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? diurnal worms
FOR? nocturnal 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? thin coats
FOR? thick 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? slow ostriches
FOR? fast ostriches
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? Eat berries and flowers
FOR?
eat grass
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.