Lab Manual Exercise #10

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Ecological Principles #1

Go To Ecological Principles #2

Table Of Contents:

    1.   Ecosystem, Biome, Life Zones
    2.   Food Chains & Food Webs       
    3.   Symbiosis: Living Together       
    4.   Biological Magnification
    5.   Biological Control
    6.   Native vs. Naturalized
    7.   Thermodynamics
    8.   Energy Pyramids
    9.   Plant Succession
  10.   Food Productivity
  11.   Adaptations Links
  12.   Some Definitions
          A.  Plant Adaptations
          B.  Animal Adaptations
  13.   Major Biomes of N. America
  14.   Photographs Of Adaptations
  15.   Principles of Population Growth

1. Biomes, Ecosystems & Life Zones

Biome: A large geographical region whose climate produces a characteristic climax association of plants and animals. The term biome usually refers to terrestrial habitats (on land). In North America there are about six major biomes. Aquatic ecosystems, such as the ocean, are often subdivided into different zones, such as the intertidal, pelagic, benthic, photic and aphotic zones.

Plant Community: An assemblage or association of certain dominant indicator species occupying a given region. In California the desert biome consists of several different plant communities, such as the creosote bush scrub, shadscale scrub, sagebrush scrub, Joshua tree woodland and pinyon-juniper woodland. The local chaparral and coastal sage scrub plant communities surrounding Palomar College are considered part of an arid desert biome. Some general biology textbooks have added a seventh biome called the "shrubland biome" to encompass these brushy habitats.

A coastal salt marsh plant community in San Diego County as seen from the bluffs of Torrey Pines State Park. These lowland extensions of river deltas are very valuable wildlife habitats. The dense vegetation of coastal marshlands provides a nesting and breeding habitat for marine birds, and a vital breeding habitat for species of small fish and crustaceans.

Ecosystem: All of the organisms in a natural community or biome plus all of the associated environmental factors with which they interact. The term ecosystem could actually be applied to any of the terrestrial biomes or plant communities. For example, the tundra biome could also be referred to as tundra ecosystem; the chaparral plant community could also be referred to as the chaparral ecosystem. The term ecosystem is well-suited for aquatic communities such as ponds, lakes, streams and even the ocean. In fact, oceanography is the study of the ocean ecosystem. Including ocean, topsoil and atmosphere, the earth is a large, complex ecosystem called the biosphere; however, in terms of the vast universe it is but a mere dot. A self-contained spaceship in which gasses and waste are recycled may also be thought of as an ecosystem.

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).

The Arctic-Alpine Life Zone in the Sierra Nevada is dominated by a plant community of boulders and low-growing perennials called the alpine fell-fields. Because there is very little soil formed in these regions (except in some alpine meadows), true tundra vegetation is poorly developed compared with the Rocky Mountains or the Arctic region. Photo was taken at the 14,500 foot summit of Mount Whitney on the eastern escarpment of the Sierra Nevada.

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.

Left: The Transition Life Zone on the western slopes of the Sierra Nevada is dominated by the yellow pine forest (Pinus ponderosa). This forest is absent from the eastern slopes, although higher slopes contain forests of the more drought-resistant jeffrey pine (P. jeffreyi). Right: Along the eastern side of the Sierra Nevada, the Upper Sonoran Life Zone of pinyon pines (P. monophylla), juniper (Juniperus osteosperma) and sagebrush (Artemisia tridentata) grades directly into the steep slopes of the Canadian and Hudsonian Life Zones. Ponderosa pine forests of the Transition Life Zone on the western side of the Sierra Nevada are absent from many areas of the eastern side.

Note: C. Hart Merriam was the founder of the United States Bureau of Biological Survey which later become the U.S. Fish and Wildlife Service. The Merriam Mountains bordering the east side of Twin Oaks Valley in San Marcos is named after his brother, Major Gustavus F. Merriam, who homesteaded in this area in 1875.

2. Food Chains & Food Webs

Food Chain: A sequence or chain of organisms existing in a natural community in which each link of the chain feeds on the one below and is eaten by the one above. There are seldom more than six links in a food chain, with plants on the bottom and the largest carnivores at the top.

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.

