ABAXIAL
Abaxial means being located on the side away from the axis. The abaxial surface of a leaf is its underside.

ABSCISIC ACID
Abscisic acid is a plant hormone that inhibits growth, causes the abscission of leaves, induces dormancy, closes stomata, and triggers other phenomena in response to adverse conditions.

ABSCISSION
Abscission is the normal separation of a leaf, fruit, or flower from a plant. Abscisic acid is the plant hormone involved in abscission.

ABSCISSION ZONE
The abscission zone is the area at the base of leaf's petiole, a fruit stalk, or a branch in which the separation (abscission) layer develops. The disintegration of this layer causes a leaf, fruit, or flower to fall from a plant. Abscisic acid is the plant hormone involved in this process.

ACICULAR
Acicular means needle-like (for example, pine needles are acicular).

ACID RAIN
Acid rain is polluted and harmful to the environment. Acid rain has a low pH. Acid rain may have been a component of the K-T extinction.

ACHENE
An achene is a dry, indehiscent one-seeded fruit with a leathery pericarp that is easily separated from the seed coat (for example, sunflower).

ADAPTIVE RADIATION
Adaptive radiation is the diversification of a species as it adapts to different ecological niches. If successful, the species becomes specialized for the new environments (the mechanism being natural selection), and they eventually evolve into different species.

ADAXIAL
Adaxial means being located on the side towards the axis. The adaxial surface of a leaf is the upper side.

ADENOSINE TRIPHOSPHATE
ATP (short for adenosine triphosphate) is a nucleotide that has a ribose sugar and three phosphate groups. ATP is a high-energy molecule used for energy storage by organisms. In plant cells, ATP is produced in the cristae of mitochondria and chloroplasts.

ADVENTITIOUS
Adventitious organs are those organs that grow from an unusual part of the plant. For example, fibrous adventitious roots grow from the trunk above the ground instead of starting underground.

AERIAL ROOT
An aerial root is a plant's root that is produced above the ground.

AGE
An age is a unit of geological time which is distinguished by some feature (like an Ice Age). An age is shorter than epoch, usually lasting from a few millions of years to about a hundred million years.

AGRICULTURE
Agriculture is the science of farming, including growing plants and raising animals.

AGROFORESTRY
Agroforestry is a land use system in which woody perennials are grown with agricultural crops (together with other land uses, like animal production).

AGROLOGY
Agrology is a branch of soil science that studies the soil used in producing crops.

AGROSTOLOGY
Agrostology is a branch of botany that studies grasses.

AIR PLANT
Air plants (also called epiphytes) are plants that live attached to a plant (or other structure like a telephone pole or a building) and not in the ground). Epiphytes include many orchids and bromeliads. Epiphytes are not parasites; they get water and nutrients from the air (and not from their host).

ALGAE
Algae are simple photosynthetic organisms that belong to the kingdom Protista. Most algae are aquatic; seaweeds are algae. Some algae are unicellular while others are multicellular.

ALIEN
An alien is a plant that is not native to a place; it came from another place.

ALOE
Aloes are succulent, clumping plants with fleshy, toothed (non-fibrous) leaves. THere are about 300 species of aloe; they live in warm, dry habitats and most originated in northern Africa. Aloe vera is a popular plant whose gel-like sap is used as a medicinal salve; it is originally from northern Africa, the Cape Verde Islands, and the Canary Islands. Aloe vera has gray-green leaves and tubular yellow flowers that grow on a stalk that is up to 3 feet tall. Classification: Family Liliceae (lilies). Genua Aloe, Species - about 300 including A. vera, A. ferox, etc.

ALTERNATE
An alternate pattern of leaves or buds is a pattern in which there is one leaf (or bud) per node, and on the opposite side of the stem (not in pairs).

ALVAREZ THEORY OF EXTINCTION
This theory is that a large asteroid, meteor, or comet hit the Earth 65 million years ago, causing huge atmospheric and geologic disruptions, leading to a mass extinction which killed the dinosaurs and many other plant and animal species.

AMBER
Amber is a yellowish, fossilized tree resin (from conifers) that sometimes contains bits of trapped matter.

AMYLOPLAST
A organelle (with double membranes) in some plant cells that stores starch. Amyloplasts are found in starchy plants like tubers and fruitsr.

ANGIOSPERM
(pronounced AN-jee-oh-sperm) Angiosperms (meaning "covered seed") are flowering plants. They produce seeds enclosed in fruit (an ovary). They are the dominant type of plant today; there are over 250,000 species. Their flowers are used in reproduction. Angiosperms evolved about 145 million years ago, during the late Jurassic period, and were eaten by dinosaurs. They became the dominant land plants about 100 million years ago (edging out conifers, a type of gymnosperm). Angiosperms are divided into the monocots (like corn) and dicots (like beans).

