This document defines key terms related to oceanic productivity such as primary productivity, photosynthesis, chemosynthesis, trophic levels, food chains, and food webs. It also summarizes that primary productivity in a region is influenced by nutrient availability and sunlight, energy is inefficiently transferred between trophic levels at around 2%, and organisms in a food web have more alternative food sources than those in a food chain.

1. Oceanic Productivity 15.3

2. Primary Productivity
• The production of
organic matter
from inorganic
substances
through
photosynthesis or
chemosynthesis.

3. Photosynthesis
• The process by which plants, algae, and
certain prokaryotes use light energy to
convert water and carbon dioxide into energy-
rich glucose molecules.

4. Chemosynthesis
• The process by which certain microorganisms
use chemical energy to produce food.

5. Trophic Level
• A nourishment level
in a food chain; plant
and algae producers
constitute the lowest
level, followed by
herbivores and series
of carnivores at
progressively higher
levels.

6. Food Chain
• A succession
of organisms
through which
food energy is
transferred,
starting with
primary
producers.

7. Food Web
• A group of interrelated food chains.

8. Key Concept
• What factors influence a region’s
photosynthetic productivity?
–Two factors influence a region’s
photosynthetic productivity: the
availability of nutrients and the
amount of solar radiation, or sunlight.

9. Key Concept
• Describe the transfer efficiency
between trophic levels?
–The transfer of energy between trophic
levels is very inefficient. The average
amount of energy transferred between
trophic levels is roughly 2 percent.

10. Key Concept
• What advantages do organisms in a
food web have over those in a food
chain?
–Animals that feed through a food web
rather than a food chain are more
likely to survive because they have
alternative foods to eat should one of
their food sources diminish or
disappear.