LECTURE 1 INTRODUCTION TO ENVIRONMENTAL SCIENCE

I. WHAT IS ENVIRONMENTAL SCIENCE 1. What is environment? Consists of both: Biotic factors/elements (living things) Abiotic factors/elements (nonliving things)that surround us, and which we interact with.2. What is environmental science? Environmental science is an interdisciplinary study of how humans interact with living and nonliving parts of their environment. (Natural sciences, Social science, Humanities) Biology is the study of living organisms Chemistry is the study chemicals and their interactions Physics is the study of matter and energy Earth science is the study of earths nonliving systems Social science is the study of human populations Goals of environmental science To learn how nature works To understand how we interact with the environment To find ways to deal with environmental problems and live more sustainably Ecology is a key component of Environmental science Ecology studies how organisms, or living things, interact with one another and with their environment Ecosystem is a set of organisms within a defined area or volume interacting with one another and with their environment of nonliving matter and energy Environmental science is not environmentalism Environmental science The pursuit of knowledge about the natural world Scientists try to remain objective Environmentalism Environmental activism A social movement dedicated to protecting the natural world3. Natural CapitalNatural capital = Natural resources + Natural services Natural resources: materials and energy in nature Renewable Nonrenewable Natural services : processes in nature (Photosynthesis, Nutrient cycling)II. ECOLOGICAL - Humans impact over history Wherever humans have hunted, grown food, or settled we have changed the environment. - Hunter-Gatherers Most of human history People who obtained food by moving around collecting plants and hunting wild animals. - Agricultural revolution Plants and animals were domesticated and population grew. 10,000 years ago Life got easier Population grew Towns began forming Impact on environment grew More land used- Industrial revolution Caused a shift to fossil fuels as an energy source. 1800s Life got easier Advances in technology People lived longer People moved to cities away from farms Increased environmental impact- Renewable resources Resource is anything obtained from the environment to meet our needs and wants Renewable resources include solar energy, air, water, soil, plants, wind Renewable resources can be replenished in days to several hundred years Solar energy is a perpetual resource because it is renewed continuously Renewable resource can be used indefinitely without reducing its available supply -> sustainable yield When use -> replacement rate -> environmental degradation - Non-renewable resources Non-renewable resources exist in a fixed quantity of stock Nonrenewable resource forms more slowly than it is used up Non-renewable resources include fossil fuels like coal, oil and natural gas, metallic minerals, non-metallic minerals Resource is said to be depleted when almost used up Some non-renewable resources can be recycled or reused 3Rs of more sustainable use: Reduce (use less), Reuse (use a resource over and over), Recycle (processing it into new materials)- Tragedy of the Commons In 1968, the biologist Garrett Hardin called the degradation of openly shared resources the tragedy of the commons : In a commons open to all, unregulated use will deplete limited resources. Conflicts arise when people share resources If no one takes responsibility for the resource it will get overused and become degraded/depleted Example: Renewable resources like trees cut faster than they formed - Ecological footprints Ecological footprint is the amount of biologically productive land and water needed to supply a person or country with renewable resources and to recycle the waste and pollution produced by such resource use. It compares human demand with planet Earth's ecological capacity Per capita ecological footprint is the average ecological footprint of an individual in a given country or area. The footprint can also be a useful tool to educate people aboutcarrying capacityandover-consumption, with the aim of altering personal behavior. - Who uses most resources? Developed countries like the U.S. (high personal wealth) have high consumption rates What are the developed countries of the world? Developing countries : have high population growth, poverty and lower resource consumption Ecological footprints are not all equal- IPAT model Rich and poor countries have different environmental impact Simple model of Ehrlich and Holdren (1970) I = P x A x TI: Environmental impactP: PopulationA: Affluence or resource consumption per personT: Technology used

III. ENVIRONMENTAL PROBLEMS & THEIR CAUSES - Human activities = Impacts on environment- What are our main environmental problems: Pollution Pollution : an undesirable change (by contamination of chemical or other agents) in the air, water or soil that affects humans or other organisms. Air pollution Water pollution Land pollution- Pollution Point source Single identifiable source that discharges pollutants into the environment (smoke stack, exhaust pipes, industrial discharge) Non-point source Large or dispersed land areas, such as crop fields, streets, and lawns that discharge pollutants into the environment over a large area (stormwater, septic tanks)- Dealing with pollution Prevention input control Cleanup ands remediation output control Which strategy is more - What are our main environmental problems : Loss of biodiversity Biodiversity : the number and variety of species that live in an area. Earth has been home to 100s of millions of species Only a few exist today Mass extinctions - What are our main environmental problems : Global warming Sea level rise: Underground water salined, loss of islands and low-lying coastal areas Leads to loss of living habitats - What are our main environmental problems : Habitat destruction- Human population growth The worlds population presently grows by about 250,000 people per day. This is roughly equivalent to adding a new U.S. city of Los Angeles, California, every 2 weeks, a new France every 9 months, and a new United Statesthe worlds third most populous countryabout every 4 years.