ANNUAL
An annual is a plant that goes through its entire life cycle within a year. It grows from a seed, matures, produces seed, and dies within a year.

ANNUAL RING
Annual rings are concentric circles that appear on tree trunk cross-sections that mark the end of a growing season. These rings show whether the tree grew a lot or a little that year.

ANTHER
The anther is the tip of a flower's stamen. The anther contains the pollen.

ANTHOPHYTA
Anthophyta are flowering plants, the largest group of plants (which includes the grasses). The flowers are used in reproduction. They evolved during the Cretaceous period.

APICAL DOMINANCE
Apical dominance is the phenomenon in which a terminal (end) bud inhibits the development of lateral (side) buds.

APICAL MERISTEM
The apical meristem consists of meristematic cells located at the tip (apex) of a root or shoot.

APOGEOTROPIC ROOTS
Apogeotropic roots are roots that grow upwards to the soil surface (other roots grow downwards), emerging from the soil and growing upwards. The sego palm has apogeotropic roots, as do cycads.

APOMIXIS
Apomixis is a type of reproduction in which a plant produces seeds without fertilization.

APOMORPHY
An apomorphy is a new genetic characteristic common to a clade. Feathers are an apomorphy for birds.

APPLESEED, JOHNNY
Johnny Appleseed was a legendary man who spread apple trees through the USA. His real name was John Chapman, but he was called Johnny Appleseed because of his love for growing apple trees

AQUATIC
Aquatic organisms are those found in water. Many plants are aquatic, including seaweeds.

ARABLE
Arable land is suitable for growing crop plants.

ARBOREAL
Arboreal means living in trees. Many animals are arboreal, including the sugar glider.

ARBORETUM
An arboretum is a park or garden where trees and shrubs are grown for educational and/or scientific uses.

ARCUATE
Leaves with arcuate venation have veins that are curve towards the apex (tip).

AREOLE
Areoles are circular clusters of spines on a cactus. Flowers bud at an areole and new stems branch from an areole.

ARID
An arid area is dry and hot, with little rainfall and few plants.

ASTEROID
An asteroid is a large rock or small planet orbiting the Sun. Most asteroids lie in a belt between Mars and Jupiter. An asteroid impact with the Earth may have caused the K-T mass extinction.

ATMOSPHERE
The atmosphere is the mixture of gases that surrounds the Earth. The Earth's atmosphere is mostly nitrogen.

ATOM
Everything is made up of tiny atoms. An atom is the smallest part of an element that has the properties of that element.

ATP
ATP is short for adenosine triphosphate; it is a nucleotide that has a ribose sugar and three phosphate groups. ATP is a high-energy molecule used for energy storage by organisms. In plant cells, ATP is produced in the cristae of mitochondria and chloroplasts.

AUTOTROPH
(pronounced AW-toh-trofe) An autotroph (or producer) is an organism that makes its own food from light energy or chemical energy without eating. Most green plants, many protists (one-celled organisms like slime molds) and most bacteria are autotrophs. Autotrophs are the base of the food chain.

AUXIN
Auxins are growth hormones found in plants. Auxins induce phototropism, apical dominance, cell elongation and many other reactions.

AWN
The awn is a bristle-like extension of a plant near its tip.

AXIL
The axil of a plant is the angle between the upper side of the stem and a leaf, branch, or petiole. In flowering plants, the bud develop in the axil of a leaf.

AXILLARY BUD
The axillary bud is a bud that develops in the axil (the angle between the stem and the leaf) of a plant.

AXIS
The axis of a plant runs through the middle of it, e.g., the stem of a plant or the rachis of a compound leaf.

BACKGROUND EXTINCTIONS
Background extinctions are those extinctions that occur continually throughout time. These extinctions are caused by small changes in climate or habitat, depleted resources, competition, and other changes that require adaptation and flexibility. Most extinctions (perhaps up to 95 per cent of all extinctions) occur as background extinctions.

BADLANDS
Badlands are barren, severely eroded places on Earth where the soft rock layers are sculpted into beautiful forms. These exposed rock layers are often wonderful places in which to find fossils. They're called badlands because the land is useless for farming and many other human purposes.

BAMBOO
Bamboo is a fast-growing monocot grass.

BANANA
The banana tree is an herbaceous plant (because there is no woody tissue in the stem), it is also considered a fruit (because the seeds of the plant are contained within the banana).

BARK
The bark is the outer covering of the trunk, branches, and roots of trees.

