OCR A Level Biology

Topic Questions

A LevelBiologyOCRTopic Questions5. Communication, Homeostasis & Energy5.1 Communication & Homeostasis

5.1 Communication & Homeostasis

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1
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Which of the rows, A to D, shows the correct responses to the changes in the internal or external environment?

  Changes in the internal or external environment Responses
A Blood carbon dioxide concentration increases Breathing rate decreases
B High blood glucose concentration Pancreas releases insulin hormone
C Decrease in body temperature Hair erector muscles relax
D Increase in body temperature Vasoconstriction

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2
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Which of the following correctly describes cell signalling?

  • Signalling molecules are always hormones

  • Cell signalling involves communication between cells that are very close together and between cells that are very far apart

  • During cell signalling a stimulus is converted into a signal by effector cells

  • Cell signalling molecules have the same shape as the membrane receptors to which they bind

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3
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Which of the following is a correct definition of negative feedback?

  • Any change from the normal range of a factor is amplified

  • A receptor detects a stimulus and an effector brings about a response

  • Any change from the normal range of a factor is corrected to bring levels back within the normal range

  • Communication between cells to control and coordinate the response to changing environments

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4
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Which of the following is an example of thermoregulation in an ectotherm?

  •  Vasoconstriction

  • Basking in the sun

  • Consuming a large volume of food

  • Contraction of hair erector muscles

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5
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The graph below shows the body temperature of a student before, during and after performing a star jump workout.ocr-a-5-1e-mcq-q5-body-temperature-homeostasis

Which of the following statement(s) could explain the events shown in the graph?

1 At 2 mins, metabolic rate increases
2 After 6 mins, arterioles near the skin dilate to allow more blood flow to the skin surface
3 After 6 mins, hair erector muscles relax

  • 1, 2 and 3

  • Only 1 and 2

  • Only 2 and 3

  • Only 1

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1
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Which of the following is not a reason that communication systems are needed in multicellular organisms?

  • Maintaining internal conditions in the body within broad limits

  • Specialised cells, like red blood cells, perform a specific function

  • Carbon dioxide concentration in the blood needs to be controlled

  • Organisms need to detect and respond appropriately to stimuli

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2
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Which of the following correctly describes an example of cell signalling?

  • Beta cells in the pancreas release glucagon into the bloodstream, which then acts on liver cells

  • Lymphocytes release cytokines that acts on pathogens by binding to them

  • The posterior pituitary releases ADH into the blood. This acts on kidney cells

  • A neurotransmitter causes a postsynaptic cell membrane to become hyperpolarised by increasing the movement of sodium ions into the cell

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3
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Which of the following statements about the blood clotting cascade are correct?

1 Soluble fibrinogen is converted into insoluble fibrin
2 This is a positive feedback system.
3 Platelets work to reverse the change by decreasing the response.

  • 1, 2 and 3

  • Only 1 and 2

  • Only 2 and 3

  • Only 1

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4
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The graph represents the oxygen consumption rate of a weasel (a small mammal) over a range of external temperatures.

ocr-a-5-1h-mcq-q4-oxygen-consumption-rate Which statement about the graph is correct?

  • The temperature of the blood carrying oxygen through the hypothalamus increases at higher external temperatures.

  • Metabolic rate decreases with increasing external temperature

  • Internal body temperature decreases with decreasing oxygen consumption rate.

  • There is a 60 % decrease in oxygen consumption rate between 25 °C and 35 °C.

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5
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The image below shows a marine iguana.

Marine iguanas have evolved a range of strategies that enable them to keep warm during cold conditions in the Galapagos islands. 

Which of the following statements, A to D, correctly describes an aspect of iguana strategies for keeping warm?

  • Pressing their bodies against warm ground for heat transfer

  • Receptors in their hypothalamus help detect the temperature of their blood, resulting in internal changes such as the redirection of blood flow away from the skin

  • Temperature regulation is essential to allow enzyme-controlled reactions to occur at a suitable rate

  • Increased food consumption during winter to allow an increase in metabolism

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1
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Which of the options, A to D, correctly describes how an endotherm would respond to an increase in temperature?

  • dilation of arterioles near the surface of the skin

  • erector muscles contract, causing hairs to stand up

  • rapid contractions of skeletal muscles

  • sweat glands release less sweat

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2
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Fig. 11.1 shows the heat flow through the skin of an athlete during vigorous exercise.

