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Introduction to Plants Table of Contents The Plant Kingdom Photosynthesis and Light Mosses, Liverworts, and Hornworts Ferns, Club Mosses, and Horsetails • Introduction to Plants - The Plant Kingdom What Is a Plant? • Multicellular organisms with tissues and organs. • Contain chlorophyll inside chloroplasts and can make food. • Can not move from place to place. • Made of eukaryotic cells with cell walls. Introduction to Plants - The Plant Kingdom Plant Cell Structure Activity • Click the Active Art button to open a browser window and access Active Art about plant cell structure. Introduction to Plants Adaptations to Land • To move to land, plants had to develop adaptations to solve the following problems: – Prevent water loss – cell walls made of cellulose help prevent water loss. Most land plants also have a waxy covering called a cuticle on their stems and leaves that also aids in preventing water loss. – Obtain water and nutrients from soil – plants evolved roots. Introduction to Plants Adaptations to Land – Transport Materials —water moves up and food moves down through tube-like vascular tissue. – *Support their own weight—cell walls and vascular tissue provide structure and support. Stems and roots then evolved. – *Reproduction—the most successful land plants evolved ways to reproduce without water (seeds). Introduction to Plants - The Plant Kingdom Water Loss in Plants • The graph shows how much water a certain plant loses during the hours shown. Introduction to Plants - The Plant Kingdom Water Loss in Plants • Reading Graphs: –What variable is plotted along each axis? –Horizontal axis–time of day; vertical axis– water loss. Introduction to Plants - The Plant Kingdom Water Loss in Plants • Interpreting Data: –According to the graph, during what part of the day did the plant lose the most water? The least water? –Most–midday; least– in the evening. Introduction to Plants - The Plant Kingdom Water Loss in Plants • Drawing Conclusions: • What could account for the pattern of water loss shown? –The plant seemed to lose the most water during the sunniest or warmest parts of the day. Introduction to Plants - The Plant Kingdom Water Loss in Plants • Predicting: –How would you expect the graph to look from 10 p.m. to 8 a.m.? Explain your reasoning. –The line graph would descend during the night and rise again in the morning hours; water loss is less during the night when there is no sun. Introduction to Plants Origin of Plants • Evolved from one-celled, plant-like protists in the ocean (Green Algae) – Fossil record is sketchy because most plants decay before they form fossils. – Oldest plant fossils are about 400 million years old. They had no leaves and their stems grew underground. Introduction to Plants Photosynthesis • All plants make food through the process of photosynthesis. • During photosynthesis, plants use energy from sunlight to change carbon dioxide and water into sugar and oxygen. – 1. Sunlight or “white light” is made of all of the colors of the rainbow (the visible spectrum). – 2. Plants absorb most of these colors except green. Green light is reflected by the pigment known as chlorophyll. – 3. Other plant pigments reflect other colors and are called accessory pigments. We see them mostly in the fall, when plants stop making chlorophyll. Introduction to Plants - Photosynthesis and Light The Photosynthesis Process • In photosynthesis, the energy in sunlight is used to make sugar and oxygen from carbon dioxide and water. Introduction to Plants The Big Picture of Photosynthesis • Water enters through the roots of the plant. • Carbon dioxide enters through tiny openings in the leaves of the plant called stomata. • They travel to the chloroplasts where they are changed into a special sugar, called glucose, and oxygen. • Glucose is the plant’s food. It is broken down, just like our food, to give the plant energy to grow, develop, respond and reproduce. • Most of the oxygen is released also through the stomata of the leaves and used by other organisms. Introduction to Plants - Photosynthesis and Light The Photosynthesis Process Activity • Click the Active Art button to open a browser window and access Active Art about the photosynthesis process. Introduction to Plants The Photosynthesis Equation • The many chemical reactions of photosynthesis can be summarized by this equation: light energy carbon dioxide + water (6CO2) (6H2O) sugar + oxygen (C6H12O6) (6O2) Introduction to Plants - Photosynthesis and Light Photosynthesis • Click the Video button to watch a movie about photosynthesis. Introduction to Plants Classification of Plants • The Plant Kingdom is divided into nine divisions (not phyla). • The first division includes nonvascular plants. – Nonvascular plants have no vessels (vascular tissue) for transporting food and water. Therefore, they are all very small and grow in damp shady places. They include: – 1. Division Bryophyta —mosses, liverworts and hornworts Introduction to Plants Classification of Plants • The remaining eight divisions are all vascular plants. • Vascular plants have vessels (vascular tissue) to transport water and materials and help support the plant. Therefore they can grow very tall and are better suited to all land habitats. Some reproduce using spores and some use seeds. This chapter will look at the three divisions of seedless vascular plants. 