Cleavage in mammals is:
Correct answer: B. holoblastic unequal
- A. holoblastic equal
- B. holoblastic unequal
- C. superficial
- D. discoidal
Explanation
Cleavage in mammals is holoblastic unequal. Mammals have microlecithal eggs so they have holoblastic cleavage in which the segmentation lines pass through the entire egg, dividing it completely. As the eggs are microlecithal so one would expect that first cleavage will produce two equal blastomeres. But, this is not the case. The two blastomeres produced are unequal which divide further to form 4 unequal blastomeres and this process continues to form a ball of cells called morula. Superficial cleavage occurs in insects and discoidal cleavage occurs in birds.
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About Kingdom Animalia
Animals are multicellular, heterotrophic eukaryotes whose cells lack cell walls and chloroplasts, with specialised tissues in most groups. Coverage includes body symmetry, tissue layers, coelom, segmentation and levels of organisation, plus major phyla such as Porifera, Cnidaria, Platyhelminthes, Annelida, Arthropoda, Mollusca and Chordata.
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