Biology Ecology

Front 1

Positive interactions between species

Back 1

Mutualism (+/+)
Dispersive mutualisms:
Nutritional and defensive mutualisms

Commensalism (+/0)

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Mutualisms

Back 2

Dispersive
Pollination
Seed dispersal
Nutritional and defensive mutualisms
Nitrogen-fixing bacteria
Mycorrhizal fungi
Ants and treehoppers

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Pollination: Specialists vs. generalistsPotential Benefits for Specialists:

Back 3

Plant:
Receives right type of pollen
Pollinator:
More reliable nectar/pollen reward!
Yucca Pollinated only by Yucca moths
Various pollination “syndromes”
Honeybees and bumblebees:generalists or specialists?
Bee-mimicking orchids (Ophrys)

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dispersal agents

Back 4

Wind
Water
Animals
Fleshy fruits
Bur fruits

Front 5

Herbivory.

Back 5

Consumption of plant materials by animals either at the expense of the plants,(+/-) = exploitation herbivory, or beneficial to the plants, (+/+) = mutualistic herbivory. The latter involves eating plant material (fruit, nectar) but dispersing the seeds or pollen.

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Diet

Back 6

Diet includes seeds (granivore), fruits (frugivore), stems, leaves (folivore), buds (browser),
trunk cambium, roots, plant juices and/or sap, algae (algivore), etc.

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Generalizations for herbivores

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1. Food is generally more available for herbivores than it is for carnivores
2. Specializations for a plant diet primarily involve evading the physical and chemical defenses of the plants.
3. The most high-energy plant foods (seeds, fruit, flowers) are generally the least abundant, most widely dispersed plant product.
4. The digestive tract of herbivores, in comparison to carnivores, is much longer and more complex.

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Distinct herbivore tactics

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1. Selection of certain plant parts
2. Make food caches during times of food abundance, as done by numerous species

Front 9

Plant defenses against herbivores

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(Herbivores eat 79% of algae, 30% of aquatic plants, and 18 % of terrestrial plants. Why isn’t more plant material eaten? Why is the world so green? The quick answer: plant defenses. Then, why don’t all plant species have defenses if defending against herbivores is so important? The quick answer: it’s energetically costly to synthesize structural and chemical defenses, and therefore only when herbivory becomes excessive is their strong selection favoring defense mechanisms in a population).

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Mechanical defenses

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a. Tough epidermis: of seed shells; bark on branches and trunks
b. Entanglement devices: thick waxy cuticle and plant hair on leaves and stems entangles and deters small herbivores (e.g., trichomes: enlarged hairs, sometimes with toxic secretion (Fig. 35.18), common in tomato plants).
c. Piercing devices
-Cutting edges in “cutgrass”, a wetland species (silica)
-Spines and needles in many deciduous plants and cacti;

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Chemical defenses

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a. Standing defenses (always present in plants):
b. Inducible defenses: plants increase production of existing chemicals, or synthesize new chemicals, upon attack by herbivores or pathogens

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Standing defenses

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1) Secondary metabolites (derivatives of existing plant metabolism that are
selected for when they discourage herbivores)
2) Indigestible chemicals: Chemicals that render the plant tissues less digestible:

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Secondary metabolites

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a) Phenolics (like tannins in oak leaves, which are substances that nactivate animal’s digestive enzymes; marijuana in animals)
b) Terpenes (mint & lemon oil; pyrethroids in chrysanthemums; pinene in pitch pines that is toxic to bark beetles)
c) Alkaloids (morphine, codeine, caffeine, nicotine, cocaine) cause destructive
behavior in herbivores in large quantities

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Indigestible chemicals:

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a) Cellulose, the greatest deterrent to food value. Except for fungi, some
bacteria, and protists, no organism is able to breakdown cellulose
b) Silica, an indigestible component of grasses, also hurtful to eat (cur grass).
c) Lignin, the most indigestible product of plants, even to bacteria
and most fungi.
d)Tannins are insoluble colloidal compounds that bind to proteins under acid conditions (in animal stomachs) and consequently block protein digestion and
make plant nutrients much less available to the herbivore (oak and hemlock
have high tannin concentrations).

