Week 2 (Modules 3-4)

Question 1

Proximate causality = ____ or ______ questions

Answer 1

• how

- mechanism

Question 2

Ultimate causality = _____ or ______ questions

Answer 2

• why

- function

Question 3

When did life arise on Earth?

Answer 3

~3.5 billion years ago

Question 4

In which domains of life are circadian rhythms found?

Answer 4

all 3 (eukaryote, bacteria, archaea)

Question 5

Circadian clocks have ______ several times

Answer 5

evolved

Question 6

What is the ‘escape from light’ hypothesis?

Answer 6

Ancient organisms may have evolved to perform vulnerable cellular processes at night, so UV rays do not disrupt them

Question 7

What are the two hypotheses for the origins of circadian rhythms?

Answer 7

• escape from light/oxygen (external coordination)

- internal biochemical coordination

Question 8

What is the ‘escape from oxygen’ hypothesis?

Answer 8

Ancient anaerobic organisms may have evolved circadian rhythms in order to produce antioxidants during the day, when photosynthesizing organisms produce oxygen

Question 9

What is the ‘internal biochemical coordination’ hypothesis?

Answer 9

Organisms evolved circadian rhythms in order to be able to temporally separate internal processes that cannot occur at the same time

Question 10

One of the most important functions of clocks is to anticipate _____

Answer 10

the change from day to night and back

Question 11

Two uses of being able to predict the changes from night to day are:

Answer 11

• organisms are able to predict when food will be readily available
• organisms can predict when the best time to perform a biological function is

Question 12

What is FAA?

Answer 12

Food-anticipatory activity - the emergence of activity prior to mealtime

Question 13

At what time of day can rats and mice anticipate meals?

Answer 13

Any time of day

Question 14

What are the two different modes of circadian clocks?

Answer 14

• alarm clock mode

- wristwatch mode

Question 15

What is time-place learning?

Answer 15

When animals can discriminate time of day by learning to go to a particular place at a particular time of day

Question 16

What is time-compensated sun-compass orientation?

Answer 16

When animals use the location of the sun to navigate, also taking into account the movement of the sun throughout the day

Question 17

What is ‘swamping’?

Answer 17

When animals wait until a certain time using circadian clocks to perform an action that makes them vulnerable together

Question 18

What is temporal niche segregation?

Answer 18

When two competitor species in the same niche use a circadian clock to be active during different parts of the day

Question 19

What is photoperiodism?

Answer 19

When animals use circadian clocks to keep track of days passing, in order to anticipate yearly changes in the environment

Question 20

Disrupted circadian rhythms have been linked to higher mortality rates of ____

Answer 20

cancer

Question 21

Most organisms function optimally when _______

Answer 21

there is a match between the period of their circadian clock and the cycles of the environment

Question 22

Loss of circadian rhythms has been suggested to cause

Answer 22

reduced lifespan

Question 23

What is an oscillator?

Answer 23

Any device that produces a rhythm

Question 24

What is a pacemaker?

Answer 24

Controls other oscillators

Question 25

What is an interval timer?

Answer 25

A clock that is limited to timing one interval, then must be reset

Question 26

What two problems does entrainment solve?

Answer 26

• Adjusting the timing to fit with a 24-hour interval

- Synchronizing the rhythm with the environment

Question 27

What is masking?

Answer 27

A direct effect of an environmental stimulus on behaviour

Question 28

If synchrony to a changed LD cycle is instantaneous, this is probably due to ____

Answer 28

masking

Question 29

What is the difference between positive and negative masking?

Answer 29

Negative masking suppresses a behaviour, while positive masking stimulates it

Question 30

What is the non-parametric entrainment model?

Answer 30

The hypothesis that entrainment can occur with small daily phase adjustments (period of the rhythm is not a parameter)

Question 31

What is a parameter?

Answer 31

A feature of a clock that can be set

Question 32

What can you predict if you know the tau of a circadian clock and the shape of its phase response curve?

Answer 32

• limits to entrainment
• phase of entrainment
• gradual re-entrainment

Question 33

What factors determine how long it takes to shift to a new time zone?

Answer 33

• the magnitude of the shift
• the direction of travel
• the timing of light exposure
• parameters (wavelength, amplitude) of the light stimulus

Question 34

What is the parametric entrainment model?

Answer 34

Hypothesizes that light entrains circadian rhythms by altering both the phase and period of the clock (period is a parameter of the rhythm)

Question 35

Global environmental features are _______

Answer 35

• enduring
• stable
• nontrivial

Question 36

From where did circadian clocks likely emerge?

Answer 36

primitive prokaryotic life forms

Question 37

Where are local oscillators found?

Answer 37

In the specific body part they are responsible for providing a circadian rhythm for

Question 38

What are three defining characteristics of circadian clocks?

Answer 38

• self-sustaining and have a ~24h period in consistent conditions
• temperature compensated
• entrainable by environmental stimuli