5 Points of Darwin’s Natural Selection
Read the following situations below and identify the 5 points of
Darwin’s natural selection.
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.
a. What worm has natural selection selected AGAINST?
FOR? nocturnal worms
diurnal worms
b. Darwin's 5 points: Identify the 5 points in the scenario above.
Population has variations. There are 2 types of worms in the area
(diurnal and nocturnal)
Some variations are favorable. Birds do not eat nocturnal worms
(nocturnal worms advantage)
More offspring are produced than survive. 100 of the original 500
worms survive to reproduce
Those that survive have favorable traits. More nocturnal worms
survive and reproduce
A population will change over time. Nocturnal worm population
increases; diurnal worm population decreases
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.
a. What bear will natural selection select AGAINST?
FOR? thick coats
thin coats
b. Darwin's 5 points: Identify the 5 points in the scenario above.
Population has variations. There are 3 types of bears (thick,
medium, and thin coats)
Some variations are favorable. Thick coats provide warmth to
survive (thick coat advantage)
More offspring are produced than survive. Half of the total cubs
born survive
Those that survive have favorable traits. Bears with thicker coats
have a higher survival rate
A population will change over time. Survial rate of bears with
thicker coats rises, population of bears with thin coats will
gradually decrease
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 approximately
10 eggs (each mother only lays 1), but many rodents break into the
eggs and eat the fetus before they hatch.
a. What ostrich will natural selection select AGAINST?
ostriches
FOR?
fast ostriches
slow
b. Darwin's 5 points: Identify the 5 points in the scenario above.
Population has variations. There are slow and fast ostriches
Some variations are favorable. Fast ostriches can out run the
jackals (fast ostriches advantage)
More offspring are produced than survive. Rodents eat the eggs
before they hatch
Those that survive have favorable traits. The fast ostriches can
outrun the jackals
A population will change over time. Fast ostriche population
increases; slow ostriche population decreases
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.
a. What rabbit will natural selection select AGAINST?
and flowers
FOR?
eat grass
Eat berries
b. Darwin's 5 points: Identify the 5 points in the scenario above.
Population has variations. There are 2 types of rabbits (eat grass
and eat berries and flowers)
Some variations are favorable. Rabbits that eat grass have food
(grass eating advantage)
More offspring are produced than survive. Babies are being eaten
by predatos or starving
Those that survive have favorable traits. The grass eating rabbits
can eat the others cannot
A population will change over time. The population of grass eating
bunnies increases and the population of berry/flower eating
bunnies decreases
Living things that are well adapted to their environment survive and reproduce.
Those that are not well adapted don’t survive and reproduce. An adaptation is any
characteristic that increases fitness, which is defined as the ability to survive and
reproduce.
Over many generations heritable adaptive characteristics become more common in a
population. This process is called evolution by natural selection. Evolution by
natural selection takes place over many, many generations. Evolution by natural
selection leads to adaptation within a population. The term evolution by natural
selection does not refer to individuals changing, only to changes in the frequency of
adaptive characteristics in the population as a whole.