Respiration I. Two Types a. Cellular respiration i. Glucose + O2 ? CO2 + energy b. Organismic Respiration i. O2 ? body and it?s cells ii. Body and cells give off CO2 II. Ideal respiratory medium is air, not water a. This is because there is more oxygen in the air and it takes less energy to ventilate i. Ventilation-mechanism for moving the respiratory medium over the respiratory surface III. Ideal respiratory surface a. Lots of surface area-increases opportunity for gas exchange b. Thin walls-allow for easy diffusion c. Moist-O2 and CO2 must be dissolved in order to diffuse across the respiratory surface d. Should be lots of blood vessels IV. 4 major respiratory surfaces a. Body surface i. Mollusks, annelids, some amphibians ii. Animals should be small because small animals tend to have a large surface to volume ration iii. Low metabolic rate iv. If animal is terrestrial, it must live in a moist environment and/or secrete mucus b. Tracheal tubes i. Insects, some other arthropods ii. These systems have spiracles = openings in the body surface iii. Spiracles lead to tracheal tubes iv. Tracheal tubes end in tracheoles = fluid-filled terminals, where direct exchange of gases with the cells takes place v.Ventilation by body movements or tracheal tube movements c. Gills i. Mainly in aquatic animals ii. Chordates-usually internal gills 1. H2O goes into mouth and out of gills iii. Operculum 1. Covers gills in most bony fish 2. Protects and ventilates 3. None in sharks so they must swim continuously iv. Counter current exchange 1. Maximizes the difference in oxygen concentration between blood and the water 2. Greater than 80% of oxygen in water is removed 3. Gradient: Oxygen always goes from water ? blood v.Con-current flow 1. Only about 50% of oxygen in water is removed 2. Gradient would be switched 3. This doesn?t exist in nature vi. CO2 moves in the opposite direction, from blood? water d. Lungs Vertebrate Lungs V. Salamander a. Has simple sacs VI. Frog a. Has increased surface area b. Gulps air-no diaphragm muscle c. Forces air down with mouth and throat muscle VII. Reptiles a. Has an even more increased surface area b. Still simple VIII. Birds a. Lungs have extensions call air sacs-act like bellows (instruments or machines that by alternate expansion and contraction draws in air through a valve or orifice and expels it through a tube) -usually 9 air sacs b. Advantages of air sacs i. Make birds light (weight) ii Dissipate heat, which is associated with birds? high metabolic rate c. Parabrochi-thin-walled ducts in the lungs of birds; gases are exchanged across their walls i. Flying birds have about 1,800 ii. Non-flying birds have about 400 d. 2 cycles of inhalation and exhalation i. 1st cycle-air into posterior air sac?exhale into lungs ii. 2nd cycle-air into anterior air sac?exhale into lungs iii. Lungs-where the oxygen-carbon dioxide exchange occurs IX. Mammal Lungs (gets smaller as you go down) a. Nostrils b. Nasal Cavity c. Pharynx d. Glottis i. Opening to larynx and trachea ii. Epiglottis-closes over trachea when we swallow so food doesn?t go into lungs e. Larynx i. Vocal cords; supported by cartilage f. Trachea and Brochi i. Supported by C-shaped cartilaginous rings ii. Lined with cilia an mucus?trap particles, pathogens, and move up so you can swallow and destroy iii. Cilia get destroyed by cigarette smoking g. Bronchioles i. Many branches (more than 18,100) ii. Major Branches have cilia and mucus to protect them h. Aveoli i. Alveolus-singular ii. Alveoli-cluster of air sacs iii. Highly vascularized (this is good because you want to be able to pick up oxygen) iv. Over 300 million in human lungs v.Good for gas exchange because 1. Large Surface area-spread out a human lung, it would cover a tennis court 2. Thin wall vi. Emphysema-Decreased surface area for gas exchange, barrel chest, can?t force air out vii. Water molecules of inner alveolar surface?produce surface tension?encourages alveolar collapse 1. This is bad, but the water lining is crucial for gas exchange since O2 and CO2 molecules must dissolve 2. Surfactant-phospholipoprotein-coats the inside of the alveoli and lowers the surface tension, therefore interfering with the water molecule (H-H) bonding Mechanics of Breathing I. Negative pressure breathing a. Diaphragm and rib muscles change the volume of the thoracic cavity (lungs adhere) II. When there is an increase in lung volume, the pressure in the lungs decreases (relative to the atmosphere) causing air too rush in a. Boil?s Law P1V1 = P2V2 III. This contrasts with the frog Gas Exchange IV. Dalton?s Law of Partial Pressures a. Total Pressure = Sum of Individual Gases V. Each gas independently exerts a partial pressure VI. So in diffusion, each gas follows its own concentration gradient (partial pressure gradient) VII. The pressure of carbon dioxide in the atmosphere is much less than the pressure of carbon dioxide in the body so it flows out VIII. The pressure of oxygen in the atmosphere is much greater than the pressure of oxygen in the body so it flows in Respiratory Pigments I. Combine reversibly with oxygen and increase the capacity of blood to transport oxygen II. Types of pigments a. Hemocyanin i. Copper containing protein found in many mollusks and arthropods ii. Found in hemolyph (not blood) iii. Blue when oxygenated iv. Clear without oxygen b. Hemoglobin i. Oxygen containing pigment that we use ii. Found in almost all vertebrate red blood cells iii. 4 protein chains (subunits) iv. 4 heme groups with iron 1. Iron binds oxygen v.Bright red when oxygenated vi. Dark red without oxygen vii. Hemoglobin experiences cooperativity-when one subunit binds an oxygen molecule?this causes a conformational (shape) change? results in other subunits binding to oxygen more rapidly viii. Bohr Effect 1. Oxygen dissociates (is released) from hemoglobin (Hb) in the presence of H+ ions (low pH) a. O2Hb + H+ ??HbH + O2 2. Increase in CO2 will also cause Hb to give up O2 3. O2 is free to go to cells that need it a. H+ ions are a product of active tissues-tissues need oxygen so they release the ions to signal for the blood to release oxygen ix. O2 transport 1. 97% of oxygen is transported by hemoglobin 2. 3 % of oxygen is dissolved in plasma x. CO2 transport 1. 7-10% is dissolved in plasma 2. 20% combines with Hb in RBC?s 3. 