Tree of Life
 Planet
Earth is about 4.6 billion years old.
 Oldest known rocks are about 3.8 billion
years old.
 Oldest fossils (prokaryotes) are about 3.5
billion years old.
Tree of Life
 All
living organisms on this planet share a
common ancestor.

The tree of life reflects the branching
pattern of speciation (phylogenetic history
of life) that has occurred since the origin of
life.
Tree of Life
 There
is an excellent Tree of Life website
in which you can trace the branching
pattern of the history of life and explore
classification.
 http://tolweb.org/tree/
Tree of Life
 There
is a hierarchichal classification of
life in which organisms are progressively
nested within larger and larger categories
as more distant relatives are included in
the classification (we will explore
classification shortly).
 The highest level of classification is the
Domain of which there are three.
26.22
Domains Bacteria and Archaea
 Domain
Bacteria
 Domain Archaea
 The
domains Bacteria and Archaea are
both prokaryotes (they have no nucleus
and the DNA is not arranged in
chromosomes). Prokaryote derived from
the Greek Pro meaning before and karyon
meaning a kernel [i.e. a nucleus]
Domain Bacteria
 Includes
most of the bacteria people are
familiar with including disease-causing
species (Salmonella; Vibrio cholerae
which causes cholera), nitrogen-fixing
(Nitrosomonas) and parasites (Borrelia
burgdorferi which causes Lyme disease).
Domain Bacteria
 Bacteria
play a major role in
decomposition and many live symbiotically
with other organisms including humans
helping to break down or synthesize foods
needed by the host.
Domain Archaea

The Archaea include many extremophiles,
organisms that live in extreme environments.

Includes thermophiles which tolerate extreme
heat (e.g. live in geysers and hot springs where
temps may reach 90 degrees celsius) and
halophiles (salt lovers, which live in very saline
environments (e.g. Great Salt Lake, Dead Sea)
Archaea in hot springs
Bacteria and Archaea
 Bacteria
and Archaea are both
prokaryotes and their DNA is arranged in
circular structures called plasmids.
 However, they have substantial
differences in their biochemistry, cell wall
structure and other molecular details.
Bacteria vs. Archaea


Bacteria are inhibited by antibiotics Streptomycin
and Chloramphenicol but Archaea are not.
Archaea in common with Eukarya have histone
proteins associated with their DNA, have introns
in their DNA, and have several kinds of RNA
polymerase. Bacteria lack these features.
 Archaea and Eukarya thus are members of a
clade.
Domain Eukarya
 Domain
Eukarya contains the eukaryotic
organisms (from Greek eu true and karyon
a kernal) which have a true nucleus and
DNA arranged in chromosomes.
 Eukaryotic
cells are much larger and
complex than prokaryotic cells and contain
organelles such as mitochondria,
chloroplasts, and lysosomes.
Domain Eukarya
 Domain
Eukarya includes three kingdoms
the Plantae, Fungi and Animalia.
 There
are also a number of unicellular
eukaryotes that may form as many as five
other kingdoms. These were formerly
grouped in the paraphyletic group the
Protista.
Domain Eukarya
 Plantae,
Fungi and Animalia are mostly
multicellular, but plants are autotrophic
(produce their own food by
photosynthesis) whereas the fungi and
animals are heterotrophic (consume other
organisms).
Plants
 Unlike
animals, plants remain in one place
and produce food through photosynthesis.
They trap the energy in sunlight and store
it in chemical bonds.
 The
energy stored in chemical bonds can
then be used to fuel metabolic processes.
Figure 10.2
Plants
 To
carry out photosynthesis plants must
obtain water and minerals from the soil,
CO2 from the air, and light from the sun.
 The
structure of plants reflects their need
to carry out these tasks.
Basic structure of plants
 Plants



have three basic organs:
Roots
Stems
Leaves
 These
organs are organized into two
systems: the largely below-ground root
system and the above-ground shoot
system (stems and leaves).
35.2
Fungi
 Fungi
are heterotrophs and feed by
absorption.
 They
secrete enzymes outside their
bodies (exoenzymes) which break down
complex molecules to simpler ones which
the fungus can absorb.
Fungi
 Some
fungi are unicellular (yeasts), but
most are multicellular.
 Body
of multicellular fungi made up of tiny
filaments called hyphae.
 The
hyphae form a mass called a
mycelium that penetrates the medium the
fungus is feeding on.
31.2
Fungi
 Mushrooms
and toadstools are the familiar
reproductive structures of fungi.
 Fungi produce spores which may be
sexually or asexually produced
Fungi
 Fungi
and Animalia share a more recent
common ancestor (about 1.5 billion years
ago) than they do with Plantae.
 Fungi
are believed to have evolved from
flagellated single-celled protistans, which
suggests multicellularity arose
independently in Fungi and Animalia
Animalia
 Since
zoology is the study of animals, the
kingdom Animalia is the focus of this
semester although we will briefly discuss
the single-celled protozaon groups.
Animalia

Animals are heterotrophic eukaryotes. Most are
multicellular.

Except for sponges all animals have tissues
which are specialized collections of cells
separated from other tissues by membranes.

Tissues are arranged together to produce
organs and organs are organized into organ
systems (e.g. digestive system).
Animalia
 Most
animals are bilaterally symmetrical
and form a large clade called the Bilateria.
 Bilateral
animals have a left and right side,
top and bottom, as well as front and rear
ends.
 A smaller
number are radially symmetrical
(e.g. jellyfish).