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Herbivore responses to plant defenses

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1. Countering mechanical defenses
2. Countering chemical defense

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Countering mechanical defenses

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a. Tough tongue, mouth and gut, as with cactus-eating tortoises & wood rats, and giraffe who eat the prickly underside and outer crown leaves of Acacia trees.
b. Mastication apparatus and grinding mills to breakdown tough seed coats and resistant tissue: grinding teeth, continually growing teeth, gizzards in birds, regurgitation of cud and re-mastication in many hoofed mammals and rodents)

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Countering chemical defense

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a. Inactivate defense chemicals
b. Form a mutualism with another species that can digest the defense
c. Eat sub-toxic amounts of plants (some primate leaf eaters) and then more on to
another plant species (easy to do in the tropics with a rich diversity of plant species)
d. Eat plant before induced defenses are activated, and then abandon the plant

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Inactivate defense chemicals

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1) Cellulase evolution: many bacteria, protists and fungi (decomposers of plant poducts) have evolved the enzyme cellulase to breakdown cellulose (a defense product) into highly utilizable simple sugars (glucose).
2) Alkaline pH: Ex. Gypsy moth caterpillars have an alkaline (high pH) stomach,
which keeps tannins from binding to protein and making the protein unavailable to the herbivore. Consequently, Gypsy moths eat oak leaves and hemlock bark, both high in tannins, and suffer no loss in protein digestion. The herbivore in this case is one up in the Co-evolutionary Arms Race (p. 1215) between the herbivore and the plant.

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Form a mutualism

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1) Internal (gut symbiosis) of many animals with bacteria and protists that can break down cellulose.
2) External (ant-fungal relationship) (leaf-cutting ant). Ants harvest leaf
Fragments and put them into chambers with a specialized fungus that grows on the fragments and produces excretions of excess simple sugars for the ants. Only the fungus has cellulase for the digestion of plant cellulose.

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Carnivory

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Killing and consumption of other animals (+/-)

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Diet

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includes specialists such as piscivores (fish eaters) and insectivores [notice here the absence of specialization on parts of animals; instead, just different animal groups [animals are just one big fruitcake when it comes to food quality, although there is some preference
when it comes to the order of the tissues consumed, such as brains/head, gonads and guts]

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Generalizations for carnivores

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1. Animals represent a higher quality food item (protein, fat) than plants.
2. Specializations for carnivory are generally different from those for herbivory
3. Animals are seldom known to freely produce parts of themselves as food for some other organism in exchange for some favor or resource (although there are a few exceptions), unlike in plants where mutualistic herbivory (+/+) is common

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Distinct carnivore tactics

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1. Search Image (visual and chemical focus on the most abundant/rewarding prey type while ignoring nearby, but otherwise good, prey, for at least as long as the focal prey is the most economical to take down)
2.Overcoming prey mobility
a.Social carnivory (lions)
b.Pursuit: short distance (cats) or long distance (wolves) dichotomy of adaptations
c.Luring (angler fish lure and snapping turtle tongue)
d.Sit and wait (praying mantis) and surprise pounce/grasp/bite
3. Fat storage (food caches are rare as a means of long-term energy storage, except during
winter by some carnivores burying parcels of meat)

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Prey defenses

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1. Mechanical/behavioral defenses of prey
a.Retaliation: Porcupine quills, sting ray spine, Zebra kick
b.Startling behavior: Under wing moth with hind wing eye spots looking like owl face (also, recall apple maggot fly mimicking a jumping spider)
c.Deflection of attack to non-vital area: 4-eved butterfly fish (eyespots on tail)
d.Large size: elephant, buffalo
e.Death feigning: most carnivores avoid eating aged flesh to avoid toxins/disease of rotted flesh – Hog nose snake, opossum
f.Fleeing: quickly as deer, antelope; Retreat to burrow in ground hogs
g.Crypsis: becoming hard to locate (insect or spider looks like bird dropping on leaf)
h. Clustering (Safety in numbers and confusion effect) (Ex. Grunt fish)

