1 / 23

HOW POPULATIONS CHANGE

HOW POPULATIONS CHANGE. Chapter 8 Section 1 . a population is…. all the members of a species living in the same place at the same time . 3 Properties of populations…. SIZE – number of individuals in the population H ow many?

callum
Télécharger la présentation

HOW POPULATIONS CHANGE

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. HOW POPULATIONS CHANGE Chapter 8 Section 1

  2. a population is… all the members of a species living in the same place at the same time

  3. 3 Properties of populations… SIZE – number of individuals in the population How many? DENSITY – number of individuals per area or volume How tightly packed? DISPERSION – the distribution or arrangement of a population within a given space • can be dispersed evenly (uniformly), clumped, random

  4. What factors affect the size of a population? • Births, Deaths, Immigration and Emigration • Immigration - when individuals move into a population • Emigration- when individuals leave a population

  5. Emigration after the Civil War Confederate Colonies of Brazil: The Confederados • at the end of the Civil War (1860's) some Confederates left the US (emigrated) to South America • numbered in the thousands • settled primarily in Brazil – coastal areas • some returned to their homes in the United States, but many more settled permanently in Brazil and their descendants are living there today

  6. How does a population change? • Populations grow when… there are more births than deaths or when individuals move into the population. • Populations decline when… there are more deaths than births or when individuals leave the population .

  7. Population Growth is… a change in the size of a population over time GROWTH RATE = birth rate – death rate Growth rates can be… positive, negative or zero • positive growth – more births than deaths • negative growth – fewer births than deaths • zero growth – number of births = number of deaths

  8. Growth Rate

  9. Reproductive Potential The maximum number of offspring that each member of a population can produce • Some species have higher reproductive potentials than others • Insects have a large reproductive potential as compared to humans

  10. Reproductive Strategies “R” strategists – overcome massive loss of offspring by producing many offspring – in hopes that some will survive • Example – insects “K” strategists – have fewer offspring and longer generation times • Example - humans

  11. R strategist (many offspring) or K strategist (few offspring)

  12. 2 Types of population growth models … exponential growth and logistic growth

  13. Exponential Growth • Populations sometimes undergo exponential growth which means that the population grows faster and faster • “J” shaped graph • Exponential growth occurs in nature only when there is plenty of food and space and little or no competition or predators

  14. Exponential Growth of Human Population

  15. Logistical growth • Populations sometimes undergo logistical growth which means the growth rate decreases with increasing number of individuals until it becomes zero when the population reaches a maximum • “S” shaped graph

  16. Logistical growth

  17. Linear Growth • means a population grows by a fixed amount each generation • a steady increase in a population • this type of growth is not characteristics of most populations

  18. What limits the growth of a population? Carrying Capacity – the maximum population size that an environment (or ecosystem) can sustain • Populations cannot grow indefinitely • A population may increase beyond its carrying capacity but this cannot be maintained • Because ecosystems change, the carrying capacity is difficult to predict or calculate exactly

  19. What else limits a population? • RESOURCES- water, sunlight, minerals,… • The most severely limited resources will determine the carrying capacity of an environment! • COMPETITION - for food, shelter (habitat) and mates • PREDATORS

  20. 2 types of Limiting Factors in Ecosystems Density Dependent Factors Resources that decrease as a population increases Density Independent Factors Environmental factors that affect all populations equally

  21. Density Dependent Factor(s)– Resources that decrease as a population increases • regulate a population when individuals are densely packed (crowded) together Examples – limited resources, predation, disease, food, water, shelter, space,….

  22. Density Independent Factor(s) – Environmental factors that affect all populations equally • regulate a population regardless of the population’s density – this type of regulation affects all members of a population Examples – severe weather, current, natural disasters, climate, temperature, precipitation, salinity,…

More Related