Ch 22-Intro. To Plants BIG IDEA: What are the 5 main groups of plants & how have 4 of these groups adapted to life on land?

22.1 What is a Plant? Kingdom- Plantae- Eukaryotes w/ cell walls containing cellulose that perform photosynthesis Need sunlight, gas exchange, water, and minerals to survive Leaves allow for max. sunlight absorption

Plants need Oxygen(O2) for cellular respiration and Carbon dioxide (CO2) for photosynthesis. They release O2 Evolved structures to prevent water loss and absorb water

Plants can be unicellular (like green algae) or multicellular (like a tree or shrub) Adapting to Life on Land Fossils tell us that ancestors of modern plants lived in water. Lacked leaves and roots, very small Over time evolution of plants onto land required adaptations to prevent water loss, make them better at storing water, and capable of reproducing without water.

Land plants created new ecosystems, allowing new species to evolve 5 major groups based on 4 features: Embryo formation Water-conducting (vascular) tissues Seeds Flowers

Plant Life Cycle Land plants alternate between a diploid (2n) and haploid (1n) phase- alternation of generations 2n-diploid phase: multicellular sporophyte, or spore-producing 1n-haploid phase: multicellular gametophyte, or gamete producing

Starts w/ sporophyte, which produces haploid spores through meiosis  2. grow into gametophytes  3. produce gametes (egg + sperm), which come together (fertilization)  4. produces diploid zygote, develops into sporophyte

22.2 Seedless Plants Green algae were the 1st plants. Evidence of their existence ~550 million years ago. - Characteristics: mostly aquatic in fresh and salt water, and some moist areas on land

Most green algae are unicellular w/ branching filaments Lack specialized tissues for water transport b/c it’s readily available in environment Life cycle can switch between 2n and 1n, but stay in whatever generation is suitable to their living conditions -Ex: Clamydomonas

Multicellular green algae: Some form colonies Examples: Volvox and Spirogyra

Mosses are classified as bryophytes. - Mosses have thin waxy coat to prevent water loss + root-like filaments- “Rhizoids” - Some of the 1st land plants - Lack vascular tissue (specialized structures to carry water)

Bryophytes have alternation of generations -Gametophyte is dominant generation -Depend on water for reproduction (to carry gametes)

Female reproductive structure: archegonia Male reproductive structure: antheridia -Sperm+egg= zygote in fertilization

Vascular tissue=tracheophytes ~420 million years ago vascular tissue developed -Allows for transport or water/nutrients+ grow tall Xylem transports water Phloem transports nutrients

Vascular tissue is in many non-seed bearing plants, and all seed-bearing plants Seedless (ex): fern. - Root structure: rhizomes Leaf- structure: fronds Abundant in wet habitats, don’t require much lighta

Fern life cycle: Dominant phase: 2n sporophyte -Fertilization requires water

22.3 Seed Plants Seed is a plant embryo and food supply in a protective covering How’d plants adapt to reproduce w/out water? - Reproductive process in cones or flowers, transfer of sperm by pollen, and embryo protection in seeds

Types of seed plants= gymnosperms (cone bearing) and angiosperms (flower bearing) Male gametophyte is in structure called pollen grain Carried by wind or animals to female Pollen + female reproductive structure= pollination

After fertilization zygote grows into sporophyte embryo. Seeds can survive extremes like cold, heat, and drought b/c of protective seed coat Grows into plants once conditions are right

Gymnosperm= “naked seed”, seeds are exposed on scales w/in cones. Male Female Gymnosperm= “naked seed”, seeds are exposed on scales w/in cones. Seed cones are larger than pollen cones. In gymnosperms, the direct transfer of pollen to the female cone allows fertilization to take place w/out water

22.4 Flowering Plants Flowering plants= angiosperms Ovaries surround and protect the seeds Angiosperms reproduce sexually by means of flowers. After fertilization, ovaries develop into fruits, that surround, protect, and help disperse seeds

Flowers provide an evolutionary advantage b/c they attract pollinators Flowers provide an evolutionary advantage b/c they attract pollinators. Pollination is more efficient than relying on wind Fruits provide an evolutionary advantage b/c they allow for seed dispersal Soooo… angiosperms are the most complex and evolved of the plants

Flowering plants are classified according to the # of seed leaves (cotyledons) in their embryos. Monocots produce 1 seed leaf. Dicots produce 2 seed leaves

Woody plants are made of cells w/ thick cell walls for support. Include trees, shrubs, and vines Herabceous plants are smooth and nonwoody. Don’t produce wood. - Include sunflowers, dandelions, and petunias