Scientists Say: Eukaryote

Eukaryotes are living things whose cells package their DNA inside a nucleus

Eukaryotic cells, like the one illustrated, contain structures called organelles that perform different jobs.

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Eukaryote (noun, “Yoo-CARE-ee-ote”)

Eukaryotes are living things whose cells contain a nucleus. The nucleus is a pouch that stores the cell’s DNA. Eukaryotic cells also hold other pouches that do specific jobs inside the cells. These pouches are called organelles. Some, for instance, generate energy to keep cells running. Others remove unwanted waste. This is similar to the way organs in your body do different jobs to keep you healthy.

A wide variety of creatures are eukaryotes. Some, such as yeast, are only a single cell. Others, such as plants and animals, are made of many cells. But not every living thing is a eukaryote. Some are prokaryotes. These are living things whose cells do not package their DNA inside a nucleus. The genetic material just floats around the cell. Prokaryotic cells don’t have organelle pouches, either. They are simple cells. And all prokaryotes are single-celled creatures. Bacteria and archaea are examples.

Eukaryotes are thought to have emerged about 2 billion years ago. They may have arisen from simpler cells that gobbled up their neighbors. Some of the cells that got eaten were not digested. Instead, they started doing the work of organelles inside the bigger cells. Mitochondria, for instance, may have once been snarfed-up cells. Now, those organelles generate energy for eukaryotic cells. Chloroplasts may have suffered the same fate. Those organelles convert sunlight into energy in plant cells.

In a sentence

Fossils dating back 750 million years may offer the oldest evidence of vampire-like microbes biting into eukaryote cells to suck out their insides. 

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Maria Temming is the assistant editor at Science News for Students. She has bachelor's degrees in physics and English, and a master's in science writing.

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