Semester 2: Exam Revision

Question 1

Four Plant Tropisms

Answer 1

Plant phototropism
Geotropism
Negative geotropism
Photoperiodism

Question 2

What is positive phototropism

Answer 2

Growth of shoots towards light

Question 3

Geotropism

Answer 3

Growth of roots in response to pull of gravity

Question 4

Negative Geotropism

Answer 4

Tendency of stems to grow upward, away from force of gravity

Question 5

Photoperiodism

Answer 5

Response of an organism to seasonal changes in day length

i.e day–night cycle

Question 6

What are short and long day plants?

Answer 6

• Short day plants: require long nights to trigger flowering

- Long-day plants: flower if nights are short or if the plants are continuously illuminated

Question 7

5 plant hormones

Answer 7

1) Auxins
2) Gibberellins
3) Cytokinins
4) Abscisic Acid
5) Ethylene

Question 8

Auxins

Answer 8

• promote growth of anew shoots
• triggers positive phototropism & negative geotropism of shoots
• responsible for apical dominance

Question 9

What is apical dominance

Answer 9

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.

Question 10

Gibberellins

Answer 10

• Promote growth (general)

- involved in cell division flowering in some plants, fruit enlargement, seed germination

Question 11

Cytokinins

Answer 11

• (in presence of auxins) stimulate cell division/differentiation, growth of lateral branches.

Question 12

What happens if there is more cytokinins than auxins?

Answer 12

Stems and leaves develop more

Question 13

More auxins than cytokinins

Answer 13

Roots develop

i.e: stimulates cell division, enlargement, tissue differentiation

Question 14

Abscisic Acid

Answer 14

• Growth inhibiting hormone
• Has opposite role of auxins
• abscission of flowers, fruit, leaves & control of stomata movement
• promotes bud/seed dormancy, increases frost resistance

Question 15

Ethylene

Answer 15

Increases cellular respiration & the process associated with fruit ripening

I.e: increases break down of starches- triggered by auxins and abscisic acid.

Question 16

Three types of adaptations and their definition

Answer 16

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

Question 17

temperature regulation and water balance in ectotherms

Answer 17

generally unable to raise their body temperature by internal heat production

Question 18

temperature regulation and water balance in endotherms

Answer 18

generate heat by internal heat production, maintaining a relatively constant body temperature by regulating heat generation and heat loss to their environment.
•

Question 19

Metabolism

Answer 19

total of the physical & chemical processes by which energy and matter are made available by an organism for its own use.

Question 20

Homeostasis

Answer 20

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

Question 21

Thermoregulation

Answer 21

maintenance of core internal temperature

Question 22

examples of thermoregulation

Answer 22

• 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

Question 23

• Water Regulation [OSMOREGULATION]

Answer 23

> 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

Question 24

• Neuron (nerve cell)

Answer 24

basic unit of a nervous system; a cell specialised to receive, conduct & transmit information

Question 25

• Sensory

Answer 25

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

Question 26

Interneuron

Answer 26

local circuit neuron of the central nervous system that relays impulses between sensory anf motor neuron.

Question 27

Motor

Answer 27

neurons which activate muscle cells, transmit messages from brain through spinal cord

Question 28

Synapses

Answer 28

specialised region where information is communicated from a nerve cell to another nerve cell or to an effector cell such as muscle

Question 29

Thermo-receptors,

Answer 29

sensory nerve ending in a sensory cell sensitive to changes in temperature

Question 30

Negative Feedback

Answer 30

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

Question 31

Tolerance Range

Answer 31

range of environmental conditions (e.g. Temperature) that an organism can survive in

Question 32

Primary Productivity

Answer 32

rate at which converters convert light energy to chemical energy as new plant growth [plant biomass]

Question 33

Net Primary Productivity

Answer 33

rate of accumulation of producer tissue

Question 34

Biomass

Answer 34

amount of material that accumulates at a trophic level (measured as dry weight per unit area)

Question 35

• Ecological Pyramid (Trophic Levels)

Answer 35

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

Question 36

Bioaccumulation:

Answer 36

concentration of substances such as toxins along food chains in ecosystems

Question 37

Food Web

Answer 37

series of interacting food chains

Question 38

Food Chain

Answer 38

organisms linked together by their feeding relationships

Question 39

Trophic Levels

Answer 39

a group of organisms that forms one link in a food chain, consisting of producers, consumers or decomposers

Question 40

Biological Agent

Answer 40

: an organism (e.g. Natural predator or parasite) that is used in the biological control of a pest species

Question 41

Biological Control

Answer 41

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

Question 42

Limiting Factor

Answer 42

any condition that limits the abundance or distribution of an organism

Question 43

Carrying Capacity [of an ecosystem]

Answer 43

] is the maximum population that can be sustained before organisms run out of environmental resources

Question 44

Succession: Primary and Secondary succession

Answer 44

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.

Question 45

Nitrification

Answer 45

conversion of organic nitrogenous compounds that cannot be used by plants into inorganic compounds (nitrates) which can be, converted by soil-borne bacteria

Question 46

• Nitrogen Cycle

Answer 46

• (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

Question 47

Nitrogen Fixation

Answer 47

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

Question 48

Phosphorus: a slow cycle; What?

Answer 48

• 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

Question 49

Phosphorus Cycle: circulation of phosphorus through the environment

Answer 49

• 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

Question 50

Summary of the Phosphorus cycle

Answer 50

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]

Question 51

Water Cycle:

Answer 51

describes circulation of water through ecosystems • Water being essential for life, organisms on land rely on water cycling between the oceans and the atmosphere

Question 52

The global water cycle

Answer 52

• 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