BIOL 152 1st Edition Lecture 10 Outline of Last Lecture I Case Study a Symbiosis b Endosymbiosis II Organismal Structure and function a Single celled organisms b Multi cellular organisms III Protists a Classification i Excavata ii Chromalveolata iii Archeoplastida iv Green Algae Outline of Current Lecture I The green algae are the closest relatives of the land plants a Green algae and land plants share many features b Green algae are NOT monophyletic c The Caryophyceans are sister to the land plants II The colonization of Earth presents many challenges a Consider the habitat s of the ancestors of land plants b Review the major challenges III A series of key innovations permit colonizing Earth a Reflect upon the synapomorphies of land plants b Leaf morphology illustrates some of the solutions to desiccation c Stoma or stomates regulate water loss in many plants IV One clade of land plants evolved complex vascular tissues a Xylem is a complex tissue that functions to transport water b Energy is not required to move water c Phloem is a complex tissue that functions to transport the product of photosynthesis d Energy IS required for phloem to move sugars via bulk flow These notes represent a detailed interpretation of the professor s lecture GradeBuddy is best used as a supplement to your own notes not as a substitute Current Lecture Plant Structures and Function Green Algae Very diverse o Unicellular or multicellular o Filamentous colonial Habitat o Freshwater to marine o Terrestrial soil snow o Symbiotic lichens Synapomorphy o None not monophyletic o Phylogenetically classify 2 choices Recognize as two separate lineages Combine green algae and land plants Chlorophyta and PlantsMany similarities Chlorophyll A and B Storage CHO starch inside plastids Cell walls sometimes cellulose Some have plasmodesmata Charophyceans Most closely related to plants Major challenges to move to land Communication between cells Plasmodesmata pores between cells provides an efficient mechanism for translating information Desiccation Many adaptations Gas Exchange Stomata pores on leaf and stem surface have the ability to open and close for gas exchange Sexual Reproduction Alternation of multicellular generations Basic anatomy of a plant Cells tissues tissue system organs Tissue systems dermal ground and vascular Continuous in plant vary in appearance in different organs Anatomy of a typical leaf Many adaptations and variations on this general theme Must balance uptake of CO2 and loss of H2O o Epidermis o Mesophyll o Stoma Review Water and Life Basics of water movement same for all Water not actively pumped between cells Moves passively by osmosis diffusion of water across a semi permeable membrane Diffusion tendency of a substance to move down its concentration gradient Semi permeable membrane water moves passively often solutes do not Stoma and Guard Cells Stoma open in response to sunlight Pump in solutes and water If stoma were blocked photosynthesis would stop due to the inability to obtain CO 2 Vascular tissue A key innovation Function transport all plant organs Two types Xylem moves water and dissolved minerals Phloem moves nutrients solutes Water H2O Molecules on one end and on the other o Forms hydrogen bonds between molecules Cohesive stick together o Surface tension Adhesion Transpiration where plants lose most of their water Trade off o Gain CO2 for photosynthesis get rid of excess O2 o Lose water More water loss more pull Forces that pull water from the soil Pressures extend all the way down to root Cohesion tension model Cohesion o Water column in xylem o H bonds between water Tension p o From evaporating water in leaves o Pulls column upwards Adhesion o H bonds with xylem walls o Helps counter gravity Water moves up a plant by moving down a pressure gradient Vascular Bundle Composed of xylem and phloem Phloem tissue o Transport of photosynthate o Living cells o Photosynthates are sugars which require energy to move between cells Two kinds of cells o Sieve cells Cell to cell connections simple sieve areas Passage of materials cell to cell Contain nuclei o Sieve tube elements Cell to cell connections complex sieve plates Very efficient rapid movement of materials Lack nuclei Companion cells contain nuclei and work in partner with sieve tube elements to help regulate Phloem transport Source sink Source leaves usually Sink area of active growth Sink storage ares Bulk flow of phloem sap Sucrose from source o Into sieve tube o By active transport o Requires energy transport Water from xylem o Into sieve tube by diffusion Hydrostatic pressure flow o Carries sucrose along Sucrose in sieve tube o Into sink by active transport Water o From sieve tube into xylem by diffusion
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