p2: survival and response

Question 1

stimulus:

Answer 1

detectable change in envionment, external or internal

Question 2

simple reaction pathway

Answer 2

stimulus > receptor > coordinator> effector> response

Question 3

why do organisms need to respond to changes in their environemnt?

Answer 3

• avoids competitiona nd predators
• keeps them in a favourable environment
• grow towards/away from stimuli
• disperse to find new stimuli

Question 4

behaviour patterns

Answer 4

• instinctive behaviour is an innate response to stimuli
• innate behaviour genetically determined, not learnt
• same response if same species

Question 5

kinesis

Answer 5

• behaviour pattern where animal responds to change in stimulus by increasing or decreasing activity
• change in rate of movement
• random movement, not directional

Question 6

taxes

Answer 6

• directional movement towards or away from a stimuli
• positive taxes: towards stimuli
  negative taxes: away from stimuli
• phototaxis: light
• chemotaxis: chemicals
• aerotaxis: oxygen
• geotaxis: gravity
  halotaxis: salt
  hydrotaxis: water

eg: earthworms move away from light
- more likely to find food
- more likely to avoid predators
- less likely to dehydrate

Question 7

reflec axtion

Answer 7

• short lived response
• rapid, dont have to be learnt
• protects agaisnt damage to body tissue
• helps escape from predators
• enable homeostasis
• find food

Question 8

explain the advantages of simple reflex arcs

Answer 8

• rapid
• protect body from damage to tissues
• dont ahve to be learned
• help escape predators
• enable homeostatic control

Question 9

plant growth factors

Answer 9

• synthesised throughout plant
• diffuse from growing regions to other tissues, to regulate growth
  eg: IAA, AUXINS

Question 10

IAA

Answer 10

• produced in tips of roots and shoots
• diffuses to growing region
• causes cell elongation in the shoots
• inhibits cell elongation in the roots
• transported to shaded parts of roots and shoots

Question 11

describe the effect of IAA on shoot growth in plants

Answer 11

• IAA synthesised in shoot tips
• IAA diffuses into growing regions
• light causes movement of IAA frpm light side to shaded side
• more IAA on shaded side than light side
• directional growth as greater cell elongation in shaded side
• shaded side grows faster and shoot bends towards light

Question 12

describe the effect of IAA on root growth

Answer 12

• IAA synthesised in root tips
• IAA diffuses into growing region
• IAA moves to shaded side
• inhibits cell elongation
• uneven growth, more elongation on side with less IAA
• directional growth away from light and downwards towards gravity

Question 13

describe what is meant by the term taxis

Answer 13

moves trowards or away from directional stimulus

Question 14

compare and contrast taxis and tropism

Answer 14

• both directional responses to a stimuli
• taxis moves whole organism whereas tropism is the movement of part of an organism