Biology: Domains of Life - Archaea and Eubacteria

• Biologists have identified about 1.4 million species.
• Three-fourths of the identified species are animals.
• There are an estimated 4-30 million undescribed species.
• Biologists classify and name organisms for communication.
• Ribosomal RNA is used to study the evolution of early life.
• Ribosomal RNA's evolutionary conservation property is its slow rate of change.
• All life shares a common ancestor
• Life is divided into three evolutionary lineages called domains, which supersede kingdoms.

The Three Domains

• Archaea, Eubacteria, and Eukarya are the three domains.

Archaea

• Archaea are prokaryotic microbes.
• Archaea live in extreme environments like high-temperature rift valleys and high salt or acidic environments.
• All Archaea inhabit anaerobic environments.
• Archaea are the most primitive life forms.
• The ancient Archaean gave rise to the other two domains.

Eubacteria

• Eubacteria are true bacteria.
• Eubacteria are prokaryotic.
• Eubacteria lack a cell-membrane-enclosed nucleus and membranous structures.

Eukarya

• Eukarya includes all eukaryotic organisms.
• The classification system is based on Whittaker's (1969) system.
• The classification uses cellular organization and mode of nutrition.

Five Broad Categories of Living Things

• Kingdom Monera, Kingdom Protista, Kingdom Fungi, Kingdom Plantae, and Kingdom Animalia are the five broad categories.

Kingdom Monera

• Monera are prokaryotic.
• Monera are unicellular.

Bacteria

• Bacteria are the most abundant organisms.
• Bacteria can be chemosynthetic, photosynthetic, saprobic, or parasitic.
• Bacteria have a widespread distribution, including deserts, hot springs, glaciers, seas, hydrothermal vents, soil, human gut, skin, and deep underground (2,780 meters).
• Some bacteria are beneficial decomposers, recyclers of nature that influence the global cycling of nitrogen, sulfur, and other nutrients.
• Lactobacillus is a bacteria that is used in the production of pickles, sauerkraut, yogurt, and buttermilk.
• Actinomycetes are used in pharmaceuticals such as antibiotics
• Some bacteria are harmful pathogens and cause decay in goods like carbon-rich foods and fruits.

Cyanobacteria (Blue-green algae)

• Cyanobacteria are photosynthetic.
• Cyanobacteria live in moist places on land, fresh and marine water.
• Cyanobacteria are producers in the food chain and the main component of phytoplankton.
• Phytoplankton produces 50% of atmospheric oxygen (O2).

Kingdom Protista

• Protista are predominantly unicellular.
• Protista are eukaryotic.

Plant-like Protists

• Plant-like protists include euglenoids, diatoms, and golden-brown algae.
• Plant-like protists have chlorophyll and are photosynthetic.

Animal-like Protists: Protozoa

• Protozoa lack chlorophyll and are heterotrophic.
• Protozoa are motile through cilia, flagella, or amoeboid movement.
• Examples of Protozoa include: Amoeba, Plasmodium spp., and Paramecium.

Kingdom Fungi

• Fungi are eukaryotic.
• Fungi are predominantly sedentary.
• Fungi can be saprobic/saprobiotic or parasitic.
• Some fungi are unicellular (yeast), while others are multicellular (bread and fruit molds, mushrooms).
• Fungi are used in baking, brewing (Saccharomyces cereviseae), as decomposers, and can cause diseases.
• Fungi damage property, and are partners with bacteria in natural decay acting like recyclers.

Kingdom Plantae

• Plantae are mostly multicellular.
• Plantae are eukaryotic.
• Plantae have rigid cell walls made of cellulose.
• Plantae contain chlorophyll and are photosynthetic.

Brown Algae (Phaeophyta)

• Brown algae appear olive green, golden, or dark brown, with the pigment fucoxanthin.
• Macrocystis and Laminaria are commercially harvested for products like ice cream, pudding, jelly beans, salad dressing, and cough syrup.
• Alginic acid from cell walls is used to make algins, used as thickening, emulsifying, and suspension products.
• Brown algae are consumed in the Far East as food, mineral source and fertilizer.

Red Algae (Rhodophyta)

• Red algae are red due to the pigment phycoerythrin.

• Carrageenan, from Irish moss, is used as a thickening agent in dairy products.

• Funori is used as laundry starch, hair dressing adhesive, and in water-based paints.

• Agar from Gelidium is used as a laboratory culture medium.

• Phaeophyta and Rhodophyta are marine and referred to as seaweed.

Green Algae (Chlorophyta)

• Green algae contain chlorophyll and live in water or moist environments.
• Green algae range from unicellular to multicellular types.
• Mosses, liverworts occur in very moist habitats.
• Vascular plants include Ferns, Gymnosperms and Angiosperms.
• Ferns reproduce using spores.
• Gymnosperms are cone-bearing plants like cycads and pines.
• Angiosperms are flowering plants, monocots and dicots.

Kingdom Animalia

• Animalia are multicellular and eukaryotic.
• Animalia lack a rigid cell wall.
• Animalia lack chlorophyll.
• Animalia exhibit heterotrophic nutrition by ingesting food particles.

Sponges (Porifera)

• Sponges have no symmetry, tissues, or organs, use tough fibers and glass-like spicules.
• Examples of Sponges include common bath sponges and Venus flower baskets.

Coelenterates

• Coelenterates are primitive animals with radial symmetry.
• Examples of Coelenterates include: jellyfish, sea anemones, Hydra.

Flatworms

• Flatworms are bilaterally symmetrical, with distinct dorsal and ventral surfaces, as well as distinct anterior and posterior ends.
• Examples of Flatworms include parasitic flukes and tapeworms, and the free-living Planarian Dugesia.

Mollusks

• Mollusks are complex animals abundant in oceans and freshwater.
• Most have shells (snails, clams, scallops, oysters).
• Some mollusks lack shells (slugs, squid, octopus).

Annelids (Segmented Worms)

• Annelids are segmented worms, with bodies divided into visible units.
• Examples of Annelids include earthworms and Nereis (a marine worm).

Arthropods

• Arthropods have jointed legs and are considered the most successful organisms.
• Arthropods have the greatest number of species (mostly insects).
• Arthropods produce the most offspring, occupy the most habitats, fend off predators, and exploit large amounts of food.
• Living lineages include chelicerates (spiders), crustaceans (barnacles and crabs), and uniramians (centipedes, millipedes, insects).

Echinoderms

• Echinoderms are marine animals with radial symmetry.
• Examples of Echinoderms include sea stars/starfishes, sand dollars, sea urchins, and sea cucumbers.

Chordates

• Chordates have an internal bony skeleton, particularly a backbone, and a dorsal hollow nerve cord.
• Examples of Chordates include fish, amphibians, reptiles, birds, and mammals.

Explore the classification of life into three domains: Archaea, Eubacteria, and Eukarya. Learn about the characteristics of Archaea, including their extremophile nature and primitive origins, and Eubacteria, the true bacteria. Understand the evolutionary relationships and shared ancestry of all life forms.