BARLEY
Barley is a cereal grain related to wheat, oats, and rice. Barley seeds (the part of the plant that is highest in nutrition) grow in spikes at the tips of the stems - it resembles wheat. This important crop is grown in temperate areas and is used as animal feed, for malt (used in making beer, malted milk, and food flavoring), and for human consumption (used as a flour, a thickener, a cereal, in soups, etc.). Barley was cultivated thousands of years ago; it was grown by the Egyptians from 5,000 to 7,000 years ago. The countries that produce the most barley are Russia, Canada, and Germany. Classification: family Poaceae (Gramineae) (grasses), genus Hordeum, species H. vulgare.

BENNETTITALEANS
Bennettitaleans, also called cycadeoids, are primitive plants (gymnosperms) that resemble cycads (but they are not cycads), but have different methods of reproduction. Bennettitaleans lived throughout the Mesozoic Era. Examples of bennettitaleans include Williamsonia (Jurassic through end Cretaceous), Williamsoniella (Jurassic through end Cretaceous), and Zamites (Triassic).

BERRY
A berry is a small, juicy, fleshy, stoneless fruit that contains one or many seeds. This simple fruit has a pulpy pericarp surrounding the seed. Some berries include the gooseberry, raspberry, tomato, currant, and grape.

BIENNIAL
Biennial (menaing "two years") means that it takes two years to complete the full life cycle.

BILATERAL
Bilateral means two sides.

SYMMETRY
Bilateral symmetry (also called symmetry across an axis) is when one side of an object is the mirror image of its other half - i.e., one half has the same shape and size as the other half (for example, most leaves are bilaterally symmetrical).

1,000,000,000

BILLION
A billion is a thousand million. Multicellular life evolved on Earth about a billion years ago.

BINOMIAL NOMENCLATURE
Binomial nomenclature is a system developed by Linnaeus for giving organisms scientific names in which each organism has a genus name (always capitalized) and a species name (not capitalized). For example, the Venus flytrap is Dionaea muscipula, and people are Homo sapiens.

BIODIVERSITY
Biodiversity is the abundance of different plant and animal species found in an environment.

BIOLOGICAL MAGNIFICATION
Biological magnification is the phenomenon in which toxins (poisons) are more and more concentrated in living organisms that are higher up in trophic levels of the food web. For example, if a small amount of toxins is in plants, the animal that eat those plants have a higher concentration of the toxins, and the meat-eaters that eat those plant-eaters have even higher levels of the toxin. The toxins are from pesticides (bug killing chemicals), herbicides (weed-killing chemicals) and waste materials.

BIOMASS
A biomass is the total amount of living material in an area. It is calculated by adding up the weights of all of the organisms.

BIRCH
Birch (genus Betula, many species) are broad-leafed, deciduous trees and shrubs with paper-like bark.

BLADDER
A bladder is a small, air filled sac. Some plants, like bladderwort (a seaweed), have air bladders.

BLADE
A blade is a narrow, flat leaf.

BLUE-GREEN ALGAE
Blue-green algae (also called cyanobacteria) are simple, (usually) one-celled photosynthetic organisms that lack a membrane-bound nucleus (they are prokaryotic). They have a primitive, bacteria-like cell structure (lacking a nucleus and other organelles); although they ahve photosynthetic pigments, they lack chloroplasts (the specialized photosynthetic organelles seen in higher plants). Blue-green algae belong to the kingdom Monera.

BOLIDE
A bolide is a meteor, asteroid, or comet that hits the Earth and explodes.

BOTANIST
A botanist is a scientist who studies plants.

BOTANY
Botany is the scientific study of plants.

BRACT
A bract is a reduced, leaf-like structure that is associated with a flower or a cone.

BRANCH
A branch is a part of a tree or shrub that grows from the trunk or stem.

BROMELIAD
Bromeliads are a group of plants that have stiff, waxy leaves that form a cup-shaped body. This "cup" catches and retains water during wet weather, and the plant uses this water to live through dry spells. Most bromeliads are xerophytes (able to tolerate a dry environment) and epiphytes (living attached to another plant and not rooted in the ground). Classification: Division Magnoliophyta (Angioperms), Class Liliopsida (monocots), Subclass Zingiberidae, Order Bromeliales, Family Bromeliaceae (Bromeliads). Bromeliads were named for the Swedish botanist Olaus Bromelius (1639-1705).

BROWSER
A browser is an animal that eats tall foliage (leaves). Many sauropod dinosaurs, like Brachiosaurus and Ultrasauros, were browsers.

BRYOPHYTES
Bryophytes (Phylum Bryophta) include the hornworts (Class Anthocerotae), liverworts (Class Hepaticae), and mosses (Class Musci). These low-growing plants do not have true roots, leaves, or stems - they also lack a vascular system (the internal tubes that transport food and water in more advanced plants). Bryophytes probably evolved from green algae; fossils of bryophytes are rare.

