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 Phloem: sugar Xylem: water and minerals

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. Embryo Food supply 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 Gametophyte (n) Sporophyte (2n) Spores (n) Meiosis Male gamete (n) Female gamete (n) Fertilization Mitosis and cell division

Survey of Plant Kingdom

Liverworts: nonvascular, seedless

Hornworts: nonvascular, seedless

Mosses: nonvascular, seedless

Whisk ferns: vascular, seedless

Club mosses: vascular, seedless Ancient club mosses form the coal reserves found today

Horsetails: vascular, seedless

Ferns: vascular, seedless Fronds: fern leaves with spores that grow underneath

Cycads: exposed seed, vascular

Ginkgos: exposed seed, vascular

Welwitschia: exposed seed, vascular

Conifers: exposed seed, vascular, bearing cones

Flowering plants: seeds within fruits, vascular