Protists & Fungi. KINGDOM PROTISTA All protists are eukaryotes. Most are unicellular, but some are multicellular. Some are heterotrophic, others are autotrophic.

Protists & Fungi

KINGDOM PROTISTA • All protists are eukaryotes. Most are unicellular,

but some are multicellular. Some are heterotrophic, others are autotrophic & some can switch back & forth. Protists were the first organisms to develop sexual reproduction & multicellularity.Most protists live in moist environments.

• There are 3 groups of protists: 1) plantlike protists called algae, 2) animal-like protists called protozoans, & •3) fungus-like

protists called slime molds.

ALGAE

•Algae are autotrophic. They are responsible for producing ~90% of the world’s oxygen. They vary greatly in size from microscopic to rubbery kelps. They serve as the basis for most aquatic food chains.Algae are classified according to color. There are 5 major groups of algae.

• 1. Golden Algae - Chrysophyta/Bacillariophyta – 12000 species – most of these are unicellular- the most common examples are the diatoms- these are small organisms made of silica that resemble glass-like boxes with lids & are used to make toothpaste, paint, Comet, filters, silver polish.

• 2. Fire Algae- Pyrrophyta/Dinoflagellata – 1100 species – responsible for red tides (this can paralyze/kill fish & other organisms) - these also exhibit bioluminescence- they give off light – have 2 flagella

• 3. Green Algae- Chlorophyta – 7000 species – thought to be ancestors of plants- common examples are Volvox, Spirogyra, Ulva

• 4. Brown Algae - Phaeophyta – 1500 species – also known as seaweed- many of these have air bladders- to help with flotation – common examples are Laminaria, Sargassum.

•5. Red Algae - Rhodophyta – 4000 species – can live at deep ocean depths (absorb green, violet, & blue light) - these can be used to make agar, ice cream, pudding, icing.

PROTOZOANS•These are

unicellular. They are classified based on their method of locomotion. They are also heterotrophs.

• 1. Rhizopods (also known as Sarcodines) – best example is amoeba- these organisms move using “false feet” called pseudopodia. They also use these for engulfing food. Amoebas reproduce asexually using binary fission.

• 2. Foraminiferans – (your book includes these with Sarcodines) also move using pseudopodia – have porous shells (tests) that look like snails – accumulate in limestone deposits – White cliffs of Dover

• 3. Ciliates - move using cilia – best example is Paramecium - these organisms ingest food through their oral groove. Contractile vacuoles help pump water out of the cell – have a protein coat called a pellicle (helps it to squeeze through tight areas). Many have 2 nuclei – a micronucleus (contain normal chromosomes that divide by mitosis) & a macronucleus (contains small pieces of DNA derived from micronuclei).

• 4. Flagellates (Zoomastigina)- move using flagella – many of these organisms have symbiotic relationships with other organisms – examples are Trypanosoma & trichonymphs. The choanoflagellates are thought to have given rise to sponges & thus all other animals.

• 5. Euglenophyta - freshwater protists w/ 2 flagella – some have chloroplasts & are photosynthetic & some can be heterotrophic & autotrophic – contain eyespots that detect light (phototaxic – moves toward the light) & an outer protein coat called a pellicle.

•6. Sporozoans- (Apicomplexa) these have no method of movement & are therefore all parasitic. The most common example is Plasmodium.

SLIME MOLDS • These are all heterotrophs &

resemble fungi. These begin their life as a slimy mass containing many nuclei. The mass is called a plasmodium & oozes across the forest floor. They are considered to be decomposers. When conditions become harsh, slime molds release spores. These germinate into flagellated cells that join & form a zygote that resembles an amoeba.

• 1. Acrasiomycota - cellular slime molds amoeba-shaped – form a slug when deprived of food

• 2. Myxomycota - stream along as a multinucleate mass of cytoplasm – give rise to spores when conditions are harsh

•3. Oomycota- unicellular parasites or decomposers – cell walls made of cellulose – water molds, white rusts, downy mildews – plant pathogens

KINGDOM FUNGI • Fungi are nonmotile organisms

that obtain food by decomposing organic matter. They lack chloroplasts & contain chitin in their cell walls. The body of a fungus is made of several thin, individual filaments called hyphae that contain cytoplasm & nuclei. These secrete enzymes that digest food. Digestion is performed extracellularly.

• The intertwined mass of hyphae is termed mycelium. It is a tangled mass primarily found under the substrate. The fruiting body is the visible portion of the fungus. Fungi are either saprophytic or parasitic.

• Fungi are classified according to method of reproduction. They are able to grow under a wide range of conditions which makes them annoying pests at times, but also helpful in baking, brewing, winemaking, cheesemaking, & antibiotics. All but yeasts are multicellular. Many fungi are saprophytic.

• Drawing of a typical fungus:

REPRODUCTION• Fungi reproduce by releasing

spores. These form asexually or sexually at the tips of the hyphae. Spores may be suspended in the air for long periods of time & can be carried great distances (ideal form of reproduction for organisms stationed in one area). Fungal spores are haploid(n).

Sometimes fungi contain 2 haploid nuclei, this is termed a dikaryon.

FOUR FUNGI PHYLA • 1. Zygomycota- also

known as zygote fungi – haploid nuclei from different mating types fuse to form diploid zygotes – develop into zygosporangia - have stolons that are surface hyphae & rhizoids that are like “mini-roots” (anchor the fungus) – most common example = black bread molds- usually has asexual reproduction with spores – has + & - mating strains

• 2. Ascomycota- form fine asexual spores – sexual spores in asci – hyphae divided by perforated septa – dikaryons – ex. = cup fungi, yeasts, red bread mold, morels, truffles, chestnut blight, Dutch elm disease.

• 3. Basidiomycota- reproduction is usually sexual – hyphae divided by septa – have a characteristic club-shaped reproductive structure ex.= mushrooms, puffballs, shelf fungi

•4. Deuteromycota- (Fungi Imperfecti) – no known sexual stage of life cycle – ex. = Penicillium, Athlete’s foot, ringworm, fungi used to make cheese, soy sauce

• 5. Chytridiomycota - motile cells with a single, whiplike flagellum

FUNGAL ASSOCIATIONS

• Symbiosis refers to a close relationship between 2 organisms. Fungi form symbiotic associations with plants, green algae, & cyanobacteria.

• 1. Lichens- mutualistic relationships between fungi (almost always ascomycetes) & cyanobacteria, green algae, or both; the photosynthetic partners live among the hyphae of the fungus; the fungus derives energy from its photosynthetic partners & cannot survive without them – the fungus provides minerals & protection from the environment for its partner – can live in harsh environments & are often known as pioneer organisms – sensitive to pollution – good indicators about the environment

• 2. Mycorrhizae- mutualistic relationships between fungi & the roots of plants; 80% of all plants have mycorrhizae associated with their roots;; the plant provides sugars to the fungi; in return, the fungi serve as accessory roots, greatly increasing the surface area available for the absorption of nutrients

2 types:

•1) Endomycorrhizae- mycorrhizae penetrate the plant root (probably led to the invasion of land by plants),

•2) Ectomycorrhizae- mycorrhizae wrap around the root – important for most trees