Chapter 36 - Population Dynamics

Chapter 36 - Population Dynamics - Population Dynamics...

Info iconThis preview shows page 1. Sign up to view the full content.

View Full Document Right Arrow Icon
This is the end of the preview. Sign up to access the rest of the document.

Unformatted text preview: Population Dynamics Population Chapter 36 Population Population A group of individuals of the same group species occupying a given area species Characteristics of a Population Characteristics Size and Density Size Distribution Age structure Growth Survivorship Density Number of individuals per unit area or Number volume Density information is more useful if Density combined with distribution (spacing) data Population Distribution Population Pattern in which individuals are spaced Pattern within a specified area of habitat within clumped uniform random Clumped Distribution Clumped Uniform Distribution Uniform Fig. 39-2c, p.686 Random Distribution Random Life Tables Life Tracks age-specific patterns Tracks Population is divided into age groups Birth rates and mortality risks are Birth calculated for each age category calculated Table 39.2 Life Table for the United States Human Population in 2001 Number at Start of Interval 100,000 99,316 99,184 99,108 99,012 98,682 98,214 97,743 97,189 96,388 95,234 93,552 91,179 87,705 82,519 75,122 65,104 51,820 35,943 19,796 7,890 2,045 Age Interval 0–1 1–5 5–10 10–15 15–20 20–25 25–30 30–35 35–40 40–45 45–50 50–55 55–60 60–65 65–70 70–75 75–80 80–85 85–90 90–95 95–100 100+ Number Dying During Age Interval 684 132 76 96 330 468 471 554 801 1,154 1,682 2,373 3,474 5,186 7,397 10,018 13,284 15,877 16,147 11,906 5,845 2,045 Life Expectancy at Start of Interval 77.2 76.7 72.8 67.9 62.9 58.1 53.4 48.6 43.9 39.2 34.7 30.3 26.0 21.9 18.1 14.6 11.5 8.8 6.5 4.8 3.6 2.7 Reported Live Births 7,315 525,493 1,022,106 1,060,391 951,219 453,927 95,788 5,244 263 Table 39-2, p.692 Survivorship Survivorship The three types of survivorship curves – Reflect species’ differences in reproduction and Reflect mortality mortality Percentage of survivors (log scale) 100 I 10 II 1 III 0.1 0 50 Percentage of maximum life span Figure 36.3 10 0 Type I Type High survivorship for most age groups High except older individuals – Ex. humans, large mammals, Ex. – produce few offspring but provide produce extensive parental care extensive Type II Type Constant survivorship rate at all ages – Ex. lizards, invertebrates and rodents Ex. Fig. 39-10b, p.693 Type III Type Low survivorship for the young but Low individuals that do make it live longer – Ex. many fish and invertebrates Ex. – produce many young produce – give no parental care give Fig. 39-10c, p.693 Changes in Population Size (Growth) (Growth) Births + Immigration add individuals Deaths + Emigration subtract individuals Zero Population Growth Zero Interval in which number of births is Interval balanced by number of deaths balanced Assume no change as a result of Assume migration migration Population size remains stable Exponential Growth Exponential Is the accelerating increase that occurs Is when growth is unlimited when Exponential Growth in Field Mice in Time Number of Cells 70 0 minutes 20 40 60 80 100 120 1 2 4 8 16 32 64 512 4,096 16,777,216 (= 2 hours) 3 hours 4 hours 8 hours 0 0 12 hours 20 40 60 80 100 120 140 10 68,719,476,736 = 20 = 21 = 22 = 23 = 25 = 26 = 29 = 212 = 224 = 236 Number of bacterial cells (N) = 24 50 60 40 30 20 G=rN Time (min) Biotic Potential Biotic Maximum rate of increase per individual Maximum under ideal conditions under In nature, biotic potential is rarely reached Limiting Factors Limiting Environmental factors that restrict Environmental population growth population Breeding male fur seals (thousands) 10 8 6 4 2 0 1915 1925 1935 Year 1945 Figure 36.4B Fig. 39-7a, p.690 Carrying Capacity (K) Carrying Maximum number of individuals that can be Maximum sustained in a particular habitat sustained Logistic growth occurs when population size is limited by carrying capacity is Logistic Growth Logistic Occurs when population size is limited by Occurs carrying capacity carrying Density-Dependent Controls Density-Dependent Depend on the number of individuals in Depend the population Increase a population’s death rate and Increase decrease the birth rate decrease Ex. Disease, competition, parasites, Ex. toxic effects of waste products toxic Density-Independent Controls Density-Independent Do not depend on the number of individuals Do in the population Natural disasters or climate changes Natural Affect large and small populations alike Evolution Shapes Life History Traits Evolution Traits that affect an organisms timing of Traits reproduction and survivorship reproduction Shaped by adaptive evolution r-selection Individuals are small, mature early, and or Individuals produce many off spring at a time produce k-selection Individuals are large and long-lived, Individuals Mature and reproduce at a later age Produce few and well cared for Produce offspring offspring Human Population Growth Population now exceeds 6 billion Rates of increase vary among countries Population continues to increase Population exponentially exponentially Population Growth Curve Population Estimated size by 10,000 years ago By 1804 By 1927 By 1960 By 1974 By 1987 By 1999 Projected for 2050 5 million 1 billion 2 billion 3 billion 4 billion 5 billion 6 billion 8.9 billion What is the earths Carrying Capacity What Ecological footprint – Amount of land needed to support human Amount demands on Earth’s resources demands World is already in ecological deficit – Overpopulation, over consumption – Possible limiting factors: food, space Possible Age structure of a Population Age Population of individual in different age groups Affects populations future growth Indicates social conditions Varies in developing and developing countries – Infant mortality – Life expectancy Age Structure Diagrams Age Show age distribution of a population Rapid growth Afghanistan Age 85+ 80–84 75–79 70–74 65–69 60–64 55–59 50–54 45–49 40–44 35–39 30–34 25–29 20–24 15–19 10–14 5–9 0–4 8 6 Male Female Slow growth Decrease Italy Male Female United States Male Female Primary reproductive ages 4 2 0 2 4 6 8 6 4 2 0 2 4 6 6 4 2 0 2 4 6 ure 36.10B Percent of population Percent of population Percent of population ...
View Full Document

This note was uploaded on 02/10/2011 for the course BIO 1100 taught by Professor Woods during the Spring '07 term at Troy.

Ask a homework question - tutors are online