Podcast
Questions and Answers
What characteristic distinguishes circadian rhythms from other biological processes?
What characteristic distinguishes circadian rhythms from other biological processes?
- Their limited influence on diverse physiological functions.
- Their ability to persist under constant environmental conditions. (correct)
- Their direct regulation by seasonal changes.
- Their exclusive dependence on external light cues.
Why is the study of jet lag relevant to understanding biological clocks?
Why is the study of jet lag relevant to understanding biological clocks?
- It shows how biological clocks can be instantaneously reset.
- It illustrates that biological clocks can be temporarily disrupted when external cues are mismatched. (correct)
- It proves that jet lag is purely psychological and not related to biological processes.
- It demonstrates that biological clocks are not affected by environmental time cues.
What key role does melatonin play in the context of photoperiodism?
What key role does melatonin play in the context of photoperiodism?
- It serves as a hormonal signal conveying information about day length. (correct)
- It directly absorbs light and triggers immediate physiological responses.
- It regulates body temperature independently of light exposure.
- It controls the perception of color in the eyes.
How does temperature compensation contribute to the reliability of circadian rhythms?
How does temperature compensation contribute to the reliability of circadian rhythms?
In the context of circadian rhythms, what does 'free-running' refer to?
In the context of circadian rhythms, what does 'free-running' refer to?
Which of the following is an example of a physiological process influenced by photoperiodism?
Which of the following is an example of a physiological process influenced by photoperiodism?
How do short-day plants respond to light exposure?
How do short-day plants respond to light exposure?
What does the term 'entrainment' refer to in the context of circadian rhythms?
What does the term 'entrainment' refer to in the context of circadian rhythms?
How might changes in day length affect the timing of migration in birds?
How might changes in day length affect the timing of migration in birds?
Considering the relationship between the SCN (suprachiasmatic nucleus) and the pineal gland in mammals, how is melatonin production regulated?
Considering the relationship between the SCN (suprachiasmatic nucleus) and the pineal gland in mammals, how is melatonin production regulated?
If an organism displays a consistent activity pattern that shifts slightly later each day under constant conditions, what does this suggest about its circadian rhythm?
If an organism displays a consistent activity pattern that shifts slightly later each day under constant conditions, what does this suggest about its circadian rhythm?
What would be the most likely effect of completely removing all light from the environment of a diurnal animal with a functional biological clock?
What would be the most likely effect of completely removing all light from the environment of a diurnal animal with a functional biological clock?
How does the molecular clock mechanism use feedback loops?
How does the molecular clock mechanism use feedback loops?
Which of the following scenarios would provide the strongest evidence that a particular behavior is regulated by a circadian rhythm?
Which of the following scenarios would provide the strongest evidence that a particular behavior is regulated by a circadian rhythm?
What effect would you expect to see in an animal that has the gene for the CLOCK protein knocked out?
What effect would you expect to see in an animal that has the gene for the CLOCK protein knocked out?
Imagine an animal species that relies on hibernation to survive the winter. How might photoperiod influence this behavior?
Imagine an animal species that relies on hibernation to survive the winter. How might photoperiod influence this behavior?
In the context of detoxifying enzymes, how does circadian rhythmicity relate to the effectiveness of pesticides on insects?
In the context of detoxifying enzymes, how does circadian rhythmicity relate to the effectiveness of pesticides on insects?
What might be the advantage of seasonal reproduction that is timed according to photoperiod?
What might be the advantage of seasonal reproduction that is timed according to photoperiod?
How does the use of a mouse activity meter provide evidence for behavioral rhythms?
How does the use of a mouse activity meter provide evidence for behavioral rhythms?
Flashcards
Biological clock
Biological clock
Internal mechanism controlling cyclic activities.
Circadian rhythms
Circadian rhythms
Daily cycles of activity influenced by internal biological clocks.
Circadian diversity
Circadian diversity
Differences in circadian rhythms among species.
