Biodiversity and Patterns in Life
Classifying life
• Carl von Linne (1707-78)
• Botanist and naturalist
• Began to classify
organisms based on
observed characteristics
Turn in your diagram/classification for 5pts extra credit
Classification activity
Lion
Magnolia
Crab
Sea Lion
Tiger
Orangutan
Fish
Cat
What traits do they share?
Lion
Cells with nuclei, no cell walls, backbone, produces milk, large canine
teeth, long tail, ability to roar
Plant
Cells with nuclei, cell walls
Crab
Cells with nuclei, no cell walls
Cat
Cells with nuclei, no cell walls, backbone, produces milk, large canine
teeth, long tail
Tiger
Cells with nuclei, no cell walls, backbone, produces milk, large canine
teeth, long tail, ability to roar, dark vertical stripes
Fish
Cells with nuclei, no cell walls, backbone
Orangutan
Cells with nuclei, no cell walls, backbone, produces milk
Sea Lion
Cells with nuclei, no cell walls, backbone, produces milk, large canine
teeth
Nested hierarchy of shared
characteristics
Species
Kingdom Phylum
Class
Order
Family
Felidae
Carnivora
Mammals
Animals
All living things
Chordates (vertebrates)
Genus
Panthera
Linnaean system of classification
• Use observable shared or divergent
characteristics to classify organisms
in a nested hierarchical system
• Organism grouped at high levels of
classification share a few, very
general traits.
• Organisms grouped at lower levels
of classification share many, very
specific traits with each other.
• Give unique binomial name to each
species (Genus species; e.g.
Panthera tigris)
Phylum
Chordata
Genus
Panthera
Whence diversity?
Why do organisms share characteristics?
Where does diversity of life come from?
Two major hypotheses
H1. Species were fixed, had always
been the way they are. The
assumption there is balance in
nature.
Both hypotheses had been
postulated in many different
cultures, Ancient Greece, Rome,
China, Medieval Islam
Scientific evidence to test these
hypotheses began to be collected
in the age of exploration (16001800s)
H2. Life on earth has changed over
time
Puzzling Observations
Homologous structures: structures that have
underlying similarities but very different
functions
Puzzling Observations
Vestigial traits: structures or
traits that do not serve a
function and are degenerated
in form.
Puzzling Observations
• Similarities in embryo development
Why is bear species size
correlated with latitude?
Biogeography
Why is the highest
biodiversity around the
equator?
Why do you find big flightless
birds that look similar to each
other on totally different
continents?
Why do animals at the
North pole look like animals
at the South Pole?
Analogous traits
Traits that are similar in
function, but not
necessarily sharing an
underlying structure
(e.g. wings of bats, birds
and bees)
Cactus
Euphorbia
Fossils
-Where are these
organisms?
-Why do some of them
resemble extant (alive)
organisms?
- Extinction was not a
widely accepted concept
before the 1800s
Reflection (10 points)
Observations
• Hierarchy of shared
characteristics
• Homologous structures
• Vestigial traits
• Biogeography
• Adaptations
• Analogous traits
• Fossils
• Embryology
Question
• Based on the observations we’ve
discussed, does one hypothesis
seem to be more valid than the
other? (H1. Life is fixed, H2. Life
has changed)
• Explain your reasoning. And
which of the observations
support the hypothesis
• If both hypotheses are equally
valid at this point, explain which
evidence supports each and
discuss what other evidence
would be important in deciding.
Developments in Geology
• Understanding the history of life on earth
went hand in hand with understanding the
history of the earth (advances in the
science of geology)
• Leading understanding at the time was
catastrophism (earth generally fixed except
for a few catastropic events)
• Uniformitarianism: Many geological
formations can be explained by the
accumulation of gradual changes over
many many many years
Conclusions:
• Earth has been around for a long time
(millions of years, not thousands)
• The earth has changed over time.
Charles Lyell
(1797-1875)
Charles Darwin & Alfred Wallace
• HMS Beagle (1831) chart the
coast of South America
• Darwin was offered job as
naturalist, collecting specimens
and recording observations
• Naturalist
• 1848 expedition to Amazon
• 1854-1862 travelled through Malay
Archipelago studying island biogeography
• Known as the father of biogeography
Evolution
• Change over time
• Biologically: Descent with modification
• Small scale: changes in gene frequencies in a
population from one generation to the next
• Large scale: accumulation of changes over
thousands/millions of years leads to the descent
of different species over many generations
Thus...
• All organisms share common ancestors
• Some are more distant than others
• Classification is really study of genealogy
Look back on taxonomy
Common panthera ancestor
Common felis ancestor
Common carnivora ancestor
Common mammal ancestor
Common vertebrate ancestor
Common animal ancestor
Common ancestor of all living organisms
Second cousin
Geneaology
Siblings
Cousin
Mom
Grandma
Great grandma
Development of taxonomy
What evidence is there that all living
organisms share a common ancestor?
• What traits do al living organisms share?
Next time
• More on evolution
• The mechanism driving change
• Is there a conflict between science and
religion?