Ecology: The study of the interrelationships between plants and animals and their environment. The term environment includes the sum total of physical and biotic conditions and influences that surround an organism or population of organisms.

• Physical Environmental Factors: These relate to climatic conditions of terrestrial, freshwater and marine ecosystems; including light, temperature, water (precipitation), substrate (soil), mineral nutrients, topography & terrain, atmospheric gasses, currents, fire, etc. The study of freshwater ecosystems is limnology and the study marine ecosystems is oceanography.

• Biotic Environmental Factors: These relate to the presence of other organisms, including pollination, insect-flower relationships, predator-prey relationships, seed dispersal, scavenging, symbiosis (mutualism, parasitism & commensalism), overgrazing, overpopulation, animal behavior, mimicry (Batesian & Mullerian), aposematic coloration, nitrogen fixation etc.

Life Zones: In 1898, C. Hart Merriam proposed six major North American life zones based primarily on temperature relative to altitude. Each zone has a characteristic flora and fauna associated with the climate of that particular elevation zone. The six zones are: (1) Lower Sonoran (Central Valley of California and the southwestern desert region); (2) Upper Sonoran (foothill oak woodland of the western Sierra Nevada and the sagebrush scrub & pinyon-juniper woodland east of the Sierra Nevada); (3) Transition (yellow pine forest and coastal redwood forest); (4) Canadian (lodgepole pine forest and red fir forest of the Sierra Nevada; (5) Hudsonian (subalpine forests of whitebark pine and mountain hemlock); (6) Arctic-Alpine (alpine fell-fields of the Sierra Nevada and tundra meadows above timberline). The zones are named after latitudinal regions, including Sonora, Mexico, Canada, Hudson Bay and the Arctic Tundra. An altitudinal increase of 1,000 feet is roughly equivalent to a latitudinal change of 600 miles. In terms of the climate and the flora and fauna, a trip northward of 600 miles is roughly similar to an elevation change of 1,000 feet. Low desert valleys are similar to Sonora, Mexico, while high elevation subalpine forests are similar to the Hudson Bay region. For example, the bottom of the Grand Canyon in Arizona is Lower Sonoran, while nearby subalpine forests on the San Francisco Peaks are Hudsonian. In southern California, the timberline on Mount San Gorgonio (11,000 feet) has a subalpine flora similar to the Hudson Bay region 6,600 miles to the north (11 x 600 = 6,600). The lodgepole pine forest on Mount San Gorgonia (9,000 feet) has a flora reminescent of the Canadian Life Zone 5,400 miles to the north (9 x 600 = 5,400).

Although the life zone classification works reasonably well on the west side of the Sierra Nevada, it has some major discrepancies on the east side of the range. Here the Upper Sonoran meets the Canadian in some places with no Transition in between. Also, some animals that occur separately in Upper Sonoran and Transition on the west are mixed together on the east side. Almost all of the plants of these zones are different on the two slopes of the range. For these reasons, most regional floras use other vegetation classification systems, such as plant communities rather than life zones.

Food Web: A complex pattern of interconnected food chains in a community. The organisms are typically connected by arrows that show the direction of energy flow.

Trophic Level: A level of nutrition or "link" in a food chain. In accordance with the Second Law of Thermodynamics, food chains seldom have more the six links.

Producers: Autotrophic photosynthetic plants that occupy the first trophic level of a food chain.

Autotrophic: Mode of nutrition in which the organism is able to synthesize its own energy-rich carbohydrate molecules. ATP must be generated first in order to synthesize the carbohydrates. This includes green photosynthetic plants and chemosynthetic (chemoautotrophic) bacteria. Photosynthetic bacteria utilize light energy and include purple sulphur bacteria and halobacteria. Chemoautotrophic bacteria obtain energy (ATP) from the oxidation of elements in their environment. Examples of chemosynthetic bacteria include sulphur bacteria, iron bacteria and the remarkable bacteria responsible for desert varnish. Nitrifying bacteria oxidize ammonia from decay into nitrites, water and ATP.

