Bio 156 Unit 4 Compilation

Table of Contents:

The Digestive System: Nutrients into the Body

–          GI Tract Walls Are Composed of 4 Layers

–          5 Processes Accomplish Function

–          Digestive Organs/Accessory Organs

–          How Nutrients are Absorbed

–          Endocrine and Nervous System Regulate Digestion

–          Nutrition: Carbohydrates, Lipids, Proteins, Vitamins, Minerals, Fiber

–           Weight Control: Energy Consumption vs. Energy Spent

–          Digestive System Disorders

–          Eating Disorders

Nervous System

–          Neurons: Communication Cells of the Nervous System

–          Neuron Cell Structure

–          Sodium-Potassium Pump Maintains Resting Potential

–          Graded Potentials Alter the Resting Potential

–          Action Potentials are All-or-None and Self-Propagating

–          Neroglial Cells

–          Information is Transferred from Neuron to Target

–          Process of Synaptic Transmission: Neurotransmitter Release

–          Neurotransmitters Exert Excitability/Inhibitory Effects

–          Postsynaptic Neurons Integrate and Process Information

Population Growth and Human Impacts

–          Air Pollutants, Atmosphere, and Greenhouse Effects

–           Pollutants Produce Acid Rain

–          Water is Scarce and Unequally Distributed

–          Human Impacts on Water Supply and Water Pollution

–          Pollution and Overuse: Damaged Land

–          Energy: Many Options/Choices

–          Human Impacts: Creating a Biodiversity Crisis

–          Biodiversity is Healthy for Humans

–          Measuring Sustainability and Quality of Life

–          Toward a Sustainable Future

The Digestive System: Nutrients Into the Body

The digestion system comprises organs that function to get nutrients into the body. This is accomplished as food passes through a hollow tube in the body called the gastrointestinal tract (GI). 9 Organs as well as 4 accessory organs accomplish the process of breaking down food, digestion, and absorption of water and nutrients. The entire GI tract is 36 feet long as it begins as food is taken in through the mouth and expelled as waste through the anus.

Digestive System
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Digesting food takes 10% of the total daily energy requirement of the body. 70% of the energy is just spent on “idle” which maintains the functioning of the body, while 20% of energy output is utilized for activities of daily living.

GI Tract Walls Are Composed of 4 Layers

Mucosa: Innermost layer (mucous membrane) is in contact with the lumen (the space the food travels through). To enter the blood, all nutrients cross through this tissue.

Submucosa: Layer outside of mucosa that is comprised of connective tissue. The components of food that are absorbed in the mucosa enter this tissues lymph and blood vessels (this tissue also contains nerves).

Muscularis: Layer outside of submucosa that is responsible more movement. It has 2 or 3 sublayers of smooth muscle; one that is oriented in a circular fashion around the “tube” and one that is arranged lengthwise.  (Stomach has diagonal sublayer).

Serosa: The thin outermost wall of GI tract. It protects the other layers and attaches the digestive system to body cavity walls.

  • Sphincters (thick ring of smooth circular muscle) separate some of the organs from each other. They do this by contracting which closes of the passageway between organs.

    GI Tract Wall (Layers)
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  • 5 Processes Accomplish FunctionRaw materials must be broken down into a form the body can use. This is accomplished by:
    1. Mechanical processing and movement. Chewing begins the process of breaking food down. Peristalsis propels the food forward in the GI tract. Segmentation mixes the food in a back-and-forth action. Peristalsis occurs throughout the tract while segmentation occurs primarily in small intestines (this action pushes food against the mucosa so body can absorb nutrients).
    2. Secretion. Enzymes, fluid, acid, alkali, bile, and mucus are secreted at various places into the GI tract. Several hormones that regulate digestion are also secreted into the blood.
    3. Digestion. Food is broken down chemically and mechanically into smaller products, culminating in nutrient molecules.
    4. Absorption. (mostly in the small intestine) Nutrients pass into the blood or lymph by crossing the mucosal layer of the GI tract.
    5. Elimination. Undigested material (waste) is expelled out of the body.Digestive Organs/Accessory OrgansMouth : The average adult mouth contains 32 teeth that are specialized to crush, grind, cut, and tear food. The act of chewing begins the process of breaking the food down into smaller pieces. The tongue positions the food over the teeth (also assists in speech and taste).

