Fundamentals of Biology

• As a universal solvent, water provides the medium in which all other molecules dissolve and interact in the process of life

• Besides water, most of the chemicals that make life possible are organic compounds; compounds that contain carbon, hydrogen, and oxygen

• Organic compounds are high-energy molecules

Fundamentals of Biology• Most organic molecules belong to one of four

main groups:– Carbohydrates (storage and structural sugars)– Proteins (enzymes, hormones, structure, signaling)– Lipids (energy storage, buoyancy, water repulsion)– Nucleic acids (store and transmit genetic info)

The Fuel of Life

• The molecules that make up living things interact in many complex chemical systems

• Most importantly, organisms have to capture, store and use energy (in the form of ATP)

• Two main pathways to process energy:– Photosynthesis– Respiration

Photosynthesis

• Most organisms ultimately get their energy from the sun

• In photosynthesis, algae, plants and other photosynthetic organisms capture the sun’s energy and use it to make glucose, a simple sugar, which is stored, utilized, and/or converted into other organic compounds– Such organisms are called autotrophs

Photosynthesis• Solar energy is captured by pigments such as

chlorophyll and is converted into chemical energy (ATP) which is then used to make glucose out of CO2 and H2O; releasing O2 as a by-product

Respiration

• Organisms that cannot photosynthesize and produce their own food are called heterotrophs

• Heterotrophs must obtain energy from organic matter that was produced by autotrophs

• Both autotrophs and heterotrophs perform respiration to utilize the energy stored in organic compounds by photosynthesis

Respiration

• In respiration, sugars are broken down using oxygen, giving off CO2 and water as a result

• All living organisms respire!

Respiration and Photosynthesis

Respiration: ATP

C6H12O6 + 6O2 6CO2 + 6 H2O

Photosynthesis light energy

6CO2 + 6 H2O C6H12O6 + 6O2

Chemosynthesis chemical energy

6CO2 + 6 H2O C6H12O6 + 6O2

Levels of Ecological Organization

• Populations• Communities• Ecosystems

Levels of Ecological Organization: Population

• A group of individuals of the same species living together in one area; interbreeding

Levels of Ecological Organization: Population

• A group of individuals of the same species living together in one area; interbreeding

Levels of Ecological Organization: Community

• Populations of different species living together in one area; naturally-occurring

Levels of Ecological Organization:Ecosystem

• Communities and non-living components of the environment in which they interact

Challenges of Life in the Sea

• Many adaptations of marine organisms have to do with maintaining homeostasis

• Homeostasis: regulation of an organism’s internal environment to maintain a stable, constant condition (regardless of external conditions)– Salinity– Temperature

Salinity

• Many enzymes and other organic molecules are extremely sensitive to the concentration of ions in solution

• Whenever the internal composition of a cell differs from that on the outside, substances tend to move in or out of the cell by diffusion

• Diffusion – process by which molecules move from areas of high to areas of low concentration

Salinity• Osmosis is the diffusion of water from areas

of high to areas of low concentration• If there is more dissolved material, and

therefore less water inside a cell than outside, water will move into the cell by way of osmosis

• When the outside water is more concentrated than the cell, the cell loses water by osmosis to the external environment

a) More water outside of cell than inside: water moves into cell

b) Same water outside of cell as inside: no movement of water

c) Less water outside of cell than inside: water moves out of cell

Red blood cell

HypotonicHypertonic Isotonic

More solutes; less water

Equal solutes and water

Fewer solutes; more

water

Hypertonic

More solutes; less water

Isotonic

Equal solutes and water

Hypotonic

Fewer solutes; more

water

Hypertonic

More solutes; less water

Cell in a Hypertonic SolutionCell in a Hypertonic Solution

During osmosis, water moves from regions of high to regions of low

concentration

Water molecules move from the red blood cell into the hypertonic solution

The movement of water from the red blood cell causes the cell to shrivel

and shrink.

Cell in an Isotonic SolutionCell in an Isotonic Solution

Since the number of solutes in the cell is equal to the number of solutes in the

solution, there is no net movement of water from or into the red blood cell.

Isotonic

Equal solutes and water

Hypotonic

Fewer solutes; more

water

Cell in a Hypotonic SolutionCell in a Hypotonic Solution

Water molecules move from the hypotonic solution into the red blood

cell.

The movement of water into the red blood cell causes the cell to swell and

eventually burst.

During osmosis, water moves from regions of high to regions of low

concentration.

Images : Copyright © The McGraw-Hill Companies, Inc.

Hypertonic Isotonic Hypotonic

Regulation of salt and water balance

• Generally speaking, marine organisms live in a liquid medium that is more concentrated in ions than that of their internal environments

• Some marine organisms regulate their salt and water balance by doing nothing at all; their internal concentrations change as the salinity of water changes– Such organisms are osmoconformers– Most can live only within a narrow range of salinity

Osmoconformers  Sodium Magnesium Calcium Potassium Chloride

Seawater 478.3 54.5 10.5 10.1 558.4

Jellyfish 474 53 10 10.7 580

Polychaete 476 54.6 10.5 10.5 557

Sea urchin 474 53.5 10.6 10.1 557

Mussel 474 52.6 11.9 12 553

Squid 456 55.4 10.6 22.2 578

Isopod 566 20.2 34.9 13.3 629

Crab 488 44.1 13.6 12.4 554

Lobster 541 9.3 11.9 7.8 552

Hagfish 537 18 5.9 9.1 542Adapted from Potts and Parry 1964 as cited by J. Levinton 2009