70% is transported as bicarbonate ions in the plasma 4. Carbonic anhydrase-enzyme in red blood cells that speeds up this reaction 5. When CO2 levels are high, reaction goes to the left a. Tissues release CO2 which is picked up by the RBC which converts it to bicarbonate ion 6. When CO2 levels are low, reaction goes to the right III. Respiration is mainly regulated by a. CO2 chemo-receptors (mainly) i. The chemo-receptors stimulate respirator centers in the pons and medulla oblongata b. A drop of oxygen-it stimulates breathing IV. SARS a. In the news b. Severe Acute Respiratory Syndromes c. Causes pneumonia i. Pneumonia causes increased permeability of alveolar walls so the increase in fluid goes into the alveoli? this decreases surface area for gas exchange ii. Can ultimately cause death Osmoregulation and Disposal Of Metabolic Wastes I. These are excretory functions II. Excretion is the removal of metabolic waste (not undigested waste = elimination) III. Wastes include a. Excess water and salts b. Carbon dioxide c. Nitrogenous wastes i. Results from breakdown of amino acids and nucleic acids ii. Excreted in several forms IV. Terrestrial Vertebrate Excretory Organs a. Kidneys-Urea, Uric acid, water (in urine) i. Via liver b. Digestive System-bile pigments (in feces) from RBC Hemoglobin breakdown c. Skin-water (in sweat) d. Lungs-water vapor and CO2 exhaled Urinary System I. Parts of urinary system a. 2 kidneys b. 2 ureters c. 1 bladder d. 1 urethra II. Kidney a. Divided into cortex and medulla b. Renal-refers to kidneys c. Functional unit is the nephron d. Parts of nephron i. Renal corpuscle-consists of 1. Glomerulus (also called glomular capillary) 2. Bowman?s Capsule ii. Renal Tubule-consists of 1. Proximal convoluted tubule (PCT) 2. Loop of Henle 3. Distal convoluted tubule (DCT) a. Leads to a collecting duct e. Blood vessels-Blood flow around the nephron i. Renal artery?afferent arteriole?glomerulus?efferent arteriole? peritubular capillaries?small veins?renal vein f. 3 main activities of the nephron i. Filtration-movement of substances from the blood into the tubule (Bowman?s capsule) ii. Reabsorption-movement of substances from the tubules to the blood iii. Secretion-movement of substances from the blood into the tubules III. Filtration a. Factors that affect filtration i. Afferent arteriole has a diameter larger than that of the efferent arteriole?this leads to increase in hydrostatic pressure in the glomerulus ii. Lots of surface area because the glomerulus is highly coiled iii. Increase in Porosity of glomerulus due to fenestrations (pores) between the endothelial cells of the capillaries iv. Wall of Bowman?s capsule consists of cells called podocytes (specialized epithelial cells; sometimes called foot cells) with foot processes?between these processes are filtration slits b. Podocytes with foot processes and the increase in porosity of the glomerulus (iii. And iv.) Together, make up the filtration membrane c. End result is that almost everything, except cells and large molecules (proteins), is forced out through the filtration membrane and into the Bowman?s capsule i. About 180 L per day is forced out ii. This is 4 times our total body fluid iii. The average person excretes/ urinates about 1.5 L per day IV. Reabsorption a. 65% of reapsorption takes place in the PCT b. Reabsorption is the selective returning back to the blood of about 99% of substances that were forced out c. Things that are reabsorbed i. Water (mostly) ?each day we reabsorb about 178 L ii. Glucose iii. Amino acids iv. Vitamins v.Salts d. These must first pass through the interstitial fluid before they are reabsorbed back into the blood e. Reabsorption is done by active transport and diffusion in the PTC i. Brush border-this increases the surface area f. There is a tubular transport maximum (Tm) i. For glucose ~ 125 mg/minute can be reabsorbed ii. All can?t be reabsorbed when you have diabetes mellitus (type I or II)- that?s why there is a high glucose concentration in the urine V. Secretion a. It is also selective b. Most of it occurs in the DCT c. Both active transport and passive transport are use d. What should be secreted? i. K+ (if it is too high-skeletal muscle, smooth muscle, the heart, and nerves are affected) ii. H+ (to regulate pH) iii. Ammonium ions VI. 2 kinds of Nephrons a. Cortical nephrons i. Have a short loop of Henle ii. Not good for concentrated urine iii. Make up ~ 80% of all nephrons b. Juxtamedullary nephrons i. Able to produce urine with a higher osmolarity (osmotic pressure) than most body cells ii. 2 features concerning juxtamedullary nephrons 1. Counter current mechanism 2. Gradient of osmotic pressure in the interstitial fluid surrounding the nephron a. Cortex-lowest osmotic pressure b. Medulla-highest osmotic pressure VII. Looking at Reabsorption Again a. As fluid moves through the tubules, it gets reabsorbed back into the blood (from the interstitial fluid) b. Path i. Bowman?s capsule ii. PCT (concentration is 300 mOsM/L = same as blood) 1. Active transport of Na + 2. Cl- follows because of the charge 3. Then water follows because of osmosis iii. Descending limb 1. Filtrate (becomes the urine later) is being concentrated 2. Osmosis of water because of the higher osmotic pressure of the interstitial fluid 3. Descending limb is not permeable to NaCl iv. Ascending limb 1. Filtrate is being diluted 2. Na+ is passively, and then actively transported out 3. Cl- follows 4. Ascending limb is not permeable to water 5. From the ascending limb, the fluid enters the v.Distal Convoluted Tubule 1. Filtrate is more dilute than interstitial fluid 2. This dilution allows us to make very dilute urine (~100mOsM) 3. At the DCT- a hormone can act a. Aldosterone i. Mineralocorticoid ii. Made in the adrenal cortex iii. Stimulates the reabsorption of Na+ iv. Without aldosterone, we?d loose ~ 2 % of our Na+ per day?this leads to death because we cannot replace the Na+ fast enough vi. Collecting Ducts 1. This is where the urine can be concentrated- 140mOsM 2. Aldosterone a. Increases the reabsorption of Na+ 3. Antidiuretic hormone (ADH) a. Secreted by posterior pituitary b. Allows water to be reabsorbed by making collecting ducts more permeable to water 4. Urea is also reabsorbed at the collecting ducts, which contributes to the high osmotic pressure of the interstitial fluid vii. Leaving the Kidney 1. The filtrate (urine) is usually hypertonic to the blood and isotonic to the medullary interstitium VIII. Key Points of System a. Diffusion only requires a difference in concentration b. Ascending and Descending limbs are different i. Run in opposite directions (counter current) ii. Differ in their permeabilities 1. Descending limb is permeable to water 2. Ascending limb is permeable to salt Kidney Disease I. Kidney disease is a decrease in function of kidneys II. Can happen because of a. Infections b. Decreased blood delivery (arteriosclerosis c. Diabetes III. Common symptoms a. Increased amount of protein in urine b. Edema-swelling due to i. Increase in Na+ in the tissue ii. Increase in Nitrogenous wastes c. H+ in the tissue d. Edema and H+ in the tissues can lead to a coma or death e. Urine becomes isotonic-can?t concentrate or dilute it f. Don?t notice until more that 75% of nephrons aren?t working g. Treatment?Dialysis = hemodialysis i. 3 times a week, 4-6 hours ii. Ambulatory-can get treatment inserted in you so you can go home h. Used paratoneum (part of body) as dialysis membrane Biodiversities I. Definitions a. Evolution-the accumulation of inherited changes within populations over time b. Population-a group of individual of one species that live in the same geographical area at the same time II. Theories a. ET b. Creationism i. Immutable-things are created a certain way and they don?t change ii. Supreme Being is the creator iii. This theory is not testable; it is based on fate iv. This was the only theory for millions of years c. Evolution i. Lucilio Vanini-said