      Salivary Glands: (Accessory Organ) the 3 pairs of glands in the mouth (near back of jaw, below lower jaw, under tongue) produce saliva that moistens and helps keep the food together and easier to swallow. The 4 main ingredients include: mucin, a protein that holds particles together for easier swallowing; salivary amylase enzyme that begins the process of digesting carbohydrates; bicarbonate that maintains pH that is most effective for amylase ; and lysozyme which helps to inhibit bacterial growth.

      Pharynx: Place where food enters after being pushed down by the tongue. Receptors in the pharynx stimulate the “swallowing reflex”. The soft plate closes off the nasal passageway (by rising) and the larynx raises a little as the epiglottis bends to close the airway (trachea) temporarily. This prevents us from choking. The food slides past the epiglottis and into the esophagus.

      Esophagus: This is a muscular tube that, through peristalsis, propels the food forward to the stomach and consists of smooth muscle and skeletal muscle. The lining produces mucus to make the food slide down easier. The esophageal sphincter prevents reflux of the contents of stomach by opening as food arrives and closing after it passes into the stomach.

      Stomach:The stomach stores food, regulates delivery, and digests protein. The stomach stores food until it can be digested and is able to expand 1-3 liters capacity when we eat. Gastric glands secrete hydrochloric acid, mucus, or primarily what becomes pepsin (protein-digesting enzyme that is created as pepsinogen is exposed to stomach acid). Muscle contractions mix all the contents together, mechanically breaking food into smaller particles. Then the stomach delivers the partially digested contents (chime) into the small intestine (stomach regulates the rate of delivery). A mucus layer protects the tissues from the acidic contents. * Peptic ulcers may occur when the mucus layer is damaged and the underlying tissue is exposed creating an open sore.

      Small Intestine: Peristalsis starts at the lower esophageal sphincter which only propels about 1 tablespoon of chime into the small intestine at a time before it closes. The small intestine contains villi, folds, and microvilli that increase the surface area of small intestine by over 500 times. This makes it ideal for the absorption of nutrients. Carbohydrates and lipids are digested here, as well as continuing of protein digestion.  The gastric juices are neutralized and digestive enzymes are added from the intestine and pancreas. The first region called the duodenum is where most of the remaining digestion takes place and the remaining 2 sections (jejunum and ileum) primarily absorb water and nutrients. As the water and nutrients are absorbed through the mucus layer, they are transported through the blood and lymph vessels to nourish the body.

      Pancreas:Organ that lies just behind the stomach and performs exocrine and endocrine functions. The pancreas produces and secretes several digestive enzymes aimed at protein, carbohydrate, and lipid digestion. Proteases, trypsin, chymotrypsin and carboxypeptidase work to digest proteins; pancreatic amylase work to finish the digestion of carbohydrates; and lipase works to digest lipids. Sodium bicarbonate is secreted to neutralize stomach acid and allow other pancreatic enzymes to work more effectively.

      Liver: The liver produces bile to facilitate digestion of lipids. The hepatic portal system (carries blood from one capillary bed to another) carries nutrient rich blood directly from digestive organs to the liver. The liver processes and stores nutrients for the body. The liver is also involved with many other functions that maintain homeostasis: stores fat-soluble vitamins; stores glucose as glycogen; manufactures plasma proteins; synthesizes and stores some lipids; inactivates many chemicals; converts ammonia into less toxic urea; and destroys worn-out red blood cells.

      Gallbladder: The gallbladder receives the bile the liver produces through ducts and then removes water to concentrate and store it. The bile is released and secreted into the small intestine after a meal.

      Large Intestine: The large intestine absorbs most of the remaining water and nutrients and stores the remainder of the material as waste until it is expelled. It begins at the cecum (a pouch that receives chyme from small intestine) and includes 4 regions: ascending colon, transverse colon, descending colon, and sigmoid colon (where feces are stored until they pass through the rectum and anus- expelled). There are multiple strains of bacteria that live in the colon, some of which create useful by-products such as vitamin K.

      How Nutrients Are Absorbed

      Carbohydrates and proteins are absorbed by active transport. Proteins are broken down into amino acids and then actively transported into the mucosal cells. Through facilitated diffusion, they eventually make their way out of the mucosal cells and into the capillaries.