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Armor: Mussel shell thickness, an inducible (genetically plastic) defense

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- Mussel/Crab system (p. 1221-1222):
1) Sites with crabs, mussels have larger shells and stronger attachment
2) Sites without crabs, mussels have thinner shells and weaker attachment
3) Need experiment to conclusively demonstrate the induced defense, because sites with crabs may have more wave action, which may cause thicker shells
4) Experiment in text: chemicals from crabs cause larger mussel shells, so there is a cause and effect relationship between the presence of crabs and thicker mussel shells and stronger attachment

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Chemical defenses of prey

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a. Nausea induction: skunk scent, hydrogen cyanide production by lady bugs
b. Death threat via toxins sequestered from another organism.

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Monarch butterfly. Example of the exploitation of a plant chemical defense

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1) Eggs laid on milkweed, which has few herbivore enemies in old field habitats
2) Larvae (caterpillars) hatch and feed on milkweed leaves, which contain a cardiac glycoside toxic to most herbivores
3) The caterpillar is immune to the toxin, and stores enough in its tissues to deter its
bird predators as well as the bird predators of the adult butterfly produced by the caterpillar.
4) The monarch is aposematic (warning coloration: orange, red black streaks), which warns birds about the bad taste. One experience will cause birds to avoid eating Monarchs.
5) Lincoln Brower showed that naïve (inexperienced) blue jays ate monarchs, only to subsequently vomit up the butterfly and avoid future monarch attacks
6) Viceroy butterflies look like Monarchs but are perfectly palatable. This mimic gains an advantage at the expense of the model (the monarch) in a relationship called Batesian mimicry, where the model is bad tasting and the mimic isn’t.

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Newts & blue-spotted octopus

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Newts & blue-spotted octopus have Tetrodotoxin obtained from a bacteria (most potent neurotoxin known)

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Parasites

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those organisms that in the process of feeding on animals or plants generally reduce the quantity of tissue, but not tissue function, in amounts too small to be life-threatening but which can be substantial enough to have a negative effect on the organism

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Resident parasites

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live-in parasites, often a community of ecto- and endoparasites living and often reproducing in/on a single organism. Ex. tapeworm, fleas, yeast on animals; galls, scale insects of plants. Buffalo Video

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Transient parasites

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periodic visitors looking for a meal, such as mosquitoes, leeches, vampire bats, ticks, soapberry bug; Theoretically, most plant herbivores are plant parasites in the sense that they graze on a plant part without altering tissue function or killing the entire plant

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Pathogens

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anything that causes disease (an often vague and abused term, but generally is the alteration in the normal function of living cells, tissue, organs, or organ systems)

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Characteristics in the context of interactions between organisms

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1. Pathogens use the host as a disposable energy source for its own reproduction and, in the case of animals, dispersal agent
2. The virulence (ability to cause disease) of pathogenic organisms is influenced by the density of the host and, when present, the vector (= another organism that transmits the disease causing microbe to the host)
3. Pathogens often modify the behavior of the host to make them more vulnerable to contact by the vector (Ex., the mosquito in the case of malaria; data show that mosquitoes are highly attracted to individuals inflicted with the disease)
4。Diseases, such as those caused by viruses, are often difficult to control because the high mutation rates of the viruses stay ahead of any immunological responses of its host (Box 34.2)

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The virulence

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a. High virulence. High density of the host/vector allow the rapid spread of the disease before symptoms and even death occur, despite the fact that the host shows almost immediate symptoms and even death (= symptomatic host). The pathogen is not designed by natural selection to reduce virulence to give enough time for disease transmission; the high host density of the host insures almost immediate transmission. (Ex. bird flu).
b.Low virulence. Low host/vector density results in pathogens delaying the onset of the disease symptoms (asymptomatic) in order to insure their transmission to other hosts. These disease organisms are often difficult to eradicate because infected individuals spread the disease widely before their symptoms appear (Ex. AIDS).

