Breakout Questions: In this sign, what does “Maximum Capacity” mean? What would happen if that capacity was exceeded?

Population Ecology Notes Demography is the scientific study of human populations. Population: a group of organisms of one species that interbreed and live in the same place at the same time

Population Ecology Notes Limiting factor: any biotic or abiotic factor that restricts the existence, numbers, or reproduction of an organism

4 factors which affect population growth: Natality = number of births Mortality = number of deaths Immigration = number moving into a population Emigration = number moving out of a population

Patterns of population growth 1) Slow reproduction - reproduce a few young, live in stable environments, usually large in size and maintain sizes at carrying capacity. Ex: elephants, humans 2) Rapid reproduction - produce many offspring in short periods of time, live in unpredictable environments that change rapidly, usually small in size and have short life spans. Ex: mosquitoes

Population Curves J-curve (also called the Exponential Curve) Initial increase in the number of organisms is slow, and then the population begins to increase rapidly Exponential growth occurs when the number of organism rises at an ever-increasing rate

S-curve (also called the Logistic Curve) Population initially increases and then levels off Carrying capacity = the number of organisms that an environment can support over an indefinite period of time

Carrying Capacity Largest population an environment can support at any time Population can increase beyond this number but cannot stay elevated

Carrying Capacity Estimated by average population sizes or by observing population diebacks after a certain size has been exceeded

2 kinds of limiting factors Density-dependent factors: includes disease, competition, and parasites which have an increasing effect as the population increases Density-independent factors: affects all populations regardless of their density such as temperature, storms, floods, or droughts

World Population 1800s brought exponential growth food production hygiene medicine

Age-Structure Diagram Population grouped by age/gender More young than old - high growth rate Even distribution of ages - slow or no growth

Age-Structure Diagram Analysis 1 2 3 Are there more males or females? Which country would have low immigration? Which country has a high life expectancy? Which country has low fertility rate? What is happening in the third country? More females world-wide Country 1 – developing Country 3 – developed Country 3 Country 2 – transitional

Demographic Transition Change from high birth and death rates to low birth and death rates Industrial development may affect population growth rate

Stages of the Transition First stage: pre-industrial society birth rate and death rate are high Second stage: population explosion Death rates decline; birth rates stay high

Stages of the Transition Third stage: birth rate decreases Population size stabilizes (much larger than before) Fourth stage: birth rate drops below replacement level Population decreases Takes 1-3 generations for demographic transition to occur

Flow Chart Create a flow chart to summarize the stages of demographic transition Age Structure

Development and Population Some countries may never become developed, due to population growth rates incentives to reduce fertility rates

Slowing Growth Population growth is slowing this century World population growth will stabilize by 2050 at 9 billion More Is Less III

What Did You Learn? Complete the following template: The important thing about the first stage of demographic transition is: _____________ ; but, the important thing about the fourth stage of demographic transition is: _____________ .