Relationship between Water Flow and Animal

Size

Variables

Control variables: Water depth, river bed substrate composition, light intensity, water temperature

Independent variable : Water flow rate

Dependent variables: Animal species(size of animals), abundance of individuals, adaptions of water flow

Hypothesis

Animals with larger size can rarely adapt high water flow rate due to larger surface area to volume ratio.

Materials

Water flow meter

Light meter

Digital thermometer

Brush pen

Quadrat

Metal sieve

Measuring tape

Forceps

Plastic sorting tray

Methods

1, Select four localities with different flow rate by using flow meter.

2, Set a quadrat at each localities

3, Measure the light intensity, water depth, and water temperature, make sure they are similar.

4, count the abundance of different species

Results

Flow rate (m/s)

0 0.02 0.1 0.12

Water penny

0 0 1 3

Stonefly

nymph1 0 3 1

stream snail

11 (large)

36(large)

1 40

Predace-ous

chub7 0 0 0

Analysis

Most animals found in high water flow rate are smaller in size, including large stream snail, stonefly nymph and water penny.

Larger animals (predaceous chub) are found in slow water flow rate quadrat.

Discussion

The larger sizes of animals, the larger surface area to volume ratios. They are easily washed away at high water flow rate. They cannot withstand large water current and vice versa.

Summary

The hypothesis can be supported by results.

So, in slow water flow there are more animals with relatively larger size.

The end