Difference Wiki

Protozoans vs. Metazoans: What's the Difference?

Edited by Aimie Carlson || By Janet White || Published on February 5, 2024
Protozoans are single-celled organisms, while Metazoans are multicellular animals, representing a fundamental difference in complexity and organization.

Key Differences

Protozoans are unicellular organisms, meaning they consist of a single cell that performs all life functions. Metazoans, in contrast, are multicellular animals, with cells differentiated into tissues and organs for specialized functions.
Protozoans belong to the kingdom Protista, characterized by their simple cellular structure and varied modes of nutrition. Metazoans are part of the kingdom Animalia and are distinguished by their complex body structures and typically heterotrophic mode of nutrition.
Protozoans primarily reproduce asexually, though some exhibit sexual reproduction. Their life cycles can be complex, involving different forms depending on the environment. Metazoans, however, have more complex life cycles, often including sexual reproduction, development stages, and sometimes metamorphosis.
Protozoans are found in a wide range of habitats, including water bodies, soil, and as parasites inside other organisms. Metazoans inhabit diverse environments on earth and play varied roles in ecosystems, from primary consumers to apex predators.
Protozoans represent some of the earliest forms of life, offering insights into the evolution of cellular processes. Metazoans show the complexity of evolution, with a wide range of body plans and adaptations to different environments.

Comparison Chart

Cellular Structure


Biological Kingdom



Mostly asexual, some sexual
Primarily sexual, with developmental stages


Varied, including aquatic and parasitic
Diverse, including terrestrial and aquatic

Role in Ecosystem

Producers, consumers, decomposers
Consumers, including predators and prey

Protozoans and Metazoans Definitions


Protozoans can be free-living or parasitic.
Malaria is caused by Plasmodium, a parasitic protozoan.


Metazoans reproduce sexually, contributing to genetic diversity.
Butterflies, as metazoans, undergo metamorphosis during their life cycle.


Some protozoans can form cysts to survive harsh conditions.
To survive drought, certain protozoans form protective cysts.


Metazoans can be invertebrates or vertebrates.
Fish, birds, and mammals are all vertebrates within the metazoan category.


Protozoans exhibit various forms of locomotion, like cilia and flagella.
Paramecia use cilia for movement, a characteristic feature of these protozoans.


Metazoans are multicellular animals with complex, differentiated tissues.
Humans are metazoans with highly specialized organ systems.


Protozoans play essential roles in nutrient cycles and food webs.
Protozoans in soil contribute to decomposing organic matter.


Metazoans are an integral part of ecosystems, serving various ecological roles.
Predatory metazoans like lions play a crucial role in maintaining ecological balance.


Protozoans are single-celled eukaryotic organisms often found in aquatic environments.
Amoebas, a type of protozoan, are common in pond water.


Metazoans' bodies are organized into systems like the nervous and digestive systems.
The complex digestive system of cows, as metazoans, allows them to process cellulose.


Any of numerous chiefly single-celled eukaryotic organisms, most of which move about freely and ingest food, including the amoebas, ciliates, flagellates, and apicomplexans. Protozoans along with certain algae, oomycetes, and some other groups make up the protists.


Any of numerous heterotrophic eukaryotic organisms of the kingdom Metazoa, characteristically having a multicellular body with cells differentiated into tissues; an animal.


Plural of protozoan


Plural of metazoan


How do protozoans reproduce?

Protozoans mostly reproduce asexually, with some exhibiting sexual reproduction.

What is a protozoan?

A protozoan is a single-celled eukaryotic organism, often found in moist environments.

Do metazoans have specialized cells?

Yes, metazoans have specialized cells organized into tissues and organs.

What is the ecological role of protozoans?

Protozoans serve as producers, consumers, and decomposers in ecosystems.

What defines a metazoan?

A metazoan is a multicellular animal with complex, organized body structures.

Is a protozoan larger or smaller than most metazoans?

Protozoans are generally much smaller than metazoans.

Can metazoans live in extreme environments?

Some metazoans have adapted to live in extreme environments.

Are protozoans considered animals?

Protozoans are not animals but are classified under the kingdom Protista.

How do metazoans contribute to biodiversity?

Metazoans contribute significantly to biodiversity through various forms and ecological roles.

What types of reproduction are seen in metazoans?

Metazoans primarily reproduce sexually, involving the combination of genetic material.

Can protozoans be harmful to humans?

Some protozoans are parasitic and can cause diseases in humans.

Are metazoans capable of complex behaviors?

Yes, many metazoans exhibit complex behaviors due to their advanced nervous systems.

How do protozoans obtain nutrients?

Protozoans obtain nutrients through various methods, including absorption and ingestion.

Do metazoans have a role in food chains?

Yes, metazoans are crucial in food chains, serving as prey and predators.

What habitats do protozoans inhabit?

Protozoans inhabit a variety of habitats, including aquatic and terrestrial environments.

Do metazoans have a single type of tissue?

No, metazoans have multiple types of tissues with specialized functions.

What is the significance of protozoans in science?

Protozoans are important in research for understanding basic biological processes.

Do metazoans have a fixed body plan?

Most metazoans have a fixed body plan determined by their genetics.

What is the lifespan of metazoans compared to protozoans?

The lifespan of metazoans varies widely and is generally longer than that of most protozoans.

Are all protozoans microscopic?

Most protozoans are microscopic, but some can be seen with the naked eye.
About Author
Written by
Janet White
Janet White has been an esteemed writer and blogger for Difference Wiki. Holding a Master's degree in Science and Medical Journalism from the prestigious Boston University, she has consistently demonstrated her expertise and passion for her field. When she's not immersed in her work, Janet relishes her time exercising, delving into a good book, and cherishing moments with friends and family.
Edited by
Aimie Carlson
Aimie Carlson, holding a master's degree in English literature, is a fervent English language enthusiast. She lends her writing talents to Difference Wiki, a prominent website that specializes in comparisons, offering readers insightful analyses that both captivate and inform.

Trending Comparisons

Popular Comparisons

New Comparisons