Heterotrophic: Mode of nutrition in which an organism is unable to synthesize its own energy-rich carbohydrate molecules, and is parasitic or saprophytic on other organisms. Parasitic heterotrophs live on other living organisms, while saprophytic heterotrophs depend on dead, decaying organic matter. There are many species of parasitic and saprophytic bacteria and fungi. Saprophytic decay bacteria and fungi are essential decomposers which recycle vital nutrients back into the ecosystem. Parasitic bacteria that cause human diseases are termed pathogenic. Some flowering plants called mycotrophs obtain their energy-rich molecules from soil fungi that in turn parasitize the roots of forest trees. This complex symbiotic fungus-root relationship is called mycorrhizae.

Lichen: A symbiotic relationship between an alga (autotrophic phycobiont or photobiont) and a fungus (heterotrophic mycobiont). This type of symbiotic relationship is mutually beneficial to both organisms.

Primary Consumers: Plant eaters (herbivores) that occupy the second trophic level of a food chain.

Herbivore: An animal the eats herbage or plant material. The largest animals on land today are herbivores. The largest dinosaurs were also herbivores.

Granivore: A herbivore (such as a rodent) with a diet primarily of grains and seeds.

Omnivore: An animal that eats both plant and animal material. There is some disagreement among biologists (especially vegetarians), but humans are probably omnivores rather than carnivores or herbivores.

Insectivore: An predatory animal (such as a shrew or bat) with a diet consisting chiefly of insects.

Carnivore: An animal that feeds on the flesh of other animals.

Secondary Consumers: Carnivorous animals that occupy the third trophic level and feed on the herbivores of the second trophic level.

Predator: An animal that kills and feeds upon another animal. There are some rare cases where an animal actually kills and eats its mate (after mating), such as the Australian redback spider and preying mantis.

Prey: An animal that is hunted and killed for food by another animal.

Tertiary Consumers: Larger carnivores of the fourth trophic level that kill and eat the smaller carnivores (and herbivores) of the third and second trophic levels.

Biology students often ask whether the developing embryo (and later the fetus) within the uterus is parasitic on its mother. Under a strict definition of symbiosis, the parasite and its host typically belong to different species. However, under a general definition of a parasite, the embryo derives sustentance from the host (mother). Although the mother is not usually harmed, there are cases when the pregnancy causes serious (life threatening) complications. R. N. Nesse and G.C. Williams (Why We Get Sick, 1994) discuss the parasitic nature of the human fetus in their chapter on pregancy (pp. 197-200). The fetus (and placenta) secrete several potent hormones into the mother's blood stream in order to benefit itself at the expense of the mother's health. Human placental lactogen (hPL) ties up maternal insulin so that blood glucose levels rise and provide more glucose to the fetus. If the mother happens to be deficient in her production of glucose, this can cause gestational diabetes, possibly fatal to the mother. The placenta also makes several substances that can constrict arteries throughout the mother's body. High blood pressure during pregnancy is called preeclampsia when it gets severe enough to damage the kidneys. During the early stages of pregnancy, the developing placental tissue destroys uterine nerves and arteriolar muscles that adjust blood flow, and this makes the mother unable to reduce the flow of blood to the placenta. Human chorionic gonadotropin (hCG) is another hormone secreted by the fetus. It binds to the mother's luteinizing receptors and stimulates the continued release of progesterone from the mother's ovaries. This hormone blocks menstruation and lets the fetus stay implanted on the wall of the uterus.

There are many remarkable examples of mutualism between species of animals, plants, protists and cyanobacteria. Unicellular algae called zooxanthellae live within the bodies of marine invertebrates, including sponges, jellyfish, sea anemones, corals, gastropods and turbellarians. The photosynthetic activity of these symbiotic algal cells is vital to the survival of the individual coral animals and to the entire reef ecosystem. The zooxanthellae include several species of unicellular algae in the order Zooxanthellales within the algal division Pyrrophyta (also spelled Pyrrhophyta). No other ecosystem other than the tropical rain forest rivals coral reefs in terms of complexity and productivity. The term zoochlorellae refer to several species of symbiotic unicellular green algae of the division Chlorophyta. Along the Pacific coast of North America, zoochlorellae produce the greenish color in sea anemone tentacles. There are many references in Wayne's Word about symbiosis, including the fig and fig wasp, yucca and yucca moth, acacia and acacia ant, azolla fern and cyanobacteria, and many others. See the table of Wayne's Word hyperlinks below:

