The Kingdom Protista

The Kingdom Protista Unit VI Chapter 20

What is a Protist? • A protist is any organism that is not a plant, an animal, a fungus, or a prokaryote • Protists are eukaryotes that are not members of the kingdoms Plantae, Animalia, or Fungi • The 1st eukaryotic organisms on Earth, appearing nearly 1/5 billion years ago, were protists • Protists are a diverse group that may incloude more than 200,000 species

Classification of Protists • Most protists are classified by their method of obtaining nutrients • Animal-like protists are heterotrophs • Plant-like protists photosynthesize • Fungus-like protists are parasites or decomposers

Animal-Like Protists: Protozoans • The 4 phyla of animal-like protists are distinguished from one another by their means of movement: • Zooflagellates – swim with flagella • Sarcodines – move by extensions of cytoplasm • Ciliates – move by means of cilia • Sporozoans – do not move on their own

Zooflagellates • Animal-like protists that swim using flagella are classified in the phylum Zoomastingina and are referred to as zooflagellates • Most have either 1 or 2 flagella (although some species have many)

Zooflagellates • Absorb food through their cell membranes • Most live in lakes and streams, although some live in the bodies of other organisms • Most reproduce asexually by means of binary fission, although some have a sexual life cycle

Sarcodines • Sarcodines are animal-like protists that use pseudopods for feeding and movement • Pseudopods (false feet) are temporary projections of cytoplasm • The best known sarcodines are amoebas • Amoeboid movement involves the cytoplasm of the cell streaming into the pseudopod allowing the rest of the cell to follow

Sarcodines • Amoebas can capture and digest particles of food and even other cells • To do this, they surround their meal and take it inside to form a food vacuole (a small cavity in the cytoplasm that temporarily stores food) • Amoebas reproduce by means of binary fission

Ciliates • Animal-like protists that move and feed by means of cilia are known as ciliates • Cilia are hair-like projections similar to flagella • Most ciliates are free living (non parasitic) • Some of the best known ciliates belong to the genus Paramecium

Ciliates – Internal Anatomy of the Paramecium • The cilia of a paramecium are organized into evenly spaced rows and bundles that beat in an efficient pattern • A paramecium’s cell membrane has trichocysts • small, bottle-shaped structures used for defense • Paramecium have a macronucleus • a working library of genetic information • Paramecium have a micronucleus • contains a reserve copy of all of the cells genes • Paramecium have a gullet • An indention in one side that traps food particles • Paramecium have an anal pore • Region of the cell membrane used to empty waste materials into the environment • Paramecium have contractile vacuoles • Used to collect and store excess water

Ciliate Reproduction • Under most conditions, ciliates reproduce asexually by mitosis and binary fission • However, when placed under stress, cilia may engage in conjugation • During conjugation, 2 cilia attach themselves to each other and exchange genetic information

Sporozoans • Members of the phylum Sporozoa are animal-like protists that do not move on their own and are parasitic • The sporozoan Plasmodium, which causes malaria, is carried by the female Anapheles mosquito • As many as 2 million people die from malaria each year • Other diseases caused by animal-like protists include: African Sleeping Sickness and Giardia

Plant-Like Protists: Unicellular Algae • The 4 phyla of plant-like protists that are grouped together as unicellular algae are: • Euglenophytes • Dinoflagellates • Chrysophytes • Diatoms

Chlorophyll & Acessory Pigments • One of the key characteristics used to classify algae is the type of photosynthetic pigments they contain • In adapting to conditions of limited light, various groups of algae have evolved different forms of chlorophyll • Chlorophyll a • Chlorophyll b • Chlorophyll c • Each form of chlorophyll absorbs different wavelengths of light • Many algae also have accessory pigmentsthat absorb light at different wavelengths than chlorophyll

Euglenophytes • Euglenophytes are plantlike protists that have two flagella but no cell wall • Euglenas have a cluster of reddish pigments known as an eyespot which function to help find sunlight for photosynthesis • Euglenas do not have a cell wall, but they do have an intricate cell membrane called a pellicle • Euglenas reproduce asexually by means of binary fission

