Read the DDT Story and Answer the Following Questions

PESTICIDES & BIOACCUMULATION

The DDT Story

Read The DDT Story and answer the following questions:

1.  What is the chemical name for DDT?

2.  What was DDT used for during World War II?

3.  How does DDT enter a food web?

4.  What were some of the ecological effects of spraying DDT?

5.  In your own words explain why animals at the top of the food chain are at a higher risk from poisons in the environment. How are humans impacted?

The Danger of Pesticides:

Pesticides such as DDT that contain ______are soluble in ______but not in ______.

This means they cannot be released in ______or ______and instead accumulate in ______.

What does this mean for animals in the food chain?

The ______the tropic level, the greater the ______of toxins. This process is called ______/______.

How Bioaccumulation works:

The Tertiary Consumer (hawk) eats the Secondary Consumer (bird) and absorbs ____ of the ______from the ______.

The Secondary Consumer (bird) eats the Primary Consumer (caterpillar) and ______the toxins in its ______.

The Primary Consumer (caterpillar) eats ______of the leaves (Producer) contaminated with the ______.

The Producer (plant) is ______with the pesticide and some is ______in by the plants.

Bioaccumulation of DDT

How does a pesticide such as DDT build up in the bodies of organisms in the food chain?

Imagine a pond near a farmer’s field that is infested with harmful insects. The farmer sprays the field with DDT. Wind blows some of the pesticide onto the marsh plants. Each plant absorbs 5 mg of DDT insecticide into their cells.

Marsh Ecosystem Food Chain:

Marsh plants Minnows perch fish red-tailed hawk

Complete the table of calculations to determine the bioaccumulation of the DDT.

Organism / Organism consumed / Amount of DDT present in each organism consumed (mg) / Total number of organisms consumed in a year / Amount of DDT accumulated by the organism (predator) (mg)
Minnow / Marsh plants / 5 mg / 100
Perch / Minnow / 50
Hawk / Perch / 20

Questions:

1.  How much has the amount of DDT increased from the marsh plants to the body of the red-tailed hawk?

2.  What will happen to the DDT when the hawk dies?

3.  The farmer was going to use a new pesticide, AST. It disappears from the environment after only seven days. How would the accumulation of AST have compared to the accumulation of DDT?

4.  Why must the use of new pesticides be controlled and monitored very carefully?

Pesticides

Read the case study on pesticides and answer the following questions.

1.  In your own words define the following terms

Pesticides –

Pests –

2.  a) What is the major difference between first and second generation pesticides compared to modern pesticides? Why does this change make them somewhat safer?

b) How do the modern pesticides work?

3.  Why do pesticides eventually become useless?

4.  List the advantages and disadvantages of using pesticides in the T-chart below.

Advantages Disadvantages