Which of the following is responsible for variation?

$(a)$ "Recent fossils are found closer to the earth's surface." Comment on the statement stating reason.
$(b)$ List two factors which could lead to the rise of new species.

Explain analogous organs and homologous organs. Identify the analogous and homologous organs amongst the following:
Wings of an insect,wings of a bat,forelimbs of frog,forelimbs of a human.

In which animal did the eyes originate first?

In pea plants, which trait is dominant between height and dwarfness?

With the help of suitable examples,explain why certain traits cannot be passed on to the next generation. What are such traits called?