- The document discusses the evolution of biological classification systems from Linnaeus's two-kingdom system to the modern three-domain system. It describes the levels of taxonomy from smallest to largest and characteristics used to classify organisms, including evolutionary relationships revealed by DNA evidence. The three domains are Bacteria, Archaea, and Eukarya, with Eukarya containing the kingdoms Protista, Fungi, Plantae, and Animalia. Classification systems continue adapting to new genetic and molecular evidence.
3. 18-1 Finding Order in Diversity
Natural selection and other processes have
led to a staggering diversity of organisms.
Biologists have identified and named about
1.5 million species so far.
They estimate that 2–100 million additional
species have yet to be discovered.
4. To study the diversity of life, biologists
use a classification system to name
organisms and group them in a logical
manner.
5. In the discipline of taxonomy, scientists
classify organisms and assign each
organism a universally accepted name.
When taxonomists classify organisms,
they organize them into groups that have
biological significance.
6. Assigning Scientific Names
Common names of organisms vary, so
scientists assign one name for each
species.
Because 18th century scientists
understood Latin and Greek, they used
those languages for scientific names.
This practice is still followed in naming
new species.
7. Early Efforts at Naming Organisms
The first attempts at standard scientific
names described the physical
characteristics of a species in great detail.
These names were not standardized
because different scientists described
different characteristics.
8. Carolus Linneaus developed a naming
system called binomial nomenclature.
In binomial nomenclature, each
species is assigned a two-part
scientific name.
The scientific name is italicized.
9. The first part of the name is the genus
name (Capitalized).
A genus is a group of closely related species.
The second part of the name is the
species name (lowercase).
The species name often describes an important
trait or where the organism lives.
10. Linnaeus's System of Classification
Linnaeus not only named species, he also
grouped them into categories.
11. Linnaeus’s seven levels of
classification are—from smallest to
largest—
• species
• genus
• family
• order
• class
• phylum
• kingdom
12. Each level is called a taxon, or
taxonomic category.
Species and genus are the two
smallest categories.
Grizzly
bear
Black
bear
22. Biologists currently group organisms into
categories that represent lines of
evolutionary descent, or phylogeny, not
just physical similarities.
Grouping organisms based on
evolutionary history is called
evolutionary classification.
23. The higher the level of the taxon, the further
back in time is the common ancestor of all
the organisms in the taxon.
Organisms that appear very similar may not
share a recent common ancestor.
24. •Different Methods of Classification
Appendages Conical Shells Crustaceans Mollusk
Crab Barnacle Limpet Crab Barnacle Limpet
Molted external
skeleton
CLASSIFICATION BASED ON
VISIBLE SIMILARITY CLADOGRAM
Segmentation
Tiny free-
swimming larva
Active Art
25. Superficial similarities once led barnacles
and limpets to be grouped together.
Appendages Conical Shells
Crab Barnacle Limpet
26. However, barnacles and crabs share an
evolutionary ancestor that is more recent
than the ancestor that barnacles and
limpets share.
Barnacles and crabs are classified as
crustaceans, and limpets are mollusks.
27. Many biologists now use a method called
cladistic analysis.
•Cladistic analysis considers only
new characteristics that arise as
lineages evolve ( called derived
characters).
•Characteristics that appear in recent parts of a
lineage but not in its older members are called
derived characters.
28. Derived characters can be used to
construct a cladogram, a diagram
that shows the evolutionary
relationships among a group of
organisms.
Cladograms help scientists understand how
one lineage branched from another in the
course of evolution.
29. A cladogram shows the evolutionary
relationships between crabs, barnacles, and
limpets.
Crustaceans Mollusk
Crab Barnacle Limpet
Tiny free-swimming larva
Molted external skeleton
Segmentation
30. The genes of many organisms show
important similarities at the molecular level.
Similarities in DNA can be used to help
determine classification and evolutionary
relationships.
31. DNA Evidence
•DNA evidence shows evolutionary relationships of
species.
•The more similar the DNA of two
species, the more recently they shared a
common ancestor, and the more closely
they are related in evolutionary terms.
•The more two species have diverged from each
other, the less similar their DNA is.
32. Molecular Clocks
•Comparisons of DNA are used to mark
the passage of evolutionary time.
•A molecular clock uses DNA
comparisons to estimate the length of
time that two species have been evolving
independently.
34. A molecular clock relies on mutations to mark
time.
Simple mutations in DNA structure occur
often.
Neutral mutations accumulate in different
species at about the same rate.
Comparing sequences in two species shows
how dissimilar the genes are, and shows
when they shared a common ancestor.
36. The Tree of Life Evolves
•Systems of classification adapt to new
discoveries.
•Linnaeus classified organisms into two
kingdoms—animals and plants.
•The only known differences among living
things were the fundamental traits that
separated animals from plants.
