how they reproduce. The algae that reproduce sexually will latter reproduce
asexually. All algae reproduce asexually. Unicellular algae divide by mitosis and
cytokinesis. Multicellular algae that contain thalli and filaments can fragment.
Each new piece can form a thallus and a filament.T YPES OF ALGAE
Chrysophytes
Chrysophytesare unicellular algae that live in fresh water and contain chloro-
phyll aand chlorophyll c, which are photosyntheticpigments used to transform
sunlight into energy. These are also known as golden algae because they have
golden silica scales. There are 500 known species of chrysophytes. Some chrys-
ophytes are amoeboid that attack bacteria by engulfing and destroying it.Diatoms
Diatomsare unicellular algae that have a hard, double outer shell made of silica.
Nutrients pass through pores in the shell, then through the diatom’s plasma mem-
brane contained within the shell. There are 5,600 known species of diatoms, most
of which are phototrophic and contain chlorophyll a and chlorophyll c pigments.
They also contain carotenoids, which are yellow and orange pigments. Some
diatoms are heterotrophsand break down and use organic matter as nutrients.
Diatoms accumulate at the bottom of the sea and are commercially mined for both
their value as an abrasive and their filtering and insulating capabilities (used in the
filters in pools).Dinoflagellates
Dinoflagellatesare unicellular algae that have the capability of self-movement
through the use of tail-like projections called flagella. The flagella are located
between grooves in the cellulose plates that cover the dinoflagellate’s body. These
flagella pulsate in both an encircling motion around the body and in a perpendi-
cular motion, causing the dinoflagellates to rotate like a top. There are about
1,200 known species of dinoflagellates that inhabit both fresh water and seawater.
Dinoflagellates live in seawater. Some are heterotrophs and break down
organic matter for nutrients. Some seawater dinoflagellates are luminous, giving
a twinkle to the sea at night. Freshwater dinoflagellates are phototrophic: They
synthesize nutrients from sunlight using photosynthesis.(^172) CHAPTER 11 The Eukar yotes