Evolution by Natural Selection WKS Lab ANSWER KEY Zu3kag | PDF ... - Free Printable

Let’s go step by step to understand what’s happening in the figures and answer each question clearly.

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Part 1: Figures 1–3 — What’s happening?

In Figure 1, we see a group of mice on gray ground. Some are white, some are brown (or tan). There’s no predator yet.

In Figure 2, a bird (predator) is flying above. It’s likely hunting the mice.

In Figure 3, after the bird has hunted, there are fewer mice overall — but notice: more brown mice remain, and fewer white ones.

Why? Because the ground is grayish-brown. Brown mice blend in better with the ground → harder for the bird to see them → more likely to survive. White mice stand out → easier for the bird to catch → more get eaten.

So yes — the population changed: more brown mice survived because they were better camouflaged. That’s natural selection!

✔ Answer to first question:
YES: THERE ARE MORE BROWN MICE IN FIGURE 3 THAN IN FIGURE 1.
Because brown mice are better hidden from predators on this ground color, so more of them survived to reproduce.

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Part 2: Which mouse is the fittest? (Female mice table)

Fitness = ability to survive AND produce offspring that can also survive and reproduce.

Look at the table:

| Color | Black | Tan | Tan & Black | Cream |
|-------------|-----------|------------|-------------|------------|
| Age at Death| 2 months | 8 months | 4 months | 2 months |
| Pups | 0 | 11 | 3 | 0 |
| Speed | 8 cm/sec | 6 cm/sec | 7 cm/sec | 5 cm/sec |

Even though the black mouse is fastest, it died young and had zero pups → not fit.

Cream mouse: same — died young, no pups.

Tan & Black: lived 4 months, had 3 pups — okay, but not best.

Tan mouse: lived longest (8 months), had most pups (11). Even if slower, she survived longer and made more babies → those babies can grow up and have their own babies.

✔ So the tan mouse is the fittest.

Answer:
THE FITTEST MOUSE IS THE TAN MOUSE BECAUSE IT LIVED THE LONGEST, AND PRODUCED THE LARGEST SIZE OFFSPRING.

*(Note: “Size” here probably means number — typo in original text. Should be “largest number of offspring.”)*

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Part 3: If fur color is similar to mother’s, what color will be most common among pups?

Since the tan mouse is the fittest and produced 11 pups (way more than others), and her pups will likely be tan too (since fur color is inherited from mom), then…

✔ Most pups will be tan.

Answer:
TAN COLOR.

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Part 4: Male lions — who is the fittest?

Definition again: Fitness = survive + produce offspring that survive to adulthood and can reproduce.

Table:

| Lion Name | George | Dwayne | Spot | Tyrone |
|-----------|--------|--------|-------|--------|
| Age at death | 13 yrs | 16 yrs | 12 yrs | 10 yrs |
| Cubs fathered | 19 | 25 | 20 | 20 |
| Cubs surviving to adulthood | 15 | 14 | 14 | 19 |
| Size | 10 ft | 8.5 ft | 9 ft | 9 ft |

George: lived long, many cubs, 15 survived → good.

Dwayne: lived longest (16 yrs), fathered most cubs (25), but only 14 survived → not as many made it.

Spot: average everything.

Tyrone: died youngest (10 yrs), but 19 of his 20 cubs survived to adulthood → almost all made it! And he still fathered 20 cubs.

Remember: fitness isn’t just about living long or having lots of babies — it’s about how many of your babies actually grow up to have their own babies.

Tyrone’s cubs mostly survived → they’ll pass on his genes → so he’s the fittest.

✔ Answer:
TYRONE IS THE FITTEST LION BECAUSE IN THE END, IT GENERATED THE LARGEST NUMBER OF CUBS THAT SURVIVED TO ADULTHOOD (AND THEREFORE WERE ABLE TO REPRODUCE).

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Part 5: Suppose Tyrone passed on infection-resistance genes...

If his cubs are more likely to survive because of these genes, then those genes will become more common in the next generation — because more cubs with those genes live to reproduce.

That’s exactly how natural selection works: helpful traits become more common over time.

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Final Answer:

YES: THERE ARE MORE BROWN MICE IN FIGURE 3 THAN IN FIGURE 1.
THE FITTEST MOUSE IS THE TAN MOUSE BECAUSE IT LIVED THE LONGEST, AND PRODUCED THE LARGEST NUMBER OF OFFSPRING.
TAN COLOR.
TYRONE IS THE FITTEST LION BECAUSE IN THE END, IT GENERATED THE LARGEST NUMBER OF CUBS THAT SURVIVED TO ADULTHOOD (AND THEREFORE WERE ABLE TO REPRODUCE).