14.1- SURVIVAL AND RESPONSE

Question 1

What is a stimulus?

Answer 1

detectable change in the internal or external environment of an organisms that leads to a response in organisms

Question 2

What does being able to detect a stimuli allow you to do? (2)

Answer 2

move away from harmful stimuli, i.e. predators + extreme temps
detect + move towards source of food

Question 3

What do organisms that survive from danger have a greater chance of doing?

Answer 3

greater chance of raising offspring + passing their alleles to next generation

Question 4

What is there on organisms with more appropriate responses?

Answer 4

selection pressure favouring organisms with more appropriate responses

Question 5

What is a stimuli detected by?

Answer 5

receptors

Question 6

What are receptors specific to?

Answer 6

specific to one type of stimulus

Question 7

What does a coordinator do?

Answer 7

formulates suitable response to stimulus

Question 8

At what level can coordination be?

Answer 8

may be at molecular level or involve large organ i.e. brain

Question 9

What is a response produced by?

Answer 9

effector

Question 10

At what level can a response be?

Answer 10

may be at molecular level or involve behaviour of whole organism

Question 11

What is one means of communication in large. multicellular organisms?

Answer 11

occurs via chemicals called hormones, which is relatively slow process found in animals + plants

Question 12

What other communication, other than hormonal communication do animals have?

Answer 12

nervous system

Question 13

How fast is the response of the nervous system in comparison to hormonal communication?

Answer 13

more rapid

Question 14

What is each receptor + effector linked to?

Answer 14

central coordinator

Question 15

What does the coordinator connect?

Answer 15

info from receptor with appropriate effecter

Question 16

What is the sequence of events that can involve either chemical control or nerve cells?

Answer 16

stimulus -> receptor -> coordinator -> effector -> response

Question 17

What is a taxis?

Answer 17

simple response whose direction determined by direction of stimulus

Question 18

How do motile organisms respond to environmental changes?

Answer 18

respond directly to environmental changes by moving its whole body either towards favourable stimulus or away from unfavourable one

Question 19

How are taxes classified according to?

Answer 19

according to whether movement towards stimulus (positive taxis) or away from stimulus (negative taxis) + by nature of stimulus

Question 20

What phototaxis is it when single-celled algae moves towards light?

Answer 20

positive phototaxis

Question 21

Why would single-celled algae move towards light?

Answer 21

as it increase their changes of survival since, being photosynthetic, they require light to manufacture their food

Question 22

What phototaxis is it when earthworms move away from light?

Answer 22

negative phototaxis

Question 23

Why would earthworms move away from light?

Answer 23

as it increases their chance of survival as it takes them into the soil, where they’re better able to conserve water, find food + avoid some predators

Question 24

What chemotaxis is it when some species of bacteria move towards a region where glucose is more highly concentrated?

Answer 24

positive chemotaxis

Question 25

Why do some species of bacteria move towards a region where glucose is more highly concentrated?

Answer 25

as this increases their chances of survival as they use glucose as s source of food

Question 26

What is a kinesis?

Answer 26

changes speed at which it moves + rate at which it changes direction

Question 27

How does the rate of turning change when an organism crosses a sharp dividing line between favourable + unfavourable environment?

Answer 27

rate of turning increases

Question 28

Why does an organism rate of turning increases when it crosses a sharp dividing line between favourable + unfavourable environment?

Answer 28

as it raises its chance of a quick return to a favourable environment

Question 29

How can the rate of turning change when an organism moves a considerable distance into an unfavourable environment?

Answer 29

rate of turning may slowly decrease so that it moves in long straight line before it turns, often very sharply

Question 30

When is kinesis important?

Answer 30

when stimulus less directional

Question 31

What is a tropism?

Answer 31

growth of part of plant in response to directional stimulus

Question 32

What types of phototropism is it when plant shoots grow towards light?

Answer 32

positive phototropism

Question 33

What type of gravitropism is it when plant shoots grow away from gravity?

Answer 33

negative phototropism

Question 34

Why do plant shoots grow towards light + away from gravity?

Answer 34

so their leaves are in most favourable position to capture light for photosynthesis

Question 35

What type of phototropism is it when plant roots grow away from light?

Answer 35

negative phototropism

Question 36

What type of gravitropism is it when plant roots grow towards gravity?

Answer 36

positive gravitropism

Question 37

Why do plant roots grow away from light + towards gravity?

Answer 37

response increases probability that roots will grow into soil, where they’re better able to absorb water + mineral ions