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Two case studies involving pathogenic organisms

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1. Myxoma virus: Causes the disease Myxomatosis in rabbits
2. Human Malaria revisited – (Self study; SEE TEXT: 356, 608-609, 1225-1226).

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Myxoma virus: Causes the disease Myxomatosis in rabbits

Back 36

Two hypotheses:
1) Evolution of resistance to Myxoma in rabbits (the initial 0.2 % with resistance were highly selected for)
2) Evolution for decreased virulence in virus, because less virulent forms allowed rabbits to live longer for more mosquito transmission of the disease vs. rabbits who died quickly from the more virulent form of the disease.

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Myxoma virus: Causes the disease Myxomatosis in rabbits

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a) 12 pair of European rabbits were inadvertently introduced into Australia in 1859, becoming a nuisance invasive species there
b)7 years later, 14,253 were shot to control their numbers on a single ranch.
c)Now, 100 million rabbits occur in Australia.
d)Problematic, because raising sheep for wool is an important industry, and rabbit compete with sheep for grass, not to mention with people for all their vegetables
e) Control could be by killing brigades, poison, and introduced predators, all of which can be problematic
f)Introduced the Myxoma virus in 1950, when there were about 600 million rabbits. In South America, this virus is spread by mosquito vectors and causes almost 100% mortality. After introduction into Australia in 1950, it caused 99.8 % mortality of rabbits infected with Myxoma (high virulence).
g)In 1951, only 90% died of those infected
h) In 1952, only 50% died of those infected
i) two hypotheses
j)Experiments were conducted with rabbits exposed to the original virus and the virus in the population with greater survivorship: Hypothesis 2 above accounted for the results.

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Community

Back 38

consists of the living, interacting organisms in a given location. It has an ecological separateness or identity to it as defined by the close networking or interactions among organisms composing it (e.g., parasite and its host, predator-prey interactions, mutualisms)

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Community scale

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very small (e.g., a vernal pool) to large (e.g., a great lake), same as below for ecosystems, but with a focus on just the organisms and their interactions.

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Emergent properties of communities

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e.g. succession: the sequence of recovery of species following species removal as result of a disturbance (e.g., volcanic eruption, land clearing).

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Ecosystem

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a community + abiotic environment. One can study organismal interactions without much attention on the abiotic environment (solar radiation, temperature, minerals, water, etc), although a full understanding of organismal interactions really depends on a concurrent study of the abiotic variables influencing organismal interactions.

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Ecosystem scale: Ecosystems can exist at many different scales

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a. Decaying leaf ecosystem in a vernal pool (a tiny water basin created by spring snow melt and precipitation, but drying up later in the year; e.g., in the BU Nature Preserve)
b.BU Nature Preserve wetland: the multiple beaver ponds and adjacent habitat
c.Watershed (better unit): area of landscape that drains into a particular river/stream
1) Fuller Hollow Creek watershed (the creek fringing BU to the east)
2) Susquehanna River watershed
3)Chesapeake Bay watershed, including other streams/rivers entering the Chesapeake Bay, such as the Potomac River
d.Temperate forest (one of several large regional terrestrial biomes)

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Biome

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Major terrestrial ecosystem defined by global climate patterns and characterized by
distinct assemblages of animals, plants, and regional abiotic variables

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Determinants of global climate pattern

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A. Solar Radiation: causes a cascade of events
B. Earth’s rotation (influences on horizontal air and water mass flow)
C. Seasons: caused by rotation of the earth around the sun and the tilt in the earth’s axis relative to
the sun’s position.
D. Mountains: winds moving toward mountains are deflected upwards, which causes precipitation on the windward side of the mountains and dry (rain shadow) conditions on the leeward side of mountains.

