Kingdom Protista and Diatoms

Kingdom Protista

• Protists are eukaryotic organisms with membrane-bound organelles and a nucleus
• They can be unicellular, colonial, or multicellular
• They exhibit diverse nutritional modes (autotrophic, heterotrophic, or mixotrophic)
• Primarily found in moist or aquatic environments
• Reproduce asexually and sexually
• Exhibit diverse morphologies, ranging from single-celled organisms to large multicellular forms (e.g., seaweeds)
• Play crucial ecological roles (producers, decomposers)
• Have economic importance (food, biofuels, industrial products)
• Some protists cause diseases (e.g., malaria) and serve as research models

Diatoms

• Unicellular algae characterized by silica-based cell walls called frustules
• Major components of phytoplankton, with roles in aquatic food webs and carbon cycling
• Two main types: centric (radial symmetry) and pennate (bilateral symmetry)
• Eukaryotic cells with photosynthetic organelles (chloroplasts) and other typical organelles
• Their distinctive frustules are valuable tools for identification
• Originated through secondary symbiosis, engulfment of a red alga

Brown Algae (Ochrophytes)

• Multicellular algae with cellulose walls
• Primarily found in marine environments, often forming kelp forests
• Asexual and sexual reproduction
• Exhibit a wide range of shapes and structures; varied morphological diversities

Red Algae (Rhodophyta)

• Mostly multicellular, seaweed-like organisms
• Thrive in warmer, deeper marine waters
• Contain pigments called phycobilins, giving them red coloration
• Often form delicate, feathery or branched structures
• Thallus - plant body of the algae
• Three types of thallus: male gametophyte, female gametophyte, tetrasporophyte
• Reproduce with non-moving gametes carried by water currents

Dinoflagellates (Dinophyta)

• Unicellular protists with cellulose plates called theca and two flagella
• Most are photosynthetic, though some are mixotrophic
• Important components of freshwater and marine ecosystems
• Some species produce toxins that can build up in shellfish (red tides)

Euglenoids

• Unicellular algae inhabit freshwater environments and some sewage treatment areas
• Spindle-shaped, without a rigid cell wall. Instead have a pellicle (elastic covering) for shape flexibility
• Two flagella: whip-like structures for movement and to detect light
• Some are photosynthetic, while others are heterotrophic
• Exhibit diverse nutritional modes (autotrophic, heterotrophic, or mixotrophic)

Slime Molds (Myxogastria)

• Heterotrophic
• Feeding via phagocytosis; absorb organic matter
• Some alternate between amoeboid, motile and stationary spore-producing stages
• Cell walls lack chitin

Water Molds (Oomycota)

• Saprotrophic or parasitic fungi-like protists.
• Cell walls primarily composed of cellulose.
• Reproduce using flagellated zoospores
• Often found in aquatic environments, damp soil, and as plant pathogens.

Kingdom Fungi

• Eukaryotic organisms
• Heterotrophic nutrition, absorb rather than ingest nutrients
• Cell walls composed of chitin
• Lack chlorophyll
• Absorptive nutrition
• Composed of network of filaments called hyphae creating mycelium
• Asexual and sexual reproduction using spores
• Store energy as glycogen.

Phylum Chytridiomycota

• Primarily aquatic, with some terrestrial species
• Uni or multicellular
• Produce flagellated zoospores, the only motile fungal spores
• Often considered the most primitive fungi, sharing evolutionary links with protists
• Saprophytic or parasitic, especially on amphibians (causing chytridiomycosis)

Phylum Zygomycota

• Primarily terrestrial, found in soil, decaying matter, or as parasites
• Coenocytic hyphae (multinucleate)
• Form a thick-walled zygosporangium during sexual reproduction to protect the zygospore under adverse conditions
• Asexually reproduce using sporangiospores
• Examples: Rhizopus (black bread mold), Mucor

Phylum Glomeromycota

• Mostly terrestrial, forming symbiotic relationships with plant roots
• Coenocytic hyphae
• Obligate symbionts, forming arbuscular mycorrhizae. These increase surface area and enhance water absorption
• Asexually reproduce through large, multinucleate spores
• No known sexual reproduction

Phylum Ascomycota

• Diverse habitats (soil, decaying matter, plants, and symbionts, including lichens)
• Septate hyphae (divided by cross walls)
• Distinguished by ascus (sac-like structure where sexual ascospores are produced) along with ascocarp (fruiting body surrounding the asci)
• Includes unicellular yeasts, molds, and more complex organisms like morels and truffles
• Reproduct asexually (conidia or budding)
• Reproduce sexually by producing ascospores in asci, often contained in ascocarps,

Phylum Basidiomycota

• Primarily terrestrial (forests, soil, decaying matter)
• Septate hyphae
• Distinguished by basidium (club-shaped structure that produces basidiospores) and often complex fruiting bodies like mushrooms, puffballs
• Asexual reproduction rare (conidia or fragmentation)
• Sexual reproduction involves basidiospores produced on basidia, usually on fruiting bodies

Phylum Microsporidia

• Obligate intracellular parasites, infect animals (especially insects and humans)
• Unicellular, lack typical fungal features like mitochondria
• Reproduce through spore formation using a polar tube to inject their genetic material into host cells

Lichens

• Symbiotic association of fungi and photosynthetic organisms
• Thallus - body of the lichen
• Three main types: crustose (crust-like), foliose (leaf-like), and fruticose (shrub-like)
• The fungal component is more readily identified and used for lichen classification

Bryophytes

• Non-vascular, non-flowering plants
• Thriving in moist, shady environments
• Requires water for fertilization
• Lack of true roots, stem, and leaves, instead have specialized root-like structures (rhizoids)
• Dominant gametophyte generation
• Reproduce via spores

Explore the fascinating world of Kingdom Protista, including the unique characteristics of protists and their crucial roles in ecosystems. Delve into diatoms, the unicellular algae known for their silica-based cell walls and significant contributions to aquatic food webs. This quiz will test your knowledge of these diverse organisms and their importance.