      The digestion of carbohydrates begins in the mouth as salivary amylase begins the process of breaking down polysaccharides into disaccharides. The digestion is completed in the small intestine as enzymes and pancreatic amylase break down the remaining carbohydrates into monosaccharaides. Monosaccharaides use different active transport proteins, but follow similar pathways to those for amino acids.

      Lipids are broken down by bile salts into tiny fat droplets. These are then digested by intestinal and pancreatic lipases. They become fatty acids and monoglycerides and dissolve in micelles (small droplets of bile salts and lecithin). Micelles’ function is to transport monoglycerides and fatty acids to the outer surface of cells so they may be absorbed into the cell. Inside the cell they recombine into triglycerides, are given a protein coating, and released into the lymph to return to the venous blood vessels near the heart.

      Water is absorbed by osmosis due to the higher concentration of water in the lumen than in the intestinal cells (or in the blood).

      Vitamins and minerals have many paths of absorption dependent on if they are fat or water soluble. Fat- soluble follow the lipid pathway: dissolve in the micelles and absorbed by diffusion through the lipid membrane of cell layer. Water-soluble vitamins are absorbed through diffusion (through pores or channels) or active transport. (The body also digests and reabsorbs the components of digestive secretions themselves, returned to the liver, and recycled to use again).

      Endocrine and Nervous Systems Regulate Digestion

      Regulation depends on volume and content of food. As the stomach stretches the neural reflexes increase peristalsis and secretion of gastric juices. The stretching of the stomach combined with the trigger of protein release gastrin stimulates the gastric glands.

      In the small intestine, acid in chyme stimulates release of secretin which stimulates the pancreas to secrete bicarbonate (neutralizing acid).  Protein and fat stimulate release of cholecystokinin (CCK) which then stimulates the pancreas to secrete enzymes and the gallbladder to release bile. Stretching, secretin, and CCK inhibit stomach movement and stomach secretions.

      In the large intestine gastrin and stomach stretching increases movement.

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      Nutrients are used or stored until needed. Depending on what molecules are in short supply and which may be in excess the body, there can be a great amount of conversion of one to another according to the body’s needs. When people consume more nutrients (and calories) than what is actually used, the body may store the excess for future use which could lead to increased body weight in time. When people consume less than what is used, the body utilizes storages of energy to make up the difference. In time (and done regularly) the person will lose weight. Eating a healthy diet may help one get the nutrients their body needs while maintaining a healthy weight. General recommendations include: consuming less than one teaspoon of salt a day and using sugar in moderation; eating plenty of vegetables, fruits, and whole-grain products; eating a variety of foods; and only drinking alcoholic beverages in moderation.


      Carbohydrates are a major source of energy and many nutritionists recommend 45%-65% of Calorie intake come from carbohydrates. Carbohydrates can be simple (sugars) that are found in natural products such as honey and fruits, or complex(starch or glycogen) found in vegetables such as potatoes and corn or grains such as rice or oatmeal. Complex carbohydrates are better because they release sugars more slowly and contribute minerals, vitamins, and fiber. Refined sugars are the least beneficial (such as corn syrup or granulated sugar) as they release sugars quickly and have had most other nutrients removed.

      Simple carbs (left), complex (right)
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      Lipids are essential for cellular structure (components) and are energy sources. Most of the cell membrane is comprised of phospholipids and cholesterol. Cholesterol also forms the backbone of steroid hormones and is used to synthesize bile. Fat cushions organs, insulates the body, stores energy, and stores vitamins. Too much fat in a diet can lead to excess weight gain and higher risk of cardiovascular disease. Most nutritionists recommend no more than 20%-35% of Calories per day should come from lipids.

      Saturated fats tend to be solid at room temperature and are found primarily in meat and dairy products. They tend to raise “bad” LDL cholesterol.

      Unsaturated fatsare oils at room temperature and are considered healthier than saturated fats because they tend to lower LDL levels. These tend to come from plants such as olive, canola, and corn.

      Trans fats are vegetable oils that are turned back into solids at room temperature by partial hydrogenation of the fatty acid tails. They may increase shelf life and are used in commercial baked goods, margarine and shortening. Trans fats also tend to raise LDL cholesterol and increase the risk of cardiovascular disease (as does saturated fats).


