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What is a plant?. Unit 7 Chapter 20. Plant characteristics. Eukaryotic Multicellular Autotroph: food made through photosynthesis Cell walls made of cellulose Cuticle : waxy covering on plant body May have originated from green algae. Evidence for algal ancestry.
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What is a plant? Unit 7 Chapter 20
Plant characteristics • Eukaryotic • Multicellular • Autotroph: food made through photosynthesis • Cell walls made of cellulose • Cuticle: waxy covering on plant body • May have originated from green algae
Evidence for algal ancestry • Cellulose cell walls in algae and plants • Same types of chlorophyll for photosynthesis and stores sugar as starch • Fossil record dated 440 MYO showed plants without leaves
Adaptations to living on land • Algae are mostly found in water as they have no adaptations to prevent drying out on land. • Plants have structures that enable life on land. • Roots • Cuticle and waxy coats • Protection for gametes (sperm and egg)
Leaves • Plant organ that photosynthesizes • May occur in other plant parts with chlorophyll (ex: stems of cactus)
Roots • Absorbs water and minerals from soil • Helps to anchor plants to ground • May store sugar reserves (taproot)
Stem • Transports water and minerals from roots to branches and leaves • Transports sugar from leaves to storage organs • May store sugars and water (ex: sugar cane, cactus)
Xylem and phloem: specialized cells that transport sugar and water • Xylem and phloem make up vascular tissue • Supports plant life away from water source Xylem: water and minerals Phloem: sugar
Nonvascular plants: plants without xylem and phloem • Mosses, hornworts, liverworts
Nonvascular plants • Simple • Few cell layers thick • Doesn’t need vascular tissue to transport water and sugar because simple diffusion suffices
Reproduction without water • Algae require water to transport sperm to egg for fertilization. • Land plants store food with embryo within a protective coat. This forms the seed. • Seeds are easily dispersed and protected from the environment. Food supply Embryo Seed coat
Seedless plants • Sperm requires small water film to get to the egg. • Spores are formed instead of seeds.
Alternation of generation: plant life cycle Male gamete (n) Female gamete (n) Spores (n) Gametophyte (n) Meiosis Fertilization Sporophyte (2n) Mitosis and cell division
Club mosses: vascular, seedless • Ancient club mosses form the coal reserves found today
Ferns: vascular, seedless • Fronds: fern leaves with spores that grow underneath