Lecture 11 Flashcards
1
Q
Homology
A
- same structure shared by descendants of a common ancestor no matter how modified in descendent form
- important to evolution because we need to know if something we’re studying is related to something we already know
- comparision is vital–>is it the same thing?
2
Q
Analogs
A
- features that rose independently but look similar and don’t share a common ancestor
- convergence/parallel evolution
3
Q
Descent with modification
A
- descendants from same ancestor but results in branching pattern due to modification
- relates to characterization of homology (key idea)
4
Q
Homology vs. Analogy
A
- analogous structures have same function but aren’t evolutionarily linked (wings of fly and wings of airplane)
- homologous structures are highly conserved (forelimbs of vertebrates-same components or horns of antelopes-all very divers in structure but descendants of primitive horns)
5
Q
Evolutionary studies
A
- most based on homologous structures
- asking about think you can show to your satisfaction that they’re homologues.
- can start looking at new things including loss of elements, and changes for new function
- homology concept is used to trace evolution of homologous structures, including loss of element, or changes for new functions
- aids in identifying analogs in evolution
6
Q
Vertebrate forelimbs (birds)
A
- much different in structure but same components
- highly specialized for their function-know it’s doing something different, but you can’t see it.
- trace back history of bird forewing limb to an animal that has a different more basal structure as compared to that of the other vertebrates
7
Q
Levels of homology
A
- can be homologous at one level and analogous at the next
- bats and bird’s forelimbs are homologous but not at the level of wings those are analogous
8
Q
Artiodactyla
A
- started out with 5 digits but reduced to walking on 4
- then reduced in size to two
- lightweight running structure achieved
9
Q
Horses
A
- have one digit that evolved from 5
- went through stage of having three toes
- reduces weight of foot for running
- forelimbs are homologous but single toe is analog
10
Q
Criteria for homology
A
- shared spatial relationships in an anatomical system
- composition and properties of the structure
- historical continuity in evolutionary record (can you see earlier precursor, and earlier precursor of that?)
- e.g. vertebrate skull
11
Q
Vertebrate skull
A
- in evolution skulls of some bones lost, some bones fused together, and some adopted new function
- evolutionary trend you usually see: starts out complex, full of smaller bits that are eventually slimmed down to fewer components like in the case of the dog skull
12
Q
Jaw bone
A
- used to articulate behind the ear but now it articulates just in front of your ear
- the bones that used to be the jaw articulation that now no longer had a job were incorporated into the hearing apparatus (incus and malleus)
13
Q
Non-homology (homoplasy)
A
- convergence can produce similar solutions which can be considered false homologies–>homoplasy
- analogy: totally unrelated structures–>do direct relationship in evolutionary history
- homologous at basic structural level but analogous as independently derived structures
14
Q
Flight in vertebrates
A
- all use forelimb
- Pterodactyl: super long pinky with wing suspended from it
- bird: start with dinosaur ancestry; whole hand is fused to be sturdy support for feathers
- bat: umbrella method; suspended on all fingers
- HOMOLOGOUS as FORELIMBS; ANALOGOUS as WINGS
- insect wings are ANALOGOUS IN ALL WAYS to WINGS in VERTEBRATES
15
Q
Gene Homology
A
- organisms have homologous genes (the same gene which represents common descent of an ancestral gene in two lineages)
- e.g. Myoglobin-oxygen-binding protein found in tissues of all vertebrates so there are myoglobin genes