Major Themes in Comparative Anatomy, with review of important concepts Flashcards
(23 cards)
Distinguish the three mechanisms that can lead to morphological similarity?
Homology, analogy, homoplasy
Homology
Features that share common ancestry (only evolved once in a lineage)
Example: arm bones (1 bone, 2 bone, many bones)
Analogy
Features with similar function but not shared ancestry
Example: bird and bat wings
Homoplasy
Features with strong resemblance due to convergent evolution due to similar selection pressures
How can we differentiate convergence from common descent?
Positional criterion: elements location/position
Structural criterion: numerous features in common
Transitional criterion: historical/developmental intermediates
Function is NOT criterion. Exception: muscles: origin/insertion, innervations
What are the 5 distinguishing characteristics of chordates?
1) pharyngeal gill slits
2) notochord
3) post-anal tail
4) dorsal hollow nerve cord
5) iodine binding subpharyngeal organ
What are the main functions of chordate body systems?
Integumentary: protective
Muscular system: movement
digestive system: process nutrients
respiratory: gas exchange w/ environment
circulatory system: deep exchange
urogenital sytem: excretion, reproduction
endocrine system: chemical control
nervous system: overall control
sensory system: information gathering
What are the vertebrate innovations with respect to body systems?
“New head” - feeding, breathing, sensing, communicating
Skeletal system: framework
Respiratory system: ventilation
Why are many morphological structures compromised?
Compromised because of conflicting needs
- Often not ideal for some
- Most structures must serve multiple roles
Natural selection acts on all life stages
- To survive an organism must be viable at all life stages
Remember that evolution acts at all life stages and that different stages may have very different challenges and selection pressures.
Natural selection acts on all life stages, to survive an organism must be viable at all life stages
Major stages of vertebrate life history
Fertilization –> embryonic development –> maturation –> adulthood –> senescence (sometimes)
Ectoderm
Mesoderm
Endoderm
Recall that the vertebrate “new head” is built from the vertebrate-specific neural crest cell population and the neural placodes.
Vertebrate body, especially head, is a unique collection of structures of neural crest and placed origin, from filter feeding to active predation, anatomically distinct from each other, sets vertebrates apart from all other chordates
What does the hourglass model explain? Which genes are responsible for this phenomenon? What would be the result of mutations in these genes?
Hourglass model explains how evolutionary diversity starts very different, then goes very similar and ends very different, due to the Hox genes, mutation in the hox genes lead to improper development
Three main “rules” of Evo-Devo
Small genetic toolbox: hox genes, highly conserved across different species
Modularity of gene activities: different enhancers, same gene can be reused in different contexts allowing for variation
Gene duplication: makes copies of genes, allows for one copy to stay same one to change
Recognize the importance of Hox cluster transcription factor genes, their amplification during two rounds of whole genome duplication in early vertebrates, their role in AP axis delineation and their re-use in the evolution of other body axes such as the proximo-distal axes of paired appendages and genitalia.
When do we first see (in which taxa) do we see the innovations: body plan inversion, first pair of appendages, two rounds of whole genome duplication, jaws, TWO pairs of appendages, the fish-like and tetrapod-like characteristics of TikTaalik.
Body plan inversion: after split from ambulacraria
First pair of appendages: ostracoderms
Two rounds of whole genome wide duplication: after split of agnathans
Jaws: placoderms
Two pairs of appendages: placoderms
What are the main consequences of the lifestyle shift involved in moving from water to land?
Vertebrates out of water must:
- Provide their own support
- Modify locomotory style
- Develop complex appendicular musculature
- Have a neck
- Protect body, eggs, young against water loss
- Lose gills and gain lungs
- Lose lateral line system and electroreceptors
- Evolve terrestrial sensory systems
- Feed differently
- Have muscular tongue and saliva
- Locate drinking water
- Osmoregulate differently
- Modify modes of excretion
- Fertilize eggs more precisely
What are the consequences of increasing body size?
Must greatly increase support system
Must have muscles rather than just cilia
Must have respiratory pump rather than just cilia
Must have greatly increased respiratory surface
Must increase absolute amount of food eaten
Must have efficient food transport and processing mechanisms
What are the typical characteristics of secondarily aquatic vertebrates?
Evolve a fusiform body shape
Reduce/lose appendages
Lose or simplify teeth
Excrete ammonia
Evolve salt glands or hypersaline urine
Lose/reduce salivary glands and tongue
What are the consequences of endothermy?
Endotherms can be active more of the time
Can survive in areas ectotherms can’t
Can have a bigger brain
Eat more and more often
Need more efficient food processing
Need an efficient 4-chamber heart
