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1 BIOLOGICAL CLOCKS BIOLOGICAL CLOCKS

1 BIOLOGICAL CLOCKS. 2 All organisms respond to different cycles. They respond to: All organisms respond to different cycles. They respond to: 1) annual

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Page 1: 1 BIOLOGICAL CLOCKS. 2 All organisms respond to different cycles. They respond to: All organisms respond to different cycles. They respond to: 1) annual

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BIOLOGICAL CLOCKSBIOLOGICAL CLOCKS

Page 2: 1 BIOLOGICAL CLOCKS. 2 All organisms respond to different cycles. They respond to: All organisms respond to different cycles. They respond to: 1) annual

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All organisms respond to All organisms respond to different cycles. They respond different cycles. They respond to:to: 1) annual cycles, with the 1) annual cycles, with the

changing of the seasons;changing of the seasons; 2) daily cycles (night and day)2) daily cycles (night and day) 3) lunar cycles (monthly cycles)3) lunar cycles (monthly cycles) 4) tidal cycles (related to the tides)4) tidal cycles (related to the tides)

Biological timing responses

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Synchronisation with the cyclesSynchronisation with the cycles

It is advantageous for an It is advantageous for an organism to be in sync with organism to be in sync with these cycles in it’s environment. these cycles in it’s environment.

Important events such as Important events such as mating, germination, migration mating, germination, migration are triggered by different stimuli are triggered by different stimuli which can be endogenous or which can be endogenous or exogenous.exogenous.

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Exogenous RhythmsExogenous Rhythms

When a rhythm is in direct response When a rhythm is in direct response to an environmental cue it is said to to an environmental cue it is said to be exogenous. be exogenous.

Examples include day length, Examples include day length, temperature, the height of tides.temperature, the height of tides.

An example of an exogenous An example of an exogenous biological rhythm is the hopping of biological rhythm is the hopping of sparrows on a perch when a light is sparrows on a perch when a light is turned on. turned on.

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Endogenous RhythmsEndogenous Rhythms

Endogenous rhythms are set by Endogenous rhythms are set by an internal clock (biological an internal clock (biological clock).clock).

They will persist even in the They will persist even in the absence of environmental cues.absence of environmental cues.

Examples include preparing for Examples include preparing for winter by storing food, animals winter by storing food, animals coming on heat, solar coming on heat, solar navigation.navigation.

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Resetting the biological clockResetting the biological clock

To remain in synchrony with the To remain in synchrony with the environment, biological clocks need environment, biological clocks need to be reset at regular intervals. This to be reset at regular intervals. This process is called process is called entrainment.entrainment.

The environmental cue that resets The environmental cue that resets the biological clock is called the the biological clock is called the zeitgeberzeitgeber (“time giver” in German) (“time giver” in German)

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Look at page 191 BiozoneLook at page 191 Biozone

Read through the human Read through the human biological clock and answer the biological clock and answer the pages on 192pages on 192

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PeriodPeriod

The period of a rhythm is the The period of a rhythm is the length of one cycle of the length of one cycle of the rhythm.rhythm.

In this graph In this graph the period of the the period of the cycle is about cycle is about 24 hours.24 hours.

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Types of rhythms/cyclesTypes of rhythms/cycles

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Circadian CyclesCircadian Cycles

A circadian cycle has a A circadian cycle has a periodperiod of of about 24 hours. In other words it is about 24 hours. In other words it is about 24 hours long (one day).about 24 hours long (one day).

Examples of circadian cycles in Examples of circadian cycles in humans include the wake/sleep humans include the wake/sleep cycle, body temperature changes, cycle, body temperature changes, and heart rate (the last two drop at and heart rate (the last two drop at night).night).

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Patterns of Activity within Patterns of Activity within Circadian CyclesCircadian Cycles Diurnal - mostly active during Diurnal - mostly active during

the day, inactive at night. Eg. the day, inactive at night. Eg. Humans, bees.Humans, bees.

Nocturnal – active at night, Nocturnal – active at night, inactive during the day.inactive during the day.

Crepuscular – active at dawn Crepuscular – active at dawn and dusk. Eg rabbits and and dusk. Eg rabbits and mosquitoes.mosquitoes.

Arrhythmic – no regular patternArrhythmic – no regular pattern

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Circatidal cyclesCircatidal cycles

A circatidal cycle is about 12.5 A circatidal cycle is about 12.5 hours long (one tidal cycle).hours long (one tidal cycle).

Circatidal cycles affect marine Circatidal cycles affect marine organisms, particularly those organisms, particularly those which live on shorelines. which live on shorelines. Examples include feeding cycles Examples include feeding cycles for shellfish and rock pool for shellfish and rock pool animals.animals.

