<p> NOTES: CH 5 – Populations</p><p>POPULATION: - -influenced by similar environmental factors Populations are… -shaped by:  (between individuals and their environment)  (can modify characteristics within a population) Population Characteristics:  Geographic Range / Boundaries ( )  Population size  Density (# of individuals per unit area/volume) -ex:  Dispersion ( among individuals) Measuring Density  random sampling / estimation -count individuals in a representative area - (nests, burrows, droppings, tracks, etc.) Factors Affecting Growth & Decline of a Population ● increases in pop. size: ● decreases in pop. size: (mortality) Change in Population Size = **Consider this…. ● A population of moose had 100 individuals. Over the course of the year, there were 29 births and 34 deaths. Also, 5 moved into the area while 15 left the area. What was the change in the population that year? How many moose are left in the population? SOLUTION : B = D = I = E = Remember the equation: (B-D) + (I-E)</p><p>So how much of the original population is left? Did the population increase, decrease, or stay the same? What happens to the population size if… ● If more organisms are born than die… - ● If birthrate = death rate… - ● Death rate exceeds birthrate… - ● Population Growth Models: Exponential vs. Logistic Growth Exponential Growth Model ● , there will be exponential growth of a population: EXPONENTIAL GROWTH: ● Occurs when there are - - ● Population size increases ● Individuals can reproduce at a constant rate ● if nothing stops a population from growing, it is undergoing exponential growth ● a natural population cannot continue with exponential growth for long  WHY? -- there are limiting factors to continuous growth such as space, food, & competition CARRYING CAPACITY: -property of the environment -varies over space and time with abundance of resources Logistic Growth vs. Exponential Growth ● Exponential growth = ● Logistic growth = ● Logistic growth occurs after a period of exponential growth ● What causes a population growth to stop / slow? - ! (a.k.a. ) Population Limiting Factors: Density-dependent factors: intensify as pop. size increases</p><p>- - - - - (plants) - -accumulation of wastes - (hormonal changes, aggressiveness, delay in sex. maturation) - - Density-independent factors: Density-independent factors are unrelated to pop. Size - -freeze; cooler temps -extreme heat - , etc. *Most ecologists agree that a combination of factors limits pop. size </p><p>5.3: HUMAN POPULATION GROWTH ● DEMOGRAPHY: -Growth rate -Age structure -Geographic structure (who lives where?) ● Human Population Growth is an exception to what we consider a "natural population" ● the human population, like other populations, has increased over the course of time ● about 500 years ago, the world's population started growing - WHY? , , etc. – all led to increased longevity of people ● as of 2001, the human population is over 6 billion; this is double what it was 40 years ago!!!! ● It took over 10,000 years for human population to increase to 1 billion people ● It then took a little over a century to reach 2 billion ● Then, !! Since the early 1800’s, the human population on Earth has been growing exponentially. ● The primary cause -little to do with an increase in birth rate -main cause = -improved medicine, agriculture, and living conditions -people have begun to live longer and healthier lives ● they produce that are more likely to survive to adulthood ● produce even more children… ! ● On average, each person in the United States uses than a person from another country…food for thought.</p><p>QUESTION TO PONDER: When will the Earth reach it's carrying capacity for humans and what will happen when it does?</p><p>NOTES: CH 6 – Humans in the Biosphere ● Humans affect regional and global environments (including soil, water, and the atmosphere) through: - - - Sustainable Development: ● RENEWABLE RESOURCES: by a healthy ecosystem (i.e. some trees that grow quickly) ● NONRENEWABLE RESOURCES: natural processes within a reasonable amt. of time (i.e. , , , etc.) 6.2: Human Impacts on Ecosystems Disruption of nutrient cycling ◆ farming and agriculture: remove nutrients from one area; they appear in other areas ◆ sewage, factory wastes, livestock runoff, fertilizer leaching all lead to accelerated eutrophication of lakes (excess growth of photosynthetic organisms) ◆ dumped into ecosystems -many cannot be degraded; persist for years - as they are passed up through successive trophic levels -top level carnivores most affected -ex: DDT (pesticide); banned in US (1971) “ ” Carbon dioxide emissions / Greenhouse Effect ◆ combustion of fossil fuels and burning of wood / deforestation </p><p>◆ temperature increases w/ increased CO2 ◆ possible scenarios: - ; flooding; warming trend</p><p>Depletion of Ozone: ◆ ozone forms a protective layer in stratosphere that absorbs UV radiation ◆ accumulation of CFC’s (used in aerosol propellants and refrigerants) is destroying ozone ◆ possible consequences: - -unpredictable effects on crops -unpredictable effects on phytoplankton Exploding Human Population: Where will we all live?…HABITAT DESTRUCTION! ◆ only 15% of original forest and 1% of original tallgrass prairie remain in US ◆ tropical rainforests are cut at a rate of 500,000 km2 per year; will be gone in approx 20 years ◆ development, logging, war, oil spills, etc. The main threat of habitat destruction is the ! 6.3: BIODIVERSITY ● BIODIVERSITY: the ● How do we measure BIODIVERSITY? -measure / count the Example: 1 acre corn field vs. 1 acre rainforest Corn field: Rainforest: . . . . Importance of Biodiversity: ● The presence of different forms of life make our planet beautiful…but why else is biodiversity important? Importance to Nature: ● if a species of lost from an ecosystem, other living things will be affected ● ; ● change ● animals can’t exist without plants ● flowering plants can’t reproduce without their animal pollinator / partner Importance to Nature: EXAMPLE è decomposers break down dead material into nutrients the plants can use è a rainforest tree grows from nutrients in the soil released by decomposers è a sloth eats the leaves of this tree è insects live on the sloth **Living things create niches for other living things!! Importance to Humans:</p><p>● , and CO2 is removed from the air by diverse species of plants & algae ● biodiversity gives humans a diverse diet (beef, chicken, tuna, shrimp; multiple & diverse plant products from almonds to zucchini!) ● humans rely on biodiversity for materials used in clothing, furniture, buildings ● improving human health: most pharmaceuticals are synthesized to mimic naturally occurring chemicals discovered in living things EXAMPLES: Loss of Biodiversity: ● EXTINCTION: ; when the last of its members dies 6.4: Meeting Ecological Challenges ● ECOLOGICAL FOOTPRINT: describes the total area of land and water ecosystems needed to provide the . an individual uses and to absorb the that individual generates -includes: the , the , where you live, the electricity / gas you use, etc</p><p>Comparing Footprints: ● the average American has an ecological footprint than the global average. ● by contrast, the African nation of Zambia has a footprint approx. A Sustainable Future…? ● We can follow these steps to help us toward a sustainable future: 1) in the environment 2) to determine the cause, and then: 3) Using scientific understanding to & have a positive impact on the global environment.</p>