What kind of plants do we see in a climax community? Agenda for Tuesday Jan 27 th 1.Population Notes

What kind of plants do we see in a climax community?

Agenda for Tuesday Jan 27th 1.Population Notes

• Why study populations?– Learn how organisms change over time, problems in

an environment, and relationships between organisms

Population Growth Rate

• Must know birthrate and mortality• Emigration – moving out of a pop.• Immigration – moving into a pop.

– Immigration rate = emigration rate

• Calculating growth rate=(population at end – population at beginning)

Population at beginning

Exponential Growth Rate

• Occurs when organisms have ideal conditions

• More individuals = faster growth

• Rarely happens– WHY?– Limiting factors

Logistical Growth Rate• Populations go through

different growth phases– Lag Phase – slow growth– Exponential growth – rapid

growth, few die, many reproduce

– Population growth slows down

– Steady state – population levels, birth rate = death rate

Lag

Exponential

Slows

Steady state

Questions

• The human population is currently growing at an exponential rate. What does this mean about our birth and death rates?

• The Mantled Howler Monkey is currently considered an endangered species. What does this mean about its birth and death rates?

Carrying Capacity• Maximum number of individuals that an

environment can support– Measured in winter

Limiting Factors…• Anything that prevents the number,

reproduction, distribution, growth of an organism– Abiotic– Biotic

• Tolerance – ability of an organism to survive when subjected to limiting factors– Upper and lower limit = range

Population Ranges

• Species are limited to where they may exist• Abiotic conditions

Temperature HumidityRainfall Sunlight

• Biotic conditionsPredatorsCompetitorsparasites

Density independent factors

• affects the size of a population regardless of the population density– Abiotic

• Weather, Water, Fire, Sunlight, temperature• Humans – dams, pollution

Density Dependent Factors• A factor whose effects on the size or growth of

population vary with the population density – Biotic factors

• Predation, disease/parasites, competition• Food, water, shelter (resources)

Disease/Parasites• Outbreaks of disease tend to occur when

population size has increased– Disease is transmitted faster– True for humans as well as animals

• Parasites increase at higher densities

Questions

Imagine a population of skunks. Imagine that the skunks are reproducing at a very high rate, and the skunk population is growing rapidly.

a) List a possible density-independent factor that could stop the skunk population’s growth.

b) List a possible density-dependent factor that would limit the skunk population’s growth.

Population Density

• # of organisms per area

• Dispersion – pattern of spacing of populations– 3 types

• Uniform• Clumped• Random

Dispersion Pattern: Uniform

Dispersion Pattern: Clumped

Dispersion Pattern: Random

Reproductive strategies

R-strategy (rate strategists)• Produce as many offspring as possible in a short

time– Little energy in raising young

K-strategists (carrying capacity strategy)• Few offspring that have a better chance of living

– Expend a lot of energy raising young

Compare and contrast r and k reproductive strategies

Agenda for Wednesday Jan 28th 1. Invasive species project

Quiz tomorrow

What is a density independent factor? A density dependent factor?

Agenda for Thursday Jan 29th 1.Go over HW2.Quiz3.Human populations

Human Population Growth

• It took all of human history up to the early 1800s for world population to reach 1 billion people

• until 1960 to reach 3 billion• Today, the world gains 1 billion people every 11 years• The current population is almost 8.5 times larger than

the population of 760 million at the beginning of the Industrial Revolution

• At current growth rates, the world population could double in as little as 58 years

http://www.census.gov/popclock/

Human Population Growth

What’s Behind Population Growth

• Three Factors – Fertility– Infant Mortality– Longevity

• Animal Domestication and Agriculture– Provided for a few to feed

many

• Industrial Revolution– Growth of Cities and

Infrastructure• Water• Energy• Transportation

– Increased Productivity– Nutrition– Sanitation– Medicine

Resource Consumption (6)

• High consumption

• Getting worse• Rate increase

faster than population growth

Human Carrying Capacity

•Technology has allowed us to raise Earth’s carrying capacity for our species time and again.

•Tool-making, agriculture, and industrialization each enabled humans to sustain greater populations.

Our ‘Commons’ are in Danger

• Atmospheric pollution and climate change• Water pollution, including ground aquifers• Deforestation and loss of oxygenation • The oceans, coral reefs and their bounty• National parks, wildernesses and wetlands• Nonrenewable natural resource depletion

– Fossil fuels, mineral ores, topsoil…..

Biodiversity is in Danger

• Humanity has spawned a species extinction to rival the 5 great extinctions of 65 - 440 million years ago

• Recovery times from the great extinctions took 10’s of millions of years

• Biodiversity is essential to life on Earth and holds untold treasures for the future

• An ecological ethic is emerging

Human Population Growth

• Zero population growth – birth rate + immigration rate = death rate +

emigration rate

• Age structure– # of males and females in three age groups

• Pre-reproductive (0-19), reproductive (20-44), and post –reproductive (45-80+)

Why do some countries have a growing population while other countries have a declining population?

Concept Web

• Social, economic, envt• Positive, neutral, neg impacts on more people

What event in human history helped spark our population

growth?

Agenda for Friday jan 31st 1.Quiz2.Present

What concerns are there about the increase in human population?

Agenda for Monday Feb 3rd 1.Present2.Biomes