that man descended from apes?he was burned at the stake (1619) ii. Galileo-said we are not the center of the universe Darwinian Evolution d. Darwin never called in evolution e. Organisms go from Simple?Complex f. Evolution is the accumulated inherited changes in a population over time i. Species is not Immutable g. Darwin?s contribution was not the idea of evolution, but the mechanism for evolution?Natural Selection i. Majority of people already believed in evolution before Darwin h. Darwin was influenced by earlier thinkers i. Da Vinci-things had changed ii. Malthus-the population?s can?t increase without limit, there must be a struggle for existence iii. Lyell-before him people though the earth was only 6,000 years old?he said it was much older and it changed dramatically over time via erosion and volcanoes 1. Darwin thought that if the earth can change, so can species 2. If the earth was old, this gave time for change iv. Lamarck-species came from earlier, more primitive forms (he was correct, and Darwin agreed with this) Lamarck was wrong in thinking that the mechanism was though ?acquired traits? 1. Ex: giraffe got a long neck because it stretched a little more each generation and the parent passed in down to offspring 2. This can?t be true because we have been doing circumcisions for years but are still born with a foreskin III. Darwin a. Didn?t do well in school b. Rich family c. Parents sent him on a 5 year voyage to the Galapagos Islands on the HMS Beagle d. He was the ship?s naturalist e. Got in a fight with the captain, only one in his social class, and had no one to interact with giving him lots of time to think f. Saw lots of different species, which gave him ideas about evolution g. Book was ?The Origin of Species? h. Natural Selection-Individuals are born with traits that make them best adapted for their environment are also the ones most likely to survive (survival of the fittest) and are most likely to successfully produce offspring i. Arguments against natural selection i. Overproduction 1. Every organism produces more offspring than could actually survive 2. Population increases geometrically-more over time ii. Limits on Population Growth 1. Growth is logarithmic, not exponential (Mathius) 2. Resources are limited?struggle for survival 3. Most fit survive-these are the ones most adapted to the environment iii. Variation 1. Individuals of a species vary (height, color, etc) 2. * Variation is the raw material for evolution 3. Bell curve (with mean, mode, etc) a. Could be skewed-ex: skin color 4. Darwin didn?t know where variation came from-didn?t know about genetics and mutation iv. Differential Reproductive Success 1. Those individuals that possess the most favorable combinations of characteristics are more likely to survive and reproduce 1. Males are usually bigger than females 2. The biggest male usually has reproductive success because he is a better fighter 3. Best adapted individual will produce the most offspring and therefore pass on the genes 4. Survival and reproduction are not random a. Favorable traits are passed j. Evidence that supports the theory of evolution through natural selection i. Artificial Selection 1. Farmers have been doing it for 100?s of years a. Only allow the best individuals to breed 2. Artificial because man decides what traits will be selected 3. Hens-increased egg production by 500% in 30 years a. Only hens at the high end of the bell curve for the amount of eggs laid were chosen to reproduce 4. Broccoli, cabbage, kohlrabi, Brussels sprouts, etc. all artificially produced from the mustard plant 5. Slight variations are preserved 6. Species are not immutable ii. Fossil Records 1. 99.9% of all species that ever existed are extinct 2. Carbon dating-technique used to determine the age of a fossil 3. We never found fossils out of order in the rock sediments (always corresponded with carbon dating and other proofs) 4. Horse a. 50 million years ago, it was the size of a dog i. Used to hide ii. Browsers- looked for food iii. Environment changed iv. Ice Age caused the forest to be eliminated v.In the grasslands the horse couldn?t hide vi. Learned to run vii. Grazers-started to eat grass, hay, etc. viii. Needed different teeth, legs, feet, etc. ix. This progressions not really linear-it just happens to be the only one of many species that survived iii. Comparative Anatomy 1. Homologous Structures a. Structures with different functions derived from the same structure in an common ancestor b. Evidence of divergent evolution c. Animals may have the same bones, but modified versions d. Evolution modifies pre-existing structures? Preadaptation-a novel evolutionary change in a preexisting biological structure that enables it to have a different function; feathers, which evolved from scales represent a preadaptation to flight 2. Homoplastic (Analogous) Structures a. Look similar and/or have similar functions, but are not derived from a common ancestor b. Ex: insect wing?membrane, bird wing?bones c. Convergent evolution-doesn?t mean that two species become one, their structures just become more alike d. Sea animals developed the same body shape?birds, fish, mammals, reptiles e. The environment demands the same needs on very different species 3. Vestigial Structures a. Nonfunctional b. Remnant of the structures that used to be used c. Ex: a python still has a tiny vestigial femur i. The genetic info is still their, it?s just not expressed, it will eventually be lost d. Ex?s in humans i. Nipples on men ii. 3rd molar (our diets have changed?mouths are now smaller) iii. Nictitating Membrane-inside of eye iv. Segmented abdominal muscles (only essential for 4-legged animals) v.Caudal vertebrate-tail bone vi. Hair on the body iv. Comparative Embryology 1. Early in embryo development-all animals are very similar v.Biogeography 1. The study of past and present geographic distribution of species 2. Galapagos and Cape Verde Islands have very similar environments, but very different species, however, the species are similar to those on their main lands vi. Molecular 1. DNA sequencing-we can see differences in the codes of the nucleotide bases a. The more differences = the more time since they diverged from a common ancestor b. Phylogenetic tree i. Phylogeny-evolutionary history of a group of related species 2. We can now get DNA from teeth of extinct organisms 3. Amino acid sequencing a. Supports structural/morphological evidence b. Tells us how many years ago we diverged 4. As we go farther into the past, living organisms are less and less similar to life today vii. Imperfect Adaptation 1. Ex: humans were not well designed for walking upright a. We came from 4-legged animals in which it was a good design b. Evidence = back, knee, and foot pain c. We evolved to walk upright so our arms would be fee to grasp and take things (selection pressure) d. Natural selection has to work with what is available-preadaptation 2. Ex: Bird feathers from reptile scales 3. Ex?s in humans: a. Varicose veins b. Hernias c. Hemorrhoids d. Child birth e. Learning to walk viii. Direct Evidence 1. Not a lot because evolution is over