❤️ 3.6 - 3.6.1 - 3.6.1.1 Survival and response (A-level only)

Question 1

Plants and animals respond to changes in their external environment to …

Answer 1

… increase their chances of survival

Question 2

Animals respond to changes in their internal environment to make sure that the conditions are always optimal for their …

Answer 2

… metabolism (all the chemical reactions that go on inside them).

Question 3

What is a stimulus?

Answer 3

Any change in the internal or external environment.

Question 4

Receptors detect …

Answer 4

stimuli.

They can be cells or proteins on cell surface membranes. There are lots of different types of receptors that detect different stimuli.

Question 5

Effectors produce a …

Answer 5

… response.

Effectors are cells that bring about a response to a stimulus to produce an effect. Effectors include muscle cells and cells found in glands, e.g. the pancreas.

Question 6

Receptors are …….. to one type of stimulus.

Answer 6

specific

Question 7

What do receptors communicate with effects via?

Answer 7

The nervous system or the hormonal system or both.

Question 8

What does the nervous system send information as?

Answer 8

Electrical impulses.

Question 9

The nervous system is made up of a complex network of cells called what?

Answer 9

neurones.

Question 10

What are the 3 main types of neurones?

Answer 10

Sensory neurones, motor neurones and relay neurones.

Question 11

What do sensory neurones transmit electrical impulses from and to?

Answer 11

From receptors to the central nervous system (CNS) - the brain and spinal cord.

Question 12

What do motor neurones transmit electrical impulses from and to?

Answer 12

From the central nervous system (CNS) to effectors.

Question 13

What do relay neurones transmit electrical impulses between?

Answer 13

Sensory neurons and motor neurones.

Question 14

What are electrical impulses also called?

Answer 14

Nerve impulses or action potentials.

Question 15

How does a stimulus make its way to an effector?

Answer 15

Stimulus – Receptors – sensory neurone– CNS –motor neurone– Effectors – Response.

Question 16

When a stimulus is detected by receptor cells an electrical impulse is then sent along what type of neurone?

Answer 16

Sensory neurone.

Question 17

When an electrical impulse reaches the end of a neurone, chemicals called neurotransmitters take the information across to the next neurone, which then sends what?

Answer 17

An electrical impulse.

Question 18

The CNS (the coordinator) processes the information and sends impulses along what type of neurones to an effector?

Answer 18

Motor neurones.

Question 19

What are the two different systems in which the nervous system is split into?

Answer 19

1) The central nervous system (CNS) - made up of the brain and the spinal cord.
2)The peripheral nervous system - made up of the neurones that connect the CNS to the rest of the body.

Question 20

What are the two different systems in which the peripheral nervous system is split into?

Answer 20

1) The somatic nervous system - controls conscious activities, e.g. running and playing video games.
2) The autonomic nervous system - controls unconscious activities, e.g. digestion.

Question 21

What are the two opposite effects in which the autonomic nervous system has on the body?

Answer 21

1) The sympathetic nervous system - gets the body ready for action (fight or flight system).
2) The parasympathetic nervous system - calms the body down (rest and digest system).

Question 22

What are reflexes?

Answer 22

The are rapid, automatic responses to stimuli.

Question 23

A reflex is …

Answer 23

… where the body responds to a stimulus without making a conscious decision to respond.

Question 24

Why are reflexes rapid?

Answer 24

Because you don’t have to spend time deciding how to respond, the information travels really fast from receptors to effectors.

Question 25

Because they are rapid, simple reflexes help to what?

Answer 25

Protect the body.

Question 26

What is a reflex arc?

Answer 26

The pathway of neurones linking receptors to effectors in a reflex.

Question 27

A simple reflex arc involving the 3 neurones (sensory, relay and motor) = The hand-withdrawal response to heat.

Answer 27

1) Thermoreceptors in the skin detect the heat stimulus. 2) The SN carries impulses to the RN. 3) The RN connects to the MN. 4) The MN sends impulses to the effector (your biceps muscle). 5) Your muscle contracts to withdraw your hand and stop it being damaged.

Question 28

If there is a relay neurone involved in the simple reflex arc, what is it possible to do?

Answer 28

Override the reflex, e.g. in the hand-withdrawal response to heat example, your brain could tell your hand to withstand the heat.

Question 29

What are three words you could use to describe nervous system communication?

Answer 29

Localised, short-lived and rapid.

