Transcript File

Unit 2 : Diversity of Life
Classification - Concepts and
Principles
• Scientists have identified 1.5 million kinds of
living organisms. To deal with this huge number,
biologists classify the organisms according to an
established international system. This system
allows biologists to identify an organism and place
it in the correct group with related organisms.
• The branch of biology that deals with classification
and naming of living organisms is called
taxonomy.
Taxonomy
• naming and placing of all organisms into
groups.
• science of classifying organisms
Early Classification Schemes
• placed all organisms into one of two groups
Early Classification
Living Things
Plants
Animals
Classification by
Aristotle and Theophrastus
• Aristotle classified animals according to
where in the environment they lived.
• Theophratus classified plants according to
their stem structure
Aristotle's Classification
Animals
Air Dwellers
Land Dwellers
Water Dwellers
Theophrastus's Classification
Plants
Herbs
(soft stem)
Shrubs
Trees
(Several woddy stems) (single woody stem)
• The early schemes were based mainly on
structural similarities.
• In 1866 Ernst Haeckel added a third Kingdom Protista
• Was a dumping ground to help deal with
organisms that were neither animals or plants
• Ex. Euglena- had characteristics of both plant and
animals so placed in Protista
• As scientist learned more about structure and
function of different organism more kingdoms
were added.
• Kingdom Fungi was proposed. Organisms from
this kingdom were originally classified as plants,
but fungi are not photosynthetic and are
heterotrophic so they became a separate kingdom.
Robert Whittaker (1969)
• Proposed a 5 Kingdom classification system
base upon the following:
• A) n umber of cells
• B) presence or absence of a nucleus
• C) Mode of Nutrition
Today
•
•
•
•
•
•
•
•
6 Kingdom classification
Kingdom Animilia
Kingdom Plantae
Kingdom Fungi
Kingdom
Protista
Kingdom Bacteria or Monera
Kingdom Archaea
Three Domains( Largest
Classification Group)
• All six kingdoms are separated into 3 domains
• A) Domain bacteria-Kingdom bacteria or Monera
• B) Domain Archaea- Kingdom Archaebacteria or
Archaea
• C). Domain Eukarya-Kingdom Animalia, Plantae,
Protista, and Fungi
• Domain Eukarya originates from the word
Eukaryotic meaning having a nucleus
Classification Categories
• Within any Kingdom there are many levels
of classification.
Carl Linnaeus
• Linnaeus attempted to classify all known
species of his time (1753).
• Linnean hierarchical classification was
based on the premise that the species was
the smallest unit, and that each species (or
taxon) nested within a higher category
Classification Categories
 Kingdom
E.g. Humans
 Animalia
 Phylum
 Chordata
 Class
 Mammalia
 Order
 Primates
 Family
 Hominidae
 Genus
 Homo
 Species
 Homo sapiens
• Every single type of organism
belongs to one kingdom, one phylum,
one class, one order, one family, one
genus, and one species.
• Every Organism on earth is placed into each
of the classification categories
Humans
•
•
•
•
•
•
•
Kingdom Animalia
Phylum Chordata
Class Mammalia
Order Primates
Family Hominidae
Genus Homo
Species Sapien
Domestic Dog
•
•
•
•
•
•
•
Kingdom Animalia
Phylum Chordata
Class Mammalia
Order Carnivora
Family Canidae
Genus Canis
Species familaris
Wolf
•
•
•
•
•
•
•
•
K. Animalia
P. Chordata
SubP. Vertebrata**
C. Mammalia
O. Carnivora
F. Canidae
G. Canis
S. lupus (Latin for wolf)
Naming Organisms
• The system for naming things is called binomial
nomenclature. It consists of naming each species with
two names. The first is the genus name, the second is
the species name.
• This system was developed at a time when Latin was
the language of scholars, and therefore the names are
in Latin. Newly discovered organisms are still named
using the Latin language.
• Genus has first letter capitalized, species all lower case
• underlined or italicized
Examples
• Homo sapiens - Humans
• Canis familaris - dog
• The scientific name is used worldwide by
all scientists, regardless of the language
they speak.
• The present classification system consists
of 6 kingdoms .
• The 6 kingdom system of classification is
the best and most widely accepted system
in use today because of the following
reasons:
• 1. It is generally able to deal with the
discoveries of new life forms.
• 2. Its ability to cope with changing ideas
about those characteristics of greatest
importance in classifying organisms.
• 3. Able to account for the evolutionary and
biochemical relationships that have been
discovered among organisms.
Common Names
• organisms may also be given common
names.
