PROTISTS What is a Protist n Protists are

PROTISTS

What is a Protist? n Protists are eukaryotes that cannot be classified as animals, plants, or fungi n n n Recall: Eukaryotes have a nucleus and membrane-bound organelles All protists live in moist surroundings Protists=diversity n Examples of this n n n 1) 2) 3) Some are unicellular while others are multicellular Some are heterotrophs, some autotrophs, some both Some cannot move while others move extremely fast

What is a Protist? n n Due to this diversity, classifying these organisms has been extremely difficult Scientists have decided to classify them into the following 3 groups: n n n Animal-like protists Plantlike protists Fungus-like protists

Nutrition n n Many protists are autrophs, organisms that make their own food. Other protists are heterotrophs, organisms that must get their food by eating other organisms or their byproducts

Movement and Reproduction n n Protists use cilia, flagella, or pseudopodia to move. Reproduction is done either sexually, asexually, or both. n They reproduce asexually by binary fission and sexually by conjugation

Animal-Like Protists n n n Heterotrophs Most can move from place to obtain food Animal-like protists are also called protozoans Unicellular Protozoans can be classified into four groups, based on the way they move and live: n Protozoans: n n With Pseudopods With Cilia With Flagella That are parasites

Protozoans With Pseudopods n n Protozoans with pseudopods are known as sarcodines Sarcodines move and feed by forming temporary bulges in the cell-cytoplasmic streaming Pseudopod=false foot Pseudopods form when cytoplasm flows toward one location and the rest of the organism follows

Protozoans with Pseudopods n n Pseudopods enable sarcodines to move and trap food Some fresh-water sarcodines have a contractile vacuole n n A structure that collects the extra water and then expels it from the cell Ex) Amoeba

Protozoans with Cilia n n n Known as the Ciliates Use cilia, hair-like projections from cells, to move and obtain food Act like tiny oars Cells are complex Example n Paramecium

Paramecium n Paramecium are a ciliate that: n n Has two contractile vacuoles Has two nucleus n n n Large nucleus controls the cell Small nucleus functions in reproduction Reproduce mostly by binary fission but occasionally by conjugation

Protozoans with Flagella n n n Called the flagellates Protists that use long, whiplike flagella to move May have one or more flagella Some live inside other organisms (symbiosis) Others may harm its host it is in

Protozoans That Are Parasites n n n This group is characterized more by the way they live than their movements They are all parasites that feed on the cells and body fluids of their host Move in a variety of ways Many have more than one possible host Ex) n Plasmodium: protist that causes malaria

Plantlike Protists n n n Commonly called algae Extremely diverse Like plants, they are all autotrophs Most are able to use the sun’s energy to make their own food Some are unicellular while others may be multicellular

Plantlike Protists n n Some live in colonies of a few cells up to thousands of cells Wide variety of colors depending on their pigments n n Green, yellow, red, brown, orange, or even black Play a significant role in many environments

Diatoms n n Unicellular protists with glasslike cell walls Some float near the surface of water bodies while others attach to rocks in shallow water Can move by oozing chemicals out of slits in their cell walls and glide in the slime When they die, there cell walls collect on the bottom of oceans or lakes to form diatomaceous earth n Diatomaceous earth is used in household scouring products, insecticides, and as a polishing agent

Dinoflagellates n n n Unicellular algae surrounded by stiff plates that look like a suit of armor Variety of colors All have two flagella held in grooves between their plates When flagella beat, they twirl like toy tops as they move through the water They glow in the dark

Euglenoids n n n Green, unicellular algae found mostly in fresh water Can be heterotrophs under certain conditions but mainly autotrophs Consists of a flagellum, a nucleus, chloroplasts, eyespot (used to find light for photosynthesis)

Structure of a Euglena

Characteristics of Algae n n Algae can be unicellular, colonial, filamentous, or multicellular Seven Phyla of Plant-like protists: n n n n Chlorophyta Bacillariophyta Euglenophyta Phaeophyta Rhodophyta Dinoflagellata Chrysophyta

Red Algae n n n Almost all are multicellular seaweeds Found as deep as 260 meters; red pigment good for absorbing sunlight at low depths Substances extracted from red algae is used to make ice cream and hair conditioner

Green Algae n n n Very diverse Most are unicellular; some form colonies; others are multicellular Most live in either fresh or salt water Few live on land on rocks, crevices in tree bark, or in moist soils Very closely related to plants; contain same type of chlorophyll

Green Algae

Brown Algae n n Many organisms commonly called seaweed is brown algae Has plantlike structures Giant kelps are an example of brown algae Some substances in brown algae are used as thickeners in puddings and other foods

Funguslike Protists n Fungus are the “sort of like” organisms n n n Heterotrophs like animals; cell walls like plants Spore is a tiny cell that is able to grow into a new organism Have the ability to move at some time in their lives

Slime Molds n n Brilliant colored Live on forest floors and other moist, shady places Feed on bacteria and other microorganisms Produce spores when conditions become harsh

Water Molds and Downy Mildews n n n Both usually live in water or moist places Grow as tiny threads that look like fuzz Attack many food crops