Population Ecology

4

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 1964. They were extinct by 1989.

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Panama Golden frog video

Katami national park video

Golden Toad of Costa Rica video

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

• Ecology is 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

Individuals

• Cell is basic unit of life → cells, tissues, organs and organ systems (recall from biology)

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• Ecologists study life above these levels, the most basic is an individual organism

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• Ecologists study relationships between organisms

Population

• A population is a species that live together in the same area
• ex golden toads in Monetverde, all the people in Teays Valley

video toad video

• Population ecology is the study of how individuals interact with each other

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Community

• All of the populations in a specific area, includes plants, fungi, other animals

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• Community ecology is the study of interactions among species

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Ecosystem

• Include living and non-living things

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• ex: Monteverde's cloud-forest ecosystem of all organisms that live there, the air, water and nutrients they use

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• Ecosystem ecology is the study the living and nonliving things of a system together.

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Biome

• Include living and non-living things

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• distinct ecological communities of plants and animals living together in a particular climate

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• Many different biomes

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Biosphere

• The Biosphere includes all the organisms and the parts of earth that hosts life.

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• Examine energy and matter cycles that influence organisms.

Biomes That Will Be Studied

AQUATIC BIOMES

• Freshwater
• Freshwater wetlands
• Marine
• Coral reef
• Estuaries

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TERRESTRIAL BIOMES:

• Tundra
• Rainforest
• Savanna
• Taiga
• Temperate forest
• Temperate grassland
• Alpine
• Chaparral
• Desert linked to http://kids.nceas.ucsb.edu/biomes/freshwater.html

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Biome Mini Project

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• Task: Given your assigned biome, create a presentation that highlights the following:

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• Regions of the world the biome is located with a map highlighting these areas
• Climate description & climatograph
• Describe the landscape and show an image
• At least 3 Plants found there with pictures
• At least 3 animals found there with pictures

Project handout

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Climographs and Maps

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Biotic and Abiotic Factors

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• Biotic factors: Parts of an ecosystem that are living or used to be living
• Abiotic factors: Parts of an ecosystem that have never been living

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Lesson 4.1 Studying Ecology

Did You Know? Decaying organisms are biotic factors as long as their structure remains cellular.

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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.
• Migration- seasonal movement into and out of an area, can temporarily affect population size.

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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.

Video 1

video 2

Article

video

Population Size

Lesson 4.2 Describing Populations

• Population Size - The number of individuals in a population at a given time
• Sudden and dramatic decreases in population size can indicate an unhealthy population headed toward extinction.
• Ecologists often use sampling techniques to estimate population size.

Did You Know? The passenger pigeon was once North America’s most abundant bird. Hunting drove them to extinction in less than 100 years.

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Counting Laysan Albatross Nests

Population Density

Lesson 4.2 Describing Populations

• Population Density - Measure of how crowded a population is
• Larger organisms �generally have lower �population densities.
• 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

Northern pintail ducks

Population Distribution

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

Age Structure Diagrams

Lesson 4.2 Describing Populations

• Relative number �of organisms of each age group within population
• Can be used to predict future population growth of a population

Sex Ratios

Lesson 4.2 Describing Populations

• 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 billion—an exponential rate of increase.

Birth and Death Rates

Lesson 4.3 Population Growth

• A population’s relative birth (natality) rate and death (mortality) rate affects how it grows.
• Survivorship curves show how the likelihood of death varies with age.

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Immigration and Emigration

Lesson 4.3 Population Growth

• In addition to births and deaths, population growth is affected by immigration and emigration.
• immigration - individuals moving into a population
• emigration - moving out of —individuals moving into and out of a population.
• Migration, seasonal movement into and out of an area, �can temporarily affect �population size.

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Calculating Population Growth

Lesson 4.3 Population Growth

• Determined by the following equation: �(birth rate + 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

• Exponential Growth means that the 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

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Logistic Growth and Limiting Factors

Lesson 4.3 Population Growth

• Logistic Growth - 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.

Biotic Potential

Lesson 4.3 Population Growth

• Biotic potential - 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.

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