4. • Evolution has lead to a staggering
variety or organisms
• Biologists have identified and
named about 1.5 million species
so far
• They estimate anywhere between
2 and 100 million additional
species have yet to be discovered
6. Assigning Scientific Names
• By the 18th century, European
scientists recognized that
referring to organisms by common
names was confusing
• Common names vary among
regions within a country
11. Early Efforts at Naming
Organisms
• First attempts at standard scientific names
often described physical characteristics
• As a result, these names could be 20
words long!
• Ex.) The English translation of the
scientific name of a particular tree might
be “Oak with deeply divided leaves that
have no hairs on their undersides and no
teeth around their edges.”
14. Rules for Binomial
Nomenclature
• Written in italics
• First word is capitalized
• Second word is lowercased
Ex.)
Genus species
Genus species
G. species
15. • The name often tells you something
about the species
• Ex.) Tyranosaurus Rex
• Tyrant Lizard King
19. Linnaeus’s system of classification
uses seven taxonomic categories
Largest / Least
Kingdom Specific
Phylum
Class
Order
Family
Genus Smallest /
Most Specific
species
20. Mnemonic Device
Kingdom • King
Phylum • Phillip
Class • Came
Order • Over
Family • For
Genus • Good
species • Soup
23. Problems with Traditional Classification
• Sometimes, due to convergent
Evolution organisms that are quite
different from each other evolve
similar body structures
• Ex.) Crab, limpet, barnacle
24.
25. Evolutionary Classification
• Darwin’s theory of evolution
changed the entire way that
biologists thought about
classification
• Biologists now group organisms
into categories that represent
lines of evolutionary descent, not
just physical similarities
26. Classification Using
Cladograms
• Many biologists now prefer a
method called cladistic analysis
• This method of classification
identifies and considers only
those characteristics that arise as
lineages evolve over time
30. Similarities in DNA and RNA
• Suppose you were trying to compare
diverse organisms such as yeast and
humans
• It wouldn’t make sense to try to classify
anatomical similarities
• The genes of many organisms show
important similarities at the molecular level
• These similarities can be used as criteria
to help determine classification
• Ex.) Myosin in humans & yeast
31. Molecular Clocks
• Use DNA comparison to estimate
the length of time that two species
have been evolving independently
32. Molecular Clocks
• Mutations happen all the time at
about the same rate
• A comparison of DNA sequences in
two species can reveal how dissimilar
the genes are
• The degree of dissimilarity is an
indication of how long ago the two
species shared a common ancestor
35. • In taxonomy, as in all areas of
science, ideas and models change as
new information arises, some
explanations have been discarded
altogether, whereas others such as
Darwin’s theory of evolution by natural
selection, have been upheld
• So it should not be surprising that
since the 1800’s, the tree of life has
been revised and edited since the
discovery of all this new information
36. The Tree of Life Evolves
• Before Linnaeus’s time, the only
two Kingdoms that existed were
Plants and Animals
• As scientists discovered new
organisms that didn’t fit into the
plant or animal category, they
made a new category
37. The Old 5 Kingdom System
1. Animals
2. Plants
3. Fungi
4. Protist
5. Bacteria
38. • In recent years, as evidence
about microorganisms continued
to accumulate, biologists come to
recognize that the Monera were
composed of two distinct groups
39. The New 6 Kingdom System
1. Animals
2. Plants
3. Fungi
4. Protist
5. Eubacteria
6. Archaebacteria
40.
41. The Three Domain System
• Molecular analysis has given rise
to a new taxonomic category that
is now recognized by many
scientists
44. Domain Bacteria
• Unicellular
• Prokaryotic - no nucleus, no membrane
bound organelles
• Thick walls (containing peptigoglycan)
• Free living and parasitic
• Important decomposers
• Some photosynthesize
• Some don’t need oxygen
– Anerobic
• Some need oxygen
– Aerobic
52. • Acidophiles – live in acidic
environments
• Thermophiles – can tolerate hot
temperatures 50 – 110 degrees
• Halophiles – can stand extreme
concentrations of NaCl
• Methanogens – Produce methane
CO2 + H CH4
57. Protista
• Small
• Mostly unicellular
• Eukaryotic – has a nucleus, and
membrane bound organelles
• Cannot be classified as animals,
plants or fungi, but share many
characteristics with plants,
animals and fungi