Chapter 21: What is a Plant? 21.1: Adapting to Life on Land
Adaptation Cuticle Leaf Root Stem Vascular tissue Nonvascular tissue Vascular plant Nonvascular plant Seed Alternation of Generations Sporophyte Gametophyte Spore Diploid Haploid Section 21.1 Vocabulary
Multicellular Eukaryotic Photosynthetic Cell walls with cellulose What is a Plant?
Adaptations in Plants • For most land plants water must be absorbed from the soil to survive. • Land plants evolved structural and physiological adaptations that help protect the gametes from drying out. • Land plants must also withstand the forces of wind and weather and be able to grow against the force of gravity.
Most fruits, stems, and leaves are covered with a protective waxy layer call the cuticle which creates a barrier that prevents the water in the plant’s tissues from evaporating. Preventing Water Loss
Carrying Out Photosynthesis • The leafis a plant organ that grows from a stem and usually is where photosynthesis occurs • Leaves differ greatly in size and shape.
Because soil is a plants primary source of water plants can take in water and nutrients from the soil with their roots. A rootis a plant organ that absorbs water and minerals usually from soil. Putting Down Roots
Roots contain tissues that transport the nutrients to the stem. Some roots are used for storage. Putting Down Roots
Water moves from the roots of a tree to its leaves, and the sugars produced in the leaves move to the roots through a stem. A stemis a plant organ that provides support for growth. Transport Material
Transport Material • Stems contain tissues for transporting nutrients to different parts of the plant. • In green plants stems can contain chlorophyll and photosynthesize. • Most stems contain vascular tissuewhich are made up of tube like, elongated cells through which water, food, and other materials are transported. • Plants that possess vascular tissue are known as vascular plants. • Examples: pine and maple trees, ferns, English ivy, and sunflowers.
Mosses and several other small, less familiar plants called hornworts and liverworts are classified as nonvascular plants because they do not have vascular tissue. Transport Material
A seedis a plant organ that contains an embryo, along with a food supply, and is covered by a protective coat. A seed protects the embryo from drying out and also can aid in its dispersal. Reproductive Strategies
Reproductive Strategies • Land plants can reproduce by seed or spores. • In non-seed plants, which include mosses and ferns, the sperm require film of water on the gametophyte plant to reach the egg.
Reproductive Strategies • In seed-plants, which include all conifers and flowering plants, sperm reach the egg without using a film of water. • This explains why non-seed plants live in wetter habitats than most seed plants.
Alternation of Generations • The lives of plants include two stages, or alternating generations.
Alternation of Generations • The gametophytes generation of a plant results in the developments of gametes. • All cells of the gametophyte generation, including the gametes are haploid (n). • The sporophyte generation begins with fertilization. • All cells of the sporophyte are diploid (2n) and are produced by mitosis and cell division. • Spores are produced in the sporophyte body by meiosis and are therefore haploid (n).
Alternation of Generations • In non-seed plants such as ferns, spores have hard outer coverings • Spores are released into the environment where they can germinate into haploid gametophyte plants. • These plants produce male and female gametes. • After fertilization, a new sporophyte develops within a seed. • The seed eventually is released and the new sporophyte plant grows.
Alternation of Generations • Journal Drawing: • Draw the life cycle of plants • Use different colors to represent the gametophyte (haploid) generations and the sporophyte (diploid) generation. • Read the Problem-Solving Lab on pg. 563 and be prepared to discuss in class.
Evolution Frond Cone Hepaticophyta Anthocerophyta Bryophyta Psilophyta Lycophyta Arthrophyta Pterophyta Cycadophyta Gnetophyta Ginkophyta Coniferophyta Anthophyta Know examples for each phyla 21.2 Vocabulary
Phylogeny of Plants • Some botanists use plant characteristics to classify plants into divisions. • A plant division is similar to phylum in other kingdoms • The production of seeds can be used as a basis to separate the divisions into two groups: • Non-seed plants • Seed Plants
Non-Seed Plants • These plants produce hard-walled reproductive cells called spores. • Non-seed plants include vascular and nonvascular organisms
small plants commonly called liverworts flattened bodies nonvascular grow in moist environments water moves throughout the organism by osmosis and diffusions Hepaticophyta
There are two kinds of liverworts Thallose: broad body that looks like a lobed leaf Leafy: creeping plants with three rows of thin leaves Hepaticophyta
small thallos plants sporophytes resemble the horns of animals, which gives them their common name- hornworts grow in damp, shady habitats and rely on osmosis and diffusion to transport nutrients Anthocerophyta
mosses also rely on osmosis and diffusion to transport material some have elongated cells that conduct water and sugars usually less than 5 cm tall and have leaflike structures that are only one or two cells thick. spores formed in capsules Bryophyta
known as whisk ferns have thin, green stems vascular plants, but do not have roods or leaves small scales that are flat, rigid, overlapping structures cover each stem only one genus is found in the southern US Psliophyta
club mosses vascular plants found in moist environments have stem, roots, and leaves leaves are very small and contain vascular tissue usually less than 25 cm, but the ancestors grew as tall as 30m used as part of the coal that is now used by people for fuel Lycophyta
horsetails vascular have hollow jointed stems surrounded by whorls of scale like leaves primarily a fossil group, but there are about 15 species that exist today Arhrophyta
ferns most diverse non-seed vascular plants have leaves called fronds that vary in length from 1cm to 500cm found almost everywhere, but primarily in the tropics Pterophyta
Seed Plants • Produce seeds, which in dry environments are a more effective means of reproduction that spores. • Seeds consist of an embryo, food supply, and a hard protective seed coat. • All have vascular tissue
About 100 species of cycads Palm like trees with scaly trunks and can be short or more than 20 m Produce male and female cones on separate trees Cycadophyta
Cones: scaly structures that support male or female reproductive structures. Cycad cones can be as long as 1m Seeds are produce in female cones. Male cones produce clouds of pollen Cycadophyta
Three genera of gnetophytes Gnetum: 30 species of tropical trees and climbing vines Ephedra: 35 species that grow as shrubby plants in deserts and arid regions. Gnetophyta
Gnetopyta 3. Welwitschia: one spescies which is found in the deserts of southwest Africa. Its leaves grow from the base of a short stem that resmbles a large, shallow cap.
Ginkgophyta • One living species, Ginkgo biloba • Small fan-shaped leaves • Have male and female reproductive structures on different trees
The seeds produced on female trees have an unpleasant smell, so Ginkgos planted in parks are usually the male tree. Resistant to insects and air pollution Ginkgophyta
Conifers, cone-bearing trees such as pin, fir, cypress, and redwood Vascular seed plants that produce seeds in cones Identified by the characteristic of cones or leaves that are needle-like or scaly Coniferophyta
Coniferophyta • Bristlecone pines are the oldest known living trees in the world
Pacific yew is a source of cancer-fighting drugs. Coniferophyta
Anthophyta • Flowering plants • Largest and most diverse group of seed plants living on Earth • Approximately 250,000 species • Produce flowers form which fruits develop which usually contains one or more seeds • This division has two classes: • monocotyledons • dicotyledons