Biology Bellwork – 10/17/12 Describe some observations you can make about populations of insects over the course of a year? The populations of flies or mosquitoes go up in the spring and summer and decline in the fall. Do they die out completely in winter? A few individuals in each population find places to go over-winter, and some migrate.

Biology Bellwork – 10/24/12 Explain how the improvement in shelter can increase the survival rate of a human population. Adequate shelter provides defense against extremes of the environment such as temperature, precipitation, and wind. In addition, shelter provides defense against biotic factors in the environment such as venomous snakes, mosquitoes, other insects that harbor parasite, and large predators such as wolves and bears. All of these have the potential to shorten the life span of individuals, thereby affecting the human population as a whole.

Alternative Assignments Write a paragraph comparing density-dependent and density-independent factors that can limit human populations. Imagine that you are a housefly. Write a short comic strip, with illustrations, explaining what it is like to be a r-strategist from a fly’s view-point.

Bellwork 10/25/12 Define the followings vocabulary terms: Carrying Capacity The maximum number of individuals in a species that an environment can support for the long term. Limiting Factor Biotic or abiotic factor that restricts the number, distribution, or reproduction of a population within a community.

Population Ecology

Population Dynamics Population: All the individuals of a species that live together in an area at the same time Demography: The statistical study of populations, allows predictions to be made about how a population will change Although several species may share a habitat they each have their own niche. A niche is a very narrow range where a species fits within a habitat.

Population Dynamics Three Key Features of Populations Size Density Dispersion Although several species may share a habitat they each have their own niche. A niche is a very narrow range where a species fits within a habitat.

Three Key Features of Populations Size: number of individuals in an area Although several species may share a habitat they each have their own niche. A niche is a very narrow range where a species fits within a habitat.

Three Key Features of Populations Growth Rate: Birth Rate (natality) - Death Rate (mortality) How many individuals are born vs. how many die Birth rate (b) − death rate (d) = rate of natural increase (r) Although several species may share a habitat they each have their own niche. A niche is a very narrow range where a species fits within a habitat.

Three Key Features of Populations Density: measurement of population per unit area or unit volume Pop. Density = # of individuals ÷ unit of space Although several species may share a habitat they each have their own niche. A niche is a very narrow range where a species fits within a habitat.

How Do You Affect Density? Immigration: movement of individuals into a population Emigration: movement of individuals out of a population Density-dependent factors: Biotic factors in the environment that have an increasing effect as population size increases (disease, competition, parasites) Density-independent factors: Abiotic factors in the environment that affect populations regardless of their density (temperature, weather)

Factors That Affect Future Population Growth Immigration + + - Population Mortality Natality - Emigration

Three Key Features of Populations Dispersion: describes the spacing of organisms relative to each other Clumped Uniform Random Although several species may share a habitat they each have their own niche. A niche is a very narrow range where a species fits within a habitat.

Population Dispersion

How Are Populations Measured? Population density = number of individuals in a given area or volume Count all the individuals in a population Estimate by sampling Mark-Recapture Method

How Do Populations Grow? Idealized models describe two kinds of population growth: Exponential Growth 2. Logistic Growth

Carrying Capacity Carrying Capacity (k): The maximum population size that can be supported by the available resources There can only be as many organisms as the environmental resources can support Although several species may share a habitat they each have their own niche. A niche is a very narrow range where a species fits within a habitat.

Bellwork – 10/26/12 An employer offers two equal jobs of one hour each for fourteen days. The first pays $10/hour. The second pays only 1 cent the first day, but the rate doubles each day. Which job would you rather have? Job #1  $10 x 14 days = $140 Job #2  $0.01 + $0.02 + $0.04 + $0.08 + $0.16 + $0.32 + $0.64 + $1.28 + $2.56 + $5.12 + $10.24 + $20.48 + $40.96 + $81.92 = $163.83

Exponential Growth Curve Figure 35.3A

Logistic Growth Curve

Factors Limiting Growth Rate Declining birth rate or increasing death rate are caused by several factors including: Limited food supply The buildup of toxic wastes Increased disease Predation

“Booms” and “Busts”

Reproductive Strategies R Strategists Short life span Small body size Reproduce quickly Have many young Little parental care Ex: cockroaches, weeds, bacteria

Reproductive Strategies K Strategists Long life span Large body size Reproduce slowly Have few young Provides parental care Ex: humans, elephants

Age Distribution Distribution of males and females in each age group of a population Used to predict future population growth

Human Population Growth J curve growth Grows at a rate of about 80 million yearly r =1.3% Why doesn’t environmental resistance take effect? Altering their environment Technological advances The cultural revolution The agricultural revolution The industrial-medical revolution

The Human Population Doubled three times in the last three centuries About 6.1 billion and may reach 9.3 billion by the year 2050 Improved health and technology have lowered death rates

History of the Human Population