What would we do without energy?

A. Energy = The ability to do workB. The Laws of Thermodynamics:1. First law of Thermodynamics: Conservation of energy- energy can change type, but

the total amount of energy present remains constant.

2. Second law of Thermodynamics: Entropy – all processes in the universe

tend toward greater disorder or lesser quality energy (heat!).

C. Energy is transformed from one form to another but remains constant in ecosystems.

D. The sun is the ultimate source of all the energy in an ecosystem. How is this solar energy first converted to biomass? Photosynthesis!

6CO2 + 6H2O + solar energy -- C6H12O6 + 6O2

E. So photosynthesis converts solar energy to stored chemical energy (glucose).

F. Producers, consumers, and decomposers use chemical energy stored in glucose and other organic compounds to fuel their life processes. In most cells, this energy is released by aerobic respiration.

Respiration Energy Conversion

G. Aerobic respiration uses oxygen to convert glucose to other forms of energy.

C6H12O6 + 6O2 6CO2 + 6H2O + energy

H. Some decomposers get the energy they need by breaking down glucose or other organic molecules in the ABSENCE of oxygen. This is called anaerobic respiration, or fermentation.

I. The end products of anaerobic respiration depend in part on the starting organic molecule, but can include:

CH4 (methane) Ethyl alcohol (C2H6O)

Acetic Acid (C2H4O2) and hydrogen sulfide (H2S)

J. So photosynthesis converts solar energy to stored chemical energy – only via plants. And all organisms use respiration to convert stored chemical energy into the energy they need for movement, growth, maintenance and repair.

II. Producers

A. Producers - Producers can make the nutrients they need to survive from the compounds in their environment.

1. Also called autotrophs (self feeders) In land ecosystems most producers are green plants

II. Producers

2. In aquatic ecosystems most are phytoplankton, also dinoflagelates and algae.

II. Producers

3. Most producers use sunlight to make food by photosynthesis.

6CO2 + 6H2O + energy -- C6H12O6 + 6O2

4. Though plants do most of the planet’sphotosynthesis, bacteria “invented” the process. Photosynthetic bacteria stillexist.

II. Producers

5.A few producers – mainly specialized bacteria- produce nutrients without using sunlight.

6. Chemosynthesis – heat is used to convert inorganic compounds (like sulfur) into nutrients.– Ex. Bacteria that live near hot vents on ocean

floorProducers… Yeah, Yeah,Yeah !

II. Producers

B. The amount or mass of living organic material (biomass) that a particular ecosystem can support is determined by the amount of solar energy captured and stored as chemical energy by the producers of an ecosystem.

C. Gross Primary Productivity (GPP) is the rate at which an ecosystem’s producers convert energy to biomass (OR solar energy to stored chemical energy).

D. GPP is usually measured in terms of energy production per unit area over a given time span, such as kilocalories per square meter per year (kcal/m2/yr)

II. Producers

E. To stay alive, grow, and reproduce, producers must use some of the chemical energy (aka glucose) they have stored in respiration.

F. The energy present in tissues for consumers to eat is called Net Primary Productivity.

II. Producers

G. Net primary productivity (NPP) is gross primary productivity – respiration.

NPP = GPP – R (R=Respiration).

NPP is the amount of energy available from producers for other organisms in the ecosystem.

II. Producers

H. Ecosystems differ vastly in their NPP. On land, NPP usually decreases as you travel from equator to pole because of the decreasing amount of solar radiation available.

I. In the ocean, the highest NPP is found in estuaries where high inputs of plant nutrients flow from stream run off.

J. Because of low nutrient availability, the open ocean has very low NPP, except in areas of upwelling.

K. In spite of low NPP, the open ocean produces more of the earth’s total biomass per year than any other ecosystem, simply because there is so much open ocean.

L. In total biomass, open ocean, tropical rain forest, and temperate forests produce the most per year. Tundra and desert are last.

M. When looking at biomass production per square meter, estuaries, swamps and marshes, and tropical rainforest produce the most. Open ocean and deserts are last.

III. ConsumersA. Consumers or heterotrophs get their nutrients from

feeding on the other organisms.

B. There are several classes of consumers depending on their food source.

Quetzal – Omnivore!

C. Herbivores- plant eaters, called primary consumers because they feed directly on other producers

1. Primary consumers in terrestrial ecosystems include most insects, many bird species (that feed on seeds or nectar), deer, rabbits

2. Primary consumers in aquatic ecosystems are zooplankton (microscopic heterotrophs that feed on phytoplankton.)

D. Carnivores – meat eaters, feed on other consumers

1.Secondary consumers are the organisms that eat the herbivores.

2.Terrestrial examples include spiders, insect eating birds, frogs, etc.

3.Aquatic examples include some fish or aquatic frogs.

4. Tertiary or higher-level consumers are carnivores that feed on the flesh of other carnivores.

5. Terrestrial examples include tigers, wolves, snakes, hawks

6. Aquatic examples include sharks and killer whales.

Jaguar – largest

Tertiary consumer

In Costa Rica.

