PREDATOR-PREY RELATIONS LAB
Predators and prey are organisms that interrelate, and they can influence on another’s success in reproduction. Predators are organisms that consume other organisms-their prey. These two organisms evolve together. They live in an environment where they must develop certain adaptations to survive. When an adaptation is developed, it gives an organism certain physical characteristics that create an advantage for survival and can come to dominate in a population. An adaptation aids survival by either decreasing a prey's chance of being eaten, or by increasing a predator's chance of obtaining food to survive and reproduce. Predators must fight for food. They face density-independent factors which are factors that limit resources, but they cannot be controlled; an example would be bad weather or wildfires. Density-dependent factors are things that can be controlled such as the amount of competition in an environment. For example, if a prey’s traits allow it to run faster, the predator must also have the characteristics to allow it to run fast enough to catch its prey. Many people confuse adaptions with evolution, but they are not the same. Adaptions are changes in an animal that happen in one generation, while evolution occurs over many generations (Modern Biology, 2006). Charles Darwin had a theory that was the opposite of adaptations. Charles Darwin’s theory of natural selection was basically “survival of the fittest.” When organisms reproduce and exceed the carrying capacity, the competition in the environment increases. Because of this, some organisms will not survive (Theory of Natural Selection). It was then that Darwin realized those organisms who were most suited for the environment were the ones who will live on and
reproduce (Darwin’s Theory of Evolution). For example, picture two birds in an environment. One bird has a long beak and the other has a short beak. The bird with the long beak is able to reach into the holes in the ground and eat the seeds, but the other cannot. The bird populations with the long beaks will be able to survive and reproduce while the population of birds with the short beaks will thin out and eventually go extinct (Modern Biology, 2006).
Which predators will be able to survive and reproduce based on their characteristics, adaptations to the environment, density-dependent factors such as competition for food, and density-independent factors such as bad weather or wild fires?
The spoon will be the predator that survives, reproduces, and dominates the population. If there is a competition between predators over a prey, then the spoon will easily be able to use its bowl-like shape to easily scoop up the prey. If the prey is hidden in the grass, then the spoon will be able to slide through the grass and scoop up any prey hiding.
1. 300 pieces of corn
2. 300 pieces of black beans
3. 300 pieces of lima beans
4. 100 pieces of pinto beans
5. Plastic forks with one tongue removed (Broken Forks)
6. Plastic forks
7. Small plastic knives
8. Plastic spoons
9. Tweezers (forceps)
10. A grass field approximately 15 meters square or a carpeted area about the same size. 11. Styrofoam 6-8 oz. cups
12. Stop watch
1. Distribute 100 pieces of corn, lima beans, and black beans onto the field. 2. Divide the class into 5 groups that are as close to equal as possible. 3. Give each member of one group forks, of another group spoons, of another group broken forks, of another group knives, and the last group forceps. (If there are no forceps available, the lab can be demonstrated with only 4 groups.) 4. Every student gets a Styrofoam cup.
5. Instruct the students that they are individual predators with structural variations. The beans and the corn are the prey. The prey must be picked up with the feeding mechanism (forks, knives, spoons,...
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