Monotremes

Question 1

What are Prototheria?

Answer 1

Group of animals including Monotremes
Egg layers

Question 2

3 Groups of extant monotremes

Answer 2

• Platypus
• Spiny anteater
• Echidna

Question 3

What groups are in the subclass Theria?

Answer 3

• Metatheria (marsupials): Short gestation time, long lactation, born in a altricial state.
• Eutheria (placentals): Long gestation time, short lactation

Question 4

Features of the monotremes?

Answer 4

• Lay eggs
• Sprawling gait - adaptation for swimming/digging.
• No teeth - keratinised pads
• Bill or beak
• Electroreceptors & mechanoreceptors on bill/beak used to detect prey.
• 5 pairs of sex chromosomes
• 1 vitellogenin gene - found in sauropsids - give rise to yolk formation. (Marsupials and placentals have lost this gene)

Question 5

When did Echidnas and platypus diverge?

Answer 5

• 19-48 MYA
• Obdurodon (ancestral form) - had teeth.

Question 6

How do platypus feed?

Answer 6

• 40,000 electrical receptors & 60,000 mechanical receptors in bill
• Closes ears, eyes and nose underwater when hunting.
• Bill detects prey signals