      Proteins make up the enzymes that direct metabolism, they build muscle fibers, serve as receptor/transport molecules, and a few are hormones. All proteins are comprised of 20 different amino acids. The body can produce 12, but 8 have to be obtained from our diet and are called essential amino acids.

      Complete proteinis a protein source that contains all 20 amino acids in the proportion the body needs. Sources include nearly all animal proteins (meat, fish, milk, yogurt, eggs), but almost all plant proteins (except soybeans) lack at least one or more of the essential amino acids. Vegetarians must be careful in selecting various foods to ensure they obtain the proper balance of amino acids (such as red beans and rice). Approximately 15% of a person’s Caloric intake should come from protein.


      A group of at least 13 chemicals that are essential for normal functioning and fall into two groups: fat soluble and water soluble. Fat soluble are absorbed and stored along with the components of fat and released from the fat tissue as needed. Water soluble vitamins are absorbed easier than fat soluble vitamins but are only stored briefly and must be consumed on a regular basis.


      Minerals are chemical compounds that are found in nature (inorganic) and are essential for normal metabolic functioning. They are found in the blood as ions (potassium, sodium, chloride), represent most of the chemical structure of bone, and contribute to the activity of muscles and nerves. There are 21 minerals that are considered essential.


      Fiber is indigestible material found in many gains, vegetables, and fruit. It is beneficial to the colon as it makes feces bulky and helps them to pass more efficiently through the colon. A diet low in fiber can cause constipation, hemorrhoids, or diverticulosis. It is recommended that a person eat 20-35 grams of fiber a day for optimum colon functioning

      Weight Control: Energy Consumed vs. Energy Spent

      Energy is measure in units called Calories. A person’s daily caloric energy needs can be determined by your basal metabolic rate (BMR). This is the energy a body needs to perform the functions of sustaining life (breathing, maintaining organ function). BMR can be influenced by several factors including: gender and body composition, age, health, stress, food intake, and genetics.

      Healthy weight control involves not consuming more calories than what you are actually burning. Physical activity is an effective way to maintain healthy weight. While a person’s BMR stays fairly constant, exercising burns extra calories. 3500 Calories must be used to lose one pound of fat.

      Healthy weight improves overall health and reduces the risk of many diseases and ailments. The government recommends a BMI (body mass index) of 18.5-25 to be healthy. BMI is a measurement of body fat that utilizes a person’s height and weight to determine percentage of body fat. A measurement of 30 or higher represents obesity.

      Digestive System Disorders

      –          Lactose intolerance: difficulty digesting milk due to loss of enzyme that digests lactose.

      –          Peptic ulcers: sores in the stomach due to erosion of mucosal lining of the stomach.

      –          Celiac disease: (also known as gluten intolerance) the immune system responds to gluten by damaging or destroying the villi in the small intestine. The results in malabsorption of all sorts of nutrients and symptoms vary but may be diagnosed by a blood test.

      –          Diverticulosis: Small sacs in the mucosal lining of large intestines which represents a weakness in the wall. It is suspected that inadequate dietary fiber may contribute to the development of diverticulosis.

      –          Colon polyps: can be cancerous or non-cancerous growth that projects from a mucous membrane.  Polyps can be detected and removed in a colonoscopy (because most colon cancer starts as polyps).

      –          Hepatitis: Generally caused by toxic substances or viruses, it is inflammation of the liver. Hep A (there is a vaccine for) is transmitted by contaminated water/food and causes a brief illness. Hep B travels in body fluids/blood and if not treated can lead to liver failure (vaccine available). Hep C is also transmitted through blood and damages the liver. Severe cases may lead to cirrhosis or liver cancer.

      –          Gallstones: Excessive cholesterol in the bile may lead to the formation of gallstones that may grow large enough to obstruct bile flow and cause intense pain. Treatments may involve dissolving the stone(s) or removal of the gallbladder.

      –          Malnutrition: Conditions where body development and function are compromised due to over nutrition (which leads to obesity) or under nutrition (insufficient diet).

      –          Obesity: The World Health Organization says obesity is a global epidemic. There is a strong link between environment and the global rise in obesity as modernization favors an imbalance between caloric intake and expenditure.

      Eating Disorders

      Eating disorders are nervous system disorders and are most prevalent in women living in industrialized Western nations. They involve intense fear of gaining weight.

