Glossary for AnalogicalPlanet.com
angiosperms Literally, "angion" is Greek for container or vessel and "sperma" means seed. Thus an angiosperm is a plant that produces seeds enclosed in a container. The container holding the seeds is known as an ovary. Compare to gymnosperms. The angiosperms are the most successful seed producing plants in terms of sheer numbers with over 250,000 species. The angiosperms first appear in the fossil record about 130 million years ago, well before the extinction of the dinosaurs. When someone speaks of "flowering plants" they generally mean angiosperms with their colorful petals. There have been changes in the classification systems for these plants in the last fifty years so you can find different names for high level taxons. For example, some authors (Hulten 1968, Zomlefer 1994) refer to angiosperms as the Class Angiospermae while others (Campbell 1999, pg 565) place all angiosperms in the Division Anthophyta (Gr. antho, "flower"). Classification schemes can get confusing but the reality is simple. All angiosperms have ovaries, gymnosperms don't.
antheridium In plants, the moist chamber where sperm develop. Specifically in bryophytes, the antheridium is a stalked sac that contains many sperm and is enclosed in a jacket consisting of a single layer of cells.
bryophyte literally "moss-like plant". Modern usage restricts this word to refer to mosses, hornworts, and liverworts only.
Carboniferous The geological period (360-290 mya) during which horsetails, club mosses, and ferns were the dominant land plant, frequently attaining the size of modern trees. These giant "tree-ferns" flourished in vast swamps which covered a large part of the continents. The remains of these swamps formed the coal beds of our times and are a type of "fossil fuel". The Carboniferous period also saw the ascendancy of amphibians, development of flying insects, and the origins of reptiles and seed plants (gymnosperms).
Devonian a geological period of the Paleozoic ("ancient life") era between the Silurian and Carboniferous periods.The Devonian period began about 409 mya (millions of years ago) and ended about 363 mya. Plants fossils showing well defined vascular (water and sap conducting) tissue appear in the Devonian period. During this period bony fishes continued to diversify and amphibians and insects first appear. The first seed plants appear near the end of the Devonian period about 360 mya. (Campbell et al. pg 549). Geological periods are blocks of time that correlate with specific types of rock strata and their characteristic fossils.The Devonian period is named for rock formations observed in Devon, England and elsewhere.As an aside, the Jurassic period of dinosaur movie fame is named for rock types found in the Jura mountains of Switzerland. The Silurian and Ordovician are named for ancient tribes of Wales, but still refer to types of rocks and their fossils (Putnam's Geology, pg 40.)
diploid possessing two sets of chromosomes. A sporophyte is composed of diploid cells because it was formed from a zygote. You have diploid cells for the same reason. Compare to haploid.
Dioscorides A Greek philosopher (circa A.D. 64) who authored a pharmacological account of plants that served along with Theophrastus's work as the basis for Pliny's book on plants, Natural History.
DNA deoxyribonucleic acid is the primary component of chromosomes. It is shaped like a ladder. The side rails are a chain of sugar and phosphate molecules and the rungs are pairs of four nitrogenous bases: guanine, adenine, thymine, and cytosine. Twist the opposite ends of the ladder so that you get a full twist every 10 rungs and you have the double helix. It's double because of the two strands of sugar phosphate. A seqeunce of "rungs" forms a functional group called a gene.
eukaryote literally a "true nucleus". A cell with a well defined nucleus surounded by a nuclear membrane and with membrane bound organelles (such as mitochondria or chloroplasts). All Fungi, plants, animals, and protists are composed of eukaryotic cells. In contrast, bacteria are called prokaryotic cells and have a nuclear area not bounded by a membrane. Prokaryotic cells are the earliest forms of cellular life and originated a few hundred million years after the earth's crust solidified (Campbell 1999, pg. 492). Prokaryotic cells first appear in the fossil record about 3.5 billion years ago. The oldest eukaryotic cell fossils are about 1.7 billion years old.
gamete The root of the word gamete is Greek gamein, to marry or join. It is found in common words like polygamy, and is very frequently used in biological terms to indicate that something is involved in reproduction. A gamete is a reproductive cell, usually a sperm or egg, that fuses with another gamete to produce a zygote. The zygote is the single cell that is the beginning of life for a sexually produced multicellular organism. We were all zygotes once--a single cell. Some people claim to remember their early childhood. Others claim to remember their past lives, but nobody claims to remember when they were a zygote. Everybody's forgotten.
gametophyte The haploid plant that produces gametes, either eggs or sperm or both. In mosses the gametophyte is easily visible as a small green plant, but in seed producing plants the gametophyte generation is reduced to microscopic proportions in the pollen grains and ovules.
