Introduction to Plants! Mrs. Lambert Plants The Basics • Multicellular • Eukaryotes • Cell walls made of cellulose • Autotrophs An Early Scientist described plants as, “Stationary animals that eat sunlight.” Life Cycle • Plants have a life cycle that is characterized by alternation of generations. • Two generations: – Gametophyte – plant that produces haploid gametes (N). • Gametes – eggs and sperm that fuse to produce diploid individual. – Sporophyte – plant that produces diploid spores (2N). • Spores – reproductive cells that produce a new individual by mitosis. • All plants have gametophyte stage and sporophyte stage. The lives of plants revolve around: 1. The need for sunlight, water and minerals. – 2. Plants use water quickly when the sun is shining. Gas Exchange • 3. Plants require oxygen to support respiration as well as carbon dioxide for photosynthesis. Movement of water and minerals. • Plants take up water and minerals through their roots but make food in their leaves. Early Plants • Early plants lived in the water. • When they moved to land, they changed the environment in ways that made it possible for other organisms to develop. • Early plants probably looked like multicellular green algae. Plants are divided into two categories: • Bryophytes – Non-vascular plants. – No tissue to transport water and nutrients throughout the plant. • Tracheophytes – Vascular plants. – Tissue to transport water and nutrients. Bryophytes • Three divisions: – Mosses – Liverworts – Hornworts • The simplest plants – no tissue to transport water and nutrients. – No true roots, stems, or leaves. Mosses • The most common bryophytes. • Live in wet habitats – swamps, bogs, streams. • Can tolerate very low temperatures. – Most abundant plants in polar region. • Leaves of mosses are only one cell thick. • Must be close to water – found in moist shaded environments. – Size is limited. • Anchored to the ground by filaments called rhizoids. • Obtain water and nutrients by absorbing them directly into plant cells. – Water seeps from one cell to the next. Reproduction in bryophytes • Reproduce with alternation of generations. • Gametophyte is dominant stage of life cycle. • Sperm must swim to egg. – Bryophytes must live in areas where water is available. Tracheophytes • Contain vascular tissue. – Xylem – carries water upward from roots to every part of the plant. • Tracheids – hollow cells with thick walls that resist pressure. – Phloem – transports solutions of nutrients and carbohydrates produced by photosynthesis downward from leaves to the roots. • Produce lignin – a substance that makes cell walls rigid. • Because of xylem, phloem and lignin, Tracheophytes can grow upright to reach great heights. Tracheophytes are divided into two main groups • Seedless plants – Club moss, horsetails and fern • Seed plants – Gymnosperms – Angiosperms Seedless plants - ferns Seedless plants - ferns • Have roots, stems and leaves. – Roots – underground organs that absorb water and minerals. – Leaves – photosynthetic organs that contains vascular tissue gathered into veins of xylem and phloem. • The leaves of ferns are called fronds. – Stems – supporting structures that connect roots and leaves, carrying water and nutrients. Life Cycle of the Fern • In ferns and other vascular plants, the diploid sporophyte is the dominant stage. • Fern sporophytes produce haploid spores on the underside of their fronds in tiny containers called sporangia. • Sporangia are grouped in clusters called sori. • The spores germinate and develop into haploid gametophytes. • Small heart-shaped plants that grow independently of the sporophyte. • On the underside of the gametophyte: – Antheridia – where sperm are produced. – Archegonia – where eggs are produced. • Fertilization requires a thin film of water, allowing the sperm to swim to the eggs. • The diploid zygote produced by fertilization grows into a new sporophyte plant. • Sporophyte fronds may die in the winter, but rhizomes live through the winter and sprout again in the spring. Life cycle of fern Seed Plants • The dominant group of photosynthetic organisms on land. Seed Plants are divided into two groups: • Gymnosperms – bear seeds on the surface of cones. – Conifers such as pines and spruces. – Ancient ginkgoes. Angiosperms • Flowering plants that bear seeds within a layer of tissue that protects the seed. • Include grass, flowering trees and shrubs, all flowers. Reproduction in seed plants: • Seed plants do not require water for fertilization of gametes. • Adaptations that allow this: – Flowers or cones. – The transfer of sperm by pollination. – The protection of embryos in seeds. Cones and Flowers • Gametophytes of seed plants grow and develop in two types of sporophyte structures: – Cones – seed bearing structures of gymnosperms. – Flowers – seed bearing structures of angiosperms. Pollen • In seed plants, the male gametophyte is contained in a pollen grain. • The pollen grain is carried to the female gametophyte by wind, insects, birds, or small animals. • The female gametophyte is located in the ovary of the flower. This transfer is called pollination. Seeds • After fertilization, the zygote develops into a tiny plant called an embryo. • A seed is an embryo of a plant that is encased in a protective covering and surrounded by a food supply. – Embryo – the early developmental stage of the sporophyte plant. – Seed coat – surrounds and protects the embryo. • The embryo can remain within the seed for years. Gymnosperms • Include gnetophytes, cycads, ginkgoes and conifers. Ginkgoes • Belong to phylum Ginkgophyta. • Only one species: Ginkgo biloba. • Common when dinosaurs were alive. • One of the oldest seed plant species alive today. Conifers • Belong to phylum Coniferophyta. • Includes pines, spruces, firs, cedars, sequoias, redwoods and yews. • Some can live for more than 4,000 years. • Most conifers are evergreens. Some redwoods can grow more than 300 feet tall. Tallest is 397.1 feet tall! Angiosperms – Flowering Plants • Angiosperms have unique reproductive organs known as flowers. – The vast majority of living plant species. – 235,000 species. . • Flowers attract animals such as bees or hummingbirds, which transport pollen from flower to flower. – Much more efficient than wind pollination used by gymnosperms • Flowers contain ovaries, which surround and protect the seeds. • After pollination, the ovary develops into a fruit. – A thick wall of tissue surrounding the seed. – Fruit protects the seed and aids in its dispersal. – Animals eat fruit and the seeds leave the digestive system ready to sprout. • The animal disperses the seed when it travels. • Plants use fruit to attract animals and increase the range of their habitat. Diversity in Angiosperms • Incredibly diverse with many different categories. • Monocots and dicots. • Woody and herbaceous plants. • Annuals, biennials and perennials. • These categories overlap! Two groups of angiosperms • Named for the number of seed leaves or cotyledons in the plant embryo. • Monocots and dicots. Monocots • • • • One seed leaf or cotyledon. Leaves: Parallel veins. Floral parts in multiples of 3. Stems: Vascular bundles scattered throughout stem. • Fibrous roots. • Corn, wheat, lilies, orchids and palms. Dicots • • • • Two cotyledons. Leaves: Branched veins. Floral parts in multiples of 4 or 5. Stems: Vascular bundles arranged in a ring. • Taproot. • Roses, clover, tomatoes, oaks and daisies. Monocots have fibrous roots, dicots have taproots Woody and Herbaceous Plants • Woody plants – made of cells with thick cell walls that support the cell body. – Trees, shrubs and vines. • Herbaceous plants – do not produce wood as they grow. – Dandelions and sunflowers. Classification of Angiosperms based on life span: • Annuals – complete life cycle within one growing season. • Petunias, pansies, cucumbers. Biennials • Complete life cycle within two growing seasons. • Parsley and celery. • Foxglove and Prince William. Perennials • Plants that live for more than two years. – Grass, asparagus, maple trees.