Chapter 28, Problem 1TYK

Which of the following is not an evolutionary trend among plants?

a. developing vascular tissues

b. becoming seedless

c. having a dominant diploid generation

d. producing nonmotile gametes

e. producing two types of spores

Summary Introduction

Introduction:

Plants are the multicellular eukaryotes that fall under the phylum Plantae. On early Earth, the plants used to live underwater and during the course of evolution, the plants became terrestrial. Plants are the ultimate source of nutrition for all the life forms present on Earth and have evolved in many ways to adapt to the terrestrial life.

Answer to Problem 1TYK

Correct answer:

Becoming seedless is not an evolutionary trend among plants.

Explanation of Solution

Explanation/justification for the correct answer:

Option (b) is becoming seedless. Seedless plants were present on the early Earth because at that time the plants did not have any packaging system to cover and protect their seeds. They were dominant in the late Silurian period, that is about 427 million years ago. When the plants evolved they developed mechanisms to protect their embryo inside a seed covering. Hence, option (b) is correct.

Explanation for the incorrect answers:

Option (a) is developing vascular tissues. The plants that were present on the early Earth belonged to the clade bryophytes, which did not have any elaborate vascular systems. With the evolution of the plants, they developed a vascular system in order to transport the sugars and water synthesized during photosynthesis. So, it is an incorrect option.

Option (c) is having a dominant diploid generation. In early plants, that lived underwater, the life of haploid gametophyte was long. When the plants adapted to terrestrial life, the life of the diploid sporophyte became longer as compared to the haploid gametophyte. So, it is an incorrect option.

Option (d) is producing non-motile gametes. Due to the absence of water on land, the plants found other methods to transport their gametes, without the help of water. Some plants have very beautiful flowers that attract bees, birds, and other animals, which help in the dispersal of seeds and in return they get nectar and other rewards. Some plants have very light pollens, which are transferred with the help of wind. So, it is an incorrect option.

Option (e) is producing two types of spores. The vascular plants developed as a result of evolution. They have two types of spores that are male and female spores. These plants are called heterosporous. The male gametes are called pollens and the female gametes are called eggs. So, it is an incorrect option.

Hence, options (a), (c), (d), and (e) are incorrect

Conclusion

Thus, it can be concluded that as plants evolved, they developed a mechanism to protect their embryo in the form of seeds, became vascular and heterosporous. The plants also developed non-motile gametes and dominant diploid sporophyte.