B7: COORDINATION AND RESPONSE

7.1 Hormones

What is a hormone? A chemical substance Produced in an endocrine gland Carried in the blood Alters the activity of the target organ(s) Destroyed by the liver• Copy and complete this table using p152

fig12.6.1.• Do not use adrenaline as an exampleHormone Gland Action

hormones

Produced by the adrenal glands (above the kidneys) Prepares the body for action:

Adrenaline Effect on musclesAdrenal glands Fight or flight

Action Reason

Increases blood glucose level

for muscles to use to produce ATP energy for contraction

Increases heart rate to transport more glucose and oxygen to the muscle cells

Dilates airways so more air reaches alveoli for increased gas exchange

Dilates blood vessels in brain and muscles

to deliver more glucose and oxygen to these cells

Constricts blood vessels in gut and other organs

allowing blood to be diverted to muscles

B7: COORDINATION AND RESPONSE

7.2 Tropic responses

What is a tropism? Plants grow towards or away from stimuli The growth response is called a tropism

gravity

light

Shoots will grow towards light – a positive tropism

Shoots will grow against gravity – a negative tropism

The stimuli Phototropism is the growth response

towards or away from light Geotropism is the growth response with or

against gravity

geotropism

phototropism

Putting it all together: Complete this table:

Response Tropism

Shoots growing towards sunlight Positive phototropism

Shoots growing against gravity Negative geotropism

Roots growing away from sunlight Negative phototropism

Roots growing with gravity Positive geotropism

How do plants grow to the light?

A hormone called auxin is made in the tip of the shoot

Auxin causes shoot cells to enlarge

When light is directly overhead, auxin diffuses equally down the shoot

The shoot grows straight up

light

How do plants grow to the light?

When light is directional, the auxin moves to the shaded side of the shoot

The cells on the shaded side elongate more than the cells on the lighted side

The shoot grows towards the light

light

Auxin at work

Phototropism experiment

How do plants respond to gravity?

gravity

shoots grow up

roots grow down

negative geotropism

positive geotropism

How do plants respond to gravity? Auxin is made in the

shoot and root tips Auxin causes slowed

growth in root cells When a plant is laid on its

side, auxin collects in the lower cells

The lower cells in the shoot elongate and the shoot grows upwards

The lower cells in the root slow in growth and the roots grow downPhototropism and ge

otropism

Textbook Questions Complete the following summary

questions:P153 exercise 1P155 exercises 1, 2 and 3

Complete the following exam-style questions:P156 question 4