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AP Environmental Science Population Dynamics, Carrying Capacity and Conservation Biology © Brooks/Cole Publishing Company / ITP.

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Presentation on theme: "AP Environmental Science Population Dynamics, Carrying Capacity and Conservation Biology © Brooks/Cole Publishing Company / ITP."— Presentation transcript:

1 AP Environmental Science Population Dynamics, Carrying Capacity and Conservation Biology © Brooks/Cole Publishing Company / ITP

2 1. Characteristics of Populations © Brooks/Cole Publishing Company / ITP Changes in population size, density, dispersion, and age distribution are known as population dynamics. Population size- the number of individuals in a population at a given time Population density- the number of individuals per unit area in terrestrial ecosystems or per unit volume in aquatic ecosystems Dispersion- the spatial patterning of individuals Age structure- is the proportion of individuals in each age group (e.g., prereproductive, reproductive, and postreproductive) of a population.

3 Characteristics of Populations © Brooks/Cole Publishing Company / ITP In terms of dispersion, individuals of a population can be clumped, uniform, or randomly distributed. CLUMPING MOST COMMON!!! (a) Clumped (elephants)(b) Uniform (creosote bush)(c) Random (dandelions) Figu re 9- 2 Pag e 164

4 2. Population Dynamics and Carrying Capacity © Brooks/Cole Publishing Company / ITP Population size is governed by births, deaths, immigration, and emigration: [Population Change] = [Births + Immigration] – [Deaths + Emigration] If the number of individuals added are balanced by those lost then there is zero population growth (ZPG) Populations vary in their capacity for growth, also known as biotic potential. Intrinsic rate of growth (r)- is the rate at which a population will grow if it had unlimited resources. Carrying capacity (K)- the number of individuals in a population that can be supported in a given area.

5 Population size (N) Time (t) Carrying capacity (K) Environmental resistance Biotic potential Exponential growth

6 Population Dynamics © Brooks/Cole Publishing Company / ITP Factors that tend to increase or decrease population size: Biotic potential and environmental resistance determines the carrying capacity Fig. 10–3

7 Population Density Density-dependent population controls- reliant on a dense population for effect: Pests Infectious diseases Competition for resources Predation Density-independent population controls- affect population size regardless of density: Weather Fire Habitat destruction Pesticides Pollution

8 Carrying Capacity There are always limits to population growth in nature. Carrying capacity (K) is the number of individuals that can be sustained in a given space The concept of carrying capacity is of central importance in environmental science If the carrying capacity for an organism is exceeded, resources are depleted, environmental degradation results, and the population declines. **Carrying capacity is determined by climatic changes, predation, resource availability and interspecific competition. © Brooks/Cole Publishing Company / ITP

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10 Exponential vs. Logistic Growth Exponential growth occurs when resources are not limiting. Logistic growth occurs when resources become more and more limiting as population size increases. Fig. 10–4 © Brooks/Cole Publishing Company / ITP

11 Exponential Population Growth © Brooks/Cole Publishing Company / ITP Exponential growth occurs when resources are not limiting. During exponential growth population size increases faster and faster with time Currently the human population is undergoing exponential growth Exponential growth can not occur forever because eventually some factor limits population growth. Fig. 10–4a

12 Logistic Population Growth © Brooks/Cole Publishing Company / ITP Logistic population growth occurs when the population growth rate decreases as the population size increases. Note that when the population is small the logistic population growth curve looks like exponential growth Over time, the population size approaches a carrying capacity (K). Fig. 10–4b

13 Exceeding the Carrying Capacity © Brooks/Cole Publishing Company / ITP During the mid–1800s sheep populations exceeded the carrying capacity of the island of Tasmania. This "overshoot" was followed by a "population crash". Numbers then stabilized, with oscillation about the carrying capacity. Population Crash Fig. 10–5

14 Exceeding the Carrying Capacity © Brooks/Cole Publishing Company / ITP Reindeer introduced to a small island off of Alaska in the early 1900s exceeded the carrying capacity, with an "overshoot" followed by a "population crash" in which the population was totally decimated by the mid–1900s. Fig. 10–5

15 Population Curves in Nature © Brooks/Cole Publishing Company / ITP Natural populations display a broad diversity of population curves. Stable- populations are relatively constant over time, fluctuating slightly above and below carrying capacity such as those in undisturbed tropical rain forests. Cyclic- population size changes over a regular time period. (e.g., seven–year cicada or lynx and snowshoe hare) Irruptive- characteristic of species that only have high numbers for only brief periods of times and then experience crashes due to seasons or nutrient availability such as algae and many insects Irregular- erratic and the reasoning is typically not understood. Fig. 10–6

16 © 2004 Brooks/Cole – Thomson Learning Number of individuals Time (b) Irruptive (a) Stable (c) Cyclic (d) Irregular

