Question

Which of the following is an egg laying mammal?
A. Panthera leo
B. Elephas maximus
C. Hemidactylus flaviviridis
D. Ornithorhynchus anatinus

Answer 1

Hint:
Here all options are in Scientific names. So, common names are as follows:
A. Panthera leo – lion
B. Elephas maximus – Asian elephant
C. Hemidactylus flaviviridis – Genus of Gecko family
D. Ornithorhynchus anatinus – Duck-billed platypus

Complete answer:
Mammals are warm blooded vertebrate animals that can be distinguished by having fur or hair on the body and females have ability to secrete milk for their off-springs. Females possess special milk secreting organs called mammary glands.
Mammals have special ability to give birth to live off-springs, that is they are viviparous. This is possible due to presence of placenta which helps in providing nutrition during growth of off-spring inside the mother’s womb called foetus. Examples are Humans, Tigers, Monkey, etc.
Other animals who lay eggs are called Oviparous. They lay eggs and further they develop into organisms outside the mother’s body. Placenta is absent in this type of animal. Examples are frogs, birds, Crabs, fishes, etc.
So, option A is a Lion- Lion is a mammal which gives live off-springs. They have placenta and thus this option is not the correct answer.
Option B is Asian elephant – Elephants Also give birth to fully developed organisms that give birth to live off-springs. Thus, this option is also not correct.
Now, Option C is the Gecko family – Example is house Lizard. These organisms lay eggs for reproduction but these are not mammals, they belong to class Reptilia. Thus, this option is also not correct.
Option D is Duck-billed platypus – Mammals that lay eggs are only three: 1. Echidna
2. Spiny Ant Eater
3. Duck Billed Platypus

Thus, the correct answer is Ornithorhynchus anatinus – Duck-billed platypus.

Note:
There are five species of monotreme species that lay eggs that are one Duck-billed platypus and four species of echidna. Many species are found in Australia and New Guinea. These are very primitive for mammals because they lay eggs.