Explain why food chains generally consist of three or four steps.
Explain why food chains generally consist of three or four steps.
Solution
• Only 10% of the energy from one trophic level is transferred to the
next level. Most of the energy is lost as heat.
• So very little usable energy will remain after four trophic levels./
10% 10%
Grass → Grasshoper → Frog
(Producer ) (
Primary
) (
Secondary
)
1000k Cal. consumer 100k Cal. consumer 10k Cal.
(Any other suitable food chain)
12 (A)
• As his pancreatic duct is blocked, enzymes for digestion will not be
transported to small intestine / The blockage will cause difficulty in
digestion of proteins, carbohydrates and fats.
• Insulin secretion is already affected.
OR
(B)
• Reflex action
• An automatic and quick response to a stimulus which does not involve
thinking.
PAGE 3 {31-4-1}
• Stimulus → Receptor → sensory neuron → relay neuron (spinal cord)
→ Motor neuron → effector (muscle) response.