# Presentation: 493070

## Opening Questions

**Does DDE accumulate in all species equally? Why not? What type of species is most likely to accumulate large amounts of DDE due to biomagnification?**** **
**When was DDT banned?**** **

**Opening Questions**

**Notes:**
The Opening Questions for the day are presented. Students can come in a quietly mark down their answers to these questions at the beginning of class. When a suitable amount of time has passed, review the questions as a class. 

1.	Why is DDT harmful? What effect of DDT (DDE) is linked to the slow decline of birds of prey in the United States during the late 1960s and early 1970s?

DDT breaks down in the body of animals to become DDE. DDE tends to stay in the body and at high concentrations can result in nervous system damage, immune system problems, thyroid problems, eggshell thinning and death. The slow decline of birds of prey in the US mostly reflects the effect of eggshell thinning caused by DDE bioaccumulation in female birds. Thin eggs tend to break before embryos can fully develop and hatch.

2. 	Does DDE accumulate in all species equally? Why not? What type of species is most likely to accumulate large amount of DDE due to biomagnification?

No, DDE does not accumulate in all species evenly. Consumers that are high in the food chain such as tertiary consumers are likely to accumulate a lot of DDE due to biomagnification. In order to meet their caloric requirements, tertiary consumers eat a lot of organisms that have small concentrations of DDE in their bodies. These small doses add up to high concentrations of DDE in the bodies of tertiary consumers. In addition, since DDT gets washed off into streams, rivers and the ocean, animals that feed on water-dwelling creatures tend to accumulate more DDE than animals that feed on terrestrial animals. (Unless the terrestrial animals they feed on are consumers that largely feed on aquatic animals.)

3.	When was DDT banned?

DDT was banned in 1972.

## Was the DDT ban effective in reducing the DDE concentrations in wildlife?

***Was the DDT ban effective in reducing the DDE concentrations in wildlife?***

**Notes:**
We can use data to determine if DDE concentrations in wildlife decreased after the DDT ban was passed. Through the years scientists have collected a great deal of data on contaminants in wildlife. Much of this data is easily accessible to the public through databases on the internet. 

## Slide 3

**Notes:**
Contaminants and Vertebrates Online provides different types of information about contaminants in animals. One of the components of Contaminants and Vertebrates Online is CEETV, a Contaminants Exposure and Effects-Terrestrial Vertebrates database that people can search on through the Internet to get data concerning contaminants and/or species they are interested in.

## Contains data concerning contaminants in mammals, birds, amphibians and reptiles that live near coastline or estuaries in the United States.

**Contains data concerning contaminants in mammals, birds, amphibians and reptiles that live near coastline or estuaries in the United States.**
**Created by scientists working for the Biological Resources Division of the U.S. Geological Survey, a part of the Department of the Interior of the United States Government. **
**Data in CEETV is mostly from articles published in peer-reviewed journals. Some data are from government reports and government websites. **

**Notes:**
The Contaminants Exposure and Effects Database-Terrestrial Vertebrates or CEE-TV (www.pwrc.usgs.gov/ceetv) stores data about contaminants in mammals, birds, amphibians and reptiles that live near coastline or estuaries in the US. The CEE-TV database was created by scientists working for the Biological Resources Division of the U.S. Geological Survey (USGS). USGS is a part of the Department of the Interior of the federal government. The mission of the Biological Resources Division is “to work with others to provide the scientific understanding and technologies needed to support the sound management and conservation of our Nation's biological resources”. CEE-TV contains data gathered by hundreds of different scientists throughout the 20th and 21st centuries that has been published in peer-reviewed journals, government reports and on government websites. We are going to use data from CEE-TV to investigate whether the DDT ban has been effective in reducing DDE concentrations in wildlife.

 1. From where will we get data to investigate whether the DDT ban was effective in 
reducing DDE concentrations in wildlife?

 2.  Who created this database? Why might they be interested in contaminants?

 3. Where did the data in the database come from? Do you trust this source of data to 
be	fairly non-biased? Why or why not?

## There is a lot of data in CEETV, over 11,000 records on more than 400 species. 

***What data do we need to examine if the DDT ban was effective?***

***What type of species should we investigate? ***

**Notes:**
 4. 	What type of species should we investigate? Why?

A TERTIARY CONSUMER. Due to biomagnification, tertiary consumers will accumulate the most DDE in their bodies. Small amounts of DDE in organisms lower in the food web might still accumulate to dangerous concentrations in a tertiary consumer. In order for the ban to be considered effective, the biomagnification of DDE needs to decrease significantly. That is, DDE concentrations in tertiary consumers need to decrease below the adverse effect level.

Ask students to give some examples of tertiary consumers such as bears, mountain lions, eagles, hawks, etc.

## What factors should we consider before selecting a tertiary consumer to investigate?

***Do all tertiary consumers have the same likelihood of accumulating high concentrations of DDE?****** ***
***2. ******	******Can we combine species or do we need to pick one?****** ***
***3. ******	******How much data is available?***
*	**	**	**	*

**Notes:**
How do we choose? Discuss the following questions
 5. 	Do all tertiary consumers have the same likelihood of accumulating high concentrations of DDE?

No, as noted in lesson 2 and in today’s opening questions, DDT runs off into the water and consumers that eat mostly water-dwelling organisms tend to accumulate higher concentrations of DDE. Thus in order to focus on the most sensitive species, we should pick a tertiary consumer that feeds mostly on water-dwelling animals.

 6.  Can we combine species or do we need to pick one? Why?

Species do not necessarily accumulate DDE in the same way due to differences in the type of animals they eat and physiological differences that cause DDE to be processed differently. Some species will accumulate more or less DDE than other species even if fed the exact same food. Thus an 8 ug/g ww DDE concentration in one species may not be comparable to an 8 ug/g ww concentration in another species. In order to insure we are comparing data in a non-biased manner we should pick only one species.