time 2. Ex: Insect resistance to insecticides a. In the beginning, insecticides killed almost all of the insects b. Some had a gene for resistance (detox., thick skin, etc.) c. This slight variation became advantageous d. After many generations, almost all will have the gene because the other die so the genes are contributed disproportionately k. All the types of evidence tell the same story i. All are self-supporting-no disagreement-a mosaic of evidence ii. Whatever question we ask, we always get the same answer from each part of the evidence l. ?Evolution is a process of adaptation to the environment. Natural selection acting on variation (preserving if beneficial, removing if detrimental) is the means by which this adaptation occurs.? Darwin i. Darwin said that evolution is random 1. Implies that humans are not the inevitable product for large brains 2. This contradicts religious beliefs?stirred up controversy 3. Darwin used to be a creationist, but the evidence for evolution and natural selection is overwhelming Population Genetics and Microevolution I. Background a. Hardy-Weinberg Equation-predicts populations that are not evolving? gives a starting point so you can measure the change in a population b. Population-all individuals of the same species living in a particular area at the same time. They share a common gene pool c. Gene Pool-pot of alleles-total genetic information of a population (sum of all alleles of all genes in a population d. Natural Selection acts on a population e. How do populations evolve? i. Variation is the raw material for selection ii. No evolution can occur without variation f. Darwin knew nothing of genetic; Mendel knew Genetics g. Genetics and Evolution converged in The Synthetic Theory of Evolution h. Microevolution i. Small changes in one or a few genes (not speciation?may occur over time) ii. Short-term adaptation of populations to change in the environment iii. Result of a change in allele frequency i. Macroevolution i. Long-term formation of different species ii. Will result in big changes in a species or the development of a new species all together iii. Comes from microevolution j. Evolution-change in allele frequencies over time i. If allele frequencies don?t change, there is no evolution k. Alleles are haploid l. Allele frequencies must add up to one m. Frequency change ? evolution n. Frequency stable ? genetic equilibrium Hardy Weinberg Equation o. Derivation i. Sperm penetrates the egg ii. Each gamete is haploid recessive or dominant iii. Take a heterozygous cross p. Hardy-Weinberg Equation describes a population in equilibrium-not evolving-evolution occurs when something disturbs the equilibrium q. Baseline r. p2+2pq+q2=1 p + q =1 s. Examples i. How many people are ?carriers? (Aa) of albinism if albinism is recessive and 1 in 20,000? ii. What proportion of a mouse population will have white coats? t. Gene frequencies are inherently stable u. Hardy-Weinberg Equation predicts changes in offspring gene frequencies (permits tracking changes from generation to generation) v. The equation provides no basis for evolutionary change, but allows us to see if there are departures from the prediction over time w. Evolution occurs only when something disturbs the genetic equilibrium x. Gene frequencies don?t change by themselves y. Describes an idealized population that is not evolving (genetic equilibrium) i. Ideal?doesn?t actually exist z. Under certain conditions population allele frequencies are in genetic equilibrium 5 Conditions necessary for Hardy-Weinberg Genetic Equilibrium 1) No mutations i. Never true ii. Rate may be very low 2) No migration in and out of the population i. No sex between 2 populations ii. Almost never true 3) Population size must be infinite or very large i. Never infinite, but can be large 4) Mating is random i. Mating is almost never random 5) No selection i. Usually some is going on ii. Only can be true for short periods of time aa. All conditions cannot be true all of the time. That?s why there are never ideal conditions in nature bb. Since these tell you that evolution is not happening?the opposites are the causes of evolution cc. So what good is Hardy-Weinberg since it only describes impossible populations? i. Because deviations between idealized Populations and real populations measure the extent of evolution. Variation dd. Raw material ee. Processes causing deviations from the HW equilibrium 5 causes of evolutionary changes (departures from H-W equilibrium) 1. Mutation * 1) The ultimate source of variation because it creates new alleles 2) Must be combined (with natural selection) to be powerful 2. Migration 1) Introduces new alleles into a population 3. Genetic drift 1) Evolution by chance 2) Small populations 3) Survival of the luckiest (not the fittest) 4. Sex 1) Meiosis reshuffles the gene pool 5. Natural selection * 1) Acts on variation with conjunction with something else Mutation-1 i. DNA makes mistakes in the genetic code ii. Can be spontaneous or induced (radiation makes breaks in DNA) iii. Random-we can?t predict what the mutation will be even if we induce it iv. Mutated parent gene affects the offspring and not the parent 1. The sins of the fathers are visited upon the children v.Almost always bad vi. Ultimate source of NEW variation vii. Rare=not common enough to change by itself-must work with natural selection viii. NO MUTATION = NO LIFE ON EARTH ix. We must adapt x. Errors in DNA code 1. Deletion 2. Duplication 3. Inversion xi. Neutral Variation-a mutation could be neither harmful nor beneficial (rare) xii. Most mutations are harmful and therefore selected against because any population has been through generations of natural selection, so they are already well adapted. Migration-2 xiii. Variation because populations exchange genetic information?gene shift via sex ff. Genetic Drift i. Evolution by chance ii. Survival of the ?Luckiest? iii. Example 1. Founder Effect-different gene pool because only some genes did not get transported 2. Independent of selection 3. May not be favorable 4. Sampling error-the smaller the surviving sample, the less it represents the whole population 5. There is no genetic drift if a population is large because the sampling error is minimal 6. Genetic Bottle Neck 1) Ex: the cheetah population has almost no genetic variation gg. Sex and Non-random mating i. Why is there sex? 1. It really doesn?t make any sense because you only pass on 50% of your genes; asexual reproduction passes on 100% 2. Sex is danger?lots of competition, cannibalism in spiders, fireflies make their presence known to predator 3. There is sex because Meiosis provides variation! Variation is needed for life on earth 1) Recombination occurs in meiosis?like shuffling a deck of cards ii. Sex is almost always non-random because some individuals are more successful 1. Assortive Mating 1) We tend to mate with those like us so there are more homozygous traits 2. Inbreeding 1) Prefer to mate with those you are more closely related to 2) Plants are more prone to this 3) Male animals tend to leave when they are more sexually mature 4) Inbreeding Depression-the