where is the biological clock in our body? how does it effect us?
It is a metaphor referring to your sense of time passing and the affects of aging. It is not any single thing. eg. the menstrual cycle is an obvious biological clock ... one that counts down. There are a lot of vaguely "timed" processes in your body (puberty, pattern baldness, hormones etc) which are collectively referred to as "your biological clock".
You know how it affects you - you are alive.
Arthur Winfree's book "The Geometry of Biological Time" is a terrific read. For example, as Simon mentions, there are numerous timescales to consider: the cell cycle, cardiac rhythms (and more generally, excitable cells), circadian rhythms, menstruation cycles, and the life cycle of slime mold all represent repetitive processes; the process of development from embryo to adult is another carefully regulated temporal process, but one that does not repeat.
Circadian rhythms continue to be an active area of research- it is difficult to quantify influences of genes vs. adaptation. Different organisms (fungi, bacteria, insects, vertebrates, etc) all have oscillatory networks of molecules, but the molecules themselves are not conserved (see for example, Vinod Kumar, "Biological Rhythms"), and the rhythm can show great variability in the face of environmental changes.
To the Op:
Don't forget the Hayflick limit and the effects telomerase has on age
To Simon ( or anyone else who knows the answer):
Would it be correct to assume that the above two factors fall under the phenomena of the 'biological clock'?
Hi Andy, why do you say the circadian molecules are not conserved? Many are, cryptochrome for instance is conserved from plants to animals http://www.ncbi.nlm.nih.gov/pubmed/13678578. A brief insight review article (not very recent, but to the point): Circadian rhythms from flies to human.
To the OP: you need to specify what biological clock you are talking about. For circadian rhythms there is a central clock in the suprachiasmatic nucleus of the brain, which synchronizes peripheral clocks in organs and other tissues.
Just going by my fantastically poor understanding. My reference (Vinod's book, the chapter by Zordan et. al.) says "Although the molecules involved in the clock machinery show heterogeneity across taxa, the mechanisms underlying the basic functioning of biological clocks show substantial conservation at various levels of phylogeny of living organisms." I interpreted this to mean the genes/gene products are not conserved.
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