Coordination, Response & Homeostasis (Cambridge (CIE) IGCSE Biology)

2,4-D is a synthetic plant auxin that is used as a weedkiller.

Researchers investigated the effectiveness of different treatments of 2,4-D on the control of the weed Conyza canadensis in fields of maize, Zea mays.

The results are shown in Table 1.

Table 1

Maize farmers that had been using treatment C were advised by the researchers to change to treatment F.

Discuss the advantages and disadvantages of changing to treatment F.

Auxin causes the shoots of a plant to grow away from gravity.

State the name of this response.

Extended only

Cells just behind a shoot tip absorb water and grow in length. A plant hormone stimulates cell elongation and controls the response of stems to gravity.

(i)

State the name of the plant hormone that stimulates cell elongation in stems.

[1]

(ii)

Explain how the response of stems to gravity is controlled.

[4]

Define the term sensitivity.

Fig. 1 shows the reflex arc involved in a simple reflex action.

Fig. 1

On Fig. 1, use label lines to identify and name the three types of neurone shown. 

A reflex is an involuntary action.

Explain what is meant by the term involuntary action.

Extended only

(i)

Define the term synapse.

[1]

(ii)

Describe how impulses are transmitted across a synapse.

[3]

Extended only

When a body senses danger, more adrenaline is secreted from the adrenal glands.

Describe two ways in which the hormone adrenaline affects the body in preparation for action.

State one difference between nervous and hormonal control systems.

This question is about neurones and reflex actions.

Choose words from the list to complete the sentences.

Each word may be used once, more than once, or not at all.

endocrine                      fast                           impulses

motor                       nervous                         receptor                       sensory

slow                        stimuli                         synapses

Neurones are cells that are part of the (i)............................................... system.

There are three types of neurone involved in a simple reflex action: a sensory neurone, a relay neurone and a (ii)............................................... neurone.

The nerves conduct electrical (iii)............................................... . These are transmitted from one neurone to the next at junctions called (iv)............................................... . 

A reflex action is automatic, co-ordinated and (v)............................................... .

The eye is a sense organ that responds to light.

Fig. 1 is a diagram of a section through the human eye.

Fig. 1

Table 1 describes some of the functions of the parts of the eye.

Complete the table by:

• Naming the parts of the eye

• Using the letters on Fig. 1 to identify the parts of the eye.

Table 1

Extended only

(i)

A pair of muscles in the eye work in opposition to each other to adjust the amount of light entering the pupil.

State the term that describes the action of a pair of muscles working in opposition to each other.

[1]

(ii)

A different pair of muscles in the eye work in opposition to each other to view objects at different distances from the eye.

State the name of the process that allows the eye to view objects at different distances. 

[1]

Extended Only

Explain why the eye cannot easily identify different colours in low levels of light. 

Extended only

Complete the five sentences about the eye and the nervous system.

Structures in the eye change the shape of the lens so that the eye can focus on near and distant objects. This is called ............................................... .

The radial and circular muscles in the iris of the eye are a pair of .............................................. muscles that work against each other.

Muscles in the eye are controlled by the nervous system.

The .............................................. nervous system contains only sensory and motor neurones.

The .............................................. nerve from the eye contains sensory neurones that conduct impulses to the ............................................... .

Extended only

Transmission of impulses relies on the flow of ions through the cell membranes of neurones down their concentration gradients. Active transport is responsible for maintaining the concentration gradients of ions across the membranes of neurones.

Explain how ions are moved across membranes by active transport.

Extended only

Fig. 1 shows the junction between two neurones.

Fig. 1

Many drugs interfere with the action of neurotransmitters at the junctions between neurones.

Two drugs that influence the transmission of impulses between neurones are atropine and eserine. The actions of these drugs are shown in Table 1.

Table 1

Explain the effects of these two drugs on the nervous system using the information in Fig. 1 and Table 1.

Insulin is a hormone that regulates the concentration of glucose in the blood.

Describe what is meant by the term hormone.

Extended only

Person A and person B were monitored to see how well they could control their blood glucose concentration.

They did not eat or drink anything other than water for eight hours before the monitoring began. They then drank a glucose solution.

Blood samples were taken at 30-minute intervals.

The blood samples were tested for glucose concentration.

The results are shown in Fig. 1.

Fig. 1

(i)

Calculate the percentage increase in the blood glucose concentration in person A between 60 and 90 minutes.

Give your answer as a percentage and to the nearest whole number.

[3]

(ii)

Using Fig. 1, compare the response of person A with the response of person B after the ingestion of glucose.

[3]

(iii)

Using Fig. 1, explain the response of person B after 90 minutes.

[4]

(iv)

Person A had Type 1 diabetes.

Outline the treatment of Type 1 diabetes.

[2]

Extended only

Fig. 1 shows the path of light entering the front part of the eye of a person with normal vision, whilst looking at a close object.

Fig. 1

As people get older (typically 40+), their lenses lose flexibility and can't spring back into a round shape when looking at close objects.

Explain what effect a less flexible lens would have on the path of light. 

Extended only

Explain the changes that occur in the normal human eye to focus on near and distant objects.

Extended only

Fig. 2 shows the light path into the eye of a person with normal vision and into that of a person with long-sightedness. 

Sufferers of long-sightedness are not able to see nearby objects clearly e.g. when reading, although this can be corrected using glasses.

Fig. 2

Use the diagrams in Fig. 2 to explain why people with long-sightedness cannot see nearby objects clearly. 

Extended only

As people age, their vision tends to deteriorate.

The majority of adults choose to wear glasses to correct their vision as shown in Fig. 3.

Fig. 3

The data in Fig. 3 was gathered from a survey of 4500 people.

Calculate the difference between the number of people needing no vision correction and the people who chose to use contact lenses. 

Extended only

The flow of blood through the skin can be investigated by using a flow-meter.

Fig. 1 shows a flow-meter above a section through the skin.

Fig. 1

(i)

State the name of cell P.

[1]

(ii)

State the types of blood vessel labelled Q, S and T.

[3]

(iii)

State the name of the tissue at R that provides insulation.

[1]

Extended only

The blood flow through the skin of some volunteers was measured with a flow-meter when their skin was exposed to different temperatures.

Capsaicin is a compound that gives people the sensation of feeling hot when it is put on the skin. Researchers applied capsaicin to the skin of the volunteers and again measured the blood flow through their skin at different temperatures.

Fig. 2 shows the results.

Fig. 2

(i)

Use the information in Fig. 2 to describe the effect of increasing the temperature of the skin surface on blood flow to the skin without capsaicin.

[3]

(ii)

Explain the mechanism that increases blood flow through the skin.

[3]

(iii)

State the difference between the average blood flow for the treatments (with and without capsaicin) at 35°C.

Space for working.

__________% [1]

(iv)

The researchers thought that capsaicin stimulated receptors in the skin.

Explain the process by which capsaicin could reach these receptors.

[3]

Extended only

Explain the importance of regulating body temperature in humans.

Body temperature is controlled by both hormones and nerves. 

Explain how coordination by hormones differs from coordination by nerves.