Lecture 9 Flashcards
What is the biggest difference between like in water and life on land?
The effect of gravity on support and locomotion
What must land animals have in terms of support?
They must have a bony skeleton capable of transmitting backwards force to substrate and resisting forces
Describe the structure of land animal bone
Not uniform, dense on the outside, soft & spongey in the middle
What are joints covered in and what is it for?
Small layer of articular cartilage to reduce friction
Where does bone length growth occur?
At the epiphyses
What is the zygapophyses and what does it do?
They’re processes on the vertebrae & interlock to prevent twisting and bending
What’s changed in the axial muscles from sea to tetrapods?
Were used for locomotion in fishes & assumed 2 new roles in tetrapods. Postural support of body & ventilation for lungs
Name the two axial muscles in tetrapods
Nuchal ligament & Rectus abdominus muscle
Explain the path of evolution of axial muscles
Differentiation of epaxial then hypaxial muscles followed by development of transverse abdominus
What does the transverse dominus do?
Forces air out, amphibians still have this
Summarise the evolution of the appendicular skeleton
Limbs and limb girdles evolved, tetrapod limbs were derived from the fin of fishes
What girdle works well in water but not on land and why?
The pelvic girdle because it wasn’t attached to the skeleton
What did jointed limbs form for tetrapods?
Form holdfasts
What parts of the body was locomotion supported by?
In primitive tetrapods, locomotion via axial musculature
What happened to the pelvic girdle when changing for life on land?
It fused with modified sacral vertebrae
What connected the three paired bones on each side of early tetrapod to the vertebrae?
Ilia
What was no longer used to support the head and jaw muscles like in fishes?
The pectoral girdle
Name the two types of bones lost in tetrapods that fish have
Opercular & gular bones
What do tetrapods have instead of the opercular and gular bones?
A flexible neck
What holds the girdle to the sternum and the ribs?
Muscles & connective tissue
What does not articulate directly with the vertebral column?
The pectoral girdle
Name the function that the appendicular muscles had in fishes?
Hydrodynamic lift, steering and breaking
What occurred in regards to musculature between life in sea and life on land and what was still present?
More complex musculature began to appear as limbs took on new roles but ancestral pattern was still present
In regards to locomotion, which one is more expensive to move on/in?
Land
Describe something that happens in regards to skeletal structure when the size of an animal increases
Volume changes affect structural forces. Larger animals (elephants) their skeleton is proportionately thicker than a smaller tetrapod
What also differs between small and large tetrapods?
Stances differ, straight vs bent legs
What does a difference in locomotory styles minimise?
Shearing stresses on legs
Describe the structure of early tetrapods
Wide, flat, lengthened snout, teeth infront of eyes & combined feeding & breathing functions
What happened to the chondrocranium area during transition to land?
Oral cavity expanded, sucking air into mouth, floor of
mouth raised, air squeezed into lungs
The floor of the mouth was raised via what?
The hyoid apparatus
What expansion remained the same?
Same buccal expansion used for suction feeding in water
Why were tetrapods consequently lengthened?
Needed to place head over their prey & suction feeding can’t work in air
What is a key innovation for feeding on land?
A large and muscular tongue that works in concert with the hyoid apparatus
What is only found in terrestrial vertebrates?
Salivary glands
What did loss of gills also result in the loss of?
Branchiometric musculature, except gill levators
What did the cucullaris become in tetrapods?
Trapezius
What did the low density and viscosity of air enable?
Tidal ventilation
Describe the ventilation of amniotes
They have extraembryonic membranes & use a negative-pressure aspiration pump (opposed to positive-pressure buccal pump
Describe the negative -pressure aspiration pump
Expansion of the rib cage creates negative pressure that then sucks air into the lungs
What expands the rib cage to breathe?
Intercostal hypaxial muscles
What allows the development of a longer neck in amniotes?
Long, strengthened trachea with negative-pressure system
What has to be there for the prevention of blood pooling and to overcome gravity?
High blood pressures
How is blood plasma recovered and returned to the circulatory system?
If it leaks out the blood vessel walls, its recovered by the lymphatic system
What allows fluid in tissues to drain into venous system?
One-way system of blind-ended vein-like vessels that parallel veins
What was moved posteriorly as gills were lost and the neck evolved
The heart
What elements of the heart were reduced or absent in tetrapods?
Sinus venosus and conus arteriosus
What supplies lungs with deoxygenated blood?
Pulmonary circuit
What supplies lungs with oxygenated blood?
Systemic circuit
What accompanied the development of lungs?
Double circulation
Describe the change in aortic arches in tetrapods
2&5 were lost, three arches were retained: 3rd 4th & 5th
Where do the carotid, systemic & pulmonary arches go to?
Head, body & lungs
What happened in teleosts and derived ray-finned fish?
Lungs converted to swimbladder; pulmonary system lost. Aortic arch 2 and spiracle lost.
What was obtained in the modern amphibian?
Cutaneous arch to skin
