Bio Ch. 1 - Energy Flow Through the Biosphere

Heavy Metals

• Mercury, Copper, Cadmium, Chromium, Lead, Nickel, Zinc, Tin

• mercury from gold mining
• many from metal processing
• may affect nervous system
• may affect reproduction

Cyanide

• used in leaching of gold
• used in fishing
• toxic

Ecological Pyramids

Ecological pyramids represent the distribution of energy in an ecosystem.

They exist in three types:

Pyramid of Numbers

This represents the number of organisms that occupy each trophic level

Advantaged & Disadvantages of the Pyramids

Pyramids of numbers & biomass can sometimes be inverted be to certain situations within ecosystems.

These inverted pyramids then lose their ability to accurately represent the passage of energy from one trophic level to the next.

Pyramid of Biomass

Pyramid of Energy

Biomass is the dry mass of living organisms per unit of area. The pyramid of bio indicates the biomass present at each trophic level in an ecosystem.

The Inverted Numbers Pyramid

A pyramid of energy represents the amount of energy that is transferred through each trophic level.

This inversion occurs when we have a large number of primary consumers feeding on a single producer. There are a few cases where this will occur:

Consequences of the Laws:

As a result, we lose energy as it is passed along a food chain.

As a general rule, less than 10% of the energy that is present at one level is passed on to the next.

This will limit the number of tropic levels in an ecosystem to five or fewer.

Energy Transfer Between Trophic Levels

Food Chains & Webs

Most food chains have very few trophic levels. The amount of energy transferred from one level to the next ranges from 5-20 percent. The remaining energy is not passed on because it is not stored in tissues.

As a general rule we can consider that, on average, only 10% of energy at each level is passed on to the next level ( the "rule of 10")

• Food Webs show connections between different food chains

A food chain is a model showing linear pathway through which energy moves in ecosystems.

Chemosynthetic Organisms

Other types of bacteria that carry out chemosynthesis have been found in other environments. We now know that these organisms live in the cold ocean, in hot springs, salty lakes, deep caves, and even in soil

Energy in the Biosphere

Decomposers

Decomposers play an important role in ecosystems. Without them, the nutrients trapped in the bodies of dead organisms would not be released. Therefore, you can think of decomposers nature's recyclers.

Consumers

Earth can be considered a closed system. The energy that the Earth receives does not cycle like matter does.

We are bound by the First & Second Laws of Thermodynamics:

Law of Thermodynamics:

1st: Matter cannot be creates nor destroyed. Only can be converted from one form to another

2nd: If matter is converted from one form to another energy is lost

Consumers cannot capture the sun's energy directly. Therefore, they must feed on producers

Levels of Consumers

Primary consumers (herbivores) eat producers

Secondary consumers (carnivores) eat mainly herbivores

Tertiary consumers are organisms that feed on other carnivores

Occasionally, there are higher order consumers

How Energy Enters the Biosphere

Chemosynthesis

Organisms that live in areas without life (such as the deepest parts of the ocean) not perform photosynthesis. Near deep-sea vents in the ocean, specialized bacteria split hydrogen sulfide molecules that come out of the vents. They use the energy obtained from breaking the chemical bonds to create energy-storing compounds.

One of the requirements of all living things is energy. All organisms use cellular respiration to obtain energy from chemical compounds. These chemical compound are produced by organisms known as producers

Photosynthesis & Solar Energy

Photosynthesis

Photosynthesis is carried out by producers such as plants, algae & some bacterias.

The process of photosynthesis is often written as:

The Earth receives large amounts of energy from the sun. However, very little of that energy is used for photosynthesis:

30% is reflected from the clouds and atmosphere

19% is absorbed by the atmosphere and clouds

Of the remaining energy that reaches the ground, only 1-2% is used to drive photosynthesis

Energy Flow Through the Biosphere - BIO Chapter 1

Bioaccumulation & Biomagnification

BioAccumulation:

The increase in concentration of a substance in an organism over time (taken in & stored faster then they are broken down)

Biomagnification:

The increase in concentration of a pollution from one link in the food chain to another

Properties of substances that bioaccumulate

• the substance must be:
• long lived
• mobile
• fat soluble (typically)
• biologically active

Can you think of a situation where bioaccumulation is positive?

A classic example: DDT

• DDT - dichloro - dipheny - trichloraethane (chlorinated hydrocarbon)
• It has a half-life of 15 years - that means 100kg of DDT is used it will break down as follows

Year Amount Remaining

0 100kg

15 50kg

30 25kg

• DDT has rather low toxicity to humans
• But :
• high toxicity to insects
• if accidentally swallowed in large amounts, it can cause a person to become excitable, have tremors & seizures
• In animals, harmful effects in reproduction & in the nervous system
• cause shell-thinking birds, in particular varnivores birds (raptors) such as ospreys & bald eagles

The Inverted Biomass Pyramid

Oceans ecosystems may show an inverted biomass pyramid as the producers (phytoplankton) make up much less biomass than the zoo plankton that feed on them.

Keep in mind, though that the phytoplankton transfer a larger amount of energy per kg of mass to the zoo plankton.

Energy Transfer & The Stability of Ecosystems

Comparing different Biomass Pyramids

As our climate changes, so will the distribution of organisms in our ecosystem. If organisms at the bottom of these ecological pyramids are affected, then those changes will be passed on through the food chain.

If an ecosystem has fewer & less varied producers, then the food wens in this ecosystem will change, resulting in more fragile ecosystem.

Pyramids of energy will always be upright. This is because these types of pyramids only represent the energy that is transferred through each trophic level

Disadvantages of the Pyramid of Energy

To develop a pyramid of energy, we must know how much energy is contained in the tissue at each trophic level.

To do this, we must use calorimetry.

In this process, a sample of material is burned to determine how much energy it contains.

Therefore, it is very time consuming to determine values for a pyramid of energy.