Decomposers Organisms of the fifth (or higher) trophic level (including fungi and bacteria) that decompose the dead members of lower trophic levels, thus returning essential elements, such as nitrogen and phosphorus, to the ecosystem. These are the primary recyclers of the ecosystem. In some food chains, the decomposers occupy the sixth trophic level and are preceeded by a fifth trophic level occupied by scavengers (such as insect larvae, vultures and hyenas).

The following table shows the general organization of a food chain:

Trophic Level
Fungi &
Larger Carnivore
Green Plant

The organization of a typical food chain.

The following illustration shows a simplified food web in a marsh ecosystem. The direction of energy flow is shown by the red arrows. Since food chains rarely follow a precise linear sequence, the food web is a better way to show energy flow between different trophic levels. The food web interconnects several different food chains within the community. [For example, the grasshopper may be eaten by the shrew; or the cricket may be eaten by the shrew or by the bullfrog.] Food webs essentially show "who eats whom" within a community or ecosystem. Some food webs depicted in biology textbooks can be extremely complex, with numerous species connected by arrows.

A simplified food web in a marsh ecosystem.

Disruption of Horned Lizard Food Chain By Argentine Ants

3. Symbiosis: Living Together

Symbiosis: Symbiosis may be defined as an intimate association between two or more organisms. There are three main types of symbiosis, including commensalism, parasitism and mutualism. In commensalism, one organism in the relationship is benefited while the other is neither benefited nor harmed. Some bird nests and trees form a commensal relationship. The birds obtain shelter and protection without harming the tree. Certain epiphytic orchids also form commensal relationships with trees. The dorsal fin of the remora is modified into a sucker which forms a temporary attachment to the shark. The shark does not seem to be inconvenienced by this and makes no attempt to remove the remora. When the shark feeds, the remora is in a good position to pick up scraps of food left by the shark. Marine mammals, including whales and manatees, often carry harmless hitchhikers called barnacles on their backs. The barnacles benefit from the ride through nutrient-rich waters. In parasitism, the parasite benefits by obtaining nutrients from the host's body, which is often harmed by the relationship. There are many examples of parasitic plants and animals, including remarkable root parasites called broomrapes. In some parasitic relationships, the host does not appear to be harmed; however, this is not commensalism, because the parasite is absorbing its nutrients directly from the host. The relationship between the jumping bean shrub and the jumping bean moth is certainly one-sided and probably slightly parasitic. The moth larva is clearly a seed predator. Although the moth doesn't appear to harm the host that much, it could decrease the percentage of viable seeds. In mutualism both members of the association (called symbionts) derive benefit from their relationship. In a sense, this mutually beneficial relationship is a type of "marriage." In lichens, the "marriage" is vital to the survival of both the algal and fungal symbionts, although some species have been grown separately in laboratories.

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.

Wayne's Word Hyperlinks About Symbiosis

4. Biological Magnification

Biological Magnification: The concentration (parts per million) of certain non-biodegradable chemical residues (such as DDT & PCBs) increases along the food chain. DDT (dichloro-diphenyl-trichloroethane), PCBs (poly-chloro-biphenyls) and PVCs (poly-vinyl-chlorides) are very toxic chlorinated hydrocarbons used in the manufacture of plastic pipe and insecticides. Dioxin or TCDD (tetra-chloro-dibenzo-dioxin) is another very toxin chlorinated hydrocarbon. It is an unintentional by-product of many industrial processes, including waste incineration, chemical and pesticide manufactoring, and pulp and paper bleaching. It is the primary toxic component of Agent Orange, the defoliant used in Viet Nam that poisoned thousands of U.S. troops and countless thousands of Vietnamise people. A normal level of dioxin is about 14 to 45 units per gram of blood fat. Almost everyone has some level of dioxin because this toxic chemical is widespread in the environment and accumulates in the food chain. In December 2004, the dioxin level in Ukrainian presidential candidate Viktor Yushchenko's blood was 6,000 time normal, indicating that he was being poisoned.

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.).

