7.3 Protists Key Concepts: What are the characteristics of animal-like, plantlike, and funguslike protists? Key terms: protist, protozoan, pseudopod, contractile vacuole, cilia, symbiosis, mutualism, algae, spore

What is a protist? Protists are eukaryotes that cannot be classified as animals, plants, or fungi. Mostly it’s all the other stuff that aren’t those things. They are extremely diverse. Some unicellular, some multi, some autotrophs, some heterotrophs, etc Divided into three categories:

Animal-like protists Like animals, animal-like protists are heterotrophs, and are able to move around to get food. Protozoans (animal-like protists) Unicellular 4 kinds – pseudopods, cilia, flagella, parasites

Protozoans continued Protozoans that live in fresh water, like amoebas, have a problem: Small particles, like water, pass through the cell membrane into the cytoplasm So what? If excess water builds up inside the cell, the amoeba could BURST So they have contractile vacuoles – a structure that collects excess water and expels it (like you and your bladder)

Protozoans continued Some have symbiosis – a close relationship in which at least one of the species benefits Some have mutualism – where both partners benefit from living together

Protozoans with Pseudopods Pseudopods – temporary bulges of the cell – means “false foot” The pseudopods form when cytoplasm flows to one location Examples: sarcodines and amoebas

Protozoans with cilia Ciliates – have structures called cilia (hairlike projections from cells that move with a wavelike motion) They are used to move and obtain food Paramecia Use two contractile vacuoles More than one nucleus

Protozoans with flagella Flagellates – protists that use long, whiplike flagella to move. May have more than one. Some of them live inside bodies of other organisms

Protozoans that are parasites These are characterized more by the way they live than by the way they move They are all parasites that feed on the cels and body fluids of their hosts They move in a variety of ways Sometimes have more than one host

Plantlike Protists Commonly called algae – they are autotrophs Play a significant role in many environments by creating food and oxygen Vary in size Some unicellular, others multicellular, usually live in colonies Come in a wide variety of colors

Diatoms Unicellular protists with beautiful glasslike cell walls. Some float near the surface of lakes or oceans, others attach to objects like rocks Food source for heterotrophs When they die, their cell walls collect on the bottoms of bodies of water and create diatomaceous earth.

Dinoflagellates Unicellular algae surrounded by stiff plates that look like a suit of armor Have different amounts of green, orange, and other pigments ALL have two flagella held in grooves Twirl like tiny tops MANY glow in the dark

Euglenoids Green, unicellular algae that are found mostly in fresh water CAN be heterotrophic under certain conditions (usually autotrophs when enough light is present)

Red Algae Almost al red algae are multicellular seaweeds Red pigment good at picking up small amounts of light Used in a variety of ways by people (e.g. dyes)

Green Algae Green algae contains green pigments. Most unicellular Some form colonies Most live in fresh water or sea water Closely related to plants and use chlorophylls Some people think they should be in the plant kingdom, but they ain’t right now

Brown Algae “seaweeds” Has a lot of plantlike structures Flourish in cold waters Form forests underwater Often have gas filled sacs called bladders that allow them to float upright

Funguslike protists Your book refers to them as the “sort of like” organisms As in, they are sort of like all kinds of things. They are heterotrophs They have cell walls Most have spores – tiny cells able to grow into new organisms – to reproduce

Slime molds Often brilliantly colored, live in dark moist places Eat bacteria and other microorganisms Begin as tiny cells, use pseudopods to creep around Join together and grow to form a big jelly mass Release spores to make new slime molds

Water molds and downy mildews Most water molds and downy mildews live in water or moist places Grow as tiny threads that look like fuzz Attack food crops