Oceanography Lecture Notes Outline

Life in the Ocean - An Overview


I. Lecture Content

Definition of Life What Does it Mean to be "Alive"?

Biogeochemical Cycles Carbon, Nitrogen, and Others

Physical Controls Affecting Life Matter, Energy, and the "Zone"

Biological Controls Affecting Life Life's Affect on Life

Evolution of Marine Life Change through Time

Classification of Marine Life Taxonomy and Phylogenies

Classification of Marine Habitats The Various Living Zones


II. Defining Life

A. Precise Formal Definition is Elusive


1. A definition of life must have the following criteria:


        Highly organized structure(s)


        Low-entropy state


        Capture, store, transmit, and transform energy


        Capable of reproducing


        Adapt to the environment


        Change through time


2. The intimate exchange of matter and energy between

living and nonliving systems makes it difficult in many

cases to draw a line where one stops and the other starts


3. The essential difference between living and nonliving

systems is the living system's:


        Ways of utilizing energy to move, grow and maintain


        Functioning cells


        Ability to reproduce

o       Generate new entities with similar cells


B. Life and Matter

1. All living systems on Earth contain matter

        Consist of 23 of 107 known chemical elements


        Only four of these make up nearly 99% of the mass of all

living things:

o       Oxygen

o       Carbon

o       Hydrogen

o       Nitrogen


2. The 23 elements in living things combine to form several

classes of biochemicals essential to all life. They are:

        carbohydrates (sugars, starches, and cellulose)

        lipids (fatty acids, fats, waxes, and oils)

        proteins and enzymes

        nucleic acids


3. The across-the-board sameness and occurrence of all

the above substances in all living things on Earth strongly

suggest a common origin (ancestor) to all groups of life

C. Life and Energy

1. All living systems capture, store, transfer, and transform



2. Living systems not able to create energy - only change it


3. Different living systems have unique variations in how

they capture, store, transfer, and transform energy

        Photosynthesis of plants


        Chemosynthesis of certain bacteria


4. Organisms utilize energy input to both move, grow and

maintain their highly ordered structures


        Temporarily delays Second Law of thermodynamics


        Work against entropy = lowering degree of disorder


5. Life derives its energy principally from the sun

        Directly - Photosynthesizers (autotrophs)

        Indirectly - Consume autotrophs (heterotrophs)

        There are a few exceptions

o       Deep sea vent bacteria


6. Typical path of energy in living systems

        Sunlight ▬► chemical energy ▬► kinetic energy ▬► heat


III. Biogeochemical Cycles

A. Biogeochemical cycles defined

1. The movement of the atoms and small molecules (that

life depends upon) between living and nonliving systems


2. The atoms and small molecules that life depends upon

(making up the living tissue of organisms) are either:


o       Always on the move in and out of living systems


o       Locked away in the Earth


      Deeply buried rock


B. There are Several Major Biogeochemical Cycles






      Trace Metals


C. The Carbon Cycle

1. The largest of all cycles in terms of mass (see fig. 13.3)

        Reservoirs include life, land, ocean and atmosphere


        Forms include carbonate sediment and rock, hydrocarbon

fuels, gaseous CO2 in the atmosphere and dissolved gas in the

ocean, in bodies of organisms, dissolved organic carbon, and

dissolved inorganic carbon-based ions, like carbonic acid


2. Carbon is the basic building block of all life on Earth

        Ability to form long chains to which other atoms can attach


3. Carbon enters the atmosphere and ocean in several ways

        Life respiration

        Volcanic eruption

        Uplift, weathering, and erosion of carbonate rock

        Burning of fossil fuels


4. Carbon initially enters the living world in one main way:

        Carbon fixation by photosynthesis

        Either from the atmosphere or ocean


5. Carbon moves through the living world in several ways:

        Moving within a living organism

o                Incorporated into cells of organism for growth

         45% of total used for organism growth

o                Respiration (converted to end product - CO2)

         45% of total used in respiratio

o                Excreted as dissolved organic carbon (DOC)