BUD
A bud is a small, developing part of a plant that will grow into a flower, a new leaf or a stem.

BUD SCALE
A bud scale is a modified leaf (or similar structure) that covers and protects the bud.

BULB
A bulb is an underground stem, usually globular, that has fleshy leaves emerging from the top and roots emerging from the bottom. The fleshy leaves store food. Examples include the tulip, narcissus, and onion.

BULBEL
A bulbel (also called a bulbet) is a small bulb that grows from another bulb. This is an example of vegetative proagation.

BULBLET
A bulbet (also called a bulbel) is a small bulb that grows from another bulb. This is an example of vegetative proagation.

BURBANK, LUTHER
Luther Burbank (1849-1926) was an American plant breeder who developed over 800 new strains of plants, including many popular varieties of potato, plums, prunes, berries, trees, and flowers. One of his greatest inventions was the Russet Burbank potato (also called the Idaho potato), which he developed in 1871. This blight-resistant potato helped Ireland recover from its devastating potato famine of 1840-60. Burbank also developed the Flaming Gold nectarine, the Santa Rosa plum, and the Shasta daisy. Burbank was raised on a farm and only went to elementary school; he was self-educated. Burbank applied the works of Charles Darwin to plants. Of Darwin's The Variation of Animals and Plants under Domestication, Burbank said, "It opened up a new world to me."

BURGESS SHALE
The Burgess shale is an incredibly fossil-rich area in the Canadian Rocky Mountains (in British Columbia). This Lagerstatten (a geological fossil deposit rich with varied, well-preserved fossils) is replete with fossils from the Cambrian Period, roughly 500 million years old. The Burgess shale was discovered in 1909 by Charles Doolittle Wolcott, who was the Secretary of the Smithsonian Institution in Washington, D.C. at the time. Fossils from this area include early representatives of most modern groups, including plants, worms, sponges, shrimp-like crustaceans, and jellyfish.

BUTTRESSES
Buttresses are tree trunk supports that help hold up tall trees in rainforests. They are needed to stabilize the tree because the soil is shallow (only a few inches deep) and the tree roots do not penetrate very deeply into the earth.

1,000,000,000


BYA
"bya" is an abbreviation for billions of years ago.

C3 PLANT
A C3 plant is one that produces phosphoglyceric acid, (a molecule that has three carbon atoms) as a stable intermediary in the first step in photosynthesis (the Calvin Cycle). Most plants on Earth (over 95 percent) are C3 plants.

C4 PLANT
A C4 plant is one that produces oxaloacetic acid (a molecule that has four carbon atoms) as a stable intermediary in the first step in photosynthesis. Very few plants on Earth (less than 1 percent) are C4 plants (including corn and sugarcane). Photorespiration in C4 plants is more efficient in strong light. The processes in C4 biochemistry were studied by M. D. Hatch and C. R. Slack.

CACAO
The cacao plant (Theobroma cacao) is a evergreen flowering tree native to wet, warm forests of South and Central America. This tree grows to 40 feet (12 m) tall. After flowering, 10 to 14-inch long red fruit pods develop. In each pod are almond-shaped cacao beans and pulp. Chocolate is made from the beans in the pods of the cacao plant.

CACTUS
A cactus (the plural is cacti) is a succulent plant that can live in dry areas. It has a structure that minimizes water loss. The stems are photosynthetic, green, and fleshy. The leaves are reduced to spines or are absent. Classification: Division Magnoliophyta (angioperms), Class Magnoliopsida (dicots), Subclass Caryophyllidae, Order Caryophyllales, Family Cactaceae (Cactus).

CALIFORNIA POPPY
A golden poppy (Eschscholzia californica) from western North America. It has finely-divided foliage and cup-shaped flowers.

CALVIN CYCLE
The second stage in the process of phtosynthesis is called the Calvin Cycle (it is also called the Calvin-Benson Cycle or the Carbon Fixation Cycle. In the Calvin Cycle, carbon molecules from carbon dioxide, CO₂, are fixed into the sugar glucose, (C₆H₁₂O₂) (in six repeats of the cycle). The Calvin Cycle takes place in the stroma of eucaryotic chloroplasts. The major enzyme that mediates the Calvin Cycle is Rubisco (ribulose-1-5-biphosphate carboxylase). The Calvin Cycle was first investigated in the late 1940s and early 1950s by the Nobel Prize winning chemist Melvin Calvin (1911-1997).

CALYX
The calyx is the sepals of a flower.

CAMBIUM
Cambium is a layer of dividing cells found in the cambium forms the specialized xylem and phloem cells and causes the stem to increase in thickness.

