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Transcript
CHAPTER EIGHT: UNDERSTANDING POPULATIONS Section One: How Populations Change in Size What is a population? Population: all the members of a species living in the same place at the same time Population Density: the number of individuals per unit area or volume Population Dispersion: relative distribution or arrangement of a population’s individuals within a given amount of space Section One: How Populations Change in Size How does a population grow? Growth rate: a change in a population’s size over a given period of time Growth rate= births – deaths When the number of births = number of deaths, the growth rate is 0 Section One: How Population Change in Size How fast can a population grow? Reproductive potential: the maximum number of offspring that each member of a population can produce Exponential growth: populations grow exponentially, or faster and faster Only happens when there is plenty of space and food in nature Section One: How Populations Change in Size What limits population growth? Carrying capacity: the maximum population that an ecosystem can support indefinitely Difficult to predict because ecosystems are always changing Resource Limits Competition within a Population Members of population use the same resources in the same way and compete for that resource Territories may be established Section One: How Populations Change in Size Population Regulation Density dependent Populations are large and there are not enough resources for everyone Density A independent certain amount of individual die regardless of population size Such as weather and natural disasters Section Two: How Species Interact with Each Other An Organism’s Niche Niche: the unique role of a species within a ecosystem Includes their home, environmental factors needed for survival, and all interactions with other animals Section Two: How Species Interact with Each Other Ways Species Interact Competition Predation Parasitism Mutualism Commensalism Symbiosis and Coevolution Section Two: How Species Interact with Each Other Competition When different individuals or populations attempt to use the same limited resource Can occur within and between species When different species compete for the same resource it is called a niche overlap Indirect competition: species compete but do not come in direct contact with one another Niche restriction: each species uses less of the niche than it is capable of using Adaptations reduce competition Section Two: How Species Interact with Each Other Predation When a predator feeds on a prey Some organism have adaptations to avoid or defend against predation Predator-prey populations are usually similar because the predator depends on prey for food Section Two: How Species Interact with Each Other Parasitism When one organism lives in or on another and feeds on it Examples: ticks, tapeworms, fleas, leaches, mistletoe Parasites do not kill their host but often weaken it Section Two: How Species Interact with Each Other Mutualism A close relationship between species in which both receive a benefit from the other Examples: gut bacteria Section Two: How Species Interact with Each Other Commensalism A relationship in which one species benefits while the other is not harmed or helped Example: epiphytes Section Two: How Species Interact with Each Other Symbiosis and Coevolution Symbiosis: a relationship in which two species live in close association Usually describes relationships where atleast one species benefits May lead to coevolution