1 / 21

Population

Population. A group of organisms of the same species living in the same environment over time. Changing Population Size. Recall the four factors that add to or remove from the population:. 1. Natality/Births. 2. Mortality/Deaths. 3. Immigration. 4. Emigration.

galvin
Télécharger la présentation

Population

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. Population A group of organisms of the same species living in the same environment over time.

  2. Changing Population Size Recall the four factors that add to or remove from the population: 1. Natality/Births 2. Mortality/Deaths 3. Immigration 4. Emigration

  3. Human populations remained static until agriculture began to develop. Changes in Populations Then humans were able to supply food to more population and as a result populations grew. Since the industrial revolution populations have continued to grow.

  4. Limits on Populations A population will not grow endlessly. There are six factors that will prevent a population from growing uncontrollably.

  5. Factor #1: Biotic Potential This is the number of babies an organism can produce during its lifetime; it is determined by: 1. Birth potential - the number of babies per birth. 2. Capacity for survival - the number of babies that reach the age of reproduction. 3. Procreation - the number of times the species reproduces each year. 4. Length of reproductive life - the number of years the species can have babies.

  6. Mousy Example: Birth Potential Consider a mousy example: Birth potential - the number of babies per birth. A mouse can have an average of eight babies each time it gives birth. 8 mice

  7. Mousy Example: Capacity for Survival Consider a mousy example: Capacity for survival - the number of babies that reach the age of reproduction. Suppose on the prairie that 50% of mice survive to be old enough to reproduce. 8 x 50% survival = 4 mice

  8. Mousy Example: Procreation Consider a mousy example: Procreation - the number of times the species reproduces each year. In Canada, female field mice can reproduce about 5 times per year. 4 x 5 times/year = 20 mice

  9. Mousy Example: Reproductive Life Consider a mousy example: Length of reproductive life - the number of years the species can have babies. Female mice can have babies at 6 weeks of age, and die at a year, reproducing for only one year. 20 x 1 year = 20 mice

  10. Mousy Example: Summary In our mousy example, the biotic potential of each female will be20 mice. What will this do to the mouse population? Predict the effect on a fox population in the same prairie. Why are we not surrounded by mice and foxes?

  11. Factor #2: Limiting Factors The environment provides factors that prevent populations from reaching their biotic potential. Resources (biotic and abiotic) that are in short supply limit population growth. • food • territory • predators • water • pollution • diseases

  12. Fern Example: Limiting Factors Consider a fern plant that produces 50 000 spores in a single year: Water - dry weather prevents germination and kills exposed plants. Predators - grazing animals will reduce the population.

  13. Factor #3:Carrying Capacity: This is the maximum number of individuals of a species that can be supported indefinitely by an ecosystem. Availability of resources determines the carrying capacity of an ecosystem.

  14. Another Mouse Example:Carrying Capacity Suppose the population of predators is low; the mouse population will… increase. This causes the amount of mouse food to… decrease. The mouse population becomes sickly (mange) and slow; they are easy prey for predators so the mouse population will… decrease. Carrying capacity is restored!

  15. Carrying Capacity:Analogy

  16. Factor #4Limits of Tolerance Law of the Minimum: The nutrient that is least availablelimits growth. e.g. People who lack vitamin C will get scurvy and will die.

  17. Factor #4Limits of Tolerance Law of Tolerance: Organisms are harmed if nutrient or abiotic factors are too low AND too high. e.g. We all know that people can die of thirst, but… there is one recorded case of a woman dying from drinking too much water!

  18. Factor #4Limits of Tolerance

  19. Factor #5Density-Dependent Factors A large population size makes it possible for certain “problems” to occur. Consider the SARS outbreak of 2003. Where did this DISEASE spread? Large populations... Hong Kong, Toronto, etc. Other density-dependent factors that control population size include food supply, water quality, sunlight, disease, and territory.

  20. Factor #6Density-Independent Factors These factors will affect the size of the population, even if the population is small. Consider a tornado. Will the tornado kill a population of mice, even if it is a small population? Other examples include fires and floods.

  21. Assignment: Video Assignment: Population Limits on the Brown Tree Snake: http://www.teachersdomain.org/resources/tdc02/sci/life/eco/bioinvaders/index.html Text Assignment: p. 80 #1, 2a, 3, 4 Modified: Video (top half); handout

More Related