Transcript Effect of Temperature on Cold

Unit
Animal Science
Problem Area
Aquaculture
Lesson
Effect of Temperature on ColdBlooded Animals
Student Learning Objectives
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1. Define the term poikilotherm.
2. Explain how the circulatory system of
poikilotherms is affected by changes in
temperature.
3. Describe how temperature affects the
metabolic rate of poikilotherms.
4. Describe the effect other factors, beside
temperature, have on the activity of
poikilotherms.
Terms
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Circulatory system
Dissolved oxygen
Homeotherm
Metabolism
Poikilotherm
What is a poikilotherm?
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A poikilotherm is an organism whose body
temperature adjusts to its environment.
A. Poikilotherms are often referred to as coldblooded or ectotherms. This includes most fish and
reptiles. For this reason large fluctuation in water
temperature in an aquatic environment can cause
the aquacrop to be stressed or can effectively kill
them.
B. Homeotherms are organisms whose body
temperature is relatively constant. They are
commonly called warm-blooded or endotherms.
How is the circulatory system of poikilotherms affected
by changes in temperature?
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The general rule is that as temperature increase so
does bloodflow.
A. The circulatory system of the fish includes the
heart, gill blood vessels, cranial veins, cardinal
veins, aorta, portal vein, hepatic veins as well as
capillaries. Blood cells move through the capillaries
one blood cell at a time. Capillaries join together to
form veins in the tail which do not pulsate.
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B. When the water temperature decreases the blood
flow decreases. The diameter of the arteries gets
smaller and less blood gets circulated.
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C. When the water temperature increases the blood
flow also increases. The increased temperature
causes the blood vessels to expand and allow more
blood to flow.
What effect does temperature have on the metabolic
rate of poikilotherms?
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Metabolism is the process of converting food to
energy.
A. Metabolism requires that oxygen and food be
transported through the fish. When blood flow is
reduced due to temperature, less oxygen is
available to cells for respiration so the process is
slowed. As a result, in fish that are in temperatures
lower than their desired range, activity is reduced.
What factors, beside temperature, affect the activity of
poikilotherms?
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A. Water quality is of major importance in the general health of
aquatic organisms. This includes nitrogen compounds and
dissolved oxygen, among others. Nitrogen levels need to be
carefully monitored to reduce the harmful effects of ammonia and
nitrite. Generally dissolved oxygen, elemental oxygen that
remains in solution under existing conditions, levels needed to be
4–5 ppm at a minimum. Dissolved oxygen depletion can result in
large fish dying off in a matter of a few hours.
B. Stress levels associated with handling, injuries, crowding also
reduce the activity of fish.
C. Poor nutrition will also reduce fish activity.
Review/Summary
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What is a poikilotherm?
How is the circulatory system of poikilotherms
affected by changes in temperature?
What effect does temperature have on the
metabolic rate of poikilotherms?
What factors, beside temperature, affect the
activity of poikilotherms?