mistakes

Question 1

adaptations of phloem (sieve tube)

Answer 1

• sieve plate with sieve pores - allows for continuous movement
• cellulose cell wall - strengthens wall to withstand hydrostatic pressure
• no nucleus, vacuole or ribosome - maximise space for translocation
• thin cytoplasm - reduces friction to facilitate movement

Question 2

adaptations of phloem (companion cells)

Answer 2

• nucleus and other organelles present - provides metabolic and genetic support to sieve tube elements, helping w loading and unloading
• transport proteins in plasma membrane - moves assimilates into and out of sieve tube elements
• large numbers of mitochondria (provide ATP for active transport)
• plasmodesmata - allows organic compounds to move from companion cells to sieve tube elements

Question 3

explain what the Rf values represent in chromatography

Answer 3

equation
- depends on relative solubility of the pigment
- each pigment has a specific Rf value
- can be used to identify different pigments

Question 4

give 3 examples of photosynthetic pigments

Answer 4

chlorophyll, carotene, xanthophyll

Question 5

compare and contrast exchange of energy with nutrient cycling in ecosystems

Answer 5

both
- flow through ecosystems
- both used for metabolism and growth

energy:
- source is the sun
- lost as heat between each trophic level
- is not recycled

nutrients
- source is soil/rocks
- escape food chains as litter/feces
- recycled

Question 6

causes of eutrophication

Answer 6

• excess nutrients in an aquatic system
• natural runoff from soil/erosion/weathering of rocks
• runoff of fertilisers
• partially treated sewage

Question 7

explain what information a pyramid of energy provides about an ecological community

Answer 7

shows the amount of energy at each trophic level measured over a given period of time. The units are energy per area per time. The width/size of each bar represents the amount of energy the bottom level represent the producers, and subsequent levels represent consumers. Each level should be roughly one tenth of the size/10 % of the preceding
level as the energy that enters a community is ultimately lost as heat/in
respiration.

Question 8

explain why viral diseases cannot be treated using antibiotics

Answer 8

• viruses are not living
• viruses lack metabolism
• antibiotics target metabolic pathways

Question 9

describe the origin of eukaryotic cells according to the endosymbiotic theory

Answer 9

a. mitochondria and chloroplasts are similar to prokaryotes ✔
b. host cell took in another cell by endocytosis/by engulfing in a vesicle ✔ Allow “taking in” in place of “engulfing”
c. but did not digest the cell/kept the ingested cell alive, developing a symbiotic/mutualistic relationship between engulfed and host cell ✔
d. chloroplasts and mitochondria were once independent/free-living organisms ✔
e. DNA loop in chloroplast/mitochondrion
g. double membrane around chloroplast/mitochondrion ✔
h. 70s ribosomes in chloroplast/mitochondrion ✔

Question 10

explain how insects secrete nitrogenous waste

Answer 10

a. excreted as uric acid ✔
b. excretion by Malpighian tubules ✔
c. nitrogenous waste/ammonia «accumulates» in hemolymph ✔
d. nitrogenous waste/ammonia absorbed by Malpighian tubules ✔
e. ammonia converted to uric acid ✔
f. conversion to uric acid requires energy/ATP ✔
g. high solute concentration in Malpighian tubules due to active transport of ions/Na+/K+ into Malpighian tubules ✔
h. water absorbed by osmosis flushes uric acid/nitrogenous waste to «hind» gut ✔
i. water/ions reabsorbed from the feces and returned to hemolymph ✔
j. uric acid precipitates/becomes solid/forms a paste so can pass out with little water ✔
k. uric acid excreted/egested with the feces ✔
l. water conservation/osmoregulation
m. uric acid is non-toxic ✔

Question 11

draw labelled diagrams to show a condensation reaction between two amino acids

Question 12

outline a reason in which reef building corals are affected by increasing atmospheric carbon dioxide

Answer 12

• corals have exoskeletons made of calcium carbonate
• CaCO3 shells dissolve in acidic conditions
• high co2/acidic conditions reduce availability of CaCO3 for forming shells

Question 13

explain how aphid stylets can be used to study the movement of solutes in plant tissues

