Chapter 1 - exam review notes - Human Impact on the Environment PDF

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Chapter 1: Environment: is more than water, land, and air; it is the sum total of our surroundings.  Includes all of earth’s biotic components (living things), as well as the abiotic components (non-living things).  Biotic >animals, plants, forests, soils, people  Abiotic >continents, clouds, rivers, oceans, icecaps Natural resources: the various substances and energy sources we need to survive.  Replenishable resources are known as renewable natural resources. i.e. sunlight, wind, wave energy, etc.  In contrast, nonrenewable natural resources, like fossil fuels and mineral deposits. Formed much more slowly than we use them. Four Significant Periods of Societal Change 1) Paleolithic Period/ Old Stone Age: (2.5 million years ago) humans gained control of fire and began to shape stones as tools with which to modify their environment. 2) Neolithic Period/ Agricultural Revolution: (10,000 to 12,000 years ago) humans transitioned from hunter-gatherer to a settled agricultural way of life. 3) Industrial Revolution: (mid 1700’s) shift from rural agricultural life style to modern urban society powered by fossil fuels. Created a better quality of life but came with many adverse health and environmental risks. 4) Medical-Technological-Revolution: (Today) advances in medicine and sanitation and shift towards a green movement. 

Scientific method: a technique for testing ideas with observations, it involves several assumptions and a series of interrelated steps, including making observations, formulating questions, stating a hypothesis, generating predictions, testing predictions, and analysing the results from the tests.

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Geography uses the approaches and insights of numerous disciplines from the natural sciences and social sciences

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Systems are networks for interacting components that generally involve feedback loops, show dynamic equilibrium, and result in emergent properties. Earths natural systems are complex, so environmental scientists often take a holistic approach to studying environmental systems. Atmosphere-air/ Hyrdrosphere-water/ Geosphere-land/ Cryosphere-ice/ Biosphere-life/ Anthrosphere- humans Ecosystem: consists of all organisms and nonliving entities that occur and interact in a particular are at the same time. o Energy flows in one direction through ecosytems, whereas matter is recycled. o Energy is converted to biomass, and ecosystems vary their productivity Nutrients are elements and compounds that organisms consume and require for survival. Input of nutrients can boost productivity, but an excess of nutrients can alter ecosytems in ways that cause severe ecological and economic consequences. Water moves throughout the global environment as a result of processes in the hydrologic cycle The carbon flux between organisms and the atmosphere occurs via photosynthesis and respiration. Most carbon is contained in sedimentary rock, but substantial amounts also occur in the oceans and soils Nitrogen is a vital nutrient for plant growth. Phosphorus is most abundant in sedimentary rock, with substantial amoint in soil and the oceans.

Chapter 3: Population is determined by four factors:

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Births within a population, natality Deaths within a population, mortality Immigration Emigration

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Populations are characterized by population size, population density, population distribution, sex ration, age structure, and birth/death rates.

Natural rate of population growth: The rate of change in a population’s size resulting from birth and death rates alone, excluding migration. Crude birth rate - Crude death rate = Natural rate of population growth This reflects the degree to which a population is growing or shrinking as a result of its own internal factors. Population growth rate: An increase in the size of a population, or group of individuals of a particular species in a given location, at a given time. The effects of migration are taken into account. (Crude birth rate - Crude death rate) + (Immigration rate - Emigration rate) = Population growth rate Exponential growth: The increase of a population (or of anything)by a fixed percentage each year; geometric growth; contrasting with linear growth.  

Populations unrestrained by limiting factors will undergo exponential growth until they meet environmental resistance. Logistic growth describes the effects of density dependence; exponential growth slows as population size increases, and pop size levels off at a carrying capacity.

