Evolution - worksheet answers
Glossary:
Adaptation: changes in the traits of a population of a species that make it better suited (fitter)
for its environment.
Artificial selection: selection by humans of particular traits in a species that humans want to
keep or develop.
Convergent evolution: where different species develop similar traits because they share the
same environment e.g. penguins, dolphins and sharks.
Divergent evolution: where one species gives rise to separate species over time because of
adaptations to a new environment e.g. the Galapagos finches.
Homologous structures: are anatomical structures that are similar.
Mutation: a random change in the DNA of an individual.
Natural selection: where individuals of a species which are better suited (more fit) for their
environment, live to breed and produce offspring where as those which are not suited do not
(i.e. nature selects).
Parallel evolution: where populations of a species are separated by geography or other
circumstances and develop as separate species with similar traits e.g. western and eastern
kangaroos.
Speciation: the formation of a new species. i.e. a new population which cannot or will not
breed with another population to produce viable offspring.
Variation: the diversity of genetic material within a population.
Questions:
1.
A gene pool is the collective genetic information of a population or species.
2.
Evolution (to me) describes the changes that have occurred in living organisms over the
history of life on earth. By looking at the relationships between species, connections can be
drawn to find common origins and ancestors.
3.
Lamarck:
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The only Giraffes that can survive are those that can eat leaves from tall trees.
Those individuals that can't reach the leaves will eventually stretch their necks.
Once an individual has stretched its neck, then this trait will be passed on to the next
generation.
Darwin:
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Giraffe population is genetically diverse.
Some longer necked individuals are able to reach the food source (tall trees).
These longer necked individuals are fitter (more likely to survive and reproduce).
Over time there are a greater proportion of longer necked giraffe genes in the population.
Eventually, over a long period of time, all giraffes have long necks.
4.
Selection pressure is the result of the natural or artificial pressures that kill a proportion of a
population, but some will survive. Those that survive are the ones that will pass their traits
(the very same traits that saved them from being killed by the selection pressure) on to the
next generation.
5.
The fossil record is incomplete because some animals do not have anatomical structures (like
shells, bones) that leave fossil evidence behind. Fossils are usually found in a limited number
of places and relate to a limited time period.
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6.
Evolution is a result of changes through generations. The more generations that can be born
in a year, the quicker the evolution of that species.
7.
Gondwana land was an ancient super continent comprising Australia, New Zealand,
Antarctica and South America. Continental drift caused these continents to separate. Before
they separated, there was a flightless bird that was the common ancestor for the individual
species listed in the question. So much time has elapsed, and the environments of these
animals have changed greatly, as a result, the species adapted to become separate species.
8.
a) Butterflies and bats are an example of convergent evolution. They come from very
different ancestry (insects and mammals) but have nevertheless developed similar
anatomical structures (wings).
b) Dolphins and porpoises are an example of divergent evolution. They are closely related,
but have recently evolved into separate species with slightly different traits (teeth shape).
c) Sharks and whales are an example of convergent evolution. They come from very
different ancestry (fish and mammals) but have nevertheless developed similar
anatomical structures.
d) Snakes and lizards are an example of divergent evolution. They are closely related (both
reptiles), but have evolved into separate species with slightly different traits (legs / none).
e) Eels and earthworms are an example of convergent evolution. They come from very
different ancestry (fish and invertebrates) but have nevertheless developed similar
anatomical structures.
f) Zebras and horses are an example of divergent evolution. They are closely related (both
horse-like thingies), but have evolved into separate species with slightly different traits
(stripes/ not), which make them better adapted to their environment.
9.
Survival of the fittest means that only those individuals who are well suited to their
environment (fit) are those that will survive to reproduce. This means that their genes are the
ones that are carried on through generations and may eventually lead to the evolution of a
new species.
10.
Extinction is when the last surviving population of a species is getting smaller in number and
therefore the total amount of genetic information for that species (its gene pool) is also getting
smaller. Once the species dies out (becomes extinct, so does its gene pool.
11.
Things become extinct because they are no longer fit for their environment.
12.
Yes, of course it could ... in fact, current theory is that a meteor caused the extinction of the
dinosaurs. Ice ages, global climate change, volcanic activity, severe drought...any of these
could cause extinctions.
13.
Artificial selection is when humans choose the traits that are going to be passed on to the
next generation, as opposed to natural selection where the traits are selected by nature that
best fit the environment. Artificial selection does not make a population better suited to an
environment - just to artificially determined ideas of what good traits are (e.g. fluffy poodle
hair)
14.
Pet budgerigars are the product of artificial selection. The colours selected will necessarily
make them well suited to the wild, but humans like them.
15.
Well this is a huge question... there is no right answer - but it is a good prompt for discussion.
16.
Bacterial populations have genetic diversity. When we try to kill a whole population with antibiotics, some (a very small number) will survive. Those that survive are the ones that will
pass their traits (the very same traits that saved them from being killed by the anti-biotics) on
to the next generation. We are effectively selecting this trait (anti-biotic resistance).
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