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Monday, May 22, 2017 THE “EVOLUTION” OF SEED PLANTS 1 Packet #71 Chapters 29, 30 & 38 Monday, May 22, 2017 THE “EVOLUTION” OF PLANT ORGANS 2 Monday, May 22, 2017 “EVOLUTION” OF ROOTS The “evolution” of roots allowed plants to become anchored and helped enable them to absorb water and nutrients from the soil Roots allow the shoot system to grow taller and contain lignified vascular tissue. 3 Monday, May 22, 2017 “EVOLUTION” OF LEAVES See Pages 584-586 Chapter 29 Figure 29.13 Page 586 Leaves increase the surface area of vascular plants. Leaves can be classified as microphylls or megaphylls All lycophytes (club mosses) have small, usually spineshaped leaves with a single vein Microphylls Leaves of other “modern” vascular plants are known as megaphylls The larger sized leaves are possible due to the highly branched vascular system which supports greater photosynthetic activity. 4 Monday, May 22, 2017 THE EVOLUTION OF SEED The evolution of seed facilitated reproduction on land Plants that produce seeds may be placed into two categories Gymnosperms Angiosperms A seed consists of a plant embryo packaged with a food supply in a protective coat The first vascular plant, according to the theory of evolution, originated about 360 MYBP in the Devonian Period. Those seeds were not enclosed in any special chambers. These plants evolved into the gymnosperms “The Naked Seeds” 5 Monday, May 22, 2017 THE EVOLUTION OF FLOWERS According to the theory of evolution, flowers evolved in the Cretaceous Period about 130 MYBP Led to further plant diversity A flower is a complex structure that bears seeds within a protective chamber called an ovary. Most “modern day” flowering plants are known as angiosperms. 6 Monday, May 22, 2017 APICAL MERISTEMS Recall, plants cannot move. The elongation of their shoots and roots maximizes their exposure to environmental resources. Growth occurs throughout the life of the plant via cell division in the apical meristematic tissue found at the tips of roots and shoots. Cells produced by meristematic tissue can differentiate into various plant tissues. 7 Monday, May 22, 2017 INTRODUCTION TO THE SEED AND SEED BEARING PLANTS 8 Monday, May 22, 2017 INTRODUCTION TO SEED BEARING PLANTS Seed plants are vascular plants that produce seeds. After fertilization in seed plants, an ovule (megasporangium) and its enclosed structures develop into a seed Earliest fossilized seeds are gymnosperms. 360 MYBP Seed plants dominate modern landscapes and are a large component of plant diversity. Seed bearing plants have important reproductive adaptations: Continued reproduction of the gametophyte The advent of the seed The evolution of pollen 9 The gametophytes of seed plants are even smaller than those of the seedless vascular plant and are protected in the ovules and pollen grains, Miniature female gametophytes develop from spores that are retained within the parental sporophyte. Monday, May 22, 2017 INTRODUCTION II 10 Seeds are the primary means of reproduction and dispersal of flowering plants. Seeds are reproductively superior to spores. Embryonic development is further advanced in seeds Seeds contain an abundant food supply Each seed has a protective coat. Monday, May 22, 2017 COMPARISON OF SEEDS VS. SPORES 11 Seed dispersal becomes important in adaptations Seed is a resistant structure that is multicellular and complex. Seed consists of a sporophyte embryo packaged with food in a protective coat Seeds can be dispersed by wind, water and animals. Monday, May 22, 2017 SEEDS, DISPERSAL & ADAPTATION 12 All seed bearing plants are heterosporous Monday, May 22, 2017 SEED BEARING PLANTS These plants have different types of sporangia that produce two types of spores. Megasporangium Microsporangium 13 Mega. vs. Micro. Megasporangia Produce megaspores *Retained in the parent sporophyte Formed within the megasporangium Enveloped with tissue called integumens Diagram on Page 586 Monday, May 22, 2017 HETEROSPOROUS SPORE PRODUCTION *Entire structure is called the ovule Microsporangia Produce microspores Develop into male (sperm containing) gametophytes. The development of pollen reduced the need for water for fertilization. 14 Develop into female (egg containing) gametophytes. Monday, May 22, 2017 MEGASPORES In the female gametophyte, there is the production of one or more egg cells If egg is fertilized by sperm, the zygote develops into a sporophyte embryo The ovule, that contains the fertilized egg, develops into a seed. Seed may be viable for days, months or years. 15 Microspores develop into pollen grains Pollen grains mature to become the gametophytes of seed plants Monday, May 22, 2017 MICROSPORES The most common gymnosperms, and all angiosperms sperm, lack flagella. Pollen can be transferred by wind and animals. 16 The transfer of pollen to ovules Monday, May 22, 2017 POLLINATION Self Pollination Cross Pollination 17 Monday, May 22, 2017 REVIEW 18 Students List potential examination questions and/or here, and on following slides, based on the packet. Monday, May 22, 2017 REVIEW 19