Q38-13TYU. - Campbell Biology

Question

This colorized SEM shows pollen grains from six plant species. Explain how a pollen grain forms, how it functions, and how pollen grains contributed to the dominance of angiosperms and other seed plants.

 

Step-by-Step Solution

Answer

Male gametophytes (pollen grains) are produced inside the anther. When specialized cells (microsporocytes) develop in immature anthers, pollen production begins. Pollen sacs, which produce pollen grains, are present in anthers.

 

Angiosperms, often known as blooming plants, are plants characterized by the development of covered seeds.

Step 1: Male gamete in plants

A flowering plant's male gametes are enclosed in a pollen grain within the anther. Insects, animals, or the wind carry them to other plants, attaching and fertilizing an egg. 

Microspores are made up of a single generating cell that splits unevenly in the microspore after meiosis.

Step 2: Function of pollen grain

The embryo sac's primary function is to transfer male gametes to their female counterparts (ovules - female reproductive cells) so that they can mature into seeds. As a result, the plant's sexual reproduction is simplified. 

Plants cannot generate seeds, fruit, or the next generation of plants without pollination, which is impossible without pollen grain.

Step 3: The dominance of angiosperms aided by pollen grains.

Angiosperms' success is mainly due to their unique reproductive systems, flowers, and fruit. By distributing pollen grains, flowers ensure pollination. Flowers protect the developing embryo and ovule inside the receptacle in a similar way.