Science 10 Practice test (Ch 1-2 Review)Name:______

Sustainability of Ecosystems

Part A Circle the letter of the correct response. (12 points)

  1. Which of the following would you expect to have the least biomass within their trophic level?

a. a population of miceb. a population of foxes

c. a population of grassesd. a population of rabbits

  1. How many trophic levels are shown in the food chain on the right?

a. 7b. 6

c.5d. 4

  1. What is missing from the food chain on the right?

a. producers

b. herbivores

c. carnivores

d. detritivores

  1. In this ocean ecosystem, which of the following is most likely?

a. a typical pyramid of numbers

b. an inverted pyramid of numbers

c. a typical pyramid of biomass

d. an inverted pyramid of biomass

  1. Which of the following is not a factor that determines carrying capacity of an organism?

a. a limited amount of nutrients and energy

b. the trophic level of the organism

c. the number of consumers in the next (higher) trophic level

d. the density or number of organisms in a limited space

  1. Which of the following is an example of interspecies competition?

a. Male wolves compete for territory.

b. Owls and hawks both eat small rodents.

c. Sea otters affect many different food chains within the ecosystem.

d. A forest fire can greatly reduce the population of spruce beetles.

  1. Which of the following is an example of a keystone species?

a. Male wolves compete for territory.

b. Owls and hawks both eat small rodents.

c. Sea otters affect many different food chains within the ecosystem.

d. A forest fire can greatly reduce the population of spruce beetles.

  1. The productivity of an ecosystem depends on:

a. temperature, moisture and soil nutrients

b. the number of top consumers

c. the type of producers

d. only the nutrients available in the soil

  1. Which of the following is NOT a factor that has increased the population of humans on Earth?

a. medical knowledge and health care

b. overcrowding in cities

c. agriculture (increased food supply)

d. sanitation (the invention of sewer systems)

  1. In Biosphere II, what are scientists trying to learn?

a. a better understanding of food webs pyramid of numbers

b. a better understanding of pyramids of biomass

c. a better understanding of competition

d. a better understanding of nutrient cycles

  1. Carbohydrates are made up of the elements

a. carbon, nitrogen, and oxygen

b. carbon, hydrogen, and nitrogen

c. carbon dioxide, and hydrogen

d. carbon, hydrogen, oxygen

  1. Which of these ecosystems has the greatest effect on the carbon cycle?

a. oceansb. boreal forests

c. grasslandsd. deserts

  1. Which of the following processes adds oxygen to the atmosphere?

a. cellular respirationb. decomposition

c. denitrificationd. photosynthesis

  1. Which of the following is a reactant of photosynthesis?

a. oxygenb. carbohydrates

c. nitratesd. carbon dioxide

  1. Which of the following processes are all involved in the carbon cycle?

a. Photosynthesis, fixation, decomposition

b. Photosynthesis, cellular respiration, decomposition

c. Cellular respiration, decomposition, fixation

d. Cellular respiration, fixation, photosynthesis

  1. Which of the following processes in NOT involved in the nitrogen cycle?

a. fixation

b. denitrification

c. nitrification

d. photosynthesis

  1. Which of the following lives in the root nodules of legume plants?

a. nitrifying bacteriab. denitrifying bacteria

c. decomposersd. nitrogen fixing bacteria

  1. Which of the following is given off by decomposers?

a. ammoniab. nitrates

c. nitrogend. oxygen

  1. Which of these conditions does NOT reduce biodiversity?

a. extreme weather conditions (cold/hot, wet/dry)

b. high levels of nutrients

c. high productivity

d. acidic environments

PartB Fill in the blanks (9 points)

  1. Match the term on the left with the corresponding definition or description (write the letter in the space provided).

  1. Nutrients
/ _C_a system where no matter enters or leaves
  1. nutrient cycles
/ _G_nutrients used in growth and life processes
  1. closed system
/ _ A chemical elements needed by living things
  1. biotic
/ _ H_ the dry mass of living things
  1. abiotic
/ _F_nutrients that enter a living thing
  1. input
/ _B_the movement of nutrients through an environment in a loop
  1. throughput
/ _E_NON-living parts of an ecosystem
  1. biomass
/ _D_living parts of an ecosystem
  1. output
/ _I_waste and unused nutrients are returned to the ecosystem
  1. Match the conversion on the left with the corresponding process on the right (write the letter in the space provided). (3 points)

C Ammonia (from waste) to nitratesA. Nitrogen fixation

B Nitrates (in soil) to nitrogen gasB. Denitrification

A Nitrogen gas to nitratesC. Nitrification

Part C Answer each question in full sentences

  1. Is it a more efficient use of land for people to eat beef or beans for protein?Explain why. (2points)

It’s more efficient to grow beans. On a limited amount of land, producers (first trophic level) will provide more energy than consumers.(The cattle lose energy through their life processes)

  1. Explain the difference between a pyramid of numbers and a pyramid of biomass.

A pyramid of numbers shows the number of organisms at each trophic level in an ecosystem. It is useful for understanding population sizes. A pyramid of biomass only shows the mass of organisms at each level.