         10% of total lost to waste as DOC


        Moving between living organisms

o       Plant matter eaten by animals

o       Animals eat other animals


6. The dissolved organic carbon is taken in by bacteria


7. Dead falling organic matter in ocean mostly converted to

CO2 by respirating bacteria who consume detritus


8. The less than 1% of organic detritus not converted to

CO2 by bacteria in the water column or ocean bottom is

incorporated into carbonate sediment and buried


9. Buried carbonate sediment and rock in ocean bottom

will at some point get recycled back into the life cycle by

         Uplift, weathering and erosion

   Volcanic gas release of melted subducted sediments


D. The Nitrogen Cycle

1. The second largest of all cycles in terms of mass

        See figure 13.4


        Reservoirs include life, land, ocean and atmosphere


        Forms include nitrate rocks and sediment, organic matter,

gaseous N2 in the atmosphere, dissolved N2 in the ocean, in

bodies of organisms, dissolved organic nitrogen, and

dissolved inorganic nitrogen-based ions like NH4+, NO3-, and



2. Nitrogen is a basic building block of all life on Earth

        Critical element in production of proteins, nucleic aids, and


3. Nitrogen enters the atmosphere and ocean as follows:

        Volcanic eruption

        Uplift, weathering, and erosion of nitrogen material


4. Nitrogen initially enters the living world in one main way:

        Fixation of nitrogen by special organisms

        Either from the atmosphere, land, or ocean


5. Nitrogen fixation is the process by which nitrogen is

bound to either oxygen or hydrogen into a usable form

by living organisms


6. Usable nitrogen moves through the living world:

        Moving within a living organism

o                Incorporated into cells of organism for growth


o                Denitrifying bacteria use reduced forms of nitrogen

ions for respiration


o                Excreted as dissolved organic carbon (DON)


        Moving between living organisms

o       Plant matter eaten by animals

o       Animals eat other animals


7. The nitrogen cycle is shown in Figure 13.4 (page 324)


E. The Phosphorus Cycle

1. The phosphorous cycle is relatively simple

        Cycles in three loops (see Fig, 13.5)


