1
Ecology 4
Main Idea: How does it benefit the ecosystem
if it contains many species and habitats
A.
Biodiversity(Definition) – is a
measurement of the degree to which species
vary within an ecosystem.
1. There is a strong connection between
biodiversity and the stability of an
ecosystem.
a. For example: A natural forest
contains many
different species of trees. If disease
or insects
attacks one population, nearby trees of
another species are likely to survive.
b. The mix of species in the ecosystem
also makes it difficult for the disease
organisms to move quickly through this
environment. Here biodiversity serves
as a barrier to the spread of the
disease.
c. In contrast, on a tree farm where
all of the trees are planted and are of
2
a single species, the entire population
could be seriously damaged by a single
disease or insect attack.
2. The interactions between organisms may
allow an ecosystem to remain stable for
hundreds or thousands of years.
3. In established, stable ecosystems,
populations tend to increase and decrease
in size in a predictable pattern. Over
time, however, the size of the population
remains relatively stable.
a. For example: when the prey
population increases, a large food
supply causes the size of the predator
population to rise, because each
predator will eat as many prey as it
can, the prey population rapidly
decreases.
b. With the decline in a prey
population, some of the predators begin
to starve. When only a few predators
remain alive, the prey population
reproduces and greater numbers of prey
3
survive.
The cycle begins anew.
The loss of biodiversity in an ecosystem
upsets its stability.
4.
a. Removing species from an
environment often causes instability
due to the loss of organisms that were
filling critical ecological niches.
5. Many species may be lost when natural
disasters or human activities cause largescale destruction to habitats.
a. Clearing large areas of tropical
rain forest has disrupted many
ecosystems; some may never recover.
1. Although some species may be
able to return to a damaged
ecosystem, others with critical
roles may be totally lost.
2. The interdependencies between
populations in the original
ecosystem may have been so great
that if biodiversity is lost, the
ecosystem may never be restored to
its original state.
4
b. Species can also be lost when
humans do not consider the environment
impact of their actions.
1. Offering bounties for the
removal of mountain lions from some
environments sounded like a good
idea at one time, but it led to
population explosions of deer herds.
2. Soon the deer overpopulated the
area, and overgrazing reduced the
food supply so much that deer
starved. The over grazing also led
to soil erosion that caused
permanent environmental damage.
3. The negative effects begun by
the removal of mountain lions were
evident for many years.
c. When humans clear land for
agricultural purposes, the loss of
biodiversity may also lead to an
unstable environment.
1. Disease and insect pests present
major problems to farmers whose
crops are genetically similar.
5
2. For these farmers, any
disruption threatens to affect the
entire crop.
3. Farmers are constantly in search
of ways to control insect pests and
diseases in their crops, because
they have created an environment
that is always in danger of serious
disruption.
4. In natural ecosystems, the
diversity of species provides no
such concentration of one kind of
making it far less likely that any
single pest or disease will cause
problems.
B.
Biodiversity Benefits Humans
1. Biodiversity also represents one of
the greatest resources known to humans.
2. It ensures the availability of a rich
variety of genetic material, some of which
may prove valuable to humans.
3. The genetic diversity found in rain
forests has provided humans with
6
medicines, insecticides, and other useful
resources.
4. If we destroy ecosystems, we lose much
of the biodiversity they hold.
5. As diversity is lost, potentially
valuable resources are lost with it.
There will be a quiz on this entire packet
on _____
There will be a TEST on this entire packet
on_____
.
.
Unit XV: Ecology Notes [Notes2000 #8]