Download Chapter 17 Organizing Life`s Diversity

Chapter 17: Organizing
Life’s Diversity
Section
1:
The
History
of
Classification
Section 2: Modern Classification
Section 3: Domains and Kingdoms
17.1 The History of Classification


Main idea: Biologists use a system of
classification to organize information about the
diversity of living things.
Objectives:
Compare Aristotle’s and Linnaeus’s methods of
classifying organisms.
 Explain how to write a scientific name using
binomial nomenclature.
 Summarize the taxa in the biological classification

17.1 The History of Classification

Review Vocabulary


Morphology: the structure and form of an organism or one of its parts
New Vocabulary:












Classification
Taxonomy
Binomial nomenclature
Taxon
Genus
Family
Order
Class
Phylum
Division
Kingdom
Domain
Early Systems of Classification



Biologists find it easier to communicate and
retain information about organisms when the
organisms are organized into groups.
Classification is the grouping of objects or
organisms based on a set of criteria.
Biologists use a system of classification to
organize information about the diversity of
living things.
Aristotle’s System


More than 2000 years ago, Aristotle developed the first
widely accepted system of biological classification.
Aristotle classified organisms as either animals or
plants.



Animals were classified according to the presence or absence
of “red blood.”
Animals were further grouped according to their habitats and
morphology.
Plants were classified by average size and structure as trees,
shrubs, or herbs.
Aristotle’s System

System useful for organizing but it had
limitations.
It did not account for evolutionary relationships.
 Many organisms did not fit easily into Aristotle’s
system; such as birds that don’t fly or frogs that live
on both land and water.


Many centuries passed before Aristotle’s system
was replaced by a new system that was better
suited to the increased knowledge of the natural
world.
Linnaeus’s System




In the 18th century, Carolus Linnaeus broadened
Aristotle’s classification method and formalized it into a
scientific system.
Like Aristotle, he based his system on observational
studies of the morphology and the behavior of
organisms
Linnaeus’s system of classification was the first formal
system of taxonomy.
Taxonomy is a discipline of biology primarily
concerned with identifying, naming , and classifying
species based on natural relationships.


A branch of the larger branch of biology called systematics
Systematics is the study of biological diversity with an
emphasis on evolutionary history.
Linnaeus’s System




Linnaeus’s method of naming organisms, called
binomial nomenclature, gives each species a
scientific name with two parts.
The first part is the genus name, and the second
part is the specific epithet, or specific name, that
identifies the species.
Latin is the basis for binomial nomenclature.
Biologists use scientific names for species
because common names vary in their use.
Binomial Nomenclature

Common names that lead to confusion:
Woodchuck or Groundhog
 Starfish are not fish
 Great Horned Owls do not have horns.
 Sea Cucumbers are not plants


Scientific names eliminate confusion

Instead of a redbird, cardinal or Northern cardinal
having different names in different regions of the
US, Linnaeus gave this bird its scientific name:
Cardinalis cardinalis.
Rules of Scientific Names




The first letter of the genus name always is
capitalized, but the rest of the genus name and
all letters of the specific epithet are lowercase.
If a scientific name is written in a printed book
or magazine, it should be italicized.
When a scientific name is written by hand, both
parts of the name should be underlined.
After the scientific name has been written
completely, the genus name will be abbreviated
to the first letter in later appearances (e.g., C.
cardinalis).
Modern Classification Systems



Evolution added a new dimension to Linnaeus’s
classification system.
Organisms were no longer classified on the basis
of morphological and behavioral characteristics
alone.
Evolutionary relationships are included in
modern classification systems.
Taxonomic Categories

A nestedhierarchal
system-each
category is
contained
within another,
and they are
arranged from
broadest to
most specific.
Species and Genus



A named group of organisms is called a taxon
(plural, taxa).
A genus (plural, genera) is a group of species
that are closely related and share a common
ancestor.
Example
American black bear – Ursus americanus
 Asiatic black bear – Ursus thibetanus

Family


A family is the next higher taxon, consisting of
similar, related genera.
Example
All bears, both living and extinct species, belong to
the same family, Ursidae.
 All members of the bear family share certain
characteristics: they all walk flatfooted and have
forearms that can rotate to grasp prey closely.

Higher Taxa



An order contains related families (Carnivora).
A class contains related orders (Mammalia).
A phylum or division contains related classes.



