Question

. DARWIN & NATURAL SELECTION
In each of the following scenarios, identify the parts of Darwin’s theory. 1.A species of moth has a 2 varieties of wing color: brown and white. As winter approaches, the
trees where the moths live loose their leaves. The moth’s predators are birds who hunt for the
moths as they rest on the dark tree bark. Every moth lays 100 eggs, but only about 10 from each
egg cluster live to adulthood.
Which moth variety do you think will be selected against? ____________________________
Which trait is favorable? Why? _________________________________________________
__________________________________________________________________________
What are the variations in this population? ________________________________________
How does this species overproduce? ____________________________________________
How will this species change over time? _________________________________________
__________________________________________________________________________
2. Only 1 out of 1000 sea turtles survives it to adulthood. From the moment they hatch, sea
turtles must strive for survival. They race across the beach and battle the waves moments after
their birth. Throughout this time, predators are stalking them for an easy meal. Some sea turtles
are faster than others.
Which sea turtle do you think will be selected against? ______________________________
Which trait is favorable? Why? _________________________________________________
__________________________________________________________________________
What are the variations in this population? ________________________________________
How does this species overproduce? ____________________________________________
How will this species change over time? _________________________________________
__________________________________________________________________________
3. Storks are a species of bird that only has the time and energy to provide for one chick. Storks
lay two eggs. After the eggs hatch, the birds feed both chicks for a week. After a week’s time, the
smaller chick is thrown out of the nest and left to fend for itself. From then, the parents focus
their efforts only on the larger chick.
Which stork do you think will be selected against? __________________________________
Which trait is favorable? Why? _________________________________________________
__________________________________________________________________________
What are the variations in this population? ________________________________________
How does this species overproduce? ____________________________________________
How will this species change over time? _________________________________________
__________________________________________________________________________

Answer 1

1)
- Selected against: White moths.
- Favorable trait and why: Brown wing color — it camouflages moths on dark bark, reducing bird predation and increasing survival.
- Variations: Wing color (brown vs. white) among individuals.
- Overproduction: Each moth lays ~100 eggs but only ~10 survive to adulthood — more offspring are produced than can survive.
- How species will change over time: Brown moths will survive and reproduce more, so the frequency of the brown-color trait will increase in the population (population evolves toward mostly brown moths).

2)
- Selected against: Slower sea turtles.
- Favorable trait and why: Faster hatchlings — speed helps them escape predators and the surf, so fast individuals survive at higher rates.
- Variations: Differences in hatchling speed, size, strength, timing of hatching.
- Overproduction: Females produce many eggs/hatchlings but only about 1 in 1000 reaches adulthood.
- How species will change over time: Faster individuals leave more offspring, so the population will tend to have more fast hatchlings over generations (increase in average speed/traits that improve escape).

3)
- Selected against: The smaller chick (the weaker, slower-growing chick).
- Favorable trait and why: Larger size / faster growth / stronger competitive behavior — these traits let a chick win parental care and survive.
- Variations: Size at hatching, growth rate, vigor, begging behavior.
- Overproduction: Parents lay two eggs but can only raise one chick to maturity, so more offspring are produced than can be supported.
- How species will change over time: Traits that give chicks a competitive advantage (larger eggs, faster growth, stronger begging) will be favored and become more common, so average competitive ability/size in chicks may increase over generations.