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Chapter 17
Classification
17-1 The Linnaean System of Classification
Organisms must be classified because they are very numerous and diverse.
Taxonomy - the science of classifying organisms. A group of organisms in a classification
system is called a taxon.
Scientists classify organisms and assign them names.
Why do we need a system to classify and name organisms? Common names can be
confusing. Names vary among languages and even regions within a single country.
Examples of common names: Spider monkey, sea monkey, sea horse, crayfish, jellyfish,
black bear, firefly, mud puppy, horned toad
Carolus Linnaeus developed a two word naming system called binomial nomenclature. In
binomial nomenclature, each species is assigned one two part scientific name.
The scientific name is italicized or underlined. Ex. Homo sapiens
1st name – genus – capitalized
2nd name – species – lowercase
Linnaeus had 7 categories in his taxonomy: *p. 520 Fig. 17.3
Kingdom – the most general and largest category
Phylum
Class
Order
Family
Genus
Species - smallest and most specific category
A genus is composed of a number of related species.
A phylum is composed of similar orders.
Ex. Class Mammalia
Characteristics include warm-blooded, body hair, produce milk for their young.
*Scientists have identified and named only a fraction of all species.
Examples of classification:
Human
Kingdom
Animalia
Phylum/Division* Chordata
Class
Mammalia
Order
Primate
Family
Hominidae
Genus
Homo
Species
sapiens
Lion
Animalia
Chordata
Mammalia
Carnivora
Felidae
Panthera
leo
Tiger
Animalia
Chordata
Mammalia
Carnivora
Felidae
Panthera
tigris
Pintail Duck
Animalia
Chordata
Aves
Anseriformes
Anatidae
Anas
acuta
*Division is used instead of phylum in plants
**An organism in the same order would have to also be in the same class, phylum, and
kingdom.
17-2 Classification Base on Evolutionary Relationships
Traditional classification grouped organisms according to similarities in appearance. Now
organisms are grouped in categories that represent lines of evolutionary descent. They are
based on genetic relationships (DNA), some physical characteristics, and proteins.
Characteristics that appear in recent parts of a lineage, but not in its older members are
called derived characters. Derived characters are used to construct a cladogram (**p. 525)
A cladogram is a diagram that shows the evolutionary relationships among a group of
organisms.
Similar genes are evidence of common ancestry. All organisms use DNA and RNA to pass
on information. Classifying organisms based on derived characters allows organisms to be
classified how they are genetically related.
17-3 Molecular Clocks
Models that use mutations rates to measure evolutionary time. These provide clues to
evolutionary history. The more time that has passed since two species diverged from
a common ancestor, the more mutations will have built up in each lineage, and the
more different the two species will be at the molecular level. (p. 531 Fig. 17.9)
- Mitochondrial DNA – only inherited from the mother (closely related species)
- Ribosomal RNA – used for studying distantly related species (p. 532 Fig. 17.10)
17-4 Domains and Kingdoms (p. 535 Fig. 17.13)
Over the years, the kingdoms have changed. Classification is always a work in progress.
1700s – 2 Kingdoms – Plantae and Animalia
1800s – 3 Kingdoms – Protista, Plantae, Animalia
**Fungi was grouped with plants
1990s – 6 Kingdoms – Eubacteria, Archaebacteria, Protista, Fungi, Plantae, Animalia
Today, we have a new taxonomic category used by scientists – the Domain.
This category is bigger than a kingdom. There are currently 3 domains.
The prokaryotes - in the past, they were grouped together in Kingdom Monera.
(Bacteria) (p. 555-565)
Domain Bacteria – Kingdom Eubacteria (do have peptidoglycan in cell walls)
Domain Archaea – Kingdom Archaebacteria (no peptidoglycan)
The eukaryotes:
Domain Eukarya –
Kingdom Protista
Mostly unicellular organisms. Include algae, slime molds, paramecium, euglena, and other
single-celled water organisms. **p. 572 - 588
Kingdom Fungi
Mostly multicellular, heterotrophic organisms that digest their food outside their body.
They have threadlike filaments (hyphae) that make up their body (mycelium). Examples
include mushrooms, bread mold, yeasts. **p. 589 - 599
Kingdom Plantae
Multicellular, autotrophic organisms that have cell walls of cellulose and chloroplasts.
