Quiz 2

Question 1

1. Epithelial tissues and cell types:

Answer 1

Simple squamous, cuboidal, and columnar (single layers of flat, cube-like, and tall cells).

Stratified squamous, cuboidal, and columnar (multiple layers).

Pseudostratified epithelia appear layered but aren’t.

Transitional epithelia can stretch and are found in places like the bladder​

Question 2

Features of epidermis (are keratin types equally distributed among vertebrates?):

Answer 2

The epidermis is derived from the ectoderm and forms layers like the stratum basale (deep layer) and stratum corneum (outermost keratinized layer). Keratin types differ across vertebrates:

Mammals only produce alpha-keratin, while other tetrapods also have beta-keratin, which is harder and forms structures like scales and claws​

Question 3

3. Features of dermis

Answer 3

The dermis is mesodermal in origin, derived from dermatome cells, and is composed mainly of collagen. The dermis can form dermal bones through intramembranous ossification, contributing to structures like skull plates and parts of the pectoral girdle​

Question 4

4. How are epidermal structures formed (epidermal invagination vs dermal evagination):

Answer 4

Epidermal invagination: Structures like hair, teeth, and sweat glands are formed when the epidermis pushes into the dermis.
Dermal evagination: Structures like scales and scutes develop when the dermis pushes outward into the epidermis​

Question 5

5. Types of bone (lamellar/nonlamellar):

Answer 5

Lamellar bone: Has organized collagen and cells, typical in slow-growing, mature bones.

Nonlamellar bone: Disorderly collagen arrangement, found in fast-growing or immature bone​

Question 6

6. Intramembranous vs endochondral ossification

Answer 6

Intramembranous ossification: Bone forms directly from mesenchyme without a cartilage precursor, as seen in dermal bones.

Endochondral ossification: Bone forms from a cartilage model, which calcifies and is replaced by bone tissue​

Question 7

7. Three major divisions of the skull bones

Answer 7

Splanchnocranium: Supports gills and respiratory structures.

Chondrocranium: Forms the base of the skull, primarily from cartilage.

Dermatocranium: Includes bones that make up the sides, roof, and mouth​

Question 8

8. Patterns of bone evolution in the skull:

Answer 8

Early vertebrates had more bones in the skull, while derived forms (like mammals) have fewer, more consolidated bones​

Question 9

9. Embryonic derivation of vertebrae

Answer 9

Somites give rise to the sclerotome, which forms vertebrae. The cells divide, migrate around the notochord, and re-segment into the vertebrae, each composed of parts from adjacent somites​

Question 10

10. Types of vertebrae (acoelous, opisthocoelous, etc.):

Answer 10

Acoelous: Flat on both ends.
Amphicoelous: Concave on both sides.
Procoelous: Concave anteriorly.
Opisthocoelous: Concave posteriorly.
Heterocoelous: Saddle-shaped​

Question 11

11. Regionalization of vertebrae (why it matters):

Answer 11

Different regions of the vertebral column (cervical, thoracic, lumbar) have vertebrae with specific forms adapted for distinct functions, such as supporting the skull, articulating with ribs, or allowing flexibility​

Question 12

12. Parts of the ribs and functions of the ribcage:

Answer 12

Head: Articulates with vertebrae.
Neck and tubercle: Connect to vertebral processes.
Shaft: Extends around the body, supporting and protecting visceral organs and providing muscle attachment​

Question 13

13. Limb evolution (what may explain the initial development of fins?):

Answer 13

Fins likely evolved to stabilize motion in water, preventing rolling or yawing during movement. Dorsal and ventral fins helped control pitch​

Question 14

14. Parts of the fin (including differences in cartilaginous and bony fish fin rays):

Answer 14

Elasmobranchs (cartilaginous fish): Have ceratotrichia (keratin-based fin rays).

Bony fish: Have lepidotrichia (ossified or cartilaginous elements)​

Question 15

15. Major divisions of the limb:

Answer 15

Stylopod: Upper limb (humerus).
Zeugopod: Forearm (radius, ulna).
Autopod: Hand/foot (carpals/tarsals, metacarpals/metatarsals, phalanges)​

Question 16

16. Archipterygial and metapterygial fins and their significance for limb evolution:

Answer 16

Archipterygial fins: Symmetrical fin structure along the main axis.

Metapterygial fins: Asymmetrical, with a posterior shift in development, leading to limb differentiation​

Question 17

17. Development of the tetrapod limb:

Answer 17

The autopod primarily forms from the postaxial zeugopod, involving overlapping gene expression domains (Hoxa13, Hoxd13)​

Question 18

18. Pelvic/pectoral girdles, their evolution, and their attachment to the axial skeleton:

Answer 18

Pectoral girdle: Disconnected from the skull, supported by muscle.
Pelvic girdle: Always attached directly to the spine via the ilium​

Question 19

19. “Grades” of locomotion (unguligrade, etc.):

Answer 19

Plantigrade: Walk on soles (e.g., humans).
Digitigrade: Walk on toes (e.g., dogs).
Unguligrade: Walk on hooves (e.g., horses)