      Anorexia nervosa: People with this condition stop eating or diet excessively, possibly to the point of starvation/death. Symptoms include distorted perception of body image, even when severely underweight.

      Bulimia: A binge-and-binge eating cycle where one eats (excessively) and then vomits or takes other actions to minimize the Calories ingested. This involves a lack of control over eating and a preoccupation with body weight/shape, but some bulimics may maintain a normal weight.

      Science in the News

    6. ScienceDaily (Apr. 9, 2012)

    On Monday, April 9, 2012 the first FDA approved magnetic heartburn device was inserted in a patient with GERD (gastroesophagel reflux disease). This device is called LINX and is implanted at the lower esophageal sphincter. The device addresses the source of the acid reflux by correcting the anatomy (assists in closing the sphincter) as opposed to medications that merely suppresses stomach acid. Clinical trial results have indicated that LINX is highly effective in treating GERD and the painful burning sensation that occurs with acid reflux. What makes this device even better is that it can be implanted in an outpatient setting that may only require a 20-30 minute procedure.

    1. Nervous SystemThe nervous system comprises 2 principle parts:
      1. Central Nervous System (CNS): This is made of the brain and spinal cord and functions to receive, process, and transfer information.
      2. Peripheral Nervous System (PNS): This is made of the nerves outside of the CNS.

      –          Sensory Division: carries information toward the CNS (input). Signals from the environment, skin, muscle, organs send info toward CNS.

      –          Motor Division: carries information away from the CNS (brain directs motor activation after receiving input= output). This involves control of skeletal muscle, parasympathetic, sympathetic, and automatic control.

      Neurons: Communication Cells of the Nervous System

      Neurons are specialized cells for communication that generate and conduct electrical impulses. Neurons generate and transmit action potentials that are electrical impulses. They serve as the primary means of communication throughout the nervous system. Types of neurons:

      Sensory Neurons are found in the PNS that receive stimuli and transmit information to the CNS.

      Interneurons transmit information between components of the CNS (distance between neurons).

      Motor Neurons are found in the PNS and transmit information away from the CNS.

      Neuron Cell Structure

      There are three parts of a neuron:

      Cell body- the main part of the cell where nourishment occurs, containing the nucleus and most of the cytoplasm/organelles.

      Dendrites- small slender extensions of the cell body that receive incoming information.

      Axon- slender extensions that are specialized to conduct electrical impulses away from the cell body.


      Nerve Cell
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      Sodium-Potassium Pump Maintains Resting Potential

      The Sodium-Potassium Pump functions to maintain cell volume and establishes/maintains the resting potential by active transport of sodium out of the cell and potassium into the cell. The resting potential is the measurable difference in voltage across the cell membrane in a resting cell (70mv). The inside of a cell has a different (negative charge relative to exterior) than the outside of a cell, that is ready to be stimulated/altered/acted upon.

      Graded Potentials Alter the Resting Potential

      Graded Potentials are transient local changes in the resting potential that may depolarize or hyperpolarize.

      Summation: graded potentials can add up in space or time (accumulative effect of stimulus) that may reach a “trigger point” or threshold, which initiates an  Action Potential (sudden reversal of membrane voltage).

      Action Potentials occur as/when:

      –          Initiated when graded potentials reach a certain threshold/trigger point.

      –          Depolarization when sodium moves into the axon (reverses inside to a positive rather than negative charge). This causes a power surge to travel out and positives are turned to negative, negative to positive.

      –          Repolarization occurs when potassium moves out of the axon which restores the initial polarity.

      Reestablishment of the resting potential is the activity of the sodium potassium pump.

      Action Potentials are All-or-None and Self-Propagating

      Individual neuron threshold sets extent of the stimulus needed. If it achieves threshold, it fires. Once triggered, an action potential is always the same in form and voltage (all-or-none). Action potentials continue to propagate themselves in the next region of the axon, and moves like a wave down the axon (at a constant speed and amplitude).

      The number of action potentials/ unit of time encodes the strength of the stimulus. Stronger stimuli generate more action potentials/unit time. The speed of action potentials are always the same for a particular neuron.  The speed can, however, be different in different neurons based on the size of the cell membrane. In larger diameter axons, action potentials travel at a greater speed.

