Lecture 11 - 2.0

Question 1

Tetrapod Tree Stems (3):

Answer 1

1. Temnospondyls
2. Lepospondyls
3. Amniotes

Question 2

Amniotic Eggs (Key Features) (4):

Answer 2

1. Semi-permeable shell: allows gases to pass (O2, CO2), but keeps fluids inside
2. Extra-embryonic egg
3. Impermeable membranes - no direct exchange with the environment
4. Does not have to be in water - does not dry out

Question 3

Amniotic Egg: Extra-Embryonic Membranes (2):

Answer 3

1. Protection and gas transfer:
   - Amnion surrounds the embryo with water
   - Chorion surrounds the embryo and took sac
2. Waste Storage:
   - Allantois fills with waste as yolk proteins are used

Question 4

Amniotic Egg: Significance (3):

Answer 4

1. Allowed entire development of the organism on land and loss of the larval stage
2. Living on land led to more efficient respiration (gas exchange):
   - Allowed embryo to become larger before hatching compared to amphibians
   - More energy invested in each egg leads to lower number of eggs overall
3. Required internal fertilization (mating, fertilization, shell)

Question 5

Amniote Key Features: Other Dericed Characteristics (3):

Answer 5

1. Low skin permeability to prevent desiccation
2. Ventilation of lungs aided by ribs
3. Body support and locomotion

Question 6

Key Features: Low Skin Permeability to Prevent Desiccation (2):

Answer 6

1. Greater variation in skin (keratin)
2. Presence of lipids

Question 7

Key Features: Ventilation of Lungs Aided by Ribs (2):

Answer 7

1. Allowed for a long neck as now able to draw air through a long tube (trachea)
2. Space for elaboration of the nerves that supply the forelimb

Question 8

Key Features: Body Support and Locomotion (1):

Answer 8

Increased apparent weight (gravity) on land required stranger/stiffer skeletons

Question 9

Amniote Axial Skeleton (2):

Answer 9

1. Expanded regionalization of the vertebral column (cervical, thoracic, lumbar, sacral, caudal vertebrae)
2. Lumbar ‘ribs’ lost in some amniotes

Question 10

Amniote Axial Skeleton (Lumbar ‘Ribs’ Lost) (2):

Answer 10

1. No ribs in way of hindlimb forward movement
2. Allowed vertical plane of flexion of the column
   - Easier limb oscillation
   - Rapid locomotion

Question 11

Atlas and Axis Vertebrae (3):

Answer 11

1. Atlas and axis have reduced centrum and processes
2. Skull-Atlas Joint
3. Atlanto-Axial Joint

Question 12

Atlas and Axis Vertebrae (Akull-Atlas Joint):

Answer 12

Vertical nodding and horizontal tilting of the head

Question 13

Atlas and Axis Vertebrae (Atlanto-Axial Joint) (2):

Answer 13

1. Twisting movement
2. Maintains bony strength of neck while allowing cranial mobility

Question 14

Vertebral Column and Body Support (5):

Answer 14

1. Body is suspended between legs
2. Vertebral column as a ‘bridge’ between support posts
3. Makes use of arch designs
4. Trunk Vertebrae held in an archer’s bow-ike by abdominal muscles and sternum
5. Cervical vertebrae are held in a violin bow-like reversed arch by neck ligaments

Question 15

Changes in Limb Posture (2):

Answer 15

1. In many mammals and dinosurs, limbs are situated under the body for increased efficiency of limb swing during rapid locomotion
2. Digit and limb position also rotated inward, allowing for a forward thrust better aligned with the direction of movement

Question 16

Changes in Skull Openings (Fenestrae) Types (4):

Answer 16

1. Anapsid - no temporal fenestrae (earliest amniotes and turtles)
2. Synapsid - one lower temporal fenestra (extinct)
3. Diapsid - two temporal fenestrae (modern reptiles and birds)
4. Euryapsid - one upper temporal fenestra (likely derived from diapsid pattern in extinct marine reptiles)