Presentation is loading. Please wait.

Presentation is loading. Please wait.

Copyright © 2009 Pearson Education, Inc. PowerPoint Lectures for Biology: Concepts & Connections, Sixth Edition Campbell, Reece, Taylor, Simon, and Dickey.

Similar presentations


Presentation on theme: "Copyright © 2009 Pearson Education, Inc. PowerPoint Lectures for Biology: Concepts & Connections, Sixth Edition Campbell, Reece, Taylor, Simon, and Dickey."— Presentation transcript:

1 Copyright © 2009 Pearson Education, Inc. PowerPoint Lectures for Biology: Concepts & Connections, Sixth Edition Campbell, Reece, Taylor, Simon, and Dickey Chapter 36 Population Ecology Lecture by Brian R. Shmaefsky

2 Copyright © 2009 Pearson Education, Inc. POPULATION STRUCTURE AND DYNAMICS

3 Copyright © 2009 Pearson Education, Inc Population ecology is the study of how and why populations change  Population –A group of individuals of a single species that occupy the same general area  Individuals in a population –Rely on the same resources –Are influenced by the same environmental factors –Are likely to interact with one another  Described by the  Number of individuals  Distribution of individuals

4 Copyright © 2009 Pearson Education, Inc.  Population dynamics is the interactions between –Biotic and abiotic factors  It is the cause of variation in population sizes –A population increases through birth and immigration –Death and emigration out of an area decrease the population 36.1 Population ecology is the study of how and why populations change

5 Copyright © 2009 Pearson Education, Inc Density and dispersion patterns are important population variables  Population density is the number of individuals of a species per unit area or volume  Within a population’s geographic range, local densities may vary  The dispersion pattern of a population refers to the way individuals are spaced within their area -Clumped -Uniform -Random

6 Copyright © 2009 Pearson Education, Inc. In a clumped pattern individuals are grouped in patches Possibly due to: - Unequal distribution of resources - Social behavior advantage

7 Copyright © 2009 Pearson Education, Inc. In a uniform pattern individuals are equally spaced in the environment Possibly due to: - Interactions between individuals - Social behavior (territoriality)

8 Copyright © 2009 Pearson Education, Inc. In a random pattern of dispersion, the individuals in a population are spaced in an unpredictable way Possibly due to: -Lack of interactions - Random or even distribution of resources

9 Copyright © 2009 Pearson Education, Inc. Life tables track survivorship over the life span of individuals in a population

10 Percentage of maximum life span Percentage of survivors (log scale) Type III Type II Type I Survivorship curves plot the proportion of individuals alive at each age

11 Copyright © 2009 Pearson Education, Inc Idealized models predict patterns of population growth  Two models used to describe population growth:  Exponential growth model  Logistic growth model

12 Copyright © 2009 Pearson Education, Inc Idealized models predict patterns of population growth  Exponential growth model –The rate of population increases under ideal conditions –Calculated using the equation: G = rN –G is the growth rate of the population –N is the population size –r is the per capita rate of increase Time (months) Population size (N) Rabbits

13 Time (months) Population size (N) Rabbits

14 Bacteria and opportunistic microorganisms follow an Exponential Growth model  Lag phase : recovery from low metabolic state, cells “gear up” their enzymes  Log phase : exponential expansion when nutrients are not limiting and conditions are right  Stationary phase : growth slows due to lower nutrients or oxygen, or buildup of waste products  Death phase : cells die more rapidly with toxic wastes or acidic pH

15 Apr MayJun Jul AugSepOct Nov Dec Number of aphids Exponential growth Sudden decline

16 Copyright © 2009 Pearson Education, Inc.  Logistic growth model –This growth model takes into account limiting factors –Limiting factors are environmental factors that restrict population growth –Formula where K = Carrying Capacity 36.4 Idealized models predict patterns of population growth

17 Time Number of individuals (N) 0 K G = rN (K – N) K 36.4 Graphs depicting exponential and logistic growth models

18 Copyright © 2009 Pearson Education, Inc.  Abiotic factors may reduce population size before other limiting factors become important  Weather, fires, floods  Biotic factors often play major role in limiting population size  Competition, predation, internal regulations, 36.5 Multiple factors may limit population growth

19 Copyright © 2009 Pearson Education, Inc Multiple factors may limit population growth Time (years) Number of females  Most populations fluctuate in numbers (Song sparrow population drops suddenly with severe winter weather)

20 Copyright © 2009 Pearson Education, Inc Some populations have “boom-and-bust” cycles  Some populations fluctuate in density with regularity  Boom-and-bust cycles –Food shortages –Predator-prey interactions  For snowshoe hare, it’s likely a combination of both these Lynx Snowshoe hare Lynx population size (thousands) Hare population size (thousands) Year

21 Copyright © 2009 Pearson Education, Inc EVOLUTION CONNECTION: Evolution shapes life histories  r /K selection –r-selective traits –Small, short-lived organisms (insects, small rodents, weeds) –Where disturbances make new opportunities for rapid growth –Fastest to reproduce has advantage –K-selective traits –Larger, long-lived organisms (bear, elephants, trees) –Nutrient- or density-limited stable climate environments –Highest efficiency in resource competition has advantage

22 Year Birth rate Death rate Rate of increase (r) Birth or death rate per 1,000 population


Download ppt "Copyright © 2009 Pearson Education, Inc. PowerPoint Lectures for Biology: Concepts & Connections, Sixth Edition Campbell, Reece, Taylor, Simon, and Dickey."

Similar presentations


Ads by Google