BIOL120 Lecture Notes - Lecture 3: Chlorophyll, Selaginella, Lycopodiopsida
7 Jul 2016
School
Department
Course
Professor
Document Summary
Lignins strengthen cell walls by replacing water and coating or encrusting the cellulose. Allows for increase in size and height. In and near shallow freshwater lakes live organisms that seem to be both plantlike and algae-like. Vascular tissue, waxy epidermis, and other characteristics evolved in freshwater green algae in the class charophyceae, allowing them to survive periods when water dried up. Eventually able to complete entire life cycle on land, as long as water was available to enable sperm to swim to eggs. Adaptive radiation allowed species to occupy variety of land environments, and were the dominant plants for about 100 million years. Svp did not remain dominant in all environments because their method of fertilization depended on water, limiting their habitat and making them vulnerable to drought. Developing embryo needed moisture and were unprotected from animals: in contrast, ancient gymnospores could reproduce without freshwater because pollen tube delivered sperm to egg.
