VERTEBRATE STRUCTURE AND
FUNCTION
EZO-31306
16 DECEMBER 2019
WAGENINGEN UNIVERSITY & RESEARCH
Lieke Luiten
, This summary contains parts of the book Vertebrates: Comparative Anatomy, Function,
Evolution by Kenneth v. Kardong (8th edition).
Table of contents
Week 1 Biological concepts + Basal vertebrates ..................................................................................... 2
Biological concepts .............................................................................................................................. 2
Basal Vertebrates ................................................................................................................................ 6
Week 2 Land life + Integument ............................................................................................................. 13
Land life ............................................................................................................................................. 13
Integument ........................................................................................................................................ 23
Week 3 Skull + Postcranial skeleton ...................................................................................................... 32
Skull ................................................................................................................................................... 32
Postcranial skeleton .......................................................................................................................... 39
Week 4: Muscles + Form and function .................................................................................................. 48
Muscles.............................................................................................................................................. 48
Form and function ............................................................................................................................. 59
Week 5: The nervous system + the respiratory system ........................................................................ 64
The nervous system........................................................................................................................... 64
The respiratory system ...................................................................................................................... 69
Week 6: Circulation + Urgenital System ................................................................................................ 78
Circulation ......................................................................................................................................... 78
Urogenital System ............................................................................................................................. 91
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,Week 1 Biological concepts + Basal vertebrates
Lectures 1, 2 & 3 and discussion meetings 1 + 2
Biological concepts
Similarities (page 15-16)
In different organisms, corresponding parts may be considered similar to each other by three criteria:
ancestry, function and appearance. The term homology applies to two or more features that share a
common ancestry, the term analogy to features with a similar function, and the term homoplasy
(denk aan plastisch chirurgie, dus uiterlijk) to features that simply look alike. Convergence
(=organismen die aanpassen aan dezelfde niche(leefomgeving)) may lead to homoplasy. Convergent
evolution= independent from each other, go through same development, but no common ancestor.
A special case of homology is serial homology, which means similarity between successively
repeated parts in the same organism.
Grades and Clades (page 24-30)
Modern vertebrates are the results of millions of year changing. We may examine particular
characters, using them to track the history of these changes.
Plesiomorphic trait (primitive condition)= the earlier (or ancestral) state of a character
Synaphomorphic trait (derived condition)= the later (or descendant) state after transformation
Taxon= group of organisms, two types:
- Natural taxon= accurately depicts a group that exists in nature resulting from evolutionary
events;
- Artificial taxon= does not correspond to an actual unit of evolution.
Sister group= taxon which is most closely related to the group we are studying
Grade= an expression of the degree of change or level of adaptation reached by an evolving group
Clade= a lineage-all organisms in a lineage plus the ancestor they have in common
Traditional systematics places together organisms with similar or homologous characteristics. The
newer phylogenetic systematics places together organisms belonging to the same clade and hence is
also called cladistics. Genealogy(=stamboom gerelateerd), not within-group variation, is the basis for
recognizing a clade. The dendrogram depicting this genealogy is a cladogram. The assortment of taxa
we are interested in examining is our ingroup; the outgroup is close to but not part of this
assortment and is used as a reference.
Names of clades:
- Monophyletic= includes an ancestor and all its descendants-but only its descendants.
- Polyphyletic= groups formed on the basis of nonhomologous characters (poly= meer dus
meerdere ancestors)
- Paraphyletic= groups that include a common ancestor and some, but not all, of its
descendants (para, paralympics= gehandicapt dus some but not all!)
Crown group= smallest clade that includes all living members of a group and any fossils nested
within.
Stem group= the set of extinct taxa that are not in the crown group but are more closely related to
the crown group than to any other.
Total group= crown + stem group
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, Maturation (page 197)
Metamorphosis (page 197)
As the events of early development come to a close, the embryo takes shape. If this emerging
individual is free-living and fundamentally unlike the adult, it is termed a larva and will eventually
undergo metamorphosis= a radical and abrupt postembryonic change in structure to become an
adult. The overall process of ontogeny (=development) is ongoing throughout the life of the
individual and does not end at hatching or birth.
If conditions experienced by the larva are more hospitable than those endured by the adult, the
balance of time an individual spends as a larva compared with its stretch(=uitrekken) as an adult
might change adaptively as well. For example, in some species of lampreys, the individual may persist
in larval form for several years, metamorphosing into the brief adult form only long enough for a few
weeks of breeding before dying. The sole function of the adult is reproduction.
Some frog larvae hatch into an aquatic environment teeming(=wemelend/vol met) with predators.
Apparently such challenges favor direct development, wherein the young embryo develops directly
into the young froglet, bypassing(=overbruggen) the larval stage.
Heterochrony (page 198)
All vertebrates pass from embryo through a larval and/or juvenile stage on their way to the adult
stage. Evolutionary modification of adults often begins here first, in the early stages of ontogeny, by
relative chances in timing of developmental events. The term heterochrony describes such a phyletic
change, wherein there is an ontogenetic shift in the onset or timing of a feature’s appearance in a
descendant species compared to its ancestor.
Heterochrony includes several ontogenetic processes that affect the rate of growth of a part, the
onset of its debut during embryology, or the offset of its growth period. Two types:
• Paedomorphosis: embryonic or juvenile characteristics of ancestors appear in the adults of
descendants. Further divided in: progenesis, neoteny, post-displacement;
• Peramorphosis: the adult characters of ancestors, exaggerated or extended in shape appear
in adult of descendants. Further divided in: hypermorphosis, acceleration, pre-
displacement.
The term recapitulation is an old and troubled term, related to heterochrony. In recapitulation,
descendant species as embryos or juveniles resemble adult stages of ancestors.
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