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• Why plants are important • http://www.enviroexplorers.com/wildflowers/importance_of_plants _and_plant_c.htm • Cool plant Facts: • http://hubpages.com/hub/plantfacts • http://www.youtube.com/watch?v=igkjcuw_n_U • http://www.youtube.com/watch?v=fc50QniIzVM • Pretest • The World of Plants (15 minutes) Plant Diversity Chapter 22 Miller & Levine Text Biology 112 Introduction to Plants (Chapter 22) Plants… • Provide the base for food chain on land • Provide shade, shelter and oxygen for all animals • Oldest fossil evidence of plants dates from about 470 million years ago! What is the name of the science of studying plants?? Botany Kingdom Plantae • Multicellular • Eukaryotic • Carry out photosynthesis using green pigments called chlorophyll • Include trees, shrubs, grasses, mosses and ferns • Most are autotrophs • Cell Walls made of cellulose What do Plants Need? 1. 2. 3. 4. Sunlight Water & Minerals Gas Exchange Movement of Water and Nutrients Plant Life Cycle • Two alternating phases, a diploid (2N) phase called the sporophyte generation and a haploid (N) known as gametophyte generation • These alternating phases are known as “alternation of generations” Early Plants • For most of Earth’s history plants did not exist. Life was concentrated in oceans, lakes and streams…Oxygen came from algae and cyanobacteria • The first plants evolved from an organism much like the multicellular green algae living today. Overview of the Plant Kingdom Botanists divide the plant kingdom into 4 groups based on three important features: 1. Water-conducting tissues 2. Seeds 3. Flowers Water-Conducting Tissues • Evolved as an adaptation to land • Absence – no xylem or phloem • Presence of tissue: – Xylem • Carries water and nutrients that enter the plant in the roots up through the stem and out to all parts of the leaves – Phloem • Parallel to the xylem • Carries sugar (energy) produced in leaves (site of photosynthesis) to all parts of the plant Types of Plants Cone-bearing plants 760 species (gymnosperms) Ferns & Relatives 11,000 species Mosses & Relatives 15,600 species 235,000 Flowering Plants (Angiosperms) Bryophytes (Non-Vascular) No Xylem or Phloem • Confined to moist habitats b/c they need water for sexual reproduction – Do not flower so no seeds – They produce spores • Commonly found in wetlands, rain forests, and roadside ditches • Generally less than 20cm tall • 3 classes: mosses, liverworts, and hornworts Liverwort Mosses Hornwort Bryophytes • Have leaflike, stemlike and rootlike organs • Have rhizoids (fine-like roots) that anchor the plant • Water and nutrients move from cell to cell by osmosis / diffusion • Mosses are the most common and they hold a lot of water – this sponge like feature makes them useful in oil spills, and potting soils Seedless Vascular Plants (Ferns & Relatives) • Dominant land plant 300 million years ago • Most are now extinct Seed Plants (Vascular) • Divided into two groups – Gymnosperms (naked seed) – Angiosperms (covered seed) • What makes them different? – Seed type is the main criterion for distinguishing the two major seed-bearing groups; gymnosperms and angiosperms – Greek: sperma “seed”, gymnos “naked”, and angeion “vessel” • Why are they successful? – Reproductive Adaptations and an improved vascular system largely account for the success of seed plants – The most widely distributed and complex group of plants on Earth – 270 000 known seed plants – Have separate male and female gametophytes, as well as roots, stems and leaves. Seed Plants - Gymnosperms • The most ancient surviving seed plants are the gymnosperms • Seeds are often found in a cone • Represent all seed plants that DO NOT form flowers (therefore do not have seeds enclosed within a fruit) • The most numerous and widespread are the conifers Gymnosperms: Conifers • Cone bearing woody trees and shrubs • Leaves are usually needlelike • Most are evergreen (don’t drop their leaves in the Autumn) • Conifers DO shed their needles, just not all at once – usually 2 to 4 years • Grow in many different environments • 600 species (pine, fir, spruce, cedar, hemlock, sequoias) • Produce useful products, ie. lumber/paper Seed Plants – Angiosperms (Flowering Plants) • There are thousands of different kinds of flowering plants • They range from tiny pond-surface plants, which are less than 1 mm long to trees 100 m tall. • Angiosperms ALL produce seeds in reproductive structures called flowers. Then, as the seeds mature, the flower changes into a fruit. • Angiosperms produce seeds that are enclosed and protected inside the fruit, which is formed by the flower. • Mature seeds are scattered, or dispersed, along with the fruit