Semester 2: Exam Revision Flashcards
Four Plant Tropisms
Plant phototropism
Geotropism
Negative geotropism
Photoperiodism
What is positive phototropism
Growth of shoots towards light
Geotropism
Growth of roots in response to pull of gravity
Negative Geotropism
Tendency of stems to grow upward, away from force of gravity
Photoperiodism
Response of an organism to seasonal changes in day length
i.e day–night cycle
What are short and long day plants?
- Short day plants: require long nights to trigger flowering
- Long-day plants: flower if nights are short or if the plants are continuously illuminated
5 plant hormones
1) Auxins
2) Gibberellins
3) Cytokinins
4) Abscisic Acid
5) Ethylene
Auxins
- promote growth of anew shoots
- triggers positive phototropism & negative geotropism of shoots
- responsible for apical dominance
What is apical dominance
the main, central stem of the plant is dominant over (i.e., grows more strongly than) other side stems; on a branch the main stem of the branch is further dominant over its own side branchlets.
Gibberellins
- Promote growth (general)
- involved in cell division flowering in some plants, fruit enlargement, seed germination
Cytokinins
- (in presence of auxins) stimulate cell division/differentiation, growth of lateral branches.
What happens if there is more cytokinins than auxins?
Stems and leaves develop more
More auxins than cytokinins
Roots develop
i.e: stimulates cell division, enlargement, tissue differentiation
Abscisic Acid
- Growth inhibiting hormone
- Has opposite role of auxins
- abscission of flowers, fruit, leaves & control of stomata movement
- promotes bud/seed dormancy, increases frost resistance
Ethylene
Increases cellular respiration & the process associated with fruit ripening
I.e: increases break down of starches- triggered by auxins and abscisic acid.
Three types of adaptations and their definition
1) Behavioural: process by which an organism/species changes it’s pattern if action to better suit it’s environment
2) Physiological: systematic response to external stimuli, maintaining homeostasis
i. e.- biological change
3) structural: Physical features - aid in survival/ succeed in environment
temperature regulation and water balance in ectotherms
generally unable to raise their body temperature by internal heat production
temperature regulation and water balance in endotherms
generate heat by internal heat production, maintaining a relatively constant body temperature by regulating heat generation and heat loss to their environment.
•
Metabolism
total of the physical & chemical processes by which energy and matter are made available by an organism for its own use.
Homeostasis
maintenance of a relatively stable internal environment [promoted by negative feedback system] i.e. Stimulus-response mechanisms in which the response produced reduces the effect of the original stimulus response produced reduces the effect of the original stimulus
Thermoregulation
maintenance of core internal temperature
examples of thermoregulation
- Sweating, panting, licking fur, insulating layers to reduce heat exchange with environment [endotherms], altering behaviour, changing blood flow to skin (and heat generating organs) regulate the temperature gradient between the body and environment, altering of SA available for heat exchange
- Heat gained as a product of cellular metabolism and from the environment, e.g. Increased muscular activity, shivering, increased cellular activity, increasing temperature on rates of cellular metabolism
• Water Regulation [OSMOREGULATION]
> process of regulating water potential in order to keep fluid and electrolyte balance within a cell or organism relative to their surrounding.
• Freshwater/Marine fish maintain salt + water balance by regulating water intake and volume of urine produced, and by actively absorbing or secreting salts
• Terrestrial Organisms achieve water balance by regulating water loss/gain i.e. Cellular respiration, e.g. Hopping Mouse - concentrated urine, does not have to drink water
• Neuron (nerve cell)
basic unit of a nervous system; a cell specialised to receive, conduct & transmit information