Population ecology and human impact


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  • Although several species may share a habitat they each have their own niche. A niche is a very narrow range where a species fits within a habitat.
  • Although several species may share a habitat they each have their own niche. A niche is a very narrow range where a species fits within a habitat.
  • Carrying capacity can change, as environment changes. Food supply, predators: number and kinds, weather, seasons.
    Rabbits in australia ate all the food. Ditto for deer on Angel Island.
  • Although several species may share a habitat they each have their own niche. A niche is a very narrow range where a species fits within a habitat.
  • Population ecology and human impact

    1. 1. Population Ecology and Human Impact By : Mmatsela Kobe
    2. 2. - Is the study of interactions among organisms and their environment
    3. 3. Population Dynamics Population: All the individuals of a species that live together in an area Demography: The statistical study of populations, allows predictions to be made about how a population will change
    4. 4. Population Dynamics Key Features of Populations
    5. 5. Population size … is the number of individuals present at a given time. The passenger pigeon was once North America’s most numerous bird, but it is now extinct.
    6. 6. Population density … is the number of individuals per unit area. In the 19th century, the flocks of passenger pigeons showed high population density.
    7. 7. Population distribution …is the spatial arrangement of individuals.    Random- No patterns Uniform- Interactions among individuals Clumped- Often correlates with resources
    8. 8. Population Distribution
    9. 9. Changes in a Population • factors determine population changes 1.births 2.deaths 3.migration • immigration • emigration
    10. 10. How Do You Affect Density?  Immigration: movement of individuals into a population  Emigration: movement of individuals out of a population  Density-dependent factors: Biotic factors in the environment that have an increasing effect as population size increases (disease, competition, parasites)  Density-independent factors: Abiotic factors in the environment that affect populations regardless of their density (temperature, weather)
    11. 11. How Are Populations Measured? • Population density = number of individuals in a given area or volume • Count all the individuals in a population • Estimate by sampling • Mark-Recapture Method
    12. 12. Formula for capture-recapture method Marked animals in 2nd sample Total caught in 2nd sample = Marked animals in 1st sample Total population size
    13. 13. How Do Populations Grow? Idealized models describe two kinds of population growth: 1. Exponential Growth has no upper limit and populations grow very quickly 2. Logistic Growth has a limit and growth approaches this limit in a sigmoidal fashion Logistic growth is more realistic in real life, but exponential growth is a better model for bacterial cultures, etc. that have unlimited resources and space
    14. 14. Exponential Growth • Also known as a J-curve • Growth is a fixed percentage of the whole (e.g., 10% per day or year) • Population is growing at its full biotic potential
    15. 15. Exponential Growth Curve • A J-shaped growth curve, described by the equation G = rN, is typical of exponential growth – G = the population growth rate – r = the intrinsic rate of increase, or growth rate in an ideal environment (births-deaths) – N = the population size
    16. 16. Logistic Growth • Also known as S-curve • Growth slows as the population approaches Carrying Capacity • Populations stabilize at carrying capacity
    17. 17. Logistic Growth Curve – K = carrying capacity – The term (K - N)/K accounts for the leveling off of the curve
    18. 18. Carrying Capacity • Carrying Capacity (k): • The maximum population size that can be supported by the available resources • There can only be as many organisms as the environmental resources can support
    19. 19. Survivorship • three types of survivorship curves • late loss (Type I) • have a high survival rate of the young, live out most of their expected life span and die in old age. • constant loss (Type II) • relatively constant death rate throughout their life span - death could be due to hunting or diseases. • early loss (Type III) • have many young, most of which die very early in their life.
    20. 20. Factors Limiting Growth Rate • Declining birth rate or increasing death rate are caused by several factors including: • Limited food supply • The buildup of toxic wastes • Increased disease • Predation
    21. 21. Reproductive Strategies r Selection (many offspring)       Short life span Small body size Reproduce quickly Have many young Little parental care Ex: cockroaches, weeds, bacteria
    22. 22. Reproductive Strategies  K Selection (few offspring)  Long life span  Large body size  Reproduce slowly  Have few young  Provides parental care  Ex: humans, elephants
    23. 23. Age Distribution • Distribution of males and females in each age group of a population • Used to predict future population growth
    24. 24. Human Population Growth • J curve growth • Why doesn’t environmental resistance take effect? • Altering their environment • Technological advances • The cultural revolution • The agricultural revolution • The industrial-medical revolution
    25. 25. Communities in Transition • Ecological succession: process by which organisms occupy a site and gradually change environmental conditions by creating soil, shelter, and increasing humidity. • Primary succession: community begins to develop on a site previously unoccupied by living organisms. • Secondary succession: existing community is disrupted and a new one develops.
    26. 26. The Human population •World population increases every year. •Increased population=increased needs. •Uncontrolled population growth=problems in the avaibility of resources needed by people. •Increase environmental damage. •Therefore, some effort to control the population growth should be put into action in order to minimize the problems that may occur.
    27. 27. The Human Population Doubled three times in the last three centuries About 6,1 billion and may reach 9.3 billion by the year 2050 Improved health and technology have lowered death rates
    28. 28. Human Impacts on Ecosystems Habitat degradation and fragmentation Ecosystem simplification Genetic resistance Predator elimination Introduction of non-native species Overharvesting renewable resources Interference with ecological systems
    29. 29. References • This presentation is a mash up of 5 presentations by the following:  Choudhury, S.M.(2009). Population Ecology. http://www.slideshare.net/Shohail/population-ecology-1968004?qid=d37f2617-c106-4648-847b-08e9a5820e9b&v=default&b=&from_s (Accessed on 06/03/2014).  Pointer, K. (2011).Population ecology : Populations. http://www.slideshare.net/coachpointer/population-ecology-9976847?qid=d37f2617-c106-4648-847b-08e9a5820e9b&v=default&b=&fr (Accessed on 06/03/2014)  Tnewberry. (2008). Population ecology. http://www.slideshare.net/tnewberry/population-ecology-514438?qid=d37f2617c106-4648-847b-08e9a5820e9b&v=default&b=&from_search=3.( Accessed on 06/03/2014)  Bombon, R. (2008). Population ecology. http://www.slideshare.net/gobuktaragang/population-ecology?qid=2c884cb11ff2-41dd-90c8-f87a735d8bb9&v=qf1&b=&from_search=28. (Accessed on 05/03/2014).  Kesturi, A. (2013). Human population and its impact. http://www.slideshare.net/alfikesturi/7-7-human-population-and-itsimpacts?qid=f2191318-2cf8-4777-bac7-6e29c191e56b&v=qf1&b=&from_search=1. (Accessed on 05/03/2014)