K-selection and r-selection describe theoretical extremes in how organisms call allocate growth and reproduction.  K-selected species are so named because their populations tend to stabilize over time at or near their carrying capacity. o natural selection favours individuals that invest in producing offspring of high-quality that can be good competitors. o Ex. Humans, girrafes, elephants  R-selected species have high biotic potential and produce a large number of offspring in a relatively short time, but do not care for their young after birth. o Often below carrying capacity o Ex. Frogs, insects Linear growth: The increase of a population (or of anything) by a fixed amount each year; arithmetic growth; contrasting with exponential growth

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Life is organized hierarchically, starting with the atoms, molecules, and cells that make up individual organisms o Habitat, niche, and specialization are important ecological concepts

Chapter 4: Ecological communities: a community is a group of populations of organisms living in the same place at the same time. As organisms feed on one another, the energy within them moves through the community or through the trophic levels (animal hierarchy).  Producers or ‘Autotrophs’ compose the first trophic level. Examples are algae, other green plants that capture sunlight to produce sugars. 

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Consumers or ‘Heterotrophs’ derive their food energy from other organisms. Consumers eat producers., these are known as primary consumers and compose the second trophic level. Examples include grazing animals like deer/grasshoppers. o Secondary Consumers pray on primary consumers. E.g. wolves praying on deer. These make up the third trophic level o Tertiary Consumers are predators that feed at even higher trophic levels. Ex An owl feeding on a rodent that has fed on a grasshopper. These make up the 4th trophic level. Most primary consumers are herbivores, and secondary/tertiary are carnivores. Omnivores eat both meat and plant Detritivores consume non-living matter. An example is a soil insect scavenging waste of dead animals/plants Decomposers such as fungi or bacteria break down leaf liter and other nonliving matter to consume. These organisms play a major ‘recycling’ role within a community. Most energy that organisms use is lost through respiration. Only a small amount is transferred to the next trophic level.

Earth’s Biomes A biome is a major regional complex of similar communities – recognized primarily from its dominant plant vegetation. I.e forests, deserts. The world is divided into roughly 10 terrestrial biomes: 1) Tundra: dry biome, but located at very high latitudes. Very cold winters, and little daylight.

2) Boreal forest: coniferous or evergreen trees, forests develop in cooler, long cold winters and short cool summers 3) Temperate deciduous forest: precipitation is spread evenly throughout the year, soils fertile. 4) Temperate grassland: temperature differences between winter and summer become more extreme and rainfall diminishes. 5) Temperate rainforest: potential to produce large volumes of commercially important forest products (lumber and paper). Interior forest is shaded and damp. 6) Tropical rainforest: areas of high rainfall grow rainforests, intermediate rainfall host dry or deciduous forests, and areas of lower rainfall become dominated by grasses. 7) Tropical dry forest: warms year round but where rainfall is lower overall, rains can be extremely heavy and accompanied by erosion. 8) Savannah: precipitations arrives during distinct rainy seasons and concentrates grazing animals near widely spaced water holes. 9) Desert: driest biome on earth, desert animals and plants have evolved many adaptations to deal with the harsh climatic conditions. 10)Mediterranean: scrub woodlands. Chapter 5: Soil is a complex plant supporting system that consists of weathered rock, organic matter, water, gases, nutrients, and microorganisms  Soil as a resource is renewable if managed carefully  Soil includes living and dead microoganisms as well as decaying material derived from plants and animals.  Processes most responsible for soil formation are weathering, erosion, and the deposition and decomposition of organic matter. o Weathering of parent material is the first step in soil formation. o Rock is broken down into smaller, finer particles.    

Partial decomposition of organic matter creates humus, a dark spongy, crmbly mass of material made up of complex organic compounds (productive for plant life) Peat is a soil dominated by partially decated and compressed organic material Five factors that influence soil formation include climate, organisms, topography, parent material and time. Each layer of soil is known as a horizon.

Soil plays a crucial role in the nitrogen cycle by hosting free-living and symbiotic microorganisms that mediate nitrogen fixation, nitrification, and denitirification.  Soil represents the largest terrestrial reservoir for carbon in the active carbon cycle.