Euglenophytes

Dinoflagellates • Dinoflagellates are plant-like organisms that can be photosynthetic or heterotrophic • Most have 2 flagella wrapped around in grooves between 2 thick plates of cellulose that protect the cell • Most reproduce asexually by binary fission • Many species are luminescent

Chrysophytes • Members of the phylum Chrysophyta are a diverse group of plantlike protists that have gold-colored chloroplasts • Includes yellow-green algae and golden-brown algae • Reproduction can be sexual or asexual

Diatoms • Diatoms are plant-like protists that produce thin, delicate cell walls rich in silicon (the main ingredient in glass) • Diatoms are among the most abundant organisms on Earth • Diatoms are beautiful!

Algal Blooms • Euglenophytes and other protists can grow rapidly in areas where sewage is discharged. • These rapid growths are known as algal blooms • Algal blooms quickly deplete the water of nutrients, and the cells of the bloom begin to die in great numbers • The decomposition of these dead algae can rob water of its oxygen, choking its resident fish and invertebrate life

Red Tides • Great blooms of the dinoflagellates have occurred in recent years on the east coast • These blooms are known as “red tides” • These species release a potentially harmful toxin that infect certain shellfish • Eating these infected shellfish can be harmful or fatal

Plant-Like Protists: Red, Brown, and Green Algae • The 3 phyla of algae that are largely multicellular are commonly known as red algae, brown algae, and green algae • A major difference among these phyla are their photosynthetic pigments

Red Algae • Red algae are plant-like protists that are members of the phylum Rhodophyta • Meaning “red plants” • Red algae are able to live at great depths due to their efficiency in harvesting reddish accessory pigments called phycobilins • Phycobilins absorb blue light, enabling red algae to live deeper in the ocean • Most red algae are multicellular and can live in waters from the polar regions to the tropics • Example: Chondrus crispus (irish moss)

Red Algae Chondrus crispus (Irish moss)

Brown Algae • Brown algae are plant-like protists that belong to the phylum Phaeophyta • Means “dusky plants” • Brown algae contain chlorophyll a and c, as well as a brown accessory pigment, fucoxanthin • All brown algae are multicellular and most live in cool, shallow, coastal marine waters • Examples: giant kelp, Sargassum, and Fucus

Brown Algae Giant kelp

Green Algae • Green algae are members of the phylum Chlorophyts • Means “green plants” • Green algae share many characteristics with plants, including their photosynthetic pigments and cell wall composition • Have cellulose in cell wall • Contain chlorophyll a and b • Store food in the form of starch • Green algae can be found in fresh or salt water • Some are single cells (ex: Chlamydomonas) • Some form colonies (ex: Volvox) • Some are multi-cellular (ex: Ulva)

Green Algae Chlamhydomonas unicellular green algae Volvox colonial green algae Ulva multicellular green algae

Human Uses of Algae • Ice creams • Salad dressings • Plastics • Waxes • Deodorants • Paints • Agar

Fungus-Like Protists • Fungus-like protists are heterotrophs that absorb nutrients from dead or decaying organic matter • Unlike true fungi, however, funguslike protists have centrioles and lack chitin in their cell wall • The fungus-like protists include: • Cellular slime molds • Acellular slime molds • Water molds

Slime Molds • Slime molds are fungus-like protists that play key roles in recycling organic material • They are found in damp places that are rich in organic matter, such as forest floors • The 2 groups of slime molds are: • Cellular slime molds (individual cells remain distinct) • Acellular slime molds (cells fuse to form larger cells during some life cycle phases)

Cellular Slime Molds • Cellular slime molds belong to the phylum Acrasiomycots • Individuals can form large slug-like colony that functions as a single unit during harsh times

Acellular Slime Molds • Acellular slime molds belong to the phylum Myxomycota • During the course of their life cycle, their cells fuse to produce structures with many nuclei known as plasmodia

Water Molds • Water molds are members of the phylum Oomycota • They thrive on dead or decaying organic matter in water and are plant parasites on land

The Kingdom Protista