A2 Ocr Biology: Communication

Front 1

a) Outline the need for communication systems in multicellular organisms

Back 1

Multicellular organisms need communication systems in order to respond to changes in their internal and or their external environment. They also need to be able to coordinate activities between organs.

Hint 1

- response - internal - external

Front 2

b) How do cells communicate with each other?

Back 2

Through a process called cell signalling.

Front 3

c) Name two examples of cell signalling.

Back 3

Hormonal and neuronal systems.

Front 4

d) Define the term "negative feedback".

Back 4

Negative feedback is a process by which any changes in a parameter brings about a response that reverses that change, so that it returns to its original set of conditions.

Hint 4

reversal

Front 5

d) Define the term "positive feedback".

Back 5

Positive feedback is a process in which any changes in a parameter leads to a response that increases that change.

Hint 5

increase

Front 6

d) Define the term "homeostasis".

Back 6

Homeostasis is th maintenance of an external environment in a constant state despite changes to the external environment.

Hint 6

- maintain - despite

Front 7

e) What are the principles of homeostasis?

Back 7

A stimulus is detected by a receptor (I. e. sensory receptor). The receptor then uses a communication pathway (cell signalling) in order to send a signal to an effector (hepatocyte, muscle cell etc). Once an effector receives this signal, the effector carries out a response that reverses that change.

Hint 7

- stimulus - receptor - communication pathway - effector - reversal

Front 8

e) What things need to maintain homeostasis?

Back 8

- Body temperature
- Blood glucose concentration
- Blood pressure

Hint 8

Blood, body

Front 9

f) What is an ectotherm?

Back 9

An ectotherm is an organism that relies on external sources of heat in order to regulate its body temperature.

Hint 9

external, temperature