Darwin's Natural Selection Worksheet featuring three scenarios: nocturnal vs. diurnal worms, polar bears with different coat thicknesses, and fast vs. slow ostriches, each illustrating natural selection principles.

Let's go through each scenario and identify Darwin’s 5 Points of Natural Selection:

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Darwin’s 5 Points of Natural Selection:

1. Population has variations.
2. Some variations are favorable.
3. More offspring are produced than survive.
4. Those that survive have favorable traits.
5. A population will change over time.

We'll apply these to each situation.

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## Scenario 1: Worms (Nocturnal vs Diurnal)

> There are 2 types of worms: nocturnal (eat at night) and diurnal (eat during the day). Birds eat during the day and only eat the diurnal worms. Nocturnal worms hide in burrows during the day. Each spring, worms produce ~500 babies, but only 100 live long enough to reproduce.

a. What worm has natural selection selected AGAINST?

Diurnal worms

What worm has natural selection selected FOR?
Nocturnal worms

Darwin’s 5 Points:

1. Population has variations.
→ There are two types of worms: nocturnal and diurnal — this is variation in behavior (timing of activity).

2. Some variations are favorable.
→ Being active at night (nocturnal) is favorable because they avoid birds that hunt during the day.

3. More offspring are produced than survive.
→ 500 babies are born, but only 100 survive to reproduce → more are born than can survive.

4. Those that survive have favorable traits.
→ The nocturnal worms survive because they avoid predation; diurnal worms are eaten.

5. A population will change over time.
→ Over generations, more nocturnal worms will be present because they are more likely to survive and reproduce.

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## Scenario 2: Polar Bears (Thick, Thin, Medium Coats)

> Three types of polar bears: thick coat, thin coat, medium coat. It’s fall, temperatures dropping fast. Bears must stay warm or freeze. Many mothers had 2 cubs, but due to cold, many now have only one.

a. What bear will natural selection select AGAINST?

Bears with thin coats

What bear will natural selection select FOR?
Bears with thick coats

Darwin’s 5 Points:

1. Population has variations.
→ Variation in fur thickness: thick, medium, thin coats.

2. Some variations are favorable.
→ Thick coats help retain heat in cold weather → more favorable for survival.

3. More offspring are produced than survive.
→ Mothers have 2 cubs, but many don’t survive the harsh winter → not all offspring survive.

4. Those that survive have favorable traits.
→ Cubs with thick coats are more likely to survive the cold; those with thin coats are more likely to die.

5. A population will change over time.
→ Over time, more bears with thick coats will dominate the population as they are better adapted.

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## Scenario 3: Ostriches (Fast vs Slow Runners)

> Two types of ostriches: fast runners (up to 40 mph) and slow runners. Jackals run up to 35–40 mph and love to eat ostriches. A flock lays ~10 eggs (each mother lays 1), but rodents eat eggs before hatching.

a. What ostrich will natural selection select AGAINST?

Slow-running ostriches

What ostrich will natural selection select FOR?
Fast-running ostriches

Darwin’s 5 Points:

1. Population has variations.
→ Ostriches vary in running speed: fast and slow.

2. Some variations are favorable.
→ Fast-running ostriches can escape jackals better → more likely to survive.

3. More offspring are produced than survive.
→ 10 eggs laid, but rodents eat eggs before hatching → many don’t survive to adulthood.

4. Those that survive have favorable traits.
→ Fast runners are more likely to evade predators and survive to reproduce.

5. A population will change over time.
→ Over generations, more fast-running ostriches will be present because they are more likely to survive and pass on their genes.

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✔ Summary Table:

| Scenario | Selected AGAINST | Selected FOR | Key Trait |
|--------|------------------|--------------|---------|
| 1. Worms | Diurnal worms | Nocturnal worms | Activity time (night vs day) |
| 2. Polar Bears | Thin-coated bears | Thick-coated bears | Fur thickness |
| 3. Ostriches | Slow runners | Fast runners | Running speed |

Each case illustrates how natural selection favors advantageous traits, leading to evolutionary change over time.

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