      Neuroglial Cells

      Neuroglial Cells support and protect axons. They make up 80% of the nervous system (Schwann cells, oligodendrocytes) and nourish, clean (some act like phagocytes to clear debris) from axons. They DO NOT transmit action potentials.

      Schwann cells form myelin sheath on neurons in the PNS. This aids in saving the neuron energy and speeds up the transmission of impulses.  Saltatory conduction (compound that insulates axon) causes a leaping pattern of action potential conduction. They help damaged or severed axons regenerate.

      Oligodendrocytes form myelin sheathes in the CNS. They do not have the same capabilities to help repair damage to axons (this is why once someone sustains spinal cord injury and are paralyzed, they do not regain movement).

      There are various disorders associated with the degeneration of myelin sheaths which causes a slowing of transmission (scattered impulse):

      –          MS (multiple sclerosis): progressive damage to the myelin sheaths in the brain and spinal cord which causes weakness, visual impairment, and incontinence.

      –          ALS (amyotrophine lateral sclerosis): progressive damage to myelin sheaths in motor area of the spinal cord which causes progressive weakening and wasting of skeletal muscle due to lack of muscle stimulation.

      Information is Transferred from Neuron to Target

      The special junction between axon terminus (axon bulb) and target cell (which can be another neuron, muscle cell, or gland) is called a Synapse. Synaptic transmission is the process of transmission of impulses from sending (pre-synaptic neuron) across the synaptic cleft to receiving (post-synaptic) target. This involves the release and diffusion of chemical neurotransmitters.

      Process of Synaptic Transmission: Neurotransmitter Release

      1. Action potential arrives at axon terminus causing calcium to diffuse into axon bulb.
      2. Calcium causes release of neurotransmitter from the vesicle.
      3. Neurotransmitter diffuses across the synaptic deficit.
      4. Neurotransmitter binds to receptor target (post-synaptic) membrane and opens gated channels.
      5. Graded potential results from sodium movement through open channels (ions go through).    

      Neurotransmitter Exert Excitability/Inhibitory Effects

      The response of postsynaptic target cells depends on several factors. First off, the response depends on the type of neurotransmitter, as there are 750 types. Response also depends on type of receptors and type of gated ion channels (the gates allow or don’t allow a particular molecule to pass through).

      Excitatory neurotransmitters depolarize the postsynaptic cell, approaching or exceeding threshold. Inhibitory neurotransmitters hyper-polarize the postsynaptic cell (prevents from receiving charges).

      Postsynaptic Neurons Integrate and Process Information

      Response in postsynaptic cells depends on how many neurons are forming synapses with it and whether the neurons forming synapses with it are excitatory or inhibitory. Convergence occurs when one neuron receives input from many others (spinal cord receives sensation from skin). Divergence occurs when one neuron sends action potentials to multiple other neurons.

      Population Growth and Human Impacts

      Air Pollutants, Atmosphere, and Greenhouse Effects

      Pollutants impair air quality (air pollution) and create many concerns: global warming, destruction of the ozone layer, acid precipitation, and smog production.

      The sun supplies the Earth with abundant energy (especially at the equator) and the atmosphere captures it selectively. 25% of the energy is reflected by clouds and atmospheric gasses; 25% is absorbed by carbon dioxide, water vapor, ozone, methane (and a few other gasses); and 50% of incoming solar radiation (insolation) actually reaches the Earth’s surface.

      The Greenhouse Effect has to do with the second law of thermodynamics= high quality solar energy entering Earth’s atmosphere is re-emitted as lower-quality heat energy. The idea is that energy is not created/destroyed but is transformed. The atmosphere close to Earth (troposphere) is loosely comparative to the glass of a greenhouse because it lets sunlight through but traps heat from radiating back outward. This maintains the heat needed for liquid water on Earth.

      The Greenhouse Effect is responsible from global warming. Human activities have increased levels of carbon dioxide which is a major greenhouse gas through deforestation and usage of fossil fuels. Other examples of Greenhouse gasses include: methane, nitrous oxide, chlorofluorocarbons (CFCs), and halons. The effect is that some areas of the Earth warm and others cool as a result of change in ocean temperatures (which have a major role in climate system).

