Science Bite
Drifters of the Sea
The word “plankton” comes from the Greek word “planktos” which means to drift or wander – which is
exactly what plankton do! Plankton are usually so small that you can only see them with a microscope or
magnifying glass – but despite their small size, they play a huge role in the marine ecosystem. Plankton
come in all shapes and sizes and can be divided into two main groups: phytoplankton and zooplankton.
Phytoplankton = plant plankton – use photosynthesis to convert sunlight and carbon dioxide (CO2) into
food and oxygen (O2).
• Phytoplankton are particularly important to supporting life in Earth’s ocean - they are the
primary producers in both freshwater and marine food webs. They make food through the
process of photosynthesis and then become food for everything from zooplankton to herring to
whales. Phytoplankton are also responsible for producing most of the oxygen in Earth’s
atmosphere.
Zooplankton = animal plankton – feed on phytoplankton and other zooplankton.
• Some zooplankton, such as copepods, will remain plankton their entire lives – holoplankton
(holo = whole). Other zooplankton, such as barnacle larva, are plankton for only part of their
lives – meroplankton (mero = part). Zooplankton are usually microscopic, but large jellyfish are
considered to be zooplankton as well.
Use the information above to fill in the blanks and answer the following questions:
1. Where does the word “plankton” come from?
2. The two main types of plankton are __Phytoplankton___ and ____Zooplankton_____.
3. Some plankton spend their entire lives in planktonic form, these are known as _holoplankton__,
while other plankton known as ___meroplankton____ spend only part of their lives in
planktonic form.
4. Why are phytoplankton so important in marine ecosystems?
Phytoplankton are the primary producers in both freshwater and marine food webs and they provide.
They serve as food for everything from zooplankton to herring to whales. Phytoplankton are also
responsible for producing most of the oxygen in Earth’s atmosphere.
5. What do zooplankton feed on?
Phytoplankton and other zooplankton
ANSWER KEY
