1 of 13© boardworks ltd 2009. 2 of 13© boardworks ltd 2009 life on earth depends on three...

1 of 13 © Boardworks Ltd 2009


Life on Earth depends on three interconnected factors:

• The one-way flow of high quality energy

sun living things (feeding interactions) environment (low quality energy) back into space as (infrared radiation - heat).

• Cycling of matter or nutrients through parts of the biosphere.

• Gravity which allows the planet to hold on to its atmosphere and causes the downward movement of chemical in the matter cycles.


Vocabulary to begin..

Abiotic – non-living

• Biotic – living


More Vocabulary…

• Levels of biological organization

• Figure 4.1 page 65

• Mini-glossary

page 64


More Vocabulary…

• Ecology – the study of interactions among organisms and between organisms and their abiotic environment.


Earth’s Four Realms

• Hydrosphere – Earth’s supply of water liquid and frozen, fresh and salty

• Atmosphere – gaseous envelope surrounding the earth

• Lithosphere – soil and rock of Earth’s crust

• Biosphere – all living organisms


Let’s Practice What is the word for…

• A group of individuals of the same species that occupy a common area.

• The unique environment that organisms are best adapted to energy resources.

• One individual living thing.• Where an organism lives.• A group of organisms that are able to

produce fertile offspring.


Let’s PracticeWhat is the word for…

• A physically distinct, self-supporting unit of interacting organisms and their environment.

• Means living.

• A group of interacting populations of different species

• Means non-living.


Energy Quality is..

The measure of an energy sources’ ability to do useful work

• Entropy: a measure of disorder or randomness of a system


Two Laws of Energy

• 1st Law of Thermodynamics – Energy is neither created or destroyed but can be transformed from one form to another.

• 2nd Law of Thermodynamics – Whenever energy is converted from one form to another, some usable energy (energy available to do work) is degraded into heat (a less usable form that disperses into the environment.)

*** Because of this, the amount of usable energy available to do work decreases over time.


Energy flow through ecosystems

Energy flows through an ecosystem, being transferred from one organism to the next.

Energy cannot be created or destroyed, only changed from

one form to another.

When energy is converted from one form to another, some is always lost as heat. This inefficiency of transfer limits the number of organisms found in any food chain.

Energy flows in one direction, obeying the law of conservation of energy.


Closed vs. Open System

• The earth is an open system for energy. We receive energy from the sun and heat energy is released back into the universe. We exchange energy with our surroundings.

• The earth is a closed system for matter. Matter is never created or destroyed. All matter that is here has always been here.

Are you breathing the same oxygen atoms the dinosaurs breathed???


Types of Energy Quality

• High quality: organized or concentrated and can perform much useful work.

• Examples…

electricity nuclear energy solar energy


Types of Energy Quality

• Low quality: disorganized or dispersed and has little ability to do useful work.

• Example…

heat in

the ocean


Forms of Energy

Potential vs. Kinetic

stored energy vs. energy of motion

• Units

kilojoules, kJ unit of work

kilocalories, kcal unit of heat


Example…

• When a car is driven, only about 20% of the high-quality energy available in its gasoline fuel is converted into mechanical energy (to propel the vehicle) and electrical energy (to run its electrical systems). The remaining 80% is degraded to low-quality heat that is released into the environment and eventually lost into space.


Example…

• When electrical energy flows through filament wires in an incandescent light bulb, it is changed into about 5% useful light and 95% low-quality heat that flows into the environment. In other words, this so called light bulb is really a heat bulb.


Energy Efficiency

• A measure of how much useful work is accomplished by a particular input of energy into a system.

• • ENERGY CAN NEVER BE RECYCLED OR

REUSED. IT IS ALWAYS TRANSFORMED FROM HIGH QUALITY TO LOW QUALITY ENERGY


Let’s Practice…

• Give an example of entropy.

• Energy quality is a measure of an energy sources’ ability to do useful work. What is the difference in high quality energy and low quality energy? Give an example.

• What are three interconnected factors that life on Earth depends?


Let’s Practice

• State the 1st and 2nd Laws of Energy (thermodynamics).

• Someone wants you to invest money in an automobile engine that will produce more energy than the energy in the fuel (such as gasoline or electricity) you use to run the motor. What is your response? Explain.


Let’s Practice…

• Use the 2nd energy law to explain why a barrel of oil can be used as a fuel only once?

• Why do you continuously need to eat food?


Vocabulary to know..

• Photosynthesis -

• Cellular respiration

• Hydrothermal vents


Obtaining energy


Energy availability in photoautotrophs


Primary production


Ecosystem examples

Net primary productivity (NPP) is a good way to compare different ecosystems. The availability of light, water and nutrients are different around the world and therefore the productivity of the world’s ecosystems also varies greatly.

desert ecosystem NPP =

260 kJm-2 year-1

tropical rainforest ecosystem NPP =

400,000 kJm-2 year-1


Ordering NPP of ecosystems


Routes of energy transfer

The organism is consumed by a primary, secondary or tertiary consumer.

Death, production of urine and feces and loss of organic tissue (e.g. fruit fall, hair loss) allows the energy from the organism to be passed on to decomposers.

The net primary productivity represents the potential food available to consumers in the ecosystem. This energy can be transferred to the next trophic level in several ways:


What is trophic efficiency?

The rate at which energy is used to make new organic molecules within heterotrophs is known as secondary production.

As with the transfer of energy from the sun to autotrophs, the transfer of energy from one organism to another is inefficient. The efficiency of chemical potential energy transferred between trophic levels can be measured.

The energy available is usually measured in kilojoules per square meter per year (kJm-2 year-1).

efficiency energy available after the transfer

energy available before the transfer= × 100


Loss of energy between trophic levels?

A large percentage of the energy is lost between trophic levels.This is as a result of the following:

Some of the organism cannot be eaten, e.g. bones, fur, etc.

Once eaten, some of the organism cannot be digested.

Energy is lost in excretory materials, such as urine.

Energy is lost in the form of heat from respiration and body heat.


Comparing trophic efficiencies


Efficiency of transfers in a food chain


Energy transfer: true or false?


Hydrothermal Vents

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