- Over-population leads to: Resource depletion Resource degradation Pollution Loss of biodiversity - Resource consumption Underconsumption Overconsumption Affluenza: unsustainable addiction to overconsumption and materialism.- Prices do not include the value of natural capital Using resources to provide goods and services does not include its harmful environmental costs Tax subsidies encourage the depletion and degradation of natural capital

IV. PRINCIPLES OF SUSTAINABILITY - Sustainability Sustainability is the ability of the earths various natural systems and human cultural systems and economies to survive and adapt to changing environmental conditions indefinitely Why should we care about sustainability? We are in process of rapidly degrading our own life support system- Three principles of sustainability Reliance on solar energy Biodiversity Nutrient recycling Strategies to make our life more sustainably Rely more on renewable energy Protect biodiversity Do not disrupt the earths natural chemical cycles

LECTURE 2 PART 1 ECOSYSTEMS: WHAT ARE THEY AND HOW DO THEY WORK?

I. WHAT KEEPS US AND OTHER ORGANISMS ALIVE ? - Earths life-support system has four major components The atmosphere is the thin membrane of air around the planet. The troposphere is the air layer about 411 miles above sea level. It contains greenhouse gases that absorb and release energy which warms the inner layer of the atmosphere. The stratosphere lies above the troposphere between 1131 miles; it filters out the suns harmful radiation. The hydrosphere consists of earths water, found in liquid water, ice, and water vapor. The geosphere is the hot core, a thick mantle, and thin crust. The biosphere includes parts of the atmosphere, hydrosphere, and geosphere.- Three factors sustain the earths life One-way flow of high-quality energy. Cycling of nutrients. Gravity.

