24.1 sensory reception N/C

Question 1

stimulus

Answer 1

• a detectable change in the internal or external environment of an organism that produces a response in the organism

Question 2

response

Answer 2

• as a result of the stimulus that is detected by the receptor a response is caused
• this may be movement of the organism or a change in behaviour

Question 3

advantages of sensitive response

Answer 3

• increases chances of sirvival for an organism; greater chance of reproducing offsprings that carry these alleles
• selection pressure favours these organisms

Question 4

what should organisms be able to respond to quickly

Answer 4

1) detect and move away from predators
2) detect and move away from extreme temperatures
3) detect and move towards needed resources; food, habitat and safety; that air survival

Question 5

receptors

Answer 5

• an organ or specialised cell that can detect the change that is causing the stimulus.

Question 6

how do receptors allow stimulus to be processed

Answer 6

• they transform energy of a stimulus into a form of energy that can be processed by the organism

Question 7

effectors

Answer 7

• range of different cells, molecules, tissues, organs and systems that carry out a response

Question 8

coordinator

Answer 8

• means of communication between receptors and effectors as sometimes they are some distance apart, which leads to a response
  e.g. the nervous system
  hormones

Question 9

coordinator in nervous system

Answer 9

• each receptor and effector is linked to a central coordinator
• coordinator connects information from each receptor with the appropriate effector

Question 10

sequence of events from stimulus to response

Answer 10

stimulus –> receptor –> coordinator –> effector –> response
- it involves either chemical control or nerve cells

Question 11

what three neurones are involved in a simple reflex arc

Answer 11

• motor neurones
• sensory neurones
• intermediate neurones

Question 12

why is response to stimulus in a simple reflex arc rapid

Answer 12

• distance between receptor and effector is relatively short

Question 13

why is a simple reflex arc innate

Answer 13

• it is a fixed pattern of response that is common to all members of that species of organism

Question 14

sequence of events from stimulus to response in a simple reflex arc

Answer 14

stimulus –> receptor –> sensory neurone –> intermediate neurone –> motor neurone –> effector –> response

Question 15

why is a simple reflex protective

Answer 15

• prevent damage by providing an immediate response

- it is involuntary

Question 16

common example of a simple reflex in humans

Answer 16

• blinking

Question 17

taxis

Answer 17

• a simple response whose direction is determined by the direction of the stimulus

Question 18

result taxis to a motile organism

Answer 18

• motile organisms responds directly by to environmental changes by either moving its whole body (or a part that detaches) TOWARDS a favourable stimulus or AWAY from unfavourable stimulus

Question 19

positive taxis

Answer 19

favourable stimulus

Question 20

negative taxis

Answer 20

unfavourable stimulus

Question 21

light taxis

Answer 21

phototaxis

Question 22

chemica taxis

Answer 22

chemotaxis

Question 23

example of positive phototaxis

Answer 23

• single called algae moving towards light to photosynthesise and make their own food

Question 24

example of negative phototaxis

Answer 24

• earthworms moving away from light to hide away from predators and to live within soil where water is plentiful

Question 25

examples of positive chemotaxis

Answer 25

• bacteria moving towards areas where there is a high concentration of glucose
• sharks moving towards areas where there is blood

Question 26

kinesis

Answer 26

• a form of response where an organism’s body is not oriented in relation to a sensory stimulus; rather, the stimulus causes an alteration in speed or direction of movement