Natural Food: Cereals, fruits, vegetables and nuts without any artificial ingredients added to them. I.e. without any preservatives, flavorings or colorings. Natural foods are not necessarily organically grown. For example: Natural maple syrups vs. most commercial syrups; many popular breakfast cereals vs. natural granola-type cereals; breads containing food preservatives vs. home-made bread; artificial ice creams vs. natural (home made) ice cream. A "Twinkee" with with a shelf life of 19 years is not a "natural food."

A simplified illustration of biological magnification. The red dots represent units of DDT. Starting with a low concentration in the water, the DDT concentration (density of red dots) increases within the bodies of each successive trophic level, ultimately reaching a lethal concentration in the Grebes.

5. Biological Control

Biological Control: The elimination (control) of dangerous or destructive pest animals (such as insects or rodents) or weedy plants without the use of deadly biocides. In a strict definition, this method of control usually involves the use of beneficial predatory animals that kill off the bad infestations.

One of the best examples of biological control in California is the introduction of a minute parasitoid Australian wasp (Psyllaephagus bliteus) to attack the infestation of lerp insects in eucalyptus trees. Eucalyptus trees throughout the state, particularly the red gum (Eucalyptus camaldulensis), are under attack by an introduced aphid relative called the the red gum lerp psyllid (Glycaspis brimblecombei), an Australian insect that severely defoliates this species of eucalyptus. The wingless, yellowish immature form (nymph) secretes a waxy protective cover called a lerp, making it difficult to control by conventional insecticide sprays. Using poisonous sprays is especially hazardous in areas such as the San Diego Zoo, where the poisons could drift into animal enclosures.

Decollate snail (Rumina decollata), a snail-eating snail that is sometimes called the "killer snail." This Mediterranean species has been introduced into southern California to control populations of the common garden snail (Helix aspersa). Although the decollate snail feeds on small garden snails, it may also feed on endangered native snails, seedlings, small plants and flowers. This is especially true if the garden snails are not available.

A well-camouflaged syrphid fly larva on a rose bud. Known as the "aphid killer," this larva has a ravenous appetite for aphids. It is a very beneficial insect and a good example of biological control of harmful insects without the use of deadly deadly insecticides.

An adult syrphid fly on a tidy tip (Layia platyglossa). It is also called a "hover fly" because it can hover in midair As an adult it is a valuable pollinator.

6. Native vs. Naturalized Plants

Native: A species component of the original flora and fauna of a region. Native is synonymous with the term indigenous. The specific region may be defined as a state (such as California), or a larger geographic region, such as Old World or New World. Generally, true native species were present in a particular region long before political boundaries were established, and they were not introduced by people. In California and the offshore islands there are at least 5,000 native vascular plant species, some of which also occur in neighboring states and Baja California. Some examples of California native plants are the coast redwood (Sequoia sempervirens), giant sequoia (Sequoidendron giganteum), Torrey pine (Pinus torreyana), ponderosa pine (Pinus ponderosa), Fremont cottonwood (Populus fremontii), California sycamore (Platanus racemosa), California poppy (Eschscholzia californica), creosote bush (Larrea tridentata), black sage (Salvia mellifera), laurel sumac (Malosma laurina), and wild cucumber (Marah macrocarpus). The latter two shrubs and vine are common members of the local coastal sage scrub plant community adjacent to Palomar College.

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 rare rock lady (Maurandya petrophila) is only known from crevices in vertical limestone walls in several canyons of the Grapevine Mountains bordering Death Valley. Several obscure and inaccessible plants are shown in the canyon wall by red circles.

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 (Tribulus terrestris), an Old World annual weed that has colonized interior valleys and roadsides throughout California. Each plant forms a prostrate mat composed of trailing stems that spread in all directions. Spiny fruits develop in the leaf axils, each fruit splitting into five seed-bearing sections (burs) called carpels. Since the fruit splits into indehiscent, seed-bearing sections, it is technically referred to as a schizocarp. The spines of each section are arranged so that one is always facing upward, like the medieval weapon called a caltrop. The spiny, seed-bearing burs readily penetrate shoes, clothing and skin, where they hitchhike to new locations.

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.