Symbiogenesis: New Species From Genomic Mergers Long-term stable symbiotic relationships between two or more organisms may lead to evolutionary change. This phenomenon, known as symbiogenesis, is described in the book entitled Acquiring Genomes: A Theory of the Origins of Species by L. Margulis and D. Sagan (2002). According to the authors, genomic mergers are a major source of genetic variability leading to the evolution of species. Instead of relying on the hit-or-miss method of random mutations, symbiogenesis provides advantageous genetic combinations through the fusion of entire genomes from two or more organisms. This phenomenon may have been a major factor in the evolution of land plants from lichen-like ancestors. Endosymbiont Hypothesis: The Evolution Of Chloroplasts The arise of photosynthetic organelles called chloroplasts represented a major step in the evolution and diversification of plant life on earth. This event had a significant effect on the evolution of animal life that depended on the plants for food, either directly in the case of herbivores, or indirectly in the case of carnivores. Chloroplasts exibit remarkable similarities with cells of cyanobacteria, and may have shared a common prokaryotic ancestry. Indeed, the outer membrane structure and circular DNA molecules of chloroplasts and mitochondria are very similar to individual prokaroytic cells. According the the endosymbiont hypothesis (or endosymbiont theory for those who are less skeptical), ancient photosynthetic prokaryotic cells became incorporated within the cells of algae or ancestral plants, forming stable mutualistic symbionts known as chloroplasts. Mitochondria may have had a similar origin. Without chloroplasts and oxygen-producing photosynthesis, the amazing diversity of today's plants and animals would not have evolved. See Mimivirus & The Origin Of A Protonucleus According to Margulis and Sagan (2002), there is even a green photosynthetic animal named Elysia viridis, a minute slug (saccoglossan opisthobranch) that never feeds throughout its adult life. Instead, it obtains carbohydrate-rich molecules by bathing in the sunlight. This slug evolved from algae-eating ancestors, only the algal cells entered the slug's tissue and remained their as photobionts (photosynthetic symbionts). According to some invertebrate zoology textbooks, the chloroplasts from algae cells are sucked into the slugs's gut and incorporated within digestive gland cells where photosynthesis occurs. There are numerous examples of plants and animals that contain microbial symbionts within their tissues, including bacteria, cyanobacteria, protozoans and algal cells. Cycads, water ferns (Azolla), legumes and the tropical flowering plant Gunnera contain nitrogen-fixing bacteria in their tissues; sea anemones and corals contain photosynthertic unicellular algae (zooanthellae and zoochlorellae); the rumen of cattle contain cellulose-digesting bacteria; termite guts contain flagellated protists which contain wood-digesting bacteria; and human intestines contain bacteria that produce essential B vitamins. Lichens are one of the best examples of symbiogenesis involving the fusion of algal and fungal genomes (kindoms Protista and Fungi). Some lichens include the genome of a third kingdom Monera because they contain prokaryotic cells of cyanobacteria. In the case of lichens, this genomic merger has enabled these organisms to survive in some of the most inhospitable environments on earth, where neither symbiont could survive on its own. In fact, lichens are an excellent example of synergism because the whole is truly greater than the sum of its parts. The algal and fungal components develop into a unique body form with morphological features quite different from either symbiont. British soldiers (Cladonia cristatella), a soil lichen with upright podetia bearing bright red apothecia at the tips. At the bottom of the centrifuge tube (left), the fungal component of this lichen (also named C. cristatella) has grown into a white, amorphous blob without its algal symbiont. In the right test tube, the algal symbiont (named Trebouxia erici) has grown into a mass of bright green cells. Only when these two symbionts form the "marriage" known as lichen is the unique structure of "British soldiers" formed. In true synergistic fashion, the lichen is truly more than the sum of its parts. For example, the podetium is a unique lichen structure that is not found in the algae or fungi. Lichens and The Evolution of Land Plants Lichenization, the process by which fungal hyphae and algal cells literally grow together to form a mutualistic association, may help to explain the remarkable evolution of vascular plants on earth. Most textbooks of general botany suggest that land plants evolved from ancestral green algae. However, some authorities believe that vascular plants are far more than simple extensions of green