18 march 20152108homology.ppt1 theory of evolution by natural selection homology and biogeography
TRANSCRIPT
18 March 2015 2108Homology.ppt 1
Theory of Evolution by Natural Selection
Homology and
Biogeography
18 March 2015 2108Homology.ppt 2
Speciation and Homology
• Speciation produces “sister species” descended from a common ancestor
• Descendant species retain characters of common ancestor possibly in modified form.
• “descent with modification”Modified character = HOMOLOGY
18 March 2015 2108Homology.ppt 3
Evidence for common ancestry (genealogical relationship)
• Same character in 2 or more species inherited from a common ancestor = HOMOLOGY possibly modified since split from sister species
• The common ancestor no longer exists, so how can we tell what’s a HOMOLOGY and what’s not?
18 March 2015 2108Homology.ppt 4
Criteria for HOMOLOGY (Operational definition)
• 1. Position in relation to other body structures.
• 2. Embryonic origin• 3. Continuity -- Characters homologous to
another character are homologous to each other.
18 March 2015 2108Homology.ppt 5
Criteria for HOMOLOGY
• 1. Position in relation to other body structures.• tetrapod forelimbs
• humerus
• radius & ulna
• carpals
• metacarpals
• phalanges
18 March 2015 2108Homology.ppt 6
Criteria for HOMOLOGY
• 1. Position in relation to other body structures. insect wings, legs antennae
18 March 2015 2108Homology.ppt 7
Criteria for HOMOLOGY
• 1. Position in relation to other body structures.• flower parts
• sepals
• petals
• stamens
• carpel (s)
18 March 2015 2108Homology.ppt 8
Criteria for HOMOLOGY
• 2. Embryonic origin similar developmental origin.• pharyngeal arches
• limb buds
• tail bud
• lobes of brain
• heart
18 March 2015 2108Homology.ppt 9
Criteria for HOMOLOGY
• 2. Embryonic origin similar developmental origin.• 1st pharyngeal arch
jaw
• limb buds
• lobes of brain
• heart
18 March 2015 2108Homology.ppt 10
Criteria for HOMOLOGY
• 3. Continuity -- Characters homologous to another character are homologous to each other.• hyomandibular stapes
(stirrup)
• quadrate incus (anvil)
• articular malleus (hammer)
18 March 2015 2108Homology.ppt 11
Ways HOMOLOGY provides evidence for evolution.
• Comparative Anatomy: • Comparative Fossil Anatomy (“Fossil Record”)
• Comparative Embryology:
• Comparative Physiology & Biochemistry:
18 March 2015 2108Homology.ppt 12
Comparative Anatomy
• Modification of existing characters/organs for OTHER FUNCTIONS• Forelimbs wings in
birds,
• Forelimbs whale flippers
• 1st gill arch vertebrate jaw
18 March 2015 2108Homology.ppt 13
Comparative Anatomy
• Modification of existing characters/organs for OTHER FUNCTIONS• Teeth fangs in
rattlesnake
• Salivary gland venom gland
18 March 2015 2108Homology.ppt 14
Comparative Anatomy
• "Imperfection" of adaptation• Panda's "thumb"
• actually “radial sesamoid” bone
• Human backbone • "Oh, my aching . . ."
• after 2-3 million years, we are still subject to back strain
18 March 2015 2108Homology.ppt 15
Comparative Anatomy• Modification for NO function
– “Vestigial” organs = "Senseless signs of History"• Characters that make no sense in present, but were used &
needed in ancestors
18 March 2015 2108Homology.ppt 16
Comparative Anatomy
• Modification for NO function– “Vestigial” organs
• Pelvic rudiments of whales
18 March 2015 2108Homology.ppt 17
Comparative Anatomy
• Modification for NO function– “Vestigial” organs
• Limb bones & claws of boas, pythons
• Human coccyx
18 March 2015 2108Homology.ppt 18
Comparative Embryology
• Some traits seen only in embryos or larvae.
• HOMOLOGY with larval or adult traits in other organisms.• Notochord in vertebrates.
• Notochord & dorsal nerve cord in tunicate larvae.
• Bilateral symmetry in echinoderm larvae
18 March 2015 2108Homology.ppt 19
Comparative Fossil Anatomy: The Fossil Record
• HOMOLOGY relates fossils to existing organisms • Change in lineages
• Extinction
• Examples:• Fossil elephants
• fossil horses
18 March 2015 2108Homology.ppt 20
Comparative Fossil Anatomy: The Fossil Record
• HOMOLOGY relates fossils to existing organisms • Change in lineages
• Extinction
• Example:• trilobites
18 March 2015 2108Homology.ppt 21
COMPARATIVE Physiology & Biochemistry
• HOMOLOGY applies to physiological & metabolic processes• Glycolysis and Krebs cycle• Mechanisms of cell signaling
18 March 2015 2108Homology.ppt 22
COMPARATIVE Physiology & Biochemistry
• HOMOLOGY applies to biochemicals• Proteins’ amino acid sequences • DNA as genetic code• RNA to translate code into protein structure• ATP as “energy currency” of cells
18 March 2015 2108Homology.ppt 23
Convergence
• Evolution (adaptation) of dissimilar organisms to common function, superficially similar characters.• piercing sucking mouth in bugs,
mosquitoes, fleas, butterflies• "wings" in bird, bat, pterosaur,
insect, (airplane ??)
• Convergent character NOT present in common ancestor!!
18 March 2015 2108Homology.ppt 24
Biogeography:
• Geographic distributions of species, genera, families, etc.
• Organisms have evolved independently in different parts of the world.
18 March 2015 2108Homology.ppt 25
Biogeography:
• Organisms have evolved independently in different parts of the world.• Endemic species, genera,
etc. on islands.• Hawaiian honeycreepers
• Galapagos finches
18 March 2015 2108Homology.ppt 26
Biogeography:
• Organisms have evolved independently in different parts of the world.
• Continents as big islands• "Patagonian hare" in S. America
• Convergence of placental and marsupial mammals
• Australia• marsupial "wolf," “badger” (T. devil), “mole,” “mouse,”
“deer” (kangaroo),
• South America
• marsupial "horse," "saber-tooth” predator
18 March 2015 2108Homology.ppt 27
Biogeography:• Used with fossil record to reconstruct evolutionary history.
• Camels in Asia = camel, dromedary • in S. America = llama, alpaca • How can this distribution be explained?
18 March 2015 2108Homology.ppt 28
Biogeography:• Used with fossil record to reconstruct evolutionary history.
• Alligator in SE USA and China/SE Asia,• Hellbenders in SE USA and China, • Cyclocosmia in SE USA and Malaysia
18 March 2015 2108Homology.ppt 29
Biogeography:
• Used with fossil record to reconstruct evolutionary history.• Isthmus of Panama
divided Caribbean from Pacific about 3 MYA
• species crabs, snails, fish, etc. have nearest relatives on other side of land barrier.