CHAPTER 8
REVIEW QUESTIONS
8.1
Although both energy and matter pass through the ecosystem, matter can be recycled by
decomposers back to the producers, but at each step in the food chain some energy is lost back
to the atmosphere as heat. Thus there is a constant depletion of energy from the food chain.
8.2
C: they release nutrients, otherwise locked up in the dead matter, for the use of producers.
8.3
a.
b.
c.
d.
Second order consumer.
They are found in rainforests thus they require a forest with a closed canopy which
provides a high humidity, an area which is not subject to drought, and a specific
temperature range.
They blend with their background so cannot be easily seen by predators; they are
nocturnal; they are able to remain motionless; they are able to eat insects and small
lizards and frogs.
Generalists since they eat a variety of different foods. This aids their survival since if one
food source (e.g. insects) is low they are able to feed on other organisms.
8.4
As each organism moves about and undergoes metabolic activities, some of the energy tied up
in chemical bonds in its body is converted to heat energy and is released into the atmosphere.
Thus there is less and less chemical bond energy available for further consumers further up the
food chain.
8.5
Biomass is the amount of organic matter in a system. Productivity is a measure in the increase
in biomass in a particular length of time. Standing crop is the biomass in a system at any
particular time.
8.6
An ecological pyramid is a model of an ecosystem showing the numbers of individuals, the
amount of biomass, or the amount of energy at each level of the food chain.
8.7
D
8.8
B
8.9
B
8.10
When a pyramid of energy or biomass is drawn it is invariably a pyramid shape with the largest
level at the bottom – the biomass and the energy it contains sustain the rest of the food chain.
In a few ecosystems, where the growth rate of the producers is extremely high, such as an
oceanic plankton system, the producer standing crop may be lower than that of the consumers.
In a pyramid of numbers there is no indication of the actual biomass and so one tree may
support a large number of consumer organisms.
8.11
Carbon can be locked up as limestone rock, coal, petroleum and other fossils.
8.12
In a cycling pool the nutrient is constantly moving between the abiotic and biotic
environments, whereas in a reservoir pool the mineral nutrient is one in which there is little or
no movement of the nutrient from the abiotic environment.
8.13
Phosphorus is a rare element, much of which is eroded as phosphate and washes out to sea
where it becomes locked into deep sea sediments. The main return to the land of this phosphate
is through sea birds, which transfer the phosphate from the marine ecosystem to the land where
they deposit excreta, particularly at rookeries, to form guano. Human exploitation of the guano
deposits occurs at a faster rate than it is formed.