Topic: Evolution
Aim: Describe the theory of Natural Selection.
Directions: Read the passage below. Use textual evidence to help answer questions1 - 5.
In the 19th century, a man called Charles Darwin, a biologist from England, set off on the ship HMS Beagle to
investigate species found on the Galapagos Islands. After spending time on the islands, he soon developed a theory
that would imply that all species derived from common ancestors through a process called natural selection. Natural
selection is considered to be the biggest factor resulting in the diversity of species and their genomes. The principles
of Darwin's work and his theory are stated below.
1. One of the prime motives for all species is to reproduce and survive, passing on the
genetic information of the species from generation to generation. When species do this
they tend to produce more offspring than the environment can support.
2. Darwin noted many differences in the species he observed on his trip to the Galapagos
Islands.
3. The lack of resources to nourish these individuals places pressure on the size of the
species population, and the lack of resources means an increased struggle between these
organisms, and as a consequence, some organisms will not survive.
4. The organisms that die as a consequence of this competition were not totally random.
Darwin found that those organisms more suited to their environment (those with
favorable traits or adaptations) were more likely to survive.
5. Overtime, the offspring of individuals with helpful adaptations make up more of a
population and eventually may become a separate species.
Less suited organisms are 'weeded out' because they lack favorable adaptations. Better suited organisms, or those
with favorable adaptations, survive which led Darwin to presume that organisms had evolved over time, where the
most desirable characteristics or adaptations of a species are favored and those organisms who exhibit them survive to
pass their genes on.
As a consequence of this, a changing environment would mean different characteristics would be favorable in a
changing environment. Darwin believed that organisms had 'evolved' to suit their environments, and occupy an
ecological niche where they would be best suited to their environment and therefore have the best chance of survival.
Questions:
1. The five points to Darwin’s Theory of Evolution are stated in the reading. Write the name of each point (listed
below) in the spaces provided above.
OVERPRODUCTION
VARIATION
COMPETITION
SURVIVAL OF THE FITTEST
SPECIATION
2. Describe the reason why organisms do not survive, according to Darwin.
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3. Identify an example of a favorable adaptation that you have observed in a species.
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4. Why does Darwin believe organisms “evolve?”
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5. State Darwin’s Theory of Natural Selection in TWO sentences using the terms: favorable, unfavorable, survive,
reproduce.
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For questions 6 – 8, identify the organisms with the favorable adaptation, the organisms with the unfavorable
adaptations and the adaptation that remains if speciation were to occur.
6. There are 2 types of worms: worms that EAT AT NIGHT (nocturnal) and worms that EAT DURING THE
DAY (diurnal). BIRDS eat during the day and seem to be eating only the diurnal worms while the nocturnal
worms are in their burrows, or holes. Each spring when the worms reproduce, that have about 500 babies but
only 100 of these ever become old enough become old enough to reproduce.
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7. There are 3 types of polar bears: one with thick coats, one with thin coats and one with medium coats. It is
fall, soon to be winter. The temperature is dropping rapidly and the bears must remain warm or they will
freeze to death. Many of the bears have approximately 2 cubs (baby bears) each but due to extreme
temperatures, many mothers only have 1 cub left.
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8. There are 2 types of rabbits: those that strictly eat grass and those that strictly eat berries and flowers. A
drought occurs one year, and the plants have difficulty producing any extras (flowers, berries, etc.) and
remain green. The rabbits have reproduced all year, but many are eaten by foxes or hawks. Due to the
drought, many rabbits have starved to death.
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