APES quiz on pages 112-122
Population Change=
(Births + Immigration) - (Deaths + Emigration)
Several different types of population change occur in nature. Four general patterns of variation in population size:
Stable, Irruptive, Cyclic, and Irregular. (Seals Initiate Conflict Irregularly)
Why clumps?
species tend to cluster where resources are available, individuals moving in groups have a better chance of encountering resources than they would searching for their resources on their own, protection from predators, and living in packs give some predator species a better chance of getting a meal
Exponential growth
starts slowly but then accelerates as the population increases because the base size of the population is increasing. Plotting the number of individuals against time yields a J-shaped curve
limiting factor principle
too much or too little of any physical or chemical factor can limit or prevent growth of a population, even if all other factors are at or near the optimal range of tolerance
Some factors can limit population size...
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stability
capacity to withstand external stress and disturbance...maintained only by constant change in response to changing environmental conditions
Three ways in which members of a population are dispersed in their habitat
clumped, uniform, and random
Most populations live together in ____
clumps
Two aspects of stability in living systems:
inertia/persistence and resilience
Primary ecological succession
involves the gradual establishment of biotic communities in lifeless areas where there is no soil in a terrestrial ecosystem or no bottom sediment in an aquatic ecosystem. Ex: newly created shallow pond or reservoir, newly cooled lava, abandoned highway or parking lot, and bare rock exposed by a retreating glacier. Primary succession usually takes hundreds to thousands of years because of the need to build up fertile soil or aquatic sediments to provide the nutrients needed to establish a plant community
Population's Age Structure
its distribution of individuals among various age groups. This can have a strong effect on how rapidly it increases or decreases in size
Some factors that can kill members of a population are density independent- their effect is not dependent on the density of the population. Ex: floods, pollution, habitat destruction, hurricanes, etc...
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Environmental resistance
the combination of all factors that act to limit the growth of a population.
Population density
the number of individuals in a population found in a particular area or volume.
Bottom up population regulation
the size of the predator and prey populations is controlled by the scarcity of one or more resources
Ecological Succession
Ecological Succession: the normally gradual change in species composition in a given area
Communities and Ecosystems change over time: Ecological Succession
The types and numbers of species in biological communities and ecosystems change in response to environmental conditions such as fires, volcanic eruptions, climate change, and the clearing of forests to plant crops
Population
a group of interbreeding individuals of the same species
4 Variables of population changes
births, deaths, immigration, and emigration (BDIE) Babies Don't Internalize Emotion.
Top-down population regulation
predation
Two main types of ecological succession
primary and secondary
Living systems are sustained through constant change
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Primary and Secondary succession are important natural services that tend to increase biodiversity, and thus the sustainability of communities and ecosystems, by increases species richness and interactions among species.
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A number of physical or chemical factors can help determine the number of organisms in a population. Sometimes one or more factors, known as limiting factors, are more important than other factors in regulating population growth. This ecological principle is called the limiting factor principle: Too much or too little of any physical or chemical factor can limit or prevent growth of a population, even if all other factors are at or near the optimal range of tolerance
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A population with few, if any, limitations on its resource supplies can grow exponentially at a fixed rate such as 1% or 2% per year
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As part of the earth's natural capital, both types of succession are examples of natural ecological resoration.
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Certain interactions among species affect their use of resources and their population size
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Changes in environmental conditions cause communities and ecosystems to gradually alter their species composition and population sizes (ecological succession)
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Changes in the population sizes of keystone species can alter the species composition and biodiversity of an ecosystem
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Density dependent factors tend to regulate a population, keeping it at a fairly constant size, often near the carrying capacity of its environment
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Each population in an ecosystem has a range of tolerance to variations in its physical and chemical environment. Individuals within a population may also have slightly different tolerance ranges for temperature or other physical or chemical factors because of small differences in their genetic makeup, health, and age
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Important limiting physical factors for populations in aquatic life zones, or water-filled areas that support life, include, temperature, sunlight, nutrient availability, and the low levels of oxygen gas in the water (Dissolved oxygen content). Another limiting factor in aquatic life zones is salinity: the amounts of various inorganic minerals or salts dissolved in a given volume of water
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In such cases, the population suffers a sharp decline called dieback/population crash, unless the excess individuals can switch to new resources or move to an area that has more resources. The carrying capacity of any given area is not fixed. In some areas, it can increase/decrease seasonally and from year to year because of variations in weather, such as a drought that causes decreases in available vegetation. Other factors include the presence or absence of predators and an abundance or scarcity of competitors
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Many of these large mammals, especially those with long times between generations and with low reproductive rates like elephants, are vulnerable to extinction
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On land, precipitation often is the limiting factor. Lack of water in a desert limits plant growth. Temp can also be a limiting factor..and soil nutrients
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Some factors that limit population growth have a greater effect as a population's density increases. Examples of such density-dependent population controls include paratism, infectious disease, and competition for resources.
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Some populations use up their resource supplies and temporarily overshoot/exceed, the carrying capacity of their environment. This occurs because of a reproductive time lag: the period needed for the birth rate to fall and for the death rate to rise in response to resource overconsumption
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Species have different reproductive patterns to help ensure their long-term survival..ex: some have many offspring and give them no protection, etc.
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Succession does not follow a predictable path. Succession proceeds in an orderly sequence along an expected path until a certain stable type of climax community occupies an area. Such a community is dominated by a few long-lived plant species and is in balance with its environment. This equilibrium model of succession is what ecologists once meant when they talked about the balance of nature
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There are always limits to population growth in nature
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Under some circumstances, population density affects population size
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When a population exceeds its carrying capacity, it can crash. Some species do not have smooth transitions from exponential growth to logistic growth
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No population can grow indefinitely: J-Curves and S-Curves
No population can grow indefinitely because of limitations on resources and competition with populations of other species for those resources
inertia/persistence
ability of a living system such as a grassland or a forest to survive moderate disturbances
resilience
ability of a living system to be restored through secondary succession after a more severe disturbance..toughness
Environmental resistance determines a area's carrying capacity..
carrying capacity: the maximum population of a give species that a particular habitat can sustain indefinitely. The growth of a population decreases as its size nears the carrying capacity of its environment because resources such as food, water, and space begin to dwindle
Secondary succession
more common type; a series of communities or ecosystems with different species develop in places containing soil or bottom sediment; begins in an area where an ecosystem has been disturbed, removed, or destroyed, but some soil or bottom sediment remains. Candidates for secondary succession include abandoned farmland, burned or cut forests, heavily polluted streams, and land that has been flooded. Because some soil or sediment is present, new vegetation can begin to germinate, usually within a few weeks. It begins with seeds already in the soil and seeds imported by wind or in the droppings of birds and other animals