phenomenon in which inbred offspring of genetically similar individuals have lower fitness than non-inbred individuals hh. Natural Selection i. The main cause of evolutionary change ii. Does not create variation?acts on it iii. Eliminates deleterious mutations iv. Acts on the whole organism v.Evolution is not a property of individuals vi. Natural Selection acts on the individual vii. 3 types of natural selection 1. Stabilizing selection 1) Selection that favors the intermediate phenotype?promotes phenotypic uniformity 2) Actually prevents evolution 3) Works against extremes 4) Most common type of natural selection 5) Common traits are favored 6) Reduces variation 7) Favors the ?status quo?? ..until the environment changes 8) Ex: babies with very high and very low birth weights have high mortality rates so the average weight is selected for 2. Directional Selection 1) If the environment changes, then one extreme may be favorable?maximum fitness 2) Selection that favors extreme phenotypes?promotes phenotypic differences 3) Curve has to shift to the new optimal fitness 4) It then restabilizes 5) This happens in Artificial selection: we choose for only the top portion to breed, so they become the average 6) Adaptation i. Structural (morphological), functional (biochemical), or behavioral modifications that improve survival/reproduction ii. These individuals are more likely to pass their genes on to the nest generation (more fit) 7) EVOLUTION HAS NO FORESIGHT!!! 3. Disruptive Selection 1) A type of directional selection 2) Selection that favors individuals at both extremes of a trait 3) This can result in divergent evolution 4) It is a major cause of speciation 5) Selection against the mean Speciation and Macroevolution I. What is a species? a. We usually talk about genus and species together b. Species are the most basic unit of evolution (Kingdom, Phylum, Class, Order, Family, Genus, Species) c. There is no set definition, but we will look at two: i. Morphological 1. Structural differences 2. We have described more than 1,370,134 species this way 3. Problems and Limitations a. Polymorphism-same species look different due to variation b. Sexual Polymorphism-males and females in the same species look very different 4. Because of these, we can not identify species by this definition alone ii. Biological Species Concept 1. Devised by Enst Mayr 2. Organisms must have evolutionary independence 3. Species-populations that are reproductively isolated from other species 4. Must interbreed to produce viable (living) and fertile (not sterile) offspring?cannot be a dead end 5. No gene flow between species 6. Problems and limitations a. Relevant only for sexual organisms b. Under artificial conditions, different species can interbreed i. Ex: horse and zebra produce sterile offspring ii. Ex: genus Canus (dogs) will interbreed and form fertile and viable offspring, but? they will only mate in a cage, not in nature II. How does a species stay a species? a. Reproductive Isolation i. Prevents two species from producing fertile hybrids III. How do species stay Reproductively Isolated? a. There are barriers to gene flow b. Gene flow encourages homogeneity c. We could not separate species without homogeneity d. 2 Barriers to Gene Flow i. Pre-zygotic barriers-before the sperm and egg fuse 1. Behavioral Isolation-recognize own species by behavioral displays (females are selective because eggs are expensive and males tend not to discriminate) 2. Communication barriers a. Auditory (ex: cricket songs) b. Chemical (ex: mosquito antennas) c. Visual (ex: firefly lights) 3. Temporal Isolation-species mate a different times (of day or of season) and this reduces the opportunity for mistakes 4. Mechanical Isolation-genitalia mush physically fit together (lock and key)?structural compatibility 5. Habitat Isolation-different species mate in different locations (ex: beetles: on trees and on ground) 6. Gametic Isolation-if all else fails and the species have intercourse then this does not allow the egg and sperm to fuse ii. Post-zygotic barriers-gametes fuse; some species are so similar that they make the mistake 1. Hybrid Inevitability-usually spontaneous abortion; if offspring is born, it is usually very weak and dies early 2. Hybrid Sterility-viable offspring, but they cannot reproduce a. Ex: a horse (62 chromosomes) mates with a donkey (64 chromosomes) they give birth to a mule (63 chromosomes-odd number, cannot pair) b. Meiosis fails IV. How do new species arise from existing species? a. Reproductive Isolation Mechanisms?Interrupted gene flow (gene flow promotes homogeneity) i. Allopatric Speciation-speciation that occurs when one population becomes geographically separated from the rest of the species and subsequently evolves 1. Gene flow interrupted because of migration is inhibited 2. Barriers and Islands a. Rivers and canons b. Mountains c. Land in a sea of water d. Water in a sea of land e. Trees in a sea of grass f. Coolness in a sea of warmth g. Warmth of coolness 3. Results from changes in the environment 4. Summary a. Population contiguous-gene flow across the entire population b. Interrupted by a barrier-prevents gene flow c. Mutation comes up in one of the split populations?only the one population is affected?genetic differences accumulate d. Reproductive Isolation and Speciation (evolutionarily independent populations)-even if reunited, there will be no gene flow 5. Geological Isolation?gene flow interrupted?reproductive isolation?speciation ii. Sympatric Isolation-formation of a new species within the same geographical region as the parental species (no geographical isolation) 1. Very common in plants 2. Rare in animals 3. Shift in Host Speciation ?Ecological isolation ?reproductive isolation 4. Example: Apple Maggot Fly a. Flies eat Hawthorn b. Environment changes?apples are planted c. Variation in population i. Some prefer apples ii. Some prefer Hawthorn d. These flies mate on the fruit e. No more gene flow between populations 5. Example: Example: In plants a. Polyploidy-many chromosomes; instantaneous speciation via spontaneous increase in chromosome number-usually results infertility of offspring i. N=haploid ii. 2N=diploid iii. >2N=polyploidy b. Must be hybridization (no hybrid sterility) c. Must be spontaneous increase in chromosomes d. Must be self-fertilization e. Polyploidy is heavily used in agriculture i. We can induce/generate new species ii. Hybrid Vigor-better than parents iii. 80% of plants are due to polyploidy 6. When environment changes, some variants may be favored by selection?fitness is redefined 7. Review a. Mating is non-random based on habitat preferences b. Genetic differences accumulate c. One population becomes two populations, and eventually leads to speciation V. How fast does evolution occur? RATES OF EVOLUTION a. Gradualism vs. Punctuated Equilibrium i. Theory of Gradualism Equilibrium 1. It is the idea that evolution occurs by a slow, steady accumulation of genetic changes over time 2. Darwin?s Idea 3. Problem?discontinuity in fossil records a. There are missing pieces b. Explanation-we just haven?t found all the fossils yet