Adjustments to Life in Air

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2 Adjustments to Life in Air Plants and Animals no buoyancy, need skeletal support desiccation physical-chemical environmental extremes (temperature, humidity, salinity) no nutrients in air reproductive cycle needs to be modified 2

3 Origin of Land Plants - aquatic green algae transfer food between cells -an aquatic habitats of temporary drying, evolved to disperse spores in air from sporangia that extended into the air - photosynthesis increased: more CO 2 and more direct sunlight - evaporation of H 2 O into air enhanced water transport between cells - conducting stands carried water upward in mosses -waxy cuticle evolved: protects and seals the plant, stops nutrient and gas intake - roots evolved: specialized absorbing structures at base of plant - stomata: pores for CO2 uptake through cuticle, closed by guard cells - intercellular gas transport - xylem: plumbing for better upward water and nutrient flow - secondary xylem = wood - plants with xylem are vascular plants - lignin: strengthens xylem cell walls - phloem: transports water and nutrients around the plant Plants Invade the Land Prior to land plants, moist terrestrial environments were inhabited exclusively by algae, cyanobacteria, and fungi. Earliest spores fossilized in Middle Ordovician rocks. The land invasion by plants took place in the Late Silurian and Early Devonian Land plants require rigid stems and underground anchors (roots and/or stems) 3

4 Vascular Plants Vascular tissues stems with tubes that: 1) carry water and nutrients upward; and 2) internally distribute food. In addition, some had leaves to capture sunlight for photosynthesis Originated in Late Silurian Vascular Plant Rhynia 4

5 Spore Plants Spores reproductive structures that can grow into new adult plants when released into the environment (ferns) Aquatic forms originated in Ordovician, terrestrial in the Late Silurian and radiated in the Devonian Lycopods early and middle Devonian, related to modern club mosses, grew the size of trees Protolepidodendron Spore plant trees in Late Devonian (30 m high) Archaeopteris, reproductive cycle would have restricted to damp places (sperm traveled over plant to fertilize eggs) Vascular Plant Baragwanathia 5

6 Lycopods Lycopods 6

7 Archaeopteris Archaeopteris 7

8 Seed Plants Seeds originated in the Devonian, pollen travels through air to fertilize eggs so that seeds can grow Flowerless seed plants Late Devonian Plants served to stabilize and reduce erosion, moved from braded streams to meandering rivers Root fungii Late Devonian 8

9 Later Paleozoic Plants Early Paleozoic plants significantly different from the Late Paleozoic New insects and spore trees in the Mississippian, replaced by seed trees in the Permian Coal deposits developed in lowland swamps, wetlands much more extensive than today Dominant coal swamp flora: Lycopods spore plants up to 30 m tall and 1 m diameter trunks Lepidodendron Sigillaria 9

10 Land plants were the base of the food web for dinosaurs Land plants did not experience a major mass extinction at the PT boundary, decline of Paleozoic floras (lycopods, sphenopsids, cordaites) started long before the end of the Permian Ferns and seed ferns survived into the Triassic, but seed ferns went extinct in the Jurassic. Ferns dominate Triassic fossil flora. Most trees were gymnosperms. The most diverse gymnosperms were the cycadeoids or cycads, followed by conifers and ginkos (gymnosperms = exposed seeds) Jurassic period called Age of the Cycads due to their dominance of forests in the Jurassic Flowering plants did not evolve until the Cretaceous Upper Devonian first seeds 10

11 Carboniferous Trees: A) Lepidodendron; B) Siggilaria 11

12 Carboniferous Forrest Late Carboniferous insect: Mazon Creek Illinois 12

13 Pennsylvanian Seed Fern Carboniferous sphenopsid Calamites 13

14 Modern sphenopsid horsetail Carboniferous cordaite tree 14

15 Carboniferous conifer 15

16 A tropical forest - Surprisingly tall ferns, horsetails, and lycophytes dominated tropical Carboniferous forests. Continental congregation The collisions between continents were widespread in the Carboniferous Period. 16

17 Coal Carboniferous ( million years ago) AMAX Delta Mine, Williamson County, Illinois E20961 Today, more than 50% of our energy in the United States is generated by coal-burning power plants. Coal-bearing rocks underlie 37,000 square mile of Illinois (that s 68% of the state!) It s the second largest reserve in the nation and is high in sulfur, which is hard on the environment. 17