Exercise starts at 400 seconds.

q11-paper-1-specimen-ocr-a-level-biology

Fig. 11.1

Blood flow can be directed to those parts of the body that make the greatest demands.

Which row gives the best explanation of the stages in Fig. 11.1?

  R S T
A Blood directed away from skin to avoid excess heat loss Blood directed towards skin to release excess heat Balance achieved between loss of excess heat and the need for oxygen in the muscles
B Blood directed away from skin and towards the muscles to supply more oxygen for respiration Blood directed towards skin to release excess heat Balance achieved between heat loss and excess heat created in the muscles
C Blood directed away from skin to avoid excess heat loss Blood directed towards skin to gain heat from the environment Balance achieved between heat loss and excess heat created in the muscles
D Blood directed away from skin and towards the muscles to supply more oxygen for respiration Blood directed towards skin to gain heat from the environment Balance achieved between loss of excess heat and the need for oxygen in the muscles

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3
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Which of the following is not a feature of the endocrine system?

  • It brings about instant responses in the body.

  • Glands secrete chemical substances into the blood.

  • It affects specific target organs.

  • It has a role in the maintenance of internal body conditions.

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4
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Which of the following statements correctly explain(s) why organisms need to be able to respond to change?

  1. Enzymes in the body can denature at low temperatures.
  2. Enzymes in the body can denature at extreme pH levels.
  3. Water will move in or out of body cells by osmosis at non-ideal blood glucose concentrations.
  4. Water vapour can build up inside leaves if the stomata do not open.

  • Only 1 and 2

  • Only 2

  • Only 2 and 3

  • Only 2, 3 and 4

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5
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The image below shows a general homeostatic mechanism.

image-5-1-m-q5

Which feature shown in the image indicates that this mechanism is a negative feedback loop?

  • Changes are detected by receptors.

  • The factor is returned to its normal range.

  • The factor deviates from its normal range.

  • The effect of the original stimulus is enhanced by mechanism A or mechanism B.

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The image below shows a summary of the homeostatic mechanism that regulates blood glucose.

Wu38Gk5-_negative-feedback-regulation-of-blood-glucose-levels

Which row in the table correctly identifies a receptor and an effector?

  Receptor Effector
A. Muscle cells Glucose
B. Pancreas cells Liver cells
C. Pancreas cells Insulin
D. Liver cells Blood glucose

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7
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Which of the following statements relating to cell signalling is not correct?

  • Signalling between distant cells is known as endocrine signalling.

  • Some signalling molecules can cross the cell surface membrane and bind to receptors inside cells.

  • The conversion of a signal to a stimulus is known as transduction.

  • Acetylcholine at a neuromuscular junction is an example of cell signalling.

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8
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Which of the rows in the table below correctly shows the sequence of events that occur during cell signalling?

A. Stimulus detected by a receptor Stimulus is converted to a signal Signal is detected by an effector A response occurs
B. A deviation from the normal level occurs This deviation is detected by a receptor An impulse is transmitted The change is reversed
C. Stimulus detected by an effector Stimulus is converted to a signal Signal is detected by a receptor A response occurs
D. Stimulus detected by a receptor Stimulus converted to an impulse An impulse is transmitted The impulse reaches an effector

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9
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The graph below shows how the body temperatures of two different species, X and Y, change as environmental temperature increases.

body-temp

Which of the following statements relating to the graph are correct?

  1. At environmental temperatures of 10 °C the enzyme-controlled reactions in species X will be taking place very slowly.
  2. At environmental temperatures of 40 °C species Y could be undergoing vasoconstriction.
  3. Species X has no mechanisms by which it can regulate its body temperature.
  4. Species X will need less food than species Y.

  • Only 1 and 2

  • Only 2 and 3

  • Only 1, 3 and 4

  • Only 1 and 4

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10
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The following paragraph outlines the responses of an endotherm to a decrease in environmental temperatures.

A decrease in core body temperature is detected by ...................................... which brings about a series of responses in the body. ...................................... in the surface of the skin ...................................... to reduce heat loss by radiation. Erector pili muscles in the skin ...................................... and the skeletal muscles contract and relax ...................................... to generate heat.

Which option from A-D gives the correct sequence of missing words to complete the paragraph?

  • Receptors in the skin, capillaries, contract, relax, slowly

  • The hypothalamus, capillaries, constrict, contract, consciously

  • Receptors in the skin, arterioles, constrict, constrict, involuntarily

  • The hypothalamus, arterioles, constrict, contract, involuntarily

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