Chapter 50

Question 1

Signals (3)

Answer 1

1. Organisms need to send and receive signals to regulate growth, development, reproduction, energy metabolism and behaviour
2. Inter- and Intra- organismal
3. Between organisms and environment

Question 2

3-Step Signalling Cascade

Answer 2

1. Reception
2. Transduction
3. Response

Question 3

Cellular-Level Signalling in Animals (4)

Answer 3

1. Hormones regulate development (except in simplest invertebrates)
2. Synthesized in endocrine glands
3. Secreted to extracellular fluid
4. Transported by circulatory system

Question 4

Cellular-Level Signalling in Plants (3)

Answer 4

1. Phytohormones regulate development
   * synthesized throughout, although some are produced in certain tissues
2. Few plant hormones - each elicits a variety of responses and usually works together with other hormones
3. Many animal hormones - each has specific action and cooperation is not essential

Question 5

Cellular-Level Signalling in Unicellular Organisms

Answer 5

Quorum Sensing

Question 6

Organisms Signal Other Organisms (4)

Answer 6

1. Exchange visual, chemical, tactile, and auditory cues
2. Importance of each differs between organisms
3. Not all organisms use all modes
4. Occurs within and between species

Question 7

Signaling Within Species

Answer 7

mating, survival, and co-operation

Question 8

Signaling Between Species

Answer 8

• survival

- organisms communicate to establish and protect symbiotic relationships

Question 9

Organisms Receive Signals from the Environment (2)

Answer 9

1. Sense pressure (touch), gravity, sound, temperature, chemicals, electromagnetic radiation
2. Cue to direct growth and behaviour

Question 10

Electromagnetic Radiation in Plants

Answer 10

1. Phytochromes are a crucial photo-receptor
2. Shade Avoidance:
   - chlorophyl absorbs red-light, so light beneath a plant canopy is higher in far-red
   - accumulation of Pr
   - Allocate resources to height to reach light

Question 11

Electromagnetic Radiation in Animals

Answer 11

1. Most have organ containing photoreceptors
   - turn light energy into nerve signals for processing
2. Compound eyes detect movements very well
3. Single-lens eyes focus light on a layer of photoreceptor cells

Question 12

Vision is Variable

Answer 12

1. Humans see in the ‘visible spectrum’

2. Birds and bees can see into the UV spectrum