Jet lag
Jet lag
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Parietal eye
Parietal eye
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Melatonin
Melatonin
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Ocelli
Ocelli
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Photoperiodism
Photoperiodism
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Suprachiasmatic Nucleus (SCN)
Suprachiasmatic Nucleus (SCN)
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Critical photoperiod
Critical photoperiod
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Animal migration
Animal migration
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Hibernation
Hibernation
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Study Notes
Biological Time-Keeping Evidence
- Biological time-keeping is evidenced by circadian rhythms, showcasing diversity across species.
- Diagnostics of circadian rhythms and the experience of jet lag also supports the existence of biological clocks.
Biological Clock Mechanisms
- The mechanism of the biological clock involves light receptors such as the parietal eye, pineal gland, melatonin, and ocelli.
Photoperiodism and Seasonal Lives
- Photoperiodism is a key aspect of seasonal lives, influencing reproduction, migration, and hibernation.
Daily Body Temperature Cycles
- Daily body temperature cycles vary across mammals, as seen in hamsters, humans, and tree shrews.
Testicular Hormone Biosynthesis
- Testicular hormone biosynthesis involves hormones like Inhibin B, anti-Müllerian hormone, testosterone, and insulin-like peptide 3, exhibiting variations throughout the day.
Detoxifying Enzyme Levels
- Detoxifying enzyme levels, including ethoxycoumarin-O-deethylase (ECOD) and glutathione-S-transferase (GST), fluctuate in a circadian manner.
Sensitivity to Toxins
- Sensitivity to toxins, such as pesticides like Baygon (propoxur) and various toxins affecting Blatella, varies depending on the time of day.
Diagnostic Criteria for Circadian Rhythms
- Diagnostic criteria for circadian rhythms include free-running under constant conditions, a free-running rhythm that is not exactly 24 hours, entrainment by photoperiod, and temperature-compensated free-running rhythm.
Shift to Different Photoperiod
- An organism shows a shift to a different photoperiod
Shift to Constant Conditions
- An organism shows a shift to constant conditions
Molecular Clock Mechanism
- The molecular clock mechanism involves a feedback circuit with delay via slow reactions and decay.
- Synthesis of A leads to synthesis of B and C
- Product C causes inhibition on A.
Entraining Signals
- Signals that can entrain the clock include the light received via the day/night signal.
Parietal Eye, Pineal Gland, and Melatonin
- Eye signals travel to the SCN (suprachiasmatic nucleus) and then to the sympathetic nervous system in the spinal cord, leading to melatonin secretion by the pineal gland.
Insect Ocelli
- Insect ocelli are light receptors.
Photoperiodism Definition
- Photoperiodism refers to the sensitivity to, and physiological response to, the photoperiod (day length).
Photoperiodism and Critical Photoperiod
- Photoperiodism involves a critical photoperiod that determines whether a plant is classified as a short-day or long-day plant.
Seasonal Adaptations
- Animals display seasonal changes in coat color (Arctic fox, Ptarmigan) and antler growth in male deer
Breeding Cycles
- The seasonal timing of breeding cycles ensures that birth occurs in spring for both short-day and long-day breeders.
Hibernation Metabolism
- Metabolism during hibernation in animals such as the Alpine Marmot and Ground Squirrel slows down
Migration Patterns
- Migration patterns of the European Blackcap Sylvia atricapilla show that the birds fly to different areas at different times of the year
Light, Temperature, and Food Quality
- Monarch migration is stimulated by day length, temperature, and food quality, which jointly affect the level of juvenile hormone (JH).
- short days, poor food, low temperature [JH] low = hibernations (diapause)
- short days, medium temperature [JH] intermediate = migration
- long days, high temperature [JH] high = gonad development & reproduction
Ruby-Throated Hummingbird Migration
- The Ruby-Throated Hummingbird migrates from Quebec to Costa Rica.
Monarch Populations
- Monarch populations fluctuate with the seasons and time of year.
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