Lec 10 part a

Question 1

Phylogeny of ocncern

Answer 1

Chondrichthyes

Question 2

Overall diversity of Chondrichthyes

Answer 2

1200 extant species

Most are marine, small number occur in freshwater

Question 3

3 clades with considerable diversity

Answer 3

Galeomorphii, squalomorphii, and batoidea

Question 4

Synapomorphies and diagnostic features of Chondrichthyes

Answer 4

Placoid scale

Tesserae

Pelvic clasper

Rectal salt gland

Question 5

Placoid scales are constituted of

Answer 5

Enamel and dentine

Question 6

Placoid scales do not grow in size, but

Answer 6

periodically shed and are replaced by large scale

Question 7

Functional significance of Placoid scales

Answer 7

Physical protection

Reduced viscous drag

Improve swim efficiency

Question 8

Synapomorphies of Chondrichthyes

Answer 8

Calcified cartilage makes up most of the skeleton

Question 9

Synapomorphies of Chondrichthyes

Tesserae

Answer 9

Crust of calcified cartilage covering the external of the cartilaginous skeleton

thin Polygonal plates

Protective layers with decent flexibility

Question 10

Jaw carries

Answer 10

Real teeth with enamel/enameloid and dentine

Question 11

Teeth replaced

Answer 11

Frequently throughout the life of an individual
(Polyphyodont)

Question 12

Synapomorphies of Chondrichthyes

Pelvic clasper

Answer 12

Appendages on the pelvic fins of the male, used to transfer sperm to cloaca (urogenital opening) of the female

Question 13

Synapomorphies of Chondrichthyes

Rectal salt gland

Answer 13

A small and highly specialized gland within the body cavity near the cloaca

Helps maintain osmotic balance by secreting salts

Question 14

Electroreceptors

Answer 14

Ability to detect external electric fields generated typically by muscle activities of other vertebrates

Question 15

Ampullae of Loronzini

Answer 15

Type of passive electroreception

Found on head and pectoral girdle