Survey
* Your assessment is very important for improving the workof artificial intelligence, which forms the content of this project
* Your assessment is very important for improving the workof artificial intelligence, which forms the content of this project
I. Challenges of Life in the Sea A. Salinity 1. Diffusion and Osmosis • • • Diffusion problematic – leads to loss of important ions Selectively permeable cell membrane limits movement of certain molecules (large, electrically charged) but allow movement of small molecules, e.g. water Osmosis – Diffusion of water across selectively permeable membrane • Water diffuses from region of higher water concentration (lower salt concentration) to region of lower water concentration • Possible to move molecules against concentration gradient by using energy to power active transport Fig. 4.13 I. Challenges of Life in the Sea A. Salinity 2. Regulation of Salt and Water Balance • • • Osmoconformers • Energetically inexpensive • Limits distribution to areas with stable salinity (Where?) Osmoregulators • Expend energy to maintain body fluid composition • Less constrained by salinity in habitat Euryhaline vs. Stenohaline Fig. 4.14 Fig. 4.15 I. Challenges of Life in the Sea B. Temperature • Rates of metabolic reactions double for each 10 oC increase in temperature Most marine organisms adapted to specific temperature range Species distributions often based on temperature of water • • • • • • • Polar Cold temperate Subtropical (warm temperate) Tropical Eurythermal vs. Stenothermal Fig. 4.16 I. Challenges of Life in the Sea B. Temperature • Ectotherms – Body temperature essentially determined by temperature of environment • • • Often poikilotherms (“cold blooded”) Some species warm certain tissues to improve performance (tuna, billfish, some sharks) Endotherms – Maintain elevated internal body temperature • • • Usually homeotherms (“warm blooded”) Energetically expensive Insulation may help to conserve heat • Blubber • Feathers • Hair I. Challenges of Life in the Sea C. Surface-to-Volume Ratio • Organisms exchange heat and substances across body wall • • • • • • • Fig. 4.17 Nutrients Gases Waste products Rate of exchange depends on S/V ratio Ratio decreases as organism size increases, if shape stays the same Smaller organisms exchange materials by diffusion Larger organisms have special systems to exchange materials II. Prokaryotes A. Bacteria • • Many shapes - spheres, coils, rods, rings Very small cells (usually less than 1 μm across) • • • • Little known until second half of 20th century Exceptions - 570 to 750 μm diameter in sediments (filamentous) and fish guts Rigid cell walls May reach very high densities under favorable conditions Heterotrophic Bacteria 1. • • • Most are decomposers (break down organic material) Important in nutrient recycling Important components of organisms’ diets, especially for benthic organisms II. Prokaryotes A. Bacteria 2. Autotrophic Bacteria a. Fig. 4.7 Photosynthetic (Photoautotrophic) • Obtain energy from sunlight • Contain chlorophyll or other photosynthetic pigments • Important primary producers in open ocean b. Chemosynthetic (Chemoautotrophic) • Obtain energy from chemical compounds - Hydrogen - Hydrogen sulfide - Ammonia II. Prokaryotes A. Bacteria 3. Cyanobacteria (Blue-green) • • • • • • Photosynthetic Contain chlorophyll + phycocyanin & phycoerythrin Some form filaments or mats Some similarities to eukaryotic algae • Contain chlorophyll a • Produce gaseous O2 May have been first photosynthetic organisms on earth Fossil stromatolites from 3 billion years ago • Calcareous mounds containing sediment and cyanobacteria http://www.fossilmall.com/Science/About_Stromatolite.htm http://www.fossilmall.com/Science/About_Stromatolite.htm II. Prokaryotes A. Bacteria 3. Cyanobacteria (Blue-green) • • • Occur in a variety of habitats • Polar bear hair • Endolithic (inside calcareous rocks and coral skeletons) • Rocky shorelines (black crusts) • Epiphytic (on algae or plants) • Endophytic (inside algal or plant cells) Many carry out nitrogen fixation • Very important process Some forms have lost ability to photosynthesize • Live as heterotrophs