Classification and taxonomy

Classification and Taxonomy

  • Classification is a method used by biologists to group and categorize species of organisms.

  • Taxonomy is the science that focuses on naming and classifying living organisms.

  • Understanding what an organism "is":

    • Typically involves intrinsic descriptions (external traits).

    • External characteristics include color, shape, and size.

    • Contrast with extrinsic descriptions, which refer to an organism's niche (its role in the ecosystem).

Hierarchical Scheme of Classification

  • A hierarchical scheme identifies approximately 1.7 million species of living organisms.

  • The binomial system of nomenclature was developed in the 18th century by Carolus Linnaeus, a Swedish botanist.

    • Each species is assigned a two-part name consisting of the genus and specific epithet.

  • Example: The proper scientific name is Scincella lateralis Say (1823).

  • The classification extends from species to domain, forming a structured approach to identifying organisms.

Taxonomic Classification Categories

  • Domains of life include:

    • Archaea

    • Eubacteria

    • Eukarya (includes Kingdoms: Protista, Fungi, Plantae, Animalia)

  • Example classification:

    • Domain: Eukarya

    • Kingdom: Animalia

    • Phylum: Chordata

    • Class: Mammalia

    • Order: Primates

    • Family: Hominidae

    • Genus and Species: Homo sapiens

The Phylogenetic Tree of Life

  • The phylogenetic tree illustrates evolutionary relationships among groups of organisms.

  • Organisms are categorized based on shared characteristics and common ancestry.

  • Notable groups include:

    • Bacteria

    • Archaea

    • Various Eucaryota (which further branches into plants, fungi, and animals).

  • A cladogram visually represents how organisms are related via specified characteristics, aiding in understanding taxonomy.

Diversity of Animalia

  • Arachnids are characterized by a cephalothorax and 6 pairs of appendages (chelicerae, pedipalps, and 4 pairs of walking legs).

  • Insects possess an exoskeleton, three main body parts (head, thorax, abdomen), and antennae.

  • Fish are aquatic, ectothermic vertebrates with scales and modified limbs for swimming.

  • Amphibians are vertebrates that require moisture, have smooth skin, and typically maintain three-chambered hearts.

    • Notable amphibians include frogs, salamanders, and caecilians.

    • Threat to Amphibians: Approximately one-third are currently threatened due to disease (e.g., chytrid fungus).

  • Reptiles have scales, claws on toes (except legless lizards), and are the first group to develop the amniotic egg.

Birds and Mammals

  • Birds are characterized by being endothermic, having feathers, four-chambered hearts, lightweight bones, and modified forelimbs as wings.

  • Mammals are endothermic vertebrates with hair or fur, lungs for breathing air, and milk for nourishing young.

Plants

  • Plants significantly shape landscapes and are commonly classified as either woody or herbaceous.

  • Various growth forms of plants include trees, shrubs, and vines.

Identification of Organisms

  • Dichotomous keys aid in species identification based on characteristics (e.g., scale counts in reptiles, leaf attributes in trees).

  • Leaf Shapes: Illustrated glossary includes various leaf shapes and arrangements critical for plant identification.

    • Common attributes include leaf tips (acuminate, obtuse, emarginate), bases (cordate, rounded), and arrangements (alternate, opposite).

Biodiversity Rank

  • States with various rankings for plant and animal diversity highlighting areas with the highest species counts:

    • Plants rank highest in California, followed by Texas, Arizona, etc.

    • Mammals also follow similar ranking patterns.