CANOPY
The canopy consists of the upper parts of the trees of a rainforest (about 65 to 130 feet or 20 to 40 m above the ground). The canopy is the part of a forest in which the branches of the trees spread out and block sunlight from reaching the forest floor. This leafy environment is full of life in a tropical rainforest and includes insects, birds, reptiles, mammals, and more.

CAPILLARY ACTION
Capillary action is the movement of water as it is pulled upwards through tubes (xylem) within a plant's roots, stems, and leaves. The water (containing minerals and dissolved nutrients) is driven against gravity by adhesion of the water molecules (they stick to the sides of the tubes), cohesion of those molecules (the water molecules sticking together), and surface tension (the forces of the molecules on surface of the upward-moving water).

CAPSULE
A capsule is a seed pod that opens when it is dry and the seeds are mature.

CARBON DIOXIDE
Carbon dioxide, CO₂, is a molecule that has one carbon atom and two oxygen atoms; it is a gas at standard temperature and pressure. Plants use carbon dioxide gas in the photosynthetic process.

CARNIVORE
Carnivores are animals that eat meat. They usually have sharp teeth and powerful jaws.

CARPEL
The carpel is the female reproductive organ of a flower - it makes the seeds. It consists of the stigma, style and ovary. There may be more than one carpel in a flower.

CASPARIAN STRIP
The Casparian strip is waxy layer (a band of suberin, a waterproofing material) that is located in the walls of plant root cells. This barrier strip stops the transport of water and minerals into the main vascular system of the root.

CAUDEX
The caudex is an enlarged, woody base of the stem or trunk (located just below the gound) on some plants - it is used for water storage. Many desert plants have a caudex, an adaptation to dry conditions. Some palms, cycads, and succulents have a caudex.

CAUDICIFORM
Caudiciform means having a caudex.

CEDAR
Cedar trees (genus Cedrus) are large evergreen coniferous trees (up to about 80 feet tall) that have dense clusters of needles held in wide, woody peg-like structures. The barrel-shaped cones are held upright above a branch. Some cedars include: Cedar of Lebanon (Cedrus libani); Atlas cedar (Cedrus atlantica) - with blue-green foliage; Deodar cedar (Cedrus deodara) - with drooping branches.

CELL
The cell is the basic structural unit of all organisms. Plant cells have a tough outer cell wall, a cell membrane, genetic material (DNA), cytoplasm, and many organelles.

CELL MEMBRANE
A cell membrane (also called the plasma membrane or plasmalemma) surrounds each plant cell (it is located within the cell wall).

CELL WALL
Plant cells have a thick, rigid cell wall located outside the cell membrane. The cell wall is made of cellulose (a polysaccharide carbohydrate), proteins, and sometimes lignin. The cell wall gives the cell most of its support and structure. The cell wall also bonds with other cell walls to form the structure of the plant.

CELLULAR RESPIRATION
Cellular respiration is a process in which energy is produced from various molecules (like glucose), producing ATP (adenosine triphosphate). During cellular respiration, oxygen is used and carbon dioxide is produced Cellular respiration occurs in the mitochondria of eukaryotes, and in the cytoplasm of prokaryotes.

CELLULOSE
Cellulose is a carbohydrate that comprises much of a plant's cell, especially the cell wall.

CENOZOIC ERA
The "Age of Mammals" (65 million years ago to today), saw the emergence of familiar life forms, humans, the modern look of the continents, and a cooling climate. The Cenozoic (meaning "recent life") followed the Mesozoic Era.

CENTROSOME
A centrosome (also called the "microtubule organizing center") is a small body located near the nucleus - it has a dense center and radiating tubules. The centrosome is where microtubules are made. During cell division (mitosis), the centrosome divides and the two parts move to opposite sides of the dividing cell.

CEREAL
A cereal is a grain that is used for human food. Some cereals include rice, oats, wheat, and barley.

CERRADO
The cerrado is a grassy, treeless plain that surrounds the Brazilian rainforest.

cf.
Cf. is an abbreviation for "compare" or "compare with."

CHALK
Chalk is a soft, white type of limestone (a sedimentary rock). It consists mostly of calcium carbonate (CaCO₃) from ancient, microscopic, single-celled marine invertebrate shells. This type of rock is very porous, soft (a hardness of 3 on the Mohs scale), and crumbly. The chalk used to draw with is actually gypsum (calcium sulfate, CaSO₄-2H₂O)

CHARACTER
A character is a inherited trait of an organism. Characters are usually described in terms of a state, for example: "blue eyes" vs. "brown eyes," where "eyes" is the character, and "blue" and "brown" are its states.

