Presentation on theme: "Population Biology. How Study Populations? Geographic Range Density and Distribution Growth rate Age structure."— Presentation transcript:
How Study Populations? Geographic Range Density and Distribution Growth rate Age structure
Geographic Range The area inhabited by a population Can vary greatly depending on the species (bacteria on a rotting pumpkin vs. cod in the western Atlantic ocean from Greenland to North Carolina
Density and Distribution Population density refers to the number of individuals per unit area Distribution refers to how individuals in a population are spaced out across the range of the population: random, uniform or clumps. Random Uniform Clumped
Growth Rate Determines whether the size of the population increases, decreases, or stays the same. can be positive, negative or zero Age Structure The number of males and females of each age a population contains Important because most animals do not reproduce until a certain age
Population Growth Factors that effect population growth 1. Birth Rate and Death Rate In a given period of time: Birth rate > death rate population increases Birth rate = death rate population stays the same Birth rate < death rate population decreases 2. Emigration and Immigration Immigration – movement of individuals into an area occupied by an existing populations Emigration – movement of individuals out of an area
Exponential vs. Logistic Growth Exponential Growth Under ideal conditions with UNLIMITED resources, a population can and will grow exponentially. Exponential growth is when a population increases exponentially X n (often doubling) Would you take the money?
Logistic Growth Resources are NOT unlimited so a population can not grow exponentially forever Logistic growth occurs when a populations’ growth slows and then stops, following a period of exponential growth Carrying Capacity The maximum number of individuals of a particular species in a particular environment can support (without degrading it for future generations)