Plant and Animal Responses Flashcards
Circadian Rhythm
- 24 hours (day-night cycle)
- Triggered by light availability
- Types: diurnal, nocturnal, crepuscular
- Advantage: predict daybreak, search for food early, maximise feeding
Circalunar Rhythm
- Approx. 295 days
- Advantage: predict spring tides for full moon, maximising % of successful reproduction
Circannual Rhythm
- Approx. 365
- Triggered by day length
- e.g. migration/hibernation of animals when leaves fall off trees
- Advantage: predict winter, moult summer hair, replace with longer winter hair for increased insulatiohn for colder temperatures
Circatidal Rhythm
- Approx. 12 hours, linked to changes in tides
- Tide in, organisms are submerged = feeding and reproduction
- Tide out, organisms exposed to air, dessication = activity stops
- Advantage: predict incoming tides = feed early etc.
Photoperiodism
Regulation of seasonal activity by day length, controlled by phytochromes
Phytochrome
Controls photoperiodism response, there are 2 types:
- Pr (day) and Pfr (night)
- During the day, Pr absorbs all red light from the sun, which is then converted to Pfr and vice versa
Long day plants
Flower in spring/summer (more Pr) e.g. sunflowers
Short day plants
Flower in autumn/winter e.g. spinach
Day neutral plants
Flower any time of year (not affected by day length)
Advantage of photoperiodism
Plants cannot move to favourable environments so instead change their rate of growth (to synchronise with pollinators)
Exogenous Rhythm
Externally driven (light availability, day length)
Endogenous Rhythm
Internally driven (internal body clock/superchiasmatic nuclei)
Zeitgeber
Environmental cues that reset the internal body clock/superchiasmatic nuclei
Free-running Period
When no zeitgebers are present
Entrainment
Resetting the superchiasmatic nuclei to match the environment
Actogram
Shows activity of organism during the day and changes in the environment
Phase Shifting
When time of activity/inactivity is pushed forwards or backwards
Benefits of biorhythms
- allows for the prediction of events that need a build up of food or reserves (migration)
- synchronisation of internal physiological processes and social activities
Taxis
Directional response either towards or away from a directional external stimulus e.g.
Kinesis
Non-directional response, rate of movement (activity influenced by an external stimulus) e.g.
Klino-kinesis
A change in rate of turning in organism
- Favourable environment = slower rate of turning
- Non-favourable environment = faster
Ortho-kinesis
A change in speed
- Favourable environment = slower
- Non-favourable environment = faster
Migration
Seasonal mass movement of a population from one location to another (for more food, better breeding conditions, away from predators/harmful weather)
Migration timings
Often triggered by biological rhythms (change in day length/climate - exogenous) and the body clock will prepare the animal for migration (endogenous rhythm)
Preparation for migration
Increasing fat layers to increase energy supply for the journey
Benefits of migration
- Remain in favourable temperatures (less energy used on maintaining suitable body temp)
- Constant supply of food (grow larger)
- Better breeding conditions
- Reduction of predation and disease
- Greater genetic mixing
Costs of migration
- Blown off course/non enough energy to complete journey
- Eaten by predators
- Benefits must outweigh costs in order for it to continue
Homing
Organism finds its way home over unfamiliar territory (using scent trails, star/sun compass, visual signs/landmarks)
Nastic Responses
Non-directional movements or ‘responses’ to the intensity of a stimulus e.g.
Tropism
Directional response to a directional external stimulus
- Plant grows towards stimulus = positive tropism
- Away from stimulus = negative tropism
Auxin
Hormone produced in the tips of plant shoots, causes cells to grow longer than normal (elongate)
Auxin in plant roots
Slows growth in the root and curves downwards (in the direction of the force of gravity)
What happens when there is a directional light source? (Auxin)
Auxin diffuses down the dark side of the plant causing the cells on the dark side to elongate whilst the cells on the light side stay the same (plants bend towards light)
Adaptive advantage of negative gravitropism
Growing upwards allows the plant to access sunlight for photosynthesis
Adaptive advantage of positive gravitropism
Growing downwards allows the plant to reach more water/nutrients required for growth
Commensalism
- One species benefits, the other is unaffected
- Benefits tend to come from food, shelter or transport
- Usually large host, small beneficiary
- e.g. birds feeding on insects found on the backs of animals
Mutualism
- Between 2 species, both benefit
- e.g. humans have gut bacteria, they help us digest food and we provide them with a home/food
Exploitation
Between 2 species, one benefits, the other is harmed
Parasitism
One organism living on/inside another species and harming it
Antibiosis
One species releases a substance that harms/kills or inhibits the growth of another species
Herbivory
Type of predation where one animal species feeds of a plant species
Mullarian Mimicry
Several unpalatable species mimic each others signals or colouration (bees, wasps) so predators know to avoid/won’t eat them
Batesian Mimicry
Harmless species imitate poisonous ones for protection against predators
Evolutionary Fitness
- A measure of an organisms reproductive success
- Fitter organisms are better adapted, more likely to survive, reproduce, pass on their genes
Courting (and its benefits)
- Ensures successful mating
- Involves displays, calls, pheromones etc.
- Benefits: species recognision, natural selection and establishing pair bonds
Polyandry
One female competes for many males
Polygyny
One male competes for many females (more common, female bears young)
Polygamy
- Several partners
- Increased genetic diversity BUT less parental care
Monygamy
- 1 male: 1 female
- Parental care shared (less time and energy spent on courting, more on offspring) BUT less genetic diversity
Lek
An area where males perform (often competitive) mating displays to attract female mates
Cooperative breeders
Related non-breeding adults assist raising young, “kin group” + “altruism”
Home Range
- Where an animal will search for food that it can’t find in its territory.
- Animals are vulnerable as it is not actively defended
Territory
Area where animal lives and it actively defends from others
Ecological Niche
Physical/biological conditions a population species faces in its habitat
Gauses Law
“Two species cannot co-exist in the same ecological niche”
Social Hierarchies
- Animals arrange themselves in an order of dominance
- Animals with high rank (alpha) have obvious advantages as they are first to feed and have the choice of mates
Advantages of social hierarchies
- Less fighting; less energy expenditure
- Increased survivability of the species when conditions are difficult/in the presence of predators
- Greater opportunity to locate food
- Non-breeding individuals help to raise others young (altruism)
Advantages of group living
- Better predator detection (more eyes, ears, nose)
- Better at finding resources (co-opporative hunting)
- Easier to find a mate
- Roles given for efficiency, individuals can specialise at roles & do them extremely well for benefit of the group
Disadvantages of group living
- Increased competition for resources, this can cause poor nutrition, less offspring survive
- Increased risk of disease; the closer the individuals get, the more likely they are to contract/spread disease