CHICXULUB CRATER
The Chicxulub crater at the tip of the Yucatán Peninsula is an impact crater that dates from 65 million years ago. It is 120 miles wide and 1 mile deep. It is probably the site of the K-T meteorite impact that caused the extinction of the dinosaurs and many other groups of organisms.

CHLOROPHYLL
Chlorophyll is a molecule that can use light energy from sunlight to turn water and carbon dioxide gas into sugar and oxygen (this process is called photosynthesis). Chlorophyll is copper-based and is usually green.

CHLOROPLAST
Chloroplasts are small green structures in plants that contain chlorophyll. Leaves have many chloroplasts.

CHONDRITIC METEOR
Chondritic meteors are stony meteors with chondrules, tiny glass spheres. These meteors are unchanged since their formation, shortly after the formation of the sun. These meteors consist of elements also common in the Earth's core.

CHROMOSOME
Chromosomes are microscopic, self-replicating structures found in the nucleus of cells. Chromosomes contain genetic material (coiled stands of DNA that contain many genes). The genome of an organism is made up of the set of chromosomes that contain all of its genes. Chromosomes were discovered by Walther Fleming in 1879; the term chromosome was proposed by Waldeyer in 1888.

CINCHONA TREE
The cinchona tree is a tropical tree that is the primary source of the anit-malarial drug quinine. Quinine is found in the bark of the cinchona tree. Quinine is a chemical that cures malaria, a deadly tropical disease carried by mosquitoes. There are many species of cinchona; they range from about 15 to 20 meters tall. The cinchona tree is native to rainforests of the eastern slope of the Amazonian Andes of South America, where it is called the "fever tree." Classification: Family Rubiaceae, Genus Cinchona, Species C. officinalis, C. ledgeriana, C. uccirubra, C. calisaya, and others.

CLADODE
A cladode is a stem that looks like a leaf.

CLADE
A clade is a group of all the organisms that share a particular common ancestor (and therefore have similar features). The members of a clade are related to each other. A clade is monophyletic.

CLADISTICS
Cladistics is a method of classifying organisms based on common ancestry and the branching of the evolutionary family tree. Organisms that share common ancestors (and therefore have similar features) are grouped into taxonomic groups called clades. Cladistics can also be used to predict properties of yet-to-be discovered organisms.

CLADOGRAM
Cladograms are branching diagrams that depict species divergence from common ancestors. They show the distribution and origins of shared characteristics. Cladograms are testable hypotheses of phylogenetic relationships.

CLASS
In classification (taxonomy), a class is a group of related or similar organisms. A class contains one or more orders. A group of similar classes forms a phylum.

CLASSIFICATION
The classification of organisms helps in their study. Cladistics is a method based on common ancestry; the Linnean system is based on a simple hierarchical structure.

CLOUD FOREST
A cloud forest is a rainforest that is on a mountainside. It is usually misty and cloudy.

CLIMAX VEGETATION
Climax vegetation is the final stage in the development of an area.

CLUB MOSSES
Club mosses (Lycopsids) are primitive, vascular plants (pteridophytes) that evolved over 375 million years ago (during the Devonian). Huge club mosses went extinct during the Permian mass extinction; smaller ones lived during the time of the dinosaurs. These plants live near moisture (in order for their spores to germinate). These fast-growing, resilient plants propagate with rhizomes (underground stems). Classification: Division Lycopodiophyta, Class Lycopodiopsida, Order Lycopodiales, Family Lycopodiaceae (Club-mosses).

COAL
Coal is a combustible mineral formed from organic matter (mostly plant material) that lived about 300 million years ago (during the Pennsylvanian Period ). During the Pennsylvanian Period, the earth was covered with huge swampy forests of giant ferns, horsetails, and club mosses. As layer upon layer of these plants died, they were compressed and covered with soil, stopping the decomposition process, forming peat. Heat and pressure chemically forced out oxygen and hydrogen, leaving carbon-rich deposits, called coal. A 20-foot-thick layer of plant material produces a one-foot-thick layer (seam) of coal.

COLEOPTILE
A coleoptile is a protective sheath that surrounds the shoot tip and the embryonic leaves of the young shoot of grasses.

COMET
A comet is a celestial body that orbits around the sun. Its tail of gas and dust always points away from the sun.

COMMENSALISM
Commensalism is a situation in which two organisms are associated in a relationship in which one benefits from the relationship and the other is not affected much. The two animals are called commensals. An example pf commensalism is vermiliads (plants living on trees in rainforests) and frogs; the frogs get shelter and water from the vermiliad but the vermiliad is unaffected. Commensalism is a type of symbiosis.

COMPANION CELL
A companion cell is a type of cell that pumps nutrients (sugars) into phloem cells.