A. Brazilian pepper tree (Schinus terebinthifolius), a naturalized species in southern California and a rampant weed in the Florida Everglades. B. Peruvian pepper tree (S. molle), another commonly naturalized dioecious species in southern California. Both species are members of the sumac family (Anacardiaceae), along with poison oak. The mature red berries of female trees superficially resemble the red berries of black pepper (Piper nigrum), but they are not related. Berries of S. molle are sometimes sold as "pink peppercorns." Although they are hot to the mouth, their use as a condiment is unwise because they contain volatile terpenes that can irritate mucous membranes in hypersensitive people.

Tree of heaven (Ailanthus altissima), a naturalized tree in the quassia family (Simaroubaceae). Native to China, this tree was introduced into the United States by early settlers during the 1700s and 1800s. It sends up sprouts from spreading roots, especially around settlements and water courses. It is especially abundant in the Sierra Nevada foothills where it has become an invasive weed. The above tree was photographed at the edge of a cultivated field in Twin Oaks Valley, northern San Diego County.

Roadside near Borrego Springs, California showing the Mediterranean mustard Brassica tournefortii. Open fields and slopes that once supported populations of beautiful wildflowers are now replaced by this aggressive mustard. The sand verbena (Abronia villosa var. villosa) in foreground is unable to compete with this large mustard.

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.

Introduced Caulerpa investations were first observed in the Mediterranean Sea. The initial point of introduction is thought to be near the Monaco Oceanographic Museum. This invasive alga has been traced to the Stuttgart Aquarium in Germany, where it originated as a mutant strain capable of surviving in a wider range of environmental conditions (such as temperature) compared with the native tropical strains. It became a very desirable aquarium plant, but an ecological disaster in the wild. Whenever someone discards aquarium water containing this mutant strain, it has the potential of reaching the ocean and escaping into bays and estuaries.

The marine green alga Caulerpa taxifolia showing stolon-like outgrowths and upright leaf-like thallus. The stolons anchor this fast-growing alga to the bottom of bays and coastal waters.

Problems Caused By Introduced Argentine Ants

7. Laws Of Thermodynamics

First Law of Thermodynamics: Energy cannot be created or destroyed but can only be transformed from one one form into another. Energy can occur in different forms, such as the energy of heat, electricity, light and the potential energy of chemical bonds. For example, the sun's energy came to the earth hundreds of millions of years ago. It was captured by green plants and used for photosynthesis and the formation of carbohydrate molecules. Over eons of time, the carbon atoms of ancient plant bodies were transformed into energy-rich deposits of coal. The coal is excavated and burned, giving off heat energy which drives a steam turbine to produce electricity. The electricity is used to heat the coils that toast your bread with your morning coffee.

Second Law of Thermodynamics: The second law states that whenever energy is changed from one form to another (e.g. heat into electricity), there is always a "loss" of usable energy. In other words, a substantial amount of the initial energy is dissipated. The unusable, dissipated energy is known as entropy. Depending on the type and number of energy transformations, only a small percentage of the initial energy is actually utilized to produce the final product. If coal is used as the fossil fuel source, then a small percentage of the sun's energy that came to the earth countless millions of years ago was used to heat the slice of bread in your toaster. The following table illustrates the laws of thermodynamics by comparing combustion with aerobic cellular respiration.

1st & 2nd Laws of Thermodynamics
Energy "Loss"
% Decrease
Chemical Energy Of Gasoline Is Converted Into
The Mechanical Energy Of A Motor Vehicle:

Combustion Within Internal Combustion Engine:
Hydrocarbon (C-H) + O2 = CO2 + H2O + HEAT
Chemical Energy Of Glucose Is Converted Into
The High Energy Chemical Bonds Of ATP:

Aerobic Respiration: Mostly Within Mitochondria:
Carbohydrate (C-H-O) + O2 = CO2 + H2O + 38 ATP
56% 1

Percent Decrease In Aerobic Cellular Respiration: To understand how the 56% decrease was obtained, it is helpful to compare the number of kilocalories in the initial carbohydrate molecule (glucose) and the final 38 molecules of ATP. Since it is difficult to relate to the energy contained in single molecules, the term "mole" is used. A mole can be defined as the molecular weight of a substance expressed in grams. The molecular weight is the sum of all the atomic weights in the molecule. Glucose is composed of six atoms of carbon (each with an atomic weight of 12), twelve atoms of hydrogen (each with an atomic weight of one), and six atoms of oxygen (each with an atomic weight of six). The atomic weight is the sum of the protons and neutrons in the atom of an element. [The atomic number of an element is the number of protons.] To appreciate this relationship, refer to a periodic table of the earth's elements. A link to a JavaScript periodic table is given below.