17 Population Curves in Nature © Brooks/Cole Publishing Company / ITP Population cycles for the snowshoe hare and Canadian lynx are believed to result because the hares periodically deplete their food, leading to first a crash of the hare population and then a crash of the lynx population. Fig. 10–8

18 3. Reproductive Strategies and Survival © Brooks/Cole Publishing Company / ITP Organisms can be divided into two categories of "strategies" for reproduction and survival: r–strategist species- tend to live in recently disturbed (early successional) environments where resources are not limiting; such species tend to have high intrinsic rates of growth (high r); K–strategist species- tend to do well in competitive conditions and live in environments where resources are limiting (later succession) They tend to have lower intrinsic rates of growth and characteristics that enable them to live near their carry capacity (population size near K). ***Figure 9-10

19 Number of individuals Time Carrying capacity K species; experience K selection r species; experience r selection K

20 r–Strategist Species © Brooks/Cole Publishing Company / ITP Characteristics of r– strategists, including production of many small and unprotected young, enable these species to live in places where resources are temporarily abundant. These species are typically "weedy" or opportunistic.

21 K–Strategist Species © Brooks/Cole Publishing Company / ITP Characteristics of K– strategists, including production of few large and well cared for young, enable these species to live in places where resources are limited. These species are typically good competitors. Fig. 10–7b

22 Survivorship Curves © Brooks/Cole Publishing Company / ITP Three kinds of curves: Late loss (usually K– strategists), in which high mortality is late in life Constant loss (such as songbirds), in which mortality is about the same for any age Early loss (usually r–strategists), in which high mortality is early in life. Fig. 10–9

23 4. Conservation Biology © Brooks/Cole Publishing Company / ITP Conservation biology- the interdisciplinary science that deals with problems of maintaining Earth's biodiversity, including genetic, species, and ecosystem components of life. Conservation involves the sensible use of natural resources by humans Three underlying principles: -Biodiversity and ecological integrity are useful and necessary for life and should not be reduced by human activity -Humans should not cause or hasten premature extinction of populations and species -The best way to preserve biodiversity and ecological integrity is to protect intact intact ecosystems and sufficient habitat.

24 Conservation Biology © Brooks/Cole Publishing Company / ITP Habitat fragmentation is the process by which human activity breaks natural ecosystems into smaller and smaller pieces of land called habitat fragments. one concern is whether remaining habitat is of sufficient size and quality to maintain viable populations of wild specie; large predators, such as grizzly bears, and migratory species, such as bison, require large expanses of continuous habitat habitat fragments are often compared to islands, and principles of island biogeography are often applied in habitat conservation.

25 5. Human Impacts on Ecosystems © Brooks/Cole Publishing Company / ITP Nine major human impacts on ecosystems: Fragmenting and degrading habitat, therefore reducing biodiversity Simplifying natural ecosystemsmonocultures reduce biodiversity Use or waste of an increasing percentage of Earths NPP that supports all consumers Unintentionally strengthening some populations of pest species and disease–causing bacteria Eliminating some predators Deliberately or accidentally introducing new species Overharvesting potentially renewable resources Interfering with chemical cycling and energy flows. Increasing dependence on nonrenewables

26 Figure 9-13 Page 172 PropertyNatural SystemsHuman-Dominated Systems Complexity Energy source Waste production Nutrients Net primary productivity Biologically diverse Renewable solar energy Little, if any Recycled Shared among many species Biologically simplified Mostly nonrenewable fossil fuel energy High Often lost of wasted Used, destroyed, or degraded to support human activities

27 Human Impacts on Ecosystems © Brooks/Cole Publishing Company / ITP Some principles for more sustainable lifestyles: We are part of, not apart from, Earth's dynamic web of life Our lives, lifestyles, and economies are dependent on the sun and earth We never do merely one thing Everything is connected to everything else; were are all in it together. According to environmentalist David Brower we need to focus on global CPR –– that's conservation, preservation, and restoration.

28 Principles of Sustainability How Nature WorksLessons for Us Runs on renewable solar energy. Recycles nutrients and wastes. There is little waste in nature. Uses biodiversity to maintain itself and adapt to new environmental conditions. Controls a species population size and resource use by interactions with its environment and other species. Rely mostly on renewable solar energy. Prevent and reduce pollution and recycle and reuse resources. Preserve biodiversity by protecting ecosystem services and preventing premature extinction of species. Reduce births and wasteful resource use to prevent environmental overload and depletion and degradation of resources. Solutions

29 6. Ecosystem Restoration © Brooks/Cole Publishing Company / ITP Can we restore damaged ecosystems? Yes, in some cases; but prevention is easier Natural restoration is slow relative to human life spans Active restoration can repair and protect ecosystems, but generally with considerable effort and expense Example: in Sacramento, California, rancher Jim Callender restored a wetland by reshaping land and handplanting native plants; many of the native plants and animals are now thriving there Restoration requires solid understanding of ecology It is not possible to undo all ecological harm, e.g., we can't foster recovery of an extinct species.


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