These first land plants evolved from the green algae, with which they share a number of traits. All store energy reserves, as starch, inside plastids. Their cell wall is built of cellulose microfibrils and the photosynthetic pigments are chlorophylls a and b, plus b-carotene.
The owe their success to the evolution of the flower. The flower's pollen and nectar encourage pollinating animals to visit, increasing the odds of fertilisation by ensuring that pollen is transferred efficiently from flower to flower. (The flowers of wind-pollinated angiosperms, e.g. grasses, are very much reduced in terms of size and complexity.) After fertilisation the carpel and other parts of the flower are used to form fruit that aid dispersal of the seeds inside the fruit. In addition, the xylem of angiosperms allow very rapid movement of water through the plant. This means that flowering plants can keep their stomata open through much of the day, achieving higher photosynthetic rates than gymnosperms; this "spare" photosynthetic capacity can support the development of fruit.
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In small plants such as single-celled algae, simple diffusion suffices to distribute water and nutrients throughout the organism. However, for plants to evolve larger forms, the evolution of vascular tissue for the distribution of water and solutes was a prerequisite. The vascular system contains xylem and phloem tissues. Xylem conducts water and minerals absorbed from the soil up to the shoot, while phloem transports food derived from photosynthesis throughout the entire plant. A root system evolved to take up water and minerals from the soil, and to anchor the increasingly taller shoot in the soil.
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-Vascular plants release oxygen into the air for the use of other organisms through the process of photosynthesis.
- Vascular plants, such as ferns prevent soil erosion, promote topsoil formation, restore nitrogen to aquatic habitats by harboring cyanobacteria, make good house plants, and have been used as food and for medicinal remedies.
INTRODUCTION: THE NATURE OF SCIENCE AND BIOLOGY
The earliest photosynthetic organisms on land would have resembled modern algae, cyanobacteria, and lichens, followed by bryophytes (liverworts & mosses, which evolved from the group of green algae). Bryophytes are described as seedless, nonvascular plants. Their lack of tissue for transport of water and nutrients limits their size (most are between 2 and 20 cm high). Bryophytes don't have typical stems, leaves, or roots, but are anchored to the ground by rhizoids. They can grow in a wide range of environments and are : when the environment dries so does the plant, remaining dormant while dry but recovering rapidly when wetted. These features make them important pioneer species.
INTRODUCTION: THE NATURE OF SCIENCE AND BIOLOGY ..
Cyanobacteria have a close evolutionary relationship with eukaryotes. They have the same photosynthetic pigments as the chloroplasts of algae and land plants. Chloroplasts are the right size to be descended from bacteria, reproduce in the same manner, by binary fission, and have their own genome in the form of a single circular DNA molecule. The enzymes and transport systems found on the folded inner membranes of chloroplasts are similar to those found on the cell membranes of modern cyanobacteria, as are their ribosomes. These similarities between cyanobacteria and chloroplasts suggest an evolutionary link between the two, and can be explained by the theory of .
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Accompanying the prominence of the sporophyte and the development of vascular tissue, the appearance of true leaves improved their photosynthetic efficiency. Leaves capture more sunlight with their increased surface area by employing more chloroplasts to trap light energy and convert it to chemical energy, which is then used to fix atmospheric carbon dioxide into carbohydrates. The carbohydrates are exported to the rest of the plant by the conductive cells of phloem tissue.