Question 30

How is the nervous response localised?

Answer 30

When an electrical impulse reaches the end of a neurone, neurotransmitters are secreted directly onto target cells (e.g. muscle cells).

Question 31

How is the nervous response short-lived?

Answer 31

Neurotransmitters are quickly removed once they have done their job.

Question 32

How is the nervous response rapid?

Answer 32

Electrical impulses are really fast.

Question 33

Plants sense the direction of light and grow towards it to maximise light absorption for ...

Answer 33

... photosynthesis.

Question 34

Plants sense gravity, so the roots and shoots grow in the right ...

Answer 34

... direction.

Question 35

Climbing plants have a sense of touch, so they can find things to climb up and reach the ...

Answer 35

... sunlight.

Question 36

Tropism defintion.

Answer 36

A tropism is the response of a plant to a directional stimulus (a stimulus coming from a particular direction).

Question 37

How do plants respond to stimuli?

Answer 37

By regulating their growth.

Question 38

A positive tropism is growth ... the stimulus.

Answer 38

towards

Question 39

A negative tropism is growth ... from the stimulus.

Answer 39

away

Question 40

Phototropism defintion.

Answer 40

The growth of a plant in response to light.

Question 41

Are shoots positively phototropic and grow towards light?

Answer 41

Yes.

Question 42

Are roots negatively phototropic and grow away from light?

Answer 42

Yes.

Question 43

Gravitropism defintion.

Answer 43

The growth of a plant in response to gravity.

Question 44

Are shoots negatively gravitropic and grow upwards?

Answer 44

Yes.

Question 45

Are roots positively gravitropic and grow downwards?

Answer 45

Yes.

Question 46

How do plants respond to directional stimuli?

Answer 46

By using specific growth factors.

Question 47

What are growth factors in plants?

Answer 47

Hormone-like chemicals that speed up or slow down plant growth.

Question 48

What are growth factors in plants produced in?

Answer 48

The growing regions of the plant (e.g. shoot tips, leaves) and they more to where they are needed in the other parts of the plant.

Question 49

What is the name of a growth factor in plants, beginning with A?

Answer 49

Auxins.

Question 50

What do auxins stimulate and how?

Answer 50

They stimulate the growth of shoots by cell elongation (where the cell walls become loose and stretchy, so the cells get longer).

Question 51

What can high concentrations of auxins do?

Answer 51

Inhibit growth in roots of plants.

Question 52

What is the name of an important auxin?

Answer 52

Indoleacetic Acid (IAA).

Question 53

Where is IAA produced?

Answer 53

In the tips of shoots in flowering plants.

Question 54

What is IAA moved around the plant to control? How does it move?

Answer 54

Tropisms - it moves by diffusion and active transport over short distances, and via the phloem over long distances.

Question 55

What does different parts of the plant having different concentrations of IAA mean for the plant?

Answer 55

That there is an uneven distribution of IAA which means that there is uneven growth of the plant.

Question 56

In phototropism, IAA moves to the more shaded parts of the shoots and roots, so there is uneven growth. True or false?

Answer 56

True.

Question 57

In the shoot, IAA concentration increases on the shaded side - cells elongate and the shoot bends towards the ...

Answer 57

... light.

Question 58

In the root, IAA concentration increases on the shaded side - growth is inhibited so the root bends away from the ...

Answer 58

... light.

Question 59

In gravitropism, IAA moves to the underside of shoots and roots, so there is uneven growth. True or false?

Answer 59

True.

Question 60

In the shoot, IAA concentration increases on the lower side - cells elongate so the shoot grows ...

Answer 60

... upwards.

Question 61

In the root, IAA concentration increases on the lower side - growth is inhibited so the root grows ...

Answer 61

... downwards.

Question 62

What do simple responses keep simple organisms in?

Answer 62

A favourable environment.

Question 63

What are the two types of responses simple organisms can carry out to keep themselves in their favourable environment?

Answer 63

Tactic responses (taxes) or either kinetic responses (kinesis).

Question 64

What are tactic responses (taxes)?

Answer 64

The organisms move towards or away from a directional stimulus, e.g. light.

Question 65

What are kinetic responses (kinesis)?

Answer 65

The organisms movement is affected by a non-directional stimulus, e.g. humidity.

Question 66

What are tactic responses called?

Answer 66

Taxes.

Question 67

What are kinetic responses called?

Answer 67

Kinesis.