Oceanography
An Invitation to Marine Science, 7th
Tom Garrison
Chapter 13
Life in the Ocean
Chapter 13 Study Plan
• Life on Earth Is Notable for Unity and Diversity
• The Flow of Energy through Living Things Allows Them to
Maintain Complex Organization
• Primary Productivity Is the Synthesis of Organic Materials
• Living Organisms Are Built from a Few Elements
• Elements Cycle between Living Organisms and Their
Surroundings
• Marine Life Success Depends upon Physical and
Biological Environmental Factors
• The Marine Environment Is Classified in Distinct Zones
• The Concept of Evolution Helps Explain Life in the Ocean
• Oceanic Life Is Classified by Evolutionary Heritage
Chapter 13 Main Concepts
• All of Earth’s life-forms are related. All have apparently evolved from a
single ancient instant of origin.
• All life activity is involved, directly or indirectly, in energy
transformation and transfer. Photosynthesis appears to be the
dominant method of binding energy into carbohydrates on this planet
(at least at Earth’s surface).
• Primary productivity involves the synthesis of organic materials from
inorganic substances by photosynthesis or chemosynthesis. Primary
productivity is expressed in grams of carbon bound into organic
material per square meter of ocean surface area per year (gC/m2/yr).
• The atoms and small molecules that make up the biochemicals, and
thus the bodies, of organisms move between the living and nonliving
realms in biogeochemical cycles. An organism’s success can be
limited by inappropriate amounts of these materials.
• Evolution happens. Organisms change as time passes, adapting by
natural selection to their environments.
• Oceanic life is classified by evolutionary heritage and its location in
the environment.
Energy Can Be Stored through
Photosynthesis
• Most of the energy used by marine
organisms to make food comes from the sun.
• Photosynthesis is the process used by most
producers to convert the sun’s energy to food
energy.
• Chemosynthesis is the production of food
from inorganic molecules in the environment.
Energy Can Be Stored through
Photosynthesis
In photosynthesis, energy from sunlight is used to bond six separate
carbon atoms (derived from carbon dioxide) into a single energy-rich,
six-carbon molecule (the sugar glucose). The pigment chlorophyll
absorbs and briefly stores the light energy needed to drive the reactions.
Water is broken down in the process and oxygen is released.
Energy Can Be Stored through
Photosynthesis
The flow of energy
through living
systems. At each
step, energy is
degraded (that is,
transformed into a
less useful form).
Sun
Producers
Photosynthesizers:
Green plants
and algae, and
specialized
bacteria
Consumers
Respirers:
Animals and
decomposers and
plants at night
To space
Stepped Art
Fig. 13-3, p. 347
Energy Can Also Be Stored
through Chemosynthesis
A form of chemosynthesis.
In this example, 6
molecules of oxygen and
24 molecules of hydrogen
sulfide to form glucose.
(other products include 24
sulfur atoms and 18 water
molecules.) The energy to
bond carbon atoms into
glucose comes from
breaking the chemical
bonds holding the sulfur
and hydrogen atoms
together in hydrogen
sulfide.
Primary Productivity Is the
Synthesis of Organic Materials
Oceanic productivity
– the incorporation of
carbon atoms into
carbohydrates – is
measured in grams
of carbon bound into
carbohydrates per
square meter of
ocean surface area
per year gC/m2/yr.
Global Primary Productivity
Oceanic productivity can be observed from space. NASA’s SeaWiFS satellite, launched
in 1997, can detect the amount of chlorophyll in ocean surface water. Chlorophyll content
allows an estimate of productivity. Red, yellow, and green areas indicate high primary
productivity; blue areas indicate low. This image was derived from measurements made
from September 1997 through August 1998.
Food Webs Disperse Energy
through Communities
• What terms are used to describe feeding relationships?
• Autotrophs – organisms that make their own food, also
called producers.
• Heterotrophs – organisms that must consume other
organisms for energy
• Trophic pyramid – a model that describes who eats
whom
• Primary consumers – these organisms eat producers
• Secondary Consumers – these organisms eat primary
consumers
• Top consumers – the top of the tropic pyramid
Food Webs Disperse Energy
through Communities
A generalized trophic pyramid. How many kilograms of primary producers are necessary
to maintain 1 kilogram of tuna, a top carnivore? What is required for an average tuna
sandwich? Using the trophic pyramid model shown here, you can see that 1 kilogram of
tuna (enough to make ten 1/4-pound tuna sandwiches) at the fifth trophic level (the fifth
feeding step of the pyramid) is supported by 10 kilograms of mid-sized fish at the fourth,
which in turn is supported by 100 kilograms of small fish at the third, who have fed on
1,000 kilograms of zooplankton (primary consumers) at the second, which have eaten
10,000 kilograms of phytoplankton (small autotrophs, primary producers) at the first. The
quarter-pound tuna sandwich has a long and energetic history.
