Transcript Lesson 2. Phylogeny, Kingdoms and Domains - Blyth

Phylogeny and Modern Taxonomy
and
Kingdoms and Domains
UNIT 1. Lesson 2.
Wednesday February 29, 2012
What is special about today?
• It only happens every 4 years
Learning Goals:
• Explain the principles of taxonomy and
phylogeny and the concepts of taxanomic
rank
• Describe and compare traditional and
modern biological classification systems
Phylogeny
and
Modern Taxonomy
Copy all red
coloured text.
Recall:
•
Taxonomy
- the classification,
identification and naming of
organisms
- aims to group organisms
according to a set of criteria
(ex. how closely related they
are to each other)
- Classifying a species by
kingdom, phylum, and so on,
is like placing students in a
large school system. First a
student might be identified
by school, then by specific
grade, and finally as a
unique individual by name.
The leopard shares many characteristics
with the lion—which belongs to the same
genus—but far fewer characteristics with
snails, sponges, or earthworms, though
they are all members of the animal
kingdom.
The Theory of Evolution
• All living things are descended from a
common ancestor in the same way that
family members are related to each other
through a common ancestor.
THEREFORE we have a different type of taxonomy:
Phylogenetics – reconstructing the
evolutionary relationships among organisms
What is this study called?……………….
• Phylogeny
(“evolutionary tree”)
- the study of the evolutionary
relatedness between, and
among, species (entire
populations of individuals)
- these relationships are similar
to a large family tree, but
instead of tracing relationships
between family members,
phylogeny tracks relationships
between entire species
These relationships can be
presented in a:
• Phylogenetic tree
- a branching diagram used to show
evolutionary relationships between different
species or groups
- hypothesized genealogy traced back to the last
common ancestor (i.e., the most recent) through
hierarchical, dichotomous branching
•
Cladistics
- the principles that guide the production of phylogenetic
trees, a.k.a., cladograms
How to read a phylogenetic tree:
Present
Most recent
common ancestor
species to B & C
Nodes –
branch point,
speciation event
Past
Most recent
common ancestor
species to A, B & C
• Clade
- a taxonomic group that includes a single common
ancestor and all its descendents
- each evolutionary branch in a phylogenetic tree
- Example: 2 clades exist in this tree
Leopards and house cats compose a branch of
two species that share a common ancestor. A
larger branch that also includes wolves has a
common ancestor that would have lived longer
ago than the ancestor of leopards and house
cats.
Small clades – small number
of species that share a very
recent common ancestor
Large clades – includes all
species that share a common
distant ancestor
Common ancestor species
Other Examples:
Each shaded area in the
phylogenetic tree highlights
one clade, such as the yellow
area including species B
through H.
This cladogram shows how derived
characters can be used to identify clades
among certain vertebrates (animals with
backbones). All the species shown here
share a common ancestor that had a
backbone. (Each clade is actually defined
by several derived characters, not just
one.)
How
Cladograms
are made:
Other
examples:
Questions:
1. How many clades are
represented in this tree?
2. Which derived
characteristic is located
the “furthest back in
time”?
3. Which derived
characteristic links the
cat and salmon?
REVIEW
2 types of taxonomy:
1) Traditional classification (taxonomic tradition)
- hiearchial classification system by Linnaeus
- groups species primarily by observed
morphological (physical) characteristics
2) Phylogenetic analyses (cladistic hypotheses)
- “modern taxonomy”
- organisms are grouped based on evolutionary
relatedness/pathways (not taxonomic ranks)
Note: Taxonomic groups often reflect true clades,
so both methods are valid.
In a phylogenetic tree, each branch point represents a common
ancestor of the species above that point. In this diagram, the
branches are labeled to reinforce how taxonomy reflects the
branching pattern of evolution.
Your Turn:
1) Fill out Kingdoms worksheet
2) Read and summarize “The
International Barcode of Life Project”
on page 36 of your text
Kingdoms and Domains
HOW DO WE ORGANIZE LIVING
THINGS?
• We name all organisms using many names:
– K ingdom
King
s
p
– P hylum
Phillip
e
– C lass
Cried
c
i
– O rder
Out
f
i
– F amily
“For
c
– G enus
Goodness
– S pecies
Sakes!”
– Come up with your own
memory trick!
• Each level is called a “taxon”
SIX KINGDOMS
•
•
•
•
Unicellular  single-cell
Multicellular  many cells
Prokaryotic  no nucleus present in cells
Eukaryotic  nucleus present in cells
• Each kingdom has
many phyla
– Each phylum has
many classes
• Each class has many
orders
– Etc.
"From the first growth of the tree, many a limb and branch has
decayed and dropped off; and these fallen branches of various sizes
may represent those whole orders, families, and genera which have
now no living representatives, and which are known to us only in a
fossil state. As we here and there see a thin, straggling branch
springing from a fork low down in a tree, and which by
some chance has been favoured and is still alive on its summit, so we
occasionally see an animal like the Ornithorhynchus (Platypus) or
Lepidosiren (South American lungfish), which in some small degree
connects by its affinities two large branches of life, and which has
apparently been saved from fatal competition by having inhabited a
protected station. As buds give rise by growth to fresh buds, and
these, if vigorous, branch out and overtop on all sides many a feebler
branch, so by generation I believe it has been with the great Tree of
Life, which fills with its dead and broken branches the crust of the
earth, and covers the surface with its ever-branching and beautiful
ramifications."
—Charles Darwin, On the Origin of Species
Apparently, the primordial
cell was a Pac Man
ghost???
http://www.dhushara.com/book/
unraveltree/evolutiontree.jpg
Domains of Life
Eubacteria
Archaea
Protista
Plants
Animals
Fungi
RECAP: TAXONOMY KEY
WORDS
•
•
•
•
•
•
•
•
•
•
Kingdom, Phylum, Class, Order, Family, Genus, Species
Taxon (plural: taxa)
Unicellular, multicellular
Prokaryotic, eukaryotic
Taxonomy
Binomial nomenclature
Cladogram
Phylogeny / phylogenetic
Homology / homologies / homologous
Dichotomous key
Your Turn
• Read Birds – In a Class of Their Own.
Answer questions 1-2
•
•
•
•
HOMEWORK:
Pg 23, Q 3,6,7
Pg 30, Q 1,3,5,9
Pg 37, Q 2,6