Population Characteristics Populations are groups of the same species in the same area Characteristics of populations include density, distribution, and growth rate Copyright © McGraw-Hill Education Population Dynamics

Population Characteristics Population density The number of organisms per unit area is the population density. Copyright © McGraw-Hill Education Population Dynamics

Population Characteristics Spatial distribution Dispersion is the spacing pattern of a population. Can be uniform, clumped groups, or random Pattern primarily driven by resources such as food Copyright © McGraw-Hill Education Population Dynamics

Population Characteristics Population ranges A species’ range is its distribution across the environment. A species might not be able to expand its population range because it cannot survive the abiotic conditions found in the expanded region. Dispersion Uniform Clumped Random Copyright © McGraw-Hill Education Population Dynamics

Add link to concepts in motion animation from page 93 here. Visualizing Population Characteristics Animation FPO Add link to concepts in motion animation from page 93 here. Copyright © McGraw-Hill Education Population Dynamics

Population-Limiting Factors Limiting factors are biotic or abiotic forces that keep populations from increasing indefinitely. Limiting factors are either density-independent or density-dependent. Copyright © McGraw-Hill Education Population Dynamics

Population-Limiting Factors Density-independent factors Any factor in the environment that does not depend on the number of members in a population per unit area is a density-independent factor. Usually abiotic, and include: Weather events Fire Human alterations of the landscape Air, land, and water pollution Population Dynamics Copyright © McGraw-Hill Education

Population-Limiting Factors Density-dependent factors Any factor in the environment that depends on the number of members in a population per unit area is a density-dependent factor. Often biotic, and include: Predation Disease Competition Parasites Copyright © McGraw-Hill Education Population Dynamics

Population-Limiting Factors Population growth rate The population growth rate (PGR) explains how fast a given population grows. Natality: birthrate of a population in a given year Emigration: number of individuals moving away from a population Immigration: number of individuals moving into a population Copyright © McGraw-Hill Education Population Dynamics

Population-Limiting Factors Population growth rate Exponential growth model: Occurs when growth rate is proportional to population size All populations grow exponentially until they encounter a limiting factor. Copyright © McGraw-Hill Education Population Dynamics

Population-Limiting Factors Population growth rate Logistic growth model: Occurs when a population’s growth slows or stops following exponential growth number of births < number of deaths when emigration > immigration. Population Dynamics Copyright © McGraw-Hill Education

Population-Limiting Factors Population growth rate Carrying capacity Carrying capacity is the maximum number of individuals in a species that an environment can support Population Dynamics Copyright © McGraw-Hill Education

Add link to concepts in motion animation from page 97 here. Characteristics of Population Growth Animation FPO Add link to concepts in motion animation from page 97 here. Copyright © McGraw-Hill Education Population Dynamics

Population-Limiting Factors Reproductive patterns Species vary in the number of births per reproduction cycle, age that reproduction begins, and in the life span. Plants and animals are placed into groups based on their reproductive factors. r-strategy k-strategy Rate strategy Carrying-capacity strategy Adapted for fluctuating environment Adapted to stable environment Generally small Generally large Short life span Long life span Many offspring Few offspring Expend little energy to raise young Invest more energy into nurturing young Copyright © McGraw-Hill Education Population Dynamics

Review Essential Questions Vocabulary What are the characteristics of populations and how they are distributed? What are the differences between density-independent and density-dependent limiting factors? What are the similarities between the different models used to quantify the growth of a population? How does carrying capacity affect reproductive rates? Vocabulary population density dispersion density-independent factor density-dependent factor population growth rate emigration immigration carrying capacity Copyright © McGraw-Hill Education Population Dynamics