Chapter 4 Population Biology The study of how populations change and what influences these changes.

Florida Alligators These creatures were once endangered. After efforts were made to save the population, they are now considered pests. How did this happen? Ban hunting, Increase fines for poaching, Breed (pits), Eliminate egg eaters

Human History How has the human population changed in the past? 1000 years ago? 50-75 years ago? now?

Animals gather in groups Why? Protection, Warmth, Strength, Reduce Workload

Choose one! You are hired for a job for only 30 days. How would you like to be paid? A) $100 per day B) 1 cent per day, and it doubles each day Assignment: Graph the amount of money you will make each day. ( x=day, y=$)

Population Growth the change in the size of a population over time Population increase- Birthrate Deathrate Population decrease- Example: WWII (During/ After)

Population Growth How fast do populations grow? Few experience linear growth Pair of Houseflies  6 trillion if all eggs hatched in 1 summer

Linear vs. Exponential Growth

Exponential Growth (J-Curve) Slow start (Lag Phase) until individuals increase, then a rapid increase in number. - No limiting factors Example: Houseflies in summer, Australian rabbits

Carrying Capacity (K) The population that a particular environment can support over an indefinite period of time What determines carrying capacity?

Limited Growth S- Shaped Curve Exponential growth until limiting factors level off population at carrying capacity. What happens if a population is above carrying capacity?

Reproduction Pattern Rapid Life History (many offspring, little care) Short life-span Ex: House fly, mosquitoes, dandilions Slow Life History (few offspring, much care) Long life-span Ex: Geese, Elephant, Oak tree

Types of Population Growth What type of population growth pattern do humans have?

Growth Rate Patterns Density-dependent Limiting Factors (Cornsmut, gall) Factor increases as the population increases Ex: Disease, competition, parasites, food, space

Growth Rate Patterns Density-independent Factors Factor with no relationship to population Ex: mostly abiotic (flood, fire, temp., wind)

Interactions that Limit Size 1. Predator-Prey Relationship 2. Competition 3. Crowding and Stress

Predator-Prey Relationship Flow of energy Remove unfit members Population of one depends on the other Ex: Lynx-Hare

Competition Density-dependent factor In competition for food and mates Ex: Lichen-grass

Crowding and Stress Aggression Decrease care, fertility, immunity lead to a decrease in population size. Ex: Zoo animals, trees

Crowding and Stress Can there be under-crowding? If there is too few individuals to find a mate to reproduce. (Giant Panda) Assignment: 4.1 Review 1-5 p. 99

Human Population Section 4-2 Pages 100-103

Have humans reached K? Lack of natural resources (fossil fuels) Are we polluting at a rate we can sustain? (Global warming, Ozone layer) Running out of land HIV / Diseases Should we make laws?

Demography the study of population growth characteristics Demographers study: Population size Density/distribution Movement Birthrate/deathrate

Human Population Growth What can humans do to control their population growth that other organisms cannot? 1. No competing organisms 2. Increase food production 3. Control disease

World Population Average of: 5 births per second -2 deaths per second 3 people gained

World Population Population Growth Rate =Births- Deaths 1995 1.7% 2001 1.3% *Scientists believe Earth’s K is 10 billion

Industrialized Countries Developing Countries Third-World Countries Types of Countries Industrialized Countries Developing Countries Third-World Countries

Industrialized Countries US, Canada, England, Japan Low deathrate, declining birthrate Little or no growth

Developing Countries India and Mexico Low deathrate, high birthrate Large population growth

Third-World Countries Rwanda, Uganda Declining deathrate, high birthrate Moderate population growth

Age Structure Pyramids Does the age of the population matter? Used to make predictions Categorized by Prereproductive 0-14 Reproductive 15-44 Post-reproductive 45+

Age Structure of Countries 1 2

Fertility the number of offspring a female produces during her reproductive years the population growth of a country depends on its birth rate, death rate, and fertility rate

Age Structure example Page 103 Pre-Reproductive Years Reproductive Years Post-Reproductive Years