Direction for: In each of the following questions a statement of Assertion is given followed by a corresponding statement of Reason just below it. Of the statements mark the correct answer as
Assertion Holoblastic cleavage with almost equal-sized blastomeres is a characteristic of placental animals. Reason Eggs of most mammals, including humans are of centrolecithal type.A) extinction of these species from other regions
B) continental separation
C) absence of terrestrial route to these places
D) retrogressive evolution
Correct Answer: C
Solution :
Eggs containing a small amount of yolk or without any yolk are known as micro-lecithal/ alecithal/oligolecithal/meiolecithal eggs. Such eggs are found in starfish, Amphioxus, Eutherian mammals including rabbit and human beings. In such egg, equal holoblastic cleavage takes plae in which equal or approximately equal-sized blastomeres are produced.
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