CHAPTER 4 Population Ecology Lesson 4.1 Studying Ecology Ernst Haeckel defined ecology in 1866 as the body of knowledge concerning the economy of nature the total relations of the animal to both its inorganic and organic environment.
Lesson 4.1 Studying Ecology Levels of Ecological Organization Ecologists study life at various levels of organization-from individual organisms to the biosphere. Ecology the study of how organisms interact with each other and with their environments The basic level of study for an ecologist is the individual organism. Individual organisms are classified into species. Species a group of individuals that interbreed and produce fertile offsprings.
Population Members of a species that live in the same area at the same time. Ex. All the golden toads living in the same area. Population ecology study of how individuals within a population interact with one another. Community all of the populations in a particular area. Community ecology study of the interactions among species. Ex. How a bee pollinates a flower or how herds of animals
migrate Ecosystem all the living and non-living things within a particular area. Ex. All the organisms, air, water, and nutrients in a place (school, town, etc) Ecosystem ecology studying the living and nonliving components of a system together. Ex. Studying the effects of the disappearance of the golden toad on the Biosphere all parts of Earth that host life, with all
of its organisms and environments. Ecologists might study how energy and matter cycle through the biosphere and influence organisms worldwide. Lesson 4.1 Studying Ecology Biotic and Abiotic Factors Biotic factors: Parts of an ecosystem that are living or used to be living Ex. Plants, animals, fungi
Did DidYou YouKnow? Know?Decaying Decayingorganisms organisms are biotic factors as long as their
are biotic factors as long as their structure structureremains remainscellular. cellular. Abiotic factors: Parts of an ecosystem that have never been living Ex. Air, wind, light, temperature, water, soil, etc Lesson 4.1 Studying Ecology Habitat
Habitat the specific environment in which an organism lives Habitats provide an organism with resources Resourceanything an organism needs to survive and reproduce, including food, shelter, and mates. Lesson 4.2 Describing Populations From 1900 to 2000, the white-tailed deer population of New York state grew from about 20,000 to more than 1 million. Densities of more than 100 deer per sq mi occur in some metropolitan areas. Lesson 4.2 Describing Populations
Population Size Population size the number of individuals in a population at a given time When population size increases or remains steady, it is a sign of a healthy
population. When population size declines quickly, it can indicate an unhealthy population headed toward extinction. Did DidYou YouKnow?
Know?The Thepassenger passengerpigeon pigeon was once North Americas most was once North Americas most abundant abundantbird. bird.Hunting
Huntingdrove drovethem themtoto extinction extinctionininless lessthan than100 100years. years. Counting Laysan Albatross Nests Determining
Population Size Ecologists often use sampling techniques to estimate population size. Instead of counting every individual in a large area, ecologists count the number in a smaller sample area then use that data to estimate the number of individuals in the larger
overall area Lesson 4.2 Describing Populations Population Density describes the number of individuals within a population per unit area Measure of how crowded a population is Larger organisms generally have lower population densities.
Northern pintail ducks Low population density: More space, resources; finding mates can be difficult High population density: Finding mates is easier; tends to be more competition; more infectious disease; more vulnerability to predators
Lesson 4.2 Describing Populations Population Distribution How organisms are arranged within an area: Random distribution: Organisms arranged in no particular pattern Uniform distribution: Organisms evenly spaced Clumped distribution: Organisms grouped near resources; most common distribution in nature
Lesson 4.2 Describing Populations Age Structure Relative number of organisms of each age group within population Can be used to predict future population growth of a population
Lesson 4.2 Describing Populations Sex Ratios Proportion of males to females Age structure diagrams give information about sex ratios. For a monogamous species, the ideal sex ratio is 50:50. Lesson 4.3 Population Growth From 1800 to today, the human population has grown from about 1 billion to more than 6.8 billionan exponential rate of increase.
Lesson 4.3 Population Growth Birth and Death Rates A populations relative birth and death rates (mortality and natality) affect how it grows. Survivorship curves show how the likelihood of death varies with age.
Lesson 4.3 Population Growth Immigration and Emigration In addition to births and deaths, population growth is affected by immigration and emigrationindividuals moving into and out of a population. Migration, seasonal movement into and out of an area, can temporarily affect population size. Lesson 4.3 Population Growth Calculating Population Growth
Determined by the following equation: (birthrate + immigration rate) (death rate + emigration rate) Growing populations have a positive growth rate; shrinking populations have a negative growth rate. Usually expressed in terms of individuals per 1000 Did DidYou YouKnow? Know? Immigration Immigrationcontributes contributes
more than 1 million more than 1 millionpeople people totothe U.S. population the U.S. population per peryear. year.
Lesson 4.3 Population Growth Exponential Growth Population increases by a fixed percentage every year. Normally occurs only when small populations are introduced to an area with ideal environmental conditions Rarely lasts long
Lesson 4.3 Population Growth Logistic Growth and Limiting Factors Growth almost always slows and stops due to limiting factors. Limiting factors: Environmental characteristics slow population growth and determine carrying capacity.
Density-dependent: Influence changes with population density. Density-independent: Influence does not change with population density. Lesson 4.3 Population Growth Biotic Potential An organisms maximum ability to produce offspring in ideal conditions Many factors influence biotic
potential, including gestation time and generation time. Organisms with high biotic potential can recover more quickly from population declines than organisms with low biotic potential.
