Characteristics of Eukaryotic and Prokaryotic Life Forms

Eukaryotes

The term Eukaryote comes from the Latin eu (good or true) and karyon (nucleus).

• These are cells possessing a true nucleus and a cell membrane. The DNA is contained within chromosomes inside the nucleus.
• They are generally large cells, ranging from 10 to 100 microns. While a few are unicellular or colonial, most form multicellular tissues.
• Reproduction is either asexual or sexual, with cell division occurring via mitosis. They possess a mitotic spindle or some form of microtubule-based organization.
• Eukaryotes are strictly aerobic for gas exchange with the environment, although some, like yeast, perform anaerobic fermentation.
• They feature cytoplasmic organelles, such as vacuoles, mitochondria, endoplasmic reticulum, and the Golgi apparatus. Ribosome particles are often associated with the endoplasmic reticulum.
• The age of these cells ranges from 1200 million years old to more recent forms.

Monera

Monera represents organisms with very small and simple structures.

• All are unicellular prokaryotes, lacking an organized nucleus and complex cellular organelles.
• Most are grouped into colonies.
• Their nutrition can be photosynthetic, chemosynthetic, or heterotrophic (fermenters).
• They reproduce by binary fission.
• Respiration is primarily through anaerobic fermentation, with a minority being aerobic.
• These are the oldest and most primitive organisms on the planet.
• They are classified as bacteria of the phylum Schizomycophyta.

Protista

The Kingdom Protista.

• Most are unicellular; others form multicellular colonies or simple structures.
• They possess a eukaryotic nucleus but lack specialized tissues.
• Both autotrophs and heterotrophs are present.
• Some move using flagella or cilia; others use pseudopods.
• Asexual reproduction occurs via cell division, budding, or spores. Sexual reproduction involves the formation of gametes.
• Their metabolism is aerobic, and they absorb nutrients through the cell membrane.

Fungi

Characteristics of the Kingdom Fungi.

• These are eukaryotic multicellular organisms.
• Their cells often contain more than one nucleus and exhibit filamentous structures.
• Structurally, they possess hyphae, mycelium, thallus, and rhizoids. Their cell walls are composed of chitin and cellulose.
• They lack chloroplasts and other photosynthetic pigments, feeding by absorbing matter from the environment.
• Fungi are obligate heterotrophs: most are saprophytic, others are obligate parasites, and some live in symbiosis with other organisms.
• They utilize aerobic respiration, exchanging gases through the cuticle.
• Asexual reproduction occurs by budding of shoots or buds, sometimes via spores and conidia.
• They are generally immobile, fixed to a substrate via rhizoids.
• This kingdom includes true molds, yeasts, and lichens, classified under the phyla Phycomycetes, Ascomycetes, Basidiomycetes, and Deuteromycetes.