Plant and Animal response
Plant growth and photo hormones
Meristems; the region of plant growth. Primary growth occurs at the opical meristems at the tips of roots and shoots.
primary growth; growth of the tips of roots and shoots is divided into three zones: zone of cell division, zone of elongation, zone of differentation
Zone of cell division; this contains the meristematic cells. These cells undergo rapid mitosis to produce new cells
Zone of elongation; the new cells no longer divide; instead they begin to expland and elongate.
Zone of differentation; once at full size, the new cells start to specialise into specific tissues such as xylem, phloem and root hair cells
Important photohormones; Auxins, cytokinins, ethylene, abscisic acid, gibberellins
Auxins (IAA); produced in the shoot and root tips. Promoted elongation in the shoots but inhibits elongation in the roots. Promoted apical dominance (growth of main shoot/root).
Cytokinins; Produced in the roots. Inhibits apical dominance by promoting lateral budding.
Ethylene; Ripens fruit and promotes abscission (detachment of fruit and leaves).
Gibberellins; Breaks seed dominancy and promotes germination
Tropic responses
tropic responses; plant growth response that occurs directional to the stimuli. Can be positive or negation
light; photo
water; hydro
gravity; geo
chemical; chemo
touch; thigmo
sun; helio
electricity; electro
tide; rheo
food; tropo
temperature; thermo
response mecanism (tropic): Tropic responses are due to uneven distribution of Auxins that causes uneven elongation of cells in areas of primary growth
Effect of gravity (tropism); causes it to accumulate in the lower sides of the stem and roots resulting in geotropism
Effect of light; causes auxin to breakdown and accumulate in the shady sides of shoots resulting in phototropism
Effect of water; Auxins are water soluble and accumulate in root cells with a high water concentration resulting in hydrotropism
Transport of auxin; passively through the phloem of actively fromcell to cell. Active transport allows for chemotropic and thigmotropic responses
Nastic response
Nastic responses; nondirectional turgor movement in plants. turgor pressure is the pressure of the contents of the cell pressing against the cell wall and is regulated by the moving water into/out of the cell/vacoule. They are proportion to the stimuli
Most common nastic response; the opening and closing of stomata due to nastic movement of guard cells as they increase and decrease their water pressure.
time frame (Nastic vs Tropic); nastic responses are immediate where as tropic responses occur over a long period of time
reversibility? (Nastic vs Tropic); Nastic reponses are reversable, tropic responses are perminant
response mechanism (nastic); often rely on specialized joint-like thickening of the base of a leaf called a pulvinus
Pulvinus joint; consists of a vasculur core (xylem and phleom) surrounded by a spongy flexible thin walled cell (two types, extensiors and flexors)
extensor vs flexor cells; increase their turgor pressure during leaf ‘opening’ and decrease during ‘closing’. flexor cells do the opposite
How the response is effected (nastic); response is effected due to active transport of sucrose and ions such as potassium and chloride. As these solutes are moved between extensors adn flexors, water flows due to osmosis.
Photoperiodism
Photoperiodism; to ensure best chnace of survival and reproduction, plantvs need to be in sync with seasonal rhythms in temperature, precipitation, pollinator activity and sunlight
stimuli of photoperiodism; many stimuli could be used to detect the season, however, none are as reliabel as the relative lenght of day and night (the photoperiodism)
Critical period; the critical duration of day/night required to stimulate or inhibit flowering
long day plants; only flower if the day lenght exceeds their critical day length. This is generally around 14-16 hours. Long day plants generally flower in late spring and summer
short day plants; only flower if the day length is less than their critical day length. Generally, 8-10 hours. These plants generally flower in winter and autumn
Day Neutral plants; photoperiod had no effect on day neutral plants. They instead generally inhibit flowering after reaching an age/development stage and/or in response to environmental cues such as a period of sustained temperature
Taxes and Kinesis
taxes and kinesis; are simple innate movement in response to stimuli. this allows organisms to move to a favourable environment, giving them a survival advantage
Taxes; directional movements that can be positive of negative
kinesis; non-directional to a stimuli. Instead the rate or movement changes in relation to the ‘comfort zone’ of the organism. Kineses are very common in single-celled organisms
Types of kinesis; orthokinesis and klinokinesis
orthokinesis; changing the speed of movement proportional to the level of stimulus
Klinokinesis; changing the rate of turning proportional to the level of stimulus
Innate vs learned behaviour
Innate behaviours; those that occur instinctively due to genetics
learned behaviour; is developed overtime by modification of behaviour due to previous experience
Homing
Homing; An animals instinctive ability to navigate through unfamiliar territory and return to an original location using navigational cues.
when is homing need; when a species is displaced from their fimiliar territory during migration, mating or even simply during hunting or other regular activity.
