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700 million years ago
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Plants first appeared on land approximately 700 million years ago. The increased oxygen in the atmosphere helped facilitate new life and evolution.
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Most plant life cosisted of small, soft, marine plants, such as green algae. When terrestrial plants evolved, they cooled the climate and provided oxygen for new life to begin on land.
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Because the earliest plants were non-vascular, they did not conduct water. Terrestrial plants primarily lived in wet enviroments. These plants reproduced by spores.
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The first vascular plants evolved. Most Silurian plants showed no differentiation of leaves, stem, and roots. Allowed plants to draw water through their structures.
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The first recognizable soils developed. Plants developed sexual organs for reproduction, stems with vascular tissue, woody tissue for structure, and stomates for respiration.
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Seed plants developed and colonized habitats where spore-producing plants couldn't flourish.
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The climate dried, which led to the evolution of advanced conifers. Cycads and ginkgos became present. There was widespread forestation in some regions.
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Sead-bearing plants dominated. Gymnosperms where the most prevalent plant.
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The climate became wetter, which developed large jungles. Conifers dominated the landscape. Flowering plants played a minor role in this period.
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Angiosperms developed and became the dominant plants. Modern-day trees appeared. Conifers continued to be pertinant trees in cold regions. Ancestors of modern-day ferms evolved during this period.
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Grasses evolved to develop the savanna ecosystem. This provided food for large grazing mammals and protection for small animals. Conifers dominated cold climates and angiosperms dominated tropical climates.
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As the climate cooled, large forests died off. Grasslands thrived because of their adaptability to dry conditions.
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The earliest agriculture consisted of cultivating grass-type plants (wheat, grain, barley. Later, humans learned to cultivate corn, squash, beans, rice, and millet.