The term division is used instead of phylum for the
classification of bacteria and plants.
The taxon of related phyla or divisions is a
kingdom.
The domain is the broadest of all the taxa and
contains one or more kingdoms.
Systematic Applications


Scientists who study classification provide
detailed guides that help people identify
organisms.
Many times a field guide will contain a
dichotomous key, which is a key based on a
series of choices between alternate
characteristics.
17.2 Modern Classification


Main idea: Classification systems have changed over time as
information has increased.
Objectives:




Review Vocabulary


Compare and contrast species concepts
Describe methods used to reveal phylogeny
Explain how a cladogram is constructed
Evolution: the historical development of a group of organisms
New Vocabulary





Phylogeny
Character
Molecular clock
Cladistics
cladogram
Determining Species

Typological species concept
Aristotle and Linnaeus thought of each species as a
distinctly different group of organisms based on
physical similarities.
 The definition of species is called the typological
species concept.
 Based on the idea that species are unchanging,
distinct, and natural types.

Biological Species Concept


The biological species concept defines a species as a
group of organisms that is able to interbreed and
produce fertile offspring in a natural setting.
Limitations:



Wolves and dogs, as well as many plant species, are known to
interbreed and produce fertile offspring even though they are
classified as different species.
Does not account for extinct species or species that
reproduce asexually
However, because the biological species concept works
in most everyday experiences of classification, it is used
often.
Phylogenic Species Concept


Phylogeny is the evolutionary history of a
species.
The phylogenic species concept defines a
species as a cluster of organisms that is distinct
from other clusters and shows evidence of a
pattern of ancestry and descent.
Species Concepts
Characters



To classify a species, scientists construct patterns
of descent by using characters.
Characters are inherited features that vary
among species.
Characters can be morphological or
biochemical.
Morphological Characters



Shared morphological characters suggest that
species are related closely and evolved from a
recent common ancestor.
Analogous characters are those that have the
same function but different underlying
construction. These characters do not indicate a
close evolutionary relationship.
Homologous characters might perform different
functions, but show an anatomical similarity
inherited from a common ancestor.
Birds & Dinosaurs

Dinosaur fossils show that they share many
features in common with birds.
Hallow bones
 Theropods have leg, wrist, hip, and shoulder
structures similar to birds.
 Some theropods may have had feathers


The evidence provided by these morphological
characters indicates that modern birds are
related more closely to theropod dinosaurs than
they are to other reptiles.
Biochemical Characters



Scientists use biochemical characters, such as
amino acids and nucleotides, to help them
determine evolutionary relationships among
species.
DNA and RNA analyses are powerful tools for
reconstructing phylogenies.
The similar appearance of chromosomes among
chimpanzees, gorillas, and orangutans suggests a
shared ancestry.
Biochemical Characters
Biochemical Characters

Scientists use a variety of techniques to compare DNA
sequences when assessing evolutionary relationships.




Sequencing and compare whole genomes of different
organisms
Compare genome maps using restriction enzymes
DNA-DNA hybridization during which single strands of
DNA from different species are melted together
Comparing the DNA sequences of different species is
an objective, quantitative way to measure evolutionary
relationships.
Molecular Clocks



Scientists use molecular clocks to
compare the DNA sequences or
amino acid sequences of genes
that are shared by different
species.
The differences between the
genes indicate the presence of
mutations.
The more mutations that have
accumulated, the more time that
has passed since divergence.
The Rate of Mutation

The rate of mutation is affected by many factors:





Type of mutation
Where the mutation is in the genome
Type of protein that the mutation affects
Population in which the mutation occurs
Molecular clocks can be valuable tools for determining
a relative time of divergence of a species. They are
especially useful when used in conjunction with other
data, such as the fossil record.
Phylogenetic Reconstruction



Cladistics is a method that classifies organisms
according to the order that they diverge from a
common ancestor.
Cladistics reconstructs phylogenies based on shared
characters.
Scientists consider two main types of characters when
doing cladistic analysis.