1. Division Lycophyta —club mosses 2. Division Sphenophyta —horsetails 3. Division Pterophyta —ferns Introduction to Plants Division Bryophyta • Mosses are the most common type of bryophyte. – 10,000 different species • All are simple, rootless plants with leaf-like growths in a spiral around a stalk. • Root-like threads called rhizoids replace true roots and hold the moss in place. • Most range in size from 2-5cm in height. Introduction to Plants Division Bryophyta Liverworts—simple, rootless plants that have a flattened, leaf-like body. Their name means, “liver herb” and in the Middle Ages, people believed this plant looked like one’s liver. Introduction to Plants Division Bryophyta Hornworts—small plants with flat, round, leaf-like structures. It’s sporophyte looks like an animal’s horn. They live near lakes and rivers. Introduction to Plants Importance of Bryophytes • Bryophytes such as mosses and liverworts are often called pioneer plants because they are the first to grow in new or disturbed areas. • Nonvascular plants like them were also probably the first land plants to evolve millions of years ago. • Many people use peat moss from bogs in agriculture and gardening. Introduction to Plants - The Plant Kingdom Complex Life Cycles • Simple plants like mosses and other bryophytes have complex life cycles that include two different stages: the sporophyte stage and the gametophyte stage. Introduction to Plants - Mosses, Liverworts, and Hornworts Mosses • A moss gametophyte is the green leafy part of the plant and the rootlike rhizoids. There are separate male and female gametophytes. • The moss sporophyte is made of a stalk and a capsule. It grows from the zygote cell and will produce new spores that will grow into new gametophytes. Introduction to Plants Another look at the moss reproduction process. Introduction to Plants - Mosses, Liverworts, and Hornworts Links on Nonvascular Plants • Click the SciLinks button for links on • nonvascular plants. Introduction to Plants - Ferns, Club Mosses, and Horsetails Charact. of Seedless Vascular Plants • Ferns, club mosses, and horsetails also reproduce using spores not seeds. However, they have vascular tissue which means they can grow much taller. There are three divisions of seedless vascular plants. Introduction to Plants Division Lycophyta Division Lycophyta— also known as club moss. Produce spores in structures that look like tiny pinecones. Sometimes called ground pine. Introduction to Plants Division Sphenophyta Division Sphenophyta— also known as horsetails. Stems are jointed with a hollow center. They contain silica (a gritty substance found in sand). They were used by pioneers to scour their pots and pans. Introduction to Plants Division Pterophyta Division Pterophyta— includes all species of ferns. Largest group of seedless vascular plants. Ancient species were huge (25 meters). Today, the largest species are 3-5 meters. These ancient fern forests formed today’s coal deposits. Introduction to Plants - Ferns, Club Mosses, and Horsetails Characteristics of Ferns • Most ferns have underground stems in addition to roots. The leaves, or fronds, grow above ground. Introduction to Plants Fern Reproduction Ferns and other seedless vascular plants also reproduce using a sporophyte and a gametophyte generation. Fern sporophyte with spore cases called sori Fern gametophyte with young sporophyte beginning to grow Introduction to Plants Fern Life Cycle The sporophyte is the fern leaf or “frond”. On the underside of the frond are spore cases called sori. These release thousands of spores. A spore grows into a heart-shaped gametophyte called a prothallium. It is held in place by root-like structures called rhizoids and has both sperm and egg cells on it. They unite and a new sporophyte begins to grow. Introduction to Plants Wrap-up • Both mosses and ferns rely on water for reproduction because the sperm cells must swim to egg cells. Therefore, these plants live only in fairly moist areas. It wasn’t until plants evolved seeds for reproduction that they truly became successful in all land habitats. • Seed producing vascular plants include all other plants not discussed in this chapter. We will be studying them next. Introduction to Plants Graphic Organizer Characteristic Moss Fern Size Small and low Can be tall Environment Moist Moist Body parts Rootlike, stemlike, leaflike structures True roots, stems, and leaves Familiar generation Gametophyte Sporophyte Is true vascular tissue present? No Yes