Question
This passage describes shell shape in pond snails.
a narrow shell (left) and a round shell (right)
A pond snail's shell may be narrow or round. Each shape is better at protecting a snail against a different kind of predator.
A narrow shell provides better protection against crayfish, which attack a snail at the opening of its shell. Narrow shells have smaller openings, so they are harder for crayfish to attack.
A round shell provides better protection against carp, which crush shells with their teeth. Round shells are harder for carp to crush.
The table below describes a possible population of pond snails at the start of a period of time and at the end of that period. The table shows shell shape 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 pond snails
Point in time Number with narrow shells Number with round shells Percentage with narrow shells Percentage with round shells
Start 358 42
%
%
End 69 131
%
%
Answers
GPT-4o mini
To complete the table for the pond snail population, we need to calculate the percentages for each shell shape at both the start and end points in time.
1. **Calculating Percentages at the Start:**
- Total number of snails at the start = Number with narrow shells + Number with round shells
- Total number of snails at the start = 358 + 42 = 400
- Percentage with narrow shells = (Number with narrow shells / Total number of snails) × 100
- Percentage with narrow shells = (358 / 400) × 100 = 89.5%
- Percentage with round shells = (Number with round shells / Total number of snails) × 100
- Percentage with round shells = (42 / 400) × 100 = 10.5%
2. **Calculating Percentages at the End:**
- Total number of snails at the end = Number with narrow shells + Number with round shells
- Total number of snails at the end = 69 + 131 = 200
- Percentage with narrow shells = (Number with narrow shells / Total number of snails) × 100
- Percentage with narrow shells = (69 / 200) × 100 = 34.5%
- Percentage with round shells = (Number with round shells / Total number of snails) × 100
- Percentage with round shells = (131 / 200) × 100 = 65.5%
Now, we can fill in the table:
| Point in time | Number with narrow shells | Number with round shells | Percentage with narrow shells | Percentage with round shells |
|---------------|--------------------------|-------------------------|------------------------------|-----------------------------|
| Start | 358 | 42 | 89.5% | 10.5% |
| End | 69 | 131 | 34.5% | 65.5% |
1. **Calculating Percentages at the Start:**
- Total number of snails at the start = Number with narrow shells + Number with round shells
- Total number of snails at the start = 358 + 42 = 400
- Percentage with narrow shells = (Number with narrow shells / Total number of snails) × 100
- Percentage with narrow shells = (358 / 400) × 100 = 89.5%
- Percentage with round shells = (Number with round shells / Total number of snails) × 100
- Percentage with round shells = (42 / 400) × 100 = 10.5%
2. **Calculating Percentages at the End:**
- Total number of snails at the end = Number with narrow shells + Number with round shells
- Total number of snails at the end = 69 + 131 = 200
- Percentage with narrow shells = (Number with narrow shells / Total number of snails) × 100
- Percentage with narrow shells = (69 / 200) × 100 = 34.5%
- Percentage with round shells = (Number with round shells / Total number of snails) × 100
- Percentage with round shells = (131 / 200) × 100 = 65.5%
Now, we can fill in the table:
| Point in time | Number with narrow shells | Number with round shells | Percentage with narrow shells | Percentage with round shells |
|---------------|--------------------------|-------------------------|------------------------------|-----------------------------|
| Start | 358 | 42 | 89.5% | 10.5% |
| End | 69 | 131 | 34.5% | 65.5% |