Communication (5)

Question 1

What are the 4 needs for communication?

Answer 1

Keeping cells alive, cell signalling, stimulus and response, coordination.

Question 2

Homeostasis definition.

Answer 2

Maintaining a constant internal environment despite changes in internal and external stimuli.

Question 3

Examples of internal and external stimuli that organisms must respond to.

Answer 3

Internal - body temperature, pH, blood glucose, water potential.

External - humidity, external temperature, light intensity, new or sudden sound.

Question 4

Example of coordination in plants.

Answer 4

Plant stem grows towards the light to maximise the rate of photosynthesis (plant hormones).

Question 5

What is cell singalling?

Answer 5

When one cell releases a chemical which has an affect on the target cell which then responds to it. Neuronal and hormonal systems work by cell signalling.

Question 6

Negative feedback definition.

Answer 6

Effectors work to reverse change and restore conditions back to the optimum. This involves the nervous system and sometimes the hormonal system.

Optimum → change (stimulus) → detect (receptor) → communicate (cell signalling) → respond (effector) → reverse change → optimum.

Question 7

Negative feedback example.

Answer 7

Regulating body temperature.

Question 8

Positive feedback definition.

Answer 8

A change is reinforced and the response is increased further away from the optimum.

Optimum → change away from optimum (stimulus) → detect (receptor) → communicate (cell signalling) → respond (effector) → increase change → change further away from the optimum.

Question 9

Positive feedback example.

Answer 9

Childbirth - when the head of the foetus pushes against the cervix, oxytocin is released, this causes the uterus to contract which pushed the babies head further into the cervix and therefore releasing more oxytocin.

Hypothermia - being cold causes less kinetic energy which causes exergonic reactions releasing energy to slow down. This causes respiration to slow down which causes less heat energy to generate = slower enzyme activity and metabolic reactions, causing someone to get even colder.

Question 10

Ectotherm definition.

Answer 10

Animals which use their surroundings to heat up their bodies, meaning their core body temperature is heavily dependant on their surroundings.

Question 11

What types of animals are ectotherms?

Answer 11

Reptiles, amphibians, fish and invertebrates.

Question 12

Thermoregulation definition.

Answer 12

Ability of an organism to keep its body within certain temperature boundaries, even when surrounding temperature is very different.

Question 13

Why do ectotherms living in water not need to thermoregulate.

Answer 13

The high specific heat capacity of the water means that it needs lots of every for it to change temperature. This means that the temperature of their environment does not change very much.
Whereas ectotherms on land have more of a problem because the temperature of the sir fluctuates.

Question 14

What do ectotherms do when they are too cold?

Answer 14

Bask in the sun.
Orientate themselves for maximum sun exposure.
Extend areas of their body to increase the surface area of their body which is exposed.
Contract muscles and vibrate to increase cellular metabolism.
Dark pigment of some absorbs more radiation.
Altering heartrate to increase metabolic rate.

Question 15

What do ectotherms do when they are too hot?

Answer 15

Seek shade.
Orientate away from the sun for less exposure.
Press body against cool rock.
Hiding in cracks in rocks.
Digging burrows.
Move into water/mud.
Minimise movement to reduce metabolic heat generated.
Increase respiration rate.

Question 16

Advantages of being an ectotherm.

Answer 16

Using less energy (making more available for growth as it is not being used to maintain body temperature).
Don’t have to eat as much food (can survive in habitats with low food availability).

Question 17

Disadvantages of being an ectotherm.

Answer 17

Core body temperature is heavily dependant on environment.
Less active in lower temperatures means that they are at risk from predators (due to their low body temp) also unable to find food.
Less able to live.

Question 18

Endotherm definition.

Answer 18

Animals that rely on their metabolic processes to warm them up and maintain body temperature.

Question 19

What type of animals are endotherms?

Answer 19

Mammals and birds.

Question 20

How do endotherms thermoregulate?

Answer 20

Peripheral temperature receptors in the skin monitor temperature changes because they are in direct contact with the external temperature.
This sends an impulse along the sensory neurone to the brain, to thermoregulatory centre in the hypothalamus to act as an early warning system (coordinates impulse).
This triggers a response by glands in the skin and muscles. (example - move into shade).

Question 21

How does skin and sweat glands maintain body temperature?

Answer 21

If core temperature is too high, sweat glands release more sweat onto the skin, the water evaporates, using heat from the blood to supply latent heat of vaporisation.

If core temperature is too low, there is less sweating which causes less heat loss.

Question 22

How does the lungs, nose and mouth maintain body temperature?

Answer 22

If core temperature is too high, animals pant to increase the evaporation.

If core temperature is too low, there is less panting which causes less heat loss.

Question 23

How do hairs maintain body temperature?

Answer 23

If core temperature is too high, the hairs lie flat on the skin.

If core temperature is too low, the erector pili muscles contract which raises hairs to trap a layer of insulating air, which reduces heat loss from the skin.

Question 24

How do arterioles leasing to capillaries in the skin maintain body temperature?

Answer 24

If core temperature is too high, vasodilation takes place, causing more blood to flow through the capillaries to the surface of the skin, resulting in more heat loss.

If core temperature is too low, vasoconstriction takes place, this constricts the flow of blood to the capillaries so there is less heat loss from the surface of the skin.

Question 25

How does the liver maintain body temperature?

Answer 25

If core temperature is too high, the rate of metabolism is reduced and less heat is generated from exergonic reactions such as respiration.

If core temperature is too low, the rate to metabolism is reduced.

Question 26

How does the skeletal muscle maintain body temperature?

Answer 26

If core temperature is too high, shivering stops and less heat is generated.

If core temperature is too low, spontaneous contractions (shivering) generates metabolic heat from exothermic reactions (muscle cells respire more)

Question 27

What do endotherms do when they are too cold?

Answer 27

Bask in the sun.
Orientate body to increase surface area exposed to the sun.
Become active to generate heat.
Roll into a ball to reduce surface area.
Put more clothes on.
Remain dry.

Question 28

What do endotherms do when they are too hot?

Answer 28

Move into shade/hide in a burrow.
Orientate body away from the sun.
Remain inactive and spread out limbs to increase surface area.
Wet skin to use evaporation to cool off.

Question 29

Advantages of being an endotherm.

Answer 29

Maintain a very stable core body temperature regardless of the temperature of the environment.
Can survive in a wide range of temperatures.
Remain active when external temperatures are too low allowing them to escape from predators.

Question 30

Disadvantages of being an endotherm.

Answer 30

Need more energy from food, so need to find efficient food.
They spend more time eating.
Can overheat.