Common names can cause
confusion
• StarFish - not a fish
• green pepper is also referred to as a bell
pepper, sweet pepper
• Common names also vary from language to
language
• Dog - perro - inu
• Cougar, Mountain Lion, Puma
Today’s Classification Schemes
• Taxonomy centers around evolutionary
relationships
Taxonomic Keys
• A taxonomic key is a guide or blueprint to
identifying organisms already classified by
taxonomists. Such keys move from general to
specific descriptions.
• The keys are dichotomous, consisting of a series
of paired statements that describe alternate
possible characteristics of the organism. These
paired statements usually deal with the presence
or absence of characteristics or structures that are
easily seen. As each pair of statements gets more
specific, a smaller grouping of organisms is
produced until the species is identified.
Sources of Evidence That We Use When
Classifying Organisms:
• 1. From fossils
• 2. From living things
1. Evidence from Fossils
• Fossils are one of the strongest sources of
evidence of evolution.
• Definition: A fossil is any remains or signs
of remains of an organism that lived in the
past.
• There are 4 major methods of fossil
foundation:
(A) Preservation of the actual organism. They are usually
preserved in a single substance. These include:
• (i) Ice - some animals are permanently frozen in ice (e.g.
Wooly Mammoth)
• (ii) Amber - amber is the resin (gum) from some trees.
The resin traps insects.
• (iii) Tar Pits - naturally occurring in warmer climates.
Animals fall into these pits and their skeletal remains are
solidified along with the tar before they can decompose.
(e.g. sabre toothed tiger)
• (iv) Volcanic Ash - during volcanoes a tremendous
amount of ash is produced. This ash covers over
organisms and acts as a preservative. (e.g. reptiles)
(B) Petrifaction
• The organism becomes covered in water
containing a high mineral content.
Gradually, the original substances of the
organism dissolve and are replaced by
minerals from the water. The remains of
the organism are turned into stone. (e.g.
petrified tree)
(C) Carbonization
• Carbonization is a process whereby large
carbon deposits of oil, coal and gas are
produced. It is the result of large groups of
organisms that are compacted together
before they can decay. In coal deposits it is
not uncommon to find the fossils of the
organisms that produced the coal fields.
(D) Molds and Casts
• Mold - sediment in which an organism is
embedded hardens, preserving the shape of
the organism after the remains decompose.
• Cast - a mold becomes filled with minerals
and then hardens, producing a copy of the
external features of an organism.
(E) Imprint
• An imprint is formed when an impression
made in mud by a living organism is
preserved when the mud is transformed into
rock.
TRANSITIONAL FOSSILS LINKING PAST AND
PRESENT
Basilosaurus (ancient whale
Dating Fossils
• It is important to know the age of fossils.
This is done in two major ways:
• (i) Relative Dating by Deposition of
Sediment
• (ii) Absolute Dating by Radioactive Dating
(i) Relative Dating by Deposition of Sediments
• Most fossils are formed in sedimentary rocks.
Examining layers of sedimentary rock gives the relative
age of fossils. The relative age is determined by a
fossil’s position in the sedimentary layers. The fossils in
the layers on the bottom are assumed to be the oldest, and
in the top layers are assumed to be the youngest; unless
the geology of the area suggests otherwise.
• Scientists have discovered it takes approximately 1000
years of sediment to produce 30 cm of rock. By knowing
the fossil’s depth, one can determine the relative age of
the fossil.
• Example: 150 cm deep means a relative age of 5000
years.
(ii) Absolute Dating by Radioactive Dating
• Radioactive dating of fossils or the rock in which it is
found gives an absolute age. This method is based on the
rate of radioactive decay in isotopes of particular elements.
Living organisms accumulate certain radioactive isotopes
when they are living. Once these organisms die, the
radioactive isotopes start to break down.
• The rate of the breakdown is called the half-life. This is
the time it requires to breakdown half of the originally
accumulated radioactive isotopes. Every isotope has a
unique half-life. When the half-life of an isotope is known
along with its proportion in a fossil-bearing rock, it is
possible to calculate the age of the sample.
Isotopes Used for Radioactive Dating
Isotope Pair Half-life
(yrs)
Carbon-14 to
5730
Useful
Range (yrs)
60 000
Uranium-235 to
Lead-207
700 million
Over 500 000
Potassium-40 to
Argon-40
1.25 million
Over 500 000
Nitrogen-14
2. Evidence from Living Things
• Living organisms provide us with evidence
that development patterns, body structures
and chemical processes show similarities
that suggest a common design among some
organisms. There are four branches of
science that provide evidence which support
the concept of evolution.
(A) Comparative Embryology
• An embryo is an organism that is in the
early stages of development. Scientists
compare the structures of the embryos of
different organisms. These comparisons of
the embryological development of different
species provide evidence of their
relationship. The closer the resemblance
between the embryos, the greater the
evolutionary relationships.
