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Succession

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Succession Ecological  succession  is a series of progressive changes in the species that make up a community over time. Ecologists usually identify two types of succession, which differ in their starting points: In  primary succession , newly exposed or newly formed rock is colonized by living things for the first time. In  secondary succession , an area that was previously occupied by living things is disturbed, then re-colonized following the disturbance. Succession often involves a progression from communities with lower species diversity—which may be less stable—to communities with higher species diversity—which may be more stable ^1 ​ 1 ​ ​ start superscript, 1, end superscript —though this is not a universal rule. Primary succession and pioneer species Primary succession  occurs when new land is formed or bare rock is exposed, providing a habitat that can be colonized for the first time. For example, primary succession may take place
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Keystone and Foundation Species

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Types of Keystone Species There are many types of keystone species, and some of them have been thoroughly studied. Predators are typically defined as keystone species, because it takes only a few to regulate populations of other species in lower trophic levels. Many species that create or modify habitats, called ecosystem engineers, are also keystone species. Ecosystem Engineer Species that create or modify habitats, such as beavers ( Castor canadensis), can strongly affect ecosystem nutrient cycling. Shifts in available nutrients can directly and indirectly affect animal or plant species that use the same habitat. Examples of Keystone Species  Even prior to Paine’s seminal work and terminology, biologists had studied and defi ned many species as unique and necessary components of a given ecosystem, despite their rarity or low numbers. Many species have been widely studied in their role as keystone species. 1. Sea Stars This is the quintessential example of a keystone species
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Community Ecology

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What Is Community Ecology? An ecological community is defined as a group of actually or potentially interacting species living in the same place. A community is bound together by the network of influences that species have on one another. Inherent in this view is the notion that whatever affects one species also affects many others -- the "balance of nature". We build an understanding of communities by examining the two-way, and then the multi-way, interactions involving pairs of species or many species.    A community is made up of populations of different species, or animals, plants, fungi, and bacteria, living in the same area A. Predation The most obvious form of species interaction is when one species eats another,  predation  being the technical term for this unfortunate fate. The  predator  is the organism that does the eating, the  prey  the one that gets eaten. A simple way to depict who eats what is by drawing a  food chain , with the arrows pointing in t
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Exponential & logistic growth

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Exponential & logistic growth Modeling population growth rates To understand the different models that are used to represent population dynamics, let's start by looking at a general equation for the population growth rate (change in number of individuals in a population over time): In this equation, dN/dT is the growth rate of the population a given instant, N is population size, T is time, and r is the per capita rate of increase –that is, how quickly the population grows per individual already in the population. If we assume no movement of individuals into or out of the population, r is just a function of birth and death rates. You can learn more about the meaning and derivation of the equation here: The equation above is very general, and we can make more specific forms of it to describe two different kinds of growth models: exponential and logistic. When the per capita rate of increase (r) takes the same positive value regardless of the population siz
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