Food Webs Disperse Energy
through Communities
Diatoms, and other primary
producers, convert the
energy from the sun into
food used by the rest of the
oceanic community.
(left) A simplified food web,
illustrating the major trophic
relationships leading to an
adult blue whale.
The arrows show the
direction of energy flow; the
numbers on each area
represent the trophic level
at which the organism is
feeding.
Elements Cycle between Living
Organisms and Their Surroundings
• What are some atoms and molecules that
cycle in biogeochemical cycles?
• Carbon - present in all organic molecules
• Nitrogen - found in proteins and nucleic
acids
• Phosphorus and silicon – found in rigid
parts of organisms
• Iron and trace metals - used for electron
transport
The Carbon Cycle Is Earth’s
Largest Cycle
The Carbon Cycle.
Carbon dioxide dissolved in
seawater is the source of the
carbon atoms assembled into
food (initially glucose) by
photosynthesizers and most
chemosynthetic organisms.
When this food is metabolized,
the carbon dioxide is returned to
the environment. Some carbon
dioxide is converted into
bicarbonate ions and
incorporated into the shells of
marine organisms. When these
organisms die, their shells can
sink to the bottom and be
compressed to form limestone.
Tectonic forces may eventually
bring the limestone to the
surface, where erosion will
return the carbon to the ocean.
Nitrogen Must Be “Fixed” to Be
Available to Organisms
The Nitrogen Cycle.
The atmosphere’s vast reserve
of nitrogen cannot be
assimilated by living organisms
until it is “fixed” by bacteria and
cyanobacteria, usually in the
form of ammonium and nitrite
ions. Nitrogen is an essential
element in the construction of
proteins, nucleic acids, and a
few other critical biochemicals.
Upwelling and runoff from the
land bring useful nitrogen into
the photic zone, where
producers can incorporate it
into essential molecules.
Phosphorus and Silicon Cycle in
Three Distinct Loops
The Phosphorus Cycle.
Phosphorus is an essential
part of the energytransporting compounds
used by all of Earth’s lifeforms. Much of the
phosphorus-containing
materials in the ocean falls
to the seabed, is covered
with sediment, is subducted
by tectonic forces, and
millions of years later
returns to the surface
through volcanic eruptions.
Physical and Biological Factors
Affect the Functions of an Organism
• A limiting factor is a factor found in the
environment that can be harmful if present in
quantities that are too large or too small.
– Any factor required for life can become a limiting
factor.
• Any aspect of the physical environment that affects
living organisms is a physical factor.
• What are the most important physical factors for
marine organisms?
– Light, dissolved gases, temperature, salinity
– Acid-base balance, hydrostatic pressure, nutrients
Physical and Biological Factors
Affect the Functions of an Organism
• Biological factors also affect living
organisms in the ocean.
• Some biologic factors that affect ocean
organisms:
– Feeding relationships
– Crowding (competition for space)
– Metabolic wastes
– Defense of territory
Photosynthesis Depends on Light
Most of the biological productivity
of the ocean occurs in an area
near the surface called the
euphotic zone.
Below the euphotic zone lies the
disphotic zone.
Below the disphotic zone lies the
dark aphotic zone, the vast bulk
of the ocean where sunlight never
reaches.
(left) The relationship among the
euphotic, disphotic, and aphotic
zones.
(The euphotic zone statistic is for
mid-latitude waters averaged
through a year).
Temperature Influences
Metabolic Rate
Temperatures of marine
waters capable of
supporting life.
Some isolated areas of
the ocean, notable
within and beneath
hydrothermal vents,
may support specialized
living organisms at
temperatures of up to
400°C (750°F)!
Substances Move through Cells by
Diffusion, Osmosis, and Active Transport
Organisms in the ocean rely on these
processes for many life functions.
•
•
•
Diffusion is mixing due to random
molecular movements.
Osmosis is diffusion of water through a
membrane
Active transport is the transport of a
substance against a concentration gradient.
Active transport requires energy input.
(left) The effects of osmosis in different
environments. (a) An isotonic solution
contains the same concentration of dissolved
solids (green) and water molecules (blue) as
a cell. Cells placed in isotonic solutions do not
change size since there is no net movement
of water. (b) A hypertonic solution contains a
higher concentration of dissolved solids than a
cell does. A cell placed in a hypotonic solution
will shrink as water moves out of the cell to
the surrounding solution by osmosis. (c) A
hypotonic solution contains a lower dissolved
solids concentration than a cell does. A cell
placed in a hypotonic solution will swell and
rupture as water moves by osmosis from the
environment into the cell.
