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What Is a Plant

This article explores the monumental adaptations of plants transitioning from aquatic to terrestrial life over 500 million years ago. It examines the evolution from simple green algae to complex land plants, detailing key adaptations such as the development of cuticles to prevent water loss, specialized leaves for photosynthesis, and roots for nutrient acquisition. The article also discusses plant structure, including vascular and non-vascular systems, and reproductive strategies involving seeds and spores, highlighting the diverse life cycles of gametophytes and sporophytes.

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What Is a Plant

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  1. What Is a Plant

  2. Adapting to Life On Land • First fossil evidence of plants – 500 million years ago. • Simple structures – no leaves. • Evolved from green algae.

  3. Adaptations: Preventing Water Loss • Cuticle: protective waxy layer around fruits, leaves, and stems. • Prevents evaporation of water.

  4. Adaptations:Leaves for Photosynthesis • In filamentous green algae, all cells carry out photosynthesis. • In plants leaves are specialized to make sugar.

  5. Adaptations:Roots • Plants must get water and nutrients from soil. • Anchor plant in ground. • Some act as storage organs.

  6. Transporting Materials • Water must move from root to leaves. • Sugars must move from leaves to roots. • Stem: strong fibers allow upright growth. • Also have tissues for transport of food, water, and minerals. • Vascular tissues – tube like cells. • Some plants are nonvascular: mosses, hornworts and liverworts. • Water and nutrients move slowly by osmosis and diffusion.

  7. Reproductive Strategies • Some use seeds: • Embryo, food supply, protective coat. • Protect from drying and aid in dispersal. • Some use spores: • Single haploid cell with hard outer wall. • Non-seed plants(mosses and ferns): • Sperm swim through film of water to egg. • Seed plants (conifers and flowering): • Sperm (pollen) does not need to swim.

  8. Alternation of Generations • 2 stages: • Gametophyte (n)haploid – makes gametes. • Sporophyte (2n)diploid – makes spores by meiosis. (Spores are haploid). • Non-seed vascular plants (ferns): • Spores release directly into environment and grow into haploid gametophytes. • Seed plants: • Spores retained by parent plant and develop into gametophytes only a few cells in size.

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