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REPONSES OF PLANTS AND ANIMALS TO THEIR EXTERNAL ENVIRONMENT - ANIMAL…
REPONSES OF PLANTS AND ANIMALS TO THEIR EXTERNAL ENVIRONMENT - ANIMAL RESPONSES
Homing and Migration
Homing is the ability of an animal to return to its home location after travelling away from it
May travel away from home to find food, resources, meet and mate at breeding site and/or return home to a well resourced location
Returning to breed at the same location provides an adaptive advantage as eggs and hatchlings will be well adapted to the specific conditions of the habitat where they are laid as their ancestors survived the selective pressures at same location
Migration is the regular, mass movement of organisms of the same species usually on a seasonal basis and typically to a predetermined location
Animals will migrate to find food, find shelter and raise young in a safe place
Migration is a large investment in energy - there has to be a survival advantage, otherwise it would be pointless for the organism to do it
Advantages
= animals remains in favourable environmental conditions - increases genetic diversity as individuals from different populations may breed together - abundant food at destination means offspring grow larger and have a high survival rate - population has a constant, year-round supply of food - animals may migrate to areas with fewer predators - diseases, or their vectors, present in one location may not be present in the location they migrate to - migration may lead to the colonisation of new habitats
Disadvantages
= migrants may get eaten by predators during the journey or when they congregate in new habitat - energy expended during migration may mean individual doesn't have sufficient reserves to successfully breed - animals may get lost of die during migration
Migratory behaviour is innate and genetically controlled but in most species it is initiated by the environment
External migration cues
Photoperiod = longer days in summer/shorter days in winter cue to migrate - less sunlight results in lower rates of photosynthesis and therefore less food, may also mean lower temps
Shifting seasons = temp and levels of precipitation change, resulting in distinct wet and dry seasons
Food/water availability = lack of food and/or water force animals to migrate
Internal migration cues
Circadian rhythms = internal calendar in nervous system - can have an innate sense when to migrate without any external stimuli
Fat reserves = low fat reserves may cue to move in search of food or high fat reserves (built up) may cue also
Sexual maturity = hormones may trigger an innate desire to migrate to breeding grounds
Taxes and Kinesis
light/photo - temperature/thermo - gravity/geo or gravi - chemicals/chemo - touch /thigmo - water/hydro - current/rheo - food/tropho
TAXES
movement of a whole organism or cell in reponse to an external directional stimulus
Taxes are innate responses because they are genetic behaviours and performed the same every time, even by animals that are isolated. The behaviours cannot be developed with practise.
+ve taxis is towards stimulus, -ve taxis is away from stimulus
An adaptive advantage is a characteristic of an organism that enables it to survive and reproduce better than other organisms in a population in a given environment; it is the basis for evolution by natural selection
- will be asked about the adaptive adavntage of a taxes reponse and this needs to be included for E
KINESIS
is an innate behavioural response of an organism to an external non-directional stimulus such as humidity or the temperature
Orthokinesis = rate of locomotion is proportional to the tolerance levels of an organism ...in optimum range, movement would be slow - outside this range, the organism is in a zone oh physiological stress and would move more rapidly to seek refuge
Klinokinesis = specific to rate of turning of an organism proportional to the external stimulus - the more phsiological stress an organism is under, the more it will twist and turn in search of a more tolerable environment
Biological Timing Reponses
Organisms have adapted to take advantaged of the daily cycle of light and dark via internal endogenous biological clocks
Biological clocks allow organisms to anticipate environmental changes, before the change happens e.g. a nocturnal animal can return to its burrow before sunrise
Biological clock can be altered or entrained using various environmental cues called zeitgebers
In natural conditions the internal cock must be contiually entrained by environment else the biological rhythm and external rhythm would become unsynchronised as day length changes with seasons
Circadian rhythms
= daily rhythms - cyclic, repeating activity patterns that are often seen in biochemical, physiological and behavioural processes
Free-running period of approx. 24 hours and are endogenous
Diurnal = active when heat loss isn't a risk, easy to see food sources and spot predators
Nocturnal = less likely to suffer dessication with cooler night temperatures with higher humidity, avoids predation by diurnal predators that are reliant upon sight
Crepuscular = avoids predators active only in daylight and darkness (fewer will be around at dawn/dusk), may provide tolerable extremes of heat and cold
Circatidal rhythms
= synchronised by tides and commonly seen in living organisms in intertidal zones
Rhythms aren't affected by wetting - proposed that mechanical agitation from waves, water pressure, changes in temperature or water turbidity may act as zietgebers
Circannual rhythms
= period of around 365.25 days
Seasonal migration, hibernation
Hibernation - lower body temp, sow breathing and heart rate (metabolic processes slow as well) - use very little energy - can go for a whole season without eating if it has eaten enough food during rest of year and stored enough fat
Actograms
= graphs of activity patterms
When organisms kept in constant conditions the period of their rhythm will continue - free-running period...over time rhythm will drift out of synch with rhythm of environment - provides an adaptive advantage to organism
Endogenous rhythm = internal rhythm which involves an internal biological clock - rhytm persists in the absences of external cues (zietgebers_
Having the period of the endogenous rhythm greater than 24 hours ensures that nocturnal animals emerge only once it is dark (and thus safe) even at times when day length increasing
Navigation Techniques
Solar navigation
= sun moves across the sky from east to west, animals are able to use its position to navigate...however over long journeys animals must compensate for the movement of the sun by using some form of biological clock or other navigation mechanism
Magnetic field
= the angel of earth's magnetic field varies with latitude so many animals use this for navigation...strength of field amd local anomalies may also help animals build up a mental map of territory
Landmarks, smells and sounds
= animals may fine tune their orientation based on familiar landmarks and smells when close to home - some animals leave pheromones to follow when they return, some have eco-location (bats, dolphins)
Stellar navigation
= animals travelling at night may orientate themselves to a particular constellation or to a celestial pole - constellations move across sky with time so animals require an internal clock for compensation
Why do organisms need to respond to their environment?
1) find a more favourable environment where they can obtain resources or alternatively to be able to move away from unfavourable environments
2) reduce inter and intra specific competition
3) avoid being eaten - called predation if relates to animal, herbivory is relates to plant
4) find another member of the same, but opposite sex, for reproduction
Adaptive behaviour gives an animal and advantage. Heritable adaptive behaviours evolve through natural selection. Individuals that possess certain genes that cause them to respond appropriately to environmental or physiological cues, will have increased reproductive success resulting in these genes beig passed on to future generations. Adaptive behaviour os crucial in the process of natural selection and thus important in the evolutionary process.
Innate and Learned Behaviours
Innate behaviours
= genetically programmed -
heritable
, encoded in DNA and passed on from one generation to the next -
intrinsic
, present in animals raised in isolation from others -
stereotypic
, performed in the same way each time by each individual -
inflexible
, not modified by development or experience
Learned behaviours
= occur as a result of experience -
non-inheritable
, acquired only through observation or experience -
extrinsic
, absent in animals raised in isolation from others -
adaptable
, capable of modification to suit changing conditions -
progressive
, subject to improvement or refinement through practice