Classification of Organisms

Classification of Organisms

• Organisms are classified into a three-domain system: Bacteria, Archaea, and Eukarya.
• Classification criteria include cell type, method of food production, and cellular organization (unicellular or multicellular).

Domain Bacteria

• Bacteria thrive in diverse environments and can be autotrophs (produce their own food) or heterotrophs (consume other organisms).
• All bacteria are unicellular prokaryotes, lacking a nucleus.

Prokaryotes

• Prokaryotes are unicellular organisms without a nucleus, meaning their nucleic acids aren't enclosed in a membrane-bound structure.

Nucleus

• The nucleus is a dense cell area that houses nucleic acids, which are crucial for directing cellular activity.

Domain Archaea

• Archaea can inhabit extreme conditions, including deep ocean floors, hot springs, and volcanic environments.
• Like bacteria, Archaea are unicellular prokaryotes and can be autotrophs or heterotrophs.
• Archaea differ from bacteria chemically and structurally.

Domain Eukarya

• Organisms in the domain Eukarya are classified into four kingdoms: Protista, Fungi, Plantae, and Animalia.

Eukaryotes

• Eukaryotes are organisms with cells that contain a nucleus, distinguishing them from prokaryotes.

Kingdom Protista

• Includes all eukaryotic organisms that are not classified as fungi, plants, or animals, often referred to as the "odds and ends" kingdom.
• Members can be autotrophic or heterotrophic and vary from unicellular to multicellular.

Kingdom Fungi

• Comprises organisms like mushrooms, molds, and mildew, including both unicellular and multicellular forms.
• Fungi are heterotrophs that obtain nutrients by absorbing the remains of dead or decaying organisms.

Kingdom Plantae

• All plants are multicellular autotrophs that produce their own food via photosynthesis.
• They provide nourishment for many land-dwelling heterotrophs.
• Plant structures vary widely and possess cell walls made of cellulose.

Domain

• A domain is a high-level taxonomic category that includes all living organisms.

Kingdom Animalia

• All animals are multicellular heterotrophs with varying adaptations for locating, capturing, and digesting food.
• Animals inhabit numerous environments and distinctively lack cell walls.

Genus

• Genus is a taxonomic rank that follows family and groups together closely related species.

Species

• A species is a group of organisms that can interbreed and produce fertile offspring, indicating close genetic relationships.