Spatial Distribution Marine organisms are either pelagic found

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.