Friday Aug 30/Monday Sept 3 Turning in supplies? Place AGENDA Grade Homework Notes: Energy Flow in Ecosystems Lab Safety Review QUIZ: Lab Safety Desert Food Web Activity (Homework if not finished) HOMEWORK Food Chains and Food Webs Pyramids of Ecology

What would we do without energy?

Energy = The ability to do work The Laws of Thermodynamics: 1. Conservation of energy- energy can change type, but the total amount of energy present remains constant. 2. Energy is transformed from one form to another but remains constant in ecosystems.

What is the main energy source for life on earth? The sun

Sometimes called autotrophs (self feeders). Producers can make the nutrients they need to survive from the compounds in their environment. In land ecosystems most producers are green plants.

In aquatic ecosystems most producers are algae or phytoplankton.

Most producers use sunlight to make food by photosynthesis. 6CO 2 + 6H 2 O + energy --  C 6 H 12 O 6 + O 2 Though plants do most of the planet’s photosynthesis, bacteria invented the process. Photosynthetic bacteria still exist.

A few producers – mainly specialized bacteria- produce nutrients without using sunlight. Chemosynthesis – heat is used to convert inorganic compounds into nutrients. –Ex. Bacteria that live near hot vents on the ocean floor. Producers… Yeah, Yeah,Yeah !

Consumers or heterotrophs get their nutrients from feeding on the other organisms.

There are several classes of consumers depending on their food source. Herbivores- plant eaters, called primary consumers because they feed directly on other producers.

Carnivores – meat eaters, feed on other consumers Omnivores – eat both plants and animals

Decomposers – break down organic matter. Example – bacteria and fungi. Detrivores – organisms that feed on dead matter or detritus. Example- snails, earthworms.

All organisms dead or alive are potential sources of food (energy) for other organisms –The sequence of who eats or decomposes whom in an ecosystem is called a food chain. It illustrates how energy moves from one organism to another through the ecosystem.

Ecologists assign every organism in an ecosystem a feeding level or trophic level (from the Greek word trophos, “nourishment”) producers belong to the first trophic level primary consumers belong to the second trophic level secondary consumers belong to the third trophic level.

Trophic Levels

In most ecosystems, organisms form a complex network of feeding relationships called a food web. Ecosystems are very complicated, food chains and food webs are only simplistic representations of existing relationships.

There are three ways to show the relative amounts of energy or matter contained within each trophic level. 1.Pyramid of numbers 2.Energy Flow pyramid 3.Biomass pyramid

1.Pyramid of Numbers – by counting the organisms at each trophic level, ecologists can graph this information to yield a pyramid of numbers. Since the typical ecological structure is many producers, not as many primary consumers, and just a few secondary consumers, the graph usually looks like a pyramid.

Pyramid of Numbers

2. The energy flow pyramid explains why the earth can support more people if they eat at lower trophic levels. This also explains why top carnivores (sharks, eagles, tigers) are the first to suffer when the ecosystems that support them are disrupted.

Pyramid of energy flow: The percentage of useable energy transferred from one trophic level to the next is about 10%. Organisms use the energy they consume for respiration, reproduction and movement. The pyramid of energy flow shows that the more trophic levels in a food chain or web, the greater the loss of useable energy. Energy is lost to the atmosphere as heat.

10% of the available energy is transferred to the next trophic level. Energy flows in one direction only. It is not recycled!!

3. Biomass Pyramid- Represents the amount of potential food available for each level in an ecosystem. Biomass is usually expressed in terms of grams of living organic matter per unit area.

Not all pyramids are shaped like pyramids!!!

Biological Magnification The process where pollutants such as pesticides or heavy metals move up the food chain. Pollutants can be non-bio- degradable which means they cannot be broken down by the metabolism of the organism. The substances or pollutants become concentrated in their toxic form in the tissues or internal organs of the organisms as they move up the food chain.

This happens because when larger animals eat smaller animals or prey, they don't just eat one or two of these animals during their lifetime, sometimes they eat thousands or millions. Not only are these animals ingesting their prey, they're also ingesting all of their prey's toxins!