See attached file.
Assignment 2: TwoCompeting Species
As you learned in the background text for PopEcoLab,interactions between populations of two more different species (interspecificinteractions) can affect population size and population density in a number ofways that can benefit or harm one or several species. These assignments aredesigned to help you learn about interactions that result in competition byfollowing the population growth of both the brown and blue sparrow.
Set the initial number of hawks to zero. Set the initialpopulation numbers for both the brown and blue sparrow equal to 200 birds. Set the relative insect consumption by the brown sparrow equal to zero, and set the relative seed consumption by the blue sparrow equal to zero. Keep the remaining parameters at their default values. Run several simulations and get an estimateof the carrying capacity of each species. Note: You can run ten independent simulations by going to the Initial Population view and clicking the Multiple Run Mode button. With this mode, set the number of runs to 10, then run the experiment.
What did you observe for the carrying capacity of eachspecies?.
Both carrying capacities will equal approximately 1000birds.
Go to the Competition view and use the slider to increasethe relative insect consumption by the brown sparrow, then run this experiment.
What happened to the density of thetwo sparrows? Is there a point at which one of the two species goes extinct?
Now reverse the situation and keep the relative insectconsumption by the brown sparrow equal to zero while increasing the relative seed consumption by blue sparrows. Before you run this experiment, formulate a hypothesis to predict the results of this experiment.
What happened to the density of thetwo sparrows? Is that what you expected? Explain your results.
Keep the two consumption rates of resources equal, butgradually increase both. Make sure you run several simulations for each set of consumption rates.
What happens as you increase the amount of competitionbetween the two species of sparrows? Explain these results.
Set both of the relative consumption rates back to theirdefault value of 0.50. Design experiments to investigate the effects ofresource densities on species competition, then run these experiments multiple times. Summarize your results.
Assignment 3:Predator and a Prey
Predation is a fact of life. Predators develop abilities tolocate and capture prey, and prey can evolve to develop mechanisms designed to minimize predation. However, if predators are more effective at capturing prey than prey species are at avoiding predation, then the population of prey species will be affected. Conversely, for some species, too little predation can also affect population numbers in a negative way if the prey species population exceeds its carrying capacity.
Evading Predators - Set the initial number of blue sparrowsto zero. We will focus on the population growth of the brown sparrow and the hawk. Set the initial population number for the brown sparrow equal to 200 birds and for the hawk equal to 20 birds. Design experiments to test the effects of increasing flight speed of the brown sparrow. Try several different flight speeds.
What happens? How does increasingflight speed affect the population numbers of sparrows and hawks?
As sparrow flight speed increases,eventually hawks become extinct because they are not successful enough at capturing prey.
Design experiments to test the effects of decreasing flightspeed of the brown sparrow.
What happens to the populationnumbers of the sparrow and hawk?
The Effect of Clutch Size on Predator-Prey Dynamics - Designan experiment to test the effects of changing sparrow clutch size on the predator-prey dynamics.
What happens to the populationnumbers of the sparrow and hawk as sparrow clutch size increases? What happens when sparrow clutch size decreases?
Design experiments to test the effects of changing hawkclutch size on the predator-prey dynamics.
What happens to the populationnumbers of the sparrow and hawk as hawk clutch size increases? What happens when hawk clutch size decreases?
Paradox of Enrichment - Rosenweig (1972) identified aphenomenon he called the "paradox of enrichment." He discovered that increasing the carrying capacity of a species‹for example, by adding nutrients to a pond‹can destabilize the system when the species is at risk of predation.Design experiments to test this idea.
What did you discover? Explain your answers.
Increasing the seed density (carrying capacity) of the brownsparrow causes predator-prey oscillations of increasingly larger amplitude which eventually results in extinction of the predator and often the prey.
Assignment 4: TwoCompeting Prey and a Predator
Ecologists have identified a phenomenon called"predator-mediated coexistence" (Caswell 1978), where a predatorfeeds on a dominant competitor, this allows the weaker competing species to coexist.
Design experiments where the brown sparrow alwaysoutcompetes the blue sparrow in the absence of any hawks, but by adding hawks that feed more heavily on the brown sparrow, all three species coexist.
Were you able to achieve these conditions? Explain your results.
Some predators are "specialists," which survive by focussing on one or a few abundant prey species. Others are "generalists," which need to eat a variety of less common prey to survive.
Design an experiment where a predator is unable to survivewith only one prey source, but can persist when two prey species are available.
Ecological systems are complex. Sometimes one species canindirectly affect another through its effect on a third species.
Design an experiment where hawks eat only brown sparrows(i.e., blue sparrows have the maximum flight speed needed to avoid hawks) and hawks coexist with brown sparrows when blue sparrows are absent. However, when blue sparrows are present, their competition with brown sparrows is enough to drive hawks to extinction.
What did you discover? What parameters enabled you to create this situation?
Account name: Millan1020
Let me see if I can get it to load.
I am done the first question, parts a and b. Part c is going to take some thinking. It is getting late here, so I will pick this up in the morning.
ok, no problem thanks
I believe I have it all done. Please double check for me that I answered all the questions because I worked them out of order. An extra pair of eyes looking at it is always a good idea.
I just need one thing to be sure everythring is ok. I need each response preceeded by the questions asked. I know it may seem simple but I'm dyslexic therfore I need everything to be in order.