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Neuroethology > Biological Clocks > Flashcards

Biological Clocks Flashcards

1
Q

what is biological clock theory

A

Animals have a timing mechanism with an endogenous, built in schedule, independent of environment

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2
Q

What is environment response theory

A

Relationships between command centers are modified by feedback from the environment… behavior changes as conditions change

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3
Q

What is the environment response theory for crickets

A

If cricket calling is controlled by environment, crickets in constant light should never call

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4
Q

What was the first cricket calling experiment

A

Grow crickets in lab under constant temperature/brightness, record calling

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5
Q

What were the results of the first cricket chirp experiment

A

Crickets continue calling in absence of environmental cue

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6
Q

What was the interpretation of the cricket chirp experiment

A

Mate calling is a free-running cycle, supporting idea that internal clock controls behavior

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7
Q

What is the time period of a circadian rhythm

A

“about a day”

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8
Q

What was the second cricket calling experiment

A

Grow crickets in lab on 12 hour light dark cycle and record calling

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9
Q

What were the results of the second cricket calling experiment

A

Crickets use the cue of darkness to adjust their calling so that it begins about 2 hours before lights off and ends about 2.5 hours before lights on

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10
Q

What was the interpretation of the second cricket calling experiment

A

Calling is reset/entrained each day to darkness, which matches the natural behavior

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11
Q

What hypothesis was supported by the cricket experiments and why

A

Both hypotheses: calling can occur independent of environment based on an internal clock but is normally reset each day during nightfall

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12
Q

What is the circadian rhythm pathway?

A

Sunlight/environmental cue -> sensory receptors -> pacemaker -> observed rhythms

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13
Q

What are sensory receptors considered

A

Clock-setting pathway

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14
Q

What is the pacemaker considered

A

Clock mechanism

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15
Q

What are the 4 observed rhythms in circadian rhythms

A

Locomotory patterns
Feeding behaviors
Hormone release patterns
Other rhythms

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16
Q

What structure is the “mammalian pacemaker”

A

Superchiasmatic nucleus (SCN)

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17
Q

What is the input to the SCN

A

Retina

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18
Q

What happens when SCN is removed from rodents

A

Arrhythmic patterns of locomotion, hormone secretion, feeding

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19
Q

What happens during transplant of SCN but noth other tissues

A

Locomotion, hormone secretion, feeding restored

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20
Q

what happens during transplant of mutant SCN

A

Mutant period length (shorter/longer than 24 hours)

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21
Q

What does the SCN do when removed from the brain

A

Maintains rhythmic secretions

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22
Q

*Research clock/per gene and add it to this

A

:(

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23
Q

What is the evidence for per as a timing gene (4)

A

Fruitfly mutations
Normal honeybee levels vary with behavior
Humans with a per mutation have altered sleep cycles
Gene is highly conserved and expressed in SCN

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24
Q

Explain honeybee per variation

A

Young nurse bees have low per and are active all day/night
Adult foragers, who go out during day, have higher per levels and exhibit defined circadian rhythms

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25
Q

What are the three expectations of the biological clock

A

Molecule relaying clocks instructions should be regulated by clocks genes
Molecule should be secreted and there should be a receptor for secretions in target behavior mediating tissue
Experimental manipulation of chemical should disrupt timing of behavior

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26
Q

What are the 2 candidate molecules for the “biological clock”

A

Melatonin and PK2

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27
Q

What is melatonin

A

Hormone released by hypothalamus at dusk that promotes sleep

28
Q

What is PK2

A

Prokineticin 2. Found in mRNA

29
Q

Why is PK2 thought to potentially be biological clock

A

Amount found in mRNA increased in beginning/end of day and decreases in middle of day

30
Q

What are the three pieces of evidence for PK2 as the circadian clock signal

A

Mice with mutations in per and tim lack cyclic production of PK2
Only certain structures produce a PK2 receptor
Injections of PK2 during the night, when levels are normally low and rats are active, leads to cessation of activity and sleep (daytime behavior)

31
Q

What are the two adaptive values of circadian rhythms

A

Individuals do not always have to check environment to see what time it is
Individuals CAN use environment to subtly adjust their clock to changing conditions

