3.6.1.1 stimuli, both internal and external , and detected and lead to a response

Question 1

why organism have to response to change in there environment

Answer 1

increase their chance of survival
increasing the likelihood of reproducing
passing alleles on to the next generation

Question 2

simple response that can allow mobile organism maintain in favourable environment

Answer 2

taxis, kinesis

Question 3

stimulus definition

Answer 3

A stimulus is a detectable change in the internal / external environment of an organism that leads to a response.

Question 4

taxis

defintion
chracteristic
example
+ve / -ve

Answer 4

Movement of a motile organism in response to a stimulus (usually environmental changes)

• directional response

e.g. chemotaxis, phototaxis etc.

The direction of movement is determined by the direction of the stimulus
Positive taxes = organisms move towards a stimulus (usually favourable)
Negative taxes = organisms move away from a stimulus (usually unfavourable)

Question 5

kinesis

characteristic

Answer 5

• non-directional
• changes the speed at which it is moving and the rate at which it changes direction in response to a stimulus
• Movement is random

If it moves into an unfavourable environment then its rate of turning decreases so that it moves in long straight lines before turning (vise versa)

Question 6

chi square test

Answer 6

If the calculated 𝛘2 < table 𝛘2
Accept the Null hypothesis
Differences are just due to chance

If the calculated 𝛘2 > table 𝛘2
Reject the Null hypothesis

Question 7

compare and contrast taxis and kinesis

Answer 7

both involve movement in repond to stimuli
directional vs non directioncal (randondom) [whereas]

Question 8

tropism

definition
+ve / -ve

Answer 8

The growth of plants in response to a directional stimulus

The plant grows towards (positive response) or away (negative response) from a stimulus

Question 9

3 type of stmuli plants respond to

Answer 9

Light - phototropism (shoots positive)

Gravity - gravitropism (roots positive, shoots negative)

Water - positively hydrotropic

Question 10

IAA/ auxin effect on plant

Answer 10

• increasing the flexibility / stretchiness of plant cell walls
  = allowing cell elongation.
  (Cell elongation on one side only can lead to a shoot or root bending.) in shoot
• inhibit cell elongation in the root

Question 11

What causes the uneven IAA distribution?

(for ans experiment Q)

Answer 11

• Light inhibits IAA on illuminated side
• Light destroys IAA on illuminated side
• Light stimulates the movement of IAA to the shaded side

Question 12

gravitropism on shoot and root

Answer 12

shoot
- elongation
- bend up
- negative gravitropism

roots
- elongation inhibit
- ben down
- positive gravitropism

Question 13

cns and pns and neuron involve

Answer 13

The CNS processes information.
Sensory neurones carry messages (electrical impulses) from the peripheral sense organs to the CNS
Motor neurones send electrical impulses from the CNS to effector organs (muscles or glands.)

Question 14

definition of a stimulus

Answer 14

A stimulus is a change in the internal (inside organism) or external (outside organism) environment.

Question 15

definition of receptor

Answer 15

A receptor detects a stimulus. Receptor cells are specific to one type of stimulus.

Question 16

propose of receptor

Answer 16

An effector produces a response.

Question 17

voluntory and involuntory response (involve body structure)

Answer 17

Voluntary responses involve the brain (conscious thinking) and spinal cord

Involuntary responses occur without thinking and often involves the spinal cord

Question 18

purpose of reflex arc

Answer 18

• Involuntary actions
• protect the body from harm,
• increasing survival chances.