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Solar Radiation: causes a cascade of events

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1. Vertical air mass circulations.
2. Vertical water mass circulation resulting from solar radiation

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1. Vertical air mass circulations.

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a. Most solar radiation at equator causes intense heating at land/sea surface Hot air picks up moisture from ground & sea surfaces (a given volume of heated air can hold more moisture than cold air)
c. Heated air expands, becomes less dense (=hot air balloon effect), rises 6-9 miles up, and becomes cooled in the upper atmosphere, the latter lowering the moisture carrying capacity of air and causing the excess water vapor to condense in the form of precipitation near the equator. Air expansion and uplift also causes equatorial low
pressure areas.
d. Expanding air high in the atmosphere moves pole ward (away from the region of
expansion), and as it cools and becomes more dense, descends at 30 degrees N and S latitude.
e. This relatively dry, descending air becomes even “drier” (lower relative humidity) when it is warmed, and this air pulls moisture out of all objects at the earth’s surface, creating very dry, arid conditions around 30 degrees latitude (deserts).
f.Some of the air at 30 degrees N/S latitude is drawn over the earth’s surface back toward the equator to replace the air that ascended when heated, creating a cyclic circulation of air ┴ to the earth’s surface between 0 and 30 degrees, called a Hadley Cell. This downward flow at 30 latitude causes secondary and tertiary cells poleward: between 30 and 60 degrees (Ferrell Cell) and between 60 and 90 degrees (Polar Cell). They occur both N and S of the Equator, 6 total in all, with the circulation between 30 and 60 degrees being opposite to the others. Where the air rises at the equator and descends at 30 degrees, horizontal air movement is weak, creating stagnant air (and poor sailing) in the “horse latitudes 30 degrees N/S and the “doldrums” near the equator.

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2. Vertical water mass circulation resulting from solar radiation

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a. Solar radiation warms the ocean surface near the equator, and because warm water is less dense than cold water, the warm water stays at the surface, forming a layer of warm, less dense water and a sharp thermocline over colder, more dense water beginning at around 100 m depth.
b.Concurrently, the chilling of polar water and the increased salinity resulting from surface evaporation during chilling increase the density of polar seas and cause the sinking of sea water and its deep flow away from the poles toward the equator.
c.Warm surface water from the equatorial seas is drawn poleward to replace the sinking polar sea water. This combination of events is part of the “engine” that drives the N/S component of the ocean conveyor (global pattern of ocean surface/deep water currents).

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Earth’s rotation

Back 48

Horizontal air mass response to rotation
a. The earth moves from west to east under the atmosphere (and the sun, etc), making the sun appear to be moving from east to west to a stationary object on earth.
b. Poleward of 30 degrees N and S, the surface air is actually moving faster than the earth’s surface and thus is experienced by objects on the earth’s surface (including us at
BU) to be moving from the west (prevailing westerly wind).
c. Polar easterly winds (from the east) occur for the same reasons as the easterly winds near the equator.
2. Horizontal oceanic current components resulting from the earth’s rotation
a. Oceanic surface currents are influenced by the earth’s rotation and surface winds, especially the surface water that isn’t quite accelerated to the earth’s rotational speed.
b. Some of this westward flow is pushed downward off the continental slopes to the sea bottom in a slow but steady west to east deep-sea current.
c. The horizontal velocity of the deflected currents to the north and south eventually exceed the earth’s rotational velocity, creating an eastward surface current beyond 30 degrees N/S of the equator (as with the wind)

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Major Terrestrial Ecosystems (= Biomes)

