Download Chapter 2 Review Questions

Chapter 2 Review Questions
Knowledge
1. Primary succession is the process of changing—in successive stages—an environment from
an area of bare rock and few species to a complex community.
2. Logging, forest fires, tilling soil, or any other event that removes the vegetation without
removing the soil could all cause the process of secondary succession to begin.
3. Secondary succession occurs where soil already exists. It is a much faster process than
primary succession.
4. Open populations are affected by the number of births, deaths, immigration, and emigration,
while closed populations do not have any immigration or emigration to affect their numbers.
In many cases, closed populations are artificial.
5. Carrying capacity is the maximum number of individuals that can be sustained in a given
environment for an indefinite period.
6. This graph shows the exponential growth of a population.
7. The carrying capacity of a population is outlined in this graph.
8. a.
The ability to fly allows an owl the advantage of being able to see from a great
vantage point and attack from the air.
b.
A sharp beak and talons are good for killing and tearing apart prey.
c.
Huge eyes allow for good vision even in low light or dark conditions.
d.
Feathers that muffle the sound of flying make the owl a stealthier hunter. The prey
does not even hear the owl approaching for a kill.
9. The three main concepts of Darwin’s theory of natural selection are the following:



Organisms usually produce more offspring than can survive.
There is variation among individuals in a population.
Organisms compete for limited resources.
10. Fitness in biological terms is the ability of an organism to survive and then successfully
reproduce. It is not solely a measure of an individual’s strength, speed, or health, although
this may influence its fitness.
11. A mutation is a change to the genes. The genes provide instructions to the body and the
change in instructions may be harmful—this is demonstrated by cancer. A mutation may
provide an advantage, for example, a changed beak shape for the Galapagos finch for a more
varied diet. Eye colour for a cat is an example of a neutral mutation.
12. Acceptance of Darwin’s theory is dependent upon acknowledging the evidence preserved in
the fossil record that organisms have changed over time. People who are reluctant to accept
this evidence have difficulty with Darwin’s theory.
13. Darwin suggested that the variety of finches on the islands all came from a common seedeating finch ancestor. Within the population of offspring there was a variation in many traits,
including some finches born with slightly different beaks. This enabled them to eat different
types of food that, in turn, provided them with the advantage of less competition for that
food source. Those finches best suited to the new food source survived to breed and
demonstrated their superior fitness to other members of the population—these finches were
able to pass on their adaptation of being able to utilize a new food source to their offspring.
Over many generations, several new species of finches developed that were well adapted to
eating different foods than their ancestors did.
14. Asexual reproduction does not require a mate for reproduction. Time and energy is saved by
simply budding or sending a runner out to create a new plant. Asexual reproduction is fast
(as in bacteria). A drawback to asexual reproduction is that there is a lack of variation, which
limits natural selection and evolutionary change.
Applying Concepts
15. The conditions that allowed the exponential growth of the beavers on Tierra del Fuego
include a vast food supply of old-growth forests and no natural predators.
16. Similarities between these two situations would be the exponential growth of both
populations after they are introduced by humans to a new habitat where there is a lack of
predators and competition. In both cases, the herbivores are causing environmental
destruction and are conflicting with the interests of the people who introduced them.
17. A difference between the two situations is the fact that the beavers are aquatic animals and
the potential for them to spread further is a risk. The reasons for introduction also differ
between the two situations—the beavers were introduced for fur and the rabbits were
introduced for food and sport.
18. Note the following polar-bear advantages.
Adaptation
slightly webbed toes
white fur
19. a.
b.
Reasons for Advantage
improves swimming after prey
helps polar bear sneak up on its prey by blending in
with its surroundings
a thick layer of fat and black
skin underneath fur
thick fat acts as insulation and black skin helps
absorb heat
female polar bears hibernate
in dens with cubs until spring
saves on energy required for moving and hunting—
can conserve energy and use it for producing milk
for young
ability to stand up on hind
legs
allows bear to see prey over snowdrifts or get a
better scent of prey
covers its black nose when
stalking a seal
increases its camouflage
The conifers preserve their place as the dominant species by keeping their
environment most favourable for conifers.
Species such as grasses and shrubs are not able to grow as well in a climax forest—
this creates stability in the community. The process of succession has ended until the
climax community is removed.
20. The disturbed area around the volcano is going through the process of primary succession.
The soil has been removed and the graph shows a large number of pioneer species, such as
lichens and mosses.
21. Answers will vary somewhat, but the three bar graphs should look similar to these.
22. It would be unlikely for someone to see an equal amount of each type of organism in the
sample area. This is because one type of organism creates conditions unsuitable for the
growth of another type of organism. The process of succession replaces one dominant
community with another. For example, tall coniferous trees would create too much shade for
grasses or shrubs to thrive.
23. The graph should look similar to this one.
24. The insect population in terrarium #1 is displaying S-curve growth. The population reaches
its carrying capacity and stays there. The insect population in terrarium #2 is displaying Jcurve growth and goes through population explosions and crashes.
25. If both insect populations were placed in the same terrarium, the insects that reproduce
exponentially would probably outcompete the slower reproducing insects. The rapidly rising
population of the insects that were in terrarium #2 would eat all the food before the other
population had a chance to reach its carrying capacity.
26. The sickled cells would have a harder time carrying oxygen because of their shape.
Individuals with sickle cell anemia would constantly be short of oxygen.
27. Although the sickle cell anemia mutation makes individuals sick, it provides resistance to
malaria. Illness from sickle cell anemia is a better alternative than death from malaria, so the
gene persists in the population.
28. The removal of malaria from the population would probably result in a reduction in the
number of individuals who carry the sickle cell anemia mutation over time, because carrying
the mutation would no longer be an advantage.
29. Darwin would explain the development of the prehensile tail of the New World monkeys as
follows.
At one time, most New World monkeys had non-prehensile tails, but because of natural
variation (mutation) a few had tails that were more flexible. The more flexible tails provided
an advantage for moving through the trees, and these individuals were able to find food,
mates, and/or escape predators better because of this adaptation. The flexible-tail monkeys
were better able to survive to create more offspring, and soon flexible tails were found in
much of the population. Over time, more and more flexible tails were selected until a true
prehensile tail had developed.
30. Weismann’s experiment did not support Lamarck’s idea of acquired inheritance of
characteristics because there was no change to the genes or instructions in the mice to
produce shorter tails. Lamarck’s theory was not accepted because there was no evidence to
support the theory.
31. It is still important to study Lamarck because he caused people to think about the idea that
populations of organisms change over time. This was a revolutionary idea for his time, and
he helped pave the way for Darwin’s ideas.
Science 20 © 2006, Alberta Education