3.3 Biological Clocks

Question 1

Zeitgeber

Answer 1

External cue influencing biological clock

Question 2

Circadian rhythm

Answer 2

Cyclic repeating activity processes that continues under constant environmental conditions (free running period 24 hours approx)

Question 3

Circannual

Answer 3

Repeats approx yearly

Question 4

Circatidal

Answer 4

Cycle approx in sync with tides (12.4 hours)

Question 5

Circalunar

Answer 5

Cycles in sync with moon phases (29 days)

Question 6

Diurnal

Answer 6

Active during day

Question 7

Nocturnal

Answer 7

Active during night

Question 8

Crepuscular

Answer 8

Active at dawn and dusk

Question 9

What are ganglion?

Answer 9

Specialized photosensitive cells in retina

Question 10

Which organ is the SCN located in?

Answer 10

Brain (hypothalamus)

Question 11

3 core steps of entrainment:

Answer 11

1. Ganglion in retina process illumination levels, send info to SCN
2. SCN interprets info, send to pineal gland
3. Pineal gland secretes melatonin at a rate which is inversely proportional to light intensity

Question 12

What is nyctinasty?

Answer 12

Night movements of plants

Question 13

What are phytochromes and what do they do?

Answer 13

Cells that detect light change.

They respond to red light (day) and far red light (night) and establish circadian cycles.

Question 14

What is the photoperiod?

Answer 14

The amount of daylight

Question 15

What is the noctoperiod?

Answer 15

A period of uninterrupted darkness (critical night length).

Question 16

Long day plants (2pts)

Answer 16

• Exceed critical day length

- Flower in summer and spring

Question 17

Short day plants (2pts)

Answer 17

• Precede critical day length

- Flower in autumn and winter