Why do fish and frog produce more number of eggs

The type of fertilization in fish and frog is external fertilization i.e fertilization takes place outside the body. So the fish and frog produce a huge number of eggs each year to overcome the chance factor(sperm to come in contact with egg) and produce offsprings.

Explanation:

he forelimbs below belong to four species that descended in a direct line from the ancestral mammal shown above. of the four descendants shown, which species most likely appeared earliest in evolutionary history?