Vertebrate Structure and Function
Answers discussion sessions EZO-31306
2018
Discussion 1: Biological concepts
1. Techniques for research: X-ray, dissection, EMG, Radiographics, natural markers, fluids, high-
resolution digital tomography. Examples: see book for figures → snake
2. The function of a structure in the environment
3. Paedomorphosis = embryonic characteristics of ancestor will be in adult descendant. Types:
a. Progenesis = early stop
b. Neoteny = slow growth
c. Postdisplacement = late start
Peramorphosis = adult characteristics of ancestor accelerated in descendent. Types:
a. Hypermorphosis = ends later
b. Acceleration = growth faster
c. Predisplacement = starts early
4. Plesiomorphic = ancestral trait, primitive condition. Synapomorphic = derived trait, after
transformation. The ancestral trait don't need to be lost. This is easy to make a phylogenetic tree:
easy view. Disadvantage: discussion about the trueness, convergent evolution.
4. Polyphyletic group: Birds+mammals
4. Change of vertebrae. To land → can move upwards and downward, fish can move laterally. When
for example the whale returned to the sea, it still moves tail upwards and downwards.
4. Homology = Same ancestor, Analogy = Same function, Homoplasy = same appearance.
convergent evolution = Independent from each other go through same development, no
common ancestor.
Discussion 2: Basal vertebrates
1. Dorsoventral inversion and inversion of blastopore: annelids have mouth first, vertebrates
anus first. Reject hypothesis because the groups are not derived from each other and the
dorsolateral inversion is developed later in the deuterostomes.
2. Cranium, sensory organs, more developed brain in Craniates. Haikouella fits in this transition
3. Neural crest cell functions: Table 5.2. Neurons, ganglia, cartilage, connective tissue, pigment
cells etc.
Notochord is important for locomotion (hydrostatic skeleton): the body can bent laterally
This is consistent with the spine, they have the same function but the spine has vertebrae and it
is not hydrostatic
No not all vertebrates have vertebrae: hagfish lost them secondary, coelacanth has also no
vertebrae and lamprey has reduces vertebrae
4. Recent agnatha are a monophyletic group. If you also take into account the fossils, they are a
paraphyletic group.
4. Placoderms have jaws, vertebrae and chorda is less important and have ‘gordels. ostracodermi
have never bones. They are paraphyletic group
4. yes bone is present in this group, mainly in teeth and scales. And sometime a thin layer around
cartilage.
4. Acanthodii: partly bony, newly formed jaw, spines on fins and body, ctenoid scales and a bony
operculum. Elasmobranchii: Cartilages skeleton, mouth downwards, fleshy fins, placoid scales
Nienke Klerks Answer discussion sessions EZO-31306 1
, Discussion 3: Land life: Amphibians to Mammals
1. Major innovations in body plan of teleostei compared to Neopterygii are: Homocercal tail,
moveable maxilla (kinetic skull), more bony vertebrae, swimbladder, leptoid scales and no
spiracle
2. Sarcopterygii are the ancestors of the land living animals. They have lungs, muscular fins with
humerus and femur and and intracranial joint. This is for the development of the leg very
important. Living forms are the lungfishes and Coelacanths. You can also say that all living
animals on land are derived animals from this group.
3. On land, the sound must go from air to water. In an aquatic environment the sound waves go
straight from water to water so there is no problem. On land, the waves must be converted.
Salamanders only use ground vibration in which they can feed the vibration through their limb or
jaw. The frog also uses this system, but has also a tympanum. So they can also convert the sound
of the air to water and hear this. Frogs are better equipped
4. Gymnophiona (Caecilians) are limbless, have reduced eyes, have tentacles, use internal
fertilization (using a phallodeum) against dehydration, skin moves independent from vertebral
column and they have no girdles.
5. Birds are distinguished by reptiles due to feathers and the fact that they are homeothermic.
They also have adjusted bone structure for flying, a synsacrum. THey are not considered a
separate class because they are imbedded in the group of reptiles and dino’s. Reptiles are seen
as paraphyletic group
6. Advantage: You get strong offspring and antibodies can be transferred to the offspring.
Disadvantage: The young is dependent of the mother for a long time it cost a lot of energy for
the mother. Pigeon milk is produced in the crop (also in males), but has the same function as
mammalian milk. There are less antibodies in pigeon milk, but regulation release in both groups
is by prolactin
Discussion 4: Integument
1. Teleost scales are cycloid or ctenoid. They lie under the epidermis, only have lamellar bone
(transparent), have no dentine, enamel or vascular bone. Sharks have placoid scales which have
enamel, a pulp cavity and dentine and grow from odontoblasts in the dermis. Bony fish also have
a slimy layer, but both groups have glands. The mucus is against predators and as protection.
Reptiles don’t have bony scales. They have keratinized scales with sometimes (in crocodile and
turtle) a bony plate underneath it.
2. A frog doesn’t have scales and has only a small layer of keratine for protection (stracum
corneum). They have mainly gas exchange through the skin, they have Leydig cells and poison
and mucus glands (in dermis, fish has mucus glands in epidermis). Besides that, they also have a
capillar network in the epidermis.
3. Apoptosis = programmed cell death. Feathers are composed of dead cells (or keratine), the
rachis are composed of the cells. The first feathers were fluffy and mainly for thermoregulation.
4. They all derive from the epidermis. But hair doesn’t have beta-keratine and feathers and
scales do have this. So they are not homologous, see figure slide 30.
5. Skin derivates are good for thermoregulation of endothermic animals. Glands help for
sweating and also fat is for isolation. Hair and feathers are also good for the isolation. daily
adjustments: Hair upwards, seasonal adjustments: more fluffy feathers, different coat.
6. Antlers: have branches and first they have living cells around it but these cells die and only a
bony structure is present. They grow at the top. Horns: No branches and a layer of dead cells
around it. They grow from the bottom. The horns of a giraffe are different: The cells on the
outside don’t dy and the bony structure is at the parietale bone of the skull.
7. Turnover rate is in the basic the same for every species. Shark doesn't have a repair of the
scales, birds change feathers 2 times a year. Reptiles shed their entire skin at once = ecdysis.
Nienke Klerks Answer discussion sessions EZO-31306 2
