AlgaeDo Now: Begin reading the introduction to the

algae on your museum visit handout.

Algae are aerobic photoautotrophic eukaryotes.

They contain chloroplasts and mitochondria.

Almost all of them are aquatic.

Algae may be unicellular, colonial, or multicellular. Multicellular forms are not as complex as land plants.

What is an Alga?

Algae are the main producers in aquatic ecosystems.

Without algae, there would be nothing for heterotrophs to eat!

Why are they important in Ecology?

How are they related to other organisms?

Algae are a diverse group of organisms, with diverse classification and evolutionary history.

A few of the more important types are explored here.

What different types are there?

Diatoms are best known for their beautiful silica shells.

They are unicellular, and are common in fresh and salt water.

Also, they produce oils!

Diatoms

Dinoflagellates are very similar to diatoms, because they are unicellular and have a silica shell.

The major difference between the two is that dinoflagellates have flagella for movement

Some kill sea life.

Dinoflagellates

Brown algae are multicellular algae that contain pigments other than chlorophyll.

They are commonly known as kelp.

Brown Algae (Phaeophyta)

Red algae are similar to brown algae, except that they have different pigments, giving them their characteristic red color.

Agar, and other polysaccharides come from these organisms

Red Algae (Rhodophyta)

Chlorophytes contain chlorophyll, have cellulose cell walls, and thus as a group are most similar to more familiar land plants

Green Algae (chlorophyta)

Earth Hisory

Algae and Protists Diversify

Fossils. These multicellular fossils are

from a rock formation in Southern China, and are some of the best preserved early eukaryotes ever discovered.

The rock formation has been dated to 551-635 MYA.

The journal article presenting the fossil describes 7 different isotope dating techniques that confirm this range.

How do we know?

Some species of algae are colonial in nature.

Colonial organisms are different from truly multicellular organisms because individual cells can survive in the environment if separated from the rest of the organism.

Colonial Organisms

Some algae may reproduce asexually or sexually, depending on environmental factors

Algae Sex