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Chapter 16

chapter 16 bio 1225 notes.docx

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Biology 1225
Michael Butler

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Chapter 16 Population Ecology *16.4 and 16.5 are excluded from online test # 3 **** For Final only need to know what is meant by: - Carrying Capacity - Biotic Potential - Population - * there will be no other questions from this chapter on the final exam 1 16.2 Characteristics of Populations pg. 317 demographics – statistics that describe a population ecology – the study of interactions among organisms and between organisms and their environment (populations) ***Population – A group of organisms of the same species who live in a specific location and breed with one another more often than they breed with members of other populations. Example: The Geese population – In the past nearly all Geese seen in the US were migratory. They nested in Northern Canada – flew to the US for the winter then returned to Canada tomate. 2 Populations can be described by 1. Population Size - number of individuals of a species in a population 2. Population Density – the number of individuals in a certain area such as the number of frogs per acre of rains forest 3. Population Distribution – the location of individuals relative to one another. a. Clumped distribution Look at page 317 – members of a population tend to be closer to one another than would be predicted by chance alone. – A patchy distribution of resources encourages clumping because members of the population tend to gather where there are resources like food available – There are benefits of living together in a social group – Limited dispersal ability also causes clumping – Asexual reproduction can also lead to clusters (clumping) – Example: Canada geese live together where there is Grass and water ***Most populations have a clumped distribution b. Near Uniform Distribution - Competition for resources with individuals more evenly spaced than would be expected by chance - Example: Nesting Sea Birds – birds aggressively repels other birds that can get within reach of its beak c. Random distribution - arises when resources are uniformly available and proximity to others neither benefits or harms individuals - Example: Dandilions look at pg. 317 ***Rare in Nature - 4. Population studies typically utilize sampling methods. A sample of the population is studied, then that information is used to infer the size and traits of the population as a whole. Such methods run the risk of sampling error, which can be minimized by using a large sample size. 3 16.3 Population Growth pg. 318 *** Biotic potential – maximum possible population growth under optimal conditions *** carrying capacity – maximum number of individuals of a species that a specific environment can sustain density-dependent limiting factor – factor whose negative effect on growth is felt most in dense populations; for ***example infectious disease or competition for food density-independent limiting factor – factor that limits growth in populations regardless of their density; for ***example a natural disaster or harsh weather logistic model of population growth – model for growth of a population limited by density dependent factors; numbers increase exponentially at first, then the growth rate slows and population size levels off at carrying capacity Per capita growth rate – the number of individuals added during some interval divided by the initial population size 4 - Population growth generally follows certain patterns - When a population grows exponentially, it increases in size by ever larger amounts per unit of time - However all populations face limits to growth, because no environment can indefinitely sustain a continuously increasing number of individuals (organisms run out of food, space, mates or some other limiting factors) - Certain ecological principles govern the growth and sustainability of populations over time, i
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