Chapter 8-1

What are Protists?

What are Protists? –the “Junk Drawer” kingdom

• A protist is a member of a group of eukaryotic organisms which have a membrane-bound nucleus.

• Most protists reproduce asexually, though some can reproduce sexually

• Protists are extremely diverse and share characteristics with plants, animals, and fungi but are not classified as any of these groups

What are Protists?• General characteristics-

– Most are unicellular, but some, such as the giant kelp, are multicellular & can grow to be as big as 100 meters

– Live in moist surroundings– Some move and some don’t– Some can make their own food, while others are

consumers or decomposers– They are classified by how they obtain food

• Scientists classify protists as plant-like, animal-like, or fungus-like based on which group they most resemble.

Three kinds of Protists-

• Plant-like

• Animal-like

• Fungus-like

Plant-like Protists

• Like plants, these protists use chlorophyll for photosynthesis – (takes place in chloroplasts)

• Almost all live in water• Examples include:

– Algae– Diatoms– Dinoflagellates– Euglenoids

Plant-like Protists- Algae• Algae are plant-like protist that

perform photosynthesis. They can be either multicellular or unicellular.

• Red algae

– Used to make ice cream, marshmallows & shampoo

• Brown algae

– Known as “seaweed”

• Green algae

Plant-like Protists- Diatoms

• A type of microscopic plantlike protist with a hard outer wall is a diatom

– Unicellular with glasslike cell walls– Used in silver polish, toothpaste & insulation

Plant-like Protists- Dinoflagellates

• Dinoflagellates are unicellular plantlike protists that use flagella to move.

– They have many pigments so they come in several colors

– They have 2 flagella that allow them to swirl around as they move

– They glow in the dark & look like fireflies at night

Plant-like Protists- Euglenoids• A Euglenoid is a unicellular plant-like

protist that has a flagellum at one end of its body. It has no cell wall. Instead it has a rigid rubbery coat called a pellicle.

• Euglenoids

– Have eyespots that

respond to changes in

light• Tell the euglena when to perform photosynthesis

– Produce food by photosynthesis

Click on the image below to observe a Euglena swimming with it’s flagella

The importance of Algae• Algae provide food for

animals and animal-like protists, and provide shelter for many aquatic organisms such as sea otters.

• They are plant-like but have holdfasts rather than roots.

• Algae can help remove pollution from the water.

•Pollution can be a food source for algae, allowing the population of algae to increase quickly.•This overproduction can lead to Red Tides, which can be dangerous to other aquatic animals & humans

Algae are thought to cause Red Tides

Animal-like Protists: Protozoans

• Protozoans are protists that resemble tiny animals

• Protozoans are unicellular and mostly live in wet environments.

• Protozoans do not have chloroplasts and cannot make their own food.– They are consumers and some are parasites

Animal-like Protists- Ciliates

• Cilia are short, hair-like structures that grow on the surface of some protists.

• Protists with cilia are called Ciliates.

• Cilia cover the surface of the cell and move a protist through water.

• Ciliates reproduce asexually, but they can exchange some genetic material through a process called conjugation.

Animal-like Protists- Ciliates

• A paramecium is a protist with cilia and two types of nuclei.

• A paramecium gets its food by forcing water into the oral groove in its side.

Click on the video below to observe a paramecium feeding!

Animal-like Protists- Flagellate

• A Flagellate is a type of protozoan with one or more flagella.

• Flagellates eat decaying matter.

Animal-like Protists- Sarcodines• Sarcodines are animal-like protists with

no specific shape.

• An amoeba is one common Sarcodine.

• An amoeba moves and obtains nutrients by using pseudopods, which means temporary or false foot.

• Amoeba form pseudopods by slowly pushing their cytoplasm against the soft, flexible cell membrane.

Animal-like Protists: Protozoa cont’• Amoeba use their pseudopods to engulf

their food and form a food vacuole

• They are found in soil, salt & fresh water, and use a contractile vacuole to get rid of excess water

Click on picture below to observe an Amoeba in action!!!

The Importance of Protozoans:Some protozoans are parasites and can cause disease like malaria.

Animal-like Protists: Protozoa cont’

• Spore forming protist, Plasmodium

Fungus-like Protists• Funguslike protists share many

characteristics with fungi.

• Slime molds are funguslike protists composed of cell material and nuclei floating in a slimy mass.

• Most slime molds absorb nutrients from other organic matter in their environment.

Funguslike Protists • A water mold is a

funguslike protist that lives as a parasite or feeds on dead organisms.

• Slime molds and water molds usually reproduce sexually when environmental conditions are harsh or unfavorable.

• Funguslike protists play a valuable role in the ecosystem by breaking down dead plants and animals, making nutrients available for living organisms.

• Many funguslike protists attack and consume living plants.

• Water mold destroyed more than half of Ireland’s potato crop in 1845

Importance of Funguslike Protists