32
Q

Which animals do not have circadian clocks

A

Animals that do not use a day-night cycle

33
Q

How does reproductive physiology correspond to hibernation

A

Molting corresponds to decrease in testicle width

34
Q

How do white-crowned sparrows know spring is coming

A

Males fly north in spring, courts females, defends territory, and fights rivals
Gonads grow from the winter state

35
Q

What is the hypothesis for determining what the biological clock is

A

Clock exhibits a daily change in sensitivity to light that is reset every day at dawn

36
Q

Explain the clock’s daily change in sensitivity to light

A

Insensitive for the first 12 hours of light, then steadily rises to a peak around 16-20 hours after the start of the cycle, then fades again

37
Q

What happens to the clock if days are less than 12 hours

A

System will not be activated because no light is present during photosensitive period

38
Q

What is the hypothesis for the photosensitive hypothesis experiment

A

You should be able to trick the clock by manipulating day/night

39
Q

Describe the photosensitive hypothesis experiment

A

Start with 8 hours of light, 16 hours of dark: no stimulation during photosensitive period (days are short, testes dont grow) then switch to 8 hours of light and 28 hours of dark

40
Q

What were the results of the photosensitive hypothesis experiment

A

8L:28D causes testicle growth

41
Q

What are some reasons why photoperiod does not always reliably predict access to food or mates

A

Dry winter, delayed thaw

42
Q

What is a more reliable predictor of resources than photoperiod

A

Rainfall

43
Q

Which animal bases its habits off of rainfall

A

Arizona sparrow

44
Q

How does the Arizona sparrow base its habits off rainfall

A

Testes grow in March, as days lengthen, but following a dry winter, they dont breed
Rainfall during the July monsoons trigger production of LH, which stimulates testes to release testosterone, increasing song production and reproductive behaviors

45
Q

What type of cue are rainfall signals

A

Proximate cues

46
Q

What type of behavioral cue do Red crossbill finches use

A

Food abundance

47
Q

How do red crossbill finches use food abundance cues

A

Take advantage of good conditions regardless of season

48
Q

What is one thing that food abundance cues do not control in red crossbill finches?

A

Breeding

49
Q

When is breeding lowest in red crossbill finches

A

December and January (even with abundant food)

50
Q

What else suggests an internal clock regulates physiology

A

Under constant conditions, testes shrink and hormone levels decline from October to December, consistent with the photoperiod sensitivity exhibited by other temperate birds

51
Q

What happened when crossbill finches were caged with females

A

Underwent faster reproductive growth than males kept alone

52
Q

What happened when crossbill finches were exposed to a female for 60 minutes

A

Testosterone levels were raised and singing was initiated

53
Q

How does the moon impact feeding

A

Decreased belly size with higher luminosity (full moon)

54
Q

When do male mice become infanticidal

A

About three weeks after mating

55
Q

What is a possible reason for how the infanticidal timing is determined

A

Internal timing device counting off from time of last meeting

56
Q

What is the hypothesis for how infanticidal timing is determined

A

We should be able to manipulate the infanticidal period by altering the perceived length of a day

57
Q

What was the fast day in infanticide behavior experiment

A

11L:11D

58
Q

What was the fast day in infanticide behavior experiment

A

13.5L:13.5D

59
Q

What were the results of the infanticide behavior experiment

A

Fast and slow day males continue habits based on how many days they percieved

60
Q

What are the implications of the results of the infanticide behavior experiment

A

Timing device in males detects number of light-dark cycles since last mating and could potentially control male hormones

61
Q

What are the two male hormones

A

Testosterone and progesterone

62
Q

What does high testosterone lead to

A

high aggression and infanticide

63
Q

What does high progesterone lead to

A

Suppression of parental behavior

64
Q

What is the hypothesis for the mechanism for infanticide experiment

A

If progesterone is key to infanticide, then males lacking progesterone receptors should not kill pups

65
Q

What is the mechanism for infanticide experiment

A

Generate a genetic knock out of the PR gene, expose males to new pups

66
Q

What were the results of the mechanism for infanticide experiment

A

PR-/- males do not kill pups
Levels of Progesterone and Testosterone are the same as in wild type mice

Neuroethology (16 decks)

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