CHAPTER 6
EXTENDING YOUR IDEAS
1.
The wallum is a stunted vegetation found in sandy, low nutrient soils. The larger mammals
such as wallabies and kangaroos feed on grasses which are sparse in these areas and larger
possums, koalas etc., are adapted to tree species which cannot grow in these conditions. Since
these heathland plants flower prolifically during much of the year, organisms adapted to
nectar, flower and fruit eating (e.g. honey-eating birds, small mammals and insects) are
attracted to the wallum. These in turn attract organisms which feed upon them, such as snakes,
lizards and insectivorous birds.
2.
The soil does not retain enough water for rainforest growth.
3.
a.
b.
c.
Sirex – pine tree
habitat
Sirex larvae – Amystereum
predation
Amystereum – pine tree
parasitism
Birds – Sirex adults
predation
Megarrhysa larvae – Sirex larvae
predation
Ibalia larvae – Sirex larvae
predation
Deladenus – Sirex, Megarrhysa, Ibalia
parasitism
Deladenus – Amystereum
predation
Megarrhysa successfully destroyed most of the Sirex larvae and thus further
generations of eggs were not laid in the trees along with the Amystereum filaments.
Several hypotheses possible, e.g.:
The original infestation of Sirex was so large that not all of them have been destroyed
by the introduced species.
Or
There have been migrations of Sirex from adjoining areas, as the numbers were
reduced by the control species.
4.
Answer variable depending on choice of community. Information for wallum given in text,
e.g.: since wallum is found in Queensland, insolation is high leading to tropical–warm
temperate climate with high summer rainfalls and drier winters. Soil is derived from sandstone
and sediments – low nutrient and water retention. Between the soil and the climate the type of
flora is limited to heaths and shrubby trees and this limits the type of fauna. (Give examples of
both and their adaptations to these conditions). Plant matter and animal droppings add humus
to the soil which is either decomposed and the matter recycled, or helps in the development of
hard clay pans which limit movement of water downwards. This results in the formation of
swamp areas in which only certain types of plants are adapted e.g. paperbarks and rushes.
5.
Answers to include information from three of the following four options:
Macropus robustus robustus
Temperature range between 27–32°C January and -1–16°C July; mean annual rainfall greater
than 800 mm; rainforest, temperate forest or savannah woodland.
Macropus robustus woodwardi
Temperature range greater than 30°C January and 10°C July; annual rainfall 500–800 mm;
desert, arid scrub, grassland and savannah woodland.
Macropus robustus erubescens
Temperature range greater than 32°C January and -1°C July; annual rainfall below 500 mm;
desert, arid scrub, grassland, mallee scrub.
Macropus antilopinus
Temperature range between 27–38°C January and greater than 10°C July; mean annual
rainfall greater than 800 mm; savannah woodland, monsoon forest.
6.
The fly larva has a very high rate of evaporation, from 50 to 25°C, thus would be most likely
to be found in cool, shaded and enclosed places with a high moisture content (and thus
humidity), e.g. decomposing matter that is protected from the direct sun. Up to 40oC the
evaporation rate of both the crustacean and the beetle is relatively low, although that of the
crustacean is higher. It is probably found in leaf litter such as that found in a rainforest. The
beetle would probably be found in more open areas of forest or woodland since it has the
lowest evaporation rate at higher temperatures.
7.
Either argument is valid but must be backed up with suitable data.
8.
a.
b.
9.
Black kite group – predators of insects and small birds fleeing from the fire.
Pied butcherbird group – scavengers of animals which have been killed by the fire as
well as predators of those escaping fire.
Whistling kite group – predators of organisms fleeing fire, scavengers of those killed in
the fire and predators of other scavengers.
Owl group – scavengers of animals killed in the fire.
Straw-necked ibis – insect eater – those fleeing the fire or scavenging on carcasses.
Red-tailed black cockatoo – seeds and nuts released during the fire.
Partridge pigeon – seeds released during the fire, suckers and young grasses.
Little corella group – suckers.
The fire represents a disclimax community. Although many plant species will have
organs such as dormant bud, lignotubers, and specialised bark so that they do not die
during the fire, some will not be able to survive. Animals which cannot move quickly
ahead of the fire will be killed. Thus for a period after the fire, the plant community
will be all but nonexistent and the only animals will be scavengers and those that prey
on the scavengers. As the plants begin to regenerate, those species of animals that
utilise young plant growth (and their predators) will return to the area, the biodiversity
becoming greater as the forest returns to its natural state.
This is a variable answer depending on the animal selected.
Concept map (part b) should include tolerance ranges of abiotic factors and detailed food web
showing relationships of biotic factors.
Prediction (part c) should show evidence of good analysis of data and should demonstrate
logical sequencing of ideas in developing the prediction.