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Factors Affecting Population Change

Factors Affecting Population Change. Exponential Vs. Logistic Growth. Two Strategies for Growth. 1. “r -strategists”: Spawners! Characterized by exponential growth, which results in temporarily large populations, followed by sudden crashes in population size.

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Factors Affecting Population Change

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  1. Factors Affecting Population Change

  2. Exponential Vs. Logistic Growth

  3. Two Strategies for Growth 1. “r-strategists”: Spawners! Characterized by exponential growth, which results in temporarily large populations, followed by sudden crashes in population size. Ex. Insects, bacteria, some plants • live in unpredictable and rapidly changing environments • Reproduce quickly when conditions are favorable • External Fertilization • Many offspring: small, mature rapidly, no parental care

  4. Two Strategies for Growth 2. “K-strategists”: Brooders! Characterized by a high degree of specialization. Ex. Trees, whales, tigers, etc. • Live in stable and predictable environments • Can compete effectively • Reproduce late in life • Internal Fertilization • Few offspring: large, mature slowly, often much parental care

  5. Density Dependent Factors • Factors that influence population regulation, having greater impact as population density increases or decreases • Struggle for survival includes factors like competition, predation, disease, and other biological effects

  6. Density Dependent Factors • Intraspecific Competition – Ecological interaction where individuals of the same species/population compete for resources in their habitat.

  7. Density Dependent Factors • Predation - Consumption of prey by carnivores • -Regulation can occur due to preferred species of prey

  8. Density Dependent Factors • Disease – Pathogens able to pass from host to host in overcrowded populations with greater ease

  9. Density Dependent Factors • Allee effect – Occurs when population cannot survive or fails to reproduce enough to offset mortality once the population density is too low; such populations usually do not survive. Eg. The extinct passenger pigeon.

  10. Density Dependent Factors • Minimum viable population size – Smallest number of individual needed for a population to continue for a given period of time • Small population size can result in inbreeding and loss of genetic variation

  11. Density Independent Factors • Factors influencing population regulation regardless of population density • Human intervention - Pesticides • Environment - reproductive success based on temperatures, natural disasters etc

  12. Limiting Factors • Any essential resource that is in short supply or unavailable. These factors determine how much the individual or population can reproduce. • Eg. light, space, water, nutrients

  13. Homework! • Page 675 1, 2 & 5 • Read 676-687

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