SAGUARO CACTUS
(pronounced sah-WAH-row) The saguaro cactus (Carnegiea gigantea) is a large succulent found in the Sonoran desert of North America. This cactus has accordian-like pleats and long spines. Photosynthesis takes place on its green, chlorophyll-containing trunk. The saguaro has a life span of over 200 years and it can grow to over 50 feet tall. This cactus produces white flowers and a deep red (edible) fruit. Each fruit produces about 2,000 reddish-black seeds.

SAMARA
A samara is a one-seeded fruit, winged, indehiscent fruit, like the seed of the maple and elm (which helicopter their way down from the tree). Samara is Latin for elm seed.

SAP
Sap is a liquid that circulates within the sapwood of woody plants. Sap rises up from the roots. Sap contains water and minerals; in the spring it also contains sugars (and stimulates the growth of the tree).

SAPLING
A sapling is a small, young tree.

SAPROPHYTE
A saprophyte is a plant that obtains nutrition from dead and decaying plant or animal tissue. Most saprophytes do not produce chlorophyll, and therefore need another source of energy. Most fungi and a few flowering plants (like some orchids and Indian pipe) are saprophytic.

SAPWOOD
Sapwood is the outer layer of wood in a tree and contains living cells. Sap circulates within the sapwood of woody plants.

SAW GRASS
Saw grass, Cladium jamaicense., is a plant that thrives in wet, warm, humid areas (swamps like the Florida Everglades). A member of the sedge family, saw grass has long, tough, sharp-toothed leaves.

SCAT
Scat means animal waste or droppings.

SCALE-LIKE LEAVES
Scale-like leaves are tiny, green leaves. On junipers, scale-like leaves overlap and cover the twigs.

SCLERENCHYMA
Sclerenchyma is a supportive and protective tissue found in plants. Sclerenchyma is composed of hard, thick, dry cells.

SCLEROPHYLL FOREST
A sclerophyll forest is one in which the crowns of the trees form a continuous canopy. The word scherophyll means "hard leaf" in Greek. Sclerophyll forests are often found in Australia - Eucalyptus trees often form a sclerophyll forest. There are wet (over 30 m tall) and dry (10 - 30 tall) sclerophyll forests

SCLEROPHYLLOUS PLANTS
Sclerophyllous plants are small plants that have hard, thickened leaves and have a relatively short distance along the stem between the leaves (short internodes). Sclerophyllous plants are often from dry areas. The word scherophyll means "hard leaf" in Greek.

SCYTHIAN EPOCH
(pronounced SY-thee-en EP-ock) The Scythian epoch was the early (lower) part of the Triassic period, about 248 million to 242 million years ago, the beginning of the Mesozoic Era.

SEASONS
There are four seasons in the year: winter, spring, summer, and fall (also called autumn).

SEA WEED
Seaweed is a type of aquatic plant that obtains its energy via photosynthesis. Seaweed (like kelp) are not true plants. Seaweeds are usually green, brown, or red.

SECONDARY COMPOUND
A secondary compound is a chemical manufactured by a plant that protects it.

SECONDARY FOREST
A secondary forest (also known as a jungle) is a forest whose canopy trees have been logged (cut), causing lush growth on the forest floor.

SECONDARY GROWTH
Secondary growth is plant growth that does not occur at the tips of the stems or the tip of the roots. In seed plants, secondary growth produces bark and wood.

SEDIMENT
Sediment is any material deposited by wind or water, like rocks and sand.

SEDIMENTARY ROCK
Sedimentary rock is rock that has formed from sediment. Most fossils are found in exposed sedimentary rock.

SEED
The seed is the reproductive unit of some plants.

SEED COAT
The seed coat is the outer, protective layer covering the seed. The seed coat is formed from the two integuments in the developing seed.

SEED DISPERSAL
Seeds are dispersed (spread) by many different methods, including floating on the wind (e.g., dandelions), floating in the water (e.g., coconut, sedge), hitching a ride on an animal (e.g., cranesbill), or being eaten (and then expelled) by a seed dispersing animal (e.g., many fruits).

SEED DISPERSER
A seed disperser is an animal that eats seeds (usually contained in fruit) but does not harm the seed. The seed is excreted in the stool, and the seed is spread away from the parent plant. Some seed dispersers include the kereru (a pigeon from New Zealand) and the cassowary (from Australia and New Guinea).

