Classification
I.
Taxonomy
Taxonomy is also known as systemic biology.
It is the study of classification of living things.
II.
Early Classification
2000 years ago, Aristotle classified organisms as plant or animal.
Those names were too long and a long series of descriptive terms.
There are 4 main reasons to classify organisms:
1. easier to study
2. organizes living things
3. explains the relationship between living things
4. it is universal
III.
Carolus Linnaeus (real name was Carl von Linne)
Father of modern Taxonomy
He developed two Kingdom system – Plantae and Animalia
He grouped organisms according to shared characteristics.
The group was called a Taxon (plural is Taxa).
He used Latin to name the taxa.
IV.
Modern System
Uses Binomial Nomenclature system to name organisms
Uses Latinized names
Genus and species names always written together
Ex Homo sapien or Homo sapien,, Canis lupus or Canis lupus
Species – organisms that can interbreed and produce fertile offspring.
Genus – group of closely related species
V.
Three Domain System
Domain Archaea (Kingdom Archaebacteria)
Domain Bacteria (Kingdom Eubacteria)
Domain Eukarya (protists, fungi, plants and animals)
VI.
Six Kingdom System
1. Kingdom Archeabacteria
 includes bacteria- like organisms that live in extreme conditions, such as very hot, very
cold or very salty (extremophiles)
 unicellular, prokaryotic - they have no nucleus
 mostly anaerobic – they don’t use oxygen
 chemosynthetic – uses inorganic substances as an energy source
 cell membranes contain unusual lipids
 cell walls lack peptidoglycan
2. Kingdom Eubacteria
 Unicellular, prokaryotes
 includes bacteria
 most are heterotrophic - cannot produce their own food
 also includes blue green algae, which are also called cyanobacteria and can produce
their own food (autotrophic)
 cells have thick, rigid cell walls, containing peptidoglycan
 live in very diverse ecological environments
3. Protista
 includes unicellular and multicellular organisms
 great variety of organisms within the kingdom
 includes Paramecium, Amoebas, protozoans are heterotrophic.
 The brown, yellow, red and green algae are autotrophic and use photosynthesis to
produce their own food.
4. Fungi
 Cell wall made of Chitin.
 Most are eukaryotic. Yeasts are unicellular.
 The mushrooms, molds and mildew are multicellular, heterotrophic and decomposers.
5. Plantae
 They are eukaryotic, multicellular and autotrophic (photosynthetic).
 This kingdom includes the mosses, ferns, shrubs, grasses, trees and flowers.
6. Animalia
 They are eukaryotic, multicellular and cannot produce their own food (heterotrophic).
 There are both invertebrates (no backbone) and vertebrates (with a backbone).
VII.
Basis for Classification
A. Structural similarities (main basis)
B. Chromosome structure (DNA)
C. Biochemical similarities
D. Embryological development
E.
Reproductive potential
F.
Evolutionary history
1. Uses cladistic analysis
2. Clade - group of ancestral species & all its descendants
3. Cladograms
a. shows evolutionary relationships among a group of organisms.
b. ancestors at node, length of branch = evolutionary time (extinct group short branch)
c. sister taxa – have common ancestor, and one taxa is not evolved from the other
d. uses derived characteristics (derived/inherited from a common ancestor means
acquired traits) - traits that arose in the most recent common ancestor of a particular
lineage and was passed along to its descendants.
e. helps scientists understand how one lineage branched from another during evolution
G.
Molecular Clocks
1. Uses DNA comparisons to estimate length of time that two species have been evolving
separately .
2.
3.
4.
5.
6.
More similar the DNA More recently they shared a common ancestor More Closely
related they are in evolutionary terms
Measures neutral mutations that have no effect on how an organism looks (phenotype).
These mutations accumulate in the DNA of different species at about the same rate.
Comparing DNA of two species can show how different the genes are, which helps tell how
long ago the two species shared a common ancestor.
Molecular clocks allow researchers to time different kinds of evolutionary events.
VIII. Earth’s early History
Earth is about 4.6 billion years old. Earth's early atmosphere probably contained hydrogen cyanide, carbon
dioxide, carbon monoxide, nitrogen, hydrogen sulfide, and water.
Earth’s early atmosphere contained little or no oxygen. Cyanobacteria, single-celled prokaryotic organisms
must have evolved in the absence of oxygen. They produced oxygen, as an end product of photosynthesis.
Hence concentrations of methane and hydrogen sulfide began to decrease, the ozone layer began to form.
The First Organic Molecules:
In the 1950s, Miller and Urey Simulated Earth's
Early Atmosphere in a laboratory setting.
By passing electric sparks through a mixture of
hydrogen, methane, ammonia, and water they
produced amino acids, which are needed to make
proteins, , and building blocks of DNA.
It suggested how mixtures of the organic compounds
necessary for life could have arisen from simpler
compounds present on a primitive Earth.
Q. Why did they use a mixture of hydrogen, methane,
ammonia, and water? Simulate atmosphere on early
earth
Q. Why did they used sterilized closed system? To
prevent O2 from entering and to avoid contamination
by bact.
Q.what was the purpose of electric sparks? To
stimulate lightning and to provide energy for the
chemical reactions
IX. Koch's Postulates - Germ Theory
Robert Koch applied the principles to establish the bacterial cause of tuberculosis and anthrax.
A plan of experimentation necessary to prove that a disease is caused by a specific infectious agent and to
isolate/identify the infectious agent.
1. Infectious agent must be present in
every case of the disease
2. Infectious agent must be extracted
from an diseased individual, isolated
from all other micro-organisms, and
grown independently in laboratory
culture
3. The cultured infectious agent, must
create the same disease when
introduced into a healthy test
individual of the same species
4. The supposed infectious agent must
be extracted from the test individual
and shown to be the same
microorganism