Table of Contents
IGCSE Biology: Mammalian Hormones – Answer Key #
SECTION A: MULTIPLE CHOICE ANSWERS (20 marks) #
1. What is a hormone?
Answer: B – A chemical substance that acts as a messenger in the body
Hormones are chemical substances, not electrical signals (A), blood cells (C), or muscles (D). They act as chemical messengers that coordinate body functions.
2. Which of the following best describes how hormones travel around the body?
Answer: C – Through the bloodstream
Hormones are carried by the blood to reach their target organs. They do not travel through nerves, digestive system, or respiratory system.
3. Which gland produces the hormone adrenaline?
Answer: C – Adrenal glands
The adrenal glands produce adrenaline. The pancreas produces insulin and glucagon, the pituitary gland produces FSH and LH.
4. Where are the adrenal glands located in the body?
Answer: B – On top of the kidneys
The adrenal glands sit on top of both kidneys. The pituitary gland is in the brain, the pancreas is behind the stomach.
5. Which two hormones are produced by the pancreas?
Answer: B – Insulin and glucagon
The pancreas produces insulin and glucagon to control blood glucose levels. The other hormone pairs are produced by different glands.
6. What is the main function of insulin?
Answer: C – To lower blood glucose levels
Insulin helps cells absorb glucose from the blood, which lowers blood glucose levels. The other functions belong to different hormones.
7. Which hormone has the primary role in raising blood glucose levels during normal metabolism?
Answer: B – Glucagon
Glucagon is the primary hormone for raising blood glucose during normal metabolism by causing the liver to convert stored glycogen to glucose. While adrenaline also raises blood glucose, it does so specifically during emergency situations.
8. The pituitary gland is often called the “master gland” because it:
Answer: B – Controls many other glands in the body
The pituitary gland is called the “master gland” because its hormones control the activity of many other endocrine glands in the body.
9. Which hormones are produced by the pituitary gland?
Answer: C – FSH and LH
The pituitary gland produces FSH (Follicle-Stimulating Hormone) and LH (Luteinising Hormone), which control reproductive processes.
10. What does FSH stand for?
Answer: B – Follicle-Stimulating Hormone
FSH stands for Follicle-Stimulating Hormone. It stimulates egg development in ovaries and sperm production in testes.
11. Which hormone is responsible for male sexual development and characteristics?
Answer: C – Testosterone
Testosterone is the male sex hormone that controls male sexual development, including voice deepening, facial hair growth, and muscle development.
12. Which two hormones are produced by the ovaries?
Answer: D – Oestrogen and progesterone
The ovaries produce oestrogen and progesterone, which control female sexual development and the menstrual cycle.
13. What happens to your heart rate when adrenaline is released?
Answer: B – It increases
Adrenaline increases heart rate to pump blood faster, delivering more oxygen and glucose to muscles during emergencies.
14. Which of the following situations would most likely cause adrenaline to be released?
Answer: C – Watching a scary movie
Scary or exciting situations trigger adrenaline release as part of the “fight or flight” response. Peaceful activities do not trigger adrenaline.
15. Compared to nervous control, hormonal control is:
Answer: D – Slower acting and longer lasting
Hormonal control takes longer to start working because hormones must travel through the bloodstream, but the effects last longer than nerve impulses.
16. How do nerve impulses travel through the body?
Answer: B – As electrical signals through nerve fibers
The nervous system uses electrical impulses that travel through nerve fibers, while hormones use chemical signals through blood.
17. Which hormone helps maintain the uterus lining during pregnancy?
Answer: B – Progesterone
Progesterone maintains the uterus lining during pregnancy, while oestrogen prepares the lining during the menstrual cycle.
18. What does LH trigger in males?
Answer: B – Testosterone production
LH (Luteinising Hormone) triggers testosterone production in males. FSH triggers sperm production. Muscle development and voice deepening are caused by testosterone itself.
