Download Unit 4 Ecosystem Dynamics and Biodiversity

Unit 4 Ecosystem Dynamics
and Biodiversity
Assessment Scenario Key
By Dr. Teresa Martin
Population Dynamics
180
160
Population (in thousands)
140
120
100
Hare
Lynx
80
60
40
20
0
1840
1860
1880
1900
Year
1920
1940
1. (a) The predator is the lynx. The prey is the hare.
(b) Looking at the graph you can see that both graphs
rise and fall almost in sequence. This shows that they
control each other.
(c) This graph is similar to the one in the habitat
activity because each one shows the population
changes over time.
(d) The factors that control population fluctuations
(changes) are the amount of food, water, shelter and
space available. These are limiting factors.
2. Balance of nature is a theory that proposes that
ecological systems are usually in a stable equilibrium
(also called homeostasis), which is to say that a small
change in some particular parameter (the size of a
particular population, for example is the stimulus) will
be corrected by some negative feedback (response) that
will bring the parameter back to its original "point of
balance" with the rest of the system. It may apply where
populations depend on each other, for example in
predator/prey relationship between the lynx and the hare.
Nature is never really in balance because populations
are constantly in flux (a state of change). Constant
change is the norm, not balance. There is no such thing
as a 'balance of nature'. The clearest evidence of this is
the harsh reality of extinction. Species don't exist in
stasis or 'balance'. They're simply contenders for
energy and organization. When a species consumes all
the available resources, or runs into
a more effective competitor for
same, its numbers crash- often
to zero.
3. The essential components of a habitat are food,
water, shelter and space in an appropriate arrangement.
4. Limiting factors are factors present in an
environment that controls a process, particularly the
growth, abundance or distribution of a population of
organisms in an ecosystem. These are any natural
resource that a population needs to survive and
reproduce.