The Importance of Plants, their origins and ways of life

1. The Importance of Plants, their origins and ways of life Objectives of the lecture: 1. Describe some ways that plants provide the foundation of life. 2. Provide the basic sequence of plant evolution and its relationship to changes in earth landforms and environment. 3. Describe the endosymbiosis theory. 4. Identify important adaptations of plants that enable them to live on land. Text book pages: 548-553 604, 609, 626-639,

3. Ginkgo biloba Illustration in Pen Tsao Kang Mu of Ginkgo with seeds (1578) Motile male sperm The only surviving species of a diverse group originating in the Permian, closely related fossils 200m ybp Ginkgo biloba extract (Gbe) and two ingredients, bilobalide and ginkgolide B, are part of a review of botanicals being used as dietary supplements in the United States. Deregulation of botanicals now permits Gbe to be sold as a dietary supplement to a willing public eager to "improve brain functioning" or "promote radical scavenging activity".

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5. Plan for Biology 220 Spring 2010

6. Why are plants important for human life? Page 627-630 How do they do that? 1. Plants produce oxygen Green plant photosynthesis 2. Plants build soil Rock weathering and carbon build-up and decomposition 3. Plants hold soil Root strength and ramification through soil 4. Plants hold water The “reservoir” function of plants and soil 4. Plants moderate the local climate Evapo-transpiration and particle capture 6. Plants provide food, fuel and fibre 7. Plants provide drugs Next slide

7. Figure 30-4-Table 30-1 Know 5 of these What functions might these substances have in plants?

8. Opium poppy, Papaver somniferum The opium poppy is the principal source of all natural opiates. Opiates are extracted from opium and poppy straw. Opium is the latex harvested by making incisions on the green capsules (seed pods). Evolution? Mature seed pod of the opium poppy (Papaver somniferum) with milky latex sap dripping from a recent cut. The latex sap contains a mixture of naturally-occurring narcotic alkaloids including morphine and codeine. Morphine is acetylated to produce diacetylmorphine, better known as heroin.

9. Figure 30-8 Cones from Araucaria mirabilis, an early gymnosperm Seed fern leaves Cooksonia pertoni Archaefructus, an early angiosperm Origin of land plants Carboniferous: Lycophytes and horsetails abundant Silurian-Devonian explosion Angiosperms abundant Gymnosperms abundant 299 145 475 mya 444 Present 359 Most major morphological innovations: stomata, vascular tissue, roots, leaves Extensive coal-forming swamps Both wet and dry environments blanketed with green plants for the first time Diversification of flowering plants First evidence of land plants: cuticle, spores, sporangia

10. History of evolution of major plant types on land

11. Life’s Timeline: The Precambrian The Precambrian (Hadean, Archaean, and Proterozoic Eons) included the origin of life, photosynthesis, and the oxygen atmosphere. First oceans; heavy bombardment from space ends First evidence of oxygenic photosynthesis First rocks containing oxygen (in atmosphere and ocean) First evidence of photosynthetic cells First sponges; first bilaterally symmetric animals; ocean completely oxygenated First photosynthetic eukaryotes First red algae; first evidence of sexual structures Formation of solar system Earth formation complete Liquid water on Earth First lichen-like organism First eukaryotic fossils Moon forms Origin of life Hadean Eon Archaean Eon Proterozoic Eon All life is unicellular Multicellular organisms begin to diversify slowly Millions of years ago (mya) Position of the continents unknown Most of Earth is covered in ocean and ice. How did multi-cellular green organisms develop?

12. How did multi-cellular green organisms develop? Endosymbiosis An endosymbiont is any organism that lives within the body or cells of another organism, i.e. forming an endosymbiosis (Greek: ἔνδον endon "within", σύν syn "together" and βίωσις biosis "living"). Examples: nitrogen-fixing bacteria (called rhizobia) that live in root nodules on legume roots, single-celled algae inside reef-building corals, and bacterial endosymbionts that provide essential nutrients to about 10%–15% of insects. Andreas Schimper observed in 1883 that the division of chloroplasts in green plants closely resembled that of free-living cyanobacteria (blue-green algae) and tentatively proposed that green plants had arisen from a symbiotic union of two organisms. Margulis and Sagan (2001) "Life did not take over the globe by combat, but by networking"

13. THE ENDOSYMBIOSIS THEORY FOR MITOCHONDRIA AND CHLOROPLAST EVOLUTION Page 604 Proposed evolutionary origin for mitochondria Aerobic bacterium Pyruvate and O2 ATP Anaerobic eukaryote 3. Eukaryote supplies bacterium with protection and carbon compounds. Bacterium supplies eukaryote with ATP. 1. Eukaryotic cell surrounds and engulfs bacterium. 2. Bacterium lives within eukaryotic cell. Each would have performed mutually benefiting functions from their symbiotic relationship.   The aerobic bacteria would have handled the toxic oxygen for the anaerobic bacteria, and the anaerobic bacteria would utilize ingested food and protected the aerobic "symbiote".

14. Secondary Endosymbiosis p609 Serial ingestion of photosynthetic bacteria by endosymbiontic prokaryotes or eukaryotes led to the ancestors of eukaryotic plants. As the ingested photosynthetic bacteria adapted to the ingesting prokaryotic host cell, plastids, such as the chloroplast evolved. Primary plastids are found in some algae because their plastids are derived directly from a Cyanobacterium. All other lineages of plastids have arisen through secondary (or tertiary) endosymbiosis, in which a eukaryote already possessing plastids is engulfed by a second eukaryote. Considerable gene transfer has occurred among genomes and, at times, between organisms.