COMPLETE FLOWER
A complete flower has a stamen, a pistil, petals, and sepals.

COMPOSITE FLOWER
A composite flower (like the sunflower) has a many individual flowers (called florets) on a wide, flat receptacle, that look like a single flower. The flowers in the central disk are called disk flowers; the flowers on the periphery are called ray flowers. This group is called Asteraceae (Compositae).

COMPOUND LEAF
A compound leaf is a leaf that is divided into many separate parts (leaflets) along a midrib (the rachis). All the leaflets of a compound leaf are oriented in the same plane. When a compound leaf falls from the tree, it falls as a unit. A double compound leaf is one in which each leaflet of a compound leaf is also made up of secondary leaflets.

CONE
A cone (strobilus) is the reproductive fruiting structure of many tracheophytes. It is a group of scales that are joined to a central stalk; the seeds are borne on the surface of the cone scales. A cone scale contains either ovules or spores (depending on whether it is female or male).

CONIFER
Most conifers are evergreen trees and shrubs that bear naked seeds in cones (a woody strobilus). Examples of modern-day conifers include pine, fir, larch, and spruce trees. Mesozoic Era conifers included redwoods, yews, pines, the monkey puzzle tree (Araucaria), cypress, and Pseudofrenelopsis (a Cheirolepidiacean). Towards the end of the Mesozoic, flowering plants flourished and began to overtake conifers as the dominant flora.

CONSERVATION
Conservation is the wise use of natural resources (plants, animals, minerals, water, etc.) so that they are not damaged and will be in good condition in the future.

CONSUMER
A consumer is a living thing that eats other living things to survive. It cannot make its own food (unlike most plants, which are producers). Primary consumers eat producers, secondary consumers eat primary consumers, and so on. There are always many more primary consumers than secondary consumers, etc.

CONTINENTAL DRIFT
Continental drift is the movement of the Earth's continents. The land masses are hunks of Earth's crust that float on the molten core. The ideas of continental drift and the supercontinent of Pangaea were presented by A. Wegener in 1915.

CONTRACTILE ROOT
A contractile root is a root that contracts (gets smaller) and pulls down the crown of the plant below the surface of the soil.

CONVERGENT EVOLUTION
Convergent evolution (convergence) is when a trait develops independently in two or more groups of organisms. An example of convergence is the wings of Pterodactyls and bats.

COOKSONIA
Cooksonia is the oldest-known land plant. This primitive plant dates from Silurian period, about 428 million years ago Cooksonia was an erect plant with dichotomous branches and terminal sporangia (sacs that produce reproductive spores). Cooksonia fosils have been found in the USA, Canada, and Czechoslovakia.

COPPICE SHOOT
A coppice shoot (also called a epicormic shoot, sap shoot, water shoot, or water sprout) is a shoot (new growth) that arises from an adventitious or dormant bud on a branch or a stem of a plant (usually near the base of the plant). This fast-growing shoot often starts to grow when part of a forest canopy is removed or thinned (allowing light in).

COPPICE STAND
A coppice stand is an area of coppice shoots.

CORPSE FLOWER
The "corpse flower" is the world's largest flower. This giant bloom is found in rainforests of Indonesia. It's scientific name is Rafflesia arnoldi. Rafflesia gives off a putrid smell that reminds people of rotting meat (this odor attracts its pollenators, beetles and flies), hence its nickname. Rafflesia's enormous flower is about 3 feet (1 m) across and weighs about 20 pounds (9 kilograms). The flower takes about a year to develop, then it blooms for about a week before dying. The flower has five wide orange petals (with pale dots) surrounding a spiked cup. Rafflesia has no stem, no roots, and no leaves. The flower is supported by fungus-like tissue that lives in another plant - the Tetrastigma vine.

COQUINA
Coquina is a type of limestone (a kind of sedimentary rock) that is mostly made of shells and shell fragments.

CORDATE LEAF
A cordate leaf has a heart shape, with the wide part towards the petiole.

CORK
Cork (also called periderm) is the soft, light-weight bark of the cork oak tree. This low-density material floats in water. Cork cells are made by cork cambium cells. Cork contains suberin, a waxy, water-proof material. Cork protects the tree from water loss and from insects and infections.

CORM
A corm is a fleshy underground stem of some plants. It looks like a bulb, but is solid (it is not formed in layers).