algae. They are comparatively too complex, diversified too quickly, and contain numerous fungus-like cells. In his fascinating article "Are Vascular Plants Inside-Out Lichens" (Ecology 69 (1): 17-23, 1988), Peter Atsatt of the University of California, Irvine discusses some of the evidence supporting a lichenized ancestor to vascular plants. According to Dr. Atsatt, the ancestral lichenization resulted in a "reverse-phase lichen" with a dominant algal component containing an endophytic, mineral scavenging fungus similar to extant mycorrhizal associations. Nuclear fusions between the fungal and algal cells resulted in hybrid nuclei containing the traits of both parents. In true synergistic fashion, this dual genome gave rise to a plant body composed of a mosaic of alga-like photosynthetic cells interspersed with specialized fungus-like cells. Probably the most difficult concept for skeptical botanists to accept is the fungal ancestry in today's vascular plants. Dr. Atsatt discusses several types of cells and tissues in vascular plants which resemble fungal hyphae, including pollen tubes, vascular (xylem) tissue, laticifers, and haustoria. Pollen tubes not only resemble the growth of fungal hyphae, but in Pinus, cycads, and Ginkgo they are branched and actually absorb nutrients from the "host's" megasporangium. The latex-producing laticifers found in many members of the Euphorbiaceae, Asclepiadaceae and other dicotyledonous families are very similar to fungal hyphae. Nonarticulated laticifers are elongate, multinucleate cellular tubes that grow throughout the plant body of these families. Some endophytic parasitic flowering plants, such as certain dwarf mistletoes and the remarkable Pilostyles thurberi of the Colorado Desert, live completely within the host tissues and only emerge from their host to produce flowers. The vascular tissue of these endoparasites literally permeate the host tissues and truly resemble fungal hyphae. The absorptive haustorial organs of many parasitic flowering plants which penetrate the host tissue are also very reminiscent of fungal hyphae. Although there is ample fossil evidence suggesting that algae and fungi lived over 500 million years ago, there is little fossil evidence of true ancestral lichens from that era. However, a startling new hypothesis from Gregory Retallack of the University of Oregon may shed some light on the existence of Precambrian lichens. Since their discovery in southern Australia in the late 1950s, the fossil remains of the Ediacaran biota have puzzled paleobiologists. These strange, flattened creatures lived about 600 million years ago presumedly at the bottom of shallow coastal seas. They have been classified in several primitive animal phyla, from jellyfish, echinoderms and worm-like animals to large alga-like protists, and may have been ancestral to other animal phyla. A number of paleontologists refer to these organisms as "Vendobionta," and regard them as an extinct early experiment in the evolution of life. By about 530 million years ago they were all replaced by shelled Cambrian animals. But according to Dr. Retallack, these bizarre creatures may have been ancient lichens. In his fascinating article "Were the Ediacaran Fossils Lichens?" (Paleobiology 20 (4): 523-544, 1994), Dr. Retallack eloquently discusses the evidence supporting his lichen hypothesis. Comparing their thickness to that of much younger tree-trunk fossils, he concludes that the fossils resisted compaction after burial almost as well as sturdy logs. Their sturdiness, large size (up to one meter across), lack of any mouth, digestive cavity or musculature, and evidence from their microscopic examination all suggest to Retallack that Ediacaran fossils were lichens. The presumed marine habitats of Ediacaran fossils is not crucial to their interpretation as lichens, because rock lichens live in the sea and on land. If one can hypothesize that at least some of the Ediacarans may be ancestral to certain animal groups, then perhaps lichens gave rise to more than vascular plants! According to Blair Hedges of Pennylvania State University (Science, August 2001), aquatic fungi evolved into a terrestrial form about 1.3 billion years ago. These early fungal forms were actually lichens because they formed a symbiotic relationship with primitive aquatic green algae. The early land surface of the Earth at this time contained numerous colorful rock lichens. The bright pigments served to reduce the harmful effects of ultraviolet radiation in a primitive atmosphere. Evidence from mutation rates in 119 genes common to living fungi and plants, indicates that ancient moss-like land plants appeared about 700 million years ago. Lichens are far more than mere biological curiosities. They are very successful and unique life forms that may hold the secrets to complex evolutionary processes, cell differentiation and gene expression in vascular plants.

