EVRExam2Review PDF

Without constraints, population growth can be rapid. Biotic Potential: Refers to unrestrained biological reproduction. Exponential Growth Rates -> Indicated by a j-shaped curve, - Represented by the formula: 𝑁𝑁𝑇𝑇 = 𝑁𝑁0 𝑟𝑟 𝑡𝑡 where r is the growth rate, T is time, 𝑁𝑁𝑇𝑇 is the...

Without constraints, population growth can be rapid. Biotic Potential: Refers to unrestrained biological reproduction. Exponential Growth Rates -> Indicated by a j-shaped curve, - Represented by the formula: 𝑁𝑁𝑇𝑇 = 𝑁𝑁0 𝑟𝑟 𝑡𝑡 where r is the growth rate, T is time, 𝑁𝑁𝑇𝑇 is the population total and 𝑁𝑁0 is the starting population. - A shortcut for calculating rate of growth in this scenario is the “rule of 70” which is calculated by dividing 70/r, which equals a “doubling time” which is the time it takes for the starting population to double. - Exponential growth leads to overshoots and diebacks – a “boom and bust” cycle Carrying Capacity – The number (or the biomass) of a species that can be supported in a certain area without depleting resources. Sometimes, when population growth nears the carrying capacity, the growth rate slows down. - The slowing rate of growth is represented by a “logistic growth” model and it produces an s-shaped curve. Recall from your previous notes that there are factors that impact population growth. Let’s review these below: Biotic vs. Abiotic Factors: Biotic (life-based factors) and abiotic (not life-based factors) Density-Dependent Factors – Based on population size. - Overcrowding, disease rates, stress, predation, food availability Density-Independent Factors – Not based on population size. - Drought, fire, habitat loss, other natural disasters Intrinsic factors – Internal to the organism (such as slow reproductive rates) Extrinsic factors – External to the organism (natural disasters, predators, competition which can be both intraspecific (members of the same species compete for resources) and interspecific (members of different species compete for the same resources). Reproductive Strategies – R-Selected (r-adapted) species – high reproductive rates, high mortality rates, don’t care for offspring, low trophic levels, generalists, booms and busts K-Selected (k-adapted) species – fewer young produced/conservative reproduction, late sexual maturity, longer generations, few predators and higher trophic levels -- When we study population in the way a demographer would study it, a formula of factors is used to describe the rate of growth. “BIDE” = (births + immigration) – (deaths + emigration) -- The Equilibrium Theory of Biogeography - Diversity in isolated islands depends on rates of colonization and extinction. - The rate of colonization depends on proximity of the island to another source of species such as a continent. - The rate of extinction depends on the size of the island and the population it can support. Why? Small populations are less likely to thrive after environmental disturbances and isolated populations cannot be replenished by immigration. -- In large populations, genetic variation tends to remain stable, provided environmental conditions remain stable. A shift of traits can occur if there is an environmental change. Genetic Drift – Gradual changes in gene frequencies due to random events. Unit 7 – Recall that many factors contribute to population growth -> fertility (births), mortality (deaths), life space, life expectancy Life Span – The oldest age to which members of the species survive. Life Expectancy – The average age a newborn can expect to attain in any given society. This has gotten longer historically due to improved sanitation, nutrition and education. Human growth has been historically exponential. Thomas Malthus (1798) wrote that human growth is exponential and is checked by famine, disease and cultural factors. - Mathus contended that human population growth causes environmental degradation. - He also predicted that population growth would be slowed by a lack of food production capabilities. Karl Marx contended that human population growth leads to resource depletion, pollution, overcrowding and employment when in conjunction with poverty (which is caused by oppression and exploitation). This leads to starvation, disease, crime, misery and subsequently war. Technology can boost carrying capacity, as we make progress in agriculture, engineering, commerce and medicine -> makes it possible to support more people per unit area. Environmental Effects of Population Calculated by the formula I = PAT where I is the environmental impact, P is population size, A is affluence and T is technology. Thus, increasing population size, affluence and technology also increases environmental impact. Demography – The study that encompasses vital statistics such as births, deaths, distribution, and population size. Fertility and Birth Rates can be measured using several statistical values – - Crude Birth Rate – Number of births in a year per thousand. - Total Fertility Rate – Number of children born to an average woman in a population during her life. - Replacement Fertility Rate – Occurs when birth rates just compensate for deaths. Other Terms: Crude Death Rate – Number of deaths per thousand persons in a given year. Natural Increase – Crude Birth Rate – Crude Death Rate Total Growth Rate includes immigration, emigrations, births and deaths. -- Patterns can be perceived in death rates and birth rates due to changes in living conditions related to economic development. This is represented by a demographic transition. Stages: (1) Pre-Modern Society – Poor conditions keep death rates high while birth rates are correspondingly high. (2) Economic Development – Economic development brights better standard of living and death rates fall. Birth rates remain constant or rise. (3) Mature Industrial Economy – Birth rates begin to fall as people see that most of their children survive. Populations continue to grow due to population momentum. (4) Developed Countries – Transition is now complete and both death and birth rates are low and population is in equilibrium. What are the conditions necessary for a demographic transition to occur? - Improved standard of living. - Confidence that children will survive. - Improved status of women. - Availability and use of birth control. Countries in various stages can be demonstrated on Age Structure Histograms. In societies, ideal family size can be influenced by both pronatalist and birth reduction pressures. Family planning allows couples to determine the number and spacing of their children. Climate and Air Pollution Atmospheric Composition – Nitrogen (N2) ~78%, Oxygen (O2) ~21%, Argon