One molecule of glucose (C6H12O6) has a molecular weight of 180 (72 for six carbons + 12 for 12 hydrogens + 96 for six oxygens = 180). One mole of glucose weighs exactly 180 grams. When thoroughly incinerated, one mole of glucose releases 686 kilocalories or 686,000 calories. [A dieter's Calorie is technically a kilocalorie.] This is the amount of potential energy contained in a mole of glucose based on heat energy. 38 moles of ATP contain approximately 304 kilocalories. Since 686 kilocalories of glucose produces 304 kilocalories of ATP, the energy decrease is 686 kcal - 304 kcal = 382 kcal. The percent decrease is determined by dividing 382 kcal by the starting number of 686 kcal and multiplying this result or quotient by 100 to obtain 56 percent. [686 - 304 = 382; 382/686 X 100 = 56%.] If the percent decrease is 56 percent, then the percent efficiency is 44 percent. Remember that some biology textbooks may give different values for the kilocalories of glucose and ATP, and different percentages for the percent efficiency of aerobic cellular respiration. The values listed here are only meant to illustrate the laws of thermodynamics. They are not meant to be an authoritative reference on physiology and biochemistry.

Percent Increase & Decrease In JavaScript

8. Energy Pyramids

Pyramid of Energy: At each link in the food chain, energy that was originally stored by the autotrophic plants is dissipated along the food chain. The more links in the food chain, the more dissipated or unusable energy. There is generally a 90 percent loss at each link of the food chain, creating a pyramid-shaped diagram that is wider at the bottom and narrow at the top.

Pyramid of Mass & Numbers: The mass (weight) and numbers of organisms decreases along a food chain (e.g. grass-grasshoppers-frogs-snakes-hawk). It takes many pounds of grass (or numerous grass plants) to support one hawk at the top of a food chain.

Percent Decrease At Each Trophic Level: To determine the decrease in kilocalories for trophic level #2, subtract 1000 kcal of grasshoppers from 10,000 kcal of grass in trophic level #1 = 9,000 kcal. This decrease in kilocalories is divided by the starting number of kilocalories of grass in trophic level #1 and the result or quotient is multiplied by 100 to obtain the percent decrease. [10,000 - 1000 = 9,000; 9,000/10,000 x 100 = 90%.] Repeat these calculations to obtain percent decreases for trophic levels #3, #4 and #5. Depending on the ecosystem, the percent decrease for each trophic level is typically 80% to 90%.

An Ocean Food Pyramid: It takes about 2500 pounds (1136 kg) of phytoplankton to support 0.5 pound (0.227 kg) of tuna. This is roughly the amount of tuna packed into a single can sold at the supermarket. Note: The decrease from 2500 to 500 is 80 percent. The other trophic levels in this pyramid are decreased by 90 percent.

Food Chain Of A Baleen Whale: A baleen whale, such as the California gray whale, has a massive, fringelike sieve of whalebone (baleen) growing from its upper jaw. The baleen is used to filter out small crustaceans, such as krill, from mouthfuls of ocean water. Since the krill (zooplankton) survive on phytoplankton, this food chain contains a total of three links.

With a 90 percent decrease in energy for each link of a food chain, the efficiency of each link is approximately 10 percent. In other words, about 10 percent of the food energy available to each link is utilized and the remainder is lost "dissipated." Food chains with fewer links have more energy available to the top level consumer. Larger herbivorous land mammals (primary consumers) occupy food chains with only two trophic levels (plant--herbivore), such as elephants (5-6 tons), hippos (3 tons) and rhinos (3 tons). The largest dinosaurs also occupied the second trophic level, including apatosaurs (30 tons) and the enormous Argentinosaurus (80-100 tons). The following table compares human food chains in the U.S. and Asia. Asian food chains typically support more people because they have fewer links and less energy lost from the ecosystem:

     1000 kcal
      100 kcal      
      10 kcal      
1000 kcal
100 kcal

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