glossary a listing of words used in this site and their definitions. Many of these words are biological terms and are not part of the vernacular. Learning these words is a challenge, but if you visualize the phenomena they describe, you will begin to see the phenomena of life."If you do not know the names, your knowledge of things perishes." — Linnaeus, Critica Botanica, 1737
gymnosperms Vascular plants that develop their seeds from exposed ovules hidden within cones rather than in an ovary as in angiosperms. Gymnosperms do not posses petals or ovaries, but do produce pollen and ovules. The gymnosperms first appear in the fossil record about 360 million years ago, long before the evolution of the dinosaurs. Modern gymnosperms are composed primarily of the Division Coniferophyta, the Conifers, with 550 species.The other Divisions are the Cycads with 100 species, Gnetae with 70 species, and Ginkgo with 1 species. In contrast, angiosperms, the flowering plants, comprise over 250,000 species.
habit in plants, a characteristic mode of growth. In animals a repetitive behavior usually performed unconsciously.
habitat the environment of an organism from which it draws support and to which it is related. It could be a hillside or an area of a hundered square kilometers, or a crack in a rock.
haploid refers to a single set of chromosomes in a cell, regardless of the exact number. Human gametes ( eggs and sperm) are haploid and possess 23 chromosomes. Human body cells are normally diploid i.e. they possess 46 chromosomes, one set from each parent. The same sort of thing happens in plants. The gametophyte plants are composed of haploid cells and produce the eggs and sperm. The sporophytes are diploid and produce spores. I don't know of any humans that produce spores, but there's a lot I don't know.
Hepaticae the Class of Liverworts, mainly thallose and leafy plants. Commonly referred to as "hepatics"
heterosporous The habit of producing different sized spores, usually large and small spores that develop into unisexual (single sex) gametophytes.The small microspores develop into male gametophytes which can only produce sperm, whereas the larger spores, called megaspores, develop into female gametophytes which can only produce eggs. "Heterospory appears to confer a selective advantage because it developed independently in at least four very different plant groups: ferns, lycopods, horsetails, and seed plants." (Niklas 1997, pg. 191). Compare with homosporous.
homosporous The habit of producing spores of a single size which develop into bisexual gametophytes. "Because the spores of the most ancient vascular land plants were comparatively small and because the spores found in the fossil remains of these plants tend to all look alike, these plants are generally assumed to have produced bisexual gametophytes. This assumption is somewhat problematic, however, because some modern mosses produce spores that look alike but develop into sexually dimorphic gametophytes (e.g. Macomitrium commatum)" (Niklas 1997, pg. 191).
Kingdoms The most inclusive or "highest" taxonomic category used in the classification of organisms. Many years ago there were only two kingdoms, Plants and Animals. Since 1969 a five Kingdom scheme has become popular. The additional three Kingdoms are Monera (bacteria), Protista ( mainly single-celled eukaryotes), and Fungi. More recently a three domain sytem has been used. The domains are "superkingdoms" which re-organize the Monera and Protista of the earlier system to emphasize the diversity of single-celled life (Campbell 1999, pg. 499).
lichens an organism formed by a symbiotic association of a fungus, an alga, and sometimes a cyanobacterium. Lichens are classified according to the fungal partner, the mycobiont. The algal partner is called the phycobiont ("phyco" means algae) or sometimes the photobiont and it uses photosynthesis to supply carbohydrates to the fungus. "In nature not one of the 15,000 - 20,000 fully lichenized fungi (almost a fifth of all known fungi, and 40% of all ascomycetes) is ever found without its domesticated alga, though most of the algae can lead independent existences..."( Kendrick 2000, pg.118).
liverworts officially known as the Division Hepatophyta. A primitive group of plants with no vascular system, simpler than mosses. They produce spores like mosses and live in similar habitats but have a simpler structure and probably had a common ancestor in the Ordovician period (approx 450 mya). They are cousins to the mosses and hornworts. Also see hepaticae.
logarithmic spiral has a radius which varies in length in a exponential relationship with the angle of revolution. Simple, uh? : ) Well try looking at it this way. The radius of a different kind of spiral, an Archimedian spiral, grows longer as it rotates, but the relationship is linear. If the radius of an Archimedian spiral rotates twice as much, it increases in length twice as much. The logarithmic spiral works the same way except the radius will increase by some power of the rotation not a multiple of it. This definition really needs a drawing to illustrate the point and then it would be easier to visualize.
microsporangia the specialized sporangia that only produces male spores known as microspores, contained in the anther. Microspores develop into male gametophytes. In seed producing plants the immature male gametophyte is called pollen. Female spores are called megaspores and are produced in, you guessed it, a megasporangium contained within the ovule of seed producing plants. The megaspores produce the archegonia of the female gametophyte which houses the ovum which, when fertilized by the pollen, ultimately becomes the seed produced by gymnosperms (mainly conifers) and angiosperms (flowering plants). This is a complicated description. Don't forget that all plants produce spores. For more info see heterosporous.
noosphere In his foreword to The Phenomenon of Man (Teilhard de Chardin, 1959) the noted biologist, Julian Huxley, credits Pierre Teilhard de Chardin with coining the word "noosphere" in 1925: "Thus in 1925 he coined the term noosphere to denote the sphere of mind, as opposed to, or rather superposed on, the biosphere or sphere of life, and acting as a transforming agency promoting hominisation (or as I would put it, a progressive psychosocial evolution)."
