Unit 7 Honors Biology

Unit 7: Taxonomy and Viruses

Part 1: Taxonomy

  • Taxonomy Overview

    • All living things are categorized into various groups.

    • The scientific naming system was developed by Carolus Linnaeus in the 1750s.

    • Taxonomy is defined as the science of naming and classifying organisms.

    • Organisms are classified into hierarchical levels, with each level being more general than the one below it.

    • Each group within taxonomy is referred to as a taxon.

II. Binomial Nomenclature

  • Two-Name System

    • Bi-nomial nomenclature is a system that assigns each species a two-part scientific name derived from Latin.

    • The first part is called the genus, which includes one or more physically similar species believed to be closely related.

      • Genus names are always capitalized and are written in italics or underlined.

    • The second part of the name is the species, which generally describes the organism.

      • Species names may reflect the organism's native location, discoverer, or a characteristic trait.

III. Linnaeus’s Classification System

  • Levels of Classification

    • Linnaeus's system consists of seven traditional levels (now expanded to eight):

    • Order from most general to most specific:

      1. Domain

      2. Kingdom

      3. Phylum

      4. Class

      5. Order

      6. Family

      7. Genus

      8. Species

IV. Domains

  • Bacteria

    • Comprises single-celled prokaryotes, forming one of the largest and most diverse groups.

    • Classified based on shape, oxygen requirements, and pathogenicity.

  • Archaea

    • Also single-celled prokaryotes, known for survival in extreme conditions (e.g., deep-sea vents).

  • Eukarya

    • Includes all organisms with eukaryotic cells; can be single-celled or multicellular (e.g., protists).

V. Kingdoms under Domain Eukarya

  • Each kingdom varies significantly:

    1. Protista - Includes slime molds and amoebas.

    2. Plantae - Comprises plants.

    3. Fungi - Includes mushrooms and other fungi.

    4. Animalia - Comprises all animals.

VI. Classification Example

  • Example: Gray Wolf Classification

    • KINGDOM: Animalia

    • PHYLUM: Chordata

    • CLASS: Mammalia

    • ORDER: Carnivora

    • FAMILY: Canidae

    • GENUS: Canis

    • SPECIES: Canis lupus

    • Question: Analyzing which organisms (bats or cats) are more closely related to gray wolves based on classification.

VII. Limitations of Taxonomy

  • The classification system initially focused solely on physical characteristics.

  • Physical similarities do not always indicate actual genetic relatedness.

  • Modern taxonomy incorporates DNA analysis to establish the relationships between species.

Part 2: Viruses

I. Overview of Viruses

  • Definitions and Characteristics

    • Viruses are infectious particles comprised of a strand of DNA or RNA encased in a protein coat.

  • Characteristics associated with living organisms include the ability to:

    1. Reproduce

    2. Utilize nutrients and energy

    3. Grow and develop

    4. Respond to the environment

    5. Maintain homeostasis

    6. Adapt over time

    7. Have organized structures

  • Consider which characteristics viruses possess.

II. Viroids

  • Definitions

    • Viroids are infectious agents that cause diseases in plants.

    • Composed of single-stranded RNA without a protein coat.

III. Prions

  • Overview of Prions

    • Prions are infectious particles made solely of proteins, which induce misfolding in other proteins.

    • Example: Mad Cow Disease (Bovine Spongiform Encephalopathy).

    • Prions can have a long incubation period with no presentee of symptoms.

      • Symptoms, once detected, worsen rapidly and lead to fatalities due to the lack of immune response against proteins.

IV. Virus Life Cycle

  • Four Steps

    1. Entry: Virus binds to target receptor and merges with host cell membrane.

    2. Replication: Viral genetic material (RNA or DNA) gets replicated.

    3. Assembly: Viral proteins are produced and combined with viral genetic material.

    4. Egress: Mature viral particles exit through the host cell membrane.

Part 3: Dichotomous Keys

I. Identification Method

  • Dichotomous Keys: A systematic identification method that categorizes organisms into two groups repeatedly, leading to more specific classifications.

    • Organisms grouped together in a dichotomous key share more common characteristics.

II. Examples of Dichotomous Keys

  • Invertebrate Phyla

    • Asymmetrical vs. Symmetrical

      • Porifera: No visible segmentation.

      • Cnidaria: Radial.

      • Platyhelmintha: Exoskeleton vs. No exoskeleton.

      • Mollusca, Annelida, Arthropoda

  • Vertebrate Classes

    • Characteristics include fur, feathers, types of fertilization, and presence of gills in adults.

    • Classifications: Mammals, Birds, Reptiles, Fish, Amphibians.