Chapter 4

Chapter 4

The Energy of Life

How Matter and Energy Enter Living Systems

Part 1

• The ultimate source for most of the energy for life is the sun.

• Photosynthesis: The process in which an organism uses the sun’s energy to manufacture food.

PhotosynthesisPhotosynthesis

ChemosynthesisChemosynthesis• Chemosynthesis: the process of using

chemicals to create food

• Similar to photosynthesis, because it produces carbohydrates, but uses chemical energy instead of light energy.

Cellular RespirationCellular Respiration• Respiration: The process of releasing energy

from carbohydrates to perform the functions of life.

• Used by all living things

Photosynthesis and RespirationPhotosynthesis and Respiration

The producers: AutotrophsThe producers: Autotrophs

• Autotroph: An organism that uses light energy (photosynthesis) or energy stored in chemical compounds (chemosynthesis) to make food

• Heterotroph: An organism that cannot make its own food and feeds on other organisms

The consumers: HeterotrophsThe consumers: Heterotrophs

The consumers: HeterotrophsThe consumers: Heterotrophs

• Herbivore: A heterotroph that feeds only on autotrophs

• Heterotrophs display a variety of feeding relationships.

The consumers: HeterotrophsThe consumers: Heterotrophs

• Carnivores: heterotrophs that eat other heterotrophs.

• This great white shark is an example.

The consumers: HeterotrophsThe consumers: Heterotrophs• Scavengers: eat organisms that have already

died.

• This hardhead catfish is a good example of a scavenger that is native to the Alabama Gulf Coast.

The consumers: HeterotrophsThe consumers: Heterotrophs

• Decomposer: An organism that feeds on and breaks down dead plant or animal matter, thus recycling nutrients in the ecosystem.

The Ocean’s Primary Productivity

Part 2

Primary ProductionPrimary Production

• Primary production: the creation of energy-rich compounds (carbohydrates) by autotrophs

• Carbohydrate: the primary energy storage molecule for living organisms.

• Primary production is measured in terms of the amount of carbon that is fixed into organic material per square meter of surface area per year. (gC/m2/yr)

Marine BiomassMarine Biomass

• Biomass is the total mass of living matter at each trophic level.

• A pyramid of biomass represents the total weight of living material available at each trophic level.

• Standing Crop: the biomass of producers at a given time.

Pyramid of Biomass

1 kilogram of human tissue

10 kilograms of beef

100 kilograms of grain

Marine Primary ProductivityMarine Primary Productivity

• Compared to terrestrial primary productivity– Overall marine productivity is only slightly less

– Marine standing crop is significantly less

– Marine ecosystem cycles energy and nutrients much more rapidly • Marine primary producers are phytoplankton

PlanktonPlankton

• Plankton: Organisms that exist adrift in the ocean, unable to swim against currents and waves, most, but not all are very small or microscopic

– Not a single species

– Both autotrophs and heterotrophs• Phytoplankton: autotrophic plankton

• Zooplankton: heterotrophic plankton

– Feed on phytoplankton and other zooplankton

PlanktonPlankton

• Meroplankton: organisms that only live part of their lives as plankton

– Ex: fish larvae

• Holoplankton: organisms that live their entire lives as plankton

– Ex: diatoms

PhytoplanktonPhytoplankton

• The most important primary producers in the marine environment.

– Account for between 92% and 96%

– Marine plants, kelp, and other multicellular photosynthesizing organisms account for 2%-5%

– Deep ocean chemosynthesis accounts for the remainder.

Phytoplankton: four primary kindsPhytoplankton: four primary kinds

1. Diatoms– Most efficient photosynthesizers known

• Convert more than half the light energy they absorb into carbs

– Cell wall made of silica• Silica: a transparent, glass-like material

• Admits light

• Can be subject to photoinhibition

– Photoinhibition: The condition in which excess light overwhelms an autotroph’s ability to photosynthesize

Phytoplankton: four primary kindsPhytoplankton: four primary kinds

2. Dinoflagellates– Characterized by 1 or 2 flagella

• Flagella: a whip-like tail used for locomotion

– Most are autotrophic, but a few are heterotrophic

– Reproduce extremely rapidly• Responsible for most plankton blooms

– Ie: red tide

Phytoplankton: four primary kindsPhytoplankton: four primary kinds

3. Coccolithophores– Shell made of calcium carbonate

• Calcium carbonate: translucent, milky-white material

• Screens out some light

• Live in brightly lit, shallow water

– All Autotrophic

– Reproduce extremely rapidly• Responsible for most plankton blooms

– ie: red tide

Phytoplankton: four primary kindsPhytoplankton: four primary kinds

4. Silicoflagellates– Internal supporting structures made of silica

– Both autotrophic and heterotrophic

– Have one long flagellum

Limits on Marine ProductivityLimits on Marine Productivity

• Limiting Factors: physiological or biological necessities that restrict survival

– Too much or too little will affect survival

• Light– Too little stops photosynthesis

– Too much results in photoinhibition

Limits on Marine ProductivityLimits on Marine Productivity

• Nutrients– Too little limits population growth– Eutrophication: can result in harmful

plankton blooms• Eutrophication: over abundance of nutrients in

an ecosystem• Plankton Bloom: overpopulation of

photosynthysizers that depletes nutrient supply in an area– In extreme cases, can deplete oxygen supply in

water

Energy Flow Through the Biosphere

Part 3

Food chains: Pathways for matter and energyFood chains: Pathways for matter and energy

• In a food chain, nutrients and energy move from autotrophs to heterotrophs and, eventually, to decomposers.

• A food chain is a simple model that scientists use to show how matter and energy move through an ecosystem.

Food chains: Pathways for matter and energyFood chains: Pathways for matter and energy

• A food chain is drawn using arrows to indicate the direction in which energy is transferred from one organism to the next.

berries → mice → black bear

Trophic RelationshipsTrophic Relationships

• Each organism in a food chain represents a feeding step, or trophic level, in the passage of energy and materials.

• Primary Consumer: first trophic level; an organism that feeds on primary producers

Trophic RelationshipsTrophic Relationships

• Secondary Consumer: organism that feeds on a primary consumer.

• Tertiary Consumer: an organism that feeds on a seconary consumer

• A food chain represents only one possible route for the transfer of matter and energy through an ecosystem.

Food websFood webs

• Ecologists interested in energy flow in an ecosystem may set up experiments with as many organisms in the community as they can.

• The model they create, called a food web, shows all the possible feeding relationships at each trophic level in a community.

Food websFood webs

Food chains: Pathways for matter and energyFood chains: Pathways for matter and energy• Most food chains consist of two, three, or four

transfers.

• The amount of energy remaining in the final transfer is only a portion of what was available at the first transfer.

• A portion of the energy is given off as heat at each transfer.

Energy and trophic levels: Ecological pyramidsEnergy and trophic levels: Ecological pyramids

• The pyramid of energy illustrates that the amount of available energy decreases at each succeeding trophic level.

Pyramid of Energy

Heat

Heat

Heat

Heat

0.1% Consumers

1% Consumers

10% Consumers

100% Producers

Parasites, scavengers, and

decomposers feed at each

level.

Energy and trophic levels: Ecological pyramidsEnergy and trophic levels: Ecological pyramids

• The total energy transfer from one trophic level to the next is only about ten percent because organisms fail to capture and eat all the food energy available at the trophic level below them.

Energy and trophic levels: Ecological pyramidsEnergy and trophic levels: Ecological pyramids

• Some of the energy transferred at each successive trophic level enters the environment as heat, but the total amount of energy remains the same.