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A. Tundra (mostly treeless landscape except for miniature trees a couple of feet high: not enough
nutrients/sunlight for much production of woody tissue, which not only doesn’t photosynthesize food, but is a major drain on resources for reproduction).
B. Conifer Forests (i.e., northern boreal forests; almost entirely coniferous, except for larch; low diversity of trees; needle retention lowers nutrient needs for maintenance; allows earlier
photosynthesis in the spring).
C. Grasslands (Prairie, Pampas (SA), Veldt, Steppes)
D. Temperate deciduous forests (mainly between 30 and 45 degrees north)
E. Desert (mostly around 30 degrees north and south latitude, the region of descending air, the horse latitudes)
F. Tropical rain forests (~ within 20 degrees of the equator) most biodiverse: 2/3 of all known living organisms live here)

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Alpine tundra

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a. Moist and cold
b. Pika: stores grass at nest for insulation and food
c. Marmot (high elevation ground hog): reduces reproductive rate and becomes more
social as a means of conserving energy (huddling conserves energy; maturation
takes 3xs longer in high elevation species due to shorter season for growth and
reproduction)

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Arctic tundra (high latitude) generally above ~ 60 degrees North latitude (mostly
above the Arctic Circle at 66 degrees N)

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a. Cold and damp, with low evaporation rates and low precipitation rates
b. Not much vegetation
1) Dwarf birches only 2 inches tall make red tinge on surface of ground
2) Willow tree in full flower is only 1” tall
c. Ptarmigan, Golden Plover: Ground nester with cryptic coloration; small food
supply many mammals flee into the hills during spring to avoid black flies and
mosquitoes in the warmer valleys
d. Resident snowy owls and Arctic fox feed on lemmings
e. Low biodiversity; high carbon stores in permafrost w/o decomposition

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Conifer Forests

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1. Catastrophe prone forests
a. Shallow root growth promotes greater wind throw damage
b. Insect devastation, like spruce budworm, because of high host density (extensive
monocultures of trees) and wind-damaged trees making insect invasion easier
2. Many browsing animals eat needles, leaves, buds and twigs and keep many areas in
early succession: Mule deer, elk, moose are common herbivores
3. Redwood: tallest tree in world, 1st branch at 140’ (taller than all buildings on campus)
4. Giant sequoia (most massive tree in world)
5. Bristle cone pine (oldest tree in world)
6. Spire-shaped trees (spruce/fir) with needles close to ground; reduces wind/snow damage
7. Lynx is typical carnivore, snowshoe hare, a typical mammalian prey; brown bears

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Grasslands

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1. Largely converted to agriculture because of rich soils
2. Warm and dry in general
3. Broadly similar to Arctic tundra in terms of low relief vegetation
4. Wind pollination works here, unlike in the tropical rainforests that depend more on
insects and bats for pollination
5. Fire is important for prairie maintenance and nutrient re-cycling; 1 week after fire,
shoots appear (plants are adapted to fire): e.g., legume plants store nutrients in roots,
allowing for rapid recovery after fire; burrowing is a major life style on the prairie to
escape predator and fire threat (Prairie dog and badger)
6. Ants: very important species for prairie soil conditioning: N-bearing wastes, soil aeration
7. Savannah grassland
a. Mostly dry and warm but highly seasonal rains; some Acacia trees
b. Important in Human evolution – primates came out onto the savanna – upright
walk to look over grass
c. Termite mounds, wildebeest

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Temperate deciduous forests

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1. Most energy is processed with release of CO2 after leaves die and fall in autumn (vs.
when alive during spring and summer when biomass accumulates and energy is stored)
2. Many detritivores, fungi, millipedes
3. Rich soils and thicker humus because of moisture and rich community of decomposers
4. Skunk, raccoon, red fox, white-tailed deer, black bear, deer mouse

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Desert

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1. Dry and hot
2. Varies from total wandering dunes to rugged terrain; some plants and animals with
water conserving structure (e.g., leaves reduced to thorns)
3. Animals like the horned lizard, diamond back rattlesnake and kangaroo rat are
adapted for living in xeric (=~ very dry) conditions; thermoregulatory animal behavior
(avoid mid-day activity)
4. Kangaroo rat never drinks water; all its water comes from its food.

