Study guide: Circulatory Systems in Animals

Course Outline

  1. Gas Exchange Surfaces
  2. Open Circulatory Systems
  3. Closed Circulatory Systems
  4. Heart Configurations Across Animals

1. Gas Exchange Surfaces

Essential Points

  • Animal gas-exchange surfaces include:
    • spiracles
    • gills
    • alveoli
    • skin

2. Open Circulatory Systems

Key Concepts & Definitions

  • Open circulatory system: A system in which haemolymph courses through the body and bathes all internal tissues rather than remaining enclosed in blood vessels.

★ Must-know

📌 An open circulatory system requires less energy to operate or maintain than a closed system, but moves less blood to metabolically active organs and tissues with high oxygen requirements.

Further detail

  • Insects and other invertebrates have haemolymph, a heterogeneous fluid that courses through their bodies and bathes internal tissues.

3. Closed Circulatory Systems

Key Concepts & Definitions

  • Closed circulatory system: Keeps blood enclosed within blood vessels and separate from body tissues.

★ Must-know

  • A closed circulatory system has a heart that pumps blood through a continuous circulation pattern, generally at higher pressure than an open system.

Further detail

📌 Animals with closed circulatory systems tend to be larger than animals with open systems, as illustrated by an elephant compared with a grasshopper.

  • Blood in a closed circulatory system does not fill body cavities.

  • Many vertebrates, including humans, have a cardiovascular system and a secondary lymphatic system.

  • A closed circulatory system can transport blood to extremities while maintaining higher blood pressure than an open system.

4. Heart Configurations Across Animals

Essential Points

  • Most mammals have four-chambered hearts that separate oxygenated blood from deoxygenated blood.

  • A fish has a two-chambered heart that pumps blood to the gills for oxygenation and then throughout the body.

  • Amphibians have three-chambered hearts in which oxygenated and deoxygenated blood mix before being pumped to the body.

Synthesis Tables

Heart Chambers and Blood Flow

Animal groupChambersBlood handling
Most mammalsFourOxygenated and deoxygenated blood remain separate
FishTwoBlood goes to the gills for oxygenation, then through the body
AmphibiansThreeOxygenated and deoxygenated blood mix before reaching the body

Test yourself

Take a 9-question practice quiz on Circulatory Systems in Animals, with every answer explained.

1. Which structures can facilitate gas exchange between an animal’s internal and external environments?

2. A biologist identifies a structure that enables gases to pass between an animal’s body and its surroundings. Which finding is an example of such a gas-exchange surface?

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Study with flashcards

Memorize the key concepts of Circulatory Systems in Animals with 20 flashcards.

What facilitates gas exchange between an animal’s internal and external environments?

Exchange surfaces such as spiracles, gills, alveoli, and skin.

What circulates through an open circulatory system and bathes its internal tissues?

Haemolymph.

How does an open circulatory system compare with a closed system in operating energy and blood delivery?

It requires less energy but moves less blood to metabolically active, high-oxygen tissues.

See the flashcards →

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