Life in the Ocean

1. LIFE IN THE OCEANS - 1

2. Interactions between biosphere, atmosphere, and
hydrosphere
Atmospheric CO2 absorbs solar radiation, and plants consume CO2
If CO2 levels too high, Earth heats up
High CO2 stimulates plant growth
Plants use up CO2, atmospheric levels decrease
Earth cools

3. Interactions between biosphere, atmosphere, and
hydrosphere
Dimethyl sulfide (DMS) used by plankton to control osmotic balance.
In atmosphere, DMS is nucleus for condensation of water vapor
(clouds).
If plankton populations increase, DMS levels increase
cloud formation over ocean increases
reflectivity of atmosphere increases
Earth cools

4. Living things are made of matter
Most abundant elements in all living
organisms are:
C H N O P S

5. Living things are made of matter
What distinguishes living matter from non-living matter?
1. homeostasis: maintain stable internal conditions
2. regulated, controlled growth & development
3. metabolism: controlled chemical reactions that provide
energy for the synthesis of necessary molecules
4. reproduction

6. The cell theory
All living things are made of cells, & all cells arose from other cells.

7. Biological species concept
species: group of actually or potentially interbreeding natural
populations that are reproductively isolated from other such
groups

8. Classification of marine organisms
taxonomy (systematics): study of the classification of and
evolutionary relationships among organisms
binomial nomenclature: system of classification
each species is given latin two-part name: Genus species
devised by Carolus Linnaeus (1750s)

9. Classification of marine organisms
Linnaeus’ system - hierarchy of larger taxa: classification categories
• (Domain)
• Kingdom
• Phylum
• Class
• Order
• Family
• Genus
• species

10. Classification of marine organisms
natural system of classification (cladistic): organisms grouped
together based only on evolutionary relationships, not on
anatomical or behavioral similarities
DNA sequencing important for developing such a system
snakes lizards crocodiles birds
???

11. Classification of marine organisms
natural system of classification (cladistic): organisms grouped
together based only on evolutionary relationships, not on
anatomical or behavioral similarities
DNA sequencing important for developing such a system
snakes lizards crocodiles birds
???

12. Classification of marine organisms
natural system of classification (cladistic): organisms grouped
together based only on evolutionary relationships, not on
anatomical or behavioral similarities
DNA sequencing important for developing such a system
snakes lizards crocodiles birds

13. Convergent evolution
convergent evolution:
development of superficially
similar features in species not
evolutionarily related
anatomical or behavioral

14. Physical factors
physical factors: any aspect of the geological, chemical, or physical
(non-living) environment that affects living organisms.
• light
• temperature
• salinity
• dissolved nutrients
• dissolved gases
• pH
• hydrostatic pressure

15. food webs

16. Light in the oceans
Sunlight is basis of (almost) all oceanic food webs
Different wavelengths penetrate to different depths
depth record for (blue) sunlight: 590m
deep sea—much bioluminescence.

17. Temperature
metabolic rate:
rate at which biochemical reactions occur w/in organism
metabolic rate directly proportional to temperature
until an upper limit
ectotherm: internal temperature close to that of environment
little or no internal regulation of temperature (poikilothermic)
endotherm: actively maintains stable internal temperature
independent of that of environment (homeothermic)
include:
marine mammals, some sharks, large fishes turtles
requires high metabolic rate: more food, greater gas exchange

18. Temperature
Mean global temperature of oceans
= 4ºC
Temperature range is much less than on
land
fewer fluctuations for organisms to
deal with.

19. Salinity
Mean salinity of oceans = 35‰ (range = 0–40‰ )
Salinity varies relatively little.
• rainfall
• evaporation
• freezing
• terrestrial runoff and riverflow
Most marine organisms have salinity within cells similar to that of
seawater.

