Transcript Lecture 6 - Phylogeny & Domain Bacteria

LECTURE PRESENTATIONS
For CAMPBELL BIOLOGY, NINTH EDITION
Jane B. Reece, Lisa A. Urry, Michael L. Cain, Steven A. Wasserman, Peter V. Minorsky, Robert B. Jackson
Phylogeny & Domain Bacteria
Lectures by
Erin Barley
Kathleen Fitzpatrick
© 2011 Pearson Education, Inc.
Taxonomy
• how organisms are named and classified
• Greek philosophers suggested that life
might have changed gradually over time
– but Aristotle – viewed species as fixed
and said that life-forms could be
arranged on a ladder of increasing
complexity = scalae naturae
Taxonomy
• Carolus Linneaus – developed the
binomial system for naming species
– binomial = two names
• developed a nested classification
system in contrast to Aristotle
– grouped animals according to
similar characteristics
– groups (taxa) known as phylum,
class, order, family, genus,
species
– thought the similarities were due
to God’s creation
Human being = Homo sapiens
-first word = Genus
-second word = species name
-both are usually italicized
Phylogeny vs. Taxonomy
• taxonomical classification not only takes the
morphological similarities of organisms into
account – it also looks at the evolutionary
relationships
• evolutionary history of a species or a group of
species = phylogeny
• phylogenies are constructed uses data ranging
from fossils to genetic analysis to derive
evolutionary relationships
– each branch point is a divergence of
two evolutionary lineages from a
common ancestor
Genus
Family
Panthera Mephitis
Lutra lutra Canis
Canis
pardus mephitis
(European familiaris
lupus
(leopard) (striped skunk) otter)
(domestic dog) (wolf)
Panthera
Felidae
Order
• classification using phylogeny
depends upon identifying common
ancestors
• physical and genetic similarities
due to shared ancestry = homology
• the relationship between common
ancestors and their descendants
can be shown as a phylogenetic
tree
• the common ancestor is the base of
a dichotomy or a two-way branch
point
Species
Phylogeny
Mephitis
Lutra
Mustelidae
Carnivora
Canis
Canidae
65.5
251
Mesozoic Cenozoic
Millions of
years ago
542
Paleozoic
Neoproterozoic
• common
ancestor of the
fish and the
human arose
542 MYA!!
• so there has
been 542
million years of
evolution for
both the fish
and the human
From Kingdoms to Domains
• earliest taxonomists just had two kingdoms: Plants and
Animals
• with the discovery of bacteria – things got a bit more
complicated
– bacteria were classified as plants since they were found to have
a cell wall
• since algae underwent photosynthesis – considered plants
also
• fungi also classified as plants – despite having nothing in
common with plants
• organisms that consumed were considered animals –
including single celled organisms like protozoans
• in 1969: five-kingdom classification system – Robert
Whittaker
– recognized the existence of two fundamental cell types:
prokaryotes and eukaryotes
– created a separate kingdom for prokaryotes and divided up
the eukaryotes
– 1. Monera - prokaryotic
– 2. Protista – unicellular organisms including algae
– 3. Fungi
– 4. Plantae
– 5. Animalia
– based on the nutritional requirements and methods of
these domains
• plants = autotrophs
• animals = heterotrophs & internal digestors
• fungus = decomposers & heterotrophs
• this classification scheme has
changed
– due to analysis of genes
0
• adoption of a three domain
system of superkingdoms
• contains the “old” kingdoms of
protists, fungi, plants and animals
• these kingdoms no longer exist
but are still kept by us stubborn
biologists!
1
Billion years ago
– 1. Bacteria – most of the
currently known prokaryotes
(or Eubacteria)
– 2. Archaea – prokaryotes that
inhabit a wide variety of
environments
– 3. Eukarya - eukaryotes
Bacteria
Eukarya
gene transfer
2
3
common ancestor
of all life
4
Origin of life
Archaea
Comparing Prokaryotic and Eukaryotic
Cells
• Prokaryotic cells:
– no nucleus
– DNA in a region of the
cytoplasm called the nucleoid
– no membrane-bound
organelles
– a Cytoplasm bound by the
plasma membrane
– smaller ribosomes
• Eukaryotic cells
– membrane – bound
nucleus containing DNA
– membrane-bound
organelles
– a Cytoplasm in the region
between the plasma
membrane and nucleus
– larger ribosomes
Prokaryotic Cells
• usually smaller and less complex than eukaryotic cells
• first cells to evolve
• single-celled organisms
– 0.5 to 5um in diameter (eukaryotes 10-100um)
– some species exist as aggregates called colonies
• e.g. cyanobacteria
• defined as having no nuclear membrane, no mitochondria or
other organelles
• divided into two domains:
– Bacteria
– Archaea
Domain Bacteria
• Bacteria:
– collective biomass – 10x of all
eukaryotes
– vast genetic diversity among
members
– physical diversity
• shapes: spheres (coccus), rods
(bacilli) and spirals
1 µm
Spherical
(cocci)
2 µm
Rod-shaped
(bacilli)
5 µm
Spiral
Bacteria
Fimbriae
Nucleoid
• made up of numerous components:
– cell capsule (slime layer) – for
adherence and protection
– cell wall
– plasma membrane – phospholipid
bilayer
– fimbrae – for attachment &
conjugation
– flagella(e) – for locomotion
– cytoplasm – for metabolism
– nucleoid region with a single
chromosome
– ribosomes – for protein synthesis
Ribosomes
Plasma
membrane
Bacterial
chromosome
Cell wall
Capsule
(a) A typical
rod-shaped
bacterium
Flagella
Prokaryotic Cells
• Bacterial cell components:
– cell wall – rigid structure outside
the plasma membrane
• cross-linked sugars
• for protection, structural support &
reproduction
• gram negative bacteria have an
additional layer of sugars and fats
outside the cell wall
• this layer is responsible for the toxicity
of these bacteria
Prokaryotic Cells
Fimbriae
Nucleoid
• Bacterial cell components:
– fimbrae – structures involved in
attachment
Ribosomes
Plasma
membrane
Bacterial
chromosome
• shorter ones involved in reproduction =
pilus
– flagella – made of protein
filaments
• for locomotion
– cytoplasm – intracellular fluid of
the prokaryote
• bounded by the plasma membrane
• cytosol + cytoskeleton
• no membrane-bound organelles
Cell wall
Capsule
(a) A typical
rod-shaped
bacterium
Flagella