Question

1. examine the following ld50 chart: ld50 test for mtbe a scientist wanted to study the effect of a gasoline additive mtbe (methyl tertiary butyl ether) on tigriopus californicus (a common marine copepod). six different concentrations of mtbe were prepared in separate test tubes, and 100 t. californicus were placed in each tube. after 24 hours, the number of organisms that died were counted and recorded. the results of the experiment are shown below. mtbe concentration (%) number of dead t. californicus <0.0001 10 0.001 10 0.01 20 0.1 55 1 90 10 100 which of the following conclusions would be true based only the information in the graph? (a) there should be 50 dead t. californicus in a population of 100. (b) there should be 55 dead t. californicus in a test population of 90. (c) there should be 100 dead t. californicus in a test population of 100. (d) only 10 t. californicus would survive in a test population of 100. (e) 100 t. californicus would survive in a test population of 100.

Explanation:

Step1: Understand LD50 concept

LD50 is the dose at which 50% of a test - population dies. Here, we have data on different MTBE concentrations and the number of dead T. californicus.

Step2: Analyze the data

When the MTBE concentration is 0.1%, 55 out of 100 T. californicus die. But we need to find the general trend related to LD50 - like scenarios. When the MTBE concentration is 1%, 90 out of 100 die. When it is 10%, 100 out of 100 die.

Step3: Evaluate options

Option (A) has no basis in the given data as there is no information about a situation where exactly 50 die out of 100. Option (B) is wrong as 55 die at 0.1% concentration but the option is not framed in a context - appropriate way. Option (C) is wrong because it is not always the case that 100 die in a test - population of 100. Option (E) is wrong as we see deaths at different concentrations. Option (D) is correct because at a high enough concentration (e.g., 10%), 100 out of 100 die, so only 10 would survive in a population of 100 if the same lethality conditions apply.

Answer:

D. Only 10 T. californicus would survive in a test population of 100.