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Population
Ch19 - Populations & Ch 20 - Sect 2: Patterns in Communities
| Term | Definition |
|---|---|
| population | a group of organisms that belong to the same species and live in a particular place at the same time |
| population size | the number of individuals that the population contains |
| population density | measures how crowded a population is |
| dispersion | the spatial distribution of individuals within the population |
| clumped distribution | individuals are clustered together |
| uniform distribution | individuals are separated by a fairly consistent distance |
| random distribution | each individual's location is independent of the locations of other individuals in the population |
| birth rate | the number of births occurring in a period of time |
| death rate / mortality rate | the number of deaths in a period time |
| life expectancy | how long on average an individual is expected to live |
| age structure | the distribution of individuals among different ages in a population |
| survivorship curves | show the probability that members of a population will survive to a certain age |
| Type I survivorship curve | the likelihood of dying is small until late in life |
| Type II survivorship curve | the probability of dying does not change throughout life (linear) |
| Type III survivorship curve | the probability of dying young is very high |
| demographers | scientists who study population dynamics |
| population dynamics | changing in size and composition over time |
| growth rate | the amount by which a population's size changes in a given time (birth rate - death rate) |
| immigration | the movement of individuals into a population |
| emigration | the movement of individuals out of a population |
| per capita | meaning per individual |
| exponential growth | a pattern of increase in number due to a steady growth rate |
| exponential model | the observation that populations can grow exponentially |
| limiting factor | any factor that restrains the growth of a population |
| logistic model | population growth that builds from the exponential model but accounts for the influence of limiting factors |
| carrying capacity | the number of individuals the environment can support over a long period of time |
| logistic growth | exponential growth then decrease to a halt when the population reaches the carrying capacity (birth rate = death rate) and growth stops |
| density-independent factors | reduce the population by the same proportion regardless of the population's size (weather, floods, fires) |
| density-dependent factors | resource limitations triggered by increasing population density (food shortages, shortage of nesting sites) |
| inbreeding | mating with relative |
| hunter-gatherer lifestyle | obtaining food by hunting animals and gathering roots, berries, nuts, etc. |
| agricultural revolution | humans began to domesticate animals and cultivate certain plants for food |
| developed countries | the world's modern, industrialized countries, better educated, population growth rate low |
| developing countries | 80% of world's population - poorer, less educated, population growth rate high |
| demographic transition | the general pattern of demographic change from high birth and death rates to low birth and death rates, as observed in the history of more-developed countries |
| species-richness | the number of species in the community - simple count of the species in the community |
| species evenness | relative abundance of each species - how common each species is in the community |
| species-area effect | larger areas contain more species than smaller areas |
| disturbances | events that change communities, remove or destroy organisms from communities, or alter resource availability |
| stability | the tendency of a community to maintain relatively constant conditions |
| ecological succession | the gradual, sequential regrowth of a community of species in an area |
| primary succession | the development of a community in an area that has not supported life previously |
| secondary succession | the sequential replacement of species that follows disruption of an existing community - soil is already present |
| pioneer species | the species of organisms that predominate early in succession |
| lichens | a simple slow-growing plant that typically forms a low crusty, leaflike, or branching growth on rocks, walls, and trees |
| climax community | a stable ecosystem in its final stage of ecological succession |
Created by:
droesener
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