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Class 10 Class 12

What is metagenesis? Mention an example which exhibits this phenomenon.


The definition of metagenesis is the reproduction cycle of an organism that alternates between sexual and asexual generations. An example of metagenesis is the reproduction cycle of a cnidarian.

The cnidarians exhibit alternation of generations in which one generation is the Polyp form while the other is the Medusa form 

What is the role of radula in molluscs?


The radula is a file-like rasping organ found in molluscs. It helps in scraping food. It also used for creating depression in rocks.


Ravi’s younger brother of class III stated that bats are like birds as they are able to fly.
How will you contradict him and make him understand that bats are mammals and not birds?


Flight is not only the criteria for classifying bat as birds. The features that bat has which prove that it is a mammal and not a bird are:

i. External ears

ii. Body covered with hairs and mammary glands. 

iii. They have skin instead of feathers and mouth.

iv. They have teeth instead of the beak.

v. They do not lay eggs but give birth to young ones.


Identify the phylum in which adults exhibit radial symmetry and larva exhibit bilateral symmetry.


Echinodermata


What is the importance of pneumatic bones and air sacs in Aves?


Pneumatic bones are hollow and hence are light weight. They help to reduce the weight and hence help the birds in flight. They also provide support.