2.2

Unicellular Organisms

Text pages 43-47

The Big ideas• What are unicellular organisms and how are

they the same or different from multicellular organisms?

2.2 Unicellular Organisms

• Unicellular organisms are called micro- organisms– Only visible under a microscope– Have only one cell– Still does all 6 characteristics of living things– Some make us sick, some are important for us to

survive

1. Bacteria

• Most plentiful• Make own food or live off of a plant or animal

(parasitic)• Prokaryotic• No nucleus, mitochondria or ribosomes• See text page 44

2. Protists

• Eukaryotic• Two types:1. Plantlike protists (text page 44)- Can produce own food (have chloroplasts)- Diatoms, Euglena2. Animal- Like Protists (text page 45 and 46)- Must feed on things that are or once were living- Amoebae, Paramecia

Any member of a class of unicellular algae, that live in cold waters of relatively low

salinity. All have shell-like, brittle cell walls made out of silica (glass) and pectin. The

walls, which are porous to allow materials in to and out of the cell, consist of two

interlocking halves that fit together like a pillbox.

Because they depend on sunlight for photosynthesis, diatoms generally live in

the upper 200 meters of oceans and bodies of fresh water. Some species simply

float in the water currents near the surface; others attach themselves to larger

floating objects or to the sea floor.

When diatoms die, they slowly sink to the seabed. The buildup of trillions of these shells forms a crumbly white sediment

known as diatomaceous earth or diatomite, which is used in manufacturing

pool filters and abrasives, including toothpaste.

Major Japanese oil wholesaler Nippon Oil and Hitachi subsidiary Hitachi Plant Technologies are developing a technology that’s supposed to make it possible to mass-produce eco-friendly jet fuel from Euglena, single-celled organisms that live in ponds and lakes.

3. Fungi

• Can be multicellular or unicellular• Bread mould, mushrooms, athletes foot,

ringworm, yeast (unicellular)