  1. Describe one difference between the scientific and traditional management of resources, such as sea otters or another species in their ecosystem. (2points)

In scientific management, the population sizes are controlled by understanding their needs and their role in the ecosystem. In traditional management, populations are controlled by hunting and use of the organism by people.

Explain why it is more difficult to control pests in monoculture than in a natural ecosystem.

In monoculture, large areas of the same crop are planted. This provides a large food supply for pests and few natural predators to eat them. In nature, the plants that are eaten by the pests are spread out, so they must work harder to find them and avoid predators at the same time.

  1. Give two examples of human activities that reduce the productivity of natural ecosystems. (2 points)

The productivity is reduced by any activity that reduces plant growth. Some examples areburning forests, draining wetlands, paving areas for roads, building golf courses and damming rivers.

  1. Explain two reasons why productive ecosystems like tropical forests cannot always be used as productive farmland. (2points)

The surrounding forest might infect the crops with diseases or pests, and changes might reduce the fertility of the soil (by removing the forest litter which provides nutrients and prevents soil from washing away).

  1. Why does energy pass through ecosystems in a flow instead of a cycle like nutrients do?

Energy at each trophic level is converted to heat or lost in the life processes. Nutrients, on the other hand, can be recycled and reused.

  1. Write the chemical equation for photosynthesis.

6 CO2 + 6 H2O + energy → C6H12O6 + 6O2

  1. Explain why we describe cellular respiration as “burning” calories”.

The reaction (it’s the reverse of the photosynthesis reaction) has the same form as a combustion reaction.

  1. Describe two ways that carbon is stored for long periods of time (on land or oceans). (2 points)

Carbon on land may be stored as deposits of plant or animal material (large deposits can form coal or oil over time). In the ocean, the shells of sea animals settle to the bottom and form sediments.

  1. Describe two human activities that increase the level of carbon dioxide in the atmosphere. (2 points)

Human activities that burn fossil fuels (coal and oil) release large amounts of carbon dioxide. Removing plant material (such as damaging or cutting down forests), prevents CO2 from being removed by photosynthesis in the atmosphere.

  1. Describe two human activities that increase the level of nitrogen in ecosystems. (2 points)

Agriculture that uses chemical fertilizer produces large amounts of nitrogen that gets into waterways. Human activities that burn fossil fuels also create nitrogen compounds that form acid rain.

  1. What human health problem is related to nitrates in drinking water? (2 points)

Nitrates in drinking water prevent proper iron absorbtion and make it hard for the body to carry oxygen properly. (Blue Baby syndrome)

  1. Explain how acid precipitation is formed. (2 points)

Acid precipitation is formed during combustion, when nitrogen and oxygen in air are heated together. The resulting compounds form nitric acid when they contact water in the atmosphere.

  1. Explain how lakes become acidified and what happens as a result. (2 points)

Lakes become acidified when acid rain is frequent. The resultis the death of almost everything living in the lake.

  1. Summarize the stages of eutrophication. (5 points)
  1. Nitrates get into surface water (fertilizer or sewage)
  2. Algae begins to grow, blocking sunlight to lower layers
  3. Plants below the surface die, so less oxygen is present
  4. Decomposers break down the dead plants, using even more oxygen
  5. Organisms that need oxygen begin to die
  1. Which nutrient cycle(carbon or nitrogen) depends most on bacteria? Explain your answer. (2 points)

The carbon cycle only relies partly on decomposers to return carbon to the atmosphere. The nitrogen cycle, however, relies almost entirely on bacteria to remove nitrogen from air (fixation)and to return it to the atmosphere(denitrification).

  1. Describe two ways that some human activities are unsustainable. (1point)

Unsustainable activities are those that:

  • remove nonrenewable resources (which nature can’t replace) such as mining,
  • remove renewable resources faster than nature can replace them, such as clearcutting all the trees in a forest,
  • or damage the environment so that it can no longer provide a resource, such as polluting groundwater and contaminating wells