Download 17.4 Domains and Kingdoms

17.4 Domains and Kingdoms
KEY CONCEPT
The current tree of life has three domains.
17.4 Domains and Kingdoms
Classification is always a work in progress.
• The tree of life shows our most current understanding.
• New discoveries can lead to changes in classification.
– Until 1866: only two kingdoms,
Plantae
Animalia and Plantae
Animalia
17.4 Domains and Kingdoms
Classification is always a work in progress.
• The tree of life shows our most current understanding.
• New discoveries can lead to changes in classification.
– Until 1866: only two kingdoms,
Plantae
Animalia and Plantae
Animalia
– 1866: all single-celled
Protista
organisms moved to
kingdom Protista
17.4 Domains and Kingdoms
Classification is always a work in progress.
• The tree of life shows our most current understanding.
• New discoveries can lead to changes in classification.
– Until 1866: only two kingdoms,
Plantae
Animalia and Plantae
Animalia
– 1866: all single-celled
Protista
organisms moved to
kingdom Protista
– 1938: prokaryotes moved
to kingdom Monera
Monera
17.4 Domains and Kingdoms
Classification is always a work in progress.
• The tree of life shows our most current understanding.
• New discoveries can lead to changes in classification.
– Until 1866: only two kingdoms,
Plantae
Animalia and Plantae
Animalia
– 1866: all single-celled
Protista
organisms moved to
kingdom Protista
– 1938: prokaryotes moved
to kingdom Monera
– 1959: fungi moved to
own kingdom
Monera
Fungi
17.4 Domains and Kingdoms
Classification is always a work in progress.
• The tree of life shows our most current understanding.
• New discoveries can lead to changes in classification.
– Until 1866: only two kingdoms,
Plantae
Animalia and Plantae
Animalia
– 1866: all single-celled
Protista
organisms moved to
kingdom Protista
– 1938: prokaryotes moved
to kingdom Monera
– 1959: fungi moved to
own kingdom
Archea
Fungi
Bacteria
– 1977: kingdom Monera
split into kingdoms Bacteria and Archaea
17.4 Domains and Kingdoms
The three domains in the tree of life are Bacteria, Archaea,
and Eukarya.
• Domains are above the kingdom level.
– proposed by Carl Woese based on rRNA studies of prokaryotes
– domain model more clearly shows prokaryotic diversity
Analyze: Why did Woese
propose classifying
bacteria and archaea into
separate domains, rather
than just separate
kingdoms?
Analyze: Why are
protists, plants, fungi and
animals classified into the
same domain but into
different kingdoms?
The Tree of Life The most recent classification system divides life into three domains, which
include six kingdoms. The distances between branches are proportional to the number of
differences in rRNA sequences among these species.
17.4 Domains and Kingdoms
• Domain Bacteria includes prokaryotes in the kingdom
Bacteria.
– one of largest groups
on Earth
– classified by shape,
need for oxygen, and
diseases caused
Figure: The most common shapes of
bacteria are rods, spirals and spheres.
Many bacteria are named after their
shape like this one shown at the right.
Spirochaeta: spiral. (colored SEM;
magnification 5000 X)
17.4 Domains and Kingdoms
• Domain Archaea includes prokaryotes in the kingdom
Archaea.
– cell walls chemically
different from bacteria
– differences discovered by
studying RNA
– known for living in extreme
environments
Figure:Pyrococcus furiosus, can be found in undersea hot vents and
in the sand surrounding sulfurous volcanoes. These organisms live
without oxygen and can grow in temperatures higher than the
boiling point of water. (colored SEM; magnification 6500 X)
17.4 Domains and Kingdoms
• Domain Eukarya includes all eukaryotes.
– kingdom Protista
Figure: Zooflagellates have flagella that help them
move through water. (colored SEM; magnification
unknown)
17.4 Domains and Kingdoms
• Domain Eukarya includes all eukaryotes.
– kingdom Protista
– kingdom Plantae
Figure: The titan arum
plant produces a flower
that smells like carrion, or
rotting meat. Beetles that
eat carrion are attracted by
this odor and often wind
up pollinating the flower.
This ecological
relationship is an example
of commensalism.
17.4 Domains and Kingdoms
• Domain Eukarya includes all eukaryotes.
– kingdom Protista
– kingdom Plantae
– kingdom Fungi
Figure: Many sac fungi are sac- or cup-shaped or
have cupshaped indentations. Sac fungi include
moss cup fungi, also known as scarlet elf cups.
17.4 Domains and Kingdoms
• Domain Eukarya includes all eukaryotes.
–
–
–
–
kingdom Protista
kingdom Plantae
kingdom Fungi
kingdom Animalia
Figure: Sea cucumbers are fleshy animals
that live on the ocean floor.
17.4 Domains and Kingdoms
• Bacteria and archaea can be difficult to classify.
– transfer genes among themselves outside of
reproduction
bridge to transfer DNA
– blurs the line
between “species”
– more research
needed to
understand
prokaryotes
Figure: In conjugation, genetic material transfers between
prokaryotes, producing genetic variation. A conjugation bridge forms
from the donor cell to a recipient cell. (TEM; magnification 6000 X)