SEED FERNS
Seed ferns (Pteridosperms) were primitive seed plants (not ferns at all) that lived in swampy areas from the Mississipian Epoch through the Mesozoic Era. They had woody stems studded with dried out leaf bases. The tops had fern-like fronds which bore seeds. Some seed ferns include Glossopteris (pictured above), Dicroidium, Caytonia, Denkania, and Lidgettonia.

SEED POD
A seed pod is an elongated, two-sided vessel that contain several fertilized seeds. It is a dehiscent fruit or pedicarp - the pod splits open when the seeds are mature. Beans and peas are some plants that have pods.

SEED PREDATOR
A seed predator is an animal that eats and destroy seeds instead of eating the fruit and leaving the seed or dispersing the seed in the stool. Parrots are seed predators. Seed predators limit the number of viable seeds.

SELF-POLLINATION
Self-pollination is the transfer of pollen from the anther to the stigma of the same flower or another flower on the same plant.

SENONIAN EPOCH
(pronounced cen-NOH-nee-an EP-ock) The Senonion epoch was the late (upper) part of the Cretaceous period, about 89 million to 65 million years ago, the end of the Mesozoic Era.

SEPAL
The sepals are small leaves located directly under a flower - they are the outermost part of a flower. Collectively, the sepals are called the calyx.

SERRATED
Serrated leaves have a jagged edge.

SESSILE
A leaf without a petiole (a leaf stalk) is sessile.

SEXUAL DIMORPHISM
Sexual dimorphism is characteristic of having two different forms, one for the males and another for the females of a species.

SHALE
Shale is a type of rock that is formed from clay that has been pressed into thin sheets.

SHIFTING CULTIVATION
Shifting cultivation is a type of farming in which fields are used for a few years, and are then left to grow in a wild state for many years. This allows the soil to recover and become rich and fertile again.

SHOCKED QUARTZ
Shocked quartz is quartz that has undergone deformation due to extreme pressure and heat. It has been found in the layer that marks the K-T boundary, lending credence to the Alvarez impact theory.

SHOOT
A shoot is new growth on part of a plant.

SHRUB LAYER
The shrub layer is the layer of the rainforest above the forest floor but under the canopy.

SIGNOR-LIPPS EFFECT
The Signor-Lipps Effect explains how a fossil record that appears to be a gradual extinction can actually represent a sudden extinction. If many organisms go extinct at the same time, the fossil record wouldn't necessarily represent the rarer species and the more common equally. The rarer species might disappear from the fossil record long before the time of extinction, simply due to chance.

SILT
Silt is fine dirt (soil or sand) that is carried by running water and deposited as sediment.

SILTATION
Siltation is the build-up of silt that is suspended in rivers or other bodies of water.

SILURIAN PERIOD
The Silurian Period lasted from 438 million to 408 million years ago. The first jawed fishes and uniramians (like insects, centipedes and millipedes) appeared during the Silurian (over 400 million years ago). The first vascular plants (plants with water-conducting tissue as compared with non-vascular plants like mosses) appeared on land (Cooksonia is the first known vascular plant). During this time, there were high seas worldwide until the end of the Silurian. Brachiopods, crinoids, corals, and eurypterids (sea scorpions) lived in the seas.

SIMPLE LEAF
A simple leaf is a leaf with only one lamina for each petiole (that is, each leaf blade has one stem).

SIPHONOSTELE
A siphonostele is a type of stele that consists of a cylinder of vascular tissue (xylem and phloem) that surrounds the central pith tissue.

SLASH-AND-BURN FARMING
Slash-and-burn farming is a destructive type of agriculture in which the farmer burns down a new portion of the rainforest every few years in order to cultivate a crop.

SMOOTH ENDOPLASMIC RETICULUM
Smooth ER is a vast system of interconnected, membranous, infolded and convoluted tubes that are located in the cell's cytoplasm (the ER is continuous with the outer nuclear membrane). The space within the ER is called the ER lumen. Smooth ER transport materials through the cell. It contains enzymes and produces and digests lipids (fats) and membrane proteins; smooth ER buds off from rough ER, moving the newly-made proteins and lipids to the Golgi body, lysosomes, and membranes.

SOIL
Soil is a natural, constantly-changing substance that is made up of minerals, organic materials, and living organisms. plants grow in soil.

SOLAR RADIATION
Solar radiation is the heat and light that comes from the sun.

SP.
Sp. is an abbreviation for "species." Sp. is often used when the genus is known, but the species is not.

