Transcript Introduction to Taxonomy 1

• GCO: How are living things organized into
groups for ease of study
– SCO: Describe peer review and explain how
classification systems developed as new evidence
concerning living things emerged (114-5, 115-7,
116-2)
– SCO: Identify questions, limitations, and
alternatives inherent in a classification system
(214-2, 214-7, 212-1)
Where else can creating groupings/categories be
of use to us in society, worldwide?
• Taxonomy: The science of classifying living things.
• Unity: Similar characteristics among organisms which
group them together (how similar organisms are).
• Diversity: Different aspects between organisms that
place them into different groups (how organisms are
different).
• Species: A group of organisms, alike in many ways, that
can interbreed under natural conditions to produce
fertile offspring.
• Genus: A group of similar species.
• Phylogeny: The evolutionary history of a species.
Living things MUST:
1) grow and develop
2) respire
3) have cells
4) use energy
5) respond to stimuli
6) generate heat
7) reproduce
• Helps organize information about organisms
• Makes it easier to identify both known, and
unknown organisms
• Shows relationships among organisms
• Think of scientists as reverse engineers
– Interested in the smaller, component parts and
how they form the larger organism
• Started classifying plants first, which led into
the classification of animals
• Began classifying according to superficial
divisions (Cesalpino – differentia)
– misleading?
• Aristotle
– Greek philosopher and naturalist
– First known classification system (2000+ years
ago)
• animal or plant
• where they lived (terrestrial (land), aquatic (water),
aerial (air), etc.)
• arranged hierarchically by complexity – scala naturae
(ladder of nature)
• not perfect (bats, birds, mosquitoes – can fly)
• John Ray
– 17th century English botanist
– Identified more than 18,000 plants – led to
modern plant taxonomy
– Used term species in classification
• species: group of organisms that looked alike and could
reproduce among themselves.
• Carolus Linnaeus
– 18th century Swedish botanist
– New classification system based physical/structural
characteristics
• more features in common, closer in relation
– “Father of Modern Taxonomy”
• binomial nomenclature (8 names before genus prior)
– Utility of Reproductive/Sexual Systems
• Less subject to environmental selection pressures
– Species “blend” together
• Not intended, but influential for Darwin and Wallace
– Ladder of species (separate rungs)
• Focus on physiology, anatomy, and behaviour
(Buffon)
– downplayed the importance of taxonomy
• Taxonomy became more of a continuum
(simple to complex)
• Correlation of characters (Cuvier)
• Affinities
– characters exhibited at any level (similarities in
groups – fins, hair, ability to feed young milk, etc.)
• Analogous Structures
– functionally similar, but made up of different
constituent parts.
• Fossil records (limiting, but useful)
• Evolution (Darwin)
– Sexual Selection
– Theory of Natural Selection
• Hierarchical system most common among
scientists
– graded/ranked
– artificial/arbitrary/limited
– imposed by humans
• Biochemical Similarity
– blood composition, protein sequence (amino
acids), etc.
• Genetic Similarity (how close are DNA/RNA
sequences)
• Fossil Record (limited – extinct)
• Behaviour
• Embryonic Development
• Comparative Anatomy
– homologous structures
• same basic pattern and same pattern of development –
not necessarily same function
How did the theory of evolution influence classification?
• In 1859, a British Scientist names Charles Darwin
explained how living things may have evolved over time.
Today, Darwin’s theory of evolution is accepted by most
scientists.
•Taxonomists started to classify living things according to
their phylogeny or evolutionary history. Today,
taxonomists try to develop an evolutionary tree for every
species which shows the inferred relationships among
different species (one common ancestor).
• Linnaeus developed a naming system called
binomial nomenclature.
– Each organism is identified by a two part scientific
name which is still used today.
– The first part is the name of the genus and the second
part is the name of the species.
– Indicates similarities in anatomy, embryology, and
evolutionary history.
– Based on some characteristic (colour, habitat, etc.)
• Castor canadensis (beaver from Canada)
– Latin names for his system as it allowed for a common
language, regardless of national origin
• Rules for writing the scientific name:
– The first letter of the genus is always capitalized.
– The first letter of the species name is never
capitalized.
– Both names must be underlined or italicized.
When creating groupings/categories at the
beginning of the lesson, you made certain
decisions based on previous knowledge and/or
your own observations. Explain why you chose
to divide things the way you did, and
rationalize/justify why you had difficulty.
“Science is the systematic classification of
experience.”
– George Henry Lewes