Unit 1, Module 1 - Homeostasis

Question 0

What is an example of a gradual response to the external environment?

Answer 0

The seasons passing.
The arctic fox has a much thicker white coat in winter.
It has a thinner grey/brown coat in summer.
The different coats adapt it to the changing conditions.

Question 1

What specific conditions do enzymes need to work efficiently?

Answer 1

A suitable environment
A suitable pH
An aqueous environment that keeps the substances and products in solution
Freedom from toxins and excess inhibitors

Question 2

What are examples of when a rapid response to the external environment is required?

Answer 2

The changes from day to night.

Walking from bright sunlight into an unlit room.

Question 3

Why is a good communication system required?

Answer 3

To ensure that the different parts of the body work together effectively.

Question 4

What will a good communication system do?

Answer 4

Cover the whole body
Enable cells to communicate with each other
Enable specific communication
Enable rapid communication
Enable both short-term and long-term responses

Question 5

How do cells communicate?

Answer 5

By the process of cell signalling.

Question 6

What are the two major systems of communication that work by cell signalling?

Answer 6

The neuronal system

The hormonal system

Question 7

What conditions must be kept constant inside the body?

Answer 7

Body temperature
Blood glucose concentration
Blood salt concentration
Water potential of the blood
Blood pressure
Carbon dioxide concentration

Question 8

What processes must occur in order to maintain a constant internal environment?

Answer 8

Any change in the internal environment must be detected.
The changes must be signalled to other cells.
There must be a response that reverses the change.

Question 9

What is the standard pathway used to produce a suitable response to a stimulus?

Answer 9

stimulus -> receptor -> cell signalling -> effector -> response

Question 10

What structures are required for the standard pathway used to produce a suitable response to a stimulus?

Answer 10

Sensory receptors, such as temperature receptors or glucose concentration receptors.
A communication system, such as the nervous system or hormonal system.
Effector cells, such as liver cells or muscle cell.

Question 11

What do sensory receptors do in the process of negative feedback?

Answer 11

These receptors are internal and monitor conditions inside the body.
If they detect a change they will be stimulated to send a message.

Question 12

What does a communication system do in the process of negative feedback?

Answer 12

It acts by signalling between cells.
It is used to transmit a message from the receptor cells to the effector cells,
The message may pr may not pass through a coordination centre such as the brain.

Question 13

What do effector cells do in the process of negative feedback?

Answer 13

They bring about a response that reverses the change detected by the receptor cells.

Question 14

What is an example of positive feedback that has a negative effect on the body?

Answer 14

Below a certain core body temperature the enzymes become less active.
If they are less active the exergonic reactions that release heat are slower and release less heat.
This allows the body to cool further and slows down the enzyme-controlled reactions even more, so that the body temperature spirals downwards.

Question 15

What is an example of when positive feedback is beneficial?

Answer 15

At the end of pregnancy to bring about dilation of the cervix.
As the cervix begins to stretch the change is signalled to the anterior pituitary gland, stimulating it to secrete oxytocin.
Oxytocin increases the uterine contractions, which stretch the cervix more, which cause secretion of more oxytocin.

Question 16

How do ectotherms keep warm and why?

Answer 16

External sources of heat.

This is because they are not able to increase respiration rates to generate heat internally.

Question 17

What are the advantages of being an ectotherm?

Answer 17

Use less of their food in respiration.
Need to find less food and may be able to survive long periods without eating.
A greater proportion of the energy obtained from food can be used for growth.

Question 18

What are the disadvantages of being an ectotherm?

Answer 18

Less active in cooler temperatures, and may need to warm up in the morning before they can be active. This puts them at greater risk of predation.
May not be capable of activity during the winter as they never warm up sufficiently. This means they must have sufficient stores of energy to survive over winter without eating.

Question 19

How do ectotherms regulate their body temperature?