CORN
Corn (Zea mays), also called maize, is a type of cereal grass; it is an edible grain. This tall, annual plant has long, alternately-spaced blade-like leaves, and a strong, solid stem. A flowering plant, staminate (male) flowers grow on the tassels at the end of the main axis of the stem. The pistillate (female) inflorescence grows into the ear of corn, and is a spike having a thick axis paired spikelets in rows (each row of paired spikelets produces two rows of grain). The ear is covered by modified leaves, called husks or shucks. Corn evolved in the Americas, but has been brought all around the world by people; it is the second-largest food crop (behind wheat). Classification: Division Magnoliophyta (angioperms), Class Magnoliopsida (dicots), Class Liliopsida (monocots), Subclass Commelinidae (grasses, sedges and rushes), Order Cyperales, Family Poaceae (Gramineae) (grasses).

COROLLA
The corolla consists of the petals of a flower.

COTYLEDON
The cotyledon is the embryonic leaf within a seed. When a seed germinates, the cotyledon is the first leaf to grow. Monocots have one cotyledon; dicots have two cotyledons.

CRENOLATE
A crenolate leaf margin has edges that are shallow-toothed.

CRISTAE
(singular crista) The multiply-folded inner membrane of a cell's mitochondrion that are finger-like projections. The walls of the cristae are the site of the cell's energy production (it is where ATP is generated).

CROSS-POLLINATION
Cross-pollination is the transfer of pollen from the anther to the stigma of a flower on a different plant.

CYTOPLASM
Cytoplasm is the jelly-like material outside the cell nucleus in which the organelles are located (the entire contents of the cell located inside the plasma membrane, but excluding the nucleus).

CYTOSOL
Cytoplasm is the jelly-like material in cells, excluding the cell nucleus and all organelles (the entire contents of the cell located inside the plasma membrane, but excluding the nucleus and other organelles).

CRETACEOUS PERIOD
Dinosaurs were at their height during the Cretaceous period, 146-65 million years ago, and flowering plants spread and flourished. There was a mass extinction (the K-T mass extinction) at the end of the Cretaceous, marking the end of the dinosaurs and many other species of animals and plants.

CRISPED
Crisped leaves have a tighly curled margin. Parsley and kale leaves are crisped.

CROZIER
The crozier is the spirally coiled "fiddlehead" of a young fern leaf.

CROWN
The crown of a plant is the area from which new shoots arise or the point at which the roots meet the stem. Also, the upper area of the tree that has a lot of branching and leaves.

CRYPTOGAM
Cryptogams are plants and plant-like organisms that do not reproduce with seeds and do not produce flowers. Many cryptogams reproduce using spores. Ferns, mosses, fungi, and algae are cryptogams.

CRYSTALS
Crystals are solids whose atoms form a very regular pattern.

CULM
A culm is the elongated straw or hollow stem of grasses. The culm usually supportes the inflorescence.

CUNEATE
Cuneate means wedge-shaped.

CULTIVAR
A cultivar is a plant that is a cultivated (bred) variety.

CUTICLE
The cuticle is the fatty or waxy outer layer of epidermal cells that are above ground.

CYANOBACTERIA
Cyanobacteria Blue-green algae (also called blue-green algae) are simple, (usually) one-celled photosynthetic organisms that lack a membrane-bound nucleus (they are prokaryotic). They belong to the kingdom Monera.

CYCAD
Cycads (Cycadophyta) are primitive seed plants that dominated the Jurassic period (cycads comprised 20% of the world flora). Cycads are palm-like trees that live in warm climates. Separate male and female plants exist (they are dioecious). These gymnosperms have long, divided leaves and produce large cones. Cycads evolved during the Pennsylvanian, had their heyday during the Mesozoic, and only about 185 species (in 11 genera) still exist today. Leptocycas (shown above) and Ptilophyllum were Mesozoic Era cycads. Later cycads had a more rounded, barrel-like base. Classifcation: Division Pinophyta (Gymnosperms), Subdivision Cycadicae, Class Cycadopsida, Order Cycadales, Family Cycadaceae (Cycads)

CYCADEOID
Cycadeoids (Bennettitales) were plants with woody stems (some erect, some spherical) and very tough leaves. Cycadeoids do not always have separate male and female plants. Cycadeoids are now extinct. Some Mesozoic Cycadeoids included: Cycadeoidea, Vardekloeftia, Williamsonia (shown above), Williamsoniella, Westersheimia, and Leguminanthus.

CYCADOPHYTES
Cycadophytes included the Cycads and Cycadeoids (Bennettitales), plants with woody stems (some erect, some spherical) and very tough leaves. These two groups differ mainly in the way they reproduce: Cycads have separate male and female plants; Cycadeoids do not always. Cycadeoids are now extinct but there are still a few cycads. Some Mesozoic Era Cycads included: Leptocycas, Cycas, Zamia, Dioon, Bowenia, Stangeria, and Microcyas. Some Mesozoic Cycadeoids included: Cycadeoidea, Vardekloeftia, Williamsonia, Williamsoniella, Westersheimia, and Leguminanthus.