- One-way flow of high-quality energy. The one-way flow of high-quality energy from the sun, through living things in their feeding interactions, into the environment as low-quality energy (mostly heat dispersed into air or water at a low temperature), and eventually back into space as heat. No round-trips are allowed because high-quality energy cannot be recycled (the first and second laws of thermodynamics)- Energy changes are governed by two scientific laws The first law of thermodynamics, or the law of conservation of energy, states that when energy is converted from one form to another in a physical or chemical change, no energy is created or destroyed. The second law of thermodynamics states that when energy is changed from one form to another, energy quality is depleted.- Cycling of nutrients The cycling of nutrients through parts of the biosphere. The earth is closed to significant inputs of matter from space, its essentially fixed supply of nutrients must be continually recycled to support life. Nutrient movements in ecosystems and in the biosphere are roundtrips take from seconds to centuries to complete. (The law of conservation of matter)- We cannot create or destroy atoms : the Law of Conservation of Matter+ Whenever matter undergoes a physical or chemical change, no atoms are created or destroyed.- Gravity Gravity, which allows the planet to hold onto its atmosphere and helps to enable the movement and cycling of chemicals through the air, water, soil, and organisms.II. WHAT ARE THE MAJOR COMPONENTS OF AN ECOSYSTEM - The nature of ecology Ecology is the science that focuses on how organisms interact with one another and with their nonliving environment in five levels - organisms, populations, communities, ecosystems, and the biosphere Organism : An individual living being Population : A group of individuals of the same species living in a particular place Community : Populations of different species living in a particular place, and potentially interacting with each other Ecosystem : A community of different species interacting with one another and with their nonliving environment of matter and energy Biosphere : Parts of the earth's air,water, and soil where life is found- Major components of an ecosystemEcosystem consist of Biotic components: living and once living parts of an ecosystem Ex: Plants, animals, dead matter, waste Abiotic components: nonliving parts of an ecosystem Ex: Water, rocks, light- Living components Organism assigned to the feeding level, or trophic level, depending on the source of food or nutrients. Producers (autotrophs) : green plants through photosynthesis process. Consumers (heterotrophs) : Herbivores, carnivores, omnivores Decomposers and detrivores detritus = dead organic materials- Producers: basic source of all food Most producers capture sunlight to produce carbohydrates by photosynthesis- Photosynthesis : A Closer Look Chlorophyll molecules in the chloroplasts of plant cells absorb solar energy. This initiates a complex series of chemical reactions in which carbon dioxide and water are converted to sugars and oxygen.- Consumers: eating and recycling to survive Consumers get their food by eating or breaking down all or parts of other organisms or their remains. Herbivores Primary consumers that eat producers Carnivores Secondary consumers eat primary consumers Third and higher level consumers: carnivores that eat carnivores. Omnivores Feed on both plant and animals.- Decomposers and Detrivores Decomposers : recycle nutrients in ecosystems. Detrivores : insects or other scavengers that feed on wastes or dead bodies.- Aerobic and Anaerobic Respiration: Getting Energy for Survival Organisms break down carbohydrates and other organic compounds in their cells to obtain the energy they need. This is usually done through aerobic respiration. The opposite of photosynthesis Anaerobic respiration or fermentation: Some decomposers get energy by breaking down glucose (or other organic compounds) in the absence of oxygen. The end products vary based on the chemical reaction: Methane gas Ethyl alcohol Acetic acid Hydrogen sulfideIII. WHAT HAPPENS TO ENERGY IN AN ECOSYSTEM - Energy flows through ecosystems in food chains and food webs A food chain is a sequence of organisms, each of which serves as a source of nutrients and energy for the next organisms. Organisms are assigned to trophic levels in a food chain. A food web is a series of interconnected food chains. Food webs occur in most ecosystems. Organisms are also assigned to trophic levels in food webs. Producers are the first level. Primary consumers are the second. Secondary consumers belong to the third. Tertiary consumers are the fourth level. Detritivores and decomposers process detritus from all trophic levels.- Usable energy decreases with each link in a food chain or web There is less high-quality energy available to organisms at each succeeding feeding level because when chemical energy is transferred from one trophic level to the next, about 90% the energy is lost as heat The large loss in chemical energy between successive trophic levels explains why food chains and webs rarely have more than four or five trophic levels. In most cases, too little chemical energy is left after four or five transfers to support organisms feeding at these high trophic levels. Thus there are far fewer tigers in the world than there are insects- Some ecosystems produce plant matter faster than others do The rate of an ecosystems producers converting energy into biomass is the gross primary productivity (GPP). Some of the biomass must be used for the producers own respiration. Net primary productivity (NPP) is the rate that producers use photosynthesis to store biomass minus the rate at which they use energy for aerobic respiration. NPP measures how fast producers can provide biomass needed by consumers in an ecosystem. Ecosystems and aquatic life zones differ in their NPP. The three most productive systems are swamps and marshes, tropical rain forests, and estuaries. The three least productive are tundra, desert scrub, and extreme desert.IV. WHAT HAPPENS TO MATTER IN AN ECOSYSTEM - Nutrients cycle within and among ecosystems Elements and compounds move through air, water, soil, rock and living organisms in biogeochemical, or nutrient cycles.- The water cycle Solar energy evaporates water; the water returns as precipitation (rain or snow), goes through organisms, goes into bodies of water, and evaporates again. Water is filtered and partly purified as it moves through the hydrological cycle. Water can be stored as ice in glaciers or in underground aquifers. Unique properties of water include that it: Is held together by hydrogen bonds. Exists as a liquid over a wide temperate range. Stores a large amount of heat. Requires a large amount of energy to be evaporated. Dissolves a variety of compounds. Filters some UV rays from the sun. Can move through capillary action. Expands when freezes. Exists in all three phases at the Earths surface.Effects of Human Activities on Water Cycle Humans alter the water cycle in 3 ways: Withdrawing freshwater at faster rates than nature can replenish it. Clearing vegetation which increases runoff and decreases replenishment of groundwater supplies. Draining wetlands which interferes with flood control.- The carbon cycle Carbon is the basic building block of carbohydrates, fats, proteins, DNA, and other compounds. Carbon circulates through the biosphere, hydrosphere, and atmosphere. Producers, consumers and decomposers circulate carbon in the biosphere. Fossil fuels contain carbon. Humans are altering atmospheric carbon dioxide mostly by our use of fossil fuels and our destruction of the carbon-absorbing vegetation. Effects of Human Activities on Carbon Cycle We alter the carbon cycle by adding excess CO2 to the atmosphere through: Burning fossil fuels. Clearing vegetation faster than it is replaced.- The nitrogen cycle: bacteria in action Nitrogen gas (N2), which makes up 78% of the atmosphere, cannot be used directly by most living organisms. Nitrogen-fixing bacteria convert N2 into compounds that are useful nutrients for plants and animals. The nitrogen cycle includes the following steps: Specialized bacteria convert gaseous nitrogen to ammonia in nitrogen fixation. Specialized bacteria convert ammonia in the soil to nitrite ions and nitrate ions; the latter is used by plants as a nutrient. This process is nitrification. Decomposer bacteria convert detritus into ammonia and water-soluble salts in ammonification. In denitrification, anaerobic bacteria in soggy soil and bottom sediments of water areas convert NH3 and NH4+ back into nitrite and nitrate ions, then into nitrogen gas and nitrous oxide gas, which are released into the atmosphere. Effects of Human Activities on the Nitrogen Cycle Human activities have more than doubled the annual release of nitrogen from the land into the rest of the environment, mostly from the greatly increased use of inorganic fertilizers to grow crops. This excessive input of nitrogen into the air and water contributes to pollution and other problems We alter the nitrogen cycle by: Adding gases that contribute to acid rain. Adding nitrous oxide to the atmosphere through farming practices which can warm the atmosphere and deplete ozone. Contaminating ground water from nitrate ions in inorganic fertilizers. Releasing nitrogen into the troposphere through deforestation. Human activities such as production of fertilizers now fix more nitrogen than all natural sources combined.- The phosphorus cycle Phosphorus circulates through water, Earths crust, and living organisms in the phosphorus cycle. Phosphorus does not cycle through the atmosphere. The major reservoirs of phosphorus on Earth are rock formations and ocean bottom sediments. Phosphorus is transferred by food webs and is an important component of many biological molecules. Phosphorus is often the limiting factor for plant growth. Effects of Human Activities on the Phosphorous Cycle We remove large amounts of phosphate from the earth to make fertilizer. We reduce phosphorous in tropical soils by clearing forests. Phosphate-rich runoff from the land can produce huge populations of algae, which can upset chemical cycling and other processes.- The sulfur cycle Much of the earths sulfur is stored underground in rocks and minerals. Hydrogen sulfide (H2S) is released from volcanoes and anaerobic decomposition of organic matter in bogs and swamps. Effects of Human Activities on the Sulfur Cycle Humans have been increasing atmospheric sulfur dioxide by Burning sulfur-containing fuels, Refining sulfur-containing fuels, Converting sulfur Containing metallic mineral ores into free metals such as copper, lead, and zinc releasing sulfur dioxide into the environment.