Answer 19

When one is cold it will change its behaviour or physiology to increase absorption of heat from the environment.
When one is hot is will change its behaviour or physiology to decrease absorption of heat and increase loss of heat to its environment.

Question 20

What adaptions do snakes have and how does it regulate temperature?

Answer 20

Expose body to sun - Enables more heat to be absorbed

Question 21

What adaptions do locusts have and how do it help regulate temperature?

Answer 21

Orientate body to sun - Exposes larger surface area for most heat absorption
Orientate body away from sun - Exposes lower surface area so that less heat is absorbed.
Increase breathing movements - Evaporates more water.

Question 22

What adaptions to lizards have and how does it help to regulate temperature?

Answer 22

Hide in burrow - Reduces heat absorption by keeping out of the sun.
Horned lizards alter body shape - Exposes more or less surface area to sun.

Question 23

How do endotherms maintain body temperature?

Answer 23

Internal sources of heat.

Behavioural and physiological mechanisms.

Question 24

What are the advantages of being a endotherm?

Answer 24

A fairly constant body temperature whatever the temperature is externally.
Activity possible when external temperature are cool.
Ability to inhabit colder parts of the planet.

Question 25

What are the disadvantages of being an endotherm?

Answer 25

A significant part of the energy intake used to maintain body temperature in the cold.
More food required.
Less of the energy from food is used for growth, or more food is needed in order to grow.

Question 26

What are the main physiological components used to maintain body temperature in endotherms?

Answer 26

Sweat glands in skin
Lungs, mouth and nose
Hairs on skin
Arterioles leading to capillaries in skin.
Liver cells
Skeletal muscles

Question 27

How do sweat glands help to maintain body temperature?

Answer 27

If temperature is too high they secrete more sweat onto skin; water in sweat evaporates, using heat from blood to supply latent heat of vaporisation.
If temperature too low less sweat is secreted; less evaporation of water, so less loss of latent heat.

Question 28

How do the lungs, mouth and nose help to maintain body temperature?

Answer 28

If too high panting increases evaporation of water from lungs, tongue and other moist surfaces, using latent heat.
If too low animal does not pant, so less water evaporates.

Question 29

How do the hairs on skin help to maintain body temperature?

Answer 29

If too high hairs lie flat, providing little insulation, and thus more heat can be lost by convection and radiation.
If too low hairs are raised to trap a layer of insulating air, reducing the loss of heat from the skin.

Question 30

How do arterioles leading to capillaries in skin help to maintain body temperature?

Answer 30

If too high vasodilation allows more blood into capillaries near the skin surface; more heat can be radiated from the skin.
If too high vasoconstriction reduces the flow of blood through capillaries near the the skin surface; less heat is radiated.

Question 31

How do liver cells help to maintain body temperature?

Answer 31

If too high rate of metabolism is reduced, less heat is generated from exergonic reactions.
If too low rate of metabolism is increased, therefore respiration generates more heat, which is transferred to the blood.

Question 32

How do skeletal muscles help to maintain body temperature?

Answer 32

If too high no spontaneous contractions.

If too low spontaneous contractions generate heat as muscle cells respire more.

Question 33

What behavioural mechanisms help to maintain body temperature if too high.

Answer 33

Move into shade or hide in burrow.
Orientate body to decrease surface area exposed to sun.
Remain inactive and spread out limbs to increase surface area.

Question 34

What behavioural mechanisms help to maintain body temperature if an endotherm is cold?

Answer 34

Move into sunlight.
Orientate body to increase surface area-exposed to sun.
Move about to generate heat in muscles.

Question 35

Where do endotherms monitor body temperature?

Answer 35

The thermoregulatory centre in the hypothalamus of the brain.

Question 36

What do the peripheral temperature receptors do?

Answer 36

Monitor the temperature in the extremities.
This information is fed to the thermoregulatory centre in the hypothalamus which can initiate behavioural mechanisms for maintaing body temperature.