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Transcript
Chapter 6 Highlights Mrs. Thompson APES 2014 Warm Up • What is the difference between Population, Community, Ecosystem and Biosphere? Objectives • Predict whether a change will increase or decrease a population • Identify the limiting factor(s) for a population • Use appropriate graphs and equations to represent population dynamics • Describe interactions between species • Explain the concept of ecological succession Population • Can be described using – Size – Density – Distribution • Turn and talk with table mates…..What do each of these terms mean? How would you measure each? Population Size • How many individuals of a species are found within a defined area • Count them…..but what if we can’t count them all? • We will do a catch and release lab to address this question Population Size • Predict which of the following factors increase population size….and which decrease population size – – – – – – Disease Competition for mates Increased death rate More food Limited habitat Increased predator population – Immigration – Emigration – – – – – Drought Increased Nitrogen Flood Increased sunlight High rate of reproduction – Increased prey population Can be divided into two categories • Density Dependent – – – – – – Disease Competition for mates Limited habitat Fighting Competition for food Competition for sunlight – “Limiting factor”= which ever resource determines the carrying capacity (K) • Density independent • • • – – – – – High birth rate Extra rain = more food Short lifespan Drought Increased Nitrogen Flood Increased sunlight High rate of reproduction Population Density • Number of individuals of a species found per unit of area • Count them and then divide by the area • (This should be review from Biology) Population Distribution • The pattern of how a population of a species occupies space (also review from biology) – Random • Most common for plants that have wind or animal spread seeds – Uniform • Requires uniform access to resources • Common in controlled environments….such as farms or territorial animals such as wild cats – Clumped • Provides protection from predators • Herding animals, schooling fish, flocks of birds Population Distribution Modeling Populations Logistic Growth Model • Species experiences exponential growth, but levels off when it reaches carrying capacity Exponential Growth Model • Requires unlimited resources and no density dependent interactions • Make sure that you can calculate exponential growth Reproductive Strategies K- Selection R-Selection Reproductive Strategies K- Selection • Low birth rate • Slow population growth • Controlled by the Carrying Capacity (K) • Usually organisms that produce few, large, slowly maturing, and high parental care offspring • Regulated by density dependent factors • Difficult to save from extinction R-Selection • High birth rate • Rapid changes in population • Frequently overshoot carrying capacity followed by die-off • Usually organisms that produce many, small, fast maturing, offspring requiring little to no parental care • Regulated by density independent factors Survivorship Curves K-selection • Type 1 Curve R-selection • Type 3 curve Warm Up • List several issues that might arise when attempting to measure a population in the field Population Studies • Mark and recapture • Used to make estimates of population size and density • Calculated using proportions # of tagged = # recaptured total pop # captured Animal Cracker Mark and Recapture • #1 Wash your hands….. • • • • • Each group will “collect one cup of crackers” Mark and count only the koala bears Dump the cup of crackers back into the container Mix them up Count how many koala bears were captured and how many captured were also tagged Random Sampling Methods • Provide UNBIASED samples for analysis • Must start with a homogenous section of the study site Sampling using a quadrat one of the simplest ways of sampling a habitat a quadrat: a square frame made of wood or metal A quadrat Sampling using quadrats to use the quadrat… Generate a random coordinates of the site put the quadrat at the random location Count the plants and animals inside it, ignore anything outside the quadrat repeat the process again in different parts of the field Sampling using quadrats to use the quadrat… calculate the average number of individuals per unit square for each species and measure the area of the habitat under study to estimate the density of each speices Sampling using quadrats limitations it will be hard to count fast-moving animals, this method is limited to vegetation and slow-moving or stationary animals the quadrat must also be placed on a fairly flat piece of land Activity 19.5 Sampling using a line transect this method is used to record exactly where each species or type of organism is found a line transect can be made from a string marked at regular intervals it is stretched across the habitat you want to examine all the organisms touching the string are recorded with their distance from one end of the line called the ‘origin’ Sampling using a line transect How to make a line transect, and illustrate the results with a profile diagram regular internal marks stake line transect origin graph paper height (m) soil 1m 0 1 2 3 4 5 distance from origin (m) 6 7 8 Sampling using belt transects a better method than line transect belt transect is made by: laying out two parallel strings, perhaps one metre or less apart and record the plants between them or placing quadrats continuously or in regular intervals along a transect line Quadrat 1 Quadrat 2 Quadrat 3 Quadrat 4 Quadrat 5 1m A belt transect Sampling using belt transects the distribution and relative abundance of different species along the belt transect can be studied Community • Species Interactions – Competition – Predator/Prey (Herbivores are predators! ) – Symbiotic Relationships • Parasitic • Mutualistic • Commensialist Competition • Competitive Exclusion Principle – States that two species that compete for the same limiting resource CANNOT coexist – May lead to • Resource partitioning (niche) – Temporal (time) – Spatial – Morphological • Extinction Predator Prey Graph • Interactions result in a cyclic pattern of population growth and decline Deer Me activity--Modeling a predator – prey relationship • RULES: – All animals must stay within the forest (any that don’t fit starve and die) – Start with 3 deer- after each generation, all surviving deer reproduce one offspring – Deer CANNOT over-lap in the forest – A wolf must eat at least one deer to survive – A wolf must eat at least 3 deer to reproduce – If you run out of wolves, a wolf from a nearby pack will immigrate to your forest Symbiosis Identified by effect on the host • Parasitic – Host Harmed • Mutualistic – Host Benefits • Commensialist – Host neither harmed or Benefits • Turn and talk- Come up with an example for each type of relationship Species Richness • How do each of the following impact the number of species present in a community – Latitude (Ie. Amount of sunlight/temperature) – Time – Habitat size Species Richness • Latitude – The more sunshine, the more produces, the more consumers that can be supported • Time – The longer an ecosystem is in existence, the more time for genetic and species diversity to increase • Habitat size – The more space available, the greater the room for different species Species Richness • Intermediate disturbance hypothesis states that mild disturbances such as occasional fire or floods increase species richness • May allow for invasive species population Ecological Succession • Primary – Soil layer removed or covered – Recovery must first establish a soil layer – Debris flows – Glacial Retreat – Lava flow/ volcanic ash – Urban development • Secondary – Soil layer and seed bank remains intact – Flood – Fire – Deforestation – agriculture Ecological Succession