- Three Big Ideas Life is sustained by the flow of energy from the sun through the biosphere, the cycling of nutrients within the biosphere, and gravity. Some organisms produce the nutrients they need, some survive by consuming other organisms, and others recycle nutrients back to producers. Human activities are altering the flow of energy through food chains and webs, and the cycling of nutrients within ecosystems and the biosphere.

LECTURE 2 PART 2 : BIODIVERSITY AND EVOLUTION SPECIES INTERACTION & POPULATION CONTROL

I. BIODIVERSITY & EVOLUTION

1. What is biodiversity?- Biodiversity is a crucial part of the Earths natural capital The biodiversity found in genes, species, ecosystems, and the ecosystem processes of energy flow and nutrient cycling that sustain all life. Biodiversity includes a number of components. Species diversity, or the number and variety of the species present in any biological community. A species is a set of individuals that can mate and produce fertile offspring. Every organism is a member of a certain species Species diversity estimates range from 8 million to 100 million. Genetic diversity, which is the variety of genes found in a population or in a species. Ecosystem diversity refers to the earths variety of deserts, grasslands, forests, mountains, oceans, lakes, rivers, and wetlands. Functional diversity includes a variety of processes such as energy flow and matter cycling occurring within ecosystems.- Species diversity Organisms, the different forms of life on earth, can be classified into different species based on certain distinctive traits.- Genetic diversity In most natural populations individuals vary slightly in their genetic makeup. This genetic diversity enables life on the earth to adapt to and survive dramatic environmental changes.- Ecological diversity Terrestrial (land) portion of the biosphere is classified into biomes The differences reflect changes in climate, mainly differences in average annual precipitation and temperature.- Functional diversity The variety of processes such as energy flow and matter cycling that occur within ecosystems as species interact with one another in food chains and webs.- Why should we care about biodiversity?Biodiversity provides us: Natural resources (food, water, wood, energy, and medicines) Natural services (air and water purification, soil fertility, waste disposal, pest control) Aesthetic pleasure

2. Biological evolution, speciation, extinction - Biological evolution by natural selection explains how life changes over time Biological evolution is the process whereby Earths life changes over time through changes in the genes of populations in succeeding generations. The theory of evolution by natural selection is a scientific explanation of how the process of evolution takes place. Natural selection is the process in which individuals with certain traits are more likely to survive and reproduce under a particular set of environmental conditions than those without the traits.- Biological evolution Genetic variability occurs through mutations, which are random changes in the DNA molecules of a gene in any cell. An adaptation, or an adaptive trait, is any heritable trait that improves the ability of an individual organism to survive and to reproduce at a higher rate than other individuals in a population under prevailing environmental conditions. Natural selection can result in the evolution of genetic resistance, the ability of one or more organisms in a population to tolerate a chemical designed to kill the population. Examples include antibiotic-resistant bacteria and pesticide-resistant insects.- Adaptation through natural selection has limits Organisms can adapt to a change in environmental conditions only if the necessary genetic traits are already present in a populations gene pool. Another limit is that even if a beneficial heritable trait is present in a population, the populations ability to adapt may be limited by its reproductive capacity.- There are three incorrect ideas about evolution through natural selection Survival of the fittest meaning survival of the strongest. Organisms develop certain traits because they need them. Evolution by natural selection involves some grand plan of nature in which species become more perfectly adapted.- Geologic processes affect natural selection Tectonic plates shift slowly on the planets mantle, changing the earths surface. The location of continents affects climate and thus species distribution Movement of plates allowed the spread and evolution of species. Earthquakes can cause changes in earths surface that result in geologic isolation of populations. Volcanic eruptions can destroy habitats and reduce, isolate, or wipe out populations of species.- Climate change and catastrophes affect natural selection Cooling and warming periods have covered much of the earth with glacial ice, or melted the ice and drastically raised sea levels. Long-term climate changes determine where different types of plants and animals can survive, and caused the extinction of some species. Catastrophic events, such as collisions with large asteroids, have caused: Destruction of ecosystems and extinction of large numbers of species. Shifts in the locations of ecosystems and created opportunities for the evolution of new species.- Speciation Speciation is the process where one species splits into two or more different species. Geographic isolation occurs when different groups of the same population of a species become physically isolated from one another for a long period of time. Reproductive isolation occurs when mutation and change by natural selection operate in the gene pools of geographically isolated populations. Geographic isolation can lead to reproductive isolation, divergence of gene pools, and speciation.- Extinction Biological extinction is the process by which an entire species ceases to exist. Local extinction occurs when a population of a species becomes extinct over a large region, but not globally. Endemic species are found in only one area and are thus especially vulnerable to extinction. Background extinction has occurred over most of Earths history- There have been several mass extinctions of life on the Earth Mass extinction is a significant rise in extinction rates above the background level, in which large groups of species are wiped out. Fossil and geological evidence indicate that there have probably been five mass extinctions during the past 500 million years Mass extinctions have been followed by an increase in species diversity as new species have arisen to occupy new habitats or to exploit newly available resources. There is growing evidence that we are experiencing the beginning of a new mass extinction, with much of the increase in extinctions and loss of biodiversity due to human activities.

