Ecological pyramids and Laboratory work 2
Answers are for parents and teachers.
1
Chain: plankton → small fish → larger fish → seal. The seal’s dry mass is 15 kg. How many kg of plankton?
15000
2
Energy: plant 250 000 kJ. How many kJ in the secondary consumer (level 3)?
2500
3
Yield is 400 g/m² (dry). What area gives 2 000 000 g (dry) of plants?
5000
4
Why is a food chain not longer than 5–6 links? Explain with a calculation.
It decreases tenfold per link: at the 6th link energy is 10⁻⁵ of the start, too little to support life.
5
Why are top predatory birds harmed most by pesticides (DDT)?
Biomagnification: the poison accumulates in fat and its concentration rises along the chain; DDT thinned bird eggshells.