1. Ecology

2. Energy Flow in an Ecosystem
Trophic Levels
Ecologists use food chains & food webs to model the flow of energy through an ecosystem
Each feeding level within a food chain/web = Trophic level
3 Major Trophic Levels
1. Producers
Plants, Plankton, Algae
Make organic material from inorganic material
Sunlight, carbon, oxygen, nitrates, water

3. Energy Flow in an Ecosystem
Remaining Trophic Levels
2. Consumers
Get organic material from other living tissues
3 Types:
Herbivore:
Eats only producers
Ex: Cow, grasshopper, rabbit
Carnivore:
Preys on other heterotrophs
Ex: Wolves, lion
Omnivore*
Eats both plants & animals
Ex: Bears, humans, mockingbirds

4. Energy Flow in an Ecosystem
Remaining Trophic Levels
3. Decomposers
Fungi (mushrooms), bacteria
Breakdown dead organic material and returns inorganic material back to the soil

5. Invasive Species Asian Long Horned Beetle Sighted in Worcester, MA
Kills trees
Popular, Willow, Elm
Beetle reproduces inside the tree
Larvae tunnel through and eat the tree
Tree crumbles
Native to Asia/Japan where there is a natural predator
Has no natural predator in the United States

6. Invasive Species
Asian Long Horned Beetle

7. Invasive Species Snakehead Fish Native to Asia
Many different species of the Snake Head Fish
Some are huge and very aggressive
Get caught in fish nets  Attack fisherman
Sold as pets in the United States
Pet stores started purchasing smaller versions of this fish
People who could not keep them  dumped them into ponds
No predator in the United States
Eat everything that lives in a pond (top of the food chain)
Deplete entire food source within the pond and then MoVe on to another pond
Shimmy across land  primitive lung (in addition to gills)

8. Invasive Species Snakehead Fish Evolutionary Advantage
Can breath oxygen
Within the air (primitive lung) AND
Within the water (gills)
Swim and move across land

9. Invasive Species
Snakehead Fish

10. Pollution Pollution Threatens biodiversity and global stability
Changes the composition of air, soil, & water
Many types…
Human-made chemicals, not found in nature, are being discovered in food webs
Pesticides  DDT (dichloro-diphenyl-trichloroethane)
Industrial chemicals  PCBs (polychlorinated biphenyls)
These substances are ingested by organisms when they drink water or eat other organisms that contain the toxic substance
Some substances are metabolized by the organism and excreted with other waste products
However, DDT and PCBs, accumulate in the tissues of organisms

11. Biological Magnification
Biomagnification:
Increasing concentration of toxic substances in organisms as trophic levels increase in a food chain/web
Carnivores at the higher trophic levels seem to be most affected
Examples of toxic substances accumulating in food webs:
DDT
Mercury
PCBs
Concentration of the toxic substance is relatively low when it enters the food web
Concentration of toxic substance in individual organisms increases as it spreads to higher trophic levels

12. DDT Highly effective pesticide
Used from the 1940s to the 1970s to control crop-eating and disease-carrying insects
However, it caused the eggshells of fish-eating birds to be fragile and thin  death of the developing birds
May have played a role in the near extinction of the bald eagle & peregrine falcon
Once these toxic effected were discovered, the use of DDT was banned in some parts of the world

13. Mercury Heavy metal found in the ocean
Water  Algae  Bigger Fish (Tuna, swordfish)  Human
Pregnant women should not eat tuna or swordfish due to the accumulation of the mercury in these fish
Link between autism & mercury

14. PCBs Manufactured from 1929 until banned in 1979 Range of toxicity
Cancer
Adverse health effects on the immune, reproductive, nervous, & endocrine systems
Hundreds of industrial & commercial applications
Electrical
Heat transfer
Hydraulic equipment
Plasticizers in paints, plastics, & rubber products
PCBs can accumulate in the leaves and above-ground parts of plants and food crops. They are also taken up into the bodies of small organisms and fish. As a result, people who ingest fish may be exposed to PCBs that have bioaccumulated in the fish they are ingesting

15. Eutrophication Another form of water pollution
Destroys underwater habitats for fish and other species
Fertilizers, animal waste, sewage (rich in nitrogen & phosphorus) flow into waterways
Resulting in extensive algae growth
Algae use up the oxygen supply during their rapid growth & after their deaths during the decaying process
No oxygen in the water = other organisms in the water suffocate