c. In general, fossils do not support this theory (too many instances) ii. Theory of Punctuated Equilibrium 1. The idea that evolution proceeds with periods of little or no genetic change, followed by very active phases, so that major adaptations or clusters of adaptations appear suddenly in the fossil record 2. Species remain unchanged for long periods, after which they change abruptly in response to sudden changes in the environment 3. Proposed by Steven J. Gould 4. This theory seeks to explain a. Discontinuity in fossil records b. Rate of evolutionary change iii. Both theories are true 1. Fast change in environment?fast change in species 2. Slow change in environment?slow change in species VI. Patterns of Evolution a. Adaptive Radiation i. It is the evolution of a large number of related species from an unspecialized ancestral organism ii. Diversification?Adaptive Radiation iii. Explosion of speciation iv. Many ecologically diverse species from one ancestral species in a short period of time v.This is where all pieces come into play vi. Example of adaptive radiation-Darwin?s Finches 1. Partitioning of food resources to reduce competition 2. Migration 3. No gene flow 4. Different mutations 5. Small founder populations 6. Environments different with unexploited niches a. Leads to the different selection pressures vii. Very rare viii. Most of the time, when a small population is in a marginal environment, that population dies ix. Example of Large-scale adaptive radiation 1. Evolution of wings in insects a. Wings were a random mutation that were selected for b. Preadaptation-origin of evolutionary novelties from pre-existing structures b. Extinction i. The ultimate form of evolutionary change ii. The elimination of a species; occurs when the last individual member of a species dies iii. This is the reason why there are no 3 billion different species alive today iv. 99.99% of species that ever lived are extinct v.We now have 1.5 million species today vi. Extinction is due to the introduction of novel competitors, predators, parasites, and environmental changes vii. Two types of extinction 1. Background extinction a. Slow b. Small scale c. Due the inability to adapt i. To climate (habitat loss) ii. To novel predators iii. To novel competitors d. Example: mammoth was hunted by humans to extinction 2. Mass extinction a. Abrupt b. Large scale c. Sometimes good d. Example: dinosaurs-gave mammals a chance for adaptive radiation e. There have been 5 major events over the last 500 million years viii. Current background extinction rate is greater than 40 times higher than the pre-human rate 1. Humans cause many species to go existence 2. This leads to a loss of biodiversity ix. Background extinction due to Habitat loss 1. We loose 2% of the rain forests each year 2. In NJ, the pine barrens are being lost x. Alien Species Act of 1996 1. Introduced species are leading to extinction of other species VII. Evolution: Theory or Fact? a. BOTH i. Fact: millions of fossils, DNA,etc. show that species are not immutable ii. Theory: the mechanisms that cause evolution b. All scientific knowledge is theoretical c. Nothing in biology makes sense without evolution Ecology I. Ecology-a discipline of biology that studies the interrelations among living things and their environments Population Ecology II. Population ecology is the study of how populations change over time X. Distribution a. Spacing of a population b. There are two types of populations i. Static 1. There are three ways static populations can be distributed a. Clumped (patchy, aggregated, usually around resources) b. Uniform (mutual repulsion; often in aggressive species) c. Random (very rare because resources are not random) 2. Clumping is most common 3. Behavioral patterns often lead to clumping 4. Clumping can be a defense mechanism 5. Static-snapshot in time 6. A static population is not very realistic ii. Dynamic 1. Individuals come and go 2. Series of Static populations can show a dynamic one XI. Reproductive Potential a. Limits the population b. All organisms produce more offspring than can survive XII. Population Models a. 2 opposing forces i. Natality (b) ii. Mortality (d) b. 3 Phases of a population that a model must consider i. Growth ii. Stability iii. Decline c. Models i. Growth rate (r) 1. Problem-it only measures static populations, and it doesn?t take time into consideration ii. Exponential Growth 1. Problem-it is unrealistic because it assumes that a population grows forever without restriction 2. It is impossible because of limited resources, space, waste build up, etc. 3. The growth rate is proportional to density 4. Most populations have a period of exponential growth 5. As density increases, growth rate increases 6. This equation only considers growth, not stability and decline iii. Logistic Growth 1. ?S? curve-sigmoidal curve 2. Carrying Capacity-the maximum number of individuals that the environment can support? K 3. Now we have growth and stability 4. Growth slows as the population approaches K 5. N = K when b ? d = 0 or b = d?no growth 6. Resources and populations are finite so populations must stabilize 7. K is not a constant; it can change based on the environment 8. Logistic model recognizes growth and stability, but not decline, so it is still not realistic d. What factors Regulate Growth? i. K (mortality) is the most important in regulation XIII. Population Regulating Mechanisms (for this purpose, mortality is means that the genes don?t get to be passed on) a. Density-Independent Mortality Factors i. Environmental factors that impact a population are unaffected by the number of individuals in that population ii. No correlation between density and growth iii. These factors have the most impact on a population undergoing exponential growth iv. Abiotic (physical) environment v.Ex: Flood, Lake dries up, Temperate (more subtle) causing massive deaths, regardless of the size of the population b. Density-Dependent Mortality Factors i. Environmental factors that affect the ability of a species to thrive as a direct result of the number of individuals ii. Population growth is suppressed as the density of the population increases iii. Increase in death rate, decrease in birth rate iv. Operates by negative feedback via death and birth rate v.Biotic Environment vi. Ex: disease and parasites-because as the population increases, transmission is made easier vii. Ex: predation-population regulated by predator, the predator is negative feedback viii. Ex: Competition-when organisms reduce the fitness of each other by using or defending a shared resource 1. Resources include food, water, mates, mating sites, sunlight, etc. 2. Everyone or someone losses in competition 3. Two types a. Contest Competition- (win or loose) dominant individuals obtain limited resources at the expense of others?leads to some of the population doing well and the others dying or not reproducing (reduced fitness for some, enhanced for others) b. Scramble Competition-all individuals in a population ?share? the resources equally?this only works for relatively small populations?an increase in density is bad for all because resources become depleted?can lead to reduced fitness for all i. There is selection pressure for contest competition because: 4. There are mechanisms to reduce competition a. Ex: Insect metamorphis-different forms have different needs so there is not as much competition for one resource XIV. Reproductive Strategies a. Introduction i. Survivorship curves-distribution of deaths 1. 