Before You Read
Everyday activities, such as driving or heating your home, often pollute
ecosystems. In your opinion, which human activity is the most harmful
to the environment? Explain. I believe that the most harmful human
activity is burning fossil fuels because they release a lot of carbons
in to the air.
1. Bioaccumulation is the gradual build-up of synthetic and organic chemicals in
living organisms.
2. Keystone species are species that can greatly affect population numbers and
the health of an ecosystem.
3. Bio magnification is the process in which chemicals not only accumulate but
become more concentrated at each tropic level in a food pyramid.
4. Even small concentrations of chemicals in producers and primary and
secondary consumers can build up to cause problems in higher trophic levels.
5. PCBs are synthetic chemicals that were widely used from the 1930s to the
1970s in industrial products.
6. Half-life is the time it takes for the amount of a chemical to decrease by half.
7. Persistent organic pollutants are carbon-containing compounds that remain
in water and soil for many years.
8. Chemical accumulation is measured in parts per million.
9. Heavy metals are metallic elements with a high density that are toxic to
organisms at low concentrations.
10. Three polluting heavy metals are lead, mercury, and cadmium.
.
11. Bioremediation is the use of living organisms to clean up chemical pollution
naturally, only faster, through biodegradation.
Chemical
Toxic organic chemicals
from red tide.
Effects on producers,
primary consumers,
and secondary
consumers
Effects calms, muscles
and oysters, bio
accumulates to levels
harmful to other
organisms
Effects on humans
If shellfish are eaten, it
can cause paralysis. This
can result in a serious
illness or even death
DDT
Lead
bio accumulates in fat
tissue and can
cause nervous system,
immune system, and
reproductive disorders
There are similar effects
of the human effects are
seen on fish and birds.
Cadmium
In fish, it is associated
with higher death rates
and lower reproduction
and growth rates.
Highly toxic to
earthworms
Mercury
Organisms also circulate
mercury through the food
chain. Some
bacteria in soils change
compounds such as
mercury sulfide into
methylmercury, a highly
toxic compound that
bioaccumulates in the
brain, heart, and kidneys
of vertebrates
bio accumulates in fat
tissue and can
cause nervous system,
immune system, and
reproductive disorders
anemia (a blood
condition), nervous
system damage,
sterility in men, low
fertility rates in women,
impaired
mental development, and
kidney failure
smoking, as tobacco
plants easily absorb the
metal (Figure 2.58).
Cadmium can
accumulate in lung
tissue, causing lung
diseases such as
cancer. Non-smokers
ingest cadmium mainly
through foods such as
mushrooms, shellfish,
fish, and seaweed.
Cadmium moves from
the
digestive system to the
liver and then to the
kidneys.
methylmercury is
absorbed during
digestion, then enters the
blood and is stored in the
brain. It affects nerve
cells, the heart, kidneys,
and lungs and
suppresses
the immune system
PCBs and the orca
1. What are PCBs? What is their full chemical name? PCBs were one of the
most widely used industrial products, but they are now banned. They
interfere with the normal functioning of the body’s immune system and
cause problems with reproduction. Their full chemical name is
Polychlorinated Byphenyls.
2. What were PCBs used for in the 1970s? They were used as industrial
products.
3. In North America, PCBs were banned in 1977. Explain why they are still
having an effect on organisms today. Because they stay in the environment
for a long time, and aquatic ecosystems especially are affected by them
4. Explain what happens to PCBs when they enter an orca’s body. They go into
the blubber.
5. How do orcas survive when salmon stocks are low? What effect does this
have on their survival? Orcas use their blubber for energy.
6. Draw a diagram to illustrate how biomagnification occurs in orcas.
Effects of bioaccumulation
on ecosystems
1.
2.
3.
4.
5.
6.
F
D
E
B
C
A
7. C
8. C
9. B
10. C
11. D
12. D