Answer 13

a. aphids tap into phloem with their stylets «to use sap as a food source»
b. plants grown in radioactive CO2/14CO2 incorporate it into carbohydrate
c. phloem contents/sap/fluid flows through the stylet
d. aphid body severed/cut from stylet «after stylet inserted into phloem»
e. analyze «sap/fluid exuded from stylet» for solutes/carbohydrates
OR
radioactive-labelled carbon can be detected «in the phloem sap»
f. stylets at different parts of the plant can show sequence/rate of movement

Question 14

explain the effects of auxin on plant cells

Answer 14

a. increases cell elongation/growth/enlargement OR has effect on rate of mitosis
b. changes the pattern of gene expression
promotes transcription of some genes
c. changes the pH of the extracellular environment/cell wall and
increases activity of proton pumps
d. breaks cross links/connections between cellulose fibres in cell wall
e. increases cell wall plasticity
f. «varying» auxin concentrations have different effects in different parts of
the plant

Question 15

explain changes in biomass for the biomass-respiration graph

Answer 15

a. increases cell elongation/growth/enlargement OR has effect on rate of mitosis
b. changes the pattern of gene expression
OR
promotes transcription of some genes
c. changes the pH of the extracellular environment/cell wall
OR
increases activity of proton pumps
d. breaks cross links/connections between cellulose fibres in cell wall
e. increases cell wall plasticity
f. «varying» auxin concentrations have different effects in different parts of
the plant

Question 16

explain why biomass continues to increase after the respiration levels plateau

Answer 16

a. development of mature trees requires xylem/wood
b. xylem/wood contributes to biomass but not respiration
c. photosynthesis/production greater than respiration
d. photosynthesis/production continues to accumulate biomass
OR
accumulated biomass remains/increases

Question 17

what do ocean currents do to plastic debris

Answer 17

they concentrate them

Question 18

outline the requirements for sustainability within a sealed mesocosm

Answer 18

• photosynthetic organisms/autotrophs/plants as producers;
• light (as energy source) for photosynthesis;
• nutrient/water recycling (by saprotrophs);
• decomposers/saprotrophs to breakdown (toxic) wastes;

Question 19

outline primary succession

Answer 19

colonization of areas that were barren/not previously inhabited/not occupied by organisms;

Question 20

outline processes that must occur over time to produce deeper soil

Answer 20

• weathering of rock accumulates matter (allowing pioneer species to grow);
• death/decomposition of organisms increase organic matter/detritus/litter;
• increased soil allows larger/more plants to grow / roots preventing erosion;
• as more plants are decomposed, soil depth/amount of soil available increases;

Question 21

explain how levels of PCBs increase so greatly over trophic levels

Answer 21

• as producers/algae take in nutrients, they also collect/absorb PCBs;
• consumers can take in PCBs directly from the water;
• PCBs are not digested/metabolized;
• PCBs build up in cells/tissues / bioaccumulate;
• PCBs pass on to higher level consumers or
  organisms in the higher trophic levels accumulate more;
• At each trophic level there is biomagnification;

Question 22

explain how biogeographic factors affect the richness and evenness of biodiversity

Answer 22

• biogeographic features are combinations of species, habitats and physical features
• richness is the number of different species present (in an area)
• evenness refers to relative abundance of the different species (in an area)
• large nature reserves/large islands have greater biodiversity
• large areas have more species/populations/habitats/richness
• connected areas/nature reserves have more diversity than isolated ones/corridors between areas increases biodiversity
• the greater the surface:perimeter ratio, the greater the biodiversity
• edges are transition areas
• circular shape has more biodiversity than rectangular shape;
• biodiversity measured by Simpson’s / diversity index;

Question 23

Suggest changes in the management of a national park that could reduce the amount
of macroplastic pollution.

Answer 23

• recycling programs
• place litter containers/garbage cans close to camping sites
• fines for those causing pollution or pass littering laws

Question 24

Describe one method that could have been used to estimate the population size of a
given tree in a forest after fire damage had occurred.

Answer 24

• random sampling using quadrats
• trees counted in quadrant
• population calculated using area

Question 25

when are edge effects especially pronounced?

Answer 25

in areas with small habitat fragments

Question 26

Explain how top-down factors control algal blooms.

