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Evolution on a short time scale
• Guppies are red or gray
• Killifish is green
• Pike cichlid is blue
Doesn’t eat much
Does eat
Biological Species concept
• Group of actually or potentially interbreeding
natural populations which are reproductively
isolated from other such groups
• If they cannot mate = reproductively isolated
(members of a different species)
• Several reproductive isolating mechanisms
– Prezygotic – before formation of offspring
– Postzygotic – after formation of offspring
Prezygotic isolating mechanisms
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Geographic isolation
Ecological isolation
Temporal isolation
Behavioral Isolation
Mechanical isolation
Prevention of gamete fusion
POSTZYGOTIC
– Hybrid infertility
Chapter 15
• Scientific name (or species name)
– Homo sapiens
• We call this the binomial system of naming
• First word is the genus (means group)
• Second word is the species
Linnean system of Classification
• Each level is called a taxon
• Taxonomy is the study of such
organization
• King Philip Came Over For
Green Spaghetti
• Each level above includes more
animals than the one below
• For example, Phylum Chordata
refers to organisms with a
backbone
– Class Mammal
– Class Sauropsida (lizards and
birds)
– Class Amphibia
– Etc.
What is a species?
• We defined it earlier as a group of organism
that can interbreed and produce fertile
offspring
– Problem!
– Some organisms do NOT sexually reproduce
– Others produce hybrids
• We define a species as a group of organisms
that share similar features
How to build a family tree
• Phylogenetic tree (cladogram)
• Clade – group of organisms that share
a derived trait
• Derived trait (character) – trait that
arose in a common ancestor
• Cladogram is comparative –
something with fur versus something
without fur
• Outgroup – organism that differs in its
derived trait (hagfish) compared to all
other organisms (ones that have jaws)
• Ingroup – organisms being compared
to ingroup (ones that have jaws)
• Sometimes cladograms are ‘weighted’
to show that some characters are
more important (example birds and
lizards)
Kingdoms
• Bacteria – cell wall
• Archaea – cell wall, live in extreme environment
• Protista – single cell that doesn’t fit anywhere
else
• Plantae – cell wall, energy from light
• Fungi – cell wall, energy from absorption
• Animalia – no cell wall, energy from digestion
• Bacteria
• Archaea
• Eukarya
Domains