* You may want to follow this question up with “What kind of bias would we be introducing if we combine data for different species?”  Sample selection bias

 7.  What other factor effects our choice of species since we are getting our data from an existing database?

We are not collecting data ourselves but relying on data that has been collected by others. Thus, we not only need to pick a tertiary consumer that feeds mostly on water-dwelling animals but also one for which a lot of DDE data has been collected so we can have a large sample size to minimize bias. Some species are more difficult to study than other species either because they are protected or difficult to capture or only found in very remote locations.

One of the species that meets these requirements is the bald eagle. Tell students that they will be given subset of the CEE-TV database in order to investigate the effectiveness of the DDT ban. Their dataset will only contain data for DDE concentrations in bald eagles in the U.S. First, in order to prepare, the class will review an example using ospreys.

## CEETV Data for DDE in Ospreys

- We have data on DDE concentrations in osprey eggs collected from various locations in the U.S. between 1968 and 1991. What question do we want to ask?
-  What is our hypothesis?

**Hypothesis:**** **In the two decades following the 1972 banning of DDT,** **DDE concentrations in osprey eggs did not consistently decrease in the United States below a harmful concentration(< 3ug/g ww).* *

**Our investigation is clearly defined:**
**Species:**** ****Osprey**
**Matrix (body part): ****Egg contents**
**Location: ****United States**
**Harmful concentration of DDE: **_**>**_** 3 ug/g ww**
**Time frame: ****DDE concentrations < 3 ug/g ww by 1992**

**Notes:**
 8. We have data on DDE concentrations in Osprey eggs collected from various locations in the U.S. between 1968 and 1991. What question do we want to ask? What is our hypothesis?

Recall from Lesson 1, science attempts to disprove things. A hypothesis is always formulated as a null hypothesis. In this case our null hypothesis is “DDE concentrations in Osprey eggs in the United States were not consistently below the adverse effect level (< 3 ug/g ww) in the two decades following the DDT ban in 1972.”

 9. With this hypothesis, how have we specifically defined our investigation?

	With this hypothesis we have clearly defined our investigation in the following ways:
		Species: Osprey
		Matrix (body part): egg contents
		Location: United States
		DDE adverse effect concentration: >3 ug/g ww
		Time frame: DDE concentrations < 3 ug/g ww by 1992

## We are going to investigate our hypothesis by graphing DDE concentrations in osprey eggs collected in the U.S. by year. 

***What do we expect the graph to look like if the hypothesis is supported?****** ***

***What do we expect the graph to look like if the hypothesis is rejected?****** ***

**Notes:**
We are going to investigate our hypothesis by graphing DDE concentrations in Osprey eggs collected in the U.S. by year. 
 10. What do we expect a graph of DDE concentrations in Osprey eggs collected in the U.S. by year to look like if the hypothesis is true?

*Click with mouse and graph examples will appear one at a time, 1 graph per click. 

	No consistent pattern, no decrease, or an increase.

*Click with mouse and next question will appear.

 11. What do we expect a graph of DDE concentrations in Osprey eggs collected in the U.S. by 
year to look like if the hypothesis is false?

*Click with mouse and graph will appear.

	Consistent decrease with time with DDE < 3 ug/g ww by 1992 

## Slide 9

**Notes:**
This is a slide of raw data. This is what the bald eagle data that students will be working with will look like when they first get it. 

## Individual data records 

**Groups based on year**

**Average DDE concentration for each group **

**Notes:**
The computer program, Excel, is used to sort the individual data records into groups by year. We then use Excel to calculate an average DDE egg content concentration for each group.

 12. What steps need to be taken to transform the individual records into DDE averages that can be graphed?

## Average DDE concentration for = each group 

**Sum of DDE concentrations of all individuals in the group**
**Total number of individuals in the group**

**Average DDE concentration for ****=**** each group **

**Notes:**
The average DDE egg content concentration for each group is calculated by dividing the sum of the DDE concentrations for every individual by the number of individuals. Stress the need to account for every individual since this is a question that will come up during Bald Eagle Activity 1. 

 13. How is the average DDE concentration for a group calculated?

## DDE (ug/g ww average concentration) 

**in Osprey eggs by Year**

**Notes:**
We end up with a table of DDE average egg concentration by year group. We can then use Excel to make a graph of these averages. 

## Slide 13

**Notes:**
And here it is, our graph. 

 14. What did the graph of the Osprey data look like? What was the highest average 
concentration of DDE found in Osprey eggs and during what time period was this high found?

With the graph displayed, discuss the following questions:

 15. Have we disproved our hypothesis?  What is our conclusion?

YES. Our conclusion is that DDE concentrations in Osprey eggs in the United States consistently decreased below the adverse effect concentrations (< 3 ug/g ww) in the two decades following the DDT ban in 1972.

 16. How long did it take for DDE to decrease below adverse effect concentrations (< 3 ug/g ww)?

		Around 9 years

 17. Was the DDT ban effective in decreasing DDE concentrations in wildlife in the United 
       States?

We cannot answer this question. Our results are limited to our hypothesis that concerns DDE concentrations in Osprey eggs. Moreover, if we wanted to be truly accurate we would not say in the U.S. but along coast and estuaries in the U.S. since the data contained in CEE-TV are limited to these regions. Now lets explore the effectiveness of the DDT ban further by looking at another data set, DDE in bald eagle eggs.

## The bald eagle, our National Bird and a symbol of freedom is also very sensitive to DDE!  Adverse reproductive effects begin to occur when concentrations in bald eagle eggs reach about 3ug/g.