37. There are enough differences among
organisms to make 5 kingdoms:
•Monera
•Protista
•Fungi
•Plantae
•Animalia
39. The six-kingdom system of
classification includes:
•Eubacteria
•Archaebacteria
•Protista
•Fungi
•Plantae
•Animalia
40. Changing Number of Kingdoms
Introduced Names of Kingdoms
1700’s
Late 1800’s
1950’s
1990’s
Plantae Animalia
Protista Plantae
Monera Protista Fungi Plantae
Eubacteria
Archae-
bacteria
Animalia
Animalia
AnimaliaProtista Fungi Plantae
41. The Three-Domain System
•Molecular analyses have given
rise to the three-domain system
of taxonomy that is now recognized
by many scientists.
•The domain is a more inclusive category
than any other—larger than a kingdom.
42. The three domains are:
•Eukarya, which is composed of
protists, fungi, plants, and animals.
•Bacteria, which corresponds to
the kingdom Eubacteria (true
bacteria).
•Archaea, which corresponds to
the kingdom Archaebacteria.
43. Modern classification is a rapidly changing
science.
As new information is gained about
organisms in the domains Bacteria and
Archaea, they may be subdivided into
additional kingdoms.
44. Domain Bacteria
•Members of the domain Bacteria are
unicellular prokaryotes.
•Their cells have thick, rigid cell walls that
surround a cell membrane.
•Their cell walls contain peptidoglycan.
46. Domain Archaea
Domain Archaea
•Members of the domain Archaea are
unicellular prokaryotes.
•Archaea live in extreme
environments.
•Their cell walls lack peptidoglycan, and
their cell membranes contain unusual
lipids not found in any other organism.
50. Domain Eukarya
Protista
•The kingdom Protista is composed of
eukaryotic organisms that cannot be
classified as animals, plants, or fungi.
•Its members display the greatest variety.
•They can be unicellular or multicellular;
photosynthetic or heterotrophic; and can
share characteristics with plants, fungi,
or animals.
51. Fungi
•Members of the kingdom Fungi are
heterotrophs with cell walls that
contain chitin.
•Most fungi feed on dead or decaying organic
matter by secreting digestive enzymes into it
and absorbing small food molecules into their
bodies.
•They can be either multicellular (mushrooms) or
unicellular (yeasts).
52. Domain Eukarya
Plantae
•Members of the kingdom Plantae are
multicellular, photosynthetic autotrophs.
•Plants are nonmotile—they cannot move
from place to place.
•Plants have cell walls that contain cellulose.
•The plant kingdom includes cone-bearing
and flowering plants as well as mosses and
ferns.
53. Domain Eukarya
Animalia
•Members of the kingdom Animalia are
multicellular and heterotrophic.
•The cells of animals do not have cell walls.
•Most animals can move about.
•There is great diversity within the animal
kingdom, and many species exist in nearly
every part of the planet.
54. Which statement about classification is true?
a. Biologists use regional names for organism
b. Biologists use a common classification
system based on similarities that have
scientific significance.
c. Biologists have identified and named most
species found on Earth
d. Taxonomy uses a combination of common
and scientific names to make the system
more useful.
55. Linnaeus's two-word naming system is
called
a. binomial nomenclature.
b. taxonomy.
c. trinomial nomenclature.
d. classification.
57. A group of closely related species is
a(an)
a. class.
b. genus.
c. family.
d. order.
58. Which of the following lists the terms in
order from the group with the most
species to the group with the least?
a. order, phylum, family, genus
b. family, genus, order, phylum
c. phylum, class, order, family
d. genus, family, order, phylum
59. Grouping organisms together based on
their evolutionary history is called
a. evolutionary classification.
b. traditional classification.
c. cladogram classification.
d. taxonomic classification.
61. In an evolutionary classification system,
the higher the taxon level,
a. the more similar the members of the
taxon become.
b. the more common ancestors would be
found in recent time.
c. the fewer the number of species in the
taxon.
d. the farther back in time the common
ancestors would be.
62. Classifying organisms using a
cladogram depends on identifying
a. external and internal structural
similarities.
b. new characteristics that have
appeared most recently as lineages
evolve.
c. characteristics that have been
present in the group for the longest
time.
d. individual variations within the group.
63. To compare traits of very different
organisms, you would use
a. anatomical similarities.
b. anatomical differences.
c. DNA and RNA.
d. proteins and carbohydrates.
64. Organisms whose cell walls contain
peptidoglycan belong in the kingdom
a. Fungi.
b. Eubacteria.
c. Plantae.
d. Archaebacteria.
65. Multicellular organisms with no cell
walls or chloroplasts are members of
the kingdom
a. Animalia.
b. Protista.
c. Plantae.
d. Fungi.
66. Organisms that have cell walls
containing cellulose are found in
a. Eubacteria and Plantae.
b. Fungi and Plantae.
c. Plantae and Protista.
d. Plantae only.
67. Molecular analyses have given rise to a
new taxonomic classification that
includes
a. three domains.
b. seven kingdoms.
c. two domains.
d. five kingdoms.
68. Which of the following contain more
than one kingdom?
a. only Archaea
b. only Bacteria
c. only Eukarya
d. both Eukarya and Archaea