3. Importance of species diversity - Each species plays a role in its ecosystem An ecological niche is a species way of life in an ecosystem, everything that affects its survival and reproduction. Niche is different from habitat, which is the place where an organism lives. Generalist species have broad niches. They can live in many different places. They can eat a variety of foods and tolerate a wide range of environments. Flies, cockroaches, rats and humans are generalists. Specialist species have narrow niches. They live only in very specific environments. This makes them more prone to extinction when environmental conditions change. If the environment is constant, specialists have fewer competitors. Chinas giant panda is a specialist with a specialized diet of mostly bamboo.- Species can play four major roles within ecosystems1. Niches can be classified further in terms of specific roles that certain species play within ecosystems. A species can be described as native, nonnative, indicator, or keystone.2. Native species are those that normally live and thrive in a particular ecosystem.3. Nonnative species, also called invasive, alien, and exotic, are those that migrate into, or are deliberately or accidentally introduced into, an ecosystem.4. Nonnative species can threaten native species.- General types of species Indicator species provide early warnings of damage to a community or an ecosystem. Birds are excellent biological indicators because they are found almost everywhere and are affected quickly by environmental changes, such as loss or fragmentation of their habitats and introduction of chemical pesticides. Amphibian species are also believed to be indicator species. Keystone species are species whose roles have a large effect on the types and abundance of other species in an ecosystem, even though they may exist in relatively limited numbers in their ecosystems. Examples are the wolf, leopard, lion, some shark species, and the American alligator Native species : those species that normally live and thrive in a particular ecosystem. Non-native species : can be referred under other names, such as, invasive, alien and exotic species. These are deliberately or accidently introduced into, or migrate into, an ecosystem. - Species diversity and why it is important Species diversity includes the variety and abundance of species in a particular place Species richness: the number of different species in an ecosystem Species evenness: the relative abundance of individuals within each of those species Species-rich ecosystems tend to be productive and sustainable The more diverse an ecosystem is, the more productive it will be. The greater species richness and productivity will make an ecosystem more stable or sustainable: A complex ecosystem with many different species (high species richness) and the resulting variety of feeding paths has more ways to respond to most environmental stresses because it does not have all its eggs in one basket.II. SPECIES INTERACTION 1. Species interaction - Species interact in five major ways There are five basic types of interaction between species when they share limited resources: Interspecific competition occurs when two or more species interact to gain access to the same limited resources, e.g lions and hyenas Predation occurs when a member of one species (predator) feeds directly on all or part of a member of another species (prey), e.g Male leopard preying on Indian bison Parasitism occurs when one organism (the parasite) feeds on another organism (the host), usually by living on or in the host, e.g Parasitic wasp cocoons on hornworm Mutualism is an interaction that benefits both species by providing each with food, shelter, or some other resource, e.g Bees and many species of flowering plants. The flower becomes pollinated by the insect, while the bee receives food in the form of pollen and nectar Commensalism is an interaction that benefits one species but has little, if any, effect on the other, e.g Barnacles sticking to the tail of a whale- Interspecific competition Interspecific competition is the most common interaction between species. When two species use the same resource, their niches overlap. Resource partitioning occurs when species competing for similar scarce resources evolve specialized traits that allow them to use shared resources at different times, in different ways, or in different places. e.g. warblers who live in the same trees but have such specialized feeding niches that they do not compete. - Predation Predation occurs when a member of one species (predator) feeds directly on all or part of a living organism of another plant or animal species (prey), forming a predator-prey relationship. Herbivores can walk up to their prey. Carnivores have a variety of methods to capture their prey, such as: Pursuit and ambush. Camouflage to hide and ambush. Attack with chemical warfare.- Prey species with specialized ways of avoiding predators Prey have evolved ways to avoid predators. Ability to run, swim, or fly fast; highly developed senses of sight or smell that alert them to the presence of predators. Physical protection such as shells, thick bark, spines, and thorns. Camouflage. Chemical warfare such as poisonous, irritating, foul-smelling or bad tasting chemicals. Warning coloration. Many bad-tasting, bad-smelling, toxic, or stinging prey species are brightly colored, which helps experienced predators recognize and avoid them Mimicry is when a non-poisonous species looks like (mimics) like a species that is poisonous. Behavioral strategies such as attempting to frighten predators or living in groups such as herds of antelope or schools of fish.- Parasitism Parasitism occurs when one species (parasite) feeds on the body of, or the energy used by, another organism (host), usually by living on or in the host. A parasite usually is much smaller than its host and rarely kills it. Parasites can live the inside of the host, (e.g. tapeworms) or on the outside of the host (e.g. mistletoe, sea lampreys).- Mutualism Mutualism occurs when two species behave in ways that benefit both by providing each with food, shelter, or some other resource. Examples of mutualism include birds that ride on the backs of large animals, like African buffalo, and remove pests, and the bacteria that live in our intestines and help digest our food.- Commensalism Commensalism is an interaction that benefits one species but has little, if any, beneficial or harmful effect on the other. Epiphytes are plants that attach themselves to the trunks or branches of large trees for access to sunlight; these represent commensalism.

