Question

This passage describes pelvic spines in threespine sticklebacks.

a threespine stickleback with pelvic spines
Threespine sticklebacks are small fish found in oceans or lakes. Some sticklebacks have sharp spikes called pelvic spines below their bodies.
Pelvic spines can protect sticklebacks from some predators. Large fish cannot swallow sticklebacks with spines. However, pelvic spines can actually make sticklebacks easier for other predators to catch. Some insects catch sticklebacks by grabbing their spines.
The table below describes a possible population of threespine sticklebacks at the start of a period of time and at the end of that period. The table shows the pelvic spines trait in the population at each point in time.
Complete the table. Write the exact answers as whole numbers or decimals.
Data about a population of threespine sticklebacks
Point in time Number with pelvic spines Number without pelvic spines Percentage with pelvic spines Percentage without pelvic spines
Start 54 446
%
%
End 29 696
%
%

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Answer 1

To fill out the table, we first need to calculate the percentages for the population of threespine sticklebacks at both the start and the end of the given periods.

### Start:
- **Number with pelvic spines:** 54
- **Number without pelvic spines:** 446
- **Total number of sticklebacks = Number with pelvic spines + Number without pelvic spines = 54 + 446 = 500**

#### Calculating Percentages at Start:
1. **Percentage with pelvic spines:**
\[
\text{Percentage with pelvic spines} = \left(\frac{\text{Number with pelvic spines}}{\text{Total number of sticklebacks}}\right) \times 100 = \left(\frac{54}{500}\right) \times 100 = 10.8\%
\]

2. **Percentage without pelvic spines:**
\[
\text{Percentage without pelvic spines} = \left(\frac{\text{Number without pelvic spines}}{\text{Total number of sticklebacks}}\right) \times 100 = \left(\frac{446}{500}\right) \times 100 = 89.2\%
\]

### End:
- **Number with pelvic spines:** 29
- **Number without pelvic spines:** 696
- **Total number of sticklebacks = Number with pelvic spines + Number without pelvic spines = 29 + 696 = 725**

#### Calculating Percentages at End:
1. **Percentage with pelvic spines:**
\[
\text{Percentage with pelvic spines} = \left(\frac{\text{Number with pelvic spines}}{\text{Total number of sticklebacks}}\right) \times 100 = \left(\frac{29}{725}\right) \times 100 \approx 4.0\%
\]

2. **Percentage without pelvic spines:**
\[
\text{Percentage without pelvic spines} = \left(\frac{\text{Number without pelvic spines}}{\text{Total number of sticklebacks}}\right) \times 100 = \left(\frac{696}{725}\right) \times 100 \approx 96.0\%
\]

### Completed Table:

| Point in time | Number with pelvic spines | Number without pelvic spines | Percentage with pelvic spines | Percentage without pelvic spines |
|---------------|---------------------------|------------------------------|-------------------------------|----------------------------------|
| Start | 54 | 446 | 10.8% | 89.2% |
| End | 29 | 696 | 4.0% | 96.0% |

### Summary of Answers:
- Percentage with pelvic spines (Start): 10.8%
- Percentage without pelvic spines (Start): 89.2%
- Percentage with pelvic spines (End): 4.0%
- Percentage without pelvic spines (End): 96.0%