Presentation on theme: "TIMING RESPONSES IN ANIMALS Students can…. Explain why there are environmental rhythms Explain why plant and animal behaviours are linked to environmental."— Presentation transcript:
TIMING RESPONSES IN ANIMALS Students can…. Explain why there are environmental rhythms Explain why plant and animal behaviours are linked to environmental rhythms.
Earths Rhythms Yearly orbit of Earth about the sun, together with the tilt of its axis, cause the seasons Seasonal contrast increases with increasing latitude (ie. least contrast is near the equator) Seasons have characteristic abiotic conditions (temp, day length, rainfall etc)
Daily Rhythms, 24 hr Caused by daily rotation of Earth on its axis Produces alternating light and dark periods Length of day depends on latitude and season Sun also affects daily rhythms in temp, humidity, wind
Effects of the moon Moon orbits the earth once per 27.3 days Affects the tides: moons gravitational pull combined with Earths rotation Twice-daily ocean tides Tidal levels vary during moons phases (spring and neap tides) Changes in illumination (light) at night
Environmental Rhythms and Animal Behaviour Most daily and annual animal rhythms are linked to cyclical environmental changes caused by Earths rhythms Includes periods of activity & sleep, feeding & drinking, breeding, migrations, fluctuations in body temp, sensitivity, hormone levels
What are the biological advantages to an animal species of synchronising its activities to Earths rhythms?? Better food supply Avoiding predators Avoiding competitors Finding more favourable environmental condns Avoiding harsh conditions Finding mates or a breeding place Raising young successfully ***ENHANCED SURVIVAL & REPRODUCTION***
Biological Rhythms Animals and plants exhibit all kinds of regularly repeated behaviours eg. activity patterns, reproduction, migration, hibernation EXOGENOUS rhythm: A direct response to environmental cues (external) ENDOGENOUS rhythm: Internally controlled, will continue in absence of environmental cues (involves a biological clock)
BIOLOGICAL RHYTHMS (biozone 188) LEARNING OUTCOMES Explain what BIOLOGICAL RHYTHMS are Explain the ADVANTAGE of these rhythms Explain what a BIOLOGICAL CLOCK is
What is the advantage of having a biological clock? Activity remains in sync with environment Keeps sleep/wake cycles constant Able to predict events (eg. winter, spring) Synchronise breeding stages with others of your species and the seasons Plants: flowers when the bees are out, lose leaves in winter when cold
BIOLOGICAL RHYTHMS Animals and plants exhibit all kinds of regularly repeated behaviours eg. activity patterns, reproduction, migration, hibernation EXOGENOUS rhythm: A direct response to environmental cues (external) ENDOGENOUS rhythm: Internally controlled, will continue in absence of environmental cues (involves a biological clock)
Remaining in sync with environment Biological clocks must be reset at regular intervals This is the purpose of the ZEITGEBER or external timekeeper This is the environmental cue that resets the biol clock ENTRAINMENT is the process of resetting the biol clock
The Human Biological Clock Runs at about a 25.5 hr day But we need it to be synchronised with our environment (a 24hr cycle) Mammals including humans have a master circadian clock in our brain Two tiny groups of cells called the suprachiasmatic nuclei (SCN) in hypothalamus Located behind our eyes, 1/3mm in size
SCN Pineal Gland Melatonin production PROMOTES SLEEP Shuts off melatonin production AWAKE Light stimulus Darkness stimulus In Hypothalamus
Zeitgeber = external timekeeper The light/dark cycle acts as the ZEITGEBER to reset our internal clock to a 24hr cycle Resetting of the clock is called ENTRAINMENT By following the day/night cycle, animals can better exploit the seasonal changes in the environment
The Importance of Melatonin Is the hormone controlling our sleep/wake cycle When produced at night it promotes sleep May help in the timing of onset of reproductive cycles in many species of animals Enhances the immune system More is produced over 24 hrs in the short days of winter than in summer (sleepier in winter?)