        Reservoirs include life, land, and ocean


        Forms include phosphate rocks and sediment, organic

matter, dissolved PO4 in the ocean, and in bodies of



2. Phosphorus is a basic building material of all life on


        Critical element in binding of nucleic aids

        Used in the molecules that fuel cells

        Goes into calcium phosphate for bones, teeth, nails,

and shells

3. Phosphorus enters the ocean as follows:

        Volcanic eruption via precipitation and rivers

        Uplift, weathering, and erosion of phosphorous material

via rivers


4. Phosphorus has three different cycles

        Fast cycle - direct life-death-life

o       Days to years

        Slower cycle - life-death-ocean

o       Hundreds of years

        Slowest cycle -life-death-Earth

o       Millions of years


F. The Silica Cycle

1. Very similar to phosphorus cycle


2. Silica used in connective tissue and marine shells


G. The Iron Cycle and Other Trace Elements

1. Similar to phosphorus and silica cycles

        Simple loops

        Reservoirs include land, ocean, and organisms

        Forms include iron-rich rock and sediment, iron oxides,

dissolved iron, and iron in organisms


2. Iron is nearly insoluble seawater

        Typically very low concentrations

        Very reactive in seawater

        Easily partitions into marine sediment


3. Iron concentrations are typically so low that it becomes

a limiting factor to the growth of organisms


H. Limiting Factors in the Marine Environment

1. A limiting factor is any physical or biological necessity

whose presence in inappropriate amounts limits the

normal function of an organism

        Element or nutrient



        Proper pH


IV. Physical Factors Affecting Marine Life

A. The Ocean is Marine Lifes Support System

1.      Depend on the oceans chemical constituents


2.      Depend on stable physical conditions


3.      Very intimate interrelationship between marine life and

its ocean environment


4.      The various chemical and physical aspects that marine

life rely on to survive are termed physical factors


5. The most critical physical factors for marine life are:




      Dissolved nutrients and gases

      pH balance

      Hydrostatic pressure


B. Sunlight is Essential to Most Marine Life

1. Absolutely essential to photosynthesizing organisms


2. Transparency of ocean water to sunlight allows

photosynthesis to occur down to over 100 meters deep


3. Differential absorption of various wavelengths of light

with depth


4. Depth of water penetration also limited by particulate

matter in the water column


5. Latitude and atmospheric cloud cover also affect amount

of sunlight penetrating ocean surface


C. Water Temperature

1. Ocean temperatures vary with latitude and depth


      Vast bulk of oceans water is near freezing


      Only tropical and temperate surface waters get



      See Figure 13.12 for seawater temp variations


2. Great majority of marine organisms are cold-blooded

      Cold-blooded = ectothermic or poikilothermic


      Warm-blooded = endothermic or homeothermic


3. Rates at which biochemical reactions take place depend

on seawater temperature


      Metabolic rate roughly doubles with a 10C (18F)

increase in sea temperature


      Warmer water ectothermic organisms have higher

metabolic rates than their colder water cousins


4. All marine organisms have external temperature ranges


      Endothermic organisms have fairly narrow ranges


      Ectothermic organisms have wider ranges

D. Salinity

1. Ocean salinity can vary tremendously from place to place

      Coastal areas near rivers


      Isolated, high evaporative seas


      Less variable with depth


      Slightly saltier with depth


2. Salinity levels affect cell membranes of organisms

      Changing salinity can damage cells membranes


      Affects internal cell salt-water balance


      Also affects buoyancy of an organism


F. Dissolved Nutrients and Gases

1. Dissolved nutrients and certain gases are required by

organisms to stay alive they include:

      Nitrogen (NO3-)

      Phosphorus (PO43-)




      Trace elements


      Carbon dioxide


2. The above necessary dissolved nutrients and gases are

generally in short or limited supply in much of the ocean


      Exception is CO2, which is rather abundant


      These materials are depleted during times of rapid

growth and/or reproduction cycles


3. Rapid photosynthesis depletes CO2 , but increases O2


4. Rapid respiration depletes O2, which in turn can cause a

die-off, whereby decomposition of bodies by bacteria will

further decrease O2 levels, causing a larger, broad die-off


G. Acid Base (pH) Balance

1. Seawater is slightly alkaline


      pH averages around 8


2. Variations between 8.5 and 7.0 occur in seawater


      Much smaller than that of soils


      Affects dissolved concentrations of nutrients and gases


H. Hydrostatic Pressure

1. Great hydrostatic pressure has little to physical effects

on marine life in ordinary situations


      Deep water fish rapidly hauled to the surface by

fisherman may experience critical effects


2. Hydrostatic pressure can affect degree of dissolution of

elements and gases


I. Importance of Intermixing Physical Factors

1. Physical factors are closely interrelated


      A change in one factor will typically cause a

change in one or more other factors


      See chart in Figure 13.13 for an example


V. Biological Factors Affecting Marine Life

A. Biological Factors Defined

1. Biological factors are aspects of the marine environment

that are generated by marine organisms, which in turn

affect living marine organisms


2. Biological factors include the following:


      Feeding relationships

      Organism (population) density (crowding)

      Organism waste products

      Defensive behaviors



VI. Marine Life Adaptations to Marine Conditions

A. Diffusion, Osmosis, and Active Transport

1. Importance of moving water, food and wastes in an out

of cells


2. Importance of moving water, food and wastes in an out

between organism and environment


B. The Surface-to-Volume Problem

1. Finding the right surface area to volume for both cells

and the size of organism for optimum functioning


C. Density and Buoyancy

1. Control of vertical movement of organism in water



D. Viscosity Drag versus turbulence

1. Optimization of organism body shape for movement

through seawater


2. Small animals have a drag problem


3. Large animals have a turbulence problem


E. Water Movement

1. Ocean Currents

      Pelagic drifting organisms

      Vertical movements


2. Tidal fluctuations

3. Wave and surf action


VII. Evolution of Life in the Ocean

A. Observations of Present Day Life on Earth

1. There is a great diversity of life forms

      Millions of different species are already known


      Filling millions of different environmental niches


2. There are a great number of similarities amongst life


o       External structures and functions (body parts)



o       Internal design (cellular and genetic levels)


