protists 11

Protist Diversity

200,000 species come in different shapes, sizes, and colors

All are eukaryotes – have a nucleus and membrane-bound organelles

All protists are united on the basis that they are eukaryotes that are not fungi, plants or animals

Protozoans (Animal-like Protists)

Unicellular – made up of one cell

Heterotrophs – they eat other organisms or dead organic matter

Classified by how they move

Phyla of Protozoans

1. Amoebas

2. Flagellates

3. Ciliates

4. Sporazoans

1. Amoebas: the blobs

No cell wall

Move using pseudopods – plasma extensions

Engulf bits of food by flowing around and over them

2. Flagellates: the motorboats

Use a whip-like extension called a flagella to move

Some cause diseases

ex. Trichomonas vaginalis: an STD

3. Ciliates: the hairy ones

Move beating tiny hairs called cilia

Key organisms in aquatic environments. Predators of bacteria and protozoa.

Provide nutrition for organisms at higher trophic levels.

Have contractile vacuole

4. Sporazoans: the parasite

Non-motile - Do not move

Live inside a host

One type causes malaria (plasmodium)

Can be found in a variety of moist environments

* plasmodium is a class of sporazoan that have a life stage where cytoplasms fuse. Other organisms are known to also go into this state.

What are Algae?

Plantlike Protists

Multicellular and unicellular

Photosynthetic – make their own food

No roots, stems, or leaves

Each has chlorophyll and other photosynthetic pigments

Phyla of Algae

1. Euglenoids

2. Diatoms

3. Dinoflagellates

4. Red, Brown, & Green Algae

1. Euglenoids: The Survivors

They are one of the only unicellular plant-like organisms

Aquatic

Move around like animals – use flagella

No rigid cell wall

Can ingest food from surroundings when light is not available

Decomposers

Have contractile vacuole- collects and removes excess water

2. Diatoms: The Golden Ones

Have shells made of silica (glass)

Unicellular

Photosynthetic pigment called carotenoids – give them a golden color (autotrophic) (Their carotenoid pigments help them capture sunlight)

Primary food source for other organisms and play a role in energy and nutrient cycles

Produce much of Earth’s oxygen

3. Dinoflagellates: The Spinning Ones

Spin around using two flagella

Unicellular

Responsible for Red Tides

Create toxins that can kill animals and sometimes people

Some of them GLOW - bioluminescence

Important group of phytoplankton that help cycle nutrients

Red, green and brown Algae: 

Seaweeds

Multicellular, aquatic organisms

Have differing pigments that give colour

Produce oxygen

Found in aquatic environments, both marine and fresh water

The Brown Ones 

They have air bladders to help them float at the surface – where the light is.

Fungus-like Protists

All form delicate, netlike structures on the surface of their food source

Obtain energy by decomposing organic material externally and then ingesting the particles. (absorptive heterotrophs)

PhylaofFungus-like Protists (Molds)

1. Acellular Slime molds (Plasmodial)

2. Cellular Slime Molds

3. Water Molds & Downy Mildews

Slime Molds

Live in cool moist, shady places where they grow on damp, organic matter

1. Acellular Slime Molds

Form plasmodium: They lose their cell membrane to become a mass of cytoplasm that contains many diploid nuclei but no cell walls or membranes – its feeding stage

They essentially combine to become one HUGE cell

Creeps by amoeboid movement – 2.5 cm/hour

May reach more than a meter in diameter

Form reproductive structures when surroundings dry up (Instead of staying in their feeding stage, the plasmodium transforms into fruiting bodies (like spore-producing structures))

Spores are dispersed by the wind and grow into new plasmodium (These fruiting bodies release spores into the air. The wind carries them to new locations.)

2. Cellular Slime Molds

In feeding mode, they exist as individual amoebic cells

When food becomes scarce, they come together with thousands of their own kind to produce a large mass BUT still as individuals.

May look like a plasmodium

Exist as individual amoebic cells, each one separate.

When food is scarce → The individual cells come together (aggregate) into a big clump, but they don’t fuse. Each cell keeps its own membrane and identity.

The clump may look like a plasmodium, but it’s really thousands of amoebic cells acting as a team.

Example: Dictyostelium discoideum.

3. Water Molds and Downy Mildews

Live in water or moist places

Feed on dead organisms or parasitize plants

Some are fuzzy white growths

Over 700 different kinds

Water molds were responsible for the Irish potato famine in the 1840s. (It infected potato plants by spreading through spores in water and air, attacking the leaves, stems, and especially the tubers)

Over 30% of the Irish population either emigrated or died due to this