14.1: Survival and response

Question 1

Stimulus

Answer 1

Detectable change in the internal or external environment of an organism that leads to a response in the organism

Question 2

Ability to respond to stimuli…

Answer 2

characteristic of life and increases the chance of survival of an organism

Question 3

Selection pressure in relation to stimuli

Answer 3

selection pressure favours organisms with better or more appropriate responses to stimuli

Question 4

Receptors

Answer 4

detect stimuli, are specific to one type of stimulus

Question 5

Coordinator

Answer 5

Formulates a suitable response to stimuli.

Question 6

Effector

Answer 6

produces a response

Question 7

Hormonal communication

Answer 7

relatively slow process in animals and plants via chemicals

Question 8

Nervous system

in comparison to hormonal communication

Answer 8

More rapid form of communication and only in animals

Question 9

Each effector and receptor are linked to

Answer 9

a central coordinator

Question 10

Central coordinator

Answer 10

Acts as a switchboard connecting information with the appropriate responses

Question 11

Sequence of events of nerve cells or chemical control order

5

Answer 11

stimulus > receptor > coordinator > effector > response

Question 12

Taxis

Answer 12

Simple response whose direction is determined by the direction of the stimulus

Question 13

How are taxes classified

Answer 13

According to whether the movement is towards the stimulus (positive stimulus) or away from the stimulus (negative taxis) and by the nature of the stimulus

Question 14

Example of negative phototaxis

Answer 14

earthworms that move away from light

Question 15

Kinesis

Answer 15

Form of response in which the organism doesn’t move towards or away from the stimulus, instead it changes the speed that it moves and the rate that changes direction

Question 16

Kinesis

what happens if an organism crosses a sharp dividing line between favourable and unfavourable environments

Answer 16

its rate of turning increases which increases its chance of a quick return to a favourable environment

Question 17

Kinesis
what happens if an organism a considerable distance into an unfavourable environment
important when?

Answer 17

• it will decrease its rate of turning and may continue in the same direction and then make a sharp, this makes it more likely it’ll come across a more favourable environment
• important when conditions are less of a gradient

Question 18

Examples of conditions that may have less of a gradient

2

Answer 18

humidity and temperature

Question 19

Tropism

Answer 19

The growth of part of a plant in response to a directional stimulus