Question

Difference between prototheria metatheria eutheria on the basis of yolk

Answer 1

eutheria contain alecithal eggs which mean ,do not contain yolk.
ex,human eggs.
metatheria contain microlecithal eggs which means,egg contain a little amounts of yolk
ex.amphians

Answer 2

✌️✌️hey mate,

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➡️Prototheria:

1. They are OVIPAROUS.
2. Ear is devoid of pinna .
3. Scrotum is absent in male.
4. Vagina and uterus are absent.
5. Nipples are absent over the mammary gland.
e.g.,
•Echidna,
•Tachyglossus,
•Ornithorhnchus.

➡️Eutheria:
1. They are ViViPAROUS.
2. pinna is present except in aquatic forms.
3. the scrotum is present on the sides and behind the penis.
4. they are single structure.
5. nipples are present.

➡️Metatheria:
1. They are ViViPAROUS.
2. ear possess a pinna.
3. scrotum is present but infront of penis.
4. both vagina and uterus are double.
5. Nipples are present.

e.g.,
•Macropus,
•Didelphis.
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thanks...