responses Flashcards
Taxis
Movement of animals towards (positive) or away from (negative) a directional stimulus
Kinesis
Non-directional response of animals to the magnitude or intensity of a stimulus
Orthokinesis
Change in speed of movement
Klinokinesis
Change in the rate of turning
Light
Photo
Touch
Thigmo
Heat
Thermo
Chemicals
Chemo
Current
Rheo
Gravity
Geo
Exogenous rhythm
Activities controlled only by external cues, stop when there is no cue
Endogenous rhythm
Activities controlled by an internal biological clock. Rhythm continues even in constant conditions with no external cues but may show a phase shift as there is no zeitgeber to entrain the biological clock
Zeitgeber
Environmental cue used to synchronise bio clock to external environment
Entrainment
Resetting of the internal clock using a zeitgeber, needed because day length changes with seasons and latitude
Phase shift
Change in period of rhythm
How to calculate phase shift
change in number of hours / change in number of days
Free running period
Length of rhythm under constant conditions
How to calculate free running period
Add or subtract phase shift from normal rhythm
Circadian
Every day/24 hours
Circatidal
Every 12.5 hours
Circalunar
Every month/29.5 days
Circannual
Every year/365 days
Where are mammals’ biological clocks found in?
The suprachiasmatic nucleus (SCN) in the hypothalamus of the brain
How do biological clocks work (melatonin)?
Receptors in the eyes detect light → signals SCN → signals pineal gland to stop melatonin production → awake
No light → no signal to SCN → continue melatonin production → sleep
Diurnal
Active during the day, inactive at night
Nocturnal
Active during night, inactive at day
Crepuscular
Active during dawn and dusk
Homing
Innate ability of an animal to return home from another location
Migration
Seasonal mass movement of animals from one location to another
Migration triggers
Decrease in photoperiod (most reliable) as can have warm day in winter so trigger migration to occur at the wrong time
Navigation methods (six)
Sun/solar compass
Star compass
Magnetic compass
Landmarks
Scent trail
Ocean currents
Hibernation
Dropping of an animal’s body temperature and heart rate on a seasonal basis to conserve energy. Reduces energy expenditure to allow animal to avoid harsh winter conditions when food resources are scarce
Tropism
Growth of plants towards (positive) or away from (negative) a directional stimulus.
Mechanism of auxin in tropism
Promotes cell elongation in shoot system, inhibits cell elongation in root system
Phototropism
Auxin accumulates on the shaded side
Geotropism
Auxin accumulates on the lower side
Thigmotropism
Auxin accumulates on the untouched side
Explain how tropism works
- Light is detected at the tip. Auxin produced at the tip diffuses down the stem.
- Auxin accumulates on the ___ side of the stem.
- Auxin promotes cell elongation in the shoots and causes cell walls to become elastic. When water enters by osmosis, cells on the ___ side elongate and the difference in cell size causes the stem to grow towards the light.
Nastic
Rapid and reversible movement of plants to a non-directional stimuli and involves changes in turgor pressure.
How does nastic work
- Stimulus signals the pulvinus cells to pump K+ and Cl- ions out of the cell (lower salt conc inside the cell and so higher water conc).
- Forces water out of the vacuoles of the cell by osmosis, causing the vacuoles to decrease in turgidity and the cells become flaccid.
- Plant bends and closes.
What nastic response does Venus flytrap show? Explain pros and cons
Thigmonastic - when fly touches its hairs → traps shut
Pros: gains nutrients from flies so it can live in nutrient poor swamps, no competition
Con - requires energy to carry out this mechanism (active transport to pump K+ and Cl- ions out of the cell), benefits outweigh cons
What nastic response does mimosa show? Explain pros and cons
Thigmonastic - leaves close when touched
Pros: defence mechanism to prevent herbivores from grazing/reduce SA of leaves
Benefits of photonastic
Flowers open during the day and close at night
Prevent pollen loss/damage at night due to cooler temp/dampness
Keeps petals fresh and attractive (good advertising)
No point opening up at night as most pollinators are diurnal
Photoperiodism
Response in plants to the differing ratio of light and dark in a day
What are the two forms of the pigment phytochrome?
Pr / Pred / P660
Pfr / Pfar-red / P725
Conversion of phytochrome during the day
Large amounts of red light during the day, Pr rapidly converts into Pfr
Conversion of phytochrome during night
Low amounts of far-red light, Pfr slowly converts into Pr
Which form is the active form of phytochrome?
Pfr
What is the effect of Pfr on flowering in SDP and LDP?
SDP - inhibits flowering
LDP - promotes flowering
Conditions for SDP to flower
Require low levels of Pfr to flower and therefore, long nights/short days
Flower in winter
Conditions for LDP to flower
Require high levels of Pfr to flower and therefore, short nights/long days
Flower in summer
Critical night length
Period of time that when exceeded, promotes flowering in SDP but inhibits flowering in LDP
How does a flash of light interrupting a dark period affect SDP?
