What kind of plants do we see in a climax community? Agenda for Thursday May 26th Communities and populations notes Random sampling lab

Community Def. – a group of interacting populations that occupy the same area at the same time Different organisms occupy different biomes Different adaptations

Communities Limiting factors – any biotic or abiotic factor that limits the number, reproduction, or distribution of an organism Sunlight, food, temperature Tolerance – ability of an organism to survive when subjected to abiotic or biotic factors Upper and lower limit = range

Recall… Populations – members of a single species that live in once place at a single time

Population Characteristics Population Density – # of organisms per area Dispersion – pattern of spacing of a population within an area Based on available resources (food) 3 types Uniform Clumped Random

Dispersion Pattern: Uniform

Dispersion Pattern: Clumped

Dispersion Pattern: Random

Dispersion Smaller animals usually clump Larger animals usually independent Fish Q: What advantage do smaller fish (animals) gain by forming schools (clumped groups)? Safety, confuses predators

Q: Which type of population distribution allows you to predict more accurately how many individuals reside in a given area?

Determine how many oak trees are in the forest using the random sampling technique. Use the grid.   7 3 5 8 Agenda for Friday May 27th Quiz Population sampling techniques Mark and recapture

Question If you were in charge of a team given the responsibility to determine the number of sunfish in Horseshoe Lake, discuss with a partner how would you accomplish this task.

Sampling  A technique called sampling is sometimes used to estimate population size. Organisms in a few small areas are counted and projected to the entire area.  Example: A biologist counts 10 squirrels living in a 200 square foot area, she could predict that there are 100 squirrels living in a 2000 square foot area. 

Questions A biologist collected 1 gallon of pond water and counted 50 paramecium.  Based on the sampling technique, how many paramecium could be found in the pond if the pond were 1,000 gallons? What are some problems with this technique?  What could affect its accuracy?

Mark and Recapture Biologists use traps to capture the animals alive and mark them in some way  Animals are returned unharmed to environment  Animals trapped and data is taken on how many are captured with tags A mathematical formula is then used to estimate population size

Formula for Mark and Recapture Ecologists marked 20 bears in an area. Over 5 years they captured 100 bears. Of those 100 captured 50 had a tag. What is the population of the bears? Population estimate = (total number captured) x (original # with mark) (Total number captured with mark)

What is mark and recapture? Agenda for Tuesday May 31st Mark and recapture notes and lab Finish population notes

Mark and Recapture Concerns Capturing the animal could injure the animal or scientist Disturb animal's normal behavior pattern The marks used to track the animals, such as ear punches, may cause injury to the animals or get lost between captures Marked animals may be more or less attractive to predators because of markings Assumes all animals require the same effort to get caught, might catch the weaker or younger animals more Some animals learn to fear the traps and avoid recapture or become trap-happy and attempt to get caught when they learn there is food involved and that they will be re-released

Population Ranges Limiting Factors Abiotic conditions Temperature Humidity Rainfall Sunlight Biotic conditions Predators Competitors parasites

Density independent factors Def. – any factor that does not depend on the number of organisms in a population in a given area Abiotic Weather – drought, flooding, extreme heat/cold, tornados, hurricanes Water Fire Sunlight

Density Dependent Factors Def. – any factor that depends on the number of organisms in a population in a given area Biotic factors Predation, disease, parasites, competition

Predation More members of a population = more predators

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

Competition When resources become limited animals compete Within a population or between 2 different species Lead to starvation – population can decrease

Population Growth Rate How do we figure out 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

Different Growth Rates

What is a density dependent factor What is a density dependent factor? What is a density independent factor? Agenda for Wednesday June 1st Finish notes Human pop. Graphing Biodiversity

Exponential Growth Rate Starts slow – few organisms Faster because all organisms are reproducing Rarely happens WHY? Limiting factors – food, space

Logistical Growth Rate Logistic growth occurs when a population’s growth slows or stops following exponential growth Carrying capacity

Carrying Capacity Maximum number of individuals that an environment can support for the long term Limited by energy, water, oxygen, nutrients available Population grows until carrying capacity Births outnumber deaths Exceed carrying capacity then deaths outnumber births

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

Human Population Growth

Trends in Human Population Growth Was slow and stable Recent increase in growth Technology – agriculture, medicine, shelters Developing countries add more than developed countries

More trends Zero population growth Age structure 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+)

Human Carrying Capacity Humans have a carrying capacity Technology allows an increase in carrying capacity Concerns about reaching/exceeding carrying capacity resources being used

Describe what is happening to the population in the graph below. Agenda for Wednesday Jan 26th Finish Notes Human pop. graph