SPECIATION
Speciation is the process in which a single species differentiates into two distinct species. One method by which this occurs is geographic isolation, in which two subpopulations of a single species are separated and no longer interbreed. Since the pressures of natural selection differ for the two groups, the two populations become more and more different from one other.

SPIKE
A spike is a flower stalk, an ear of grain (such as corn or wheat), or an inflorescence of unstalked flowers.

SPIKELET
A spikelet is a secondary spike found in grasses; it is a cluster of two or more flowers in the inflorescence.

SPINE
A spine is a sharp, modified leaf, scale, or stipule. Cacti have spines.

SPIROGYA
Spirogyra is a genus of multicellular green algae that lives in fresh water. Spirogyra cells are joined end-to-end, forming an unbranched, tube-like structure that contains one or two spirally-wound chloroplasts. Reproduction occurs asexually (as the filament breaks apart forming new strands) and sexually (two filaments meet and merge as the cell walls decay and a protoplast moves from one organism to the other, resulting in a zygote - this occurs under adverse conditions).

SPHENOPSIDS
Sphenopsids (horsetails) are primitive, spore-bearing plant with rhizomes. These fast-growing, resilient plants were common during the Mesozoic Era. The side branches are arranged in rings along the hollow stem. Horsetails date from the Devonian period 408-360 million years ago, but are still around today and are invasive weeds. Huge horsetails went extinct in the Permian mass extinction; smaller ones lived during the Mesozoic Era.

SPORE
A spore is a single-celled reproductive unit of some organisms (cryptogams like mushrooms, ferns and mosses). Functionally, a spore is similar to a seed but it does not containan embryo). Spores are usually encapsulated by a rigid wall.

SPROUT
A sprout is a very young plant (newly germinated) or the new growth on a plant (a shoot).

STAMEN
The stamen is the male reproductive parts of a flower. It consists of the filament and the anther, which produces pollen.

STELE
A stele is the central cylinder of vascular bundles in stems and roots.

STEM
A stem is the axis of a plant; it may be above or below the ground.

STIGMA
The stigma is part of the pistil, the female reproductive tissue of a flower. The stigma receives the male pollen grains during fertilization.

STIPE
A stipe is a stem-like structure in some plants, like some kelp and fungi.

STIPULE
Stipules are small, paired appendages (sometimes leaf-life) that are found at the base of the petiole of leaves of many flowering plants.

STOLON
A stolon is an above-ground stem that has buds that sprout to form new shoots, forming a new, genetically-identical plant. Strawberry plants have stolons.

STOMA
A stoma (the plural is stomata) is a pore (or opening) in a plant's leaves. Most of the stoma are on the underside of the leaf. Guard cells open and close the stoma using turgor pressure, controlling the loss of water vapor and other gases from the plant.

STRATA
The strata (singular=stratum) are the different layers of a rainforest. Different animals and plants live in different parts of the rainforest. Scientists divide the rainforest into strata (zones) based on the living environment. Starting at the top, the strata are: emergents, canopy, understory, and forest floor.

STRATIGRAPHY
Stratigraphy is a method of dating fossils by observing how deeply a fossil is buried. Sedimentary rock layers (strata) are formed episodically as earth is deposited horizontally over time. Newer layers are formed on top of older layers, pressurizing them into rocks. Paleontologists can estimate the amount of time that has passed since the stratum containing the fossil was formed. Generally, deeper rocks and fossils are older than fossils found above them.

STRATOCLADISTICS
Stratocladistics is a method of classifying organisms based upon both cladistics (considering common ancestors with shared anatomical characteristics) together with stratiography (information from the fossil record which lets you know which animals lived earlier or later than others; older fossils are deeper than more recent fossils). In stratocladistics, cladograms are generated in which ancestors preceed their descendants. (see Science, 11th June, Vol 284, 1999)

STRIATE VENATION
Striate venation is a vein pattern found in monocots leaves. A leaf with striate venation has its veins arranged almost parallel to one another.

STROMA
The stroma is part of the chloroplasts in plant cells, located within the inner membrane of chloroplasts, between the grana.

STRONG SEASONALITY
Strong seasonality is when there is a big difference in temperature between the seasons (for example, a hot summer and a cold winter). Compare to low seasonality, in which the difference in temperatures between the seasons is small (with mild winters and summers).

