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 1 st 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: 1. Zooflagellates – swim with flagella 2. Sarcodines – move by extensions of cytoplasm 3. Ciliates – move by means of cilia 4. 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: 1. Euglenophytes 2. Dinoflagellates 3. Chrysophytes 4. 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 pigments that 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