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.

EmbryoFood 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