MP

Population Dynamics and Endangered Species

Population Size Estimation

  • Scientists determine population size through various methods.
  • Examples of populations to estimate:
    • Zebras
    • Bass fish in a lake
    • Oak trees in a forest

Endangered Species

  • Black-footed ferret: An endangered North American carnivore related to a weasel.
  • Determining when an animal is endangered is a key aspect of conservation.

School Field Study: Estimating Dandelions or Violets

  • Task: Estimate the number of dandelions or violets on the school lawn.
  • Equipment: String, meter sticks.
  • Limitations: Data gathering time is limited to 30 minutes.
  • Steps:
    • Step 1: Submit a plan.
    • Step 2: Gather data.

Methods for Measuring Population Size

  • Random Sampling
  • Mark and Recapture

Chapter 5 - How Populations Grow

  • Population: A group of the same species in an area.

Population Density

  • Population Density: The number of individuals in an area.

Population Growth

  • Population Growth is influenced by:
    • Number of births
    • Number of deaths
    • Emigration (out)
    • Immigration (in)
  • Growth (N) = Birth Rate - Death Rate \text{Growth (N) = Birth Rate - Death Rate}

Population Growth Rate Example

  • In Springfield, 45 babies are born in the year 2008, and 15 people died that same year.
    • Positive Growth rate = increase
    • Negative Growth rate = decrease
    • Zero Population growth = deaths = births

Exponential Growth

  • Exponential Growth: Reproduction at a constant rate.
    • Occurs under ideal conditions (no limits).
    • J-shaped curve.

Logistic Growth

  • Logistic Growth: Resources become less available, growth slows or stops.
    • S-shaped curve.
  • Carrying Capacity: The number an environment can support.

Limits to Growth

  • Limiting Factor: Causes population growth to decrease.
  • Density-Dependent Factors: Influence is dependent on population size.
    • Competition
    • Predation
    • Disease

Density-Independent Factors

  • Density-Independent Factors: Influence is not dependent on population size.
    • Unusual weather
    • Natural disasters
    • Some human activities

Predator - Prey Relationship

  • Predator - Prey Relationship: Predators control prey populations.
    • As prey numbers increase, so do predators.
    • Prey will always outnumber predators.

Quick Check Questions

  1. Organisms moving OUT of an area is called emigration.
  2. The graph shows a logistic curve.
  3. The arrow indicates the carrying capacity
  4. The number of deer that can be supported by the island is 90-96
  5. The information needed to determine the population growth rate: birth rate, death rate and number of immigrants.
  6. A flood causes a 30% reduction in the population of crocodiles. This is considered a density independent factor.
  7. If an area is a negative rate of population growth, then the population is declining.
  8. Population density refers to the number of individuals in an area.

Demography

  • Demography: The study of human population growth.
    • Explains how populations change over time.

Age Structure Diagrams

  • Show the percentage of people alive at each age group.

Analysis of Age Structure Diagrams

  1. A country where the king orders the deaths of all the baby boys
  2. A country at war, many young men die in that war
  3. A country with poor health care for women, many die in childbirth
  4. A country where AIDS kills people in their 30s

Endangered and Threatened Species

  • Animals are classified as ENDANGERED when their numbers are low, meaning they may become extinct.
  • Threatened = any species which is likely to become endangered within the foreseeable future.

Endangered Species Act (ESA)

  • Congress passed the Endangered Species Act (ESA) in 1973.
  • The ESA protects endangered and threatened species and their habitats by prohibiting the “take” of listed animals.
  • Take means “to harass, harm, pursue, hunt, shoot, wound, kill, trap, capture, or collect or attempt to engage in any such conduct.”
  • ESA Only applies to animals in the U.S.
  • International laws protect animals in other countries.

U.S. Fish and Wildlife Service

  • Endangered Species Homepage
    *Cave Amphipod, endangered species found in the Midwest, including caves near St. Louis.

Charismatic Megafauna

  • Charismatic megafauna are large animal species with widespread popular appeal, which are often used by environmental activists to achieve environmentalist goals.
  • Mini-Project: Create a poster or infographic that showcases an endangered species. Present your species to the class to convince them to donate to an organization dedicated to saving the species.