Rapidly converts all Pr back to Pfr, thus preventing flowering
How does a flash of light interrupting a dark period affect LDP?
Induces flowering
Growth or dormancy
Plants and seeds suspend growth when environmental conditions are unfavourable
Vernalisation
Artificial exposure of plants/seeds to low temp to stimulate flowering and germination so that they have time to prepare for spring/summer
Abscission
Detachment of plant parts
Mutualism
Both species benefit (+/+)
Commensalism
One species benefits, one species unaffected (+/o)
Antibiosis
Successful competitor obtains all the resources it requires, while the loser is prevented (usually by chemical means) from resources and therefore excluded from the area
Allelopathy
Form of antibiosis, plant produces allelochemicals that influence the growth, survival and reproduction of other organisms
How does allelopathy work?
Leaves fall → allelochemicals leach into the soil → inhibits growth of competing plants → less competition for nutrients, water, light → increased rates of PS → more glucose for respiration → more energy for growth and reproduction
Con - cost lots of energy to make chemicals
Exploitation
One species benefits, one species harmed (+/-)
What are the three types of exploitation?
Herbivory, parasitism, predation
Predation
One organism (the predator) captures and kills another organism (the prey)
Strategies used by predators
Camouflage, position of eyes,
teeth/claws, speed and strength, hunting as a group
Camouflage
Blend into the background of or disguise to resemble something not of interest
Benefits only one party +/-
Aposematism
Using strong odours, bright colours and warning sounds to signal to the predator the unpalatability or dangerous nature of a prey item
Mimicry
Species evolves to appear similar to another so the predator is unable to tell the two apart
Batesian mimicry
Model is dangerous and unpalatable, harmless and palatable mimic has evolved similar features → predator learns from harsh experience not to eat model, so will avoid anything similar (mimic)
Mullerian mimicry
Two or more poisonous species mimic each other’s warning signals to reinforce deterrent effect to predator
Aggressive mimicry
Predators or parasites share similar features with a harmless model to deceive prey or host
Herbivory
Consumption of plant material by animals
Parasitism
Parasite lives on or within host organism and derives nutrition from it
Brood parasite
Organisms that rely on other species to raise their young.
Manipulates host by having eggs that resemble the host’s eggs (brood mimicry)
Hemiparasite (parasitic plants)
Plant derives some or all of its nutritional requirements from another living plant (eg. mistletoe).
Modified roots, called haustoria, penetrate host, connecting to the xylem or phloem, allowing the hemiparasite to extract water and nutrients from host.
Obligate/holoparasite (parasitoid)
Organism that spends its larval stage in or on another host organism, so it cannot complete its life cycle without exploiting a suitable host.
Feeds on the host as it develops and eventually kills the host
Competition
Fighting for limited resources (eg. food, water, space). Both species are harmed
Gause’s principle
No two species with identical ecological niches competing for the same resources can coexist indefinitely
Intraspecific competition
Members of the same species compete for limited resources
Why is agonistic behaviour used?
Because physical fighting leads to injury or death and expends a lot of time and energy
Territory
An area that is marked and actively defended
Home range
Wider geographical area that contains shared resources for survival
What determines the size of a territory?
Rank
Availability of resources - low resources → bigger territories (but less popn)
Increase in population size → decrease in territory size
Hierarchy
Social rank/established order of individuals in a group of animals
Altruism
Organism endangering itself or forgoing resources to benefit or protect individuals of the same species
Kin selection
Form of altruism towards relatives.
Relatives are individuals that share some genetic material, so when the relatives’ offspring survives, alleles in common can be passed on.
Courtship strategies
Rituals that allow an organism to display their traits/abilities, resulting in sexual selection.
Eg. vocalisation, dances, visual displays, puffing/flapping.
Lek
Temporary territory established for display to attract mates
Sexual dimorphism
Difference in the physical appearance of males and females
Pair-bond
Long term relationship between both parents to help raise their offspring
Less energy expended by each parent, better protection and survival of young
Monogamy
1 male, 1 female
Polygyny
1 male, many females
Polyandry
1 female, many males
Polygynandry/promiscuity
Many males, many females
Oviparous
Produce eggs that hatch (eg. fish)
Viviparous
Develops embryo, results in that birth (eg. humans)
Altricial
Underdeveloped at time of birth, unable to move around on its own
Precocious
Relatively mature and mobile from the moment of birth or hatching
Characteristics of R-strategists (6)
Short lifespan - not much time and energy to expend in reproduction
Large number of small offspring
Low chance of survival as no parental care (many young die, but enough survive)
No or low energy investment in offspring
Reach maturity early
Fast population growth rate
Characteristics of K-strategists (6)
Long lifespan, so large amount of time and energy to expend in reproduction
Small number of large offspring
High chance of survival as lots of nurturing parental care (learning)
High energy investment in offspring
Reach maturity later
Slow population growth rate
