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
• Sensory
an afferent (conductive) nerve conveying impulses that are processed by the central nervous system so as to become part of the organism’s perception of self and its environment
Interneuron
local circuit neuron of the central nervous system that relays impulses between sensory anf motor neuron.
Motor
neurons which activate muscle cells, transmit messages from brain through spinal cord
Synapses
specialised region where information is communicated from a nerve cell to another nerve cell or to an effector cell such as muscle
Thermo-receptors,
sensory nerve ending in a sensory cell sensitive to changes in temperature
Negative Feedback
involve either nervous or hormonal systems to promote stability of internal environment, stimulus-response mechanisms in which the response produced reduces the effect of the original stimulus. I.e. The response provides feedback that has a negative effect on the stimulus
Tolerance Range
range of environmental conditions (e.g. Temperature) that an organism can survive in
Primary Productivity
rate at which converters convert light energy to chemical energy as new plant growth [plant biomass]
Net Primary Productivity
rate of accumulation of producer tissue
Biomass
amount of material that accumulates at a trophic level (measured as dry weight per unit area)
• Ecological Pyramid (Trophic Levels)
diagram showing the decline in energy or the mass of plant and animal tissue (biomass) at each trophic level in a food web
• Cow eats food/grass: 30% lost as heat, 10% for growth, 60% not digested
• As energy transfers along a food chain [producers > herbivores > carnivores] there is a decline in the amount of energy/biomass available for consumption, 10% energy of one trophic level appears in the next
• Decline of energy responsible for the limited length of food chains to four or five trophic levels
Bioaccumulation:
concentration of substances such as toxins along food chains in ecosystems
Food Web
series of interacting food chains
Food Chain
organisms linked together by their feeding relationships
Trophic Levels
a group of organisms that forms one link in a food chain, consisting of producers, consumers or decomposers
Biological Agent
: an organism (e.g. Natural predator or parasite) that is used in the biological control of a pest species
Biological Control
the use of a natural agent such as a predator or parasite to limit and control the grow of a pest species, in some cases the controlled population of a pest also in turn controls the biological agent
Limiting Factor
any condition that limits the abundance or distribution of an organism
Carrying Capacity [of an ecosystem]
] is the maximum population that can be sustained before organisms run out of environmental resources
Succession: Primary and Secondary succession
orderly sequence of change in an ecosystem, in which one biological community is gradually replaced by another as the environment changes
• Primary Succession: commences with the colonisation of a bare area, which has not been colonised before
• Secondary Succession: follows disturbance of an existing biological community.
Nitrification
conversion of organic nitrogenous compounds that cannot be used by plants into inorganic compounds (nitrates) which can be, converted by soil-borne bacteria
• Nitrogen Cycle
- (1) inorganic nitrogen compounds are taken up by plants
- (2) converted into organic compounds, ingested by animals that eat the plants
- (3) organic nitrogen returned to soil/water in animal wastes or by death + decomposition of plants and animals
- (4) soil-borne bacteria convert the organic nitrogen compounds into inorganic compounds, some is lost to the atmosphere in gases
Nitrogen Fixation
conversion of atmospheric nitrogen into nitrogenous compounds that can be used by plants. [specialised cyanobacteria, especially Rhizobium bacteria that live symbiotically in the roots of legumes
Phosphorus: a slow cycle; What?
• Phosphorus is required in greater amounts than nitrogen by organisms - therefore, more likely to limit plant & animal growth, as less abundant than nitrogen, cycles slowly through ecosystems
Phosphorus Cycle: circulation of phosphorus through the environment
• weathering of rocks releases phosphorus into the soil and water • phosphates dissolved in the soil are absorbed by the plant roots • animals eat the plants (passes through food chains) • the plants and the animals eventually die, their decomposition returning phosphates to the soil i.e. The non-living part of the ecosystem • the phosphorus in the soil may again be taken up by plants or is washed away/runs off into the ocean, here some of it precipitates as marine sediments • these marine sediments are compressed into rock, uplifted and exposed to weathering, whereby the cycle may begin again
Summary of the Phosphorus cycle
phosphorus is released into soil & water through weathering of rocks, taken up by plants > eaten by animals, their decomposition returns phosphorus to the soil, where it may be trapped by the formation of new rocks (completing the cycle) or reabsorbed by plants]
Water Cycle:
describes circulation of water through ecosystems • Water being essential for life, organisms on land rely on water cycling between the oceans and the atmosphere
The global water cycle
- Water evaporates from the oceans, moves in the atmosphere over land and falls as precipitation - Some water evaporates again, a small amount becomes stored in large lakes etc but most runs off the land into the rivers and returns to the ocean • Local ecosystems do not generally experience cycling of water, but rather tends to flow through ecosystems > most water evaporates back into the atmosphere or runs off the land & moves elsewhere
