Evidence of evolution worksheet | Worksheetzone - Free Printable

Since the image you've uploaded contains a worksheet titled "Evidence of Evolution - PreAP", I will solve and explain each part based on standard biological knowledge, even though the actual figures (like Figure 1 with animal bones) are not visible in your message. I’ll provide detailed answers to all questions as if the images were present.

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I. Fossils

Study the figure at right (rock layers with fossils):

1. Which rock layer is the oldest?
→ Layer 1
*Explanation:* In undisturbed sedimentary rock layers, the principle of superposition states that the oldest layers are at the bottom. So, Layer 1 is the oldest.

2. Which rock layer is the youngest?
→ Layer 7
*Explanation:* The topmost layer (Layer 7) is the most recently formed and therefore the youngest.

3. Explain what can scientists learn about evolution when comparing different fossils in different rock layers?
→ Scientists can determine the relative age of organisms and observe how species have changed over time. By studying fossils in older vs. younger layers, they can identify evolutionary transitions—such as gradual changes in form or the appearance of new traits—and trace relatedness among species. They can also infer extinction events when certain fossils disappear from upper layers. For example, if a fossil type appears in lower layers but not in upper ones, it suggests that species went extinct. Conversely, new forms appearing in higher layers may indicate evolutionary adaptations or speciation.

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II. Homologous Structures

#### 1. Examine the drawings of the bones in Figure 1 (not visible, but standard textbook diagram)

##### i. Coloring Instructions:
- Color the humerus (upper arm bone) one color (e.g., blue).
- Color the radius and ulna (forearm bones) another color (e.g., red).
- Color the carpals (wrist bones) a third color (e.g., green).
- Color the metacarpals and phalanges (hand bones) a fourth color (e.g., yellow).
- Then, apply the same colors to the corresponding bones in the whale, cat, bat, bird, and crocodile.
- Example: The whale’s flipper has the same basic bone pattern — humerus, radius/ulna, carpals, metacarpals, phalanges — just modified for swimming.

> 🔍 This shows that despite differences in function, these animals share a common ancestral limb structure.

##### ii. Describe at least two functions of each set of bones below:

| Animal | Functions |
|------------|-----------|
| Human | 1. Grasping objects<br>2. Manipulating tools and performing fine motor tasks |
| Whale | 1. Steering and propulsion in water<br>2. Maintaining balance while swimming |
| Cat | 1. Walking, running, and climbing<br>2. Catching prey and grooming |
| Bat | 1. Flight (wings formed by elongated fingers)<br>2. Hanging upside down from surfaces |
| Bird | 1. Flight (wings supported by fused bones and feathers)<br>2. Perching and preening |
| Crocodile | 1. Crawling and swimming<br>2. Lifting body off ground during movement |

> ✔ Note: All share the same basic skeletal layout, indicating shared ancestry.

##### iii. Are the bones arranged in a similar way in each animal?
→ Yes
*Explanation:* Despite differences in size, shape, and use, all these animals have the same fundamental arrangement of bones in their forelimbs: one large bone (humerus), two forearm bones (radius and ulna), wrist bones (carpals), hand bones (metacarpals), and finger bones (phalanges). This similarity in structure is evidence of common descent.

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What does the prefix "homo" mean?

→ "Same" or "similar"
*Explanation:* The term homologous comes from the Greek *homo-* meaning “same” or “equal,” and *logos* meaning “relation.” Homologous structures are those that are similar in origin and structure due to shared ancestry, even if their functions differ.

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✔ Summary of Key Concepts:

- Fossils show the sequence of life over time and support the idea of evolution through transitional forms.
- Homologous structures (like the pentadactyl limb) demonstrate shared ancestry among diverse species.
- These similarities in anatomy suggest that modern animals evolved from a common ancestor.
- Even though limbs serve different purposes (flying, swimming, walking), the underlying bone patterns are nearly identical — strong evidence for evolution.

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