Answer 26

• herbivores regulate algal bloom
• predators of the herbivores helps regulate algal bloom
• overfishing/death of predators decreases algal bloom as herbivore population increases
• pathogens of algae will decrease algal bloom
• habitat degredation can decrease algal bloom

Question 27

Discuss how crop plants obtain the phosphorus that they need to grow

Answer 27

• plants absorb phosphorous from the soil by the roots
• soil phosphorous comes from weathered phosphate rocks and from plant/animal residues
• phosphorous is necessary for ATP and DNA synthesis

Question 28

Discuss whether the supply of phosphorous of crops is sustainable

Answer 28

• natural phosphorous cycle is slow and not sustainable with increased crop production
• phosphorous is replenished by use of mineral fertilisers
• phosphorous is mined from rocks
• rocks are being used up and non-renewable
• increased demand for food increases demand for fertilisers

Question 29

Predict the possible effect of global warming on the nutrient fl ow in a taiga ecosystem.

Answer 29

• increased biomass
• increased uptake of nutrients from soil
• increased decomposition of litter
• increased nutrient composition of soil
• ## increased weathering of rocks

Question 30

Determine whether islands are open or closed ecosystems.

Answer 30

closed because islands do not exchanged matter/nutrients with surroundings

Question 31

Discuss two advantages of ex situ conservation measures.

Answer 31

• the protection of endangered species by breeding them in captivity
• education/research opportunities
• raise awareness or gain support for conservation actions

Question 32

Some scientists estimate that available phosphorus reserves in the Earth will be
completely depleted within approximately 100 years. Discuss the implications of these
estimates.

Answer 32

• production of fertilisers will decrease so their price will rise
• increase costs of foods
• development of alternative measures of agriculture

Question 33

The percentage of phosphorus in an ecosystem that is recycled per year is in most
cases very small, and far smaller than the percentage of nitrogen that is recycled.
Suggest reasons for this difference.

Answer 33

• largest store of phosphorous is in marine sediments and minerals, whilst nitrogen is in the atmosphere
• main source of release of phosphorous is by weathering of rocks, which is a slow process, whilst nitrogen is by bacterial action
• high concentrations of nitrogen vs low concentrations of phosphorous in living organisms
• phosphorous is not a very soluble mineral

Question 34

Discuss the factors affecting population growth that can result in an exponential
growth curve.

Answer 34

• exponential growth occurs in an ideal, unlimited environment
• population growth is determined by natality, mortality, immigration, and emigration
• natality increases population as long as it is higher than mortality
• low mortality leads to exponential growth
• absence of limiting factors will lead to exponential growth (eg competition for resources)
• draw a sigmoid curve and label it with exponential growth

Question 35

Compare and contrast food chains and food webs.

Answer 35

• both represent transfer of food/energy in an ecosystem
• in both, organisms are arranged by trophic levels/feeding positions
• one species could occupy different trophic levels in a food web but not a food chain

Question 36

Define invasive alien species.

Answer 36

organisms that are introduced and have negative environmental consequences

Question 37

Using one example, outline biological control of an invasive alien species.

Answer 37

• rabbits introduced into Australia
• controlled by release of myxoma virus from South America

Question 38

Explain biogeographic factors that increase the effectiveness of nature reserves.

Answer 38

• large area can support greater range of habitats
• reduced edge effect minimises competition
• unbroken/intact areas represent less disturbance on habitats

Question 39

Outline how reserve size and shape can impact edge effects.

Answer 39

• small reserve has greater edge relative to area, increasing edge effect
• changing shape can change the perimeter for a given area and change the edge effect

Question 40

identify the assumptions made in capture-mark-release-recapture

Answer 40

• assumes sample size is large enough to be significant
• assumes there is no emigration/immigration/death of snails
• assumes the marking of the snails doesn’t affect their survival
• assumes no misidentification of species
• assumes marked snails do not lose their marks

Question 41

Natural forests in the area around Mangalore contain hardwood trees such as
teak, Tectona grandis, which are deciduous, shedding their leaves once a year.
Suggest, with a reason, when this might happen.

Answer 41

dry season/Jan/Feb
drop leaves to prevent water loss/transpiration since no rainfall for months

Question 42

Describe how ingested plastics can cause problems to marine birds.

Answer 42

• fill up the stomachs of birds so they feel full and then starve to death
• block the passage of food, causing starvation

Question 43

how nitrogen and phosphorous cycles are disrupted by extreme weather events

Answer 43

• excess rain/floods washes away nutrients by leaching and can lead to waterlogged soils
• waterlogged soils lead to denitrification due to anaerobic conditions
• lightning increases N in soil