bacteria that break down the tissues of dead or decaying organisms and release nitrogen compounds into the ecosystem.

6. Three types of symbiosis include: commensalism, where one organism benefits from another’s actions and the second organism neither benefits nor is harmed, such as a bird building a nest on a tree; mutualism, where both organisms benefit from interacting with one another, such as leaf-cutter ants and fungus; parasitism, where one organism benefits at the expense of another, such as ticks living on mammals.

7. Genetic diversity is a specific type of biodiversity that focusses on the differences among individuals of the same species.

8. Five major factors that affect biodiversity include habitat change, overexploitation, pollution, invasive species, and climate change.

9. Elements that make up the soil include litter, topsoil, humus, organic matter, rock particles, subsoil, and bedrock.

10. Most gardeners would prefer loam soil. It has lots of humus, which provides nutrients for plant growth; air pockets to allow water to drain but still support plant growth; air pockets that hold air for important bacteria to grow and assist with cycling of nutrients.

11. pH measures the acidity of substances including soil.

12. Students’ answers may vary but could include crop rotation, use of manure, or addition of fertilizers.

13. No. Dissolved oxygen measures the amount of oxygen present in water. Biological oxygen demand measures the rate at which oxygen is used up by the micro-organisms in a given body of water.

14. Modern pesticides are designed to last one growing season and then break down into less harmful substances.

15. Special concern, threatened, endangered, extirpated, and extinct.

16. Practising soil conservation and reducing farming practices that remove or damage the topsoil can reduce soil erosion.

17. Students’ answer may vary but could include by-laws that prevent the movement of materials that may carry invasive species, or laws against bringing foreign food, produce, and animals into the country.

18. The Convention on Biological Diversity

19. A community describes several interacting populations. The biosphere is defined as the area on the planet where all life exists. Since this involves all the biotic components interacting with abiotic factors, ecosystem would be a better description than community.

20. Energy and nutrients would be trapped in the tissues of all the organisms that ever existed in the ecosystem. There would likely be a shortage of nutrients and energy available for the environment.

21. (a) This statement is too wide-sweeping. Bacteria play critical roles in all the nutrient cycles and, without them, life on the planet would not be possible.

(b) Students’ answers may vary but could include the following: Certain bacteria are bad for your health and are responsible for many diseases that hurt humans, animals, and plants. However, not all bacteria are harmful.

22. (a) Pyramid A best represents a sustainable ecosystem.

(b) Pyramid B does not follow the 10 percent rule as you move up the feeding levels. Not enough energy is available to support the top two feeding levels. Pyramid C does not make sense, as the bottom level has to have the most energy.

(c) Assuming that scenario B survives past the next couple of generations, it would likely look like Pyramid A in 10 years’ time. The second level would outstrip the energy in the bottom level and eventually most of these animals would die out. However, the producers would likely recover and a sustainable number of consumers would follow.

23. (a) From 1990 to 1997, the mink population is growing the fastest.

(b) Students’ answers may vary but should be close to 8000.

(c) Limiting factors would prevent the mink population from going higher than the ecosystem could support.

(d) Students’ answers may vary but could include human intervention. Humans may have enacted conservation measures, stopped hunting, or controlled the level of mink predation.

24. (a) Habitat change

(b) Climate change

(c) Overexploitation

25. (a) The photograph shows clearcutting of a forest.

(b) Students’ answers may vary but could include changes to the habitat by removing the ecosystems many organisms live and function in; change in climate, as less water is released into the atmosphere through the transpiration and the water cycle; change in climate with the release of carbon dioxide into the atmosphere through combustion of wood; pollution, as debris from the forest industry is released into the environment.

26. No, clear water does not necessarily indicate safe drinking water. Students’ answers may vary but could include indicators that can be used to determine whether water is safe to drink, such as biological, heavy metals, pH, pesticides and presence of other chemicals.

27. The most likely cause is runoff of fertilizer from farms that has entered the lake, causing eutrophication.

28. Many pollutants bioaccumulate in the tissues of animals. The pollutants biomagnify through the food chain and eventually collect in very high concentrations in top consumers, where negative effects can be observed.

29. Students’ answers may vary but could include a plan that outlines how to increase and protect current populations of black-footed ferrets and protect their habitat. Also, designing some method to control the spread of plague by the fleas would be important.

30. (a) Suggest that they only buy wood from suppliers that support sustainably managed forests and that they can determine this by looking for the Forest Stewardship council’s tree check logo.

(b) Students’ answers may vary but could include how important it is to practise sustainable actions. These actions will encourage more businesses to reduce their footprints, knowing that customers value these practices.

31. Students’ answers may vary but could include the following categories in their reports: review of student transport to school, restoration of open spaces, control of water drainage and flow during rainfall, convert roof to green roof, landscaping, reduce use of energy use in school, recycling programs, use low-emitting materials that do not emit toxins, place windows in locations to increase natural light.

32. Students’ answers may vary but could include positive consequences: improved aesthetics and appeal, reduced chance of allergies; negative consequences: increased chance of poisoning of children and pets, runoff carrying pesticides that may enter local ecosystems and bioaccumulate. It is a poor choice for the homeowner to use pesticides. The risk is not worth the reward of having a nice looking lawn. Possible alternatives include spreading grass seed, aerating the lawn, manually pulling weeds, spreading mulch, matching plants to the conditions of the property, and watering the lawn effectively.

33. (a) The purpose of A and C is to act as experimental controls.

