Survival and response

Question 1

Q1: What is a stimulus?

Answer 1

A: A detectable change in the internal or external environment that produces a response.

Question 2

Q2: Define taxis.

Answer 2

A: A directional response to a stimulus

Question 3

Q3: What is kinesis?

Answer 3

A: A non-directional response where the speed of movement or turning increases in unfavorable conditions.

Question 4

Q4: What is a reflex arc?

Answer 4

A: The pathway of information in a reflex action: stimulus → receptor → sensory neuron → relay neuron → motor neuron → effector.

Question 5

Q5: What is the role of the autonomic nervous system?

Answer 5

A: Controls involuntary actions including heart rate and digestion.

Question 6

Q6: A plant grows toward light. Name and explain the type of response.

Answer 6

A: Phototropism: a directional growth response where auxins accumulate on the shaded side causing cell elongation and bending toward the light.

Question 7

Q7: Explain the advantage of positive gravitropism in roots.

Answer 7

A: Roots grow downward into the soil to access water and minerals and anchor the plant.

Question 8

Q8: Why do woodlice show kinesis in dry environments?

Answer 8

A: To increase movement and the likelihood of finding a favorable moist environment reducing water loss.

Question 9

Q9: A graph shows the response time for a reflex in different conditions. Suggest why response time is faster when a harmful stimulus is applied.

Answer 9

A: Harmful stimuli trigger faster responses due to direct pathways involving fewer synapses in the reflex arc.

Question 10

Q10: Data shows auxin concentration at different points on a shoot. Explain why the shaded side has more auxin.

Answer 10

A: Auxin redistributes to the shaded side of the shoot promoting cell elongation and bending toward light.

Question 11

Q11: Describe how coordination occurs in a simple reflex action.

Answer 11

A: Stimulus → receptor detects it → sensory neurons transmit impulses to the spinal cord → relay neurons connect to motor neurons → motor neurons carry impulses to effectors → response.

Question 12

Q12: Explain how IAA controls plant growth.

Answer 12

A: In shoots high IAA concentration promotes cell elongation. In roots

Question 13

Q13: Which part of the nervous system controls reflex actions?

Answer 13

A: The central nervous system (CNS).

Question 14

Q14: In which direction do auxins move in a plant?

Answer 14

A: Auxins move to the shaded or lower side in response to light and gravity.

Question 15

Q15: Compare and contrast taxis and kinesis.

Answer 15

A: Taxis is a directional response to a stimulus while kinesis is a non-directional response where movement rate depends on stimulus intensity.

Question 16

Q16: Explain the role of synapses in coordinating responses.

Answer 16

A: Synapses ensure one-way transmission of impulses and allow integration and filtering of signals.

Question 17

Q17: A shoot grows horizontally. Explain why its tip bends upward.

Answer 17

A: Gravity causes IAA to accumulate on the lower side promoting cell elongation there

Question 18

Q18: Why does severing a spinal cord disrupt reflex actions?

Answer 18

A: Reflex arcs rely on uninterrupted pathways within the spinal cord to transmit impulses.

Question 19

Q19: Describe the importance of reflex actions in animals.

Answer 19

A: Reflex actions are fast automatic responses that protect organisms from harm

Question 20

Q20: Explain why tropisms are beneficial for plant survival.

Answer 20

A: Tropisms ensure plants grow toward light (for photosynthesis) and roots grow into the soil (for stability and nutrient absorption).

Question 21

Q21: How would you design an experiment to investigate phototropism in seedlings?

Answer 21

A: Place seedlings in boxes with light entering from one side. Measure the angle of growth toward the light source. Use a control group with uniform light.

Question 22

Q22: Explain how you could use a choice chamber to investigate woodlice response to humidity.

Answer 22

A: Place woodlice in a chamber with dry and moist sections. Record their distribution over time. Conclude based on movement patterns.

Question 23

Q23: Explain why gravitropism is an advantage for seed germination.

Answer 23

A: Ensures roots grow downward into soil for water and minerals while shoots grow upward for light.

Question 24

Q24: A mutation prevents IAA redistribution in plants. Predict the effect on growth.

Answer 24

A: Plants would not exhibit directional growth responses like phototropism or gravitropism affecting their survival.

Question 25

Q25: Discuss the role of coordination in survival linking reflex actions to long-term responses like tropisms.

Answer 25

A: Reflex actions provide immediate protection from harm