Biol 301 1st EditionExam # 2 Study Guide Lectures: 6 - 11Adaption- Some body tissues are denser than water (e.g., bone); some are less dense (e.g., fats).- Organisms have developed many adaptations to cope with their tendencies to sink or float. People who are fat float easier, stronger, denser people with less body fat sink easier- Water has a high viscosity; many organisms have evolved streamlined bodies that reduce the drag caused by high water viscosity.- To take advantage of water’s viscosity, many tiny marine animals have evolved long, filamentous appendages that increase drag.- Aquatic organisms need variable amounts of essential elements, such as hydrogen, carbon, oxygen, nitrogen, phosphorus, potassium, and calcium to build organic compounds.- Solutes: dissolved substances in water.- Water inside and outside an organism often contains different concentrations of solutes.- Water moves to equalize solute concentrations in different locations.- Semipermeable membranes: membranes that allow only particular molecules to pass through; reduces free movement of solutes.- Osmosis: movement of water across a semipermeable membrane.- Osmotic potential: the force with which a solution attracts water by osmosis.- Osmoregulation: mechanisms organisms use to maintain a proper solute balance.o Hyperosmotic: tissue solute concentrations are higher than surrounding water.o Hyposmotic: tissue solute concentrations are lower than surrounding water.- Sharks and rays convert ammonia, a by-product of protein digestion, into urea.- Most urea is excreted, but some is retained in the bloodstream. This raises the osmotic potential of their blood to that of seawater, which balances water movement.- Animals can be harmed by exposure to abnormal salt concentrations.- Plants growing in salty environments also face major challenges of salt balance (e.g., root uptake of water).- Plants need carbon dioxide (CO2) for photosynthesis.- CO2 diffuses slowly through water; plants use CO2 faster than it diffuses into leaf tissues.- CO2 is rapidly converted to bicarbonate (HCO3–) or carbonate (CO3–) ions, which accumulate in massive quantities and can be used for photosynthesis.- Even when CO2 and HCO3– are abundant, they diffuse slowly and limit plant growth.- Boundary layer: a region of unstirred air or water that surrounds the surface of an object. Removed gases from this region are slow to be replaced; this further limits carbon availability.- Oxygen gas (O2) in air is 21% by volume; in water it is 1%. Not a problem for aquatic organisms that rise to the surface to obtain O2 from the air (e.g., whales).- The low solubility and slow diffusion of O2 can limit the metabolism of organisms that obtainO2 from the water. O2 can become severely depleted in waters that do not support photosynthesis (e.g., waterlogged sediments, deep water).- Countercurrent circulation is an adaptation where blood and water flow in opposite directions so that the concentration of O2 in water is always greater than the concentration in blood.- In deep oceans, many organisms have low activity rates, which reduces O2 demand.- When an environment becomes completely devoid of oxygen, it is referred to as anaerobic or anoxic.- Some plants (e.g., mangroves) extend their roots above the soil surface to absorb O2 from the air.- Many microbes live in anaerobic environments by using other sources of metabolic energy.- Heat causes biological molecules to change shape.- Heat accelerates chemical reactions by increasing molecular movement.- The rate of most biological processes increases 2 to 4 times for each 10°C rise in temperature.- Q10 value: a ratio of a physiological process rate at one temperature to the rate of that process when the temperature is 10°C cooler.- Proteins and other biological molecules become less stable, may not function properly, and may denature (i.e., open up).- Fats become fluid with heat, and stiff with cold.- Thermal pollution: changing the temperature of an environment via human discharges (e.g.,effluent from nuclear power plants).- Some bacteria are thermophilic (heat-loving) and can live at temperatures up to 110°C.- The crystal structure of ice can damage living cells.- Marine vertebrates are susceptible to freezing; added solutes in seawater lower freezing point to –1.9°C, whereas the freezing point of water in animals is higher. - Glycerol and glycoproteins: chemicals present in some animals (e.g., Arctic cod) that preventfreezing by reducing strength of hydrogen bonds or via supercooling (i.e., coating of ice seeds).- Thermal optima: the range of temperatures in which an organism best performs. Temperatures that exceed thermal optima can be detrimental.- Determined by the properties of an organism that influences the ability to function (e.g., enzymes and lipids, the structure of cells and tissues, body form).- Isozymes: different forms of an enzyme that catalyze a reaction.- Having two or more isozymes suited for different temperature ranges is useful for organismsthat must cope with variable temperaturesNatural Selection- Adaptationo The match between organisms and their environmento Result of natural selection- Natural Selection—the process (mechanism) of evolutiono Darwin originally used the phrase descent with modification- Requirements for Evolution by Natural Selection – o (More offspring are produced than survive)o Variation among individualso Inheritance of variationo Individuals with favorable characteristics are more likely to survive and reproduceDifferential survival and reproduction related to this variation–Selection- Genetic variation allows evolution by natural selection.- Deoxyribonucleic acid (DNA): a molecule composed of two strands of nucleotides that are wound together into a double helix. Each strand is composed of subunits called nucleotides. Each nucleotide has a sugar, a phosphate group, and one of four nitrogenous bases: adenine(A), thymine (T), cytosine (C), and guanine (G). The order of nitrogenous bases codes for genetic information.- Chromosomes: compact structures consisting of long strands of DNA wound around proteins.- Alleles: different forms of a particular gene. Genes are regions of DNA that code for particular proteins; changes in some phenotypes are affected by a single allele (e.g., blood type). Changes in alleles can create differences in an