Substances Move through Cells by
Diffusion, Osmosis, and Active Transport
A summary of the three main ways
by which substances move into and
out of cells. (a) In diffusion,
molecules introduced into a container
(left) become evenly distributed after
a period of time (right). (b) In
osmosis, the diffusion of water may
cause a cell to swell. The blue dots
represent water molecules, the black
dots represent dissolved particles,
and the arrows indicate the direction
of water movement into the original
cell. Under different conditions, water
may move out of the cell, causing it
to shrink. (c) Active transport enables
a cell to accumulate molecules even
when there are move inside the cell
than outside. Cells may expel other
molecules by the same process.
Water
Dye
cube
Day 1
Day 2
Day 5
Day 20
Stepped Art
Fig. 13-16, p. 361
The Marine Environment Is
Classified into Distinct Zones
Scientists divide the marine
environment into zones,
areas with homogeneous
physical features.
Zones are classified by
location and the behavior of
the organisms found there.
Evolution Appears to Operate by
Natural Selection
• Earth’s organisms have changed, or evolved,
over the course of 4 billion years.
• Evolution occurs through the process of
natural selection.
• The environment favors individuals that are
well adapted. Their favorable traits are
retained because they contribute to the
organism’s reproductive success.
Systems of Classification May Be
Artificial or Natural
• What were the contributions of Carolus
Linnaeus?
• He was one of the first to use a system of
natural classification
• He developed a classification system based
on hierarchy
• He developed a system of scientific names
for organisms
Systems of Classification May Be
Artificial or Natural
The study of biological classification is called
taxonomy.
(right) Carolus Linnaeus - the father of modern
taxonomy - in Laplander costume. (He went on
a scientific expedition to Lapland in 1732).
Linnaeus invented three supreme categories,
or kingdoms: animal, vegetable, and mineral.
Today’s biologists leave the mineral kingdom
to the geologists and have expanded
Linnaeus’s two living kingdoms to six.
Linnaeus’s great contribution was a system of
classification based on hierarchy, a grouping
of objects by degrees of complexity, grade, or
class.
Systems of Classification May Be
Artificial or Natural
A family tree showing the
relationship of kingdoms
presumably evolved from a
distant common ancestor.
The Bacteria and Archaea
contain single-celled
organisms without nuclei
or organelles; collectively,
they are called
prokaryotes. The fungi,
protists, animals, and
plants contain organisms
with cells having nuclei
and organelles;
collectively, they are called
eukaryotes.
Systems of Classification May Be
Artificial or Natural
The modern system of
biological classification,
using the Rex sole, a
type of flatfish
(Glyptocephalus
zachirus) as an
example. Note the
boxes-within-boxes
approach, a hierarchy.
Ellipses (…) indicate
groups not shown for
clarity.
Chapter 13 in Perspective
In this chapter you learned that the atoms in living things are no different from the atoms in
nonliving things; in fact, they move between the living and nonliving realms in large biogeochemical
cycles. Also, the energy that powers living things is the same energy found in inanimate objects. So
how is it possible to distinguish between life and non-life? The discussion of life in this chapter
highlights the highly organized nature of living material and the complex ways that living things
manipulate matter and energy.
Life runs on food, and some of the world’s most important producers of food are found in the ocean.
Understanding the term primary producers is central to this chapter: Primary indicates that food webs
start with those organisms; producer emphasizes that the organisms make glucose, an all-important
food molecule. Primary producers are organisms that synthesize energy-rich organic compounds
(food) from inorganic substances. If someone asks you, “What is produced in primary productivity?” a
safe answer is, “The carbohydrate glucose.”
Marine life depends on the ocean’s chemical composition and physical characteristics for life support.
The aspects of the physical environment that affect living organisms are called physical factors,
examples of which are water’s transparency, temperature, dissolved nutrients, salinity, dissolved
gases, acid–base balance, and hydrostatic pressure. Life and the ocean have evolved together –
change in one is met by change in the other. The evolution of life on Earth and the scheme of natural
classification we use to organize it are closely related. Our categorizations of living things are based
on their presumed ancestry and history.
In the next chapter you will learn about the primary producers themselves and meet the ocean’s
largest community, the drifters of the plankton. Primary productivity will be revisited – you will
discover how researchers measure productivity and what some of the physical and biological factors
are that limit it. We will see how advanced marine plants fit into the overall productivity picture and
begin thinking about animals.