Transcript of Chapter 17 Main Ideas

Classification of
Organisms
Chapter 17
Modern Biology c2009
http://en.wikipedia.org/wiki/Pangolin
1
Classification
• Estimates range from 10 million (to as
many as 50 million) species living presently
on our planet (only a small fraction of the
number that have ever existed in the earth's
history) but only around 10% have been
classified
• 1,000’s of new species found every year
2
Taxonomy
• Taxonomy is the biological branch of
classifying or grouping organisms; based on
their presumed natural relationship
• a "Taxon" ( taxa - plural) is a category into
which related organisms are placed
• Use characteristics of new species
compared to similar organisms
characteristics
• The way organisms are grouped changes as
new information comes in
3
So why classify?
• organization for study purposes
• common names may be misleading (ex:
starfish, jellyfish, prairie dog, groundhog,
ringworm, etc)
• scientists need a universal naming system
(like metrics)
• shows relationships between organisms
(evolutionary path)
• Latin = the universal language of science
4
Early Systems of Classification
• One of the earliest taxonomic systems
was setup by Aristotle around 350 BC,
based on his limited observations of
organisms.
• In his Scala Naturae ("ladder of life"), he
divided creatures up into 2 groups
(plants/animals).
• He further classified animals based on
an "either/or" system (blooded -vsbloodless) and their means of
transportation (air, land, or water).
• Plants were subdivided based on
woody-stemmed or soft-stemmed.
5
The Linnaean System
• Carolus Linnaeus: (Karl von Linne)18th
century Swedish naturalist; devised system
of grouping organisms into hierarchical
categories
• Based mostly on form & structure
• Originally used 7 levels of organization:
–
–
–
–
–
–
–
Kingdom: plant & animals
Phylum (animals); Division (plants)
Class
Order
Family
Genus
species
6
Taxonomy
Common Name: Cat, Domestic Shorthair and Longhair
Kingdom: Animalia
Phylum: Chordata
Class: Mammalia
Order: Carnivora
Family: Felidae
Genus: Felis
Species: catus
• Today, every living thing has a universal SCIENTIFIC
NAME, known as BINOMIAL NOMENCLATURE (2part name) of Genus & species, which is unique to every
living organism. see examples:
Drosophila melanogaster
Thamnophis melanogaster
Quercus rubrum
Quercus alba
Acer rubrum
7
"Making Order out of Chaos"
SUMMARY:
• Species names are Latinized; useful to
scientists around the world
• This naming system not only helps to group
things into manageable study categories, it
can help to differentiate degree of
relationship between organisms.
– Phylogeny: evolutionary history of species or
taxonomic group
8
Taxon
Red Maple
White Pine
Green Alga Mountain Lion Domestic Dog Grey Wolf
Human
KINGDOM
Plantae
Plantae
Protista
Animalia
Animalia
Animalia
Animalia
PHYLUM
Anthophyta
Coniferophyta
Chlorophyta
Chordata
Chordata
Chordata
Chordata
CLASS
Dicotyledones
Coniferopsida
Chlorophycea
e
Mammalia
Mammalia
Mammalia Mammalia
ORDER
Sapindales
Coniferales
Ulvales
Carnivora
Carnivora
Carnivora
Primates
FAMILY
Aceraceae
Pinaceae
Ulvaceae
Felidae
Canidae
Canidae
Hominidae
GENUS
Acer
Pinus
Enteromorpha
Felis
Canis
Canis
Homo
SPECIES
rubrum
strobus
compressa
concolor
familiaris
lupus
sapiens
9
The Linnaean System
• WITHIN a species, there may also be BREEDS,
RACES, or VARIETIES that show distinctive
phenotypes.
• We can also divide the Linnaean categories even
further, if needed: subspecies, superclass,
subphylum, etc.
10
And new things are being
discovered all the time!
• Hairy lobster!
...named Kiwa hirsuto "The team that
found the crustacean said that while legions of new ocean
species are discovered each year, it is quite rare to find one
that merits a new family.”
• “The family was named Kiwaida, from Kiwa, the goddess
of crustaceans in Polynesian mythology. “
(from BBC news story, 2006)
What goes into naming a
species? (6 minute audio)
11
Six-Kingdom System
• Although Aristotle classified organisms as
either plants/animals, we now recognize
many forms of life are neither.