STYLE
The style is part of the pistil, the female reproductive tissue of a flower. The style is a long tube on top of the ovary below the stigma. After the male's pollen grains have landed on the stigma during fertilization, pollen tubes develop within the style. The pollen tubes transport the sperm from the grain to the ovum (where fertilization of the egg occurs and the seeds will develop).

SUCCESSION, PLANT
Plant succession is the natural pattern of ecosystem growth and change over time for a particular environment. Plant life follows established patterns of growth and change after major distruptions, like fires, floods, agricultural damage, logging, etc. Generally, smaller, fast-growing herbaceous species and grasses grow first in an open field, followed in a few years by softwood tree seedlings and larger herbaceous species. As a young forest develops into a mature forest (30 to 70 years), an understory of smaller hardwood trees develops. The final stage is a climax hardwood forest (100 plus years).

SUCCULENT
A succulent is a plant that has fleshy and juicy tissues, like cacti, sedums, aloes, and yuccas.

SUCKER ROOT
A sucker root is a root that emerges from the ground and sends up a shoot which supports the plant.

SUESS, EDUARD
Eduard Suess was an Austrian geologist who first realized that there had once been a land bridge between South America, Africa, India, Australia, and Antarctica. He named this large land mass Gondwanaland (named after a district in India where the fossil plant Glossopteris was found). This was the southern supercontinent formed after Pangaea broke up during the Jurassic period. He based his deductions upon the fossil fern Glossopteris, which is found throughout India, South America, southern Africa, Australia, and Antarctica.

SUSTAINABLE USE
Sustainable use is the judicious use of natural resources without destroying them.

SYMBIOSIS
Symbiosis is a situation in which two dissimilar organisms live together. There are many types of symbiosis, including mutualism (in which both organisms benefit), commensalism (in which one organism benefits and the other is not affected), or parasitism (in which one organism benefits at the other organism's expense). Symbiosis used to be defined as a situation in which two dissimilar organisms live together to the benefit of both - this is now called mutualism. The word symbiosis means "living together"" in Greek.

SYMMETRY
Symmetry across an axis (also called bilateral symmetry) 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). Radial symmetry is when a basic shape is duplicated around a central point (for example, most flowers have radial symmetry).

SYMPLESIOMORPHY
Symplesiomorphy (meaning "shared old form") is the persistence of ancestral (primitive) traits in different clades.

SYMPODIAL
Sympodial (meaning "with foot") is a type of branching growth in which the terminal bud dies or ends in an inflorescence, and growth (sympodial shoots) continues from lateral buds. What looks like the plant's main axis is actually a series of many lateral branches, each arising from the previous lateral branch. Some bamboos and orchids exhibits sympodial growth. Compare with monopodial.

SYNAPOMORPHY
Synapomorphy (meaning "shared form") is a derived (new) character shared by groups. A synapomorphy can be used to infer common ancestry.

TAP ROOT
The tap root is the main root of some plants; the tap root extends straight down under the plant.

TAXON
A taxon is category in the classification of living organisms. The taxa (the plural of taxon) in the Linnean system are kingdom, phylum, class, order, family, genus, and species.

TAXONOMY
Taxonomy is the science of classifying organisms into groups by structure, origin, common ancestor, etc.

TEETH
Teeth are the jagged edges on some leaves, like those of thistles and hawthorne.

TEMPERATE RAINFOREST
Temperate rainforests are very wet, ancient forests that rarely freeze or get very hot. Most of the world's temperate rainforests are in the Pacific Northwest of the USA.

TERMINAL BUD
The terminal bud is a bud located at the apex (tip) of the stem. This type of bud is the dominant bud, since it can cause all the lateral (side) buds below them to remain dormant at all times of the year. Terminal buds have special tissue, called apical meristem, cells that can divide indefinitely.

TERTIARY PERIOD
The Tertiary period lasted from 65 to 1.8 million years ago. It followed the Cretaceous period (the end of the Mesozoic Era) and the K-T extinction. Many mammals developed then, including primitive whales, rodents, pigs, cat, rhinos, etc.

TESTA
The testa is the seed coat. It covers the seed.

TETHYS SEA
The Tethys sea was a shallow sea that existed during the early Mesozoic Era. It was the body of water that separated the landmass of Laurasia in the north from Gondwanaland in the south.

THEORY
A theory is a proposed explanation for a phenomenon.

THIGMOTROPISM
Thigmotropism is the directional bending or turning response of a plant upon contact with a solid surface or object; it is basically a sense of touch in plants. For example, the tendrils of vines are thigmotropic.

