Contemporary Biology Module 5

Question 1




As alternatives to pesticides, some of you suggested such things as adding or introducing the mosquito’s natural predators into your backyard. And that makes sense. I mean we looked at the food chain and food web interactions, right? So we know that natural predators can help balance the food web. But let’s think about that for a moment. If we do introduce more of the mosquito’s natural predators, i.e. more dragonflies, to combat our mosquito problem, what else comes with them? Their natural predator, right? Which is no big deal because their natural predators are birds and frogs. Again, we like those, yes?  But from what you learned last week, you now recognize that it doesn’t end there. Each and every organism is tied in a chain to the organisms it eats – and the organisms that eat them! 

And here all we did was plant some darn plants!  Maybe we regret that now? 😉 But no, we remember how we are dependent on the plants because of the whole soil stabilization, photosynthesis and oxygen thing, true? But now we can also recognize that by introducing plants into our backyards, we have essentially provided the first link in a “backyard” food chain. 

So let’s say we decide not to go through all of that and we decide to go ahead and spray one of the two pesticides. It’s the weekend, you’re hot and tired and you’re going to just wipe out all insects so you don’t have to bother with them or their predators! Besides, you can buy it right off the shelf and it’s easy! So let’s play that scenario out. Let’s look at how pesticides enter organisms and what the toxins are able to do. 

Remember back in Module 2 when we looked at semi-permeable membranes? Well, one of those membranes is called the plasma membrane.  As you see in your online text, the plasma membrane in animal cells is the outer most layer of the cell itself (remember, plants have an additional layer on the outside – the cell wall). So when we spray a pesticide onto the plant, and the insects land and/or walk on the plant, the toxins come into direct contact with the insect. Another mode for the toxin to enter is when the insect eats the plant that has been sprayed – this method is known as ingestion. Either way, once inside the organism, the toxins are able to move across the plasma membranes of some of the organism’s cells. The most common cells to be affected are the neurons or nervous cells. So what, you say, they’re just bugs!!  And you are right on that, but they are also animals and so are we. So, let me ask you, do you think that the toxins could affect you in a similar way? You are the one spraying, right? What if you breathe in some of the insecticides and/or you touch the plants when pruning them or pulling weeds from your beds, etc. and the toxins come in contact with your skin, or eyes, or . . . ? Let’s take a look at what the Centers for Disease Control and Prevention (CDC) and the National Pesticide Information Center (NPIC) have to say about potential side effects of our two sprays. 


United States Environmental Protection Agency

USEPA Memorandum on Lambda-Cyhalothrin

National Pesticide Information Center


United States Environmental Protection Agency

Reregistration Eligibility Decision (RED) Document for Tetramethrin

PAN Pesticides Database – Chemicals

Open a Word document.  Write your name and title the document Module 5. There are two (2) parts to this assignment. 

Part 1

Create a chart with Tetramethrin on one side and Lambda-Cyhalothrin on the other.

Write the names of each key chemical agent within the two pesticides (Tetramethrin and Lambda-Cyhalothrin).

Under each chemical agent, provide the following information: (DO NOT COPY and PASTE!!) Use your own words to explain and describe:

When was each chemical first registered with the EPA?

How do each of these chemicals behave in soil?

How do each of these chemicals behave in water?

Besides mosquitoes, what other organisms are known to be affected by each chemical? (e.g. bees?)

Are these chemicals used on food crops?

What are the Human Health Effects of each?

Most likely routes of exposure?

What are some of the symptoms associated with exposure to each drug?

What carcinogen Groups are each categorized as?

What do each of these Groups mean?

List two Environmental Health effects of each chemical.

What are the Regulations associated with these chemicals?

List at least one Precautionary Note for each chemical.

If you have to choose one or the other, based on the knowledge learned about each chemical, which one would you now choose to use in your yard and why? (short essay – minimum of 150 words)

Ok, so we know chemicals such as these are used to kill insects but are also harmful to other organisms, reside in soils for periods of time, have moderate to severe effects on water and may be harmful for humans. You see, when toxins cross the cell (plasma) membrane they affect the organelles (little organs) within the cell. So let’s look more closely at our cells. Which of the organelles do you think could be affected by toxins?

Part 2

Using your own words, state the role of the plasma membrane.

Write the names and functions of the organelles that you think could be affected by pesticides. Explain your answers.

Submit your Module 5 document to this assignment. 



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