Biology Chapter on Taxonomy & Classification

Taxonomy & Classification

• Linnaeus developed binomial nomenclature (two names) to classify organisms.
• Each organism has a genus and species name.
• Scientific names are written in italics or underlined. Only the first letter of the genus is capitalized.

Definitions

• Aerobes use oxygen to produce energy
• Obligate aerobes require oxygen to survive.
• Anaerobes don't need oxygen to produce energy.
• Obligate anaerobes can only live without oxygen.
• Facultative anaerobes can use oxygen or not.
• Anaerobic methanogens are bacteria that live in oxygen-free environments and release methane gas.

Kingdoms of Life

• Animalia: multicellular, heterotrophic, eukaryotic with cells lacking cell walls.
• Archaebacteria: prokaryotic, single-celled organisms genetically different from Eubacteria. Found in harsh environments.
• Eubacteria: prokaryotic, single-celled organisms; contains most bacteria species.
• Fungi: eukaryotic, multicellular, heterotrophic with cell walls containing chitin. Examples are mushrooms, yeasts and molds.
• Plantae: mostly multicellular, autotrophic organisms.
• Protista: mostly unicellular, eukaryotic organisms.

Key Terms

• Autotrophs: produce their own food.
• Heterotrophs: obtain energy from other organisms.
• Chitin: strong, waterproof carbohydrate found in arthropod exoskeletons and the cell walls of fungi.
• Chlorophyll: captures light energy in chloroplasts.
• Chloroplast: organelle that contains chlorophyll and converts sunlight to chemical energy in plants and some Protists.

Reproduction in Organisms

• Asexual Reproduction: one parent, offspring identical to parent. Mutations are the only source of genetic variation.
• Sexual Reproduction: two parents, offspring genetically different from parents. Crossing over and random assortment create genetic variation.

Viruses

• Viruses are not classified as a kingdom.
• Viruses are not alive.
• Viruses are parasitic and require a host for reproduction, nutrition, respiration, and other functions.
• Viruses can alter the host cell's genetic makeup.
• Lytic Cycle: a viral replication cycle that always ends with the lysis of the host cell.
• Lysogenic Cycle: viral DNA inserts into the host's DNA and is copied during cell division, delaying the release of new viruses.

Protists

• Eukaryotic organisms that appeared 1.5 billion years ago.
• Diverse species, making classification challenging.
• Protists are classified based on their nutrition.

Animal-like Protists

• Heterotrophic, unicellular, lack cell walls.
• Live in aquatic ecosystems, wet soil, or fluids within a host. Some are parasites.

Amoebas

• Single-celled, undefined body shape.
• Use pseudopods for movement.
• Feed using endocytosis. Some are parasites.

Paramecium

• Single-celled, uses cilia for movement.
• Cilia sweep food into the oral groove, which leads to a food vacuole.
• Waste is expelled through the anal pore.

Fungus-like Protists

• Heterotrophic, decomposers, feed via endocytosis.
• Live in cool, damp habitats.

Water Molds

• Filamentous.
• The whitish cottony mold found on dead fish.
• Saprophytic, consume dead organic matter. Caused the Irish Potato Famine.

Plant-like Protists

• Contains plastids and are photosynthetic.

Euglena

• Unicellular, freshwater organisms.
• Use flagella for movement.
• Can be autotrophic or heterotrophic.
• Have a red, light-sensitive structure called the eye spot.

Green Algae

• Photosynthetic.

• Single-celled, colonial, or multicellular.

• Bi-flagellated cells.

• Primarily live in freshwater.

• Chlamydomonas: single-celled.

• Volvox: colonial. Hundreds of connected singe, biflagellated cells form a hollow green sphere.

Fungi

• Characteristics: eukaryotic, multicellular, heterotrophic (saprophytic), cell walls containing chitin, reproduce both sexually and asexually.
• Hyphae are thread-like filaments that make up the body of most fungi.
• Mycelium: a tangled mass of hyphae that absorbs nutrients for food.

Classification of Fungi

• Classified based on sexual reproduction patterns:
  • Zygomycota: spores produced in a case-like structure (sporangium).
  • Ascomycota: spores produced in a sac-like structure (ascus).
  • Basidiomycota: spores produced in club-like structures (basidium).
• Spores: haploid reproductive cells.
• Sexual reproduction generally occurs under unfavorable conditions.

Examples of Fungi

Case-like Fungi (Zygomycota)

• Bread Mold: Asexual: hyphae extends along the surface and into food. Black sporangia form, releasing spores via wind. Sexual: zygospore forms upon contact and remains dormant until conditions improve. Two genetically different hyphae are produced.

Sac-like Fungi (Ascomycota)

• Penicillium: Alexander Fleming discovered penicillin, the first antibiotic. It releases a chemical that inhibits bacterial growth.
• Yeasts: unicellular fungi. Asexual: Occurs via budding in favorable conditions. Sexual: forms ascospores that remain dormant until conditions improve. Anaerobic respiration (fermentation) releases CO2 and ethanol as byproducts.

Club-like Fungi (Basidiomycota)

• Gilled Mushrooms: gills on the underside contain thousands of basidia, each with thousands of spores that are dispersed by wind.
• Imperfect Fungi: Examples include athlete's foot.

Fungal Associations

• Lichens: Symbiotic association of fungus with a cyanobacterium or algae. The algae provides food through photosynthesis, the fungus provides water, minerals, and protection from dryness.
• Mycorrhizae: Fungal mycelium forms a symbiotic association with plant roots. Mycelium forms a web over the plant roots and provides water and minerals from the soil while the plant roots provide amino acids and sugars.

Characteristics of Animals

• Heterotrophic, multicellular, eukaryotes.
• Specialized nervous and muscular tissues.
• Lack cell walls.
• Primarily sexual reproduction.

Classification of Animals

• Symmetry: Asymmetrical, bilateral, or radial.
• Cell Organization: cells function independently or form tissues and organs.
• Coelom: Presence of an internal body cavity.

Simple Animals

Phylum Porifera (sponges)

• Most primitive animals.
• All aquatic, mostly marine.
• Sessile, directly attached to a surface.
• Absorb water through tiny pores (ostia) and expel water through larger pores (oscula).
• Reproduction: sexually (hermaphrodites) and asexually (budding).

Phylum Cnidaria

• Radial symmetry.
• Cells organized into tissues.
• Examples: jellyfish, corals, anemones.