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Spatial Distribution
•Marine organisms are either pelagic (found in the
water column) or benthic (living on, in, or near the
seafloor). Benthic organisms often move on the sea
bottom (epifaunal) or through the sediment beneath
its surface (infaunal).
–
Pelagic species found in the water column are either
swimmers (nekton) or drifters (plankton). Planktonic
drifters are termed phytoplankton if they are
photosynthetic or zooplankton if they are heterotrophic
consumers.
Spatial Distribution
•Fig. 2.1 A spatial classification of marine organisms.
Evolutionary Relationships
and Taxonomic Classification
•Evolutionary Adaptations
–
Natural selection, the mechanism that drives
evolutionary adaptation, predicts that, on average, only
those individuals that are best adapted to current local
conditions will survive and reproduce, thus donating their
genetically heritable traits to their offspring.
Evolutionary Relationships
and Taxonomic Classification
Fig. 2.3 The basic
components of sexual
reproduction. The
chromosome arrangement of
each cell is shown to the
right.
Evolutionary Relationships
and Taxonomic Classification
• Evolutionary
Adaptations
Evolutionary Relationships
and Taxonomic Classification
• Taxonomy and Classification
– All species that have ever existed on Earth are
classified in a taxonomic system based on their
phylogenetic interrelationships. These systems
are often expressed as branching figures, or
cladograms, that diagrammatically represent
current hypotheses concerning evolutionary
history.
Evolutionary Relationships
and Taxonomic Classification
•Fig. 2.5 A cladogram illustrating the relationships between Sirenians and
elephants and their close relatives based on differences in mitochondrial DNA.
Evolutionary Relationships
and Taxonomic Classification
• Taxonomy and Classification
– Today we follow a system of naming species
that is a modification of nomenclature first
formulated by Linneaus more than two
centuries ago. This system recognizes five
fundamentally different types of living
creatures, or kingdoms: Monera, Protista, Fungi,
Plantae, and Animalia.
Evolutionary Relationships
and Taxonomic Classification
• Fig. 2.7 A phylogenetic tree illustrates the evolutionary
relationships of the major groups of marine organisms.
Trophic Relationships
• Harvesting Energy
– All organisms must acquire energy and matter
to survive, and two sources of each are known
to be used by living creatures.
– Organisms capable of creating their own
organic compounds from inorganic molecules
are autotrophic; those species that must ingest
preformed organics are termed heterotrophic.
Trophic Relationships
Food
Chains and
Food Web
•Fig. 2.12 Energy flow in a marine ecosystem.
Trophic Relationships
•
Food Chains and Food Webs
– Both energy and matter flow through
ecosystems, typically in extremely complex
patterns in the sea termed food webs.
Trophic
Relationships
•Fig. 2.14 A marine food web,
illustrating the major trophic
relationships that lead to an adult
herring. Adapted from Hardy 1924.
The General Nature of Marine
Life
• Unlike terrestrial creatures, marine
organisms exist in a dense, circulating, salty
medium that constantly repositions them
along with their food, waste products, and
offspring.
The General Nature of Marine Life
• Fig. 2.15 Major biotic components of a marine ecosystem with their interconnecting
paths of energy and nutrient exchange. Adapted from Russell-Hunter 1970.
The General Nature of Marine
Life
• Most photosynthetic species in the sea are
microscopic organisms that exist in
concentrations that are thousands of times
more dilute than that observed in a healthy
lawn. Hence consumers that feed on
microscopic particulate matter are much
more common in the sea than on land.