DensityDependent Limiting Factors Activity Get yourself into 6
- Slides: 20
Density-Dependent Limiting Factors
Activity � Get yourself into 6 groups of 4 -5 students per group � Once you find your group, sit at a table � You have 30 seconds
Activity! � Food Station ◦ You will have one piece of “food” to share equally between you and your group members ◦ 3 stations to go to A, B, C-Rotate through them all ◦ Make notes on your worksheet � Shelter ◦ ◦ ◦ Station On the ground you will see 3 “shelters” You must stay in the “shelter” for 3 minutes If you are loud, you’re out NO SHOVING! You will be out if you shove anyone Rotate through all 3 stations Make notes on your worksheet
So what in the world is a densitydependent limiting factor? ?
Competition � Crowded populations mean the individuals have to compete for food, water, space, sunlight, or anything else necessary for survival and reproduction � Some may have enough to survive, but can’t raise offspring � Some may die of starvation � The more individuals in an area, the faster resources are used up � Could be between individuals of the same or different species
Predation � Predator-prey relationships tend to fluctuate (go up and down) � If there is a lot of prey, the predator can eat more, increasing the number of predators � If the prey decreases too much in population, there won’t be enough food for predators and so the population of predators decreases
Herbivory (Predation of Plants) � Plant and herbivore populations fluctuate just like the predator and prey populations
Parasitism and Disease � Parasites and disease causing organisms feed at the expense of the host � This can weaken or kill the host � The larger the population the easier it is for the parasite or disease to travel through hosts
Stress from Overcrowding � Some species will fight amongst each other if they are overcrowded � This fighting can cause stress leaving individuals susceptible to disease � In a few species, overcrowding can cause females to neglect or kill their own offspring
Word Splash �Organize the following words into 3 categories ◦ Density Dependent ◦ Density Independent ◦ I’m not sure
�A hurricane � Famine � A disease kills half of the population � A forest is cleared by a logging company � The plants that one species really likes has only grown half as much as usual � An early frost kills cherry trees � There is an unusually large population of wolves that eat a lot of rabbits � Territorial lions start fighting each other for habitat space � The weather has been unusually dry so the watering hole has dried up
So what did your densityindependent factors have in common?
Density-Independent Limiting Factors
So what is it? �A factor that affects all populations in similar ways, no matter the population size or density �It includes things like: �Hurricanes �Droughts �Floods �Natural Disasters
Wait a second…is it really density dependent? � So what would happen after a drought? ◦ No water so species will compete for the water � WAIT A SECOND MS. JOHNSON! YOU’VE TRICKED US!
�Sometimes a density dependent factor can lead to a density independent limiting factor like competition �What do you think? ?
Thinking back to logistic growth… � We said that something happens to stop populations from growing. � How do density-independent and dependent factors play into this?
Carrying Capacity � These limiting factors contribute to what is called carrying capacity � Defined as: the maximum number of individuals of a species an environment can support
On a graph…
Exit Ticket �On a sheet of paper, write a paragraph explaining whether or not you think that density independent factors should be considered separate from density dependent factors. �Explain your answer using information from today.
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