2. Limits of population growth - Populations can grow, shrink, or remain stable A population is a group of individuals of the same species living in a particular place. Population size may vary in cycles based on births, deaths, immigration, and emigration. Population change = (births + immigration) - (deaths + emigration). Physical or chemical limiting factors, such as light, water, and nutrients, can affect the number of individuals in a population. Population density can affect population size. In a dense population, parasites and diseases can spread more easily, and sexually reproducing individuals can find mates more easily.- Species have different reproductive patterns Some species have many, usually small, offspring and give them little or no parental care or protection. Some species have few, usually fairly large, offspring and invest parental care and protection.- No population can grow indefinitely Environmental resistance is the combination of all factors that act to limit the growth of a population. Environmental resistance largely determines an areas carrying capacity, the maximum population of a given species that a particular habitat can sustain indefinitely. Exponential growth starts slowly but then accelerates as the population increases. Occurs when a population has unlimited resources to support its growth. A graph of population size over time of an exponential growth has a J-shaped curve. Logistic growth occurs when the growth rate decreases as the population becomes larger and nears the carrying capacity of its environment because resources such as food, water, and space begin to dwindle. Population size may stabilize at or near the carrying capacity of its environment. The result is a sigmoid (S-shaped) population growth curve. - When a population exceeds its carrying capacity its population can crash A population crash, or sharp decline in size, can occur when a population uses up its resources and exceeds the carrying capacity of their environment. Population crashes occur because of a reproductive time lag, the period needed for the birth rate to fall and the death rate to rise in response to resource overconsumption. Population crashes are more likely when the organisms cannot switch to new resources or move to other locations.- Humans are not exempt from natures population controls Ireland recorded about 1 million human deaths and 3 million emigrants associated with the 1845 potato crop destruction. During the 14th century, the bubonic plague killed at least 25 million people. Between 1981 and 2007, AIDS killed more than 27 million people and continues to claim 2 million lives each year.- Communities and ecosystems change over time: Ecological succession Ecological succession is the gradual change in species composition in a given area. Primary ecological succession involves the gradual establishment of biotic communities in lifeless areas where there is no soil in a terrestrial ecosystem or no bottom sediment in an aquatic ecosystem. Secondary succession occurs with a series of communities or ecosystems with different species develop in places containing soil or bottom sediment. Such areas include: Abandoned farmland. Burned or cut forests. Heavily polluted streams. Flooded land.- Succession does not follow a predictable path The traditional view holds that succession proceeds in an orderly sequence along an expected path until a certain stable type of climax community occupies an area. The current view is that succession reflects an ongoing struggle by different species for resources such as light, water, nutrients, food, and space, and that mature, late-successional ecosystems in a state of continual disturbance and change, not a state of permanent equilibrium.- Living systems are sustained through constant change Living systems contain complex processes that interact to provide some degree of stability. This capacity to withstand external stress and disturbance is maintained by change in response to changing environmental conditions. One aspect of stability is inertia, or persistence, which is the ability of a living system, such as a grassland or forest, to survive moderate disturbances. A second aspect of stability is resilience, which is the ability of a living system to be restored through secondary succession after a more severe disturbance.- Six big ideas Populations evolve when genes mutate and give some individuals genetic traits that enhance their abilities to survive and to produce offspring with these traits (natural selection). Human activities are degrading the earths vital biodiversity by causing the extinction of species and by disrupting habitats needed for the development of new species. Each species plays a specific ecological role in the ecosystem where it is found. Certain interactions among species affect their use of resources and their population sizes. There are always limits to populations growth in nature. Changes in environmental conditions cause communities and ecosystems to gradually alter their species composition and population sizes (ecological succession).

