5.1 Communication And Homeostasis

Question 1

All living things need to maintain a certain set of conditions inside there cells. These include: (4)

Answer 1

• suitable temperature
• suitable pH
• an aqueous environment that keeps the substrates and products in solution
• freedom from toxins and excess inhibitors

Without these conditions the cells will become inactive and die. Multicellular organisms - cells are specialised, rely upon one another, therefore must be able to communicate in order to coordinate activities.

Question 2

Define cell signalling

Answer 2

The way in which cells communicate with each other

Question 3

Changing external environments - what will a cooler environment cause ?

Answer 3

Greater heat loss

Question 4

Define receptor

Answer 4

A cell that detects a stimulus and creates action potentials (nervous impulse)

Question 5

Define effector

Answer 5

A cell, tissue or organ that brings about a response

Question 6

Define response

Answer 6

change in behaviour/physiology as a result of a stimulus

Question 7

Define internal environment

Answer 7

The conditions inside an organism

Question 8

External environment

Answer 8

The conditions outside of an organism

Question 9

Why do plants and animals need communication systems ?

Answer 9

Plants and animals need communication systems in order to respond to both internal and external environments and coordinate the activities of organs.

Question 10

What is the importance of organisms being able to respond to the internal environment ?

Answer 10

some products of metabolic activities are harmful ‐ their build up could be toxic ‐ they act as a stimulus for their own removal. maintains constant internal conditions (homeostasis)

Question 11

What is the importance of organisms being able to respond to the external environment?

Answer 11

to be able to adjust internal environment in response to external e.g. temperature
to adapt to changes in environment e.g. weather or scenery (camouflage)
find resources e.g. tropisms