(B) Comparative Anatomy
• This is a science where the anatomy of
different organisms are compared for
similarities and differences. Certain types
of similarities indicate a common
evolutionary relationship. Scientists search
for homologous structures - structures that
are found in different organisms, yet are
similar in shape, structure and origin.
Example: hearts of the various classes of
vertebrates
• Scientists also look for vestiges or vestigial
organs. These are structures that have lost their
function, but were functional in an ancestor of the
organism.
• Example - the appendix of man
VESTIGIAL STRUCTURES
(C) Comparative Biochemistry
• Scientists compare the chemical composition of
different organisms. The presence of certain
types of similar chemicals indicates a common
evolutionary relationship. The closer the
similarities, the closer the relationship between
the organisms. They look at such things as the
sequence of amino acids in the protein of
organisms.
• Example - the structure of hemoglobin of the
monkey is closely related to the hemoglobin of
humans.
(D) Genetics
• Scientists have concluded that genes are
similar in organisms that are closely related.
The more similar the DNA structures
present, the closer the evolutionary
relationship.
SIX-Kingdom System of Classification
1. Monera (also called Kingdom Bacteria)
General Characteristics:

simple organisms lacking nuclei (prokaryotic)
 either autotrophic or heterotrophic
 all can reproduce asexually
 live nearly everywhere
Unicellular
May be photosynthetic, chemosynthetic or feed by absorption
Microscopic
Non motile and motile
Motility is accomplished by means of a flagellum
Found in 3 shapes
Round-cocci
Spiral-spirilli
Rod – Bacilli
Some are saprophytic-feed on dead substances or
parasitic feed on living organisms
Sample Organisms: bacteria, cyanobacteria
Bacteria
Kingdom PROTISTA
• Also called Archaebacteria
• These bacteria like organisms posses a
differing cell wall composition that allows
them to survive extreme conditions such as
salt lakes, or hot acidic springs
2. Protista
General Characteristics:
 most are single celled (unicellular); some are
simple multi-cellular organisms (eukaryotic)
 some are autotrophic, some are heterotrophic,
some are both
 reproduce sexually and asexually
 live in aquatic or moist habitats
Some are motile
• Slime molds and water molds fungus like
heterotrophs
• Sample Organisms: simple algae, protozoa,
Volvox, parmecium, amoeba
 Classified into 3 categories based on their nutrition
 Protozoa animal like hetrotrophs that ingest or absorb food
• Phylum Zoomastigina Have flagella
• Phylum Sacrodina have pseudopodia false foot
• Phylum Ciliophora have cilia
• Phylum Sporozoa reproduce by spores
Algae plant like protists that are autotrophs that
carry out photosynthesis
 Phylum Phaeophyta- brown algae
 Phylum Chrysophyta- Diatoms
 Phylum Pyrophyta Dinoflagellates
 Phylum Euglenophyta (euglenoids)
3. Fungi
General Characteristics:
 most are multicellular (eukaryotic), some are unicellular
 all are heterotrophs
 reproduce sexually and asexually
 most are terrestrial
Non motile
Saprophytic or parasitic
Made up of Hyphae/mycelium
Cell wall made of Chitin (skeletal)
Sample Organisms: mushrooms, yeast, bread molds
•
•
•
•
Phylum Zygomycota(Zygospores)
Phylum Basidomycota( basidospores)
Phylum Ascomycota ( asci
Phylum Deuteromycota( Conidia) Penicillin
4. Kingdom Archaea or Archebacteria
• Similar to bacteria
• Survive in extreme environments( volcanoes, hot springs,
ocean vents)
• Biochemically and genetically different from bacteria
• Has same shape as other bacteria
• Found in three types
• Methogens- producers of methane
• Halophiles-salt loving bacteria
• Thermophiles- heat loving bacteria
• Cell wall contains lipids
• Move by flagella or not at all
• Reproduce by means of binary fission or conjugation
4. Plantae
General Characteristics:
 all are multicellular (eukaryotic)
 all are autotrophs (photosynthetic)
 reproduce sexually and asexually
 most are terrestrial
Contain specialized cells and tissues
Non motile or sessile
Cell wall composed of Cellulose
Divided into two groups
Non flowering, flowering
Sample Organisms: seaweeds, mosses, ferns, conifers,
flowering plants
5. Animalia
General Characteristics:
 all are multicellular (eukaryotic) and heterotrophic
 most reproduce sexually(higher form), Lower forms
asexually
 live in terrestrial and aquatic habitats
Motile
Specialized cells and tissues
Divided into two groups
Invertebrates without a back bone
Vertebrates with backbone
Sample Organisms: sponges, “worms”, lobsters, starfish,
humans