Lesson Overview Genes and Variation

Genetic Drift• Small populations• Definition• Genetic bottleneck• Founder effect

You are wandering in the tropical rainforest and a giant bright yellow

spider hangs dangling in its web in front of you. How would you determine if

you had discovered a new species of spider? If it was a new species of spider, what would you name it?

Why do we classify organisms?

• Communication–Problems with

common names• Show evolutionary

relationship• Systematics

–Taxonomy

Scientific Names

• 18th century– Latin or Greek

• Binomial nomenclature– Linnaeus– 2 word name– Latin– Writing

• Italics• First word – Genus• Second word – species• Felis catus

Linnaean Classification

• Hierarch ranking system

• Taxa (taxon)• Kingdom, phylum,

class, order, family, genus, species

Problems with Linnaean Classification

• Species are specifically defined• Other groups are subjective• New organisms hard to classify• Eugenics

–Classification of humans–Used to justify discrimination

The following is the Linnaean classification of a moose. Match each with the appropriate category

name. Hint: they are in order.

• alces• Alces• Cervidae• Artiodactyla• Mammalia• Chordata• Animalia

Evolutionary Classification

• Darwin’s tree of life• Phylogeny• Group by common

ancestors• Clades

–Definition–Advantage

Cladograms

• Root• Branch

– Speciation event• Distances• Patterns based on

– Hypotheses– Molecular data– Embryological

development– Fossil record

Creating Cladograms

• Traits inherited– From common

ancestor– Shared by many– Examples

• Derived characters– Related to

speciation event– Show closeness

of common ancestor

Reading Cladograms

• Node• Derived characteristics• Last clade

Clades and Linnaeus

• Many overlapping groups– Mammalia

• Birds very different

• Both systems are used

DNA and Classification

• Used sequenced genomes

• More genes in common– More derived

characters in common

– More recent common ancestor

• Shows relationships that can’t be seen– Examples