3 Types a. Type I i. High survival early in life ii. Heavy mortality late in life iii. Ex: Elephant, humans iv. Due to parental care v.Have few offspring vi. Social organisms vii. Pair Bonding 1. No mating season 2. Love is a chemical imbalance: increased dopamine levels and lower seratonin levels generate hormone imbalance that elicits a euphoric feeling (also causes jealousy) viii. K-strategists b. Type II i. Similar to Type I ii. Some parental care iii. Ex: squirrels c. Type III i. Low survival early in life-high juvenile mortality ii. Heavy mortality early in life iii. Ex: Clams, beetles, dandelions iv. Colonizers-usually hard to find a place to colonize v.No parental Care vi. Large number of offspring vii. r-Strategists-large growth rate b. Reproductive Strategies: Theory of r and K selection i. Different environments select for different reproductive strategies ii. Two types 1. r-strategists or r-selected species a. Goes through bust and boom b. Unstable, unpredictable, short-lived environments i. Ex: mud bar in a lake, forest fires, agricultural plowing c. Good Colonizers (pioneer species), but poor competitors d. Depend on Abiotic environment e. Clock is ticking?must reproduce fast f. Resources are not limited in these environments (for a little while) g. These are type III life spans h. Well defined by exponential equation i. High intrinsic growth rate j. Tend to be small organisms k. Pests tend to be r-strategists l. High reproductive potential, but never reaches it 2. K-strategists or K-selection species a. Population stays relatively constant b. Stable, predictable, long-lived environments c. Good Competitors d. Tend to be highly specialized e. Can throw out r-strategists f. Density dependent g. Tend to be large organisms h. Endangered species ten to be K-strategists i. Abiotic environment is less important j. Resources are limited because of intense competition k. These are Type I life spans l. Population size is maintained near carrying capacity (K) m. Well defined by logistic equation n. Small reproductive potential c. Dispersal (Migration) i. To reduce scramble competition, you can emigrate (leave) ii. Emigration is usually due to depleted resources 1. Ex: Irish lived on potatoes?potato blite disease wiped out potatoes?many people starved, others went to US?there are now more Irish in the US than in Ireland a. No genetic drift b. No sampling error d. Human Population Growth i. We are in an exponential growth period ii. Our population will stabilize or crash and burn iii. We changed our Carrying capacity (K) Community Ecology I. Interspecific relations II. Autotrophic Diversity a. All energy comes from the sun b. 2 types of autotrophs i. Photoautotrophs ii. Chemoautotrophs-not based on sunlight, utilizes H2S III. Community Interactions a. This is the types of relationships between organisms (or populations) b. Types i. Predation (Antagonism) 1. Predator-Prey 2. Plant-Herbivore + - one benefits, other suffers 3. Parasite-Host a. A good parasite doesn?t kill host ii. Competition - - both suffer iii. Commensalism + 0 one benefits iv. Mutualism (symbiosis) + + both benefit Predation (+/-) c. Adaptations to Avoid Predation i. Behavioral 1. Ex: live in large groups ii. Chemical 1. Ex: milkweed has toxins to kill or taste bad to predators iii. Morphological 1. Ex: turtle?s shell, rabbit?s ears, eyes on the sides of the head iv. Crypsis- camouflage 1. Ex: white rabbit in a snowy environment d. Coevolution i. Reciprocally induced evolutionary change between species ii. Evolutionary ?arms race? 1. Ex: plant evolves toxin, caterpillar evolves detoxin 2. Ex: predator evolves speed, camouflage, etc. to adapt to prey a. Speed is a pursuit b. Camouflage is an ambush-catch prey by mechanism other than chasing e. Mimicry i. Batesian Mimicry 1. Ex: wasp and hoverfly look the same, but a hoverfly is not dangerous and it tastes good to birds?birds wont eat it because it mistakes it for a wasp 2. Elements a. Model must be dangerous or upalatable b. Mimic must be harmless c. Model must be more common than the mimic d. Requires the predator to learn 3. Aposematic Coloration-tells predators that this organism is DANGEROUS a. Ex: monarchs, poisonous arrow frog, brightly colored snakes b. Don?t want the predator to make a mistake because then everyone looses?neither organism lives ii. Mullenan Mimicry 1. Ex: four species of butterfly that all look alike and are all toxic 2. This reinforces predator learning 3. Also causes predators to learn faster 4. Ex: monarch and viceroy both look alike and make birds ill 5. Due to convergent evolution f. Lotka-Volterra Predator-Prey Model i. Always a delay between prey increase and predator increase ii. Predators keep the population stable Competition (-/-) g. Cost to both-everyone looses h. Two types i. Intraspecific-competition within one species ii. Interspecific-competition between 2 or more species 1. Niche a. Fundamental niche?theoretical b. Realized niche?actual (because of competition) c. In a fundamental niche, there is no competition, but in reality there is always competition d. Gause?s Principle of Competitive Exclusion i. No two species can completely ecologically overly each other?can?t do the same thing at the same time ii. Experiment with bacteria alone and living with another species 1. Sharing of niche results in reduced fitness e. How do species with similar niches coexist? i. Increased differences between species where they are sympatric ii. Will evolve to reduce competition in communities that coexist iii. Ways 1. Character Displacement a. Divergence in traits of species living in the same geographical area b. Ex: Darwin?s Finches IV. Same beaks when on separate islands (allopathic) specialization-both are on the same island (sympatric) a. Evolution favors physical specialization that reduces competition 1. Resource or Niche Partitioning a. Spatial Partitioning-Subdividing the habitat spatially-take different niches b. Temporal Partitioning-use resource at different times Commensalism (+/0) a. One benefits and one is unaffected b. Ex: rainforest?orchid grows on a tree to get photosynthetic advantage (over being on the ground), but the tree is unaffected c. Often evolves into mutualism Mutualism (Symbiosis) (+/+) d. Intimate long-term relationship e. Advantageous for both partners f. Usually, one can hardly live without the other (intimate) g. Ex: Nitrogen fixing bacteria lives on plants and provides the plant with nitrogen while the plant provides nutrients and protection How do communities change over time? h. Because the planet is always disturbed i. Ex: lava, islands forming, rocks falling, fires, lakes dry up, fields plowed j. These are vacuums-need to be filled with communities k. Succession