Types of Circulation in Organisms (With Examples from Different Phyla and Classes)

Photo Credit: Ahmad Coaching

Circulation refers to the movement of fluids, such as blood or haemolymph, within an organism’s body. It helps in the transport of nutrients, gases, and waste products. In living organisms, there are different types of circulation depending on their level of organisation and body structure.

The two major types of circulation in animals are:

  1. Open circulatory system
  2. Closed circulatory system

Open Circulatory System

In an open circulatory system, the circulatory fluid (called haemolymph) is not always contained within blood vessels. Instead, it flows freely within body cavities and comes into direct contact with body tissues.

Characteristics:

  • Blood is not fully enclosed in vessels.
  • Haemolymph bathes organs directly.
  • Pressure is low and circulation is slow

Organisms with Open Circulatory System

This system is mainly found in the Phylum Arthropoda and some members of Phylum Mollusca.

Examples:

  1. Phylum Arthropoda
  • Insects (e.g. grasshopper, cockroach, butterfly)
  • Crustaceans (e.g. crab, prawn)
  • Arachnids (e.g. spider)
      2. Mollusca

  • Snail (class Gastropoda)
  • Some bivalves (e.g. oyster, mussel)
Closed Circulatory System

In a closed circulatory system, blood is always enclosed within blood vessels and is pumped by the heart. This allows faster and more efficient transport.

Characteristics:

  • Blood remains within vessels (arteries, veins, capillaries)
  • Higher pressure and faster circulation
  • More efficient oxygen and nutrient delivery

Organisms with Closed Circulatory System

This system is found in the following animal groups:

A.  Phylum Annelida

  • Earthworm
  • Leech
B.  Phylum Chordata

This includes vertebrates:

  1. Class Pisces (Fish): e.g. Tilapia, Catfish, etc.
  2. Class Amphibia: e.g. Frog, Toad, etc.
  3. Class Reptilia: e.g. Lizard, Snake, etc.
  4. Class Aves (Birds): e.g. Pigeon, Hen etc.
  5. Mammalia: e.g. Human, Dog, Goat, etc.

Comparison of the Two Systems


The type of circulatory system in an organism depends on its level of complexity. Simple organisms like arthropods have an open system, while more complex organisms such as vertebrates have a closed circulatory system. The closed system is more efficient and supports higher metabolic activities.


Related Reading:

The Human Circulatory System: Structure and Functions Explained Simply

The Human Heart: Structure and Functions Explained Simply

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