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Name ___________________________________
Period ________
Evolution by Natural Selection Practice
Read the following scenarios below and answer the questions for each.
Scenario #1:
There are 2 types of worms: worms that eat at night (nocturnal) and worms that eat during
the day (diurnal). The birds eat during the day and seem to be eating ONLY the diurnal
worms. The nocturnal worms are in their burrows during this time. Each spring when the
worms reproduce, they have about 500 babies but only 100 of these 500 ever become old
enough to reproduce.
1a. 4 factors of evolution by natural selection: Identify the 4 factors in the scenario above.
1. The potential for species to increase in number. ____________________________________________________
2. Variation is due to mutations and sexual reproduction. _______________________________________________
3. Organisms compete for limited resources. _________________________________________________
4. Those that survive have favorable traits. ___________________________________________________
1b. What worm has natural selection selected AGAINST? _________________ FOR? ______________
1c. Over time, what trait would you expect to be more common in the worm population? Justify your response.
Scenario #2:
There are 3 types of polar bears: ones with thick coats, ones with thin coats and ones with medium
coats. It is fall, soon to be winter. The temperatures are dropping rapidly and the bears must be
kept warm, or they will freeze to death. Many of the bears have had ~2 cubs each but due to the
extreme temperatures, many mothers only have one
cub left.
2a. 4 factors of evolution by natural selection: Identify the 4 factors in the scenario above.
1. The potential for species to increase in number. _____________________________________________
2. Variation is due to mutations and sexual reproduction. _________________________________
3. Organisms compete for limited resources. _________________________________________________
4. Those that survive have favorable traits. ___________________________________________________
2b. What bear will natural selection select AGAINST? ___________________ FOR? _______________
2c. Over time, what trait would you expect to be more common in the bear population? Justify your response.
Scenario #3:
In ostriches, there are 2 types: ones that run fast and those that run slowly. The fast birds can
reach up to 40 miles an hour. Jackals love to eat ostrich, and they can reach speeds of up to
35-40 miles per hour. A flock of ostrich will lay ~ 10 eggs (each mother only lays 1), but many
rodents break into the eggs and eat the fetus before they hatch.
3a. 4 factors of evolution by natural selection: Identify the 4 factors in the scenario above.
1. The potential for species to increase in number.
_____________________________________________
2. Variation is due to mutations and sexual reproduction. _________________________________
3. Organisms compete for limited resources. _________________________________________________
4. Those that survive have favorable traits. ___________________________________________________
3b. What ostrich will natural selection select AGAINST? __________________ FOR? ________________
3c. Over time, what trait would you expect to be more common in the ostrich population? Justify your response.
Scenario #4:
There are two 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.). They can only try and keep themselves green. The rabbits have had
babies all year long but many are eaten by foxes or hawks. Due to the drought, many have
starved to death.
4a. 4 factors of evolution by natural selection: Identify the 4 factors in the scenario above.
1. The potential for species to increase in number.
_____________________________________________
2. Variation is due to mutations and sexual reproduction. _________________________________
3. Organisms compete for limited resources. _________________________________________________
4. Those that survive have favorable traits. ___________________________________________________
4b. What bunny will natural selection select AGAINST? __________________ FOR? ________________
4c. Over time, what trait would you expect to be more common in the rabbit population? Justify your response.
Scenario #5:
Galapagos finches can have large or small beaks. Large beaks are best for eating seeds while
small beaks are best for eating insects. In the spring, finches mate and produce 3-4 birds per
clutch of eggs. A disease on the island results in the loss of many insect species; since this is
an island, the species are unlikely to populate the area again.
5a. 4 factors of evolution by natural selection: Identify the 4 factors in the scenario
above.
1. The potential for species to increase in number.
_____________________________________________
2. Variation is due to mutations and sexual reproduction. _________________________________
3. Organisms compete for limited resources. _________________________________________________
4. Those that survive have favorable traits. ___________________________________________________
5b. What finch will natural selection select AGAINST? __________________ FOR? ________________
5c. Over time, what trait would you expect to be more common in the finch population? Justify your response.
Scenario #6:
In the desert, a species of mouse can inherit light or dark colored fur. Mice reproduce 2-3
times per year, producing 5 babies per litter. Large birds, such as hawks, prey upon these
mice in the desert. A volcano erupts covering the area with very dark lava rock.
6a. 4 factors of evolution by natural selection: Identify the 4 factors in the scenario
above.
1. The potential for species to increase in number.
_____________________________________________
2. Variation is due to mutations and sexual reproduction. _________________________________
3. Organisms compete for limited resources. _________________________________________________
4. Those that survive have favorable traits. ___________________________________________________
6b. What mouse will natural selection select AGAINST? __________________ FOR? ________________
6c. Over time, what trait would you expect to be more common in the mouse population? Justify your response.
Scenario #7:
Pneumonia causing bacteria have a very rapid life cycle, dividing and doubling their
population every hour. Some pneumonia causing bacteria have genes that give
them resistance to antibiotics; other pneumonia causing bacteria lack this trait and
are killed if they come into contact with antibiotics. A person contracts pneumonia
and takes amoxicillin (an antibiotic) to kill the infection. A week after taking the
antibiotics, the infection remains in the person’s lungs.
7a. 4 factors of evolution by natural selection: Identify the 4 factors in the
scenario above.
1. The potential for species to increase in number.
_____________________________________________
2. Variation is due to mutations and sexual reproduction. _________________________________
3. Organisms compete for limited resources. _________________________________________________
4. Those that survive have favorable traits. ___________________________________________________
7b. What bacteria will natural selection select AGAINST? __________________ FOR? ________________
7c. Over time, what trait would you expect to be more common in the bacteria population? Justify your response.
Scenario #8:
In an ecosystem, some giraffes have long necks and others have short ones. Giraffes produce 1-2 offspring
every 2 years. Giraffes are herbivores that eat shrubs that grow throughout the ecosystem. A disease
causes low-lying shrubs to die out, reducing the amount of food available to the giraffes.
8a. 4 factors of evolution by natural selection: Identify the 4 factors in the scenario above.
1. The potential for species to increase in number.
_____________________________________________
2. Variation is due to mutations and sexual reproduction. _________________________________
3. Organisms compete for limited resources. _________________________________________________
4. Those that survive have favorable traits. ___________________________________________________
8b. What giraffe will natural selection select AGAINST? __________________ FOR? ________________
8c. Over time, what trait would you expect to be more common in the giraffe population? Justify your response.