Bio.2.2 Understand the impact of human activities on the environment. Populations Essential Standards Bio.2.1 Analyze the interdependence of living organisms within their environments. Bio.2.2 Understand the impact of human activities on the environment.

Properties of Populations Population – group of organisms of same species that live in same place at same time Characterized: Size – number of individuals a population has; estimate size Density – measures how crowded a population is (# individuals per volume) Dispersion – distribution of individuals within population (clumped, even, or random

Population Dynamics All populations are dynamic – change in size and composition over time Measure of population: Birth rate – number of births in period of time Death rate – number of deaths in period of time Life expectancy – how long individual is expected to live

Population Dynamics Age Structure – distribution of individuals of different ages in a population

Population Dynamics Survivorship Curves – patterns in mortality at different ages Type I Curve – chance of death is small early in life but increases later in life Type II Curve – chance of death is constant Type III Curve – chance of death is large in early life but decreases later in life

Population Growth Rate Growth rate = Birth rate – Death rate Change in population size depends on: Birth and death rates Immigration – movement of individual into population Emigration – movement of individuals out of population

Population Exponential Model Exponential Model – rapid increase in a population Birth rates and death rates would remain constant Exponential growth – represented by J-shape curve No limiting factors present! Limiting Factor – factor that limits growth of a population (ex. Competition, resources, etc.)

Population Logistic Model Logistic Model – builds on exponential model but includes limiting factors Logistic Curve – represented by S-shape curve Carrying Capacity – number of species the environment can support over time

Population Regulation Two kinds of population size-limiting factors Density-independent factors – affects all population the same regardless of size (ex. natural disasters ) Density-dependent factors – limit a population according to population size (ex. Competition, predators, disease)

Human population Growth Hunter-gatherer Lifestyle 10,000 – 12,000 years ago Steady population size Agricultural revolution – 10,000 years ago Slight increase in population Industrial revolution ~1840 Exponential growth