Chapter 19: Classification of Organisms

Biodiversity

Biological variety of organisms

• Thousands of new species discovered each year

• Organized according to what makes sense

Taxonomy

System of naming and classifying organisms based on shared characteristics and universal rules

First classification system

• Made by Aristotle

• Common names were used to describe the organisms

• Animals were classified into land, water, and air animals

• Plants were classified into stem or no stem

• Problems:

  • Confusing

  • Language differences

  • Not descriptive

Carolus Linnaeus (1701-1778)

• Botanist, zoologist, taxonomist, physician

• “Father of Modern Taxonomy”

• Developed and organized classification system

• Formalized naming system

• Most general - most specific

Taxon

A particular group within the taxonomic system

• Domain

• Kingdom

• Phylum

• Class

• Order

• Family

• Genus

• Species

Binomial nomenclature

Two-part naming system, gives each organism a scientific name

• Latin roots

• Common between all languages

• Includes genus and species of each organism

• Ex: Homo sapiens

• Rules:

  • First letter of first word capitalized

  • First letter of each following word lower case

  • Italicized if typed

  • Underlined if hand written

  • Ex: Ursus maritimus

• Scientific name different for each species

Subspecies

Variations of a species that live in different geographic subpopulations

• Additional name that follows species identifier

• Ursus americanus americanus: Eastern black bear, north Easter U.S. (our area)

• Ursus americanus floridanus: Southern black Bear, south eastern U.S. (Florida, Georgia, Alabama)

Phylogeny

Study of the evolutionary system of lineages of organisms

• Groups species into larger categories to reflect evolutionary descent

Phylogenetic diagram

“Family tree” of the origin of an organisms or a group

• Indicates how close organisms are thought to be

• Hypothesis

• Can be changed at any time

• Parts of phylogenetic diagram:

  • Root - represents ancestral lineage

  • Branch point or nodes - represents separation, single ancestral lines give rise to two or more daughter lines

    • Each lineage has a part of its history that is unique to it alone and parts that are shared with other lineages

    • Similarly, each lineage has ancestors that are unique to that lineage and ancestors that are shared with other lineages

Clade

A grouping that includes a common ancestor and all the descendants (living and extinct) of that ancestor

• Clades are nested within one another (nested hierarchy)

• A clade may include many thousands of species or just a few

Cladistics

System of phylogenetic analysis comparing carefully selected traits to determine the order in which organisms branched off from their common ancestor

• Shared and derived characteristics

• DNA

Shared character

Features that all members of a group have in common

• Ex: all birds have feathers

Derived characters

Features that evolved in some members of a group

• Ex: some birds have rounded beaks

Losing traits

• Distantly related organisms can lose traits

• Absence of characteristic is not used in analysis

Cladogram

Phylogenic diagram based on derived characteristics

• More closely related groups share a more recent common ancestor

• Construction:

  1. Organize information in a data table

  2. Convert to a cladogram

Domains

• Broadest level of classification

• Three major lineages for all living things

  • Bacteria

  • Archaea

  • Eukarya

Domain Bacteria

• Small, unicellular, prokaryotic

• Thick cell walls containing peptidoglycan

• Can be autotrophs or heterotrophs

• Ex: streptococcus, E. coli

Domain Archaea

• Small, unicellular, prokaryotic

• Cell walls without peptidoglycan

• Can be autotrophs or heterotrophs

• Unique biochemical properties

• Live in extreme environments

  • Deep seas, Arctic environments, volcanic vents, etc.

• Possibly the oldest living organisms

• Ex: halophiles, methanogens

Domain Eukarya

• Large-celled, unicellular or multicellular, eukaryotic

• Cells contain nucleus and complex cell organelles

• Diverse organisms

  • Plants

  • Animals

  • Fungi

  • Protists

Kingdoms

• Domains align with 6 kingdoms

• Characteristic based on cell type, reproduction, metabolism

  • Eubacteria

  • Archaebacteria

  • Protista

  • Fungi

  • Plants

  • Animals

Eubacteria

• Prokaryotic, unicellular

• Autotrophs or heterotrophs

• Classified into groups based on shape

  • Bacilli: rod-shaped bacteria

    • Listeria

  • Spirilla: spiral-shaped bacteria

    • Leptospirosis

  • Cocci: sphere-shaped bacteria

    • Staph

Archaebacteria

• Prokaryotic, unicellular

• Autotrophs or heterotrophs

• Unique biochemical properties

• Classified into groups

  • Methanogens

  • Halophiles

  • Thermoacidophiles

Methanogens

Organisms that convert hydrogen gas and carbon dioxide into methane gas

• Live without oxygen

• Found in deep fresh water, sewage, marine mud, intestinal tracts of some animals

