The cell theory states that: 1) Cells are the basic unit of STRUCTURE2) Cells are the basic unit of FUNCTION 3) Cells arise from PREEXISTING cells Not all cells have a distinct nucleus. Red blood cells, for example, lose theirnucleus as they mature. In any event, this has nothing whatever to do with thecell theory. Many anaerobic organisms (some bacteria for example) do not need oxygen. Many organisms do quite well without any nervous system or a very simple one at best. Plants do not get their food from the environment. They make it via photo- synthesis. What is true of all living things is that they arise from other living organisms. The term cell was first used in the bio-logical sense by Robert Hooke who used it to describe the spaces or holes he saw as he examined a piece of cork undermagnification. In fact, what he saw was not cells but still he is given credit for the first use of the term. Rudolf Virchow is generally given creditfor a major contribution to the cell theory. It was Virchow who first pro- posed that all cells must come from other, preexisting cells. In other wordslife comes from life. The kingdom Protista includes all one- celled organisms (except prokaryotes such as bacteria) and simple multicell- ular organisms. These include true algaeand protozoa. The spine of an animal is composed of numerous bones called vertibrae. Thus the spine is often called the vertibral column and, any creature with a backboneis placed in the sub-phylum Vertibrata. Such animals are vertibrates. A pine tree (a gymnosperm) has true leaves, a stem, true roots and conduct- ing tissue (xylem and phloem). A fern does not have true leaves nor true rootsbut it does have vascular (conducting) tissue. Bluegreen algae have none of these things but they are not classifiedas plants. Rather they are in the king- dom Monera. Among plants, only the mosses (phylum Bryophyta) lack true roots, leaves, stems and have no con- ducting tissues. When Latin names are used for an organ- ism, only the genus and species are given. The genus, the larger group, always comes first. Thus the dog and the coyote are in the same genus (canis)but are different species within that genus. In order to be classified as a chordate an organism must meet two criteria. First it must have, at some time during its life-cycle, a notochord. This is a cartilage-like rod located where the spine would normally be expected. Second, it must have a dorsal nerve cord. You are a chordate since you had a notochord briefly during fetal devel- opment and since you now have a dorsal nerve cord located inside your vertibralcolumn. The system of classification in use to- day is (from largest to smallest group):Kingdom - Phylum - Class - Order - Family - Genus - Species. Subgroups arepossible within each classification. An individual organism must take in nourishment, produce ATP by respiration and carry on life processes by the synthesis of new materials. These func- tions are essential for life. What is not necessary for the survival of the individual, however, is reproduction. A single organism can live out a full life span regardless of whether it has ever reproduced. Inorganic compounds are those which are not produced by biological processes andwhich do not contain carbon. All of the choices listed qualify as inorganic sub-stances but of them, water is by far themost abundant. All cells are either prokaryotic or eukaryotic. The eukaryotic cell is largeand contains numerous organelles includ-ing a membrane bounded nucleus. The pro-karyotic cell is much smaller. It has almost no organelles and lacks a true nucleus. The only such cells are the bacteria and the bluegreen algae and they are classified in their own kingdomcalled Monera. A genus is not a very large grouping andso most of the organisms located in the same genus are likely to have very sim- ilar characteristics. Of the choices, the lion and the tiger are most closely related. So close, in fact that they have been known to interbreed in captiv-ity and produce young. Both the lion and the tiger are in the genus felis. Also in the genus is the house cat, felis domestica. The word `arthropod' means jointed app- endage. Insects, spiders and crabs, all members of the phylum arthropoda have jointed legs. They also have a hard outer coating called an exoskeleton and their bodies are typically segmented into two, three or more sections. These are the most basic characteristics of all arthropods. Earthworms, hydras, grasshoppers and humans make up a very diverse group of organisms. It is not likely that they would all be found in just one of the smaller classifications such as genus orspecies. It seems likely that organisms that are so very different might be found together only in the largest grouping. In fact, all these creatures are animals and are all, therefore in the kingdom animalia. The smaller the category, the less the amount of variation between its members.The smallest group is a species and there is little variation among members of a species as compared to members of different species. The question asks for the proper order but does not indicate whether from largest to smallest or from smallest to largest. Regardless, the proper order iskingdom-phylum-class-order-family-genus-species. Of the choices, only kingdom - phylum-genus-species is in agreement with the sequence above. The system of classification of plants and animals is based on similarities in structure and