Survival and response (BIOL5)

Question 1

How do organisms increase chances of survival?

(For this unit!)

Answer 1

Respond to changes in their environment

Question 2

Define tropisms

Answer 2

Plants’ response to directional stimulus

Question 3

Describe tropisms

Answer 3

• Positive - growth towards stimulus
• Negative - growth away from stimulus
• Phototropism - in response to light
• Geotropism - in response to gravity

Question 4

Define taxes

Answer 4

Organisms move away from/towards directional stimulus

Question 5

Define kineses

Answer 5

Organisms movement affected by non-directional stimulus (e.g. intensity)

Question 6

Define reflex

Answer 6

Body’s response to stimuli without making a conscious decision

Question 7

Describe the reflex arc in a hand’s response to heat

Answer 7

Pathway of neurones linking receptors to effectors in reflex is the reflex arc

• Thermoreceptors detect heat stimulus
• Sensory neurone carries impulse to relay neurone
• Relay neurone sends impulses to motor neurone
• Motor neurone sends impulse to effector
• Muscle contracts to prevent damage If relay neurone involved, can override the reflex

Question 8

Features of growth factors in plants

Answer 8

• Respond to stimulus using growth factors
  
  • chemicals that speed up/slow growth
• Made in growing regions
• Gibberellim stimulates flowering/seed germination
• Auxin stimulate growth of shoots by cell elongation - where cell walls become loose/stretchy so cells get longer
• H conc auxins inhibit growth in roots!

Question 9

Features of indoleacetic acid (IAA)

Answer 9

• Auxin made in tips/roots
• IAA moves around plant to control tropisms
  
  • move by diffusion/active transport over short distances
  • move by phloem in long distance
• Results in diff parts having diff amnts IAA
  
  • uneven distribution means uneven growth
• Phototropism - IAA in shaded parts of roots/shoots
• Geotropism - IAA moves to underside of shoots/roots