![]() ![]() Four major adaptations contribute to the success of terrestrial plants. The most successful adaptation solution was the development of new structures that gave plants the advantage when colonizing new and dry environments. These plants, like cacti, minimize the loss of water to such an extent they can survive in extremely dry environments. Later, plants moved away from moist or aquatic environments using resistance to desiccation, rather than tolerance. Ferns, which are considered an early lineage of plants, thrive in damp and cool places such as the understory of temperate forests. Another strategy is to colonize environments with high humidity, where droughts are uncommon. Many mosses, for example, can dry out to a brown and brittle mat, but as soon as rain or a flood makes water available, mosses will absorb it and are restored to their healthy green appearance. One of these strategies is called tolerance. In turn, plants developed strategies to deter predation: from spines and thorns to toxic chemicals.Įarly land plants, like the early land animals, did not live very far from an abundant source of water and developed survival strategies to combat dryness. This situation changed as animals emerged from the water and fed on the abundant sources of nutrients in the established flora. Third, land plants evolved before land animals therefore, until dry land was colonized by animals, no predators threatened plant life. ![]() Second, carbon dioxide is more readily available in air than in water, since it diffuses faster in air. Water acts as a filter, altering the spectral quality of light absorbed by the photosynthetic pigment chlorophyll. To balance these survival challenges, life on land offers several advantages. Some species never moved very far from the aquatic environment, whereas others went on to conquer the driest environments on Earth. The successful land plants developed strategies to deal with all of these challenges. ![]() Therefore, both gametes and zygotes must be protected from desiccation. Additionally, the male gametes must reach the female gametes using new strategies, because swimming is no longer possible. The organism is also subject to bombardment by mutagenic radiation, because air does not filter out ultraviolet rays of sunlight. On land, plants need to develop structural support in a medium that does not give the same lift as water. Water also provides buoyancy to organisms. Even when parts of a plant are close to a source of water, the aerial structures are likely to dry out. Desiccation, or drying out, is a constant danger for an organism exposed to air. Water has been described as “the stuff of life.” The cell’s interior is a thick soup: in this medium, most small molecules dissolve and diffuse, and the majority of the chemical reactions of metabolism take place. Plant Adaptations to Life on LandĪs organisms adapted to life on land, they had to contend with several challenges in the terrestrial environment. Go to this article to get a more in-depth view of the Charophytes. Charophytes also share other features with the land plants. The common ancestor of Charophytes and land plants excludes the other members of the Archaeplastida. Scientists who solely track evolutionary straight lines (that is, monophyly), consider only the Charophytes as plants. These latecomers to photosynthesis are parallels to the Archaeplastida in terms of autotrophy, but they did not expand to the same extent as the Archaeplastida, nor did they colonize the land. In contrast, algae outside of the Archaeplastida, e.g., the brown and golden algae of the stramenopiles, and so on-all became photosynthetic by secondary, or even tertiary, endosymbiotic events that is, they engulfed cells that already contained an endosymbiotic cyanobacterium. Their evolutionary trajectory was relatively straight and monophyletic. That algal line evolved into the red and green algae, and eventually into the modern mosses, ferns, gymnosperms, and angiosperms. The ancestors to the Archaeplastida became photosynthetic by forming an endosymbiotic relationship with a green, photosynthetic bacterium about 1.65 billion years ago. While all algae are photosynthetic-that is, they contain some form of a chloroplast-they didn’t all become photosynthetic via the same path. These divergent opinions are related to the different evolutionary paths to photosynthesis selected for in different types of algae. Still others include only the Charophytes among the plants. Some scientists consider all algae to be plants, while others assert that only the green algae belong in the kingdom Plantae. Algae and Evolutionary Paths to Photosynthesis
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