Question

part b
boxer crabs (lybia tesselata) are small crabs that carry sea anemones in their claws. the anemones are used for defense and to obtain food. the relationship between the boxer crab and the sea anemone is an example of mutualism, where both organisms benefit. the crab gets protection from predators, and the anemone gets a means of transportation and access to food particles.
it has been observed that when boxer crabs are removed from their natural environment, the anemones can survive on their own. however, the crabs seem to rely on the anemones for protection. if a crab loses its anemone, it will fight to get a new one from another crab or from the environment. both crabs and anemones can reproduce on their own, ensuring the continuation of their species.
in a study, boxer crabs were collected from three reef sites of different depths. the table below shows the data collected.

	reef a (depth = 5 m)	reef b (depth = 10 m)	reef c (depth = 15 m)
boxer crabs with one anemone	3	1	0
boxer crabs with two anemones	12	7	5
total boxer crabs	16	8	5

1. calculate the percent of boxer crabs that have two anemones, for each location.

reef a: ______ %
reef b: ______ %
reef c: ______ %

1. suggest one reason why the percent of crabs with two anemones increases with depth.

1. suggest one reason why there are so few boxer crabs without anemones.

1. list three things that you do not know about the data collected in this table.

1. in order to accept this data as reliable (and therefore appropriate to compare between reefs), the data must have been measured consistently between all of the reef sites. list 3 things that the researchers could do to keep consistency within their collections.

Explanation:

Step1: Calculate percent for Reef A

Percent = $\frac{\text{crabs with two anemones}}{\text{total crabs}} \times 100 = \frac{12}{17} \times 100 \approx 70.6\%$

Step2: Calculate percent for Reef B

Percent = $\frac{7}{8} \times 100 = 87.5\%$

Step3: Calculate percent for Reef C

Percent = $\frac{4}{4} \times 100 = 100\%$

Step4: Reason for increasing percent with depth

Deeper waters may have fewer predators, so anemones (which protect crabs) are more beneficial, leading to more crabs retaining two anemones.

Step5: Reason for few crabs without anemones

Anemones provide protection from predators; crabs without anemones are more likely to be eaten, so they are rare.

Step6: Unknown data details

1. The geographic location of each reef.
2. The time of year data was collected.
3. The size/age of the boxer crabs.

Step7: Consistency measures for data collection

1. Use the same sampling method (e.g., quadrat size) at all reefs.
2. Collect data during the same time of day/season.
3. Train all researchers to identify boxer crabs and anemones uniformly.

Answer:

1. Reef A: ~70.6%, Reef B: 87.5%, Reef C: 100%
2. Deeper waters have fewer predators, so anemone protection is more critical.
3. Anemones protect crabs from predators; crabs without them are less likely to survive.
4. 1. Geographic location of reefs; 2. Data collection season; 3. Crab size/age.
5. 1. Standardize sampling methods; 2. Collect data at the same time; 3. Uniform species identification training.