Unicellular vs Multicellular

• Define and differentiate between unicellular and multicellular organisms.

• Explain how unicellular and multicellular organisms carry out essential life functions.

• Identify and provide examples of both unicellular and multicellular organisms.

• Describe the concept of cell specialization in multicellular organisms.

Key Vocabulary

Organism

An organism is any living thing that can carry out life processes on its own.

Cells

Cells are the smallest units of life and the basic building blocks of all living things.

Unicellular

A unicellular organism is a living being that is made up of only one single cell.

Multicellular

A multicellular organism is a living being that is made up of more than one cell.

Reproduce

To reproduce is the biological process of making more organisms of the same kind or species.

System

A system is a group of interacting or interrelated parts that work together to form a whole.

What Are Cells and Organisms?

• An organism is any living thing, from a tiny bacterium to a large whale.

• Cells are the basic building blocks that make up all organisms.

• They perform different functions to keep the organism alive.

Unicellular Organisms

Amoeba

• An amoeba moves around by changing its body shape.

• It eats by surrounding smaller food particles with its body.

• This organism has a very flexible cell membrane.

Euglena

• A euglena moves forward using its long, whip-like tail.

• It can make its own food just like a plant.

• This organism has an eye spot to help it find light.

Paramecium

• A paramecium moves using many tiny hairlike structures.

• These hairs also help it sweep in food to eat.

• This organism has a distinct slipper-like body shape.

What Are Multicellular Organisms?

• Multicellular organisms are living things made of more than one cell.

• ​They have different types of specialized cells that perform specific jobs.

• Transport systems move nutrients and gases throughout the organism's body.

• Humans, plants, and animals are examples of multicellular organisms.

Similarities

• ​Both single-celled and multicellular organisms need to get rid of waste materials to survive.

• ​​This waste removal process is a shared characteristic that is essential for all living things.

• ​Getting rid of waste helps them maintain a stable and healthy internal environment.

Differences

• ​Multicellular organisms are more complex, with specialized cells that perform different jobs.

• ​​A single-celled organism has only one cell to carry out all life functions.

• ​The number of cell types helps scientists classify an organism as uni- or multicellular.

• All living things are made of cells; unicellular organisms have only one cell.

• Multicellular organisms have many specialized cells that form complex systems.

• A key similarity is waste removal; a key difference is complexity.

• The number of cell types distinguishes unicellular and multicellular life.