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Animals showing circatidal Animals showing circatidal cyclescycles

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Circalunar (circamonthly) Circalunar (circamonthly) CyclesCycles A circalunar cycle is about 29 days A circalunar cycle is about 29 days

long (one lunar month).long (one lunar month).

Because the Because the position of the moon position of the moon and sun generate and sun generate tidal patterns, they tidal patterns, they can affect marine can affect marine organisms.organisms.

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Breeding in grunionsBreeding in grunions

Grunions are small fish that spawn Grunions are small fish that spawn on land. From April to June, when a on land. From April to June, when a spring tide occurs (3 or 4 times), the spring tide occurs (3 or 4 times), the fish squirm onto the beach at high fish squirm onto the beach at high tide. Female releases her eggs in tide. Female releases her eggs in sand and the male wraps around her sand and the male wraps around her to release the sperm. They then to release the sperm. They then catch the out-going tide. 15 days catch the out-going tide. 15 days later, at the next spring tide, the later, at the next spring tide, the young grunions have hatched and young grunions have hatched and catch a wave back out to sea.catch a wave back out to sea.

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Circaannual CyclesCircaannual Cycles

A circaannual cycle is about 365 A circaannual cycle is about 365 days long (one year)days long (one year)

Examples of annual cycles:Examples of annual cycles: Reproduction of animals and plantsReproduction of animals and plants Hibernation in animalsHibernation in animals MigrationsMigrations Dormancy of seedsDormancy of seeds Leaf fall (abscission)Leaf fall (abscission)

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Hibernation – an example of a Hibernation – an example of a circaannual cyclecircaannual cycle Some animals survive over winter Some animals survive over winter

by slowing down their metabolism by slowing down their metabolism and hibernating.and hibernating.

The American Woodchuck changes:The American Woodchuck changes:

1)1) it’s heart beat from 80/min to 4-it’s heart beat from 80/min to 4-5 /min5 /min

2)2) it’s temperature from 37it’s temperature from 37ººC to 3C to 3ºC.ºC.

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Aestivation = summer hibernationAestivation = summer hibernation

When the weather When the weather gets too hot, some gets too hot, some organisms hibernate organisms hibernate in summer. in summer. Earthworms burrow Earthworms burrow deep into the deep into the soil,coil into a knot, soil,coil into a knot, and secrete a and secrete a mucous over mucous over themselves to stay themselves to stay moist.moist.

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Photoperiodic responses = Photoperiodic responses = photoperiodismphotoperiodism

In most cases the cue which triggers In most cases the cue which triggers these cycles is the change in day these cycles is the change in day length. We call these length. We call these photoperiodicphotoperiodic responses.responses.

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Free running periodFree running period

The free running period of a The free running period of a cycle is the length of one cycle cycle is the length of one cycle in the absence of environmental in the absence of environmental cues.cues.

For example: If people live in an For example: If people live in an environment of constant light, environment of constant light, temperature etc, their free temperature etc, their free running period is more than 24 running period is more than 24 hours (24 hours, 42 mins).hours (24 hours, 42 mins).

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Phase shiftPhase shift

When the onset of the period of the When the onset of the period of the rhythm is changed (either earlier or rhythm is changed (either earlier or later) we have a phase shift.later) we have a phase shift.

A phase shift occurs when you travel A phase shift occurs when you travel around the earth into a different time around the earth into a different time zone – this leads to Jet Lag.zone – this leads to Jet Lag.

Phase shifts can be induced Phase shifts can be induced artificially in the laboratory by artificially in the laboratory by controlling the light and dark periods controlling the light and dark periods that an organism experiences.that an organism experiences.

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Do pages 188-192 biozone. Do pages 188-192 biozone. Look through first.Look through first.

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ActogramsActograms

Often when Often when plotting activity plotting activity of animals on of animals on an actogram we an actogram we place two days place two days next to each next to each other. other.

This makes it This makes it easier to read.easier to read.

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Working out free running Working out free running periodperiod 1. Work out when the first period of activity finishes 1. Work out when the first period of activity finishes

(nearest ½ hour)(nearest ½ hour) 2. Count down 10 days2. Count down 10 days 3. Work out when the 103. Work out when the 10thth period of activity finishes period of activity finishes

(to nearest ½ hour)(to nearest ½ hour) 4. Work out the difference between these two times4. Work out the difference between these two times 5. Convert into minutes to work out the avg time 5. Convert into minutes to work out the avg time

gained/lost over 24 hoursgained/lost over 24 hours 6. Add or subtract from 24 hours to work out free 6. Add or subtract from 24 hours to work out free

running period. running period.

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