Osmoregulators

• Most osmoregulators, however, maintain blood concentrations that are different from that of the surrounding seawater

• Most marine fish have body fluids considerably more dilute than seawater, and so are constantly losing water by osmosis

• To osmoregulate, marine fish drink seawater to replace the water lost by osmosis, and excrete excess salts actively through the gills

Osmoregulation in marine fish

Osmoregulation

• Freshwater fish have the opposite problem; their blood has a higher concentration of salt than does the surrounding water, and are constantly taking in water by osmosis

• To osmoregulate, freshwater fish do not drink and absorb salt through their gills; they also produce large volumes of dilute urine to remove excess water

Osmoregulation in freshwater fish

Osmoconformers vs. Osmoregulators

• Sharks are a special case of osmoregulators– Sharks osmoregulate by changing their internal

concentrations of solutes to match that of their surroundings

– It doesn’t matter if there are the same dissolved chemicals inside & out, so long as the total amount of dissolved material is the same • Sharks or the amount of urea

in their blood

Osmoregulation in marine birds & reptiles• Marine birds and reptiles (and some plants)

have specialized cells or glands to rid themselves of excess salt

Salt glands in action (Southern fulmar)!

Osmoregulation

• Marine mammals osmoregulate by not drinking seawater and excreting highly concentrated urine

Harbor seal kidney

Temperature

• Organisms are greatly affected by temperature• The rate of metabolic, chemical reactions

increase with increasing temperature, and slow down dramatically as it gets colder

• At extremely high temperatures, proteins (including enzymes) denature and cease to function

• At extremely low temperatures, tremendous heat loss can occur, making it difficult to maintain a constant body temperature

Temperature• Most marine organisms are adapted to live

within a particular temperature range• All organisms generate metabolic heat, but in

most organisms this heat is quickly lost to their surrounding environment; such organisms are ectotherms, cold-blooded organisms that are as warm or as cold as their surroundings

Temperature• Other marine organisms retain their metabolic

heat such that their internal body temperatures are higher than that of their surroundings; such organisms are endotherms or warm-blooded

• Endotherms include all mammals, birds, and some large fishes including tuna and sharks, as well as the leatherback sea turtle!

Endotherms in action!

Now to confuse you…

• Another way to categorize organisms is by whether or not they can maintain a constant internal body temperature

• The body temperature of poikilotherms changes with the temperature of the external environment– All ectotherms are poikilotherms– Can make ectotherms sluggish if

the water is colder than they are used to

animals.nationalgeographic.com

Poikilotherms vs. Homeotherms

• Endothermic tunas and sharks are also poikilothermic– Although they retain metabolic heat generated by

their large muscles and are warmer than the surrounding water, their internal temperature still goes up and down as the water temperature changes

• Mammals and birds are able to maintain their internal temperatures even when external temperatures vary; they are homeotherms

Endothermic homeotherms

• Requires a tremendous amount of energy• To reduce the energy cost of maintaining a

constant body temperature, homeotherms are insulated with feathers, hair and/or blubber

Thermoregulation

• Organisms have evolved mechanisms (adaptations) to regulate their body temperature and reduce heat loss to their environment– Changes in surface area to volume ratio– Presence of “antifreeze” compounds– Increase in muscular activity (“shivering”)– Adjusting blood flow to (or away from) skin– Adjusting amount of insulation– Orienting body towards sun

Thermoregulation in action!

http://dive.scubadiving.com/d2d_archive/read.php?f=1&t=920399&a=2&

Counter-current heat exchange

• Some endodermic birds and mammals regulate their internal body temperature by way of a counter-current heat exchange system– Warm blood pumped from within the body is used

to warm the cooler blood returning from the extremities

– Ingenious; blood leaving the warm interior loses its heat to returning vessels just before they enter the (cooler) extremities warming returning blood!

Countercurrent Heat Exchange

As ‘arterial’ blood leaves the body and enters the extremity, it transfers heat to returning ‘venous’ blood, which allows warm blood to re-enter the body, and reduces the loss of heat to the surrounding environment

Common dolphin dorsal fin

Common dolphin dorsal fin

Common dolphin dorsal fin

artery vein

Challenges to Life – Salt Marshes

• Organisms living in salt marshes are also subject to extreme ranges in temperature, exposure/submersion, and salinity

• Characterized by specialized plants (Spartina) capable of surviving in (and then out of) saltwater

http://en.wikipedia.org/wiki/File:Bride-Brook-Salt-Marsh-s.jpg

Challenges to Life – Tidal pools

• Organisms existing in tidal pools are subject to extreme swings in moisture, temperature and salinity

Illustration from "Discover Nature at the Seashore", Lawlor 1992

http://www.nsrwa.org/Page.85.html

Life’s a Beach… or not

• As benign and peaceful as sandy beaches look, they are among the most hostile environments for small organisms

• Sand grains are abrasive and many organisms must have protective coatings and/or be able to burrow below the surface for protection

• In fact, very few organisms survive in wave-swept sandy beaches

www.stripersonline.com/surftalkshowthread.php?t=417951