An ancestral character is found within the entire line of
descent of a group of organisms. (Birds & mammals –
backbone).
Derived characters are present members of one group of the
line but not in the common ancestor. (Birds & mammals –
feathers & hair).
Cladograms





Systematics use shared derived characters to
make a cladogram.
A cladogram is a branching diagram that
represents the proposed phylogeny or
evolutionary history of a species or group.
A cladogram’s branches indicate phylogeny.
The groups used in cladograms are called clades.
A clade is one branch of the cladogram.
Cladograms

The greater
the number of
derived
characters
shared by
groups, the
more recently
the groups
share a
common
ancestor.
17.3 Domains and Kingdoms


Main idea: The most widely used biological classification system
has six kingdoms within three domains.
Objectives:




Review Vocabulary


Compare major characteristics of the three domains
Differentiate among the six kingdoms
Classify organisms to the kingdom level
Eukaryote: an organism composed of one or more cells containing a
nucleus and membrane-bound organelles
New Vocabulary




Eubaceria
Archaea
Protist
Fungus
Grouping Species

The broadest category in the classification used by most
biologists is the domain.



The most widely used biological classification system
has six kingdoms and three domains.



The three domains are Bacteria, Archaea, and Eukarya.
Organisms are classified in domains according to cell type
and structure.
The six kingdoms are Bacteria, Archaea, Protists, Fungi,
Plantae, and Animalia.
Organisms are classified into kingdoms according to cell type,
structure, and nutrition.
Archaea are the only members of their own domain.

Archaebacteria are unicellular prokaryotes
Domain Bacteria





Eubacteria, members of Domain Bacteria and
Kingdom Eubacteria are prokaryotes whose cell walls
contain peptidoglycan.
Peptidoglycan is a polymer that contains two kinds of
sugars that alternate in the chain.
Eubacteria are a diverse group that can survive in many
different environments.
Aerobic (need oxygen) or anaerobic (die in oxygen).
Autotrophic (produce their own food) or heterotrophic
(get nutrition from other organisms).
Domain Bacteria
Domain Archaea




Archaea are thought to be more ancient than
bacteria and yet more closely related to our
eukaryote ancestors.
Their cell walls do not contain peptidoglycan.
Archaea are diverse in shape and nutrition
requirements.
They are called extremophiles because they can
live in extreme environments.
Domain Eukarya


All eukaryotes (cells with membrane-bound
nucleus and other membrane-bound organelles)
are classified in Domain Eukarya.
Domain Eukarya contains Kingdom Protista,
Kingdom Fungi, Kingdom Plantae, and
Kingdom Animalia.
Kingdom Protista


Protists are eukaryotic organisms that can be
unicellular, colonial, or multicellular.
Protists are classified into three different
groups—plantlike, animal-like, and funguslike.
Plantlike are called algea; autotrophs that perform
photosynthesis
 Animal-lke are called protozoans; heterotrophs
 Funguslike are slime molds and mildews
 Euglenoids are a type of protist that have plantlike
and animal-like characteristics; usually grouped with
plantlike because they have chloroplasts and can
perform photosynthesis.

Kingdom Protista
Kingdom Fungi





A fungus is a unicellular or multicellular eukaryote that
absorbs nutrients from organic materials in its
environment.
Member of Kingdom Fungi are heterotrophic, lack
mobility, and have cell walls.
Their cell walls contain a substance called chitin, which
is a rigid polymer that provides structural support.
A fungus consists of a mass of threadlike filaments
called hyphae.
Hyphae are responsible for the fungus’s growth,
feeding, and reproduction.
Kingdom Fungi



Mushrooms are
heterotrophic
organisms.
Some fungi are
parasites - grow and
feed on other
organisms and
others are saprobes –
get their
nourishment from
dead or decay
organic matter.
Fungi that live in a
mutualistic
relationship with
algae are called
lichens.
Kingdom Plantae





Members of Kingdom Plantae form the base of all
terrestrial habitats.
All plants are multicellular and have cell walls
composed of cellulose.
Most plants are autotrophs, but some are heterotrophic.
Plants possess cells that are organized into tissues, and
many plants also possess organs such as roots, stems,
and leaves.
Plants lack mobility, yet some plants have reproductive
cells with flagella that propel them through the water.
Kingdom Plantae
Kingdom Animalia







All animals are heterotrophic, multicellular eukaryotes.
Animal cells do not have cell walls.
Animal cells are organized into tissue, and most tissues
are organized into organs.
Animal organs often are organized into complex organ
systems.
Animals range in size.
They live in the water, on land, and in the air.
Most animals are motile, although some, such as coral,
lack motility as adults.
Kingdom Animalia
Viruses - An Exception



A virus is a nucleic acid surrounded by a protein
coat.
Viruses do not possess cells, nor are they cells,
and are not considered to be living.
Because they are nonliving, they usually are not
placed in the biological classification system.