Question

3.1 describe the changes that occur in tapeworm proglottids as they mature.
3.2 why is there an entire reproductive system in each proglottid?
3.3 tapeworms have been shaped by evolution for one purpose—reproduction. describe how their body plan is set up to maximize their efficiency for obtaining nutrition and translating this energy into reproductive output.
exercise 9 - 4 investigating flatworm behaviors
materials needed for all procedures
□ live planaria (dugesia tigrina)
□ pond water (or springwater)
□ clear petri dishes
□ plastic droppers
chemosensory and feeding behaviors
procedure
additional materials needed
□ small pieces of raw beef or chicken liver
□ hard - boiled egg yolks
□ toothpicks
□ dissecting microscopes
1 place a few live flatworms in a petri dish containing pond water, and use the dissecting microscope to observe the paths of the animals. are the paths straight or meandering? explain why.
2 next, using a toothpick, place a very small piece of hard - boiled egg yolk at the far side of the petri dish away from the flatworms.
3 observe their responses for the next several minutes. does the path of the flatworms change after adding the egg?
4 if not, try gently swirling the water or moving the egg yolk closer to the animals.

Explanation:

3.1 As tapeworm proglottids mature, they develop reproductive organs and accumulate eggs. They also change in size and structure to support reproduction.
3.2 Each proglottid has a complete reproductive system to increase the chances of successful reproduction. This allows for self - fertilization or cross - fertilization with other proglottids, and enables the production of a large number of eggs for the continuation of the species.
3.3 Tapeworms have a simple body plan with a large surface area for absorption of nutrients from the host's gut. Their long, flat shape allows for efficient nutrient uptake. The energy obtained is then channeled into the development and production of reproductive structures and eggs, maximizing reproductive output.
For the flatworm behavior investigation:

1. The paths of flatworms are often meandering. This is because they are searching for food, mates, and suitable environmental conditions. Their movement is not directed in a straight line as they are constantly exploring their surroundings.

2 - 4: These steps are designed to observe the chemosensory and feeding behaviors of flatworms. By presenting a food source (hard - boiled egg yolk), we can see if the flatworms are attracted to it. If they do not respond initially, techniques like swirling the water or moving the food closer can help to determine if they are capable of detecting and responding to the food.

Answer:

3.1: Development of reproductive organs, egg accumulation, size and structural changes.
3.2: To increase reproduction chances via self - or cross - fertilization and produce many eggs.
3.3: Simple body plan for efficient nutrient uptake, energy channeled to reproduction.
For flatworm behavior:

1. Paths are meandering as they explore for resources.

2 - 4: To observe chemosensory and feeding responses to food source.