Chapter 29 First Land Plants 1 2 billion years ago cyanobacteria existed 500 million years ago land plants and animals 385 million years ago first forest o Plants supply oxygen an food for terrestrial animals Evidence that land plants evolved from green algae Morphological o Both land plants and brown red green algae are multicellular eukaryotic and photosynthetic autotrophs o Cell walls of cellulose o Use of chlorophyll a and b o Charophytes share 4 traits with land plants Rings of proteins that make cellulose microfibrils in the plasma membrane Noncharophyte algae have linear sets of proteins Have peroxisomes to minimize loss of organic products that come from Structure of flagellated sperm closely resemble those of land plants with photorespiration flagellated sperm Phragmoplast group of microtubules forms between daughter nuclei Cell plate then forms in the middle of the phragmoplast and divides the cell as it forms a cell wall Shared by land plants and some charophytes genera Chara and Coleochaete o Charophytes especially Chara and Coleochaete are the closest living relatives of Genetic evidence land plants Adaptations enabling the move to land o Sporopollenin prevents expose zygotes from drying out Charophytes o Benefits of living on land Light unfiltered by water and plankton More CO2 from the atmosphere Soil rich in nutrients o Challenges Scarcity of water Lack of support against gravity Plantae embryophytes plants with embryos o 4 main Derived traits of plants 1 Alternation of generations multicellular sporophytes and gametophytes Gametophyte multicellular haploid organism makes gametes through mitosis o Gametes fuse to make a zygote which develops into a sporophyte o Embryos develop inside the female gametophyte o Placental transfer cells enhance the transfer of nutrients from parent to embryo Analogous to placentae in mammals Sporophyte multicellular diploid makes spores through meiosis Embryophytes land plants with embryos 2 Walled spores made in sporangia Sporangia organs possessed by sporophytes that make spores o Sporocytes undergo meiosis 3 Multicellular gametangia Gametangia organs that make gametes through mitosis o Archegonia female gametangia Make eggs o Antheridium male gametangia Make sperm often flagellated and rely on water 4 Apical meristem localized regions of cell division at the tips of roots and shoots o Other derived traits microbial attack Cuticle wax and polymers on plant that prevents drying out and protects from Early plants had no roots so they depended on symbiotic associations with fungi Secondary compounds compounds made from side branches off primary metabolic pathways that make basic macromolecules Alkaloids terpenes and tannins toxic bitter Flavonoids absorb UV radiation Deter pathogens Origin and diversification of plants o Vascular tissue cells joined into tubes that transport water and nutrients Way to distinguish plant groups Bryophytes common name for non vascular plants Not actually a clade Vascular plants plants with complex vascular tissue system Seedless vascular plants o Lycophytes club mosses o Pterophytes ferns and relatives Seed plants distinguished by the packaging of the seed o Seed embryo packaged with a supply of nutrients inside a protective coat o Gymnosperms naked seeds o Angiosperms flowering plants Grade collection of organisms that share a key biological feature abut don t necessarily have 1 common ancestor Mosses and other nonvascular plants have lifecycles dominated by gametophytes 3 phyla of nonvascular plants o Liverworts hepatophyla o Hornworts antherocerophyta o Mosses bryophyta Gametophyte is the dominant stage o Sporophyte is only present part of the time o Gametophyte is a protenoma and 1 or more gametophores Protonema mass of 1 cell thick filaments that will bud in favorable conditions to make one or more gamete producing gametophores o 2 reasons why gametophytes are short Lack of support from thin structures No vascular tissue limited to how far diffusion can distribute water and nutrients o Rhizoids anchors for bryophytes Not actually composed of tissues lack specialized cells and don t play a primary role in water mineral absorbance o Gametophytes can have several gametangia usually only 1 type Archegonia and antheridia Fertilization requires water Embryos are kept in archegonia and develop into sporophytes Many bryophytes reproduce asexually by making broad bodies that break off and grow into new copies Bryophyte sporophytes o Cannot live independently rely on gametophyte o Foot absorbs nutrients from gametophyte o Seta stalk o Capsule sporangium that makes spores through meiosis Peristome part of capsule that opens and releases spores during drier times Hornworts and liverworts have stomata Ecological and economic importance of mosses o Found all over the world o Can help retain soil nitrogen o Can live in cold or dry habitats able to rehydrate after losing most of their water o Peat partially decayed organic material made with sphagnum moss Used as fuel Soil conditioner Peatlands contain 30 of world s carbon Overharvesting releasing CO2 and contributing to global warming Ferns and other Seedless Vascular Plants were the first to grow tall Origins and traits of vascular plants o Sporophytes no longer dependent on gametophytes o Sporophytes dominant Fern fronts are the sporophyte o Transport in xylem and phloem Xylem conducts water Tracheid s tube shaped cells that carry water and minerals up the cell vascular plants sometimes called tracheophytes Lignified contain the polymer lignin that strengthens the cells o Allows plants to grow tall and outcompete other plants for sunlight Phloem cells in tubes that carry sugars amino acids and organic products o Evolution of roots Roots organs that Anchor plants Absorb water and nutrients from the soil o Evolution of leaves Leaves increase surface area and serve as primary site of photosynthesis Lycophytes oldest lineage of present day vascular plants have microphylls Microphylls small spine shaped leaves supported by 1 strand of vascular tissue o Probably evolved from sporangia on the side of the stem Almost all other vascular plants have megaphylls Megaphylls leaves with highly branched vascular system o Probably evolved from several branches close to one another Sporophylls and spore variations o Sporophyll modified leaves that have sporangia In ferns Sori clusters of sporangia on the underside of sporophylls In gymnosperms Strobili cone like structures of
View Full Document
Unlocking...