SNC1D1
Biology Test Review Answer Key
2. water
3. A food web contains many interconnected food chains. They both show the
transfer of energy (feeding relationship) in an ecosystem.
4. (a) grass grasshopper  snapping turtles

(b) grass  grasshopper  snapping turtles  bacteria
(c) SUN
grass  grasshopper  snapping turtles  bacteria
5. nitrifying – convert ammonia into nitrites, and then into nitrates
denitrifying – convert nitrates in soil back into nitrogen gas
nitrogen-fixing – convert nitrogen gas into ammonia
6. mutualism – both species benefit from the relationship, e.g. clownfish and
anemone
commensalism – one species benefits and the other is not affected, e.g. remora shark
hitching a ride on the bigger shark (and feeding off the scraps of food)
parasitism – one species harms the other species (the parasite lives on or in the host
and benefits), e.g lice feeding off your scalp
8. habitat change, climate change, invasive species, pollution, overexploitation
14. modern pesticides are water-soluble and dissolve, thus the organism can excrete
them in their waste (they do not accumulate in organisms) – they also break down
quickly in the environment
20. if all decomposers were removed, the dead material and waste would build up
and the nutrients would never be returned to the soil
21. (a) bacteria are important as decomposers, therefore not all harm humans,
animals and plants – some are crucial to the nutrient cycles
(b)Some bacteria are responsible for many diseases. However, some are important
to all living things and the environment. We must not eradicate all bacteria on the
planet.
22. (a) A
(b) B – not enough energy in the producers level to support the large number of
consumers above it
C – less energy in the producers than in the primary consumers
23. (a) 1995 – 2000
(b)8000
(c) limiting factors like predators, amount of food and water
(d) a decrease in the amount of predators, immigration of minks
24. (a) overexploitation, habitat change
(b) pollution, climate change
(c) overexploitation
28. the pollutants accumulate in organisms because many of these are fat-soluble –
the concentration of these pollutants increase as you move up the food chain
32. positive – dandelion would not steal the nutrients from the other plants in the
yard.
Negative – risk of bioaccumulation and harming other organisms
You could use an appropriate tool to pull out the weeds or use modern, safer
pesticides
33. (a) Test tube A and C had water from the fish tank without a plant (A was in a
dark, cool place; C was in a sunny location)
-want to determine the initial concentration of carbonic acid in the water before a
plant is added to it
(b)
-Test tube A: will still be yellow
-Test tube B: will still be yellow
-Test tube C: will still be yellow
-Test tube D: will be red
(c) –Test tube A: no plant to use up the carbon dioxide (in the process of
photosynthesis)
-Test tube B: the plant is in the dark so it cannot perform photosynthesis (cannot
use up the carbon dioxide)
-Test tube C: no plant to use up the carbon dioxide
-Test tube D: the plant is using up the carbon dioxide (photosynthesis); therefore
without carbonic acid, the phenol red will turn red
(d) the initial colours will be red, since there is no dissolved carbon dioxide in the
tap water (no living things in it to produce carbon dioxide, through respiration)
A: final colour will be red
B: final colour will be red
C: final colour will be red
D: final colour will be yellow
34. grass (?)  crickets  pitcher plant  herbivorous mammals
35. (a) producers 520,000 kJ/m2
(b) 520 kJ/m2
37. the quick growth from 1955 – 1965 can be due to a decreased number of
predators; the near vertical line in 1965 can be due to a natural disaster (flood, fire)
38. from 1945 – 1955, the deer is growing normally because a healthy wolf
population; when the wolf population decreases to about 50 in 1960, there is an
explosive growth of deer; the wolf population (0) in 1970 could also be explained by
a natural disaster on the island; the carrying capacity for the wolf is approximately
100 from the data shown, whereas due to nature of the graph showing the caribou
population, the carrying capacity for the caribou population can not be inferred
41. (a) ecology is the study of how living things interact with other living things and
with the non-living things in the environment
(b) system is a set of things working together as part of a mechanism
(c) matter goes from the algae to the algae-eating fish to the trout; when these die
decomposers break the waste down and return matter to the soil
energy flows in the direction from the algae to the trout (once it is used, it cannot be
reused; the sun must replenish this energy)
(d) there would be an increase in the trout but a decrease in the algae; after some
time, this would result in a decrease in the algae-eating fish, which will restore the
trout population and the whole system will reach equilibrium again
42. sustainability is the ability of populations of organisms to continue to interact
and reproduce indefinitely
biodiversity is the number of different types of organisms
-if biodiversity decreases, this will affect other populations of organisms negatively
causing a decrease in rate of reproduction
43. habitat change, climate change, overexploitation, invasive species, pollution