Lesson 10: Biological Rhythms Flashcards
biological rhythm
is comprised of one or more biological events that
1.) reoccur in time
2.) in a repeated order and
3.) with a repeated interval between occurances
what do animals do on a daily basis
- biological rhythms are the ways that organims adapt and live with the ENVIRONMENT RHYTHMS around them - such as the spin of the earth, the movemnet of the earth around the sun, and the movement of the moon around the earth
what generates biological rhythms
- biological clocks (the term for the internal physiological systems that track the enviornmental rhythms) that often tube the rhythm to the environment
animals often show multiple rhythems at the same time
paper trace of kangeroo rat activity over several months - a black mark indicates that the rat has entered a feeder
- for the rats, the year seemed divided into 3 phases
November through march:
the rats were nocturnal ( a cicadian rhythm) and showed a lunar rhythm as well
APRIL AND MAY: lunar rhythm was lost
SUMMER: the circadian rhythm delcined
- becaudr the entire rhytnm repeats each year, there is a circannual rhythem as well
circannual rhythm
repeats each year
multiple rhythms in palolo worms allow coordination and spawnng behavior
- the marine worms of south pacific produce along string of reproductive segments loaded with eggs or sperm
- when time to spawn, the reproductive portion (called the epitoke) swims away
timing is important so that eggs and sperm are released into the water at the same time
- so -
- the epitokes all arrive at dawn (circadian rhythm) on the morning of the last quarter moon (lunar rhythm) during Oct, Nov, Dec (the breeding season - circannual rhythm)
naked mole rats
live their entire lives undergroudn in a dry tropical climate
- because light and temperature don’t fluctuate, there is not rhythm of activity
fiddler crab tidal rhythm
- fiddler crabs feed on prey found on mud flats
- during high tide when the mud is covered with water, they hid in burrows
- they need to be in the burrows before the high tide arrives – so they have a tidal rhythm
costa rica fiddler crabs
- in costa rica, crabs of the same species are found on both caribbean and the pacific coasts
- in each place, the craps habe tidal rhythms that match the local tides
- if transplant crabs from caribbean coast to the pacific coast, let them hang out for 5 days and then measure rhythem in lab wihout tides, the transplants now match the pacific coast tidal pattern
entrainment of rhythm in telogryllus crickets
- male crickets typically start singing a few hours before sunset and stop a few hours before sunrise
- if you bring such a cricket into the lab and keep constant light, then its activity pattern will be offset each day because the natural rhythm is about 25 hours long
upper graph: activity pattern in constant light - offest each day because the natural rhythm is about 25 hours long (unentrained or free-running rhythm)
lower graph: entrainment of activity pattern to 24 hours when given a regular 12 hours of light and 12 hours of dark (entrained rhythm)
entrainment of circannual rhythm in golden mantled ground squirrel
newborn squirrels were captured in the spring and raised in different conditions
1.) normal light cycle - matching the outdoors environment both on a daily and seasonal basis
2.) constant din light - no light cues
In both cases, temperature was held at a constant cool temperature 24/7 and food was provided constantly so no cues from social interactions with caretakers or from meal times
RESULTS
- the results when entrainment cues are removed: each individual showed its own rhythm that was approximately one year long, but not in tube with the actual solar cycle
- controls were tuned to the solar year
social cues in anole circannual rhythm
- in males, growth of testes begins in spring and depends on increasing temperature
- ovaries in females also grow back in spring - but seemingly not because of temperature
Females were kept in the following conditions:
alone - slow ovarian growth
normal males: rapid growth
castrated males: slow growth
possible explainations for anoles
1.) normal males provide a chemical cue (a pheromone that is lost when testes removed)
2.) normal males provide a social cue based on courtship behavior (which is lost if there are no testes)
females were then kept in the following conditions
- alone: slow growth
- normal males: rapid growth
- castrated males - slow growth
- dewlapless males - slow growth
time sense of bees
- bees have the ability to learn what time of day differemnt flowering plants are blooming and have highest nectar supplies
- experiments show that they can distinguish time intervals as short as 15 minutes
- accuracy of the arrival seems to depend on an internal bioloogical clock related to metabolic rate
– if you slow it down by chilling or exposing the bee to CO2 then the bee’s sense of time is off
– suggests existence of BIOLOGICAL CLOCK
like other sorts of behavior, biological rhythms are affected by
genes and hormones and are generated by the nervous system
