SKILL FOCUSInitiating and planningHypothesizingIdentifying the variablesCommunicating resultsInvestigation
DESIGN YOUR OWN
6•A188 MHR • Unit 2 Homeostasis
Without immediate treatment, this situation can
result in death within minutes. Emergency treatment
involves injections of adrenaline hormone.
Adrenaline mimics the action of the sympathetic
nervous system, increasing heart rate and the
strength of heart contractions. This action helps to
restore blood pressure.
People at risk for anaphylactic shock usually
carry a syringe-like device called an EpiPen™ (as
shown in Figure 6.20). This device can be used to
quickly self-administer (if necessary) a life-saving
dosage of adrenaline. Doctors recommend that at-
risk individuals also wear emergency identification
bracelets.Figure 6.20An EpiPen™ is used to counteract anaphylactic
shock.In the first experiment, a set amount of food was given
to a group of mice who were roaming freely in the
basement of an old building. The researchers noted
that when the food supply could no longer support
the population, some mice moved to other parts of
the building.
In the second experiment, the mice were confined to a
large enclosure, so they could not leave. When the food
ran out, the researchers noted that the birth rate dropped
to zero. In this instance, the crowding resulted in
changes to the reproductive system of the female mice.
The third experiment involved a population of mice in a
closed enclosure supplied with unlimited food. This
experiment was performed in a variety of locations and
resulted in different observations. In Wisconsin, the
crowded population of mice became more aggressive,
and chasing and fighting behaviours increased. As well,
females stopped caring for their young, and most of
the young mice died. When the same experiment
was performed in England, the result was a decline
in birth rate.Problem
How do guppy populations respond to crowded
conditions?Hypothesis
Make and record a hypothesis on the effect of crowding
on guppy populations.CAUTION: Treat living organisms with care and
respect.Materials
a number of male and female guppies
fish tanks fish foodExperimental Plan
1.Working in a group, design an experiment to show
the effects of crowding on guppies.
2.Choose the size of fish tank(s) you want to use, the
amount of food, a method of keeping the amount
of food constant, the number and sexes of fish, and
so on.Crowding Stress on a Guppy Population
Animal populations react to the stress of overcrowding in various ways. Studies
show that animals under stress exhibit changes in hormone levels, changes in
behaviour, or a combination of both. In the 1970s, researchers at the University
of Wisconsin performed a series of experiments on mouse populations.