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SBI 3UI Unit 2 Review: Evolution
Try these questions:
1. The process involving changes in one or more characteristics of a population that are
heritable and occur across many generations is called:
d) biological evolution
2. Which of the following statements is correct?
a) mutations provide the source for genetic variation that other evolutionary forces may act
3. What is the end product of the process of natural selection?
b) adaptation
4. Which of the following best describes artificial selection?
a) Individuals that are better adapted to their environment survive and reproduce more
successfully than others
5. Which of these is the best way to determine whether members of a population are from the
same species?
a) they can interbreed and produce viable and fertile offspring
6. Which of the following factors increases genetic variation in a population?
sexual reproduction
7. Explain why genetic diversity within a population is necessary for evolution.
If all organisms are exactly the same, all organisms are equally well adapted to their
environment. All will have the same chance of surviving and reproducing, and those
exact same traits will be passed on to all offspring.
If organisms are genetically different, and some of those differences make individuals
better adapted to their environment, they will be more likely to survive and reproduce
than other individuals, thus passing on those differences to their offspring. The
differences become adaptations (characteristics that make the organisms better suited to
their environment).
8. Explain why it is correct to talk about the evolution of populations, but it is incorrect to talk
about the evolution of individual organisms
Evolution is a process that takes generations. While one organism may be better
adapted to its environment, evolution hasn’t occurred until the beneficial traits of that one
organism have been passed on through generations of successful reproduction to the
majority of individuals of that population – after this has occurred, the population may be
sufficiently different from how it started to be considered a new species.
9. Differentiate between a geographical barrier to reproduction and a behavioural barrier.
Geographical barrier: ex. a river changes its course, separating a population into two
populations. The individuals on one side can’t breed with those on the other side any
Behavioural barrier: ex. Some animals mate in the spring while others mate in the fall.
They won’t breed with each other because they’re not “in the mood” at the same time.
10. Artificial selection can sometimes cause traits that are not desirable, such as joint problems
in some breeds of dogs. Does the same thing happen in natural selection?
With natural selection, organisms that are less fit (ex. those with joint problems) will be
less likely to survive, reproduce, and pass those traits to others. Therefore, although
organisms may develop undesirable traits, it is unlikely that they will be passed on to
later generations. There are exceptions to this, of course – especially with traits that
don’t appear until after reproduction (ex. in humans – Alzheimer’s disease).
11. Describe what mimicry is and why it is considered to be an adaptation.
Mimicry occurs when one organism looks like another – ex. stick insects mimic sticks. It
is an adaptation because it allows organisms to survive because they are better able to
evade predation.
12. How does natural selection influence adaptation?
Adaptation: a beneficial trait allows more successful survival and reproduction
Natural selection: the passing on of advantageous traits by successful reproducers
(so… natural selection determines which adaptations are successful)
13. Describe the possible fates of a mutation and the effects a mutation might have on a
population. Explain what could happen in a population when a mutation provides a selective
Helpful mutations might be passed on, as they might be adaptive
Harmful mutations are unlikely to be passed on, as individuals with harmful traits are
less likely to survive or reproduce (but it’s still possible, as those harmful traits may not
appear until later in life, when reproduction has already occurred)
Neutral mutations may or may not be passed on – they have no positive or negative
14. Today, individual giant pandas and populations of giant pandas are being isolated in many
small reserves in China. What are the genetic implications of having so many small
reserves instead of one large reserve? What could be done to encourage gene flow?
Smaller gene pool = less genetic diversity = fewer opportunities for adaptation to the
challenges of their changing environment = greater likelihood of death/extinction
Improving gene flow: one large reserve instead of many small ones; if there must be
many small ones, frequently move pandas between reserves to allow mating to occur
between populations
15. Technology that enables humans to manipulate the development of species has economic
and environmental implications. Explain how monocultures can be positive and negative at
the same time.
Monoculture: growth of one species/variety in an area (in forestry – growing all maple
trees; in agriculture – growing only rice)
Positive: simple, cost-effective, allows expertise to build up in the care of the crop,
allows grower to choose a variety that has all or most of the traits s/he wants
Negative: limited genetic variability means greater vulnerability (ex. if a virus can infect
one individual, it can probably wipe out the entire crop); limited biodiversity of other
species in the ecosystem in which the monoculture occurs (there will be few soil
microorganisms or pollinators)