Download Unit 6: Classification and Diversity

Unit 6: Classification and Diversity
KEY CONCEPT
Species are classified into a hierarchical taxonomic system (Kingdom,
Phylum, Class, Order, Family, Genus, and Species) based on
Morphological, Behavioral, and Molecular similarities.
Changes in the genetic make-up of populations may affect biodiversity
through speciation and extinction.
Unit 6: Classification and Diversity
Linnaeus developed the scientific naming system still in
use today.
Taxonomy is the science of naming and classifying
organisms.
Binomial nomenclature is a two-part scientific naming system.
Scientific names are often based on Latin and Greek names.
Tyto = Genus name
alba = epithet (identifies the specific
species)
Tyto alba is the species name
Unit 6: Classification and Diversity
When writing a scientific name, scientists use these rules:
 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 (Puma concolor)
 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).
Unit 6: Classification and Diversity
Scientific names help scientists to communicate and share
a common language.
Common names, unlike scientific names, are often very
confusing and the same organism can have more than
one common name.
Unit 6: Classification and Diversity
Linnaeus’ classification system has seven levels.
• Each level is nested
in the level above it.
• Levels get increasingly
specific from kingdom
down to species.
• A taxon is a group of
organisms in a
classification system.
• The major drawback to
this system is that it is
based on morphological
characteristics.
Unit 6: Classification and Diversity
Species and Genus
 A named group of organisms is called a taxa.
 A genus (plural, genera) is a group of
species that are closely related and share a
common ancestor.
Family
 A family is the next higher taxon, consisting
of similar, related genera.
Unit 6: Classification and Diversity
Higher Taxa
 An order contains related families.
 A class contains related orders.
 A phylum or division contains related classes.
 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.
Unit 6: Classification and Diversity
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.
Characters
 To classify a species, scientists construct patterns
of descent by using characters.
 Characters can be morphological or biochemical.
Unit 6: Classification and Diversity
Morphological Characters
 Shared morphological characters suggest that
species are related closely and evolved from a
recent common ancestor.
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.
Unit 6: Classification and Diversity
 The similar appearance of chromosomes
among
chimpanzees,
gorillas, and
orangutans
suggests a
shared
ancestry.
Unit 6: Classification and Diversity
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.
Unit 6: Classification and Diversity
• Scientists estimate mutation rates by linking molecular data
and real time.
– an event known to separate species
– the first appearance of a species in fossil record
Unit 6: Classification and Diversity
Mitochondrial DNA is used to study closely related species.
• Mutation rate ten times faster than nuclear DNA
• Passed down un-shuffled from mother to offspring
grandparents
mitochondrial
DNA
nuclear DNA
parents
Mitochondrial DNA is
passed down only from
the mother of each
generation,so it is not
subject to recombination.
child
Nuclear DNA is inherited from both
parents, making it more difficult to
trace back through generations.
Unit 6: Classification and Diversity
Phylogenetic Reconstruction
 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.
 Derived characters are present members of one
group of the line but not in the common ancestor.
Unit 6: Classification and Diversity
Cladograms
 The greater the
number of derived
characters shared
by groups, the
more recently the
groups share a
common ancestor.
Unit 6: Classification and Diversity
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.
 The six kingdoms are Bacteria, Archaea,
Protists, Fungi, Plantae, and Animalia.
Unit 6: Classification and Diversity
Unit 6: Classification and Diversity
Domain Bacteria
 Eubacteria are prokaryotes whose cell walls
contain peptidoglycan.
 Eubacteria are a diverse group that can survive
in many different environments.
Domain Archaea
 Archaea are thought to be more ancient than
bacteria and yet more closely related to our
eukaryote ancestors.
 Archaea are diverse in shape and nutrition
requirements.
 They are called extremophiles because they can live
in extreme environments.
Unit 6: Classification and Diversity
Domain Eukarya
 All eukaryotes are classified in Domain
Eukarya.
 Domain Eukarya contains Kingdom
Protista, Kingdom Fungi, Kingdom Plantae,
and Kingdom Animalia.
Unit 6: Classification and Diversity
Kingdom Protista
 Protists are a diverse group of eukaryotic
organisms that can be unicellular, colonial,
or multicellular. Tend to be hard to classify.
 Protists are
classified into three
different groups—
plantlike, animallike, and funguslike.
Unit 6: Classification and Diversity
Kingdom Fungi
 A fungus is a unicellular or multicellular eukaryote
that absorbs nutrients from organic materials in the
environment.
 Members of the kingdom, fungi have cell walls
made up of chitin, are heterotrophic and tend to
lack motility.
Unit 6: Classification and Diversity
Kingdom Plantae
 Members of Kingdom Plantae form the base of all
terrestrial habitats.
 Plants are multicellular autotrophs that have cell
walls composed of cellulose.
Unit 6: Classification and Diversity
Kingdom Animalia
 All animals are heterotrophic, multicellular
eukaryotes.
 Animal organs often are
organized into complex
organ systems.
Unit 6: Classification and Diversity
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.