Bio 3.3

Taxis response

movement of an organism towards or away from an external stimulus - directional respponse

Kinesis response

non-directional movement of an organism in response to stimuli, rate of activity is determined by intensity of the stimulus

orthokinesis

intensity of stimulus impacts speed of response

klinokinesis

intensity of stimulus impacts rate of turning

homing

The ability of an animal to return over unfamiliar territory to its ‘home’ eg. nesting or roosting site

migration

the regular, mass movement of a species from one geographical location to another AND BACK - for favourable conditions eg. feeding, breeding

Endogenous rhythm

internally driven rhythm, involves and internal ‘clock’ that is independent of the external environment, setting the clock (its entrainment) can be due to the environment (zeitgebers)

exogenous rhythm

externally driven rhythm, uncommon to be solely driven by environment

Free-running

when a rhythm continues despite constant environmental conditions - not affected by external cues, gradually drift

daily rhythm

rhythmic activity linked to the night-day cycle

annual rhythm

rhythmic activities associated with the combined effects of the earth orbiting the sun and the earths 23.45degree axial tilt

primary growth

growth in plants occuring the tips of their roots and shoots, meristem cells are found in the growing region and can undergo mitosis, making new cells for growth. These new cells elongate and a vacuole forms, causing rapid growth - GROWTH IN LENGTH

secondary growth

Growth in width, thickening, formation of flowers, fruits, seeds, etc

Dormancy

Seeds/buds become metabolically inactive and await conditions suitable for germination/growth

Vernalisation

Period of cold temperature initiates or accels bud growth or seed germination

Abscissions

process of fruit or leaf fall, done by deciduous trees

Transpiration

movement of water from the roots through the stem to the leaves and out through the stomata

Auxins

plant hormone produced in the tips of roots and shoots (apical meristems), promotes cell elongations and differentiation, promotes secondary thickening of stem and root

Gibberellins

aka “bolting hormone”, plant hormone that breaks the dormancy of seeds and buds, promoting their growth

Cytokinins

Plant hormone that stimulates cell division (mitosis), produced in actively growing regions (roots), promotes growth and development of chloroplasts

abscisic acid (ABA)

plant hormone that promotes seed dormancy, inhibits germination in unfavourable conditions

Ethylene

plant hormone that stimulates fruit ripening, initiates abscission

Tropisms

A response to stimuli that results in the long term growth of a plant towards or away from a stimulus.

Nastic response

Rapid and reversible movement of a plant, direction of movement is independent of direction of stimulus, rate of response is proportional to the intensity of the stimulus.

Photoperiodism

The regulation of seasonal activity by day lenght (photoperiod)

Long-day plants (LDP)

only flower when the photoperiod exceeds a certain value known as the critical day length (CDL), flower in spring/summer

Short-day plants (SDP)

Only flower when the photoperiod is less than the critical cay length (CDL), flower in autumn/winter