Evolution and Adaptive Functions of Biological Rhythms and Clocks

Question 1

Circadian rhythms are important for what reasons?

Answer 1

• Help sync daily activities

- Help sync developmentally significant events

Question 2

Why is it assumed that biological clocks evolved several times?

Answer 2

Because animals, plants, and bacteria do not share any of the same genes

Question 3

True or false: Circadian rhythms are present in all forms of life

Answer 3

True

Question 4

What is the “external coordination/escape from light” explanation of circadian clock origins?

Answer 4

Sunlight includes radiation that can disrupt cellular processes, and early organisms could not protect themselves from the sun, therefore, they adapted to be more active at night

Question 5

What is some evidence that supports the “external coordination/escape from light” explanation of circadian clock origins?

Answer 5

• Cell division and gene transcription occur mainly at night in many species
• Cells are more easily damaged by UV light in the early night when cell division and gene transcription occur

Question 6

What is the internal coordination of biochemical processes explanation of circadian clock origins?

Answer 6

Some vital processes are incompatible with other important processes, and circadian rhythms can help create a timeline so that incompatible processes don’t overlap

Question 7

What are some things that circadian clocks are used for aside from sleep?

Answer 7

• Finding mates
• Food availability
• Predator and competitor avoidance
• Parasite avoidance
• Habitat selection
• Photoperiodism

Question 8

Photoperiodism

Answer 8

The ability to measure the length of the day and use that info to know the time of year, and anticipate what behaviour changes are necessary for upcoming seasonal changes

Question 9

Is circadian organization a physiological necessity for life?

Answer 9

No

Question 10

At the species level, what is the relationship between circadian tau and lifespan?

Answer 10

The greater the deviation from 24 hours, the shorter the lifespan

Question 11

Proximate causality

Answer 11

The “how” questions; the biological mechanisms

Question 12

Ultimate causality

Answer 12

The “why” questions

Question 13

Explain how circadian clocks are used for periodic food sources

Answer 13

Use circadian clock to recognize and remember time of day when food is reliably found

Question 14

In what animals is the use of circadian clocks for period food sources seen?

Answer 14

Bees, birds, rodents, and fish

Question 15

Time-place learning is another name for what?

Answer 15

Using circadian clocks for periodic food sources

Question 16

Explain how circadian clocks are used for competitor avoidance

Answer 16

Use circadian clock to limit activity to day or night to avoid competition

Question 17

Explain how circadian clocks are used for social coordination

Answer 17

Circadian clock ensures that males and females are active at the same time, increasing chances that they will meet

Question 18

Explain how circadian clocks are used for predator avoidance

Answer 18

Use circadian clock to avoid predation

Question 19

What is an example of using circadian clocks for predator avoidance?

Answer 19

Fledging birds

Question 20

Explain how circadian clocks are used for parasites

Answer 20

• Avoidance of parasites
• Coordination of parasites with vectors
• Avoidance of immune defences

Question 21

What is an example of how circadian clocks are used for coordination of parasites with vectors?

Answer 21

Microfilarial parasites reside in host organs liver and come into the host blood stream only during the few hours of day when mosquitos (the vectors for transmission to next host) are active

Question 22

What is an example of how circadian clocks are used for avoidance of immune defences in parasites?

Answer 22

The microfilarial strategy of entering the blood system en mass for a short period of time each day also reduces total number of parasites that the immune system can kill

Question 23

Explain the fruit fly eclosion example

Answer 23

Fruit fly eclosion occurs at dawn when humidity is optimal for drying wings

Question 24

Why are circadian clocks still present in virtually all life forms?

Answer 24

It helps them prepare in advance of daily environmental changes instead of just reacting to them