Lab 4 - Comparative Worksheet 1- General Skeletal system What was the main form

Question

Lab 4 - Comparative Worksheet 1- General Skeletal system What was the main form of axial support before skeletal systems became internalized? How does the gross morphology of the aquatic organisms skeletal system differ or remain similar dependent on their: 1) environment (habitat) 2) mode of locomotion 2 - Skulls How do the skulls of the lamprey, dogfish, mudpuppy and cat differ? Why is this? (yes think, splanchnocranium, chondrocranium and dermatocranium) Senses Review the casing and foramen for the senses. What is their shape and position on the skulls? What do these features tell you about the senses, how do they give each organism any ‘advantage’? 3 – Axial skeleton How are the vertebrae of the dogfish, mudpuppy and cat similar? What does the notocord become in these species? How do these vertebrae articulate? Why is this the same/different for each animal? 4 – Appendicular skeleton How do the pelvic and pectorial girdles change over the species? What remains the same? What differs and why? What are the advantages of these changes?

Explanation / Answer

1. The skeleton begins to form in embryo at around 6 weeks post–conception. It firstly develops as cartilage, and lateron it gets ossified, it is by which cartilage is replaced by bone. The bones later on continues to elongate and harden, whereas the epiphyses, or heads of bones, will be ossify last

The skull of pinniped are similar to of terrestrial mammals and its is characterized by

a large eye orbits, and a relatively short snout, constricted interorbital region, and large orbital vacuities ( which includes unossified spaces in ventromedial wall of eye orbit. Tin the studies the skull of otariids is instantly differentiated from those of phocids whereas the walrus in development of large, supraorbital processes were shelf-like of the frontal bones. In addition to this, the relationship of nasals to frontals is a unique among otariids; tfrontals extend anteriorly between nasals forming W-shape nasofrontal contact.

2. As we slice dog fish off the hyaline cartilage, which were slicing through the chondrocranium (neurocranium), a box around the brain. The first part of the brain comes is cerebellum, which sticks up; rest of brain is deeper. The nerves and brain were cream coloured. The trochlear nerve, runs superficially from cerebellum through cartilaginous neurocranium, to superior oblique muscle of eye. Nerves should be excreated out of cartilage. The cartilaginous peg (optic peg) between optic lobe and eye is orbital process of palatoquadrate (upper jaw). It helps keep jaw in place.

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