biochemistry between organisms. Fungi and slime molds are not plants. They are very different and are found ina separate kingdom, fungi. Algae, while photosynthetic, are placed in the king- dom protista and are not true plants at all. A lichen is a symbiotic combination of a fungus and an algae, neither one ofwhich is a plant. Ferns and maple trees,while in different phyla, are both true plants and are therefore in the kingdom plantae. The magnification that can be obtained by a light microscope can be easily calculated by multiplying the power of the eyepiece lens times the power of theobjective lens. In this case, the micro-scope has two objective lenses and thus two possible magnifications: 10X times 10X = 100X total and 10X times 40X = 400X total. A millimeter is a thousandth of a meter.A micrometer is a millionth of a meter. Thus, a millimeter is one thousand timesbigger than a micrometer. A tenth of a millimeter would only be 100 times bigger than a micrometer. 0 0.1 millimeter = 100 micrometers A millimeter equals 1000 micrometers. Therefore 0.5 millimeters equals 500 micrometers. The total magnifying power of a micro- scope is obtained by multiplying the power of the eyepiece lens times the power of the objective lens: Eyepiece X Objective = Total Power. By rearranging the formula the power of the objective can be calculated: Total Power Objective Power = ------------- Eyepiece Power 400/20 = 20 power. It is generally agreed that today, new cells can arise only from preexisting cells because the conditions that orig- inally gave rise to life no linger exist. Groups of cells do work together.Such cell groups are called tissues. Of course some organisms, such as the para-mecium and the ameba are only a single cell. It is not true that the simplest organisms have no cells as long as the viruses are not considered to be living organisms in the true sense of the term. There are usually two lenses on a micro-scope; the eyepiece lens (through which the observer looks) and the objective lens which is closest to the specimen. Stains are used in microscopy because most cells lack color and are very difficult to observe under normal illum-ination. Just as light passes through unstained specimens, so do electrons. Thus virtually all specimens prepared for electron microscopy are stained. Unstained specimens can be observed using the phase contrast microscope which takes advantage of interference patterns created by the specimen. Everything is constantly changing. The external environment is in a constant state of flux and the internal environ- ment must be constantly REGULATED in order to maintain all conditions within a normal range. The levels of glucose would be expected to rise significantly after a heavy mealand to fall drastically after a long time without eating. This, however is not the case and it is true that glucoselevels are maintained within a narrow range by a delicate interplay of hor- hormones. The maintenance of "normal" conditions within the organism is calledHOMEOSTASIS. Taxonomy is the science of classifica- tion. Animals and plants are placed in categories ranging from the most simple to the most complex. This arrangement, however is no coincidence nor is it merely a result of the whims of the tax- onomists. The classification system in use today is a reflection of evolution which began with simple organisms and built on each theme creating organisms of greater and greater complexity. Monerans are bacteria and blue-green algae. They are all monocellular organ- isms. All monerans, fungi and plants produce cells which are surrounded by a cell wall (although the composition of this structure varies widely). Animals uare organisms whose cells lack a cell wall. Unlike plants, which make their own food, animals are heterotrophs and must ingest food from the environment. Mitochondria are organelles. That means that they are only parts of cells and must therefore be smaller than a whole cell. In order to collect them, cells must be lysed (broken open) and then placed in an ultracentrifuge. They are spun until the mitochondria are concen- trated into a narrow region of the cen- trifuge tube. They can then be removed and prepared for examination by the transmission electron microscope which has the power to see minute details. ÍEveryone who has taken high school biology has participated in the dissec- tion of a frog or perhaps an earthworm. These are macrodissections or dissec- tions of large organisms. Microdissec- tion is concerned with the very small. Using microdissection techniques, sci- entists have been able to transplant thenucleus from one cell into another. Enzymes, ribosomes and DNA base pairs are far too small to be manipulated evenwith microdissection instruments. A concentration gradient occurs when there is a high concentration of a sub- stance on one side of a membrane and a low concentration on the other. Normallythat substance will try to move across the membrane from the highly concentrat- ed area to the region of lower concen- tration; from HIGH to LOW. To move the other way (uphill), from low to high, requires energy. The cell must ACTIVELY TRANSPORT the substance across the mem- brane. The modern system of classification begins by classifying all living (and extinct) organisms into five kingdoms. These are: MONERA PROTISTA FUNGI PLANTAE ANIMALIA Each kingdom is subdivided into phyla and each phylum is further subdivided to the smallest group, the species.