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Tropical rain forests

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1. Complex structure of vegetation
a. Buttress roots – compensate for thin soils resulting from rapid decomposition
b. Big leaves (gather reduced light lower in canopy)
c. Epiphytes (plants living on plants: orchids and bromeliads)
2. Several layers of trees with very tall ones
3. Lots of vines using trees as support (strangler fig)
4. Consumers are mostly arboreal (live in trees), even the ants, termites, herps
(amphibians/reptiles) and many other organisms live more commonly in trees
5. Warm and moist year round – great place for fungi; leaves decay quickly
6. Tremendous selection pressure, such as predation and competition
a. Katydid crypsis of dead leaf shows predation to be a strong selective agent
b. Plant chemical defenses common
7. Sloth, bats, macaw, parrots, cats (margay), tree iguanas, ants, termites

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Aquatic ecosystems

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aquatic biodiversity varies considerably with both global and local factors.
Sunlight penetration, temperature, oxygen availability and nutrient availability are major abiotic
determinants of biodiversity

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Freshwater habitats: Major types and their characteristics and issues

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Vernal pools: Spring thaw puddles in the woods mainly created by “windthrow” toppling of
old trees; dry up by late summer but exist long enough for the life cycle of spotted
salamanders and wood frogs (pools are important for slowing run off of rain water
and snow melt, thus reduce flooding potential…often leveled when land is farmed. Re-
growth woodlands, because of absence of depressions, is more flood prone.
2. Ponds: year round water basins with cattails and a rich amphibian community; natural
ones without fish, lots of water plants and insects; duckweed, red-winged blackbirds
3. Streams (sculpins, minnows)
4. Wetlands (Tannic acid build up from decaying organic vegetation and sphagnum moss),
low pH
5. Swamps (Cypress)
6. Lakes (thermoclines seasonally breakup late in the year with resultant nutrient recycling;
macrophytes in sun-lit littoral zones with many fishes; Fig 50.15; read Box 50.1)
7. Rivers (support many fishes, algal films, macrophytes in shallows

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Brackish water systems (Bays); mixed salt/fresh water; euryhaline fishes; oysters, crabs

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1. Salt Marshes (somewhat isolated, very high salt conditions; salt-tolerant plants and animals)
2. Bays, Estuaries (waterfowl sanctuaries); stratification of freshwater over saltwater

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Marine ecosystems: Major Zones (Fig 50.20)

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1. Intertidal (highest nutrient content, but harshest living conditions: periodic exposure to
dehydration, UV radiation and wave action)
2. Neritic Zones (shore out to continental shelf edge) most accommodating due to more gentle
Water than intertidal, sunlight for photosynthesis, nutrient recycling from bottom; many
organisms have phytoplankton symbionts (flatworms, mollusks, jellyfish, corals)
3. Oceanic

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Oceanic

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a. Mostly nutrient-poor because dead organisms float down below the thermocline to
the ocean floor (Fe is particularly limiting)
b. No attached plants/algae; floating alga Sargassum support mini oases of life.
c. Daily burst of phytoplankton growth with vertical migration of zooplankton
coming to the surface at night to safely feed on the phytoplankton, returning to the
depths at dawn.

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Neritic Zones

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a. Kelp Forests (brown alga) provide safe haven for sea otters, who control sea urchin
densities, but Monterey Bay otters are in decline and the kelp forests are getting
destroyed by sea urchins. Kelp forests require clear, cold (50F), nutrient rich water.
b. Coral Reefs (Cnidarian organisms: jellyfish, sea anemones, hydrozoans, corals)
coral polyps build CaCO3 skeletons (reefs) that provide structural support for the
second most biodiverse habitat known next to rainforests; recent CO2 build up is
creating acid conditions not favorable for CaCO3 precipitation. Water too warm above
~ 85F and too nutrient rich kills corals, one reason being that nutrient rich water
mainly causes excessive algal growth and blocks of the sun required by corals
(some Hawaiian bays when nutrient-rich sewage was dumped into the bays)