(b) A, B, and C will all be yellow. D will turn red.

(c) The plant in D will undergo photosynthesis in the sunny location. The plant will remove carbon ioxide from the water and the pH level will go higher. Phenol red turns yellow only under acidic conditions.

(d) Aquarium water has higher levels of carbon dioxide than tap water due to the animals respiring in the water. The tap water will initially turn red, and it will be impossible to tell which plants in the test tubes have undergone photosynthesis.

35.(a) Assuming the 10 percent rule, the producers contain 52 000 kJ/m2.

(b) 520 kJ/m2.

36. (a) Students’ answers may vary but should include a graph that shows exponential growth until carrying capacity is reached.

(b) Initially, the population of the invasive species would grow slowly. Without natural predators to  control the invasive species population, they would very quickly increase in population. They would eventually reach the carrying capacity of the ecosystem once the limiting factors became diminished.

37. The caribou had a seemingly unlimited supply of food for many generations. Eventually, the food supply was no longer able to support the population of caribou and their population crashed.

38. There were not enough caribou to support the original population of wolves, and they began to die off until the ecosystem reached a carrying capacity able to support a specific population of wolves.

39. Students’ answers may vary but could include pollutants such as heavy metals, plastics, emissions of nitrogen and sulfur, and the pollutants’ effects on terrestrial and aquatic ecosystems.

40. (a) The number of wild fish caught is steadily decreasing, while the number of aquaculture fish harvested is increasing.

(b) Students’ answer will vary depending on the type of analysis they do. If they use a linear approximation, the groundfish values will be close to 35 000 for 2002 and 0 for 2004. Likewise, the aquaculture values will be close to 128 000 for 2002 and 143 000 for 2004. If they draw a curve to extrapolate the data, the groundfish values will be close to 200 000 for 2002 and 190 000 for 2004. Likewise, the aquaculture values will be close to 165 000 for 2002 and 214 000 for 2004.

(c) The groundfish are a resource that is being overexploited to meet the needs of growing populations. The capture of the fish is not a sustainable practice.

(d) Eventually, the needs will be met, but unless there is a dramatic increase in harvesting, the needs will not be met for a few years.

(f) The new data show that the total for groundfish caught is now increasing while the aquaculture harvest is decreasing.

(g) Ecosystems have many variables that will affect the populations of species, and this makes it very difficult to make predictions about changes that will occur.

41. (a) Ecology is the study of ecosystems.

(b) A system is a group of individual components that interact as a whole to accomplish a task.

(c) Energy originates from the Sun and the algae convert it into a form that can be used by other  organisms in the ecosystem. The energy flows one way through the food chain. At each feeding level, only about 10 percent of the energy is transferred. Matter cycles through the organisms of the ecosystem, moving from the algae through the consumers, and eventually from the consumers back to the producers. Movement of matter is cyclical.

(d) Students’ answers may vary but could include an increase in the numbers of trout since the trout have a greater food supply. Or, the algae eaters may increase too much and decrease the overall amount of algae, which in turn will cause the numbers of algae eaters to decrease.

42. Biodiversity is defined by the biological diversity that is apparent in a certain region. Sustainable actions will ensure that the environment is able to maintain biodiversity. Unsustainable actions will threaten the levels of biodiversity by removing resources or compromising the habitats of organisms living within the ecosystems.

43. The main factors that increase loss of biodiversity are habitat change, climate change, overexploitation, pollution, and invasive species.

44. Soils form the medium that covers the top of the lithosphere. Soils support the growth of terrestrial plants since nutrients from matter cycling reside here. Students’ answers may vary but could include increasing the acidity of soil and soil erosion from agricultural practices of farmers, deforestation, mining, and development.

45. Students’ answers may vary but could include tests for indicators such as the presence of aquatic organisms, levels of dissolved oxygen, biological oxygen demand, pH, presence of heavy metals or pesticides, and various nutrient levels.

46. Environmental problems do not stop at international borders. Fixing them requires the  participation of all countries involved, so that the actions of citizens, industry, or government in one region do not undo the actions of those in another. In 1997, the United States and Canadian governments signed an agreement to restore the Great Lakes. The Ontario and state governments created management plans to clean up each of the Great Lakes. Also, in 2007, the Ontario government passed the Endangered Species Act, prohibiting the killing, capturing, possessing, selling, or trading species that are endangered in Ontario. The law also protects the species’ habitats.

47. Students’ answers may vary but could include references to stewardship and conservation activities.

48. Students’ short reports may vary but could include references to fertilizer runoff associated with agriculture and residential activities. They may also refer to activities that contribute to the five human impacts studied at the beginning of Chapter 2:

• habitat change

• overexploitation

• pollution

• introduction of invasive species

• climate change

49. Students’ answers may vary depending on the organization they choose to write about but should include environmental issues tackled, solutions to problems, and additional steps to take.

50. Students’ answers may vary but could include references to raising awareness of or doing sustainable actions that conserve ecosystems and biodiversity, such as reducing emissions, conserving energy, planting appropriate plants for our climate conditions, supporting local farms and industries by purchasing their goods, or volunteering for organizations that support and protect the environment.

51. Students’ answers may vary but could include: the use of shopping bags; choice of what products or foods to purchase; reduce, reuse, recycle; type of transportation most often used; energy conservation; awareness of waste disposal and diversion; how the demand for certain foods may lead to overexploitation of natural resources; where and how development impacts surrounding ecosystems; more respect for the types of plants and animals they use.