• Originally 5 kingdoms, but studies showed
two important subtypes of bacteria
• Archaebacteria, Eubacteria (Prokaryotic)
• Protista, Fungi, Plantae, Animalia
(Eukaryotic)
12
Archaebacteria
• Unicellular prokaryotes
• Distinct cell membranes, cell walls, and rRNA
• Most species are autotrophic; use
chemosynthesis (methane waste product), but
a few are heterotrophic
• “Extremophiles”, live in harsh conditions (ex:
hot springs)
• Archae- “ancient”; similar to first
chemotrophic prokaryotes on earth
13
Eubacteria
• Eu- “true” bacteria
• Unicellular prokaryotes
• Some species are heterotrophic, others are
autotrophic (photosynthetic or chemosynthetic)
• Responsible for tooth decay, turn milk into yogurt,
& food poisoning, important as decomposers
• Most species use oxygen; few cannot live in presence
of oxygen
• Eubacteria & Archaebacteria greatest # of living
things on Earth
14
Eubacteria
• Asexual binary fission but can recombine
genes in some ways (conjugation)
• Rapid response to evolutionary change
(mutate) because of short generation
times
15
Protista
• A wide variety of eukaryotic, mostly
single-celled organisms
– Membrane-bound nucleus & complex
organelles, linear chromosomes
• Euglena & amoebas common unicellular
protists
• Seaweed, kelp are examples of species of
multicellular protists (but lack specialized
tissues, unlike plants)
16
Protista
• Euglena
– Feed on other organisms
– Chloroplasts & photosynthesis
– Not a plant
• Amoebas
– Feed on other organisms
– Respond to touch & light
– Not an animal
17
Fungi
•
•
•
•
Heterotrophic, made up of eukaryotic cells
Absorbs nutrients from decaying matter
Cell walls made of chitin
Most are Multicellular: mushrooms, puffballs,
rusts, smuts, mildews, mold
• A few species are unicellular: Yeasts
18
Plantae
• Multicellular, eukaryotic
• Autotrophic; a few are also parasitic or
carnivorous
• Use photosynthesis as source of energy
• Sexual cycle based on meiosis
• Mosses, ferns, conifers, and flowering
plants
19
Animalia
• Eukaryotic cells, multicellular,
heterotrophic
• Symmetrical body organization
• Move about environment
• Standard sexual cycle, meiosis for
recombination of genes
20
Three-Domain System
• Carl Woese: compared sequences of
ribosomal RNA in different organisms,
estimated how long ago pairs of different
organisms shared a common ancestor
• All organisms have ribosomal RNA
• Domain: one of three broad groups that
all living things fall into on basis of rRNA
analysis
21
Three-Domain System
• Archae
– Kingdom
Archaebacteria
• Bacteria
– Kingdom Eubacteria
• Eukarya
– Kingdoms Protists,
Fungi, Plants, Animals
22
Modern Phylogenetic Taxonomy
• Taxonomists today consider morphology
(like Linnaeus did), but also use
chromosomal characteristics, nucleotide
and amino acid sequences, embryological
development
• With consideration of all of this evidence
and fossil record, yield reliable info about
phylogeny of an organism.
23
Systematics
• Systematics: organizes tremendous diversity of
living things in the context of evolution
• Classification of organism should reflect their
phylogeny
• Hypothesis based on several lines of evidence
24
Systematics
• Phylogenetic tree: family tree that shows
evolutionary relationships thought to exist
among groups of organisms
25
Systematics
• The greater # of homologous
morphological features two organisms
share, more closely related they are
thought to be.
• Early patterns in embryological
development provide evidence of
phylogenetic relationships.
• Differences in animal phyla may appear
early.
• Blastula: ball of embryonic cells
26
Tree of Life
27
Systematics
• Blastopore an indentation, develops on
outside of blastula
• Anterior/Posterior end of digestive
system; Chordates and Echinoderms
• Echinoderms: radially symmetrical marine
invertebrate with an endoskeleton; watervascular system, tube feet (starfish, sea
urchin)
28
Systematics
• Both share important characteristics like
each cell of early embryo is capable of
forming entire organism; Twins, Fruit fly
parts
• Molecular clock
• Chromosome bands
• Chimpanzee/Humans common ancestor
– 25 mya to 5 mya using karyotype and amino
acid sequences in proteins
29
Cladistics
• Cladistics: system of phylogenetic
classification using shared derived
characters to establish evolutionary
relationships
• Derived Character: feature that apparently
evolved only within the group under
consideration
– Birds; feathers (only animals to have feathers)
30
Cladistics
• Feathers evolved in bird group & not
inherited from distant ancestor of birds
• Shared derived characters, particularly a
group of several; evidence of common
ancestry between organisms that share
them
• Cladogram
31
Cladistics
• One of most notable nontraditional
conclusion shows crocodiles, birds, and
dinosaurs are more closely related to each
other than any one of them is to a snake
or lizard
• Reptiles did not all spring from one
common ancestor
• Composite of several branches that have
occurred during evolution of vertebrates
32