Estimating Population Size

Journal Entry What types of populations does random sampling work well with? What are the drawbacks of using random sampling? How would you sample a mobile population?

How do we monitor moving populations? Look at the following video – Wildebeest Migration

Understanding Populations - Big Ideas Population sizes change according to changes in the environment. The size and growth rate of human population has changed drastically over the last 200 years. Those changes have led to profound changes to almost every place on Earth.

How Populations Change in Size GOALS Describe the 3 main properties of a population Use two methods to estimate population size Explain how behavior influences population dsitribution

The Decline of the Passenger Pigeon How does a species go from having billions to extinct in just one century…The Passenger Pigeon Story. Extinct in the wild since 1900 and last died in the Cincinnati Zoo 1914.

Review: What is a population? Population: all the members of the same species that live in the same place at the same time Field mice living in a corn field, wolves in Yellowstone National Park, blacks bears in northern New Jersey

Population Size Why care about the size of the population? How can scientists estimate the population (say of Elephant Seals on a beach in CA)?

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.

Estimating Population How can you estimate the population of trees in this valley? WHY NOT COUNT THEM ALL? WHY IS SAMPLING NEEDED?

Random Sampling

Mark and Recapture Common way of estimating population size

Population Density What is population density? What are advantages and disadvantages of high and low density?

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

Population Distribution How organisms are arranged within an area: RANDOM CLUMPED UNIFORM Occurs when individuals hold territory or compete for space Plants in a desert Occurs where resources needed are found throughout Wildflowers in a meadow Most Common. Occurs where resources are together Water hole in desert, humans in cities

Many bird species are territorial Many bird species are territorial. In territorial birds species, what kind of population structure would you expect? UNIFORM

Population Distribution Random distribution: Organisms arranged in no particular pattern Uniform distribution: Organisms evenly spaced Clumped distribution: Organisms grouped near resources; most common distribution in nature

What type of distribution? CLUMPED WHY?

Ocearch - tracking shark movement This site tracks shark movement by tagging sharks In 2015 Mary Lee was at one point less than ¼ mile from the shore

History of Black Bear Sightings in New Jersey

Why is it important to estimate the populations of sharks and black bears?