Plants

Overview of PLANTS Chapter 22

Overview of Plants The plant kingdom’s impact on our lives cannot be overstated. A broad understanding of plants as organisms – their anatomy, physiology, evolution, and diversity – is required for a complete understanding of biology. Life on earth would not be possible without plants converting solar energy to chemical energy by photosynthesis. p. 518 chapter 23

The Evolution of Plants Before plants were able to live in terrestrial habitats, they needed ways to absorb minerals, conserve water, and reproduce on land. Vascular Tissue is the tissue that transfers water and other materials within the plant. The nonvascular plants, commonly referred to as bryophytes, represent the earliest stages in plant evolution. They are referred to as nonvascular because they either have no vascular system or have only very simple vascular tissue.

Nonvascular Plants or Bryophytes Do not have roots, stems or leaves Water and food move through the body of nonvascular plants by osmosis and diffusion (because they do not have a system of tubes or vessels) Characteristic = small, live in cool, wet environment Example = Liverworts, Hornworts and Mosses

The Evolution of Plants continued Many plants have vascular tissues that act as pipelines for carrying water from roots to leaves and for moving carbohydrates from leaves to roots.

Vascular Plants or Tracheophytes Have roots, stems and leaves Since they have conducting cells with reinforced walls, vascular plants are able to grow much larger than nonvascular plants. Developed a waxy, watertight covering called a cuticle to aid during drought

The Cuticle Covers the above ground parts of the plant. Prevents the tissues of the plant from drying out and losing water to the air. It is impermeable to water. It is impermeable to gasses required by plants for photosynthesis and cellular respiration. Passages through the cuticle, specialized pores called stomata, enable gas exchange in the plant. Guard cells control the opening and closing of the stomata by expanding and contracting.

The Evolution of Plants continued Plants exhibit a life cycle in which a haploid individual that produces gametes alternates with a diploid individual that produces spores. This is called Alternation of Generation. Gametophyte (n) Gametes Spores Meiosis Fertilization Sporophyte (2n)

The Evolution of Plants continued Plants exhibit a life cycle in which a haploid individual that produces gametes alternates with a diploid individual that produces spores. This is called Alternation of Generation. The first plants to invade land lacked roots, stems, and leaves. They took in water and other substances by osmosis and diffusion. Nonvascular plants, such as mosses, liverworts, and hornworts, have vascular tissue that is very simple in design. Modern vascular plants are distinguished by the following features: a dominant sporophyte, specialized conducting tissues, and a distinctive body form.

The Evolution of Seeds The first vascular plants, such as ferns, were seedless and required a film of water for fertilization.

The Evolution of Seeds The first seed-bearing plants were gymnosperms, which produced seeds that develop in cones.

The Evolution of Seeds Angiosperms are flowering plants, which produce seeds that develop within fruits.

The Evolution of Seeds A seed is a sporophyte plant embryo surrounded by a protective coat.

The Evolution of Flowers Angiosperms are the most successful plants, comprising 90 % of all living plant species. Flowers are reproductive structures that generally consist of four whorls of appendages. In many angiosperms, flower structure is suited for a particular type of pollination.

The typical angiosperm undergoes double fertilization, a process in which two sperm fuse with cells in the megagametophyte to produce both a zygote and endosperm. Angiosperms are classified as either monocots or dicots, depending on the number of cotyledons in their seeds. Fruits are specialized for seed dispersal by agents such as animals, wind, and water.

General Plant Characteristics Multicellular, eukaryotic, autotrophic (photosynthesis occurs in chlorophyll of chloroplasts) nonmotile (not mobile) Common Name Classifi-cation Vascular Tissue Structure Life Cycle Habitat Simple or Complex Plant Mosses, Liverworts Phylum Bryotphyta Absent No true roots, stems or leaves Gametophyte dominant sexual reproduction by fusion of sperm and egg Moist areas Simple Ferns Phylum Psilotophyta Present True roots, stems and leaves Sporophyte dominant, distinct, multicellular gametophyte Conifers Phylum Coniferophyta Sporophyte dominant, sexual reproduction in cones, seeds- Gymnosperms Wide spread Complex Flowering plants Phylum Anthophyta Sporophyte dominant, sexual reproduction in flowers, seeds- Angiosperms

Kingdom Plantae Seedless Seeds Gymnosperms Angiosperms ferns mosses club mosses dicots horsetails ginkgo cycads monocots whisk ferns conifers gnetophytes

Don’t forget to study for your Chapter __ “Overview of Plants” Quiz #1 When? THE FIRST OF NEXT CLASS