Biological clocks Flashcards
(24 cards)
What are the main types of biological clocks mentioned?
Segmentation clock (development), Epigenetic clock (aging), Molecular clock (evolution), Circadian clock (daily rhythms).
What does ‘circadian’ mean?
Circa-dian means ‘approximately one day’ (from Latin: ‘circa’ = about, ‘diem’ = day).
Where are circadian clocks found in the body?
In every cell; they are gene-protein oscillators that generate daily rhythms.
What environmental cues synchronize circadian clocks?
Light and food are primary zeitgebers (temporal cues).
What evidence shows circadian rhythms persist without environmental cues?
Time-isolation studies in bunkers showed sleep/wake cycles continued without external time cues.
Give examples of human circadian rhythms.
Melatonin levels, core body temperature, blood transcriptome, saliva metabolome.
What organisms have circadian clocks?
Circadian clocks are found across all kingdoms of life, including bacteria, plants, fungi, and animals.
What are some circadian rhythms observed in plants?
Leaf movement, germination, growth, stomatal movement, gas exchange, photosynthesis, flower opening, fragrance emission.
What behavior in honeybees involves circadian rhythms?
Time-compensated sun compass navigation.
What is the adaptive advantage of having a circadian clock?
Organisms with circadian clocks are better able to anticipate daily environmental changes and outcompete those without.
What happened in experiments with cyanobacteria regarding clock speed?
Strains with clock cycles matching the environment’s day length outcompeted those with mismatched clocks.
Do circadian rhythms show convergent evolution?
Yes, molecular circadian oscillators appear to have evolved multiple times across different kingdoms.
What geophysical cycles are associated with biological clocks besides the day-night cycle?
Tides (circatidal clock), lunar cycles (circalunar clock), and seasons (circannual clock).
What is the function of circalunar clocks in animals?
They help time reproduction with the moon’s cycle.
Which organism is a model for studying circalunar clocks?
The marine midge Clunio marinus.
Where is Clunio marinus typically found?
In the intertidal zones of the European Atlantic coast, mainly at rocky coasts.
How is adult emergence in Clunio marinus regulated?
By both circadian and circalunar clocks.
What is unique about Clunio marinus regarding biological clocks?
It is the only known organism with circalunar timing adaptation.
How do timing traits vary geographically in Clunio marinus?
Both circadian and circalunar emergence times are locally adapted and genetically determined.
What is allochrony?
Reproductive isolation based on differences in timing, contributing to sympatric speciation.
What is a ‘magic trait’ in evolutionary biology?
A trait that affects both ecological divergence and assortative mating, promoting speciation.
How does lunar emergence timing function as a magic trait in Clunio marinus?
It directly influences reproductive timing, enabling sympatric speciation.
What is significant about some Clunio populations regarding lunar timing?
Some populations have lost lunar timing altogether.
What does the study of Clunio marinus reveal about biological clocks?
It illustrates how internal clocks adapt to geophysical cycles and can drive ecological and evolutionary change.