Ch. 20 - 22
Kingdom Animalia
Multicellular, heterotrophic organisms that have NO cell walls. Ch. 23 - 27
*Cladogram p. 703 Fig. 23.7
A. Cell specialization – as animals have evolved, their cells become specialized to
carry out different functions, such as movement and response.
B. Development - *p. 702 Fig. 23.6
C. Body symmetry - *p. 701
Asymmetry – no symmetry (sponges)
Radial symmetry – body plan in which body parts repeat around the center of the
body (ex. Sea anemones, Sea stars)
Bilateral symmetry – body plan in which only a single, imaginary line can divide
the body into two equal halves (ex. Worms, arthropods, chordates)
D. Cephalization –concentration of sense organs and nerve cells in the front of
the body.
E. Body cavity formation – fluid filled space that lies between the digestive tract
and body wall.
Domain
Bacteria
Archaea
Eukarya
Eubacteria
Archaebacteria Protista
Fungi
Plantae
Animalia
Prokaryote
Prokaryote
Eukaryote
Eukaryote
Eukaryote
Eukaryote
cell walls
with
Peptidoglycan
cell walls
without
Peptidoglycan
cell walls
with
cellulose
cell walls
with
chitin
cell walls
with
cellulose
NO
cell walls
unicellular
unicellular
mostly
unicellular
mostly
multimulticellular cellular
Multicellular
autotroph
or
heterotroph
heterotroph
autotroph
heterotroph
Asexual
spores or
budding
Sexual
gametes
Asexual
spores or
vegetative
reproduction
Sexual
gametes
Mosses
Ferns
Flowering
plants
Asexual
budding or
fragmentation
Sexual
gametes
Sponge
Worms
Fish
Mammals
Kingdom
Cell Type
Cell Wall
Structures
Number of
Cells
Mode of
Nutrition
autotroph
autotroph
or
or
heterotroph heterotroph
Reproduction Asexual
Binary
Fission
Asexual
Binary
Fission
Examples
Methanogens
Halophiles
Strep.
E. coli
Asexual
Mitosis or
Binary
Fission
Sexual
conjugation
Amoeba
Paramecium
Slime mold
Kelp
Algae
Mushroom
Bread mold
Yeast
Reproduction in the Kingdoms
Sexual reproduction: requires the union of 2 cells so that genetic information from each cell
is combined.
*Accomplished by the biological process meiosis.
o Advantages: offspring will be different from its parents (variation) which allows species to
adapt to its surroundings.
o Disadvantages: usually takes longer for the organism to develop; fewer numbers of
organisms are produced.
o Examples: Most animals reproduce sexually (fly, human, snake, frog)
o Examples: Flowering plants and plants that make seeds can reproduce sexually using
pollination (daffodil, grass, rose, oak tree).
1. Types: fertilization of gametes (sperm and egg)
2. Types: conjugation which is exchanging genetic information; done by
paramecia and some prokaryotes.
Asexual reproduction: involves only a single parent organism and produces an exact clone
of the parent.
*Accomplished by the biological process of mitosis.
o Advantages: occurs much quicker than sexual reproduction; produces more organisms
in a shorter period of time.
o Disadvantages: New organisms are genetically identical to parents, no variation in
offspring.
o Examples: small organisms, such as bacteria, paramecia, algae, hydras, sponges
reproduce mostly by asexual reproduction.
o Examples: some flowering plants can reproduce asexually (grass, strawberry, spider
plant).
o Types: Budding – when part of the cytoplasm breaks off from parent organism and
develops into a separate organism. (Amoeba, yeast, paramecium, hydra, spider plant)
o Types: Spore formation – haploid spores develop into new organism (fungi, mosses,
mushrooms, mold)
o Types: Binary fission – direct division of one cell into 2 smaller cells (bacteria,
paramecia, algae)
o Types: Vegetative propagation – part of the parent plant develops into a new plant
through runners, stem cuttings, underground stems (strawberry, geraniums, potatoes)
o Types: Regeneration – ability to re-grow or replace missing body parts due to predation
or damage (flatworms, sponges)