8.1.2 Classification of Animals On the Basis of Temperature

Animals can be classified on the basis of the ability to thermoregulate and the source of body heat. These classifications help us understand how different animals maintain their body temperature.

Definition

Classification of Animals on the Basis of Temperature: Animals can be classified on the basis of the ability to thermoregulate and the source of body heat.

Main Idea

Animals can be classified in two ways:

• Poikilotherms — unable to maintain their body temperature within narrow limits using physiological mechanisms
• Homeotherms — able to maintain a fairly constant body temperature by using physiological mechanisms

• Ectotherms — rely more on heat derived from the environment to raise their body temperature
• Endotherms — produce their own body heat through heat production as byproduct during metabolism

Core Concept

• Poikilotherms = unable to maintain constant body temperature
• Homeotherms = able to maintain constant body temperature
• Ectotherms = rely on environmental heat
• Endotherms = produce their own body heat
• Poikilotherms = all non-vertebrates, fishes, amphibians, reptiles
• Homeotherms = birds and mammals
• Ectotherms = most invertebrates, fishes, amphibians, reptiles
• Endotherms = birds and mammals

Detailed Explanation

Classification on the Basis of Ability to Thermoregulate

Animals can be classified based upon ability to maintain constant body temperature as poikilotherms and homeotherms.

• Are all non-vertebrates, fishes, amphibians and reptiles.
• These are unable to maintain their body temperature within the narrow limits using physiological mechanisms.

Homeotherms: - Are birds and mammals which are able to maintain a fairly constant body temperature by using physiological mechanisms.

Classification on the Basis of Source of Body Heat

Animals are also classified on the basis of source of body's heat as ectotherms and endotherms.

• Animals produce metabolic heat at low level that is also exchanged quickly with environment.
• They rely more on heat derived from the environment to raise their body temperature.
• Examples are most invertebrates, fishes, amphibians and reptiles.

• Animals produce their own body heat through heat production as byproduct during metabolism in muscles or by the action of hormones that increase metabolic rate.
• The examples of endotherms are birds and mammals.

Summary Table of Classification

Intermediate Level

Classification of Animals on the Basis of Temperature

Detailed Description of Each Type

Comparison of Ectotherms and Endotherms

Formula / Mathematical Form

Not applicable to this topic.

Solved Example

Not applicable to this topic (descriptive topic).

Important Points

• 1. Animals can be classified on the basis of ability to thermoregulate.
• 2. Animals can be classified on the basis of source of body heat.
• 3. Poikilotherms cannot maintain constant body temperature.
• 4. Homeotherms can maintain constant body temperature.
• 5. Ectotherms rely on environmental heat.
• 6. Endotherms produce their own body heat.
• 7. Poikilotherms include non-vertebrates, fishes, amphibians, reptiles.
• 8. Homeotherms include birds and mammals.
• 9. Ectotherms include most invertebrates, fishes, amphibians, reptiles.
• 10. Endotherms include birds and mammals.
• 11. Ectotherms produce metabolic heat at low level.
• 12. Endotherms produce heat through metabolism.
• 13. Endotherms have higher metabolic rate.
• 14. Ectotherms use behavioral adaptations.
• 15. Endotherms use physiological mechanisms.

Remember

• - Poikilotherms = unable to maintain constant body temperature
• - Homeotherms = able to maintain constant body temperature
• - Ectotherms = rely on environmental heat
• - Endotherms = produce their own body heat
• - Poikilotherms = all non-vertebrates, fishes, amphibians, reptiles
• - Homeotherms = birds and mammals
• - Ectotherms = most invertebrates, fishes, amphibians, reptiles
• - Endotherms = birds and mammals

Common Mistakes

• 1. Confusing poikilotherms and homeotherms — Poikilotherms = variable; homeotherms = constant.
• 2. Mixing up ectotherms and endotherms — Ectotherms = environmental heat; endotherms = metabolic heat.
• 3. Thinking all fish are ectotherms — Most fish are ectotherms, but some are endotherms.
• 4. Believing all mammals are endotherms — Yes, all mammals are endotherms.
• 5. Mixing up the examples — Birds and mammals = homeotherms and endotherms.
• 6. Forgetting the role of behavioral adaptations — Ectotherms use behavior to regulate temperature.
• 7. Thinking endotherms do not use behavior — Endotherms also use behavior.
• 8. Mixing up the metabolic rates — Endotherms have higher metabolic rates.
• 9. Believing poikilotherms are always cold — They can be warm, but their temperature varies.
• 10. Forgetting the role of hormones — Hormones increase metabolic rate in endotherms.

Quick Revision

Animals can be classified on the basis of the ability to thermoregulate and the source of body heat. Animals can be classified based upon ability to maintain constant body temperature as poikilotherms and homeotherms. Poikilotherms are all non-vertebrates, fishes, amphibians and reptiles. These are unable to maintain their body temperature within the narrow limits using physiological mechanisms. Homeotherms are birds and mammals which are able to maintain a fairly constant body temperature by using physiological mechanisms. Animals are also classified on the basis of source of body's heat as ectotherms and endotherms. Ectotherms animals produce metabolic heat at low level that is also exchanged quickly with environment. They rely more on heat derived from the environment to raise their body temperature. Examples are most invertebrates, fishes, amphibians and reptiles. Endotherms animals produce their own body heat through heat production as byproduct during metabolism in muscles or by the action of hormones that increase metabolic rate. The examples of endotherms are birds and mammals.

60-Second Revision

• Poikilotherms = unable to maintain constant body temperature
• Homeotherms = able to maintain constant body temperature
• Ectotherms = rely on environmental heat
• Endotherms = produce their own body heat
• Poikilotherms = all non-vertebrates, fishes, amphibians, reptiles
• Homeotherms = birds and mammals
• Ectotherms = most invertebrates, fishes, amphibians, reptiles
• Endotherms = birds and mammals
• Warning: Ectotherms rely on environmental heat; endotherms produce their own body heat

NEXT TOPIC

• Chapter:
• 8. Thermoregulation and Homeostasis

• Topic:
• 8.1.3 THERMOREGULATORY STRATEGIES IN MAN

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