NOTES: CH 5 Populations

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1 NOTES: CH 5 Populations 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: (BD) + (IE) 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

2 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: Densitydependent factors: intensify as pop. size increases (plants) accumulation of wastes (hormonal changes, aggressiveness, delay in sex. maturation) Densityindependent factors: Densityindependent factors are unrelated to pop. Size freeze; cooler temps extreme heat, etc. *Most ecologists agree that a combination of factors limits pop. size 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

3 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. QUESTION TO PONDER: When will the Earth reach it's carrying capacity for humans and what will happen when it does? 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 u farming and agriculture: remove nutrients from one area; they appear in other areas u sewage, factory wastes, livestock runoff, fertilizer leaching all lead to accelerated eutrophication of lakes (excess growth of photosynthetic organisms) u 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 u combustion of fossil fuels and burning of wood / deforestation

4 u temperature increases w/ increased CO2 u possible scenarios: ; flooding; warming trend Depletion of Ozone: u ozone forms a protective layer in stratosphere that absorbs UV radiation u accumulation of CFC s (used in aerosol propellants and refrigerants) is destroying ozone u possible consequences: unpredictable effects on crops unpredictable effects on phytoplankton Exploding Human Population: Where will we all live? HABITAT DESTRUCTION! u only 15% of original forest and 1% of original tallgrass prairie remain in US u tropical rainforests are cut at a rate of 500,000 km 2 per year; will be gone in approx 20 years u 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 decomposers break down dead material into nutrients the plants can use a rainforest tree grows from nutrients in the soil released by decomposers a sloth eats the leaves of this tree insects live on the sloth **Living things create niches for other living things!!

5 Importance to Humans:, 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 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.