Unit 11 The Marine Environment

1. Unit 11The Marine Environment

2. 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 • Video on Bioluminescence

3. Classification of living things • Organisms can be classified into one of three domains of life: • Archaea • Bacteria • Eukarya

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

5. Classification of living things • Taxonomic classification includes the following increasingly specific groupings: • Kingdom • Phylum (Division for plants) • Class • Order • Family • Genus • Species

6. Taxonomic classification of selected organisms

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

8. Plankton: Examples Phytoplankton Zooplankton

9. Nekton: Examples

10. Benthos: Examples

11. Life cycle of a squid • Squid experience benthic, planktonic, and nektonic stages • Squid are considered meroplankton (partially planktonic) • Organisms that spend their entire lives as plankton are holoplankton)

12. 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

13. 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

14. Need for physical support • Condition: • Seawater is denseenough 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

15. 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

16. 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

17. 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

18. Variations in temperature • Condition: • Coastal water temperatures vary more than the open ocean or at depth • 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)

19. 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)

20. Osmosis • Condition: • Osmosis is the movement of water molecules through a semipermeable membrane from lowerto higherconcentrations • Osmosis removes water from hypotonic organisms • Osmosis adds water to hypertonic organisms

21. Osmosis • Adaptations:

22. 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

23. Abundance of dissolved oxygen and nutrients with depth

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

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

26. 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

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