Name: _______________________________________Class: __________________ Date: ________________
Mechanisms for Evolution
There are five main mechanisms for evolution. They are the following:
(1) Gene Flow: The movement of alleles into or out of a population
(2) Genetic Drift: The change in allele frequencies as a result of chance
(3) Mutations: The random change in the DNA of an organism
(4) Non-Random Mating: Individuals have a choice in who they mate with – not random
(5) Natural Selection: Better adapted (more fit) individuals to their environment survive and
reproduce
Read each scenario. Then identify which type of mechanism is being described.
Scenario 1 _________________________________
The males of a certain bird population have either blue, red or green
feather variations. The females seem to prefer males who have red or
blue feathers. In observing the population, it is found that green-
feathered birds are becoming less and less common.
Scenario 2 __________________________________
There is a population of dairy cows being bred by humans. The humans
choose only the cows that produce over 10 gallons of milk per day to
breed.
Scenario 3 _________________________________
In a population of ladybugs, a mutation in the offspring of one bug
produces entirely black bugs. These bugs are more successful in escaping
predators. Overtime, this gene becomes more popular in the population
and the ladybug population loses its red color.
Scenario 4 _________________________________
There is a population of squirrels who have bushy or hairless tails. 75% of
the hairless tailed squirrels randomly leave the area and migrate to
Branchburg. Meanwhile, 5 new squirrels enter the area and have straight
haired tails.
Scenario 5 _________________________________
Ten years ago, in a small population of ducks, two sizes of
eyes were observed, large and small. Three ducks have large
eyes and 7 have small. 2 of the large-eyed ducks are
randomly hit by cars and killed. Today, no large-eyed ducks
are present in the population.
1
Name: _______________________________________Class: __________________ Date: ________________
Scenario 6 _________________________________
The peppered moth comes in three different colors: black, white, and gray.
The black moth lives in one city and the white moths live in a different city.
The white moths start flying to the city where the black moths live and begin
mating with the black moths producing gray moths.
Scenario 7
_________________________________
The Northern Right Whale lives off the coast of Georgia
near Savannah. There are only a few hundreds of these
whales left in the world and they have been forced to
inbreed (have offspring with whales they are very close
relatives). The population of whales keep getting
smaller and smaller.
Scenario 8 _________________________________
Polar bears live in the North Pole. They are very large white bears with
black skin. Recently, a new type of polar bear was found in the North Pole
and it is very different from the polar bears we are all familiar with. This
polar bear cannot mate with the other kind since it’s DNA is different.
Scenario 9 _________________________________
There used to be two types of giraffes: some with long necks (like the ones we
know of today) and some with short necks. Giraffes live in the savannah where
the trees have tall branches, so the animals need to find a way to reach the leaves.
The giraffes with the long necks survived to pass their traits to their offspring
and the giraffes with the short necks eventually became extinct.
Scenario 10
_________________________________
Beagles used to either have colored tail tips or white tail
tips. Hunters liked the white tipped better because they
were able to spot the dog when was bending over a rabbit
hole. Hunters started to breed white tipped beagles with
other white tipped beagles. Today, the majority of beagles
have tails with white tips.