      CFCs deplete the ozone layer (divided into 2 atmospheric locations troposphere and stratosphere). Pollutants in the troposphere (closest to Earth’s surface) cause respiratory difficulties. The stratosphere is the shield that protects Earth’s surface from UV light. The stratospheric ozone layer has been (and continues to be) depleted by reactions with CFCs. This has created concerns about excess UV radiation and exposure. CFCs come from refrigerants and aerosol sprays, and their use has decreased due to international agreements.

      Smog (smoke+fog) production comes from industry and the burning of fossil fuels. Smog constituents are: nitrogen oxides, hydrocarbons, small oil droplets, wood particles, coal ash, asbestos, lead, animal waste, and dust. This makes for a cocktail of irritants for eyes and the respiratory system. Thermal inversion refers to atmospheric conditions that trap smog and prevent its dispersal as cold air above traps warm air and holds it down close to the Earth’s surface (makes me think of the brown haze I have witnessed in PHX).

      Pollutants Produce Acid Precipitation

      Sulfur dioxide from high sulfur coal and oil (once trapped in the Earth) is released in to the air along with nitrogen oxides from car exhausted. Once the sulfur dioxide and nitrogen oxide mix with water vapor they become sulfuric acid and nitric acid. When the rain comes down the acid precipitation causes damage to the Earth including: corrosion of metal and stone, and the disruption of forest and aquatic ecosystems. This occurs as a result of lowering pH levels of the ecosystems which maintain a delicate balance and can’t tolerate the disturbance. Acid precipitation is on the decline due to pollution abatement measures, but in North America the north east and parts of Canada are most affected.

      Water is Scarce and Unequally Distributed

      Less than 1% of the Earths total water supply is fresh water. Salt water ocean accounts for 97%, and water frozen in glacier and polar ice caps accounts for the remaining 2% (which are melting).

      Industrialized nations use 10-100 times more water than less industrialized countries. It requires more water to make things, and indoor plumbing makes water more accessible. Some desert and semi-desert countries have reached their water supply carrying capacity and must transport water in. When this happens, diversion of water impacts other human populations and species.

      Human Impact on Water Supplies and Water Pollution

      Human beings as a whole use tremendous amount of water, depleting freshwater supplies. Think about the daily activities of laundry, dishes, showers, toilets, drinking, watering your garden, washing your car, not to mention industry and construction demands.

      –          Urbanization increases storm water runoff as the water from roads, parking lots, and buildings rush into streams. The runoff doesn’t allow the water to be absorbed into the ground (and causes erosion) and the aquifer stores don’t have the opportunity to be replenished. Groundwater pollution contaminates drinking water supplies. There is a very slow exchange of the groundwater pool, it “cleans” slowly but cannot filter pollutants out the runoff also prove harmful as it may combine with sewage as overflow. This leads to possible spreading of diseases and poses a health hazard.

      .-          Human activities pollute freshwater with organic and inorganic pollutants. Organic pollutants are a result of sewage and industry, but the inorganic pollutants include: nitrates; phosphate fertilizers; and sulfates from detergents. Nitrates and phosphates wash off fields and in to the ecosystem where they alter the natural balance. Introduction of fertilizer may result in eutrophication which is rapid growth of plant life leading to death of animal life result from excessive inorganic/organic nutrients. This could present itself as an overgrowth of algae that eventually eliminates fish that can no longer breathe.

      –          Toxic pollutants include: polychlorinated biphenyls (PCBs); oil and gasoline; pesticides; herbicides; and heavy metals. These pollutants bring the issue of biological magnification: the concentration of toxic pollutants in the tissues of organisms higher on the food chain. The toxic substances accumulate in the flesh of the animal (think accumulation of mercury in fish). I also remember watching a program about the Eskimo in Alaska who are eating large mammals that contain high levels of heavy metals in their blubber. There are issues with birth defects as the mothers are ingesting the toxic flesh.

      –          Oil is another pollution concern. Sources include: 20% accidents at sea; 30% from runoff of the land; 50% seepage. The percentage for accidents at sea has most likely risen as a result of the 2010 Deepwater Horizon explosion and “spill”. Another unknown percentage comes from cruise liners. The oil pollution causes significant damage to shoreline ecosystems as 25% of the oil spilled at sea ends up in the sediment. The remaining 75% ends up in evaporation (25%) or degraded by bacteria (50%).

