ECOSYSTEMS PART 6

Bioaccumulation and Biomagnification

VOCABULARY

PesticideKills pests

InsecticideKills insects

HerbicideKills plants

TROPHIC LEVELS REMINDER

A category of organisms defined by how they get energy.

Primary Producers – plants Primary Consumers – herbivores Secondary Consumers – carnivores Tertiary Consumers – top carnivores

BIOACCUMULATION

When toxins are ingested by an organism faster than they are eliminated. The toxins build up in the tissues of the

organism.

BIOMAGNIFICATION

The increase in the concentration of a toxin as it moves from one trophic level to the next. Greatest problem is at the top of the food

chain.Example: plankton squid fist dolphins

The dolphins would have the greatest concentration of toxins.

EXAMPLE

grass mice fox wolf bear

Each wolf eats hundreds of foxes Each fox eats thousands of mice Each mice eats pounds of grass

Therefore the bear ingests billions of doses of chemicals/toxins.

EXAMPLE

grass mice fox wolf bear

The grass starts with 2 units of toxins. The mice eats 100lbs of grass

200 units of toxins The fox eats 1000 mice

200,000 units of toxins The wolf eats 100 foxes

20,000,000 units of toxins

EXAMPLE – THE DDT STORY

The risks of using powerful pesticides in ecosystems first became widely known during the 1950s and 1960s: DDT was one of the first and most powerful insecticides developed. During World War II, it was used to control populations of insects (such as body lice, fleas, and mosquitoes) that can transmit deadly diseases to people. As a result, the rate of death from malaria, bubonic plague, typhus, and yellow fever fell dramatically. DDT was also used widely on crops to control damage caused by insect pests.

About ten years after the first use of DDT, signs of trouble appeared. Dead birds, fish, frogs, and other animals were found in areas that had been heavily sprayed with DDT. The fat in their bodies contained high levels of the insecticide. Harmless or beneficial insects, such as butterflies and honeybees, also started to disappear from areas that had been sprayed.

Numbers of hawks, eagles, and ospreys on farmlands across North America and Europe fell sharply during the 1950s and 1960s. Scientists discovered that DDT reduced the ability of these birds to produce normal eggshells. Affected birds laid eggs with thin shells that broke in the nest, so they were unable to produce the usual number of young. The adult birds had accumulated DDT in their bodies from the fish they ate.

Which organism would have the highest concentration of DDT?

EXAMPLE – AIR POLLUTION

Importing Air Pollution from ChinaCBC NewsSeptember 21, 2014

EXAMPLE – POLLUTION UP NORTH

Pollutants applied in fields, often in warmer climates & other pollutants in air (from burning fuel) evaporate (water cycle) to the atmosphere Return in rain, carried back up, return in rain Travel north towards the Arctic from wind currents

Cold locks them in – few plants, poor soil, less sunlight so these pollutants are not broken down Enter food chains = bioaccumulation, then

biomagnifications Breast milk toxins 9x higher in Inuit women Animal abnormalities (seals without hair, etc.)

THINK ABOUT IT...

What is the relationship between the trophic level of an organism and the concentration of toxins in its body?

In your own words, explain why animals at the top of a food chain are particularly at risk from poisons in the environment.