THORN
A thorn is a sharp, modified stem. Thorns have a stem-like vascular structure. The honey locust plant has thorns.

THYLAKOID DISK
Thylakoid disks are disk-shaped membrane structures in chloroplasts that contain chlorophyll. Chloroplasts are made up of stacks of thylakoid disks; a stack of thylakoid disks is called a granum. Photosynthesis (the production of ATP molecules from sunlight) takes place on thylakoid disks. Thylakoid means 'sac-like' in Greek.

TIPITI
A tipiti is a flexible braided cylindrical basket made of jacitara palm bark that is used by the Tupis of South America. The tipiti is used to remove the poison liquid from bitter cassava root. The cassava pulp is squeezed in the tipiti until the poisonous liquid is extracted. This process makes the cassava edible.

TOMATO
The tomato is scientifically considered to be a fruit (because the seeds of the plant are contained within the tomato).

TRACE FOSSILS
Also known as ichnofossils, these are fossilized footprints, nests, dung, gastroliths, etc., but not actual body parts. They record the movement and behavior of animals.

TRACHEOPHYTE
A tracheophyte is a plant with true vascular tissue, like xylem and phloem.

TRANSGRESSION
Transgression is the flooding of a continent as the sea level increases, usually caused by melting polar ice. Another cause is sea floor spreading and underwater volcanism, in which large amounts of underwater lava cause water to be displaced onto land.

TRANSPIRATION
Transpiration is the process in which plants lose water through pores in their leaves (these openings are called stomata). As water is lost from the plant, the plant takes up more water (and minerals) through its roots. The rate of transpiration varies as the conditions of the plant change and is controlled by the opening and closing the stomata.

TREE
A tree is a plant that produces wood (made by xylem cells). These tall plants grow taller each year.

TREE FERN
Tree ferns are tall vascular plants that live in warm climates. These ferns have a clump of fronds on top of a fibrous trunk.

TREE RINGS
By counting the number of tree rings in a tree's trunk, you can tell how old the tree was.

TRIASSIC PERIOD
(pronounced tri-ASS-ik PEER-ee-ud) Dinosaurs and mammals evolved during the Triassic period, 248 - 208 million years ago.

TROPHIC LEVEL
A trophic level is a level of the grazing food chain. For example, plant-eaters are primary consumers; they occupy the second trophic level in the grazing food chain.

TROPICAL RAINFOREST
Tropical rainforests are warm, very wet forests that do not freeze (the temperature remains over 75°F=24°C) and do not get extremely hot. Tropical rainforests cover about 7% of the Earth's surface, in a band around the equator. They are also called equatorial rainforests.

TROPICS
The tropics are a 3,000 mile (4800 km) wide band around the equator, between the Tropic of Cancer (23.5° N latitude) and the Tropic of Capricorn (23.5° S latitude).

TRUNK
The trunk of a tree is the stem that supports the crown.

TSUNAMI
(pronounced sue-NAHM-ee) A tsunami is a huge wave, caused by undersea earthquakes, volcanic eruptions, or, more rarely, by asteroid or meteoroid impact (as in the case of the K-T extinction).

TUBER
A tuber is a modified root that stores nutrients. Potatoes are tubers.

TUMBLEWEEDS
Tumbleweeds are annual plants that have a rounded shape; they dry our in the fall, and the stem beaks off near the ground. The ball-shaped, withered plant tumbles around in the wind (hence the name), scattering their seeds. There are many different types of tumbleweed - they live in the prairie and plains of the United States. One common type of tumbleweed is Russian thistle (Salsola kali).

TURGOR PRESSURE
Turgor pressure is the force that is exerted on a plant's cell wall by the water (in the cytoplasm) within the cell. The water presses against the cell wall from within, giving the plant cell rigidity, helping it keep its shape. Turgor pressure is the mechanism that changes the shape of the guard cells that open a plant's stomata, pores located on the underside of leaves.

TUSSOCK GRASS
Tussock grass (Deschampsia cespitosa or Aira cespitosa) is a tall variety of grass (20 to 36 inches tall) that is used as an ornamental grass. Tussock grass grows in clumps and has fine hair-like leaves. In summer it produces fine green to yellow inflourences.

TYPE SPECIES
A type species is the species of an organism from which a new genus is named. For example, Tyrannosaurus rex is the type species for the genus Tyrannosaurus