LECTURE 3 : THE HUMAN POPULATION AND URBANIZATIONI. HUMAN POPULATION GROWTH * Human population growth continues but it is unevenly distributed For most of history, the human population grew slowly, but has been growing exponentially for the past 200 years. Reasons for this increase in growth rate include: Humans have expanded into almost all of the planets climate zones and habitats. The emergence of early and modern agriculture allowed us to grow more food for each unit of land area farmed. Death rates dropped sharply because of improved sanitation and health care. The rate of population growth has slowed, but the worlds population is still growing at a rate that added about 83 million people during 2011. Geographically, growth is unevenly distributed. About 2% of the 83 million new arrivals on the planet in 2011 were added to the worlds more-developed countries The other 98% were added to the worlds middle- and low-income, less-developed countries. At least 95% of the 2.6 billion people likely to be added to the worlds population between 2011 and 2050 will end up in the least-developed countries. * Factors affect human population size Birth rate, or crude birth rate, is the number of live births per 1,000 people in a population in a given year. Death rate, or crude death rate, is the number of deaths per 1,000 people in a population in a given year. Population change of an area = (births + immigration) - (deaths + emigration) The total fertility rate (TFR) is the average number of children born to women in a population during their reproductive years. Between 1955 and 2011, the average global lifetime number of births of live babies per woman dropped from 5 to 2.5. A TFR of 2.1 will eventually halt the worlds population growth.* Several factors affect birth rates and fertility rates A particular countrys average birth rate and TFR can be affected by: The importance of children as a part of the labor force. The cost of raising and educating children. The availability of, or lack of, private and public pension systems. Urbanization. The educational and employment opportunities available for women. The average age at marriage. The availability of legal abortions. The availability of reliable birth control methods. Religious beliefs, traditions, and cultural norms. * Several factors affect death rates People started living longer and fewer infants died because of increased food supplies and distribution, better nutrition, medical advances, improved sanitation, life expectancy, and safer water supplies. Two useful indicators of the overall health of people in a country or region are life expectancy and infant mortality rate The average global life expectancy increased from 48 years in 1955 to 70 years in 2011. In 2012 the life expectancy in Vietnam increased to 75.61 years (80.37 years for women and 71.07 years for men. Infant mortality is a measure of a societys quality of life because it reflects the general level of nutrition and health care. A high infant mortality rate can results from insufficient food (undernutrition), poor nutrition (malnutrition), and a high incidence of infectious disease, which is exacerbated by under- or malnutrition. While infant mortality rates in more-developed and less-developed countries have declined dramatically since 1965, more than 4 million infants die during their first year of life.* Migration affects an areas population size Migration is the movement of people into (immigration) and out of (emigration) specific geographic areas. Most people who migrate from one country to another are seeking jobs. Religious persecution, ethnic conflicts, political oppression, wars, and certain types of environmental degradation are also factors. Environmental refugees are people who migrate due to environmental degradation such as soil erosion and water and food shortages. One UN study estimated that a million people are added to this category every year.II. POPULATION AGE STRUCTURE & POPULATION CONTROL - A populations age structure helps us to make projections Age structure is the numbers or percentages of males and females in young, middle, and older age groups in a given population. Population age structure diagrams are made by plotting the percentages or numbers of males and females in the total population in each of three age categories: Prereproductive (014): normally too young to have children. Reproductive (1544): normally able to have children. Postreproductive (45+): normally too old to have children. Demographic momentum is rapid population growth in a country that has a large percentage of people younger than 15, and happens when a large number of girls enter their prime reproductive years. 1.8 billion people will move into their reproductive years by 2025. Most future human population growth will take place in less-developed countries due to their population age structure. The global population of seniors (age 65 and older) is increasing due to declining birth rates and medical advances that have extended life spans. - Populations made up mostly of older people can decline rapidly Japan has the worlds highest % of elderly people and the worlds lowest % of young people. Due to its discouragement of immigration, it may face a bleak economic future. The average age of Chinas population is increasing at one of the fastest rates ever recorded. This could lead to a declining work force, higher wages for workers, limited funds for supporting continued economic development, and fewer children and grandchildren to care for the growing number of elderly people.- Populations can decline from a rising death rate: the AIDS tragedy Between 1981 and 2010, AIDS killed more than 29 million people, and it takes about 2 million more lives each year (22,000 in the United States). AIDS kills many young adults and leaves many children orphaned, causing a change in the young-adult age structure of a country. This causes a sharp drop in average life expectancy, especially in several African countries where 1526% of the adult population is infected with HIV. AIDS can cause a pandemic loss of productive young adult workers and trained personnel.- There are three effective ways to slow population growth The three most effective ways to slow or stop population growth are: Reduce poverty Elevate the status of women Encourage family planning and reproductive health care.- Promote economic development As countries become industrialized and economically developed, their populations tend to grow more slowly. This demographic transition has four phases: Preindustrial Transitional Industrial Postindustrial Less-developed countries may transition to slower growth if modern technology can raise per capita incomes by bringing economic development and family planning. Rapid population growth, extreme poverty, and increasing environmental degradation in some low-income less-developed countriesespecially in Africacould leave these countries stuck in stage 2 of the demographic transition.- Empowering women can slow population growth Women tend to have fewer children if they are educated, have the ability to control their own fertility, hold a paying job outside the home, and live in societies that do not suppress their rights. Women account for 66% of all hours worked but receive only 10% of the worlds income and own just 2% of the worlds land. Women make up 70% of the worlds poor and 64% of its 800 million illiterate adults. Poor women who cannot read often have an average of 57 children, compared to 2 or fewer children in societies where almost all women can read.