Plants Objective Students will be able to Describe the characteristics of plants An Overview of Plants Plants Between 260,000 and 300,000 different species Have adapted to almost every environment An Overview of Plants Plants have some general characteristics: Roots or root-like structures Can perform photosynthesis Has cells that are different from those of other organisms An Overview of Plants Plant cells Cell walls, which provide structure and protection. Green pigment chlorophyll Central vacuole, which regulates water content. An Overview of Plants Earliest plants were probably green algae, dating back to 420 m.y.a. Cone-bearing plants show up around 300 m.y.a. Flowerings plants came into existence around 120 m.y.a. An Overview of Plants An Overview of Plants Scientists think plants probably evolved from green algae in the sea because: Plants and green algae have the same types of chlorophyll and carotenoids. Fossils of early plants are similar to the ancient green algae. An Overview of Plants When plants moved to land, they had to adapt to new conditions. More sunlight and carbon dioxide were available. Plants developed a cuticle—a waxy, protective layer secreted onto the surface of the plant which holds water in and allows plants to live in drier conditions. An Overview of Plants When plants moved to land, they had to adapt to new conditions. Cell walls developed cellulose, a chemical compound that provides structure and support, which allows plants to stand upright on land. Water-resistant spores and seeds enabled plants to reproduce on land. An Overview of Plants Plant classification Vascular plants use tube-like structures that carry water and nutrients throughout the plant. Nonvascular plants lack tube-like structures and use other ways to move water and nutrients. Objective Students will be able to: Identify seedless plants Distinguish between vascular and nonvascular seedless plants Explain a pioneer species Explain how humans use seedless plants Seedless Plants Nonvascular plants Very small plants that have rhizoids rather than roots Seedless Vascular plants Reproduce by spores, but have vascular tissue that carries water and nutrients throughout the plant Nonvascular plants Water is absorbed and distributed directly through cell membranes and cell walls. Grow in damp environments Reproduce by spores rather than seeds Nonvascular plants Examples of nonvascular plants: Mosses - green, leaflike growths arranged around a central stalk Nonvascular plants Examples of nonvascular plants: Liverworts flattened, leaflike bodies Nonvascular plants Examples of nonvascular plants: Hornworts - have only one chloroplast in each of their cells Nonvascular plants Pioneer species Organisms that are the first to grow in new or disturbed areas and which change environmental conditions Seedless Vascular plants Reproduce by spores, but have vascular tissue that carries water and nutrients throughout the plant Can grow bigger and thicker than nonvascular plants Seedless Vascular plants Examples of seedless vascular plants Ferns - largest group of seedless vascular plants Have stems, leaves, and roots Leaves are called fronds Reproduce by spores found on the back of their fronds Seedless Vascular plants Examples of seedless vascular plants Club mosses - needlelike leaves Seedless Vascular plants Examples of seedless vascular plants Horsetails - jointed stem with a hollow center Seedless plants Seedless plants are important because they have many useful purposes Fuel—decaying seedless plants are compressed into peat and eventually coal Soil conditioners Ferns can be used for weaving material and basketry. Objective Students will be able to: Describe the characteristics of a seed plant Describe the anatomy of a seed plant Distinguish between gymnosperms and angiosperms Compare and contrast monocots and dicots Explain how humans use seed plants Seed Plants Have leaves, stems, roots, and vascular tissue Reproduce by seeds, which contain an embryo and stored food Seed Plants Leaves Trap light and make food through photosynthesis. Seed Plants Leaves Epidermis - a thin layer of cells on the upper and lower surfaces of a leaf May have a waxy cuticle coating the epidermis Stomata—small openings in the epidermis that allow carbon dioxide, water, and oxygen to enter and exit a leaf Each stoma is surrounded by two guard cells that open and close it. Seed Plants Leaves Palisade layer contains chloroplasts, where most food is made Spongy layer loosely arranged cells and air Seed Plants Stems allow the movement of materials between leaves and roots. Usually above ground Support the branches, leaves, and flowers May store food Seed Plants Stems: Herbaceous stems—soft and green Woody stems—hard, rigid, and woody Seed Plants Roots Roots collect water and nutrients from the ground. Roots anchor plants so they don’t blow away. May store food or water. Seed Plants Vascular tissue Xylem tissue—transports water from the roots throughout the plant Phloem tissue—moves food from where it is made to other parts of the plant Cambium tissue—produces new xylem and phloem cells Seed Plants There are two kinds of seed plants Gymnosperms Angiosperms Gymnosperms Vascular plants that produce seeds that are not protected by fruit Oldest trees alive Gymnosperms have no flowers. Leaves are often needlelike or scalelike Gymnosperms Four divisions: Conifers Cycads Ginkgoes Gnetophytes Gymnosperms Conifers Cone-bearing, reproducing because of male and female cones Woody Most are trees, some are shrubs First trees on earth Gymnosperms Conifers are the oldest living things on earth Left: oldest tree is a bristle-cone pine, the Methuselah tree is 4,839 years old Right: Newly discovered in Sweden, this spruce has a root system that is 9,600 years old. Gymnosperms Conifers are the oldest living things on earth NOVA Online | Methuselah Tree Gymnosperms Conifers are the tallest living things on earth Hyperion is the newly discovered sequoia that is 379.1 feet tall, beating out the Stratospheric Giant at 370.5 feet. Gymnosperms Conifers are the widest living things on earth Left: the General Sherman Redwood at 102 ft. around Right: The Tree at Santa Maria del Tule, a Montezuma Cypress at 164 ft. in circumference Gymnosperms Conifers are the widest living things on earth This is known as the “Tree of a hundred horses.” At 204 ft around it was the widest tree ever measured It now grows in three pieces Angiosperms Vascular plants that flower and have fruit that contains seeds Fruit develops from flowers. Most fruit contains seeds. Angiosperms Two groups: Monocots One cotyledon in seed Vascular bundles scatteres Flower parts in multiples of three Parallel veins on leaves Angiosperms Two groups: Dicots Two cotyledons inside their seeds Vascular bundles in rings Flower parts in multiples of four or five Branching veins Angiosperms Different angiosperms have different life cycles: Annual - the plant’s life cycle is completed within one year Biennial - the plant’s life cycle is completed in two years Perennial - takes more than two years to grow to maturity Seed Plants Seed plants are very important because they have useful purposes Wood for construction Paper products. Angiosperms form the basis of diets for most animals, including humans.