15. Mitochondria and chloroplasts contain DNA The most convincing evidence of the descent of these organelles from bacteria is the position of mitochondria and plastid DNA sequences in phylogenetic trees of bacteria. Mitochondria have sequences that clearly indicate origin from a group of bacteria called the alpha-Proteobacteria. Chloroplasts have DNA sequences that indicate origin from the cyanobacteria (blue-green algae). There are also organisms alive today, called living intermediates, that are in a similar endosymbiotic condition to the prokaryotic cells and the aerobic bacteria. For example, the giant amoeba Pelomyxa lacks mitochondria but has aerobic bacteria that carry out a similar role. A variety of corals, clams, snails, permanently host algae in their cells. Multiple nuclei

16. Multiple ingestions lead to a variety of endosymbiotic structures

17. Figure 30-39 Plant of the Day Lycopodium species

18. Life’s Timeline: The Paleozoic Era Phanerozoic Eon: The Paleozoic Era included the origin early diversification of animals, land plants, and fungi. First ferns, vascular plants, ascomycete fungi, lichens on land First mycorrhizal fungi (Glomales) First comb jellies, arthropods, vertebrates, other phyla First tetrapods (amphibians) First mammal-like reptiles First basidiomycete fungi First bryozoans (newest animal phylum) First plants with leaves Arthropods diversify; first echinoderm First cartilaginous fish First winged insects First tree-sized plants First fish with jaws First insects First seed plants First land plants First bony fish First vessels in plants First reptiles Carboniferous Mass extinction Mass extinction Mass extinction Permian Cambrian Ordovician Silurian Devonian Mississippian Pennsylvanian Coal-forming swamps diminish; parts of Antarctica forested First upland plant communities (evergreen forests), diversification of fish, emergence of amphibians Insects diversify, coal-forming swamps abundant, sharks abundant, radiation of amphibians Echinoderms (sea stars, sea urchins) diversify Coral reefs expand Algae abundant, marine invertebrates diversify Laurentia Pangea Gondwana Gondwana Gondwana Supercontinent of Gondwana forms. Oceans cover much of North America. Climate not well known. Climate cold; extensive ice in Gondwana. Supercontinent of Laurentia to the north and Gondwana to the south. Climate mild. Supercontinent Pangea assembles. Building of Appalachian Mountains ends. Climate warm; little variation.

19. Atmospheric O2 and CO2 concentrations through geological time 70cm wing dragonfly 1m long millipede and giant spiders Widespread arthropod gigantism Origin of insect flight Denser atmosphere, Greater O2 partial pressure Carboniferous coal formation CO2 removed from the atmosphere by plant synthesis and limestone type rock formation

20. Devonian plant community found at Rhynie, in Scotland. A reed-like marsh, 370-380 million years ago. Asteroxylon MAIN FEATURES Simple dichotomous branching Sporangia 15 to 30 cm tall No roots Stomata with guard cells Most had a central vascular strand Cuticle Asteroxylon had leaves –without a vascular connection Devonian plant community

21. Life’s Timeline: The Mesozoic Era Phanerozoic Eon: The Mesozoic Era is sometimes called the Age of Reptiles. First angiosperm (flowering plant) First nectar-drinking insects First tyrannosaurid dinosaur First magnolia-family plants First bird (Archaeopteryx) First placental mammals First centric diatoms First water lilies First bee; first ant First dinosaurs First mammals Mass extinction Mass extinction Mass extinction Triasssic Jurassic Cretaceous Flowering plants diversify Gymnosperms become dominant land plants; extensive deserts Gymnosperms continue to dominate land Dinosaurs diversify Pangea Pangea Gondwana India separated from Madagascar, moves north; Rocky Mountains form. Climate mild, temperate. Pangea begins to break apart; interior of continent still arid. Gondwana begins to break apart; interior less arid. Pangea intact. Interior of Pangea arid. Climate very warm.

22. Life’s Timeline: The Cenozoic Era Phanerozoic Eon: The Cenozoic Era is nicknamed the Age of Mammals. First fully aquatic whales Oldest pollen from daisy-family plants Earliest hominins First primates First horses First apes Homo sapiens Paleogene Neogene Pleistocene Pliocene Paleocene Eocene Oligocene Miocene Diversification of mammalian orders Diversification of angiosperms and pollinating insects Diversification of grazing mammals Continents continue to drift apart. Collision of India with Eurasia begins. Australia moves north from Antarctica. Palms in Greenland and Patagonia. Strong drying trend in Africa and other continents; grasslands form. Alps and Himalayas begin to rise. Continents close to present position. Beginning of Antarctic ice cap. Opening of Red Sea. North and South America joined by land bridge. Uplift of the Sierra Nevada. Worldwide glaciation.

23. Adaptation to living on land The land that plants colonized was hostile to life. Soil development was minimal. Land plants required several adaptations to be successful that require multi-cellular tissues mechanical strength for support, exposed light catching surfaces, anchoring system, conducting system for water, system for obtaining mineral nutrients, a way to restrict water loss in desiccating air, a means of reproducing and dispersing on land

24. Things you need to know ... 1. Why plants are important for human life. 2. Some drugs derived from land plants. 3. The geological time periods when plants of different types were abundant and how this relates to the environment of those periods. 4. The adaptations shown by plants to living on land.