Download Diversity of Living Things

Classification of Living Things
Taxonomy, Hierarchical Classification,
Binomial Nomenclature, Genetic
Variation, Relatedness, Phylogeny
Kingdoms
Classification – we all do it
 Main classification by Aristotle

• Plantae and Animalia
• Does not always fit – sponges and corals fixed in one place
however they do not make their own food through
photosynthesis

Microscopes further clouded the process
• Haeckel (1866) – created a third kingdom
– Protista
– "first established beings“
– "better regarded as a loose grouping of 30 or 40 disparate phyla
with diverse combinations of trophic modes, mechanisms of
motility, cell coverings and life cycles.”
Kingdoms

Fungi – were originally included with Plants
• They do not carry out photosynthesis though and
absorb food into their bodies

Bacteria – lack a nucleus and other organelles and
can gain energy in a variety of environments
• They were given their own kingdom as well
• Sometimes known as Eubacteria, Prokaryotae or
Monera

Archaea – kingdom created in the 1990’s
• For bacteria that live in very unique environments
– Acidic springs, salt lakes, hot springs
Kingdoms
Prokaryotes & Eukaryotes
 Two
main types of cell types based on
differences in size, structure and other
characteristics
 Fossil evidence
• Prokaryotic cells – 3.5 billion years ago
• Eukaryotic cells – 1.5 billion years ago
• Multicellular organisms – 700 million years ago
Kingdoms - subdivided

Domains
• Bacteria
• Archaea
• Eukarya

Within Eukarya we
find the protists and it
is believed that they
should be further
divided
• Agreement is difficult
Taxonomy
 Classifying
organisms
• Taxis – arrangement; Nomos – law
 Carolus
Linnaeus – circa 1750
• Used physical characteristics to classify
organisms into groups
• Latin and Greek stems (Felis domesticus)
• Names given often reflect characteristics of
organism or to honour a scientist or historical
figure
Hierarchy of Groups

Horse is more like a dog then a shark
• Horses and dogs are mammals

Horse is more like a shark then an oyster
• Vertebrates vs. invertebrates
Each kingdom is broken down into smaller
groups called taxon (plural taxa) to assist with
categorization
 Kingdom is largest down to species

Hierarchy of Groups
Plantae--includes all plants
Magnoliophyta--flowering plants
Magnoliopsida--dicots
Magnoliidae--subclass for Magnolia-like plants
Magnoliales--order for Magnolia-like plants
Magnoliaceae--family for Magnolia-like plants
Magnolia--genus includes all Magnolias
grandiflora--specific epithet


The name for a species consists of the genus name and the specific epithet. **Notice
that the endings will always tell you what rank you are dealing with, even if you don't
recognize the word. For example, the word "Sterculiaceae" could only refer to a
family.
As you go up, each category is made of groups of members of the category below it-e.g., there are many types of Magnolia but they all fit into the genus Magnolia. The
Magnolias and their relatives are all in the Magnoliaceae. Orders are made up of
families, subclasses are made of orders, etc.
Binomial Nomenclature
 Using
two words for each species
• Genus and species names used
• Canis lupus (wolf); Canis latrans (coyote);
Canis familiaris (domestic dog)
 Common
Names
• Problematic because they are not standard
– Mountain lion, puma and cougar
– P. 395, fig. 11.13
Origins of Diversity
 Similar
to others in your species but not
exactly the same
– Diversity between species begins within a species
– Certain different characteristics found between two
populations in response to their environment may
allow new species to develop
• First described in 1859 by Charles Darwin in
his book: On the Origin of Species by Means of
Natural Selection
Genetic Variation

Changes in characteristics are produced
by:
1. Random genetic mutations
–
–
Introduce variety
Especially important in asexual organisms
2. Selection for a particular characteristic that
increases the organisms chance of survival
and breeding in a particular environment
Determining Relatedness
 Taxonomy
involves evolution
• A need to determine the evolutionary history of
groups of organisms
– Comparing different species living today with those
that lived in the past
 Ways
by which scientists determine
relatedness
• Anatomy, development, biochemistry, DNA
Evidence from Anatomy

Classification between major classes can be
difficult
• Archaeopteryx – 150 million years ago

Fossils not required to find anatomical evidence of
evolution
• Human arm, horse’s leg, bat’s wing and whale’s flipper
• All specialized for what they do but they have the same
evolutionary origin - homologous
Evidence from Anatomy
Further Evidence
 Development
• Relatedness due to
appearance can be a
dangerous mistake
– Larval and adult
forms of organisms
can be very
different and they
are the same
species!
Further Evidence
 Biochemistry
• Comparisons due the molecules from which
organisms are made
• Comparisons of proteins and hormones
– Horseshoe crab is more similar to spiders then to
other crabs
Further Evidence

DNA
• Genes consist of sequences of nucleotide bases in a
segment of DNA
• Human single strands of DNA are compared to other
organisms and the amount of complementary base
pairing that occurs indicates relatedness
– 93% match with the macaque monkey
– 98% match with the chimpanzee
• DNA can also help to determine how long ago species
began to diverge from a common ancestor
– Mitochondrial DNA – mother to offspring
– It mutates at a predictable rate so it provides a molecular clock
for measuring rates of evolution
Phylogeny
 “True”
evolutionary history of groups of
organisms
 Common ancestors share characteristics of
all organisms that come after in a
phylogenetic tree
 Smaller differences help to distinguish
genus’ from each other
Phylogeny

Order Artiocactyla
• Even number of hoofed toes
on hindfoot; specialized teeth
and digestive systems for
vegetation


Family Bovidae – horns
Family Cervidae – antlers
• Genus Cervus – highly
branched antlers
• Genus Rangifer – broad,
palmate antlers (hand shaped)
Phylogenetic Tree
Cladistics
 Classification
scheme based on phylogeny
• Based on idea that each group of related species
has one common ancestor
• The current organisms retain some ancestral
characteristics and gain some unique
characteristics as they diverge from the ancestor
– like a phylogenetic tree but is
used to test alternative hypothesis about
differences in branching history
 Cladogram
Phylogeny vs. Cladistics



A phylogenetic tree is a specific type of cladogram where
the branch lengths are proportional to the predicted or
hypothetical evolutionary time between organisms or
sequences
The term "cladogram" emphasizes that the diagram
represents a hypothesis about the actual evolutionary
history of a group, while "phylogenies" represent true
evolutionary history.
To other biologists, "cladogram" suggests that the lengths
of the branches in the diagram are arbitrary, while in a
"phylogeny," the branch lengths indicate the amount of
character change.
Phylogeny vs. Cladistics



Bioinformaticians produce cladograms representing
relationships between sequences, either DNA sequences or
amino acid sequences. However, cladograms can rely on many
types of data to show the relatedness of species.
In addition to sequence homology (existence of shared ancestry
between a pair of structures, or genes, in different species)
information, comparative embryology, fossil records and
comparative anatomy are all examples of the types of data used
to classify species into phylogenic taxa.
So, it is important to understand that the cladograms generated
by bioinformatics tools are primarily based on sequence data
alone.