Although the definition is accurate the citation of Teilhard de Chardin as the creator of the term is questionable. Compare to a citation in Appendix 1 of a recent important English translation of The Biosphere by Vladimir I. Vernadsky first published in Russian in 1926: "1924...Many discussions with Pierre Teilhard de Chardin (1881-1955) and Edouard Le Roy (1870-1954). The trio invent the concept of 'the noosphere.' "
The connection between Vernadsky, a geologist, and Teilhard de Chardin is an important one. This English translation of Vernadsky's most important work also contains an extensive foreword by Jacques Grinevald on the unrecognized influence of Vernadsky's ideas. Teilhard de Chardin is frequently mentioned including the fact that he attended Vernadsky's lectures at the Sorbonne in 1922-1923. The similarity of the word "noosphere" to other words such as biosphere, lithosphere, atmosphere, hydrosphere and others all point to the concentric geological model of the Earth first suggested by the Viennese geologist Eduard Seuss (1831- 1914) who coined the word "biosphere" in 1875, although its current usage is that of Vernadsky. In 1944 Vernadsky published in Russian "Some words on the noosphere". Vernadsky is also the most likely source for Teilhard's use of the sphericity of the Earth as a cause of increasing psychism and social compression.
Ordovician a geological period 510 to 439 mya that saw the origin of land plants from their aquatic algae ancestors (Campbell 1999, pg 548), (Niklas 1997, pg. 176). Marine invertebrates such as gastropods, trilobites, sponges and corals were abundant and the first vertebrate fish appeared about this time. This period represents the beginning of life on land and many of the subsequent adaptations of plants, fungi and animals allowed aquatic organisms to survive and reproduce on land.
perigonium the cluster of leaves surrounding the male sex organs (antheridia) of mosses.
pinnule the smallest leaflet of a pinnate (feather-like) fern frond.
Pliny Gaius Plinius Caecilius Secundus, the Younger. Author of Natural History. A well known Roman author and natural philosopher (A.D. 61-113) who, next to Aristotle, was the most influential biologist of classical antiquity (Nordenskiold, 1935).
pollen the microscopic, immature gametophyte produced in the stamen, the male organ in seed producing plants.
pteridophyte literally a "fern-like plant". A vascular plant with well developed roots, stems, and leaves that produces and releases spores but not seeds. Applied to the horsetails, lycopods, and ferns, "pteridophyte" is a convenient descriptive word but is not often used as an exact taxonomic term. See pterophyte
pterophyte from Greek pteron, wing ; phyton, plant. A true fern. A member of the Division Pterophyta.
seed A mature plant ovule. In angiosperms it is enclosed by the thickened wall of the plant ovary. In gymnosperms (primarily conifers) the ovule is not enclosed in an ovary but is protected by the scales of the cones. The seed contains several different tissues; the embryo which develops into a new sporophyte, the endosperm for nutrition of the embryo, and the seed coat derived from the parent plant.
sporangia The spore producing structures (capsules) of a moss plant borne on the top of the sporophyte. A single sporangium in some species of Dawsonia may contain 65 million spores (Schofield 1985, page 57) while other moss sporangia may contain a few thousand spores.
spore Usually a single cell enclosed in a spore coat. Under suitable conditions a spore will germinate without fusing with another cell. Spores are produced by the sporophyte generation of plants which, by way of the spore, alternates with the gametophyte generation. A seed contains a multicellular embryo and is very different from a spore.
sporophyte The spore producing plant that alternates with the gamete producing plant in the reproductive cycle of plants. Sporophytes are diploid organisms that produce spores in sporangia. The spores then germinate and produce the gametophyte form of the species. The gametophyte then produces the eggs and sperm which unite to form a zygote. The zygote then develops into the diploid sporophyte. Then the cycle starts all over again. Whew! You would think there was an easier way, but that's the way they do it.
stamen the male organ of seed producing plants composed of the anther, which contains the microsporangia, and the filament, which is the stalk that supports the anther.
strobilus A cone-like structure produced on the fertile branches of Horsetails and some Clubmosses that houses the sporangia that produce the spores.
Theophrastus Greek philosopher and biologist ( 370-285 B.C.) Aristotle's student and successor at the Lyceum, the school founded by Aristotle. The author of 227 treatises on plants and minerals nine of which are collected in Historia Planarum , and eight of which are collected in De Causis Plantarum. Considered to be the father of Botany, "He recognized the distinctions between monocotyledons and dicotyledons, superior and inferior ovaries in flowers, the necessity for pollination and the sexuality of plants..." (Gledhill 2002). See Dioscorides.
vascular plants Generally understood to mean plants with cells specialized for the conduction of fluids such as water and sap. This includes all existing plants except for mosses and liverworts. However, some mosses such as Polytrichum have rudimentary conducting tissue.
zygote a fertilized egg. Before fertilization an egg is called an ovum. After the nucleus of the sperm fuses with the nucleus of the ovum the egg is said to be fertilized and is referred to as a zygote. The nucleus of the zygote contains chromosomes from both gametes that formed it and is thus diploid. By further cell division the zygote can grow into a multicellular organism.
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