Biodegradable: Chemicals or compounds that decompose or break down into biologically useful elements through the action of normal decay processes, such as decay bacteria and fungi. Non-biodegradable products (such as certain plastics and polymers) do not break down under normal decay processes. Some of these non-biodegradable chemicals (such as PCBs) are also toxic to the environment.

Organically Grown: Plants grown without the use of toxic chemical herbicides, fungicides and insecticides. Organically grown also involves the use of natural fertilizers derived from matter of living origin, such as barnyard manure, green crops turned under and incorporated with the soil, compost, humus and natural leafmold, bonemeal, cottonseed meal, fish scrap, etc. Organically grown is distinguished from plants grown using commercially manufactured, concentrated fertilizers derived from mineral or inorganic origin (such as ammonium nitrate, ammonium sulfate, etc.).

Plants which are restricted to one or more specific localities within a region are termed endemic. For example, the Torrey pine is native as well as endemic to California. Although commonly cultivated, it only grows wild on the sandstone bluffs between Del Mar and La Jolla in San Diego County, and on Santa Rosa Island. Because of the many isolated mountain ranges and valleys in California, approximately 30 percent of the flora is endemic to the state. Some endemic plants in California include the California cypresses (Cupressus), Santa Cruz Island ironwood (Lyonothamnus floribundus ssp. asplenifolius), Death valley sage (Salvia funerea), Death Valley locoweed (Astragalus funereus), Panamint daisy (Enceliopsis covillei), Orcutt's woody aster (Xylorhiza orcutii) and Death Valley gilmania (Gilmania luteola). Death Valley is especially rich in endemics because of its isolation from other regions. It is surrounded by high mountain ranges and hundreds of miles of arid desert. In fact, one of the rarest endemic wildflowers in California is called "rock lady" (Maurandya petrophila), a member of the snapdragon family (Scrophulariaceae). This unusual plant grows in crevices on vertical limestone walls in steep canyons of the Grapevine Mountains bordering Death Valley.

The Hawaiian Islands have many endemic plant and animal species, although most of the islands have been replaced with aggressive introduced species. For example, the remarkable silver sword (Argyroxiphium sandwicense ssp. macrocephalum) only grows within and near the rim of 10,000 foot Haleakala Crater on the Island of Maui. Another subspecies of silver sword (A. sandwicense ssp. sandwicense) grows on the upper slopes of Mauna Kea on the island of Hawaii.

Naturalized: True naturalized plant species are introduced from another region (outside California). Because they are able to grow wild and reseed themselves, they are considered part of the California flora. Some naturalized species are considered very destructive to the natural environment because they are extremely invasive and may replace the native species. This is especially serious when the loss of native plants threatens the survival of native animals that depend on the plants for food. Naturalized plants that are considered undesirable are often referred to as weeds. It has been estimated that more than 12 percent of the California flora is composed of naturalized "weedy" species. Examples of naturalized plants are red gum (Eucalyptus camaldulensis), tumbleweed (Salsola tragus), puncture vine (Tribulus terrestris), castor bean (Ricinus communis), poison hemlock (Conium maculatum), pampas grass (Cortaderia jubata), common reed (Phragmites australis), annual grasses (Avena, Hordeum and Bromus), and wild mustards (Brassica and Raphanus). Naturalized "weeds" often have ingenious methods of dispersal, including hitchhiking on animals and airborne seeds. A single tumbleweed plant may produce 20,000 to 50,000 seeds within numerous small fruits, each surrounded by a circular, papery border. Mature plants readily break off at the ground level and are pushed along by strong gusts of wind. As they roll along hillsides and valleys, the seeds are scattered across the landscape.

Many California weeds were originally introduced near the harbors of coastal cities. Ships coming to the United States from other countries often carried rocks and soil as ballast to stabilize the ships while at sea. Upon reaching a California port the ballast was emptied from the ships at dockside. Alien weeds also arrived in contaminated seed mixtures (such as grains) and contaminated wool or other textile products. Some of the earliest records of exotic plants in California began in 1796, when Father Junipero Serra reached San Diego Bay and founded the first permanent European settlement in Alta California. During the establishment of the California missions, seeds of European mustards were scattered by early pioneers as they traveled between the missions. The bright yellow mustards marked the pathway for travelers the following spring.

