Question

Give reason. A liverwort is unable to complete its life cycle in a dry environment.

Answer 1

Amphibians are organisms that need both land and water to complete their life cycle. Liverworts and other bryophytes are also known as amphibians of the plant kingdom.

Complete answer:
Liverworts are part of the bryophytes groups which are intermediary between completely aquatic plants (algae) and higher terrestrial plants. The typical bryophytes features include
- Small size
- Either a flat, plate-like structure that grows on damp soil and rocks or leafy structures that grow on tree trunks during the moist seasons.
- The primary life stage is gametophyte (haploid).

Despite their terrestrial habitats, the liverworts are not truly land-dwelling plants due to their dependence on water for completion of their life cycle. During the fertilization stage, the liverworts require aqueous media for transferring the sperm from the male organ (antheridium) to fertilize the eggs retained inside the female organ of the archegonium. The fusion leads to the formation of sporophyte that matures and ruptures to release spores that grow into an adult gametophyte. Without the presence of water, however, the fertilization cannot take place and life cycle cannot be completed.

Additional information:
The most ancient remains of liverworts appear in the form of fossilized spores from rocks in Argentina, dating back to 473 million and 471 million years ago. These provide the earliest evidence of terrestrial colonization by plants.

Note: Due to the vital role of water played in the fertilization of liverworts, they can be only found in tropics or regions with warm and wet climates. There are over 9000 documented species of liverworts, more commonly found in areas with deep to moderate shade.