1 / 28

Populations

Populations. Chapter 19. Understanding Populations. Section 19.1. Definition:. A group of organisms of the same species living in the same place at one time. Thomas Malthus (1766-1834). Essay on the Principal of Population

zanta
Download Presentation

Populations

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. Populations Chapter 19

  2. Understanding Populations Section 19.1

  3. Definition: • A group of organisms of the same species living in the same place at one time

  4. Thomas Malthus (1766-1834) • Essay on the Principal of Population • In nature, plants and animals produce far more offspring than can survive • Man, too, is capable of overproducing if left unchecked • Famine and poverty are natural outcomes of overpopulation

  5. 3 Characteristics: 1. Size 2. Density 3. Dispersion

  6. Population Size • # of individuals in a given area • Difficult to measure • Estimates often taken

  7. Population Density • How crowded a population is • # of individuals per unit area • E.g.: 30 people/classroom

  8. Population Dispersion • Spatial distribution of individuals 1. Clumped 2. Even 3. Random

  9. Population Dynamics • Populations change over time due to: • Birth rates • Death (Mortality) rates • Life expectancy rates • Age Structure • Patterns of Mortality

  10. Age Structure • Distribution of individuals among different ages in a population

  11. Survivorship Curve Type I Type II % Survival Type III Age

  12. Patterns of Mortality • Survivorship Curves • Type I – death at old age • Type II – death at any age • Type III – death at young age

  13. Measuring Populations Section 19.2

  14. Population Growth Rate • # by which a population’s size changes over time • Depends upon: • 1. birth rate • 2. death rate • 3. emigration • 4. immigration

  15. Calculations • ADDS to population = birth & immigration • SUBTRACTS from population = death & emigration • ASSUME immigration = emigration • THEREFORE: birth rate – death rate = growth rate

  16. 2 Models of Growth • Exponential Model (J curve) 2. Logistic Model (S curve)

  17. Exponential Model • The larger the population gets, the faster it grows! • Birth & Death rates remain constant • Limitation: only exists under rare conditions • Doesn’t account for limiting factors that occur in nature

  18. Logistic Model • The exponential model accounting for the influence of limiting factors • Limiting Factor: condition that restricts growth of a population • Carrying capacity (K): # of individuals the environment can support of a long period of time • Fluctuates slightly

  19. Carrying Capacity

  20. 2 types of limiting factors • 1.Density-independent factors • Abiotic factors • Reduction of population by same proportion no matter what size it is • Ex) floods or extreme temp.

  21. 2. Density-dependent factors • Biotic factors • The larger the population, the larger the proportion of reduction. • Ex) disease or starvation

  22. Human Population Growth, 19.3

  23. History Lesson • Hunter-gatherer lifestyle: slow human growth because of high mortality rate • Agricultural revolution: human population growth because of an increase in the food supply • Industrial revolution: rapid human population growth because of decline in death rates

  24. Today’s Growth • Developed Countries: 20% of world’s population, low growth rates • Ex) USA, Japan, Germany, France, etc. • Developing Countries: 80% of world’s population, high growth rate • Ex) Central America, South America, Asia, Africa

More Related