Population Biology

Density and Distribution 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 Age Structure 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

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 Would you take the money? Exponential Growth Under ideal conditions with UNLIMITED resources, a population can and will grow exponentially. Exponential growth is when a population increases exponentially Xn (often doubling)

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)

* Population will hover around the CC