# Biology Internal Assessment - investigate whether the Window and Notching caterpillar share the same ecological niche.

Biology Internal Assessment

DCP and CE

“Ecological Niches of Caterpillars”

2013

Design

Aim

To investigate whether the Window and Notching caterpillar share the same ecological niche.

Research Question

How does the shape of the feeding bite as measured by the distance from the midrib of the cabbage tree leaf to the nearest point of the feeding site indicate whether the Window and the Notching caterpillar share the same ecological niche?

Variables

Independent Variable –

Shape of feeding site

Range: Window or Notch

Dependant Variable

The distance from the midrib of the cabbage tree leaf to the nearest point of the feeding site.

Results

Raw Data Table showing the distance from the midrib of the cabbage tree leaf to the nearest point of the feeding site (mm) of 50 samples from notched and window shaped feeding sites on cabbage tree leaves.

Observations:

- Notches were mostly at the edges of leaves but were quite deep.
- Sometimes notches didn’t go to the very end of leaves.
- Windows were very long and didn’t go completely through the leaf.
- The cabbage tree leaves taper off significantly.
- The midrib is difficult to see.
- There were some yellow spots on the leaves.

Processed Data Table showing the mean distance from the midrib of the cabbage tree leaf to the nearest point of the feeding site (mm) of 50 samples from notched and window shaped feeding sites on cabbage tree leaves and the standard deviation.

Note: Processed data was put to the same number of decimal places as raw data

Calculations:

From:

From:

A T Test has been conducted to determine whether there is a marked difference in distance from the midrib of the cabbage tree leaf to the nearest point of the notched and window feeding site.

Null hypothesis: there is no significant statistical difference between distance from the midrib of the cabbage tree leaf to the nearest point of the notched and window feeding site.

Alternative hypothesis: there is a significant statistical difference between distance from the midrib of the cabbage tree leaf to the nearest point of the notched and window feeding site.

Calculating the degrees of freedom:

(sample size) – (the number of samples) = degrees of freedom

50+50 – 2 = 98

df= 98

The critical t value is obtained from the tables using the p value of 0.05. As the table does not include our df value of 98. We round our df value to the nearest value on the table which is 120.

Therefore critical t value is 1.98 or 2 (same number of decimal places as raw data)

Table from:

From:

Calculated t value = 5 (same number of decimal places as raw data)

Critical t value = 2

Our calculated t value of 5 is greater than the critical t value of 2. Therefore my null hypothesis that there is no significant statistical difference between distance from the midrib of the cabbage tree leaf to the nearest point of the notched and window feeding site can be rejected and the alternative hypothesis that there is a significant statistical difference between distance from the midrib of the cabbage tree leaf to the nearest point of the notched and window feeding site can be accepted. Meaning I am 95% certain that there is a significant difference between the two means, and therefore there is a significant difference in distance from the midrib of the cabbage tree leaf to the nearest point of the feeding site from notched and window shaped feeding sites on cabbage tree leaves.