E. Omnivores – Eat both plants and animals

1.Terrestrial examples – pigs, foxes, cockroaches, raccoons, bears

2.Aquatic examples – comb jellies (eat both phytoplankton and zooplankton), crabs, seagulls

Collared Peccary – lowland

Rainforest omnivore

F. Decomposers – Mostly certain types of bacteria and fungi. Break down waste and dead organisms with enzymes.

G. Detrivores – Feed on wastes or dead bodies.

1.Terrestrial examples – worms, some insects, vultures.

2.Aquatic examples - catfish

A. All organisms dead or alive are potential sources of food (energy) for other organisms.

B. 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.

C. Ecologists assign every organism in an ecosystem a feeding level or trophic level (from the Greek trophos, “nourishment”)

1. Producers belong to the first trophic level2. Primary consumers belong to the second

trophic level3. Secondary consumers belong to the third

trophic level.

D. In most ecosystems, organisms form a complex network of feeding relationships called a food web. Food chains only have one linear set of arrows, while a web has multiple arrows leaving from multiple organisms (ie. The energy from a producer can go to several different consumers)

E. Ecosystems are very complicated, food chains and food webs are only simplistic representations of existing relationships.

F. Biological Magnification1. The process where

pollutants such as pesticides or heavy metals move up the food chain

2. The substances become concentrated in tissues or internal organs as they move up the chain

             

G. 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!

                   

H. Practice problems

A simple food chain consists of grass, beetle, blue jay, and red-tailed hawk. A beetle eats 10 blades of grass a day, a blue jay eats 5 beetles a day, and the hawk eats 3 blue jays a day. If each blade of grass is sprayed with 2 grams of DDT, how many grams of DDT does (1) a red tailed hawk get per day? (2) Calculate a hawk’s monthly dose (assume 30 day month)

1) Answer

2 g DDT x 10 blades x 5 beetles x 3 blue jays

Blade 1 beetle 1 blue jay 1 hawk

1) Answer

2 g DDT x 10 blades x 5 beetles x 3 blue jays

Blade 1 beetle 1 blue jay 1 hawk

2 x 10 = 20

20 x 5 = 100

100 x 3 = 300 g DDT/hawk (each day)

2.) Answer

If a hawk consumes 300g DDT/day, and a month has 30 days, a hawk consumes

300 x 30 = 9,000 grams of DDT a month!

Eeek! Biomagnification is bad!

III. Energy Transfer in Food Webs

A. Each trophic level in a food chain or web contains a certain amount of biomass, the dry weight of all organic matter contained in its organisms.

B. In a food web, chemical energy stored in biomass is transferred from one trophic level to another.

C. Energy transfer through food chains and food webs is not very efficient because with each transfer some usable chemical energy is degraded and lost to the environment as low quality heat (aka second law of thermodynamics).

D. As energy flows through food webs, there is a decrease in the amount of chemical energy available to organisms at each succeeding feeding level.

E. The percentage of usable chemical energy transferred as biomass from one trophic level to the next is called ecological efficiency.

F. In nature, ecological efficiency varies from 2-40% depending on the ecosystem and organisms (so loss of 60 to 98% of usable chemical energy).

G. However, the generally accepted average is 10% ecological efficiency from one trophic level to the next (aka 10% of the usable energy is transferred up each step in the food chain).

Why only 10%

H. There are multiple reasons why ecological efficiency averages only 10%: Much energy is lost as heat, energy is needed and used for organisms metabolism, not making biomass, not all biomass is eaten by the next trophic level (roots, fur bones) or may be indigestible and excreted as waste (tree bark).

IV. Ecological Pyramids

A. Pyramid of Numbers – by counting the number of organisms at each trophic level, ecologists can graph this information to yield a pyramid of numbers.

B. 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

C. Biomass Pyramid – You can also calculate the biomass of each trophic level in a food chain. Usually done by looking at one or several top consumers in an ecosystem and working backwards to get biomass estimates for lower trophic levels (like we did with the owl).

D. Pyramid of energy flow

1. The percentage of useable energy transferred from one trophic level to the next can be shown with raw energy numbers (usually in kilocalories).

2. The pyramid of energy flow shoes that the more trophic levels in a food chain or web, the greater the loss of useable energy.

3. The large loss of chemical energy between trophic levels explains why food chains rarely have more than four or five trophic levels. In most cases, too little chemical energy is left to support organisms feeding at these trophic levels.

E. Practice Problems: A simple food chain consists of grass, grasshopper, toad, and owl. If the grass has 10,000 kilocalories of energy stored in its biomass, how much:

1)Energy is available in the grasshopper trophic level?

2)Energy is available in the owl trophic level?

1. AnswerAlways assume 10% of the energy available in any

trophic level can pass to the next level. 10% of 10,000 is 1,000

or .1 x 10,000 = 1,000.

(Big math hint: For

10% of a number, move

decimal one to the

right!)

Grasshopper = 1,000 kcal

Grass = 10,000 kcal

2. For upper trophic levels, you must find 10% of each level to get the final level. Aka move the decimal 1 to the right for each trophic level you go up from the starting place. 3 levels, move the decimal 3 places to the right.

Grasshopper = 1,000 kcal

Grass = 10,000 kcal

Toad= 100 kcal

Owl= 10 kcal

F. The energy flow pyramid explains why the earth can support more people if they eat at lower trophic levels.

G. This also explains why top carnivores (sharks, eagles, tigers) are the first to suffer when the ecosystems that support them are disrupted.