Domains and Kingdoms

and required information about Plants, Fungi, and Mutualisms

domain Bacteria

These are part of the large group of organisms commonly called "bacteria." They include the blue-green algae (= cyanobacteria), purple sulfur bacteria, etc., as well as most of the more familiar decomposing and disease-causing bacteria.

General Characteristics

• Unicellular, absorptive-heterotrophic, photoautotrophic, or chemoautotrophic prokaryotes.
• Only one set of genes, usually in a single-stranded loop.
• Lack sexual reproduction.
• Several chemical types of cell walls.
• Lack organelles such as centrioles, eukaryotic flagella, cilia, mitochondria, and chloroplasts.
• Some bacteria have a unique type of rotating flagellum.
• Photoautotrophic species have chlorophyll, but not chloroplasts (which are organelles that are separated form the surrounding cytoplasm by their own membranes).

domain Archaea

These are also part of the large group of organisms commonly called "bacteria."   Most of the thermophilic (hot-water-loving) and halophilic (brine-loving) organisms belong here, as well as sulfur-oxidizers that are mutualists with animals (such as Pogonophora) near submarine hot water vents, and the anaerobic decomposers that produce methane from organic wastes such as sewage and landfills.
Includes chemoautotrophic, photoautotrophic, and absorptive-heterotrophic (decomposer) metabolic types; does not include pathogens or the typical, aerobic decomposers of soils and underwater sediments.

General Characteristics

• Prokaryotic like Bacteria, but biochemicals of cell walls, proteins associated with DNA, and some metabolic pathways are different from Bacteria.
• Genetically more similar to Eukarya than to Bacteria.
• Tolerate harsher environments than most other prokaryotes and all eukaryotes.

domain Eukarya

General Characteristics:

• Nuclei surrounded by membranes.
• Organized chromosomes that arrange on a mitotic spindle at mitosis and undergo meiosis for sexual reproduction.
• Often have a standard, eukaryote flagellum of the "9 + 2"-fiber design in some life stage, and Golgi apparatus.
• All those that we will cover in ZO 150 have the organelles called mitochondria, but several other, eukaryotic kingdoms lack them.
• All the eukaryotes that are photoautotrophic have membrane-bound organelles called chloroplasts.

Eukaryotic organisms not classified into candidate kingdoms.

For ZO 150, you must simply know that many amebas and zooflagellates belong to other kingdoms. This includes the sponge-like choanoflagellates, which are in an unnamed kingdom that is equally related to Fungi and Animalia by the most recent genetic studies.

kingdom Euglenozoa

General Characteristics:

• Unicellular and flagellated, and flagella not fringed.
• May be parasitic (pathogenic) or free-living.
• Nutrition may be ingestive or absorptive heterotrophic, or mixotrophic (both photosynthesis and ingestive heterotrophy).
• Cell wall, when present, does not contain cellulose.

kingdom Alveolata

General Characteristics:

• Flattened sacs called alveoli just beneath the cell membrane.
• Unicellular ingestive heterotrophs or mixotrophs.
• Cilia, flagella, or ameboid locomotion in some or all life stages.
• Free-living or parasitic (including pathogens - such as the apicomplexan Plasmodium that causes malaria).
• Includes all the ciliates, such as Paramecium.
  
• Includes the environmental pests that cause "red tides" in the ocean (such as Gymnodinium) and fish kills in local estuaries (Pfiesteria).  Some of the dinoflagellates have cellulose cell walls.

kingdom Stramenopila

General Characteristics:

• Unicellular (mostly) or simply multicellular (such as kelp).
• Many have flagellated life stages, in which case the flagella have a fringe of fine filaments.
• Photoautotrophic (diatoms, brown seaweeds such as kelp), mixotrophic (many golden algae), or absorptive heterotrophs (saprozooic and parasitic water molds).
• Some, including water molds, have cellulose cell walls.
• Diatoms and golden algae protect the cells with exterior cases or scales made of silica.

kingdom Rhodophyta

General Characteristics:

• Unicellular, mostly colonial, or simply multicellular.
• Exclusively photoautotrophic.
• Have relatively large amounts of reddish, accessory photosynthetic pigments in addition to chlorophyll that are similar to certain cyanobacterial pigments.
• Never possess flagella or cilia.
• Chloroplasts were derived from primary symbiosis cyanobacteria. (This statement was corrected and now agrees with textbook, on 9/7/04)
  
• Cell walls made of cellulose.

kingdom Viridiplantae

General Characteristics:

• Unicellular (either solitary or colonial), or multicellular.
• Almost exclusively photoautotrophic.
• A few are absorptive heterotrophic parasites.
• All photoautotrophic members have chloroplasts, surrounded by a single membrane and ultimately derived from symbiotic cyanobacteria.
• All have cellulose cell walls, constructed chemically in a way that is unique to this kingdom.
• Many (specifically excluding seed plants) have haploid, flagellated life stages or gametes.

kingdom Fungi

General Characteristics:

• Unicellular (yeasts and chytrids) or multicellular (mushrooms), absorptive heterotrophs.
• Chitinous cell walls.
• All nuclei are haploid except during brief zygote stages during sexual reproduction
• Cell membranes between nuclei in hyphae are incomplete or absent for most of the life cycle.
• Lack flagella and cilia.
• Except the most ancestor-like group, chytrids, which have flagellated sperm.

kingdom Animalia

General Characteristics:

• Multicellular, usually ingestive heterotrophs
• A few are capable of, and may rely primarily on, absorptive heterotrophy.
• Some (phylum Annelida, class Pogonophora) depend entirely on chemoautotrophic mutualists for energy.
• Cell walls and chloroplasts entirely absent.
• Many look green because they harbor intracellular or intercellular, mutualistic algae.
• Often have an intercellular class of proteins called collagens.
• Most animals (except sponges) have specialized muscle and nerve cells.
• Locomotion by ameboid movement, flagella, cilia, or muscles.
Many species have flagellated sperm.

Required Information About Viridiplantae and Fungi

Within the Viridiplantae, know relationships and distinctions among:

• green algae
• mosses
• ferns
• seed plants:
• gymnosperms
• angiosperms

Know general characteristics of these fungal growth forms:

(which are neither taxonomic nor phylogenetic groups)

• yeasts
• molds
• mushrooms

Examples of Inter-Kingdom Mutualisms

lichens
Fungi + green algae (Viridiplantae), or blue-green algae (Bacteria)
The fungus provides nutrient minerals, protection from drying, excess sunlight, and grazers for the alga, while the green or blue-green alga produces carbohydrates for the fungus by photosynthesis.

mycorrhizae (singular, mycorrhiza)
multicellular, rooted Viridiplantae + Fungi
The mycorrhizal fungus decomposes and transports mineral nutrients and water from soil into plant root cells much more efficiently than the plant root cell could do itself, while the fungus obtains carbohydrates for energy from the plant's root cells.

rhizobia (singular, rhizobium)
vascular Viridiplantae + nitrogen-fixing Bacteria
The rhizobial bacterium lives in plant root nodules and converts nitrogen gas (N₂) from soil air into ammonia (NH₃) as a nutrient for the plant, while the bacterium obtains carbohydrates for energy from the plant's root cells.

stony or reef-forming corals
Animalia (anthozoan cnidarians) + dinoflagellates (photosynthetic Alveolata) called "zooxanthellae."
The coral animal provides inorganic nutrients to the alga by capturing and digesting prey and releasing carbon dioxide from tissue respiration, while the alga produces carbohydrates for the animal by photosynthesis. 

termites and ruminant artiodactyls:
Animalia + flagellates (of several kingdoms), ciliates (Alveolata), and bacteria (Bacteria)
Protozoan and bacterial symbionts live in the animal's gut and digest cellulose and lignin for their host, while being maintained in a protected, moist environment and supplied constantly with fresh organic substrate (food) by the animal.  Many other kinds of herbivorous and detritivorous animals also have mutualistic bacteria to aid them in digesting cellulose and synthesizing vitamins and essential amino acids that they cannot synthesize for themselves.  Anaerobic archaeans also live in these gut communities and produce methane, but this chemical does not benefit the other members.

vent worms
Animalia (Pogonophora, and also a few bivalves and polychaetes) + Archaea (sulfide-oxidizers)
Prokaryotic symbionts live in a special organ of pogonophoran vent worms called the trophosome, which completely replaces the digestive tract of these gutless wonders.  The worm collects the dissolved sulfides (reduced, black sulfur compounds) that issue from submarine vents by using its tentacles with large surface areas and circulating blood containing hemoglobin.  The hemoglobin binds (just as it would to oxygen or carbon monoxide) and partially detoxifies the sulfides, then transports them to the trophosome.  The worm provides a steady supply of inorganic chemical substrate to the chemoautotrophic archaeans, which oxidize it to sulfate and use the released energy to synthesize biochemicals.  Pogonophorans use biochemical secretions and digested cells of archaeans as energy, and may also obtain energy by absorbing soluble biochemicals directly from the mud around them (absorptive heterotrophy).

pollination mutualisms
flowering Viridiplantae and insects, birds and bats (Animalia)
Many flowering plants provide nectar and excess pollen to animals as food, in exchange for the animals' transfer of the otherwise immobile pollen to the stamens of other plants or blossoms for sexual reproduction.  The animals tend to specialize in one particular species of flower, which greatly increases the likelihood that the pollen they carry will reach another plant or flower of the same species, where it can fertilize the ovule.  Some pollination mutualisms are obligatory, while others are more flexible.

seed dispersal mutualisms
seed-bearing Viridiplantae and insects, birds or mammals (Animalia)
Gymnosperms and angiosperms (collectively called spermatophytes) provide excess seeds or nutritious fruit as food for the animals, while the animals may bury some seeds they never recover, or pass undigested seeds through their guts and defecate them in new locations where the plant is likely to be able to germinate and survive, along with a little fertilizer.

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Maintained by Sam Mozley (click to send me E-mail)

Last modified on September 7, 2004