Identify the abiotic and biotic factors in this picture Identify the abiotic and biotic factors in this picture. Make a list in your notebook.

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 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. Counting Laysan Albatross Nests

Population Density Measure of how crowded a population is 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 - Territorial 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

Age Structure Diagram Visual tool scientist use to show the age structure of populations Show the number of males and females in different age groups within a population Bottom heavy –capable of rapid growth Even age- stable population Top heavy- decline

Sex Ratios Proportion of males to females 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.

What is the size of a population? 1. Number of individual in an entire ecosystem 2. How individuals in a population are spaced out 3. Number of individuals per unit area/volume What is age structure? 1. Number of individuals in a population 2. Mean age the individuals are in a population 3. Number of males or females at a given age Which of the following is an example of density? 1. 1 snake in a large field 2. 7 male and 6 female adult tigers in a jungle 3. 8 parrot fish and 75 silver fish in a lake

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