Today: Circa- rhythms & Actograms Learn how to read and interpret Actograms Weta as an example
Lots of human daily rhythms BIOZONE Human Biorhythms Susceptibility to alcohol Body temperature Blood pressure Cell divisions in skin Time of labour onset
What are Actograms? An actogram is a special graph Shows the activity of an animal or plant during the day/night and over many successive days. Gives a good picture of when the organism is active at any time. Can use them to monitor changes over time under constant conditions
Actograms show us: Light/dark regime in lab conditions Period = length of one full cycle eg. From start of activity to the next start of activity. The Free-running Period = how long the cycle runs in the absence of all environmental cues Phase-shift = New start time for the activity (eg. 8am start changes to 10am) How much has it shifted? 2 hours later
DAILY RHYTHMS Daily night/day cycle of about 24 hours Three types of activity are seen in animals: 1.Diurnal – mostly active during the day Eg. Humans, honey bees, tui 2.Nocturnal – mostly active at night Eg. Kiwi, owls, bats, moths, kakapo 3.Crepuscular – most active at dawn and dusk eg. Rabbits, mosquitos, wombats
Today: Types of Biorhythms Explain what is meant by circannual, circalunar, semi-lunar, circatidal and compound rhythms Give examples of each of the above rhythms
Environmental rhythms vs. Circa- rhythms Environmental rhythms are daily, annual, tidal, lunar etc Animal rhythms can only be called circadian, circannual etc if they persist under constant conditions in the lab.
NZ Example of a Circatidal Rhythm Chione stutchburyi cockle exhibits clear endogenous circatidal rhythmicity in shell gaping and siphon extension and also in adductor activity occurred at the times of expected high tides
Advantage of the cockles endogenous rhythm being in time with high tides? * avoid dessication at low tide * increased feeding time * increased survival
Circatidal example Fiddler crabs forage during low tide If taken away from the shore, the circatidal activity can persist for 5 weeks
Tidal/lunar cycle animation Remember: the position of the sun and moon generate our tidal patterns each month
Circalunar rhythm example Young salmon migrate downstream Soon they will migrate to the sea At new moon, surge in output of hormone thyroxine Brings about changes in physiology to cope with being in salty water
Circalunar example Marine worms called Palolo worm Spawning (egg laying and sperm releasing) is synchronised by the moon Advantage? Males and females will spawn at the same time = increased reproduction
Example of Semi-lunar rhythm Californian grunion Leaves the sea to deposit its eggs (spawning) in the sand of several beaches, Feb-Sept Spawning only takes place on 3-4 nights after full or new moon (when tides are highest). Eggs buried in sand to develop, will be washed out again during next spring tide in 12 days
Advantages of spawning at spring tide? Eggs deposited high on the sand by high tide so wont be washed away spawning bed is not disturbed by the tides until the next spring tide cycle The eggs have a safe refuge buried in moist sand in which to develop. Increased survival and reproduction
NZ Inanga: Galaxias maculatus Adult life is spent in lowland streams and rivers During spring high tides, ripe adults move up on to the grassy flats of river estuaries, go to areas covered by water only at the spring tides
The eggs develop and usually hatch at the next spring tides that cover the grasses Advantage = reproduction and survival The manner in which the fish are able to perceive and respond to the lunar cycle remains a complete mystery.
Annual Rhythms eg. Reproduction, migration, hibernation Eg. Long-tailed Bat in NZ Hibernates 4-5 months over autumn/winter Reproduces annually in summer months Responding to day/night length
Advantages for the bats? Breeds at the warmest time of year More food around during breeding season Avoids the cold months
Compound Rhythms Animal responds to more than one environmental rhythm Eg. Sandhopper – uses lunar orientation at night, solar navigation during the day.
Palola marine worm Highly synchronised breeding Research shows this is related to not only the moons phases, but also solar, daily and tidal rhythms.
PLANT TIMING RESPONSES Some plants exhibit rhythmic activity DAILY RHYTHMS: eg. Opening/closing of some flowers such as night-scented jasmine Eg. Leaf movements – the prayer plant leaves move to an erect position at night, horizontal during the day.
Plant rhythms…. ANNUAL RHYTHMS: Eg. Production of flowers, loss of leaves in autumn, germination of seeds Usually in response to change in light/dark hours
WHATS THE PURPOSE? Plants synchronise with animal activity – Eg. Open flowers and secrete nectar when animal pollinators are active in daytime – Production of flowers coincides with the life cycles and activity of animal pollinators
PHOTOPERIODISM AND FLOWERING PHOTOPERIODISM: the regulation of activity by the length of daylight (the photoperiod) Photoperiod detected by leaves Flowering is induced by the length of the photoperiod
Plants are in 1 of 3 groups: Short Day Plants need a period of long nights before they can flower (ie. They need a photoperiod of less than a certain critical day length) Long day plants need a period of short nights before they can flower Day Neutral Plants flower independently of the length of photoperiod