19. Why does adrenaline increase blood glucose concentration?
Answer: B – To provide extra energy for muscles during emergencies
During emergencies, muscles need extra energy to help you run away or fight. Higher blood glucose provides this extra fuel for muscle activity.
20. Which system provides more precise targeting of specific body parts?
Answer: B – The nervous system
The nervous system can target very specific locations where nerves end, while hormones affect all organs that have the right receptors throughout the body.
SECTION B: WRITTEN RESPONSE ANSWERS (30 marks) #
1. Define the term “hormone” and explain how hormones work as messengers in the body.
[4 marks]
Sample Answer:
A hormone is a chemical substance that acts as a messenger in the body (1 mark). Hormones are produced by endocrine glands and carried by the blood (1 mark). They travel through the bloodstream to reach specific target organs (1 mark). When hormones reach their target organs, they alter the activity of those organs by changing how they work (1 mark).
A hormone is a chemical substance that acts as a messenger in the body (1 mark). Hormones are produced by endocrine glands and carried by the blood (1 mark). They travel through the bloodstream to reach specific target organs (1 mark). When hormones reach their target organs, they alter the activity of those organs by changing how they work (1 mark).
Marking notes: Students need to mention that hormones are chemical substances, produced by glands, carried by blood, and alter organ activity.
2. Complete the table below about endocrine glands and their hormones:
[5 marks]
| Endocrine Gland | Hormone(s) Produced | Location in Body |
|---|---|---|
| Adrenal glands | Adrenaline | On top of the kidneys |
| Pancreas | Insulin and glucagon | Behind the stomach |
| Testes | Testosterone | In the scrotum |
Marking: 1 mark for each correct answer (5 total). Accept “above the kidneys” for adrenal location.
3. Explain what happens to the body when adrenaline is released. Include:
a) Two specific effects adrenaline has on the body [2 marks]
b) Why these effects are helpful during emergencies [3 marks]
Sample Answer:
a) Adrenaline increases blood glucose concentration (1 mark) and increases heart rate (1 mark).
b) Higher blood glucose provides extra energy/fuel for muscles (1 mark). Faster heart rate pumps blood more quickly around the body (1 mark), delivering oxygen and glucose to muscles faster so they can work more efficiently during emergencies (1 mark).
a) Adrenaline increases blood glucose concentration (1 mark) and increases heart rate (1 mark).
b) Higher blood glucose provides extra energy/fuel for muscles (1 mark). Faster heart rate pumps blood more quickly around the body (1 mark), delivering oxygen and glucose to muscles faster so they can work more efficiently during emergencies (1 mark).
Marking notes: For part (a), accept any two correct effects. For part (b), students must explain why each effect helps during emergencies.
4. Give three examples of situations that would cause adrenaline to be released and explain why each situation triggers this response.
[6 marks]
Sample Answer:
1. Being chased by a dangerous animal (1 mark) – this triggers adrenaline because the body needs to prepare for running away or fighting (1 mark).
2. Taking an important exam (1 mark) – this triggers adrenaline because the body recognizes this as a stressful situation that requires extra alertness and energy (1 mark).
3. Riding a roller coaster (1 mark) – this triggers adrenaline because the body perceives the fast movement and height as potentially dangerous, even though it’s safe (1 mark).
1. Being chased by a dangerous animal (1 mark) – this triggers adrenaline because the body needs to prepare for running away or fighting (1 mark).
2. Taking an important exam (1 mark) – this triggers adrenaline because the body recognizes this as a stressful situation that requires extra alertness and energy (1 mark).
3. Riding a roller coaster (1 mark) – this triggers adrenaline because the body perceives the fast movement and height as potentially dangerous, even though it’s safe (1 mark).
Marking: 1 mark for each situation, 1 mark for each explanation. Accept any appropriate dangerous, stressful, exciting, or surprising situations.