Another Mediterranean mustard (Brassica tournefortii) has found its way to desert areas of southern California, particularly Borrego Valley in San Diego County. This annual mustard grows rapidly in early spring and literally takes over fields that once supported populations of colorful annual wildflowers. After the unusually heavy spring rains of 2005, this mustard dominated most of the open fields north and east of Borrego Springs. If it is not controlled, many of the spectacular wildflower areas near Borrego Springs may transform into fields of mustard.

Naturalized plants often grow very well in disturbed sites, and this is how some of California's most noxious weeds were introduced. The earliest reported collection of puncture vine in California was made at Port Los Angeles in 1903, presumably the result of a ballast dump. Within a few decades it had spread throughout the state, reaching epidemic proportions in some cultivated valleys. The burs were carried in the wool of sheep, in hay, straw, other feed, manure, melons, alfalfa, cotton, potatoes, picking sacks and boxes, tents, sand, gravel, farm and industrial machinery, and in rubber tires of automobiles and airplanes. Puncture vine is the scourge of every bicyclist and is a major factor in the popularity of inner tube repair kits.

Puncture vine belongs to the caltrop family (Zygophyllaceae), so named because of the shape of the wicked fruits. At maturity, the fruit dries and breaks apart into five seed-bearing sections called carpels. Each section is armed with several sharp spines that readily penetrate bicycle tires or your shoes.

During medieval times, a vicious weapon called a caltrop was used in European warfare. This was an iron device with four points so designed that one was always facing upward, whichever way it landed, to impale the hooves of enemy cavalry horses. A similar device was also used in World War II to destroy truck tires on enemy supply convoys. The widespread water caltrop (Trapa natans) also has a four-pronged fruit that resembles a caltrop.

Another European weed that can easily puncture bicycle tires and bare feet is star thistle (Centaurea solstitialis). The involucre below each yellow flower cluster is composed of overlapping bracts (phyllaries), each tipped with a slender spine. Like numerous other members of the enormous sunflower family (Asteraceae), this noxious weed produces "parachute seeds" (each with a tuft of hairs) that become airborne with the slightest gust of wind. A yellow-flowered species with shorter spines (C. melitensis) is naturalized in disturbed areas of southern California, including the hills adjacent to Palomar College. A purple-flowered perennial species without involucral spines is called Russian knapweed (C. repens). The latter species is listed under the genus Acroptilon in the Jepson Flora of California, 1993. Although the genus includes some of the worst weeds in California's pasturelands, it also includes some popular garden ornamentals, such as "dusty miller" (C. cineraria).

Numerous exotic ornamentals from other countries have been propagated for erosion control, rapid growth, fire wood or other purposes, sometimes with disastrous consequences. One of California's naturalized trees, the Brazilian pepper (Schinus terebinthefolius), is a very serious problem in the Florida Everglades. This species has spread rampantly throughout miles of valuable swampland and is a threat to the native flora and wildlife. Another aggressive vine that has literally taken over large areas of land in the southeastern United States is the kudzu vine (Pueraria lobata). Seemingly harmless house plants in California have become serious weeds in the tropical Hawaiian Islands, replacing much of the original native vegetation.

Naturalized species are not limited to land plants. An ecological disaster can also be caused by the introduction of alien "weeds" into the marine ecosystem. In the summer of 2000, the Mediterranean green alga Caulerpa taxifolia (division Chlorophyta) was discovered growing in Agua Hedionda Lagoon south of Carlsbad, and at Huntington Harbor in Orange County. When introduced into a non-native marine habitat, this alga rapidly spreads across ocean bottoms as a smothering blanket of intricate, feathery blades and a dense network of stolon-like outgrowths, covering and killing all native aquatic vegetation in its path. Fish, invertebrates, marine mammals, and water fowl that are dependent on native marine vegetation are displaced or die off from the areas where they once thrived. To make matters worse, it is toxic to animals that feed on algae, such as sea urchins and marine mollusks. Because of the devastation caused by this seaweed, it has been referred to as "killer algae." It is capable of growing one inch per day, and it spreads readily by fragmentation. Even a small piece can grow into a new plant. It can readily be transported to new areas via boat anchors and fishing gear. Caulerpa has been commonly grown in aquaria and may have been inadvertently discarded into southern California waters.