i. Replacement of one community by another in a predictable sequence ii. Each stage prepares the way for the next iii. Nature is very resilient because of succession iv. Climax 1. Respiration(R)=GPP 2. Not every community reaches it?s climax v.Two stages of succession 1. Terrestrial a. Primary Succession i. Area is disturbed and all life has been wiped out ii. Bear rock where nothing has gone before iii. Lichens (r-strategists) colonize the rock (only when it?s wet)-produce acids-erode rock-make soil iv. Next moss comes in and lichens are replaced 1. Easy for debris to collect 2. Gradually forms a thick mat that allows v.Thick mat allows grass and ferns to grow because they can anchor into the moss vi. Next come herbatious plants-they grow and real soil forms (These are perennials-grow and die every year to accumulate soil) b. Secondary Succession i. Soil is already in place from primary succession ii. Biomass (dry weight of all plants and animals) and species richness increase as succession proceeds iii. As vegetation (producers) change, animals (consumers) change-completely dependent iv. Get short (crab) grass first that send out seeds (r-strategists) v.Tall grass (K-strategists) comes in and out competes/replaces short grass (they compete for the key resource-sunlight) vi. 5th year-then comes shrubs-out compete tall grass vii. 10th year-then comes pines 1. They don?t allow an understory because they block the sunlight 2. Nothing can compete-not even own seeds viii. Then comes oak-hickory trees?they start in the understory because they can withstand shade?eventually outgrow and replace pines ix. Humidity and soil moisture goes low?high x. Biomass increases because K competitors tend to be bigger xi. Species richness increases because you get more niches-leads to more species?more complex food web 1. Does species richness improve community stability? YES xii. Succession is faster in tropical climates xiii. Succession is always interrupted, so it is always starting over and changing?constant cycle (may not make it to climax before interrupted) 2. Aquatic a. Oligotrophic i. Young ii. Deep iii. Low nutrients iv. Little vegetation v.Low plankton b. Europhic i. Old ii. Shallow iii. High nutrients iv. High plankton v.Eutrophication vi. Human activities accelerate eutrophication vii. Humans can also artificially maintain oligotrophic lakes?acidic rain?high pH?no life in lake (sterile) vi. Characteristics of Succession 1. Species composition changes r?K 2. Populations tend to be r-selected early and K-selected later 3. More specialization?increase in diversity 4. Increase in total biomass and species richness 5. Food webs and ecosystems become more complex Ecosystems I. Definitions a. Ecosystem-sum total of abiotic environment and biotic communities in a given area b. Biosphere-all the earth?s communities i. Then shell of life on earth ii. Self sufficient iii. Closed system except we need solar radiation (sun) II. Energy flow a. Energy from the sun (potential energy) is converted to usable energy by plants b. Tropic levels i. Primary Producers-plankton, plants, etc. ii. Primary Consumers-herbivores iii. Secondary Consumers-carnivores iv. Top Predators-carnivores c. Thermodynamics i. First Law-energy is constant; it cannot be created or destroyed, only transformed ii. Second Law-entropy is always increasing; when energy is transferred there is a ?loss?-energy is dissipated d. Energy Transfer flow is linear (non-cyclic) e. ¼ reflected, ¼ absorbed, ½ gets through to the plant?5% of that is reflected so only 45% has potential to be used, but we don?t use most of it i. 0.1% of energy is fixed-converted to be useful-chemical bonds f. The extra is not wasted-it heats the earth and sustains life g. Inefficiencies in energy transformation result in a ?pyramid of energy? h. Disasters invert the pyramid?will collapse i. Ecology Efficiency-the percent of energy that is available to the next tropic level? 5-20% (avg. is 10%) i. INEFFICIENT j. That?s why meat costs more than bread-if we ate just bread and removed the middle-man, we?d be 100% more efficient k. Pyramid of Biomass i. In all pyramids, one tier supports the next l. Productivity of an Ecosystem i. NPP-Net Primary Productivity-usable (spendable) energy, available to be utilized for the next tropic level ii. Respiration-the expense iii. GPP-Gross Primary Productivity-all possible energy 1. NPP + Respiration (primary producers)=GPP 2. NPP=GPP-R iv. These vary in different ecosystems v.NPP is highly variable 1. Highest in tropics 2. Lowest in desserts vi. Expressed in unit g/m2/yr 1. g-grams of carbon (because photosynthesis makes it into glucose) III. Keystone Species a. Ex: Alaskan Sea Otter i. 1970 survey-strong an increasing population ii. 1993 survey-50% decline iii. 1997 survey-90%n decline iv. Why? 1. Starvation 2. Emigration 3. Habitat decline 4. Pollution 5. Disease 6. Reproductive failure v.Actually, it was a little of each, but mostly due to a novel predator-killer whales vi. Killer whales ten to feed on seals and sea lions, but they eat so much that a switch of only a few to otter will have a huge impact vii. Cascade of events 1. Area was overfished-fish population declined 2. Seal population declined as a result 3. Whales didn?t have enough seals to eat so they switched prey to otters 4. Otters population declined 5. Otters eat sea urchants 6. Sea urchant population explodes (density dependent mortality) 7. Sea urchants feed on kelp-kelp population declines dramatically b. Keystone Species is one whose abundance is relatively low but whose effect on it?s ecosystem is relatively large i. Greater impact than predicted, if you remove a keystone species IV. Biogeochemical Cycling a. Energy doesn?t cycle, elements do b. Carbon Cycle i. Reservoir-atmosphere ii. Human activity accelerates return of carbon to the reservoir 1. We inject 5-8 billion tons/year of CO2 into the atmosphere 2. Less is pulled from the atmosphere due to deforestation iii. This results in the Greenhouse Effect 1. CO2 acts as greenhouse gas 2. Atmosphere acts like the glass a. Good so the earth is warm enough for us to live b. Now holding too much heat in?leads to global warming?bad for agriculture, ice caps melt c. Nitrogen Cycle i. Need nitrogen to make protein, chlorophyll, nucleic acid ii. Reservoir-atmosphere 1. Atmosphere is not the reservoir for every cycle iii. Nitrogen in the atmosphere is not usable, must be converted 1. Ways a. Lightning-we?d have no life without lightning b. Bacteria c. Artificially-we have chemical plants to convert and we spray it onto the lawn i. Increase plant yield ii. Bad because they wash into lakes (too many nutrients leads to eutrophication) iii. Nitrogen is released (along with carbon) when we burn fossil fuels iv. We can increase the level by planting tons of soy beans v.Smog and acid rain cause excess nitrogen ?eutorphication V. Summary a. Cycles are interactions of biotic (organic) and abiotic (inorganic) b. There is a constant input of solar energy from the sun c. Elements/nutrients recycle d. Everything we do impacts the cycles
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