20. Dissolved nutrients
Concentrations of nutrients in seawater much lower (1/10,000) than
in terrestrial soils.

21. Dissolved gases
Marine organisms require CO2 and O2,
Oxygen is not highly soluble in water. [O2] in water << in air.
CO2 is soluble in water. [CO2] in water > in air.

22. Dissolved gases
[CO2] in deep water > in shallow water.
• no photosynthesis, only respiration
• solubility of CO2 is greater in colder water. Most deep water
originates in polar regions.
• pressure at depth keeps gases in solution

23. Dissolved gases
[O2] can be limiting in shallow water.
• high rates of photosynthesis during day, but high rates of
respiration at night.
• bacterial decomposition of detritus

24. Hydrostatic pressure
hydrostatic pressure: force of the weight of water in the ocean.
atmospheric pressure: force of the weight of air in the atmosphere.
Internal pressure of marine organisms equals hydrostatic pressure,
so not crushed

25. The complexity of physical factors

26. Biological factors
biological factors: any aspect of the biological environment that
affects living organisms.
Symbioses:
• predation + -
• parasitism + -
• competition - -
• mutualism + +
• commensalism + o
• amensalism - o
Interactions between physical factors and living organisms...

27. Diffusion
diffusion: passive net movement of molecules from higher
concentration to lower concentration

28. Osmosis
osmosis: diffusion of water molecules
isotonic: solutions with same concentration of solutes
hypertonic: solution w/ comparatively high concentration of solutes
hypotonic: solution w/ comparatively low concentration
35‰ NaCl 20‰ NaCl
H2O

29. Osmosis and living cells
Most marine organisms are isotonic
to seawater
In freshwater, most organisms are
hypertonic:
water diffuses into cells, organism
expends much energy to expel it

30. Gravity and buoyancy
Density of seawater = 1.025
Density of pure water = 1.000
Most organisms—mean density ≈ seawater.
many fishes have gas bladder
other marine organisms manipulate osmotic balance within tissues to
control buoyancy.
ex: pump out heavy SO4
- ions & replacing them with lighter Cl-

31. Viscosity
viscosity: internal resistance to flow of fluid
Viscosity is affected by temperature & salinity:
• viscosity of water at 0ºC is 25% greater than at 25ºC
• viscosity of saltwater > freshwater

32. Viscosity and movement
drag: resistance to movement of an organism induced by the fluid
through which it swims (or flies).
Drag depends on:
• viscosity of fluid medium
• speed of organism
• shape of organism
• size of organism
Drag is more important for smaller animals, for which viscosity of
water is relatively greater.

33. Viscosity and movement
turbulence: chaotic movement of a fluid around an object.
Turbulence slows movement of organisms, is especially important
for fast-swimming species.
Streamlined shape reduces turbulence.

34. Vertical migration
Many marine organisms move up and down in the water column in
a regular cycle.
• predator avoidance
• nutrient uptake at depth
• take advantage of horizontal currents

35. Classification of marine environment
photic zone: upper layer of ocean that receives sunlight (150-
600m).
• euphotic zone: upper portion of photic zone
photosynthesis exceeds respiration.
• disphotic zone: lower portion of photic zone
respiration exceeds photosynthesis.

36. Classification of marine environment
aphotic zone: layer of ocean below photic zone, no sunlight.

37. Classification of marine environment
pelagic zone: open water above the seafloor
• neritic zone: open water above continental shelf
• oceanic zone: open water beyond continental shelf

38. Classification of marine environment
benthic zone: the seafloor
• littoral zone: intertidal
• sublittoral zone: seafloor to edge of continental shelf

39. Classification of marine environment
benthic zone: the seafloor
• bathyal zone: seafloor of the continental slopes
• abyssal zone: seafloor of the abyssal plains and ridges
• hadal zone: seafloor of the trench walls and floors

40. Classification of marine organisms
pelagic: spend most of their time up in water column
benthic: spend most of their time attached to or on the seafloor
plankton: cannot swim efficiently against a current
nekton: can swim efficiently against a current