Tropic responses

21
© Boardworks Ltd 2004 1 of 20 © Boardworks Ltd 2004 1 of 35 KS4 Biology Tropic Responses

description

KS4 Biology

Transcript of Tropic responses

Page 1: Tropic responses

© Boardworks Ltd 20041 of 20 © Boardworks Ltd 20041 of 35

KS4 Biology

Tropic Responses

Page 2: Tropic responses

© Boardworks Ltd 20041 of 20 © Boardworks Ltd 20042 of 35

Plant Responses

Response to light

Response to gravity

Contents

What do plants respond to?

Summary quiz

Page 3: Tropic responses

© Boardworks Ltd 20041 of 20 © Boardworks Ltd 20043 of 35

Which way up?

How do plants always grow the right way up?

What conditions will affect how a plant grows?

Page 4: Tropic responses

© Boardworks Ltd 20041 of 20 © Boardworks Ltd 20044 of 35

What do plants respond to?

Plants are very sensitive and their growth is affected by their environmental conditions.

A condition that affects plant growth is called a stimulus.

What are the three types of stimuli that plants respond to?

light

water

gravity

Page 5: Tropic responses

© Boardworks Ltd 20041 of 20 © Boardworks Ltd 20045 of 35

What is a tropism?

Plants respond to stimuli by growing to or away from them.

Movement towards a stimulus is called a positive tropism.

What is a movement away from a stimulus called?

A growth movement in response to a stimulus is a tropism.

light

water

gravity

A negative tropism.

Page 6: Tropic responses

© Boardworks Ltd 20041 of 20 © Boardworks Ltd 20046 of 35

Different types of tropism

Plant responses to light, water and gravity are givenspecial names.

Can you work out what the name of each tropism means?

water

gravity

light

hydrotropism

geotropism

phototropism

Which parts of a plant respond to these different stimuli?

Page 7: Tropic responses

© Boardworks Ltd 20041 of 20 © Boardworks Ltd 20047 of 35

What do different tropisms mean?

Page 8: Tropic responses

© Boardworks Ltd 20041 of 20 © Boardworks Ltd 20048 of 35

Plant Responses

Response to light

Response to gravity

Summary quiz

What do plants respond to?

Contents

Page 9: Tropic responses

© Boardworks Ltd 20041 of 20 © Boardworks Ltd 20049 of 35

How do plants respond to light?

A plant’s response to light is called phototropism.

Is phototropism a positive or negative tropism?

light

Plants grow towards light, which is a positive tropism.

Why do plants grow towards light?

Plants need light for photosynthesis, so they respond to light by growing towards it.

Page 10: Tropic responses

© Boardworks Ltd 20041 of 20 © Boardworks Ltd 200410 of 35

Phototropism and auxins

Which part of a plant is involved in phototropism?

Auxins are made in the tip of a growing shoot and move down the stem.

These plant hormones speed up growth in a growing shoot.

light

A growing shoot on a plant responds to light.

Page 11: Tropic responses

© Boardworks Ltd 20041 of 20 © Boardworks Ltd 200411 of 35

Phototropism and auxins – light from above

When a shoot gets light from above, the auxins produced at the tip are spread out evenly in the shoot.

How will this affect the growth of the shoot?

light

Page 12: Tropic responses

© Boardworks Ltd 20041 of 20 © Boardworks Ltd 200412 of 35

Phototropism and auxins – light from above

Why does a shoot grow straight up when light is from above?

There is an equal amount of auxins in all parts of the shoot, which grow at the same rate, so the shoot grows straight up.

light light

Page 13: Tropic responses

© Boardworks Ltd 20041 of 20 © Boardworks Ltd 200413 of 35

Phototropism and auxins – light from one side

When a shoot gets light from one side, the auxins are not evenly spread out in the shoot.

How will this affect the growth of the shoot?

light

Page 14: Tropic responses

© Boardworks Ltd 20041 of 20 © Boardworks Ltd 200414 of 35

Phototropism and auxins – light from one side

Why does the shoot bend towards the light when it gets light from one side?

There are more auxins on the shaded side of the shoot, so the shaded side grows faster making the bright side bend towards the light.

light light

Page 15: Tropic responses

© Boardworks Ltd 20041 of 20 © Boardworks Ltd 200415 of 35

Phototropism experiment

Page 16: Tropic responses

© Boardworks Ltd 20041 of 20 © Boardworks Ltd 200416 of 35

Plant Responses

Response to light

Response to gravity

Contents

Summary quiz

What do plants respond to?

Page 17: Tropic responses

© Boardworks Ltd 20041 of 20 © Boardworks Ltd 200417 of 35

How do plants respond to gravity?

A plant’s response to gravity is called a geotropism.

Different parts of a plant have different responses to gravity.

Are these responses positive or negative geotropisms?

Why is important that roots grow down into the soil?

gravity

shoots grow up

roots grow down

negative geotropism

positive geotropism

Page 18: Tropic responses

© Boardworks Ltd 20041 of 20 © Boardworks Ltd 200418 of 35

Geotropism and auxins

Auxins speed up growth in shoots and slow growth in roots.

If a plant is laid on its side, the auxins produced collect in the lower side of the root and stem.

How will the auxins affect the growth of the root and stem?

Page 19: Tropic responses

© Boardworks Ltd 20041 of 20 © Boardworks Ltd 200419 of 35

Geotropism and auxins

If a plant is laid on its side, why does the root grow down and the stem grow up?

Auxins slow down growth on the lower side of the root, so the root curves down.

Auxins speed up growth on the lower side of the stem, so the stem curves up.

Page 20: Tropic responses

© Boardworks Ltd 20041 of 20 © Boardworks Ltd 200420 of 35

Plant Responses

Response to light

Response to gravity

Plant hormones

Summary quiz

Contents

Page 21: Tropic responses

© Boardworks Ltd 20041 of 20 © Boardworks Ltd 200421 of 35

Multiple-choice quiz