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General Biology II: Chapter 21 Evolution of Plants

by: Juliet Villegas

General Biology II: Chapter 21 Evolution of Plants AS.020.152

Marketplace > Johns Hopkins University > Biology > AS.020.152 > General Biology II Chapter 21 Evolution of Plants
Juliet Villegas
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General Biology II: Whole Chapter 21 Evolution of Plants
General Biology II
Rebecca Pearlman
Class Notes
General Biology II, Chapter 21, Evolution of Plants




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This 4 page Class Notes was uploaded by Juliet Villegas on Sunday February 28, 2016. The Class Notes belongs to AS.020.152 at Johns Hopkins University taught by Rebecca Pearlman in Spring 2016. Since its upload, it has received 187 views. For similar materials see General Biology II in Biology at Johns Hopkins University.


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Date Created: 02/28/16
Chapter 21 The Evolution of Plants: • Primary Endosymbiosis Produced the First Photosynthetic Eukaryotes • Key Adaptations Permitted Plants to Colonize Land • Vascular Tissues Led to Rapid Diversification of Land Plants • Seeds Protect Plant Embryos • Flowers and Fruits Increase the Reproductive Success of Angiosperms • Trends in Plant Evolution o Glaucophytes, red algae and green algae are ancestors of the land plants o Early land plants:  have no plumbing  gametophyte (haploid) is main part of plant o Later land plants  All have plumbing  In most, sporophyte (diploid) is main part of plant  Many are seed plants o Gymnosperms (“naked seeds”) o Angiosperms (“enclosed seeds”)  Charophytes are the closest relatives of land plants  Algae: o Two algal groups in Plantae: Red and Green Algae o Red algae – Most are marine. o Green algae – Have chlorophyll a and b (green) in chloroplasts; store energy as starch. o Charophytes are most closely related to land plants.  Some Key Adaptations of Land Plants: 1. Cuticle, a waxy coating 2. Stomata, closable openings 3. Gametangia, organs that enclose gametes and prevent them from drying out. 4. Embryos, young plants contained within a protective structure. 5. A mutually beneficial association with fungi that promotes nutrient uptake and water from the soil.  Land plants: o Non-vascular (non-tracheophytes) ex. mosses o Vascular (tracheopythes):  No seeds ex. ferns  With seeds, but no flowers ex. pines  With seeds and flowers ex. orchids  Land plants all have alternation of generations: o Includes a multicellular diploid stage and a multicellular haploid stage. o Gametes are produced by mitosis, spores are produced by meiosis. o Spores develop into multicellular haploid organisms.  Sporophyte – the multicellular diploid plant o Cells in specialized structures called sporangia produce haploid spores by meiosis.  Gametophye – the multicellular haploid plant. Spores develop into gametophytes. o Gametophyte produces haploid gametes by mitosis. o Fusion of gametes produces a diploid zygote, which develops into the sporophyte.  Nonvascular plants: o Live in moist habitats; have thin cuticles. o Mostly small; they have no well-developed vascular system to transport water, so size is restricted. o Small enough that minerals can be distributed throughout their bodies by diffusion o Have stomata  Mosses: o Gametophyte is photosynthetic, nutritionally independent of sporophyte. o The sporophyte, however, is always nutritionally dependent on the gametophyte and remains attached to it. o Gametes are produced in specialized structures called gametangia. The sperm must swim or be splashed by water to reach the egg. o In mosses, liquid water is still necessary for fertilization!  Vascular Tissues Led to Rapid Diversification of Land Plants o A vascular system consists of tissues specialized for transport of water and materials from one part of the plant to another. o Evolution of vascular tissue allowed land plants to spread to new environments and diversify rapidly.  Ferns: Vascular plants that are largely terrestrial o Still require liquid water for movement of sperm, so most inhabit moist woodlands and swamps o Gametophyte is small and short-lived; it is independent of sporophyte! Sporophyte can be very large (note difference from mosses) and can sometimes survive for hundreds of years.  Pollen: o Seed plants evolved independence from water for getting the sperm to the egg, allowing them to colonize drier habitats. o The male gametophyte is a pollen grain. o Seeds Protect Plant Embryos o Seeds viable for long periods. o Seed coat protects the embryo. o Many seeds have adaptations to aid in dispersal. o When the embryo begins to grow, it draws on nutrients stored in the seed. o Seeds are one of the major reasons for the evolutionary success of seed plants.  Non-flowering Seed Plants o Gymnosperms—seed plants that do not form flowers or fruits. o Ovules and seeds are not protected by ovary or fruit tissue. “Gymnosperm” means naked seed. o Has simpler plumbing than in flowering plants. o Most are woody plants. Our example of a non-flowering seed plant is a conifer (cone-bearing) tree-a pine tree.  Seeds Protect Plant Embryos o Conifers: dominate forests at high latitudes and high altitudes.  Cones contain the reproductive structures.  female cones in which seeds are protected by woody scales  male pollen-bearing cones  Flowering Plants- Angiosperms o Angiosperms—reproductive organs in flowers; seeds develop in ovaries and are enclosed in fruits. o Female gametophyte very reduced—usually only seven cells. o Male gametophyte is the pollen grain. o Largest clades of angiosperms:  Monocots (1 cotyledon); grasses, lilies, orchids  Eudicots (2 cotyledons); most trees and many shrubs and annual plants. o Synapomorphies of the angiosperms: • Double fertilization • Nutritive tissue called the endosperm • Ovules and seeds enclosed in a carpel • Germination of pollen on a stigma • Flowers • Fruits • Phloem with companion cells • Reduced gametophytes  Fruits: o Fruits develop from the ovaries after fertilization. o Fruits protect seeds and aid in dispersal. Most survive passage through the digestive organs of animals.


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