B. Observations of Ancient Life in Earth's Rock Record

1. First signs of life found in rock almost 4 billion years old


2. Earliest life was very simple and primitive




3. First animals with hard parts showed up around 500

millions years ago

      Exclusively marine animals


      Most of these organisms have been long extinct

o       Archeocyathids

o       Trilobites

o       Various shelled invertebrates


4. There has been a great diversity of life ancient forms

      Hundreds of thousands of different species documented


      Filling many different environmental niches


5. Number of similarities amongst ancient life


o       External structures and functions (body parts)


6. The assemblage of documented ancient organisms

(now fossils) living at any given time in the past is

totally unique to both, earlier or later assemblages of

preserved ancient life


      Shown at any given geographic level - local, regional, or



      Most recent fossils found in rock closely resemble the

organisms alive today


      Increasingly older fossils are progressively different


      Systematic disappearance (extinction) of old forms


      Systematic appearance (speciation) of new forms


      Complexity of organisms has increased with time

o       Prokaryotes to eukaryotes

o       Single-celled to multi-celled organisms

o       Invertebrates to vertebrates

o       Fishes to Amphibians to Reptiles to Mammals


7. Great extinctions events happen every 50 to 100 MY


      Each event wiped out a quarter to half of all species


      Extinction events attributed to bolides & eruptions


8. Extinction events followed by explosion of new life forms


      Uniquely new organisms would fill in new niches or old

niches left open from recently extinct life forms


C. What is Evolution?

1. Evolution defined:

      Change through time


2. Facts about Nature:

      The Universe has changed through time

      Our solar system has changed through time

      The physical Earth has changed through time

      Life on Earth has changed through time


3. Interpretations that Best explain the observed changes:

      The Big Bang theory

      Theory of Stellar evolution

      The Solar System accretion theory

      The Plate tectonic theory

      The theory of Biologic evolution


D. The Theory of Life Evolution

1. Biologic Evolution defined:

      The change in heredity characteristics of groups of

organisms over the course of generations due to the

combined affects of genetic mutation, natural selection,

and geographical isolation


2. Charles Darwin is credited with proposing evolution by

natural selection


3. Natural selection defined:

      Greater reproductive success among particular members

of a species arising from genetically determined

characteristics that confer an advantage in a particular



4. Genetic mutation defined:

      Inheritable change in the make-up of an organisms genes



      Both favorable and unfavorable mutations occur


      Favorable mutations are the ones that provide an organism

with an environmental advantage


5. Geographical isolation defined:

      Physical barriers to gene flow

o       Mountain ranges

o       Oceans

o       Deserts


      Physical barriers come and go with time

o       Plate tectonics the primary agent


6. New species emerge when natural selection and genetic

mutation are able to proceed within a geographically

isolated population (gene pool) with sufficient time


7. Opposition to the Theory of Evolution has come mainly from

Christian groups who favor creationism or intelligent design

      Nonscientific views based mainly on Bible scripture

VIII. Classification of Marine Life

A. Classification Systems Divide Life Based Upon Likeness

1. Study of biological classification is termed taxonomy


2. A classification system based upon only on gross

external physical and behavioral similarities is termed

an artificial system of classification

      Example is grouping all life forms that swim into a single

category or group

      List would include humans, polar bears, seals, whales,

all types of fish, squid, jellyfish, etc


3. A classification system for living organisms based upon

on the total number of structural and biochemical

similarities is termed a natural system of classification


      Arranged in an order that is

o       Logical

o       Systematic

o       Hierarchal


      Example is grouping of all types of turtles into a