Navigational cues/Methods; Position of the sun, Position of the star patterns (celestial navigation), Orientation of Earth’s magnetic field, direction of ocean currents, scents and pheromones (olfraction) and sound
Navigating familiar terrain; many animals use this when navigating, however, this is not considered a typ eof homing as it can only occur in familiar territory.
Migration
migration; the movement of animals from one region to another. True migration involves annual or seasonal movements, or involves a major habitat change as a part of a species life.
How is migration controlled; migration is genetically controlled but initiated by the environment. For migration to occur the adventages must outweigh the disadvantages
Complete migration; all members of the population will migrate
Partial migration; Some members of the population will migrate
Diffrential migration; all members of the population migrate but not necessarily all at the same time or travelling in the same distance. The differences are often due to age or sex.
Irruptive migration; Members of the population do not migrate at all some years and do migrate other years.
Adventages of migration; new/more resources, constant food supply, find mates, greater genetic mixing, better breeding conditions, reduces predation, disease and parasitism, remain in a favourable climate, lead to colonisation of a new year.
limitations of migration; Uses lots of energy, animals can run out of energy before reaching their destination and die, risk of getting lost or eaten on the way.
Migration stimuli; the cues for migration involve complex interactions between internal and external stimuli.
External stimuli; changes in weather, changes in food and water supply, length of day.
Internal stimuli; circannual rhythm (internal calendar), fat reserves, sex maturity.
Rhythms
Rhythms; most environments on earth undergo predicatble fluctations due to the time of day, month (moon phase) and year. Animals have a survival adventage if they can predict, prepare and respond to these fluctuations
Keeping time; rhythms are maintained due to endogenous pacemakers (biological clocks) and exogenous zeitgebers (environmental cues)
Biological clocks: The bodies innate time keeping sytem. Occurs due to complex interaction of certain genes and proteins called a molecular clock. Pressent in almost all tissues in the body. The master clock is a group of 20,000 cells in the anterior hypothalamus called the SCN. This clock maintains circadian rhythm
Entrainment;the process by which a biological clock is affected by environmental cues. Can occur at different levels of organisation from indivdual cells to whole organisms.
Jet lag; When the clock becomes out of sync with the environment you experience jet lag. Synchronization can only be restored with tim eand entrainment by zeitgebers. Humans have a natural biological clock that lasts 24hs and 11mins (± 16mins)
Suprachiasmatic Nucleus (SCN); the Suprachiasmatic Nucleus is located above the chiasma of your optic nerve adjacent to the pineal gland When light enters the eye, special photorecepive cells in the retina detect blue light and send a nerve impulse to the SCN. This signal increases the producation and accomolation of CLOCK and BMAL1 protains
CLOCK and BMAL1;inhibit the secretion of melatonin by the pineal gland preventing sleepyness. They promote the transcripition of period (PER) and cryptochrome (CRY) proteins which inhibits the secretion of metatonin and the transcription of PER and CRY protein leading to wakefulness.
activity patterns
diurnal; active during the day. this provides many advantages for animals that have poor visibility in low light (like humans)
Nocturnal; Active during the night. Advantageous for avoiding predators and competition. In some areas it can be an adventage to avoid the heat.
Crepuscular; Active during twilight (dusk and dawn) adventageous for avoiding the heat while utilising light for activities such as hunting.
Actograms; diagrams/graphs to show animal activity patterns over a period, demonstarting the circadian rhythm of animals.
Purpose of Actograms; Show a period when zeitgeber is present and a period when it is removed, there is useful for determining the relative influence of endogenous (internal) and exogenous (external) factors.
Phase shift; When no zietgebers are present, the organism is siad to be in a ‘free running’ period.If the activity pattern was entirely endogenous, it would remian relatively similar. However, in the absence of environmental cues the activity pattern is likely to drift. The amount of drift is the phase shift.
Ecological organisation
Levels of ecological organisation; 1. organism, 2. population, 3. community, 4. ecosystem, 5. biome, 6. biosphere
population; all the same organisms
community; all the same species within an environment
ecosystem; all the biotic and abiotic factors within an environment
biome; a major biotic community characterised by dominant factors
biosphere; the zone of all life on earth
Interspecific relationships; the way different species within a community interact with each other eg, mutualistic, exploitative, commensalistic, competitive
mutualistuc relationship; benefits both species
exploitative relationship; benefits one species while harming the other
Commensalistic relationship; benefits one species while not impacting hte other
competive relationship; harming both species
symbiosis; used to desciribe a close and long-term interaction between organisms of different species. Symbiotic relationships can be mutualistic, commensalistic or parasitic.