- Promote family planning Family planning provides educational and clinical services that help couples choose how many children to have and when to have them. Successes of family planning: Without family planning programs that began in the 1970s, the worlds population would be about 8.5 billion instead of the current 7 billion. Family planning has reduced the number of abortions performed each year and decreased the numbers of mothers and fetuses dying during pregnancy. Problems that have hindered success in some countries: 42% of all pregnancies in less-developed countries are unplanned and 26% end with abortion. An estimated 201 million couples in less-developed countries want to limit their number of children, but lack access to family planning services.III. URBANIZATION IMPACTS ON ENVIRONMENT - Scientists see three important urban trends An increasing percentage of the worlds people live in urban areas. Urban areas grow in two waysby natural increase due to births and by immigration, mostly from rural areas. Three major trends in urban population dynamics have emerged: The proportion of the global population living in urban areas increased from 2% in 1850 to 50% today, and is projected to be 70% by 2050. The numbers and sizes of urban areas are mushrooming. We now have cities with 10 million or more people (megacities or megalopolises) and will soon have hypercities with more than 20 million people. Megacities and hypercities are merging into megaregions that can stretch across entire countries. Poverty is becoming increasingly urbanized, mostly in less-developed countries. An estimated 1 billion people in less-developed countries live in urban slums and shantytowns. - Urbanization has advantages Cities are centers of industry, commerce, transportation, innovation, education, technological advances, and jobs. Urban residents in many parts of the world tend to live longer than do rural residents, and have lower infant mortality and fertility rates. Cities provide better access to medical care, family planning, education, and social services. Recycling is more economically feasible. Concentrating people in cities helps to preserve biodiversity. Central cities can save energy if residents rely more on energy efficient mass transportation, walking, and bicycling.- Urbanization has disadvantages Most urban areas are unsustainable systems. The typical city depends on large non-urban areas for huge inputs of matter and energy resources, while it generates large outputs of waste matter and heat. Most cities lack vegetation. Destroyed vegetation could have absorbed air pollutants, given off oxygen, provided shade, reduced soil erosion, provided wildlife habitats, and offered aesthetic pleasure. Many cities have water problems. Providing water to cities can deprive rural and wild areas of surface water and can deplete underground water supplies. Cities in arid areas that depend on water withdrawn from rivers and reservoirs behind dams will face increasing problems. Cities can have flooding problems for several reasons: Being built on floodplains or near low-lying coastlines. Covering land with buildings, asphalt, and concrete causes precipitation to run off quickly and overload storm drains. Destroying or degraded large areas of wetlands that have served as natural sponges to help absorb excess storm water. Flooding as sea levels rise because of projected climate. Cities in arid areas that depend on water bodies fed by mountaintop glaciers will face water shortages if global warming melts the glaciers.- Cities tend to concentrate pollution and health problems Cities produce most of the worlds air pollution, water pollution, and solid and hazardous wastes. High population densities can increase the spread of infectious diseases, especially if adequate drinking water and sewage systems are not available.- Cities affect local climates Cities tend to be warmer, rainier, foggier, and cloudier. Heat generated by cars, factories, furnaces, lights, air conditioners, and heat-absorbing dark roofs and streets creates an urban heat island surrounded by cooler suburban and rural areas. The artificial light created by cities affects some plant and animal species.- Life is a desperate struggle for the urban poor in less-developed countries At least 1 billion people live under crowded and unsanitary conditions in cities in less-developed countries. Slums are areas dominated by tenements and rooming houses where several people might live in a single room. Squatter settlements and shantytowns are on the outskirts of cities, and usually lack clean water supplies, sewers, electricity, and roads, and are subject to severe air and water pollution and hazardous wastes from nearby factories.- Cities can grow outward or upward Most people living in compact cities such as Hong Kong, China, and Tokyo, Japan, get around by walking, biking, or using mass transit such as rail or buses. In countries such as the United States, Canada and Australia, plentiful land and networks of highways have produced dispersed cities whose residents depend on motor vehicles for most travel. Largely because of urban sprawl, all Americans combined drive about the same distance each year as the total distance driven by all other drivers in the world, and in the process use about 43% of the worlds gasoline.- Motor vehicles have advantages and disadvantages They provide mobility and offer convenient and comfortable transportation. They can be symbols of power, sex appeal, social status, and success. Much of the worlds economy is built on producing motor vehicles and supplying fuel, roads, services, and repairs for them. Globally, automobile accidents kill approximately 1.2 million people a year and injure another 15 million people. They kill about 50 million wild animals and family pets every year. Motor vehicles are the worlds largest source of outdoor air pollution. They are the fastest-growing source of climate-changing CO2 emissions. At least a third of the worlds urban land and half of that in the United States is devoted to roads, parking lots, gasoline stations, and other automobile-related uses. People waste time sitting in traffic congestion.- Reducing automobile use is not easy, but it can be done A user-pays approach makes drivers pay directly for most of the environmental and health costs caused by their automobile use. An example of full-cost pricing is a tax on gasoline that covers the estimated harmful costs of driving. Gasoline revenues could be used to help finance alternatives to cars. Taxing gasoline heavily would be difficult in the U.S. for several reasons. Strong opposition from the public, and from transportation-related industries. The dispersed nature of most U.S. urban areas. Lack of fast, efficient, reliable, affordable mass transit options. Raise parking fees and charge tolls on roads, tunnels, and bridges leading into cities, especially during peak traffic times. Some cities promote car-sharing networks, which bill members monthly for the time they use a car and the distance they travel, and can decrease car ownership.- Some cities promote alternatives to cars The following are alternatives to cars, each with its own advantages and disadvantages: Bicycles Mass-transit rail systems in urban areas Bus systems in urban areas High-speed rail systems between urban areas (bullet trains)- We can make urban areas more environmentally sustainable and enjoyable places to live Smart growth encourages environmentally sustainable development requiring less dependence on cars, controls and directs sprawl, and reduces wasteful resource use, by using zoning laws and other tools to channel growth into areas where it can cause less harm. New urbanism involves less-developed villages within cities, so that people can live within walking distance of where the work, shop, and go for entertainment- Three big ideas The human population is increasing rapidly and may soon bump up against environmental limits. We can slow human population growth by reducing poverty, encouraging family planning, and elevating the status of women. Most urban areas are unsustainable, but they can be made more sustainable and livable within your lifetime.