10th grade ecosystems and food chains

Example

Five 1 m² quadrats contained these numbers of daisies: 7, 4, 11, 4, 10. What is the mean number of daisies per quadrat?

1. (7 + 4 + 11 + 4 + 10) ÷ 5 = 7.2
2. So the answer is: 7.2

Answer: 7.2

Example

A survey found 200 breeding pairs of a bird species in 2010 and 180 in 2024. What was the percentage decrease?

1. 200 − 180 = 20
2. 20 ÷ 200 × 100 = 10
3. So the answer is: 10 %

Answer: 10 %

Example

A bag of grass clippings had a mass of 200 g. After 10 days in a compost bin its mass was 180 g. What was the mean rate of decay, in g per day?

1. 200 − 180 = 20 g
2. 20 ÷ 10 = 2
3. So the answer is: 2

Answer: 2