Unit D Review Questions
1. The following table compares the processes of primary and secondary succession.
Description
Primary Succession
Secondary Succession
relative speed of
process
slower
faster
starting conditions
no soil present
soil present
events causing
process to begin
new volcanic islands from lava flow
hardening, glaciers receding
clearcut logging, forest
fires, tilling of soil
resulting community
climax community
climax community
2. a.
b.
c.
d.
e.
f.
g.
h.
population
J-curve
doubling time
open population
exponential growth
carrying capacity
closed population
S-curve
3. Note the following adaptations table. Other examples are possible.
Type of
Adaptation
How It Makes
Organism More Successful
Example of
Organism with Adaptation
speed
easier to catch prey and escape predators
cheetah or pronghorn
camouflage
makes it more difficult to see
organism and, therefore,
harder to find
walking stick insect or flounder
bright colours
attractive to mates
peacocks or parrotfish
sharp spines
undesirable to eat
cactus or porcupine
produces poison
undesirable to eat
poison arrow frog or
rhubarb leaves
thick fur or hair
warmth in winter
polar bear or deer
horns or antlers
protection or to fight for mates
moose or deer
4. Note the following contributions to the field of biology.
Researcher
Scientific Contribution
Malthus
Malthus hypothesized that populations grow exponentially but resource
production does not—this causes war and famine. He provided an analysis and
awareness of how human population change is affected.
Lamarck
Lamack proposed a theory of evolution that was unable to be proved, but he
caused people to think about how organisms might have changed over time.
Darwin
5. a.
b.
c.
Darwin proposed a theory of evolution by natural selection that is supported by
many pieces of evidence. His controversial theory went against the common
belief of the time that organisms were fixed in their current form and were
unchanged since Earth was created.
theory of natural selection
theory of evolution
selective breeding
d.
e.
f.
g.
asexual reproduction
fitness
mutation
gene
6. Student sketches of the strip mine should be similar to this one if they lived in a boreal
forest. If they lived in the grasslands, trees would not be found at the centre nor at the
edges.
a.
In the centre, students should
expect to find trees.
b.
Students should find lichens,
mosses, and ferns at the outer edges
of the mine.
c.
Trees would be found in the
surrounding area that was not
moved.
7. The predators kept the elk population at a sustainable level (carrying capacity).
8. The elk population grew exponentially after 1925.
9. The elk may have overeaten their food source, causing mass starvation. Overcrowding may
have caused disease to spread and reduce the population.
10. It appears that the biologists re-introduced a predator or began culling the herd to keep
numbers at a more manageable level.
11. Note the following camel adaptations.
Adaptation
two sets of long eyelashes
wide, padded feet
nostrils that can open and close
Reasons for Advantage
The long eyelashes help keep both bright sunlight and
blowing sand out of the eyes.
The padded feet help keep the camel from sinking in
the sand as it walks.
Closed nostrils prevent sand from blowing up the nose
during dust storms.
a hump located on its back that is The fat can be broken down to create water during dry
a reservoir for fat
times.
thick, tan-coloured fur
a tough mouth and strong teeth
This helps the camel blend into its surroundings. A light
colour reflects the heat.
A tough mouth is needed for eating sharp and spiny
(cacti) desert plants.
12. Since these colonizing plants grow in open meadows, they would be very accessible to
grazing herbivores. Defence mechanisms allow them to grow well in the open, yet not be
overeaten.
13. Some of the concerns over shipping water to cities in the United States could include the
following:

There might not be enough water left for Alberta’s own growing population.

The cost of water for Albertans will increase.

Once the pipeline is opened, can it ever be closed without huge repercussions in
trade with the United States?

