classification of living things - mrs. parker's...
TRANSCRIPT
CLASSIFICATION
OF LIVING
THINGS
Chapter 18
How many species are there?
About 1.8 million species have
been given scientific names
Nearly 2/3 of which are insects
99% of all known animal
species are smaller than
bumble bees
99% of all species that have
ever existed are now extinct
Taxonomy
Classification – the grouping of objects based on similarities
Taxonomy – the science of describing, naming, and
classifying organisms
Organisms are grouped into taxa (plural) or a taxon.
Each category is a taxon.
Freshmen (Class of 2016)
Sophomore (Class of 2015)
Junior (Class of 2014)
Senior (Class of 2013)
History of Classification
Aristotle (384 – 322 BCE) –
developed the first classification
system
Based on easily observable
characteristics
All organisms were classified as
plants or animals.
Plants – herbs, shrubs, and trees
Animals – things that swim, things
that fly, or things that walk.
Carl Linnaeus (1701 – 1778)
Wrote a book Systema Naturae in
1735 that outlined his classification
and naming system
Classification hierarchy (groups within
groups)
Binomial nomenclature
Organisms are grouped based on
similarities in their form and
structure at different levels
Levels of the Modern Linnaean System
DOMAIN
KINGDOM
PHYLUM
CLASS
ORDER
FAMILY
GENUS
SPECIES
Gets
more
specific
as you
move
down.
And,
organisms
are more
closely
related.
Binomial Nomenclature
Binomial Nomenclature – a two-word naming system using the
genus and species names
No two species can have the same scientific name
Both names are in Latin
Both names are italicized (underlined if handwritten)
The genus name is capitalized and the species name is lowercase
The species name is an identifier or descriptor
EXAMPLE – Apis mellifera
mellifera honey
Try these…
Canis lupis
Canis familiaris
Try these…
Felis domesticus Sus domesticus
How are living things classified?
Traditionally, organisms
were classified based
physical characteristics
(what could be seen).
Mammals – have hair,
produce milk and provide
care for young, and most
have live birth
Problems with the Old Way
Some organisms have similar features but are not closely
related
Example – Birds, bats, and bugs all have wings that are used to
fly but each evolved separately.
Problems with the Old Way
Some organisms look different but are closely related
Birds are dinosaurs (reptiles)
The Missing Link… (or at least one of them)
Archaeopteryx
Modern Classification
Based on phylogeny
Phylogeny – the ancestral/evolutionary relationships
among species
Each species has a family tree that includes many
ancestors and descendents and thousands of
generations.
Phylogenetic tree
How is phylogeny determined?
Phylogenetics uses the
presence or absence of traits
to determine relatedness
Morphology – studying the
physical structure or
anatomy of organisms
Very traditional but useful
for living species and
fossils
Homologous, Analogous, or Vestigial
Homologous structures – traits inherited from a common ancestor
May or may not have the same function or the exact same
appearance
Example: forelimbs of tetrapods
Homologous, Analogous, or Vestigial
Analogous structures – structures with common functions
Example – Birds, bats, and bugs all have wings that are used to fly
but each evolved separately.
Homologous, Analogous, or Vestigial
Vestigial Structures – evolutionary
leftover
Example – the human appendix has
no apparent function while rats and
other rodents have an appendix
that aids in digestion
Example – whales and snakes have
a pelvis and femur
How is phylogeny determined?
Biochemical – comparing DNA,
RNA, and protein sequences.
Genes pass from generation to
generation; therefore, all
descendents will have the similar
DNA
The more similar the DNA or
protein sequence the more
closely related the species
Levels of the Modern Linnaean System
DOMAIN
KINGDOM
PHYLUM
CLASS
ORDER
FAMILY
GENUS
SPECIES
Gets
more
specific
as you
move
down.
And,
organisms
are more
closely
related.
Cladistics
Cladisitics – a method of analysis
that infers phylogenies by careful
comparisons of shared traits.
Used to select the most likely
phylogeny among a given set of
organisms.
Comparing traits
Shared traits are defined as ancestral
Derived traits evolve in one group but
not another
Constructing a Cladogram
Cladogram – a phylogenetic
tree that is drawn in a specific
way to show evolutionary
relationships
Clade – all groups that
originate from a certain point
and have one common ancestor
Outgroup – a group that lacks
some of the shared characters
Clade
New species…
Scientists are discovering new species all the time.
So…we have to know where to classify them and how to
name them.
http://blogs.discovermagazine.com/loom/2010/06/30/what-if-anything-is-big-bird/
Constructing a Cladogram
Characters in Vertebrates
Four legs Backbone Amniotic egg Hair
Lizard yes yes yes No
Tuna no yes no No
Frog yes yes no No
Cat yes yes yes Yes
Interpreting Cladograms
Cladogram Questions
After which animals did mammary glands develop?
What animals do not have jaws?
Which animals share the trait for lungs?
Which animals have derived traits that protect them from the elements (weather)?
Why is the trait for feathers marked on the line for pigeons not the main line?
Which animals are probably predators?