Trophic Efficiency p. 306

Review: Trophic Level: Feeding level of an organism in a food chain or web. a) Trophic level 1 = plants b) Trophic level 2 = herbivores c) Trophic level 3 = carnivores that eat the herbivores. d) Trophic level 4 = carnivores that eat other carnivores (usually the top carnivore)

Energy in an Ecosystem The quantity of energy that is transferred from one level to the next is about 10%.

Pyramid of Energy Measures the total chemical energy circulating between each trophic level. 10% of energy is passed on to the next trophic level.

Energy Pyramid

To feed more humans at once, it is more efficient to eat from shorter food chains. Grains → Humans Grains → Cow → Humans

Feeding Consumption of most North Americans Consumption of meat – comparing different countries

To Do: Notes Activity – From Land to Mouth

In Conclusion... Compared to animals, green plants produce more energy per unit per area of land. Most energy in ecosystems or agricultural land comes from plants. Also, less space is needed to produce plants than to produce animals

Video – “Meat” the Truth Maybe the future? Video – “Meat” the Future Discuss

Pesticides

What are they? A pesticide is a chemical substance used to prevent, kill or chase “pests”. There are different types of pesticides: - herbicides (used to kill weeds) - fungicides (used to kill fungus and prevent moulds) - rodenticides (used to kill small rodents or pesky animals).

Pesticide Transport Pesticides can be transported easily around the environment. Here are a couple of examples: Wind – especially if a plane releases pesticides on a field, it can be transported by the wind.

Hilltop run-off -pesticides can run-off into different places. Water – rivers, lakes, streams, can transport pesticides Animals – birds can transport pesticides by holding plants in their beaks and then dropping them into other areas. Migratory birds can also transport pesticides to different regions of the world.

Influence on the Environment The majority of chemical materials can influence the environment if they are toxic. How? Water – Pesticides contaminate water. It can affect fish and other aquatic organisms. Animals and Humans that also drink from the same water source can be affected.

Land: When pesticides enter the earth, they lower the quality of the soil. - Plants cannot retain water as well - The chemical agents in the pesticides can make plants smaller.

Plants and Animals – Pesticides can be very harmful to the environment because of a process known as Bioaccumulation.

Bioaccumulation Bioaccumulation is the process in which materials, especially toxins, are ingested by an organism at a rate greater than they are eliminated.

Biomagnification Biomagnification is a process that is related to bioaccumulation. It’s the increase in the concentration of a toxin as it moves from one trophic level to the next. Video – Biomagnification!

Biomagnification Example: DDT DDT - A threat to birds of prey

If pesticides continue to destroy species and ecosystems it could have a devastating effect on the Earth.

Solutions? Bio-pesticides – made from less harmful substances. (eco-friendly) There are products you can put on your plants that release a terrible odour that pests and insects do not like, so they don’t go near them.

Another solution is genetic engineering Another solution is genetic engineering. Scientists can change the genes of plants so that they discourage pests and insects from bothering them. Video - Testing Natural Pesticides

DDT and Biomagnification DDT Conflict - Video Activity – Biomagnification

Amoeba Sisters - Biomagnification and the Trouble with Toxins