Oceans

The diversity of marine life The ocean is home to a wide variety of organisms Marine organisms range from microscopic bacteria and algae to the largest animal in the world (blue whale) Number of known marine species: 250,000

Classification of living things Organisms can be classified into one of three domains of life: Archaea Bacteria Eukarya Figure 12-1

Classification of living things Organisms can also be classified into one of five kingdoms: Monera Protoctista Fungi Plantae Animalia

Classification of living things Taxonomic classification includes the following increasingly specific groupings: Kingdom Phylum Class Order Family Genus Species

Taxonomic classification of selected organisms Category Human Killer whale Giant kelp Kingdom Animalia Protoctista Phylum Chordata Phaeophyta Subphylum Vertebrata Class Mammalia Phaeophycae Order Primates Cetacea Laminariales Family Hominidae Delphinidae Lessoniaceae Genus Homo Orcinus Macrocystis Species sapiens orca pyrifera

Classification of marine organisms Marine organisms can be classified into one of three groups based on habitat and mobility: Plankton (floaters) Phytoplankton (drifting plants and algae) Zooplankton (drifting animals) Nekton (swimmers) Benthos (bottom dwellers)

Plankton: Examples Phytoplankton Zooplankton

Nekton: Examples

Benthos: Examples

Life cycle of a squid Could something be part of all three types? Yes! Squid experience benthic, planktonic, and nektonic stages

Distribution of species on Earth The land has more species because it has greater environmental variability than the ocean Most ocean species are benthic because of greater environmental variability compared to pelagic environments Pelagic means to be surrounded by water (not near the shore or on the bottom)

Adaptations of organisms to the marine environment The marine environment presents many challenges to organisms because seawater: Is dense enough to support organisms Has high viscosity Experiences variations in temperature and salinity Contains variable amounts of dissolved gases Has high transparency Has a dramatic change of pressure with depth Marine organisms have various adaptations for the conditions of the marine environment

Need for physical support Condition: Seawater is dense enough to support marine organisms Adaptations: Many marine organisms lack rigid skeletons, appendages, or vast root systems Instead, they rely on buoyancy and friction to maintain their position within the water column

Seawater’s viscosity controlled by temperature Condition: Seawater’s viscosity (resistance to flow) is strongly affected by temperature Cold water has higher viscosity than warm water, so is more difficult to swim through Warm water has lower viscosity, so organisms tend to sink within the water column

Seawater’s viscosity controlled by temperature Adaptations: Many warm-water organisms have ornate appendages to stay afloat Many cold-water organisms are streamlined to swim more easily Warm-water copepod Cold-water copepod

Seawater’s viscosity and adaptations of phytoplankton Condition: Phytoplankton must remain in sunlit surface waters Adaptations: Small size increases surface area to volume ratio Appendages increase frictional resistance Tiny droplet of low density oil increases buoyancy

Variations in temperature Condition: Coastal (shoreline) water temperatures vary more than out in the open ocean or in deeper waters Adaptations: Many coastal organisms can withstand a wide temperature range (are eurythermal) Most open ocean and deep-water organisms can withstand only a small temperature range (are stenothermal)

Variations in salinity Condition: Coastal environments experience greater salinity variation than the open ocean or at depth Adaptations: Many shallow-water coastal organisms can withstand a wide salinity range (are euryhaline) Most open ocean and deep-water organisms can withstand only a small change in salinity (are stenohaline)

Effects of Salinity Cell membranes are affected by the salinity of the water inside and outside of them. Hypotonic Hypertonic Isotonic

Osmosis Condition: Osmosis is the movement of water molecules through a semipermeable membrane from higher to lower concentrations Osmosis removes water from hypotonic organisms Osmosis adds water to hypertonic organisms

Osmosis Adaptations:

Dissolved gases: Oxygen Condition: Marine animals need oxygen to survive Adaptations: Many marine animals use gills to extract dissolved oxygen from seawater Marine mammals must breathe air

Abundance of dissolved oxygen and nutrients with depth

Seawater’s high transparency Condition: Seawater has high transparency Adaptations: Transparency Camouflage Countershading Migration (DSL) Camouflage Countershading

The deep scattering layer (DSL) Organisms within the deep scattering layer undertake a daily migration to hide in deep, darker waters during daytime

Increase of pressure with depth Condition: Pressure increases rapidly with depth Adaptations: Most marine organisms lack large compressible air pockets inside their bodies Water-filled bodies exert the same amount of pressure as is pushing inward, so marine organisms do not feel the high pressure at depth

Divisions of the marine environment Main divisions: Pelagic (open sea) Benthic (sea bottom)