Evolution and Adaptive Functions of Biological Rhythms and Clocks Flashcards
Circadian rhythms are important for what reasons?
- Help sync daily activities
- Help sync developmentally significant events
Why is it assumed that biological clocks evolved several times?
Because animals, plants, and bacteria do not share any of the same genes
True or false: Circadian rhythms are present in all forms of life
True
What is the “external coordination/escape from light” explanation of circadian clock origins?
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
What is some evidence that supports the “external coordination/escape from light” explanation of circadian clock origins?
- 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
What is the internal coordination of biochemical processes explanation of circadian clock origins?
Some vital processes are incompatible with other important processes, and circadian rhythms can help create a timeline so that incompatible processes don’t overlap
What are some things that circadian clocks are used for aside from sleep?
- Finding mates
- Food availability
- Predator and competitor avoidance
- Parasite avoidance
- Habitat selection
- Photoperiodism
Photoperiodism
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
Is circadian organization a physiological necessity for life?
No
At the species level, what is the relationship between circadian tau and lifespan?
The greater the deviation from 24 hours, the shorter the lifespan
Proximate causality
The “how” questions; the biological mechanisms
Ultimate causality
The “why” questions
Explain how circadian clocks are used for periodic food sources
Use circadian clock to recognize and remember time of day when food is reliably found
In what animals is the use of circadian clocks for period food sources seen?
Bees, birds, rodents, and fish
Time-place learning is another name for what?
Using circadian clocks for periodic food sources
Explain how circadian clocks are used for competitor avoidance
Use circadian clock to limit activity to day or night to avoid competition
Explain how circadian clocks are used for social coordination
Circadian clock ensures that males and females are active at the same time, increasing chances that they will meet
Explain how circadian clocks are used for predator avoidance
Use circadian clock to avoid predation
What is an example of using circadian clocks for predator avoidance?
Fledging birds
Explain how circadian clocks are used for parasites
- Avoidance of parasites
- Coordination of parasites with vectors
- Avoidance of immune defences
What is an example of how circadian clocks are used for coordination of parasites with vectors?
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
What is an example of how circadian clocks are used for avoidance of immune defences in parasites?
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
Explain the fruit fly eclosion example
Fruit fly eclosion occurs at dawn when humidity is optimal for drying wings
Why are circadian clocks still present in virtually all life forms?
It helps them prepare in advance of daily environmental changes instead of just reacting to them