Healthy soil is vital for agriculture, for growth or forests, and for the biogeochemical functioning of earths natural systems, including the climate system.  Successful agriculture and a secure food supply require healthy soil  As the human population grows, pressures from agriculture and other activities are degrading earth’s soil, and we are losing topsoil from productive cropland at an unsustainable rate. o The main mechanisms of soil loss are slash, sheet, rill and gully erosion by water, and deflation, and abrasion by wind.  

Desertification: is a natural process by which formerly productive land becomes a desert as a result of climatic change or prolonged drought Crop rotation: The practice of alternating the kind of crop grown in a particular field from one season to the next

Techniques such as crop rotation, contour farming, intercropping, terracing, shelterbelts, and reduced tillage can help protect soil from erosion.

Chapter 6: Agriculture is the practice of raising crops and livestock for human use and consumption. o Major achievement and technological leap forward by humans. o Transition to a sedentary lifestyle based on agriculture increased the carrying capacity of land and led to a significant increase in population. Over the past half century, our ability to produce food has grown even faster than population. o However, throughout the years less food is being produced. o We face undernourishment, overnutrition and malnutrition daily. Green revolution o Began around 1950 o Goal was to increase agricultural productivity per unit area of land to feed the worlds people. o Agricultural scientists used selective breeding to develop strains of crops that grew quickly,, were more nutritious, or were resistant to disease or drought. o Greatly expanded use of fossil fuels, chemical fertilizers, and irrigation led to enormous increases in productivity, but also caused unintended environmental consequences, including pollution and soil degradation. Pests and pollinators

o Pest is an organism that damages crops that are valuable to us, and a weed is any plant that competes with crops. o To prevent pest outbreaks and weeds people have developed artificial chemicals to kill them off. o Pesticides: poisons that target pest organisms o Despite the toxicity of these chemicals, pests have evolved resistance to them. o Insects and other organisms are essential for ensuring the reproduction of many of our crop plants o Conservation of native pollinating insects is vitally important for our food supply Genetically modified food o Genetic modification depends on the technology of recombinant DNA. Genes containing desirable traits are moved from one type of organism into another. o Modification through genetic engeneering is both like and unlike traditional selective breeding o GM crops may have ecological impacts, including the spread of transgenes and indirect impacts on bio-diversity. o Little evidence so far for human health impacts from GM foods

Chapter 7: Five major factors affecting biodiversity loss: 1) Habitat alteration: greatest cause of biodiversity loss. o Primary source of population decline o Farming replaces diverse natural communities with simplified ones with only a few plant species o Clearing forests removes food, shelter, and other resources that forest-dwelling organisms need to survive o Urbanization and suburban sprawl supplant diverse natural communities with simplified human-made ones, driving many species from their home o Organisms are adapted to their environment so any major change will make it less suitable for them… Other organisms, human-induced changes are beneficial o All habitats in every biome are affected by human alteration (mostly for agriculture) 2)

Invasive Species: o Non-native species introduced to new environments has pushed some native species toward extinction (accidental = zebra mussels, escaped pets/food, weed seeds or intentional = food crops, domesticated animals during colonization)

o Native island species are particularly vulnerable because they are isolated with very few predators, parasites, or competitors – no evolution of defence for resistance o Those invasive species with survive tend to flourish if there is a lack of predators/parasites which attack them back home or a lack of competitors – when released from this, an introduced species may increase rapidly, spread, and displace native species o Invasive species cause billions of dollars in economic damage each year 3) o o o o

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Pollution: Air pollution can degrade forest ecosystems Water pollution can adversely affect fish and amphibians Agricultural runoff (fertilizers, pesticides, sediments) can harm many terrestrial and aquatic species Heavy metals, PCB, endocrine-disrupting compounds and various other toxic chemicals can poison both people and wildlife (e.g. oil/chemical spills – effects are dramatic and well known) Contaminants transported by atmospheric and oceanic processes from low latitudes could threaten the survival of polar bears Severe consequences, but generally less damage than habitat alteration or invasive species