      Pollution and Overuse: Damaged Land

      One third of Earths land mass has been altered by human beings. This includes the fact that 50% of the world’s forests have been removed, often times for agriculture. As cities expand productive land is consumed and the urbanization increases water use and runoff issues. Desertificationis the transformation of marginal land into near desert conditions due to over use, making it unusable for future agriculture. Land is also damaged as we use it to bury our garbage in dumps and may be contaminated through war.

      Risk of Human Induced Desertification
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    2. Its interesting to note that while there are over 80,000 potentially edible plants, human beings only consume aproximately 30 of them which comprise 90% of our caloric intake. Only about 1% of plants have been tested for their medicinal value, yet plant products constitue 50% of medication ingredients.

    Energy: Many Options/Choices

Nonrenewable resources include fossil fuels such as coal, oil, and gas. These products are limited in that there are only so much of these

in the world. Renewable resources include:

  • Nuclear energy- but then there are safety concerns and disposal issues
  • Hydroelectric power- yet the dams used to capture water alter ecosystems
  • Wind farms- but these have created problems for some species of birds/bats
  • Biomass fuels – which have created concern over usage of land (fuel or food) as well as usage of plants for food or for energy
  • Solar energy- utilizing the abundant source of light from the sun to harness energy- yet at the moment aren’t efficient enough to need all the world energy demands

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Human Impacts: Creating a Biodiversity Crisis

Human beings are creating a misbalance in ecosystems all over the world. We are accomplishing this through the various sources of pollution and habit destruction as there is a worldwide shift in people moving into cities. As people destroy habitat there is less plant and animal diversity. Diversity is essential to species surviving natural disasters and increase in global temperature.

Humans also over exploit natural resources, taking and using at a rate that nature can’t keep up with. The land is over farmed, the oceans are overfished which and doesn’t allow enough time for the species to regenerate fast enough to keep up with human demand. There is much exploitation of scarce forest resources as logging and deforestation wipe our forests out. As the forest (specifically referring to South America) is cut down and cattle are introduced, the soil is initially great for grazing, yet the soil is very delicate. Eventually, the soil cannot sustain the cattle and becomes useless as more forest must be cut down to feed the cows (which also accounts for a surprising amount of methane in the atmosphere).

Retrieved from: on 4/28/12

Worldwide, cities create 78% of carbon emissions, 60% of residual water use, and 76% of wood is used for industry. The ecological damage that a city causes is much larger than the size of the city itself.

Biodiversity is Healthy for Humans

There are 895 separate ecological regions on the Earth that human beings benefit from.  Plants (through photosynthesis) recycle carbon dioxide and provide us with oxygen. Plants are also sources of food for us and the animals we eat, in addition to providing humans with medicines. A variety of plant life provides stability to all ecosystems. No matter how much man would like to see himself apart from nature, we depend on the Earth’s animals/plants/ecosystems everyday for the necessities of life. We are a part of the web, not outside of it.

Measuring Sustainability and Quality of Life

Gross Domestic Product (GDP) refers to the total market value of all goods and services produced within a country per year. This is the standard indicator of economic progress. Genuine Product Indicator (GPI) is the measurement of the market value of goods and services PLUS the environmental costs of production (of the goods and services), social costs, and the overall quality of life. This reminds me of a saying I heard recently, “What are we going to tell our kids when we have done so much harm to this Earth.. that it was good for the economy?!”

Retrieved from: on 4/28/12

Toward a Sustainable Future

People must take action if we are to live in harmony with the delicate balance of ecosystems. By exterminating other species life on Earth, we threaten exterminating ourselves in time. Some ideas include:

  • Consume less. Industrialized nations in particular tend to use more than what they need.
  • Recycle more. There are many daily products that can be recycled or reused.
  • Support sustainable agriculture.
  • Support green roofs.
  • Lower worldwide fertility rate- over population is the concern here.
  • Reduce rural world poverty.
  • Conserve energy at home- afterall that’s where it starts- in your own home.
  • Use environmentally preferable products- less garbage, possibly less contamination.
  • Protect ecosystems that provide ecoservices

We only have one beautiful planet. As human beings look forward into the future, I hope people recognize that change must occur if we are to survive on this planet. The Earth has always provided the balance needed for regeneration, it is human beings that have altered and created imbalance through our actions. We must learn to live with the Earth, instead of merely exploiting the resources at will.


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