Survey
* Your assessment is very important for improving the workof artificial intelligence, which forms the content of this project
Download Chapter 2 BOT3015L Introduction to Autotrophs and Osmotrophs
Transcript
Chapter 2 BOT3015L Introduction to Autotrophs and Osmotrophs Organisms able to synthesize nutritive substances required for growth (auto=self, troph=feed/grow) Organisms that take up nutritive substances required for growth by osmosis (osmo=take up from external, troph=feed/grow) Presentation created by Danielle Sherdan All photos from Raven et al. Biology of Plants except when otherwise noted Today • Plant cells – characteristics of plant cells – plastids – large central vacuoles – cell wall – effects of osmosis on plant cells – cell division Microscopy enables the discovery of cells Slices of cork. Drawing by Robert Hooke, who coined the term “cell” in the 1600s Harvesting cork for commercial purposes Modern cell theory The modern cell theory states that 1. All living organisms are composed of one or more cells 2. Chemical reactions of living organisms take place within cells 3. Cells contain the hereditary information of the organisms of which they are a part, and this information is passed from parent cell to daughter cell 4. Cells arise from other cells Generalized diagram of a plant cell Note: As you will observed, much variation from this generalized diagram exists. Cytoplasmic streaming of chloroplasts QuickTime™ and a Cinepak decompressor are needed to see this picture. Considering their function, why would movement of chloroplasts by cytoplasmic streaming be advantageous? Amyloplasts store starch Today, we will use staining techniques (iodine stains starch) to visualize amyloplasts in potato tubers Amyloplasts in a bean root Observing the vacuole Put cells in a bath of concentrated solution What do you expect? Osmosis Plasmolysis Normal physiological conditions --Low external solute concentration --High internal solute concentration, thus positive pressure inside. --Positive pressure in the plant cell pushes against the restricting cell wall, like a water balloon in a cage. Under high external solute concentrations --External water potential decreases to below that inside the cell, thus osmotic water efflux from the cell. This process is plasmolysis. Today • Plant cells – characteristics of plant cells – plastids – large central vacuoles – cell wall – effects of osmosis on plant cells – cell division Mitosis and cytokinesis Mitosis (nuclear division) simplified diagram chromosome replication during S phase of cell cycle chromosomes align along metaphase plate Homologous and are attached chromosomes to cytoskeleton chromosomes condense and nuclear envelope degrades nuclear envelope forms around each set of chromosomes chromosomes are pulled apart to opposite poles, notice both sets are identical Cell division in plants occurs at meristems Onion root meristem located at tip of root Compare mitosis and meiosis Total number of cell divisions? Fill in ploidy level in above “cells” Pairing of homologs? Crossing over? Comparison chart II mitosis meiosis Centromeres divide? How many daughter cells are genetically identical to original cell? or triploid or tetraploid… or tetraploid or hexaploid…, but not triploid, why?
