4 Population Ecology CHAPTER

Finding Gold in a Costa Rican Cloud Forest Golden toads lived in Costa Rica’s Monteverde cloud forest. Golden toads were first described in They were extinct by Golden toads lived in Costa Rica’s Monteverde cloud forest. Golden toads were first described in They were extinct by Talk About It Why is the extinction of the golden toad a global concern?

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.”

Levels of Ecological Organization The study of how organisms interact with each other and with their environments Scientists study ecology at various levels of organization. The study of how organisms interact with each other and with their environments Scientists study ecology at various levels of organization. Lesson 4.1 Studying Ecology

Biotic and Abiotic Factors Biotic factors: Parts of an ecosystem that are living or used to be livingBiotic factors: Parts of an ecosystem that are living or used to be living Abiotic factors: Parts of an ecosystem that have never been livingAbiotic factors: Parts of an ecosystem that have never been living Lesson 4.1 Studying Ecology Did You Know? Decaying organisms are biotic factors as long as their structure remains cellular.

Habitat The specific environment in which an organism lives Habitats provide an organism with resources—anything an organism needs to survive and reproduce, including food, shelter, and mates. The specific environment in which an organism lives Habitats provide an organism with resources—anything an organism needs to survive and reproduce, including food, shelter, and mates. Lesson 4.1 Studying Ecology

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.

By counting the number of birds passing by a point per second, (several trials), ecologists estimated the size of one passenger pigeon flock at 2 billion pigeons. The flock required over 5 hours to fly past the counting location! # birds X 3600 seconds X 5hours 1second 1 hour = total population size! 100 years later— 0 passenger pigeons One flock in 1866 in southern Ontario was described as being 1 mi (1.5 km) wide and 300 mi (500 km) long, took 14 hours to pass, and held in excess of 3.5 billion birds. John James Audubon recounted a mile-wide flock of migrating passenger pigeons that passed overhead, blocking the sun for 3 days!southern Ontario

This photo shows how several ecologists sample a strip of an albatross nesting site. Average birds/strip X #strips in nesting site = # nesting albatross

Use this sample data to estimate the size of populations 111,000 carrier pigeons fly over per second The flock flies over for 5 hours (3600 seconds/hr) birds X 3600 seconds X 5 hours = 2 billion birds sec 1 hour 1000 toads X 2000 Ha = 2 million toads 1 Ha 111,000 carrier pigeons fly over per second The flock flies over for 5 hours (3600 seconds/hr) birds X 3600 seconds X 5 hours = 2 billion birds sec 1 hour 1000 toads X 2000 Ha = 2 million toads 1 Ha

Population Density Measure of how crowded a population is Low population density: benefits Less competition for resources disadvantages finding mates can be difficult more vulnerability to predators High population density: benefits Finding mates is easier Safety in numbers versus predation disadvantages more competition for resources more rapid spread of infectious diseasse Northern pintail ducks

Population Distribution How organisms are arranged within an area: Random distribution: no particular pattern Uniform distribution: evenly spaced Clumped distribution: grouped near resources; most common

Age Structure number ♀♂ in each age group used to predict future population growth Most people will still have more children. Characteristic of developing nations with low wealth & low levels of female education Most people will not have more children. e.g., China (sudden reduction in birth rate  lower % young)

Lesson 4.3 Population Growth From 1800 to today, the human population has grown from about 1 billion to more than 6.8 billion—an exponential rate of increase.

The rate of population growth is ( # individuals added/year - # individuals lost/year) total # individuals at the beginning of the year 2 ways to add individuals immigration birth 2 ways to lose individuals emigration death 2 ways to add individuals immigration birth 2 ways to lose individuals emigration death

Immigration and Emigration i mmigrate i nto a region e xit by e migration Lesson 4.3 Population Growth Migration, seasonal movement into and out of an area, can temporarily affect population size.

Calculating Population Growth Lesson 4.3 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 You Know? Immigration contributes more than 1 million people to the U.S. population per year.

Exponential Growth Lesson 4.3 Population Growth Population increases by a fixed percentage every year. Normally occurs only when small populations are introduced to an area with ideal environmental conditions—no limiting factors Rarely lasts long—at a certain population size, competition for resources increases.

Logistic Growth Lesson 4.3 Population Growth Growth almost always slows and stops due to limiting factors. Size of population stabilizes at a number the environments resources can sustain: The Carrying capacity Limiting factors: Density-dependent: Influence changes with population density. e.g., competition resources, predator success, Rate of infectious disease spread Density-independent: Influence does not change with population density. e.g., natural disasters, manmade disasters

Biotic Potential Lesson 4.3 Population Growth An organism’s 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.

Population Crash When a population grows so rapidly that within one or a few generations, it grows far above the carrying capacity of the ecosystem, then the size of the population may drop dramatically. During the period that the resources are being used at a higher than sustainable rate (more individuals than carrying capacity), then the recycling of matter can be disrupted, lowering the carrying capacity. Crashes normally occur for organisms with short lifespans, short gestations, and high #s offspring/female. However, having technology that allows continued unsustainable human population growth—by allowing extraction of resources like ground water or oil—puts humans at risk for a population crash. What will happen if we use up these resources—and can’t get them even with technology? When a population grows so rapidly that within one or a few generations, it grows far above the carrying capacity of the ecosystem, then the size of the population may drop dramatically. During the period that the resources are being used at a higher than sustainable rate (more individuals than carrying capacity), then the recycling of matter can be disrupted, lowering the carrying capacity. Crashes normally occur for organisms with short lifespans, short gestations, and high #s offspring/female. However, having technology that allows continued unsustainable human population growth—by allowing extraction of resources like ground water or oil—puts humans at risk for a population crash. What will happen if we use up these resources—and can’t get them even with technology?

Golden toad population growth 1 Describe these levels of an ecosystem for golden toads Individual Population Species (name it) Community Ecosystem 2 required abiotic factors for this species 3 required biotic factors for this species 4 resources required for the species 5 Two reasons likely for the extinction of the toads 1 Describe these levels of an ecosystem for golden toads Individual Population Species (name it) Community Ecosystem 2 required abiotic factors for this species 3 required biotic factors for this species 4 resources required for the species 5 Two reasons likely for the extinction of the toads