5. Compare nervous control and hormonal control by explaining the differences in:
[4 marks]
a) Speed of action
b) Duration of effect
c) Type of signal used
d) How signals travel through the body
b) Duration of effect
c) Type of signal used
d) How signals travel through the body
Sample Answer:
a) Speed of action: Nervous control is faster than hormonal control (1 mark)
b) Duration of effect: Nervous control lasts for a shorter time than hormonal control (1 mark)
c) Type of signal: Nervous control uses electrical signals while hormonal control uses chemical signals (1 mark)
d) How signals travel: Nervous signals travel through nerve fibers while hormonal signals travel through the bloodstream (1 mark)
a) Speed of action: Nervous control is faster than hormonal control (1 mark)
b) Duration of effect: Nervous control lasts for a shorter time than hormonal control (1 mark)
c) Type of signal: Nervous control uses electrical signals while hormonal control uses chemical signals (1 mark)
d) How signals travel: Nervous signals travel through nerve fibers while hormonal signals travel through the bloodstream (1 mark)
Marking: 1 mark for each correct comparison. Students must clearly show the difference between the two systems.
6. Explain the difference between insulin and glucagon in terms of their effects on blood glucose levels.
[4 marks]
Sample Answer:
Insulin lowers/decreases blood glucose levels (1 mark) by helping cells absorb glucose from the blood (1 mark). Glucagon raises/increases blood glucose levels (1 mark) by causing the liver to convert stored glycogen into glucose and release it into the blood (1 mark).
Insulin lowers/decreases blood glucose levels (1 mark) by helping cells absorb glucose from the blood (1 mark). Glucagon raises/increases blood glucose levels (1 mark) by causing the liver to convert stored glycogen into glucose and release it into the blood (1 mark).
Marking: Students must clearly state the opposite effects and explain how each hormone works.
7. A student is about to take an important exam and feels very nervous. Describe what is happening in their body in terms of hormone release and explain how this might actually help them perform better.
[4 marks]
Sample Answer:
The student’s adrenal glands are releasing adrenaline into their bloodstream (1 mark). This increases their heart rate and blood glucose concentration (1 mark). The faster heart rate delivers oxygen more quickly to the brain (1 mark), and the higher blood glucose provides extra energy for brain function, helping them think more clearly and stay alert during the exam (1 mark).
The student’s adrenal glands are releasing adrenaline into their bloodstream (1 mark). This increases their heart rate and blood glucose concentration (1 mark). The faster heart rate delivers oxygen more quickly to the brain (1 mark), and the higher blood glucose provides extra energy for brain function, helping them think more clearly and stay alert during the exam (1 mark).
Marking: Students must identify adrenaline release, its effects, and explain how these effects could help exam performance.
8. State the functions of the following hormones:
[4 marks]
Sample Answer:
a) FSH: Triggers egg development in ovaries / triggers sperm production in testes (1 mark)
b) LH: Triggers ovulation in females / triggers testosterone production in males (1 mark)
c) Testosterone: Controls male sexual development and characteristics (1 mark)
d) Oestrogen: Controls female sexual development / prepares uterus lining during menstrual cycle (1 mark)
a) FSH: Triggers egg development in ovaries / triggers sperm production in testes (1 mark)
b) LH: Triggers ovulation in females / triggers testosterone production in males (1 mark)
c) Testosterone: Controls male sexual development and characteristics (1 mark)
d) Oestrogen: Controls female sexual development / prepares uterus lining during menstrual cycle (1 mark)
Marking: 1 mark for each correct function. Accept any correct function for each hormone.
Total Marks: 50
Grade Boundaries (approximate):
A* = 45-50 marks (90-100%)
A = 40-44 marks (80-89%)
B = 35-39 marks (70-79%)
C = 30-34 marks (60-69%)
D = 25-29 marks (50-59%)
Grade Boundaries (approximate):
A* = 45-50 marks (90-100%)
A = 40-44 marks (80-89%)
B = 35-39 marks (70-79%)
C = 30-34 marks (60-69%)
D = 25-29 marks (50-59%)
