Table of Contents
IGCSE Biology: Homework Answers #
Question 1 #
What is the main source of energy for biological systems?
Answer: The Sun
The Sun is the main source of energy for most biological systems. Light energy from the Sun is captured by plants during photosynthesis and converted into chemical energy stored in glucose. This energy then flows through food chains and food webs to all other living organisms.
Question 2 #
Draw a food chain with organisms, indicate the trophic level on each one
Example Food Chain:
Grass → Grasshopper → Frog → Snake → Hawk
Trophic Level 1 → Trophic Level 2 → Trophic Level 3 → Trophic Level 4 → Trophic Level 5
Trophic Level 1 → Trophic Level 2 → Trophic Level 3 → Trophic Level 4 → Trophic Level 5
Question 3 #
Define a food chain and food web
Food Chain:
Food Web:
A food chain is a diagram that shows the transfer of energy from one organism to another in a single pathway. It shows what eats what in a simple linear sequence. Energy flows in one direction through the food chain, from producers to consumers.
Food Web:
A food web is a diagram that shows how multiple food chains are linked together in an ecosystem. It shows all the feeding relationships between different organisms. A food web is more realistic than a food chain because most animals eat more than one type of food and can be eaten by more than one type of predator.
Question 4 #
What is a target organ (hormones)?
A target organ is the specific organ in the body that a hormone affects. Hormones travel in the blood to reach their target organs and cause a change in how that organ works.
Example: Insulin is produced by the pancreas and its target organs are the liver and muscles.
Question 5 #
Suggest a situation in which the secretion of adrenaline is increased
Example situation:
When a person is suddenly frightened by a dangerous animal or is in a dangerous situation, the adrenal glands release more adrenaline into the blood.
Question 6 #
Explain how adrenaline prepares the body for action
Adrenaline prepares the body for action by:
Heart rate: Adrenaline increases heart rate to pump blood faster and deliver more oxygen and glucose to muscles.
Breathing rate: Adrenaline increases breathing rate to take in more oxygen for respiration in muscles.
Blood glucose levels: Adrenaline increases blood glucose concentration by converting stored glycogen in the liver to glucose for more energy.
Breathing rate: Adrenaline increases breathing rate to take in more oxygen for respiration in muscles.
Blood glucose levels: Adrenaline increases blood glucose concentration by converting stored glycogen in the liver to glucose for more energy.
Question 7 #
State any 4 ways in which the endocrine system is different from the nervous system
Four differences between the endocrine system and nervous system:
1. Method of communication: The nervous system uses electrical impulses along neurones, while the endocrine system uses chemical hormones carried in the blood.
2. Speed of action: The nervous system produces a very fast response, while the endocrine system produces a slower response.
3. Duration of effect: The nervous system has short-lasting effects, while the endocrine system has long-lasting effects.
4. Area of effect: The nervous system acts on specific target cells through nerve pathways, while the endocrine system sends hormones throughout the body but only affects organs with the correct receptors.
2. Speed of action: The nervous system produces a very fast response, while the endocrine system produces a slower response.
3. Duration of effect: The nervous system has short-lasting effects, while the endocrine system has long-lasting effects.
4. Area of effect: The nervous system acts on specific target cells through nerve pathways, while the endocrine system sends hormones throughout the body but only affects organs with the correct receptors.