single category or group, regardless of whether

or not they can swim


4. A classification system for ancient organisms based

upon on the total number of structural similarities is

also considered a natural system of classification


      Arranged in an order that is

o       Logical

o       Systematic

o       Hierarchal


      Example is grouping of all types of ancient

trilobites into a single category or group, based

on unique morphological characteristics

B. Modern Natural Classification System of Life Forms

1. Modern phylogeny is based upon several criteria:


      Physical, biochemical, and genetic structures


      Evolutionary relationships


2. Father of modern biological phylogeny - Carolus Linnaeus


3. Contains Six Supreme Categories

      Termed Kingdoms


      Five are "natural"

o       Archaea

o       Bacteria

o       Fungi

o       Plantae

o       Animalia


      One is "unnatural"

o       Protista


      Study Figure 13.9 and Table 13.2


3. Further subcategories based on hierarchy

      Degree of similarity, complexity, grade, or class


      Largest category at the top

o       Kingdom

o       Very few groups at kingdom level


      Smallest category at the bottom

o       Species

o       Very large number of groups at species level


4. Seven hierarchal subcategories beneath kingdom









      See Figure 13.10


5. Naming a specific animal includes two names



      An animal's scientific name


IX. Classification of Marine Habitats

A. Based Upon Homogeneity of Environmental Features

1. Classification based on similar sunlight characteristics


2. Classification based on similarity in physical location

B. Classification by Sunlight

1. Classification is based upon the intensity or absence of

sunlight within the ocean water column


2. Photic zone

      Uppermost layer of the ocean that is sunlit


      Includes the upper 600 meters of ocean column


      Varies in maximum depth according to location


      Region where photosynthesis takes place


3. Euphotic zone

      Upper part of photic zone


      Plant production by photosynthesis exceeds the loss of

carbohydrates by plant respiration


4. Disphotic zone

      Lower part of photic zone


      Loss of carbohydrates by plant respiration exceeds plant

production by photosynthesis


5. Aphotic zone

      Lies beneath the disphotic zone


      Photosynthesis is unsustainable or impossible


      This dark zone is the largest region of the ocean


C. Classification by Location

1. Primary division is between ocean water column and

ocean bottom

      Pelagic zone = Open water


      Benthic zone = Sea bottom


2. Pelagic zone divided into two subzones:

      Neritic zone = near shore over the continental



      Oceanic zone = Offshore over deep water


      Free-swimming and floating organisms dwell here



2. Benthic Zone is divided into several subzones

      Littoral zone = intertidal bottom


      Sublittoral zone = continental shelf bottom

seaward of littoral zone


      Bathyal zone = Continental slope and rise bottom


      Abyssal zone = Vast true ocean basin bottom


      Hadal zone = super deep ocean bottom; trenches


      Burrowing, attached, crawling, and swimming

organisms found on or in the bottom


D. Classification of Organisms by Behavior

1. Primary division is based upon both, the organisms

ability, or lack of ability, to stay suspended in the

water column


      Pelagic = Floating, suspended in water column


      Benthic = Living on or in the bottom


2. Pelagic organisms divided into two groups


      Plankton = suspended; passive-swimmers


      Nekton = active swimmers


X. Life In the Ocean Vocabulary - Chapter 13


abyssal zone

active transport



aphotic zone


artificial system of classification


bathyal zone

benthic zone

biogeochemical cycle

biological factor

carbon factor

convergent evolution

Darwin, Charles

denintrifying bacteria


disphotic zone

dissolved organic carbon (DOC)

dissolved organic nitrogen (DON)


ectotherm, ectothermic

endotherm, endothermic




euphotic zone


hadal zone


hydrostatic pressure





limiting factor

Linnaeus, Carolus

littoral zone

mass extinction

metabolic rate


natural selection

natural system of classification


neritic zone

nitrifying bacteria

nitrogen cycle


oceanic zone



pelagic zone

photic zone


physical factor





scientific name

second law of thermodynamics


sublitttoral zone

surface-to-volume ratio


theory of evolution