Halophiles

Organisms that live in environments with high salt concentrations

• Live in salt concentrations 5 times greater than the oceans

• Found in Dead Sea, Great Salt Lake

Thermoacidophiles

Organisms that live in very acidic, high temperature environments

• Found in volcanic vents, hot springs

Protista

• Eukaryotic, unicellular (some colonial), or multicellular

• Can be autotrophs or heterotrophs

• Some contain cell walls

• Some contain chloroplasts

• Very diverse group, organisms are fundamentally different from one another, hard to define

• Ex: amoeba, slime molds, giant kelp

Fungi

• Eukaryotic, unicellular, or multicellular

• Heterotrophs, by absorption

• Contain cell walls made of chitin

• May be as many as 1.5 million species

• Ex: mushrooms, yeasts, molds

Plants

• Eukaryotic, multicellular

• Autotrophs

• Contain cell walls made of cellulose

• Have chloroplasts

• Ex: mosses, ferns, flowering plants

Animals

• Eukaryotic, multicellular

• Heterotrophs

• No cell walls

• Very diverse group, range in size and physical structure

• Ex: fish, insects, mammals, etc.

Mammals

• Kingdom: Animalia

• Phylum: Chordata

• Class: Mammalia

• Characteristics:

  1. Endothermic - regulation of body heat through metabolism (warm-blooded)

  2. Hair, most are covered

  3. Heart is divided into 4 chambers

  4. Mammary glands - milk producing glands to feed offspring

  5. Lower-jaw made of a single bone

  6. Various types of teeth for different functions (if teeth are present)

Birds

• Kingdom: Animalia

• Phylum: Chordata

• Class: Aves

• Characteristics:

  1. Covered in feathers, essential for flight and insulation

  2. Forelimbs are wings

  3. Light-weight skeleton (bones are hollow)

  4. Rapid metabolism, energy for flight and temperature regulation

  5. Beaks, no teeth

  6. Oviparity - amniotic eggs in a hard shell

Reptiles

• Kingdom: Animalia

• Phylum: Chordata

• Class: Reptilia

• Characteristics:

  1. Ectothermic - regulation of body heat through external environment (cold-blooded)

  2. Bodies covered in scales

  3. Ear hole to pick up vibrations

  4. Oviparity (most) or live births

Amphibians

• Kingdom: Animalia

• Phylum: Chordata

• Class: Tetrapoda

• Characteristics:

  1. Thin, slimy skin without scales

  2. Ectothermic (cold-blooded)

  3. Feet (if present) lack claws and are webbed

  4. Live in water (aquatic larval stage) and on land (terrestrial adult stage)

  5. Use gills, lungs, and skin (primarily) for respiration

  6. Eggs lack shells

  7. Most have eggs fertilized external of the body

Virus

Non-living particle made of proteins, nucleic acids (DNA or RNA), and some lipids

Cells vs. Viruses

Cells

• Structure: cell membrane and organelles

• Reproduction: cell division

• Growth/development: yes

• Metabolism: yes

• Respond to environment: yes

• Change over time: yes

Viruses

• Structure: DNA or RNA with proteins and lipids

• Reproduction: only in host cell

• Growth/development: no

• Metabolism: no

• Respond to environment: no

• Change over time: yes

Stucture and composition of a virus

• Can only be seen with electron microscope

• Genetic information can be DNA or RNA

  • May have few or hundred of genes

• Capsid - protein coat surrounding virus

Viral infections

• Contain surface proteins to gain access to host cell

• Virus makes copies of itself inside host cell

  • May spread to other cells

  • May destroy host cell

• Two patterns of infection

  • Lytic

  • Lysogenic

Lytic infection

Virus enters a host cell, makes copies of itself, and causes the cell to burst (lyse)

• Viral genes transcribed and translated in host cell

• New viruses assemble

• Virus free to infect other cells

• Ex: flu, common cold

Lysogenic infection

Host cell is not immediately taken over, viral genes are copied and inserted into host’s DNA

• Viral genes transcribed and translated in host cell

• Little/no production of new viruses

• Can become an active lytic infection

• Ex: chicken pox (varicella)