Chapter 22: Plants

What is a Plant? Plant  mostly multicellular organisms of eukaryotic cells with think cell walls and that mostly get energy through photosynthesis Autotrophs  produce their own energy (chlorophyll a and b in chloroplasts) Heterotrophs plants  gain energy from decomposing organic material

What do Plants need to survive? Reactants of photosynthesis: – Sunlight, CO 2, Water Gas Exchange: – Take in CO 2 but also release O 2 (byproduct that can limit photosynthesis) Minerals/Nutrients: – Absorbed from the soil through the roots Space: – Crowding limits sunlight which lowers photosynthesis rate – Photosynthesis is a very inefficient reaction, so a high rate is needed to survive

The Plant Kingdom 5 Groups based on Adaptations: 1)Green Algae  simplest plants; seedless 2)Bryophytes  complex plants but lack main plant structures; seedless 3)Seedless Vascular Plants  typical plants but seedless 4)Cone-Bearing  typical plants that produce seeds 5)Flowering  seed producing plants with flower adaptations

The Plant Life Cycle All plant groups follow alternation of generation life cycles Diploid (2N) Phase: – Sporophyte  multicellular phase that produces spores – Spores grow into gametophytes Haploid (N) Phase: – Gametophyte  multicellular phase that produces gametes (sperm and eggs) – Gametes fuse (fertilization) to make sporophyte

Green Algae Can be unicellular or multicellular (volvox) Haploid cells most of the time and reproduce by mitosis Haploid gametes can fuse to make diploid zygote that can be dormant for long periods of time – Survive unfavorable environment Must live in water or on moist land; nutrient rich soil

Bryophytes Multicellular plants but lack leaves, stems, and roots – Lack of vascular tubes means moss can only be 1 meter high Most common type is moss Rhizoids  simple root-like tubes that help absorb water and nutrients Most of its life is the gametophyte form and requires water to mix gametes – Must live on moist ground

Seedless Vascular Plants Club Moss, Horsetails, and Ferns Vascular tissue  hollow tubs inside the plant that allow the movement of water and nutrients – Xylem  moves water – Phloem  nutrients Rhizomes  underground root system Sporophyte releases spores which grow into heart-shaped gametophytes; sperm and eggs need water to mix

Cone-Bearing Plants Seed  plant embryo, energy supply, and protective coating (seed coat) – Allows spreading of plants away from water sources Gymnosperms  “naked seed”; sporophyte release pollen grains (male- gametophyte) from Pollen Cones – travel by wind to fertilize ovules (eggs) in Seed Cones (pollination)

Flowering Plants Must abundant plant forms Angiosperms  “enclosed seed”; flower contains ovaries and pollen (sperm) – After fertilization ovaries develop into fruit (contain seeds); animals eat fruit and spread seeds in droppings Flowers allow pollination by animals; much more efficient than wind Categorize plants by: – Soft or hard stems (wood) – Annual or biennial life cycles – # of cotyledons (seed leaves); monocots (one) or dicots (two) – Flower petals in multiples of 3, 4, or 5 – Vascular buddle formations – Types of leaves

Type of Flowering Plants 5 Classifications: 1)Amborella  oldest known angiosperms; only 1 species still exists 2)Water Lily  large, showy flowers 3)Magnoliids  wide range of flowers in both size and complexity 4)Monocots  20% of flowering plant species; includes rice, corn, wheat, orchids, lilies, and irises 5)Eudicots  75% of flowering plant species; very diverse class