Ecology - Biology 111 Principles of Biology Lecture...

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Biology 111, Principles of Biology Lecture Outlines ECOLOGY: the study of the interactions between organisms and their environment The environment includes both biotic (living) and abiotic (non-living) components The biotic components include all other living organisms with which a particular organism interacts: plants, predators, prey, pathogens, etc. The abiotic components include, temperature, climate, nutrients, soil, water, etc. Organisms are affected by their environment AND they also have a direct impact on the environment. Organisms consume nutrients and put out wastes. Consider the impact/effects of ABIOTIC factors: Temperature Climate Water Wind POPULATION ECOLOGY: Populations can be described in terms of several characteristics: Density: no. of individuals/unit area (or volume) Range: geographic area inhabited by a population Dispersion: distribution pattern of individuals with respect to one another (see Figure 35.2). Three basic patterns: 1. Clumped (aggregated): positive interactions or unequal distribution of nutrients/resources (see Figure 52.3a): 2. Uniform: negative interactions/competition (see Figure 52.3b): 3. Random: absence of important interactions (see Figure 52.3c): Population Growth Rate: Recall that one of the underlying principles on which the theory of evolution is based is that organisms have an unlimited biotic potential This unrestricted growth of a population is described by EXPONENTIAL GROWTH (see Figure 52.9): Note that as the number of individuals increases, the number of individuals added to the population each generation increases dramatically
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The bacterium E. coli can reproduce every 20 minutes under ideal conditions. If a population was started with a single cell and allowed to reproduce exponentially for only 36 hours, the number of cells produced would be sufficient to cover the earth in a layer of bacterial cells 12 inches deep Exponential growth can only occur under ideal conditions with unlimited resources (never exist indefinitely) Most real populations display LOGISTIC GROWTH (see Figure 52.12): Note that when the population is small, it approximates exponential growth As the population increases in size, the growth rate decreases This decrease is due to "population-limiting factors", or "environmental resistance" Note that the size of the population eventually reaches a "steady-state", which is the carrying capacity of the environment CARRYING CAPACITY is the maximum stable population size that a particular environment can support Many biotic factors contribute to logistic growth patterns: Competition for food (see Figure 52.15b): Competition for space or territory Decreased health or survival due to overcrowding Abiotic factors, such as climate, may also influence population size and growth rates: Catastrophic declines in sparrow populations are caused by particularly harsh winters The human population has been growing exponentially for centuries (see
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Ecology - Biology 111 Principles of Biology Lecture...

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