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Overharvesting: o Most species, overhunting/harvesting by humans is not a big deal but for some it can cause them to become extinct – e.g. the polar bear (large in size, few in number, long-lived, few young per year… K-strategist species which is vulnerable to population reduction by hunting) o Traditional Inuit hunters carefully monitor and balance their harvest, using every part of the animal. Polar bears used to be hunted for sport, now it is closely monitored by arctic nations e.g. Canada, Russia, etc. o Led to steep declines in other K-selected animals such as the Atlantic grey whale (extinct) and other whales are threatened/endangered o Black market poaching and sale of wildlife contraband contributes to the problem o E.g. tigers – used to be 8 species, now only 5 and those are extirpated from much of their natural range. Tiger body parts get high price on the black market o E.g. gorillas/other primates – killed for meat, may be extinct soon o E.g. sharks – thousands killed every year for shark fin soup o Today, the ocean contains only 10% of the large animals it once did

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Climate Change: o Our manipulation of earth’s climate is starting to have global impacts on both habitat and biodiversity – greenhouse gas emissions trap heat in the

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atmosphere, warming the average temperatures worldwide and modifying global weather patterns/increasing the frequency of extreme weather events Thought to accelerate and become more severe over time Effects on plants and animals – droughts put stress on populations, warming temperatures force species to move toward higher altitudes/the poles. Some species will be able to adapt but others will not be able to move and will perish (e.g. trees may not be able to move to the poles fast enough, polar bears are losing ice to hunt on with no replacement (cannot move any further north) There many be changes in community composition with different prey, predators, and parasites they are not adapted to A 1.5-2.5 degree temperature increase could put 20-30% of the world’s plants and animals at increased risk of extinction

Growth in population and growth in consumption are the ultimate root causes behind the proximate threats to biodiversity. Chapter 8:      

Forests covers roughly 31% of earths land surface. Trees have the same basic requirements as other plants: sunlight, water, nutrients, air, and an amenable temp. There are 3 main sets of forest biomes: northern or boreal forests; temperate forests; and tropical forests. Forests provide habitat and support biodiversity. Contribute to ecosystem services that are of great value to people, including protection of the climate system and the hydrologic cycle, carbon storage and oxygen cycling. Deforestation is happening rapidly in places such as brazil, Indonesia and part of West Africa

Forests have been cleared since the beginnings of human civilization for a wide variety of reasons.  Developed nations deforested much of their land during the process of settlement, farming and industrialization.  Agriculture has contributed greatly to deforestation and has had enormous impacts on landscapes and ecosystems worldwide  Deforestation is taking place most rapidly in developing nations, driven by proximate factors such as logging and pest infestations and by root factors that are largely economic or political. Methods of harvesting timber

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Harvesting methods of timber include clear cutting and other even aged techniques, as well as selection stratergies that maintain uneven aged stands that are more closely resemble natural forest. Harvesting timber and other forest products can be sustainable as lomg as the principle of maximum sustainable harvest is maintained, so the stock does not become depleted.

Ecosystem based management  Attempts to manage the harvesting of resources in ways that minimize impact on the ecosystems and ecological processes of forest.  In Canada ecosystem based management aims to preserve health structure, functions, composition, and biodiversity.  Forest managers increasingly focus not only on extraction of forest products, but also on sustaining the ecological systems that make resources available.  Forest managers are beginning to implement ecosystem based management and adaptive management. Fire is a natural phenomenon  Ecological research shows that many ecosystems depend on fire, particularly in the boreal forest.  To reduce fuel load and improve the health and safety of forests, forest management agencies have in recent years been burning areas of forest under carefully controlled conditions.  Salvage logging is the removal of dead trees, or snags, following a natural disturbance. o Reduces future fire risks by removing woody debris that could serve as fuel for the next fire. Chapter 9: Freshwater is water that is relatively pure, with few dissolved salts. o Only 2.5% o Tied up in glaciers, icecaps, and underground aqufers. Rivers and streams (a surface water body) Water flow typically runs as follows; rain/snowmelt/spring → streams/creek/brooks → rivers → ocean Tributary - a smaller river flowing into a larger one Drainage Basin/Watershed - the area of land drained by a r...