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.