More water to those thirsty cities means more growth in those cities and an increase
in the demand for water.
14. Abiotic factors affecting survival on the island are wind, temperature, water, and light.
15. Arctic foxes, ptarmigans, shrubs, lichens, grasses, and insects are the island’s biotic factors.
16. A likely relationship is predation of the fox on the ptarmigan.
17. grasses, shrubs, and lichens
ptarmigans and insects
Arctic foxes
18.
19. Camouflage is an advantage for making stealthy attacks on its prey.
20. The ptarmigan would increase in numbers. This could reduce the amount of vegetation
because of overgrazing.
21. a.
Secondary succession would take place because soil is already present.
b.
Fire increases the amount of carbon dioxide in the air.
22. A reduction in the hare population would result in a reduction of the lynx’s food source and,
therefore, a reduction in the lynx numbers. This question may be extended by referring
students to the following newspaper article.
Global Warming Trend Takes Toll on Hare Population
Could change key cycle in boreal forest as less snow gives advantage to lynx
Andy Ogle
Journal Staff Writer
EDMONTON
Global warming has the potential to change one of the defining cycles in Canada’s immense
boreal forest region, says a University of Alberta wildlife scientist.
The 10-year population boom-and-bust cycle of the snowshoe hare and of the Canadian
lynx that preys on the hare is a signature mechanism in the boreal forest, says Stan Boutin,
whose research on the cycle has included a decade’s worth of tracking lynx in the snow in
Kluane National Park in the Yukon.
A new study, co-authored by Boutin, suggests the lynx’s ability to catch hares is tied
directly to snow conditions.
When there are few warm spells, the snow remains deep and fluffy, the lynx sinks in deeper
than the hare, and the hare escapes more easily. More winter thaws shift the advantage to
the lynx.
The team of researchers from Norway, the United States and Canada, which includes
evolutionary ecologist Nils Stenseth from Oslo, said snow conditions could be a key factor in
explaining the regional distribution and genetic variability of the Canadian lynx.
Their paper, the latest in a series on the lynx, was published this week in the Proceedings of
the National Academy of Science in the United States.
“The hare is the most dominant herbivore in the system and that oscillation really creates
the diversity of wildlife we see in the forest. So if we start to change that 10-year pulse, it
will likely have some big effects on a lot of things affected by the cycle. Virtually all the
predators in our northern forests have some sort of link to the cycle.”
Global warming could affect that 10-year cycle, Boutin said, although he’s not yet convinced
it would.
“That’s speculative at this point, but you could certainly work through the logic and say if
we start to have winters like we’ve been having in Edmonton, where you get far more
freeze-thaw cycles, that may shift the balance towards the lynx.”
The current study appears to bolster Stenseth’s contention that the 10-year cycle differs
across the country and those differences are tied to large-scale climate patterns.
“The overall pattern is always the same—a 10-year cycle,” Boutin said. But there are
regional variations, with genetically different lynx populations west of the Rockies, in the
central areas and in Eastern Canada.
The Rockies represent a physical barrier that explains the differences between western and
central populations. No such physical barrier exists between central and eastern
populations, yet there seems to be an invisible barrier that roughly follows the ManitobaOntario border.
The study says that barrier is produced by climate differences, notably the North Atlantic
Oscillation, which has an effect somewhat like that of el Nino in the Pacific. When there are
fewer warm spells in the Atlantic region, there are more warm spells in the continental
region and vice-versa.
The result is snow conditions that are always different between the two regions,
discouraging migration and mixing of populations.
Much of the data on how snow conditions affect lynx kill rates came from a decade of
research by Boutin and a small army of colleagues and graduate students tracking lynx in
Kluane National Park in the Yukon from the mid-1980s into the mid-1990s.
“Most of our work focused on looking at the kill rate to see how it tied in with the population
cycle,” Boutin said. But they also took detailed notes on snow conditions.
They wanted to know whether the snowshoe hare population inevitably crashed after a peak
because the burgeoning hare population ate itself out of house and home, or whether
predators—chiefly the lynx—caused the crash.
It turned out to be a mix of the two, Boutin said.
“Food supply slows the rate of increase but then the predators really pound them and knock
them back down, and keep them low for a period of time before they recover again.”1
1
Andy Ogle, “Global Warming Trend Takes Toll on Hare Population,” The Edmonton Journal, 11 July 2004. Reproduced
by permission of The Edmonton Journal.
23. A reduction in the hare population would cause the plant numbers to increase, other
herbivores would increase because of less competition, and other predators (such as the
wolf) may be reduced in numbers.
24. Other factors could include disease, competition, other predators, and a shortage of food.
25.
26. a.
Changing its fur colour creates two types of camouflage to help the hare hide in more
than one season. Brown fur blends with summer trees and bushes, while white fur blends
in with snow.
b. At one time, most members of the population likely had only one fur colour, but a few
members of the population had two colours because of a mutation. Over time, the
members that had two fur colours were better able to escape predators, so they survived
to pass on their genes. The single-coloured hares stood out against one of their habitat
backgrounds, so they were easier targets for predators and were killed off. Eventually,
only hares with two fur colours were left in the population.
27. Forest fires, the increased burning of fossil fuels, and the cellular respiration of animals add
carbon dioxide to the atmosphere.
28. a. The process of secondary succession has occurred to create grasses and shrubs for hares
to browse. More hares mean more lynxes can be supported by the same area.
b. The prevention of forest fires means that there will be less recycling of nutrients, no
succession will take place, and biodiversity will be reduced.
29. Abiotic tests would include light intensity, wind speed, soil pH, soil temperature, the amount
of precipitation, and soil quality.
30. Answers will vary. Refer to the Science 20 Data Booklet for Skills Scoring Guide.
a.
For example, students choose soil pH for their manipulated variable and weed growth
for the responding variable. The controlled variable is the weed species and its location
of growth.
b.
In this case, students could set up the experiment where different areas supporting
the growth of the weed had different values for soil pH.
c.
Predictions would be that the weeds could likely tolerate a wide range of soil pH values
because weeds are found in a variety of different locations, all with varying values for
soil pH.
31. a.
The fifth section acted as a control.
b.
The manipulated variable is the type of herbicide.
c.
The responding variable is the growth of the weed.
d.
Controlled variables for this experiment would include the size of the crop section, the
amount of water, the amount of sunlight, the time of day, as well as the frequency of
recording observations.
32. Mosquitoes play an important role in aquatic food chains. As was demonstrated in the
description of freshwater ecosystems in Chapter 1, mosquito larvae are first-order consumers
that feed on algae. The mosquito larvae then become an important food source for frogs,
dragonfly larvae, and small fish like the stickleback. If this link in the food web is completely
removed, it affects the whole aquatic ecosystem.
33. Answers will vary. Students should include at least one producer and one decomposer. The
most efficient arrangement would be to have the humans serve the role of the primary
consumers. If humans are herbivores, it dramatically reduces the energy losses that occur as
humans are placed in higher trophic levels on the energy pyramid.
34. Answers will vary. Again, it is
essential that producers and
decomposers both be present. It is
unrealistic to think that this selfcontained environment could
support many secondary consumers
and unlikely that it could support
any tertiary consumers. This food
web illustrates an approach where
the humans have a vegetarian
lifestyle.
35. Answers should address energy flow and matter cycling. It is critical that a continual source
of energy be utilized because energy will be continually leaving the system in the form of
heat. Therefore, answers may include energy-creating and energy-saving devices like solar
panels, access to sunlight for growing plants, and attempts to minimize energy losses. If the
habitat is to be truly self-contained, then it must be sealed so that no matter can escape. All
essential chemical compounds must be recycled with systems that attempt to mimic Earth’s
biogeochemical cycles. As an example, the production of oxygen for human inhabitants
exhaling carbon dioxide must be considered. Water is another important substance to
consider, given its central role in supporting life.
36. Sample answers for ensuring that these compounds were maintained at appropriate levels
are as follows:

Carbon cycle—ensure enough producers are available to absorb carbon dioxide, and
limit the combustion of carbon materials.

Nitrogen cycle—the presence of nitrifying and denitrifying bacteria is essential, as is
the ability to supplement nitrogen levels by adding bacteria.

Water cycle—collect and filter waste water, and set up the collection of naturally
purified water from evaporation and transpiration.

Wastes—compost organic wastes, and have decomposers to help with the recycling
of matter.
37. Less variation would mean that the populations of the various life forms could be more
susceptible to diseases and to the effects of harmful mutations. Since this is a closed
population, similarities exist to other closed populations that evolved in isolation on Earth.
The Galapagos Islands come to mind as one example. If this environment could sustain itself
for thousands or millions of years, new species could eventually develop.
38. a. This system is similar to Earth because Earth is a spaceship that relies upon energy from
the Sun, but is otherwise self-contained. Energy flows through the food webs of the
biosphere and matter is cycled.
b. The most obvious difference is that the Earth system is so much larger. Subtle
differences include the fact that Earth is incredibly complex and intricate. It is difficult to
conceive of an artificial system designed by humans that could be as sophisticated. Part
of the reason for the challenge in designing systems for supporting life as sophisticated
as the biosphere is that the fossil record suggests that the Earth system has been slowly
developing over billions of years. Even if it took one human lifetime to design a selfcontained habitat, this time falls far short of the time that it took to develop the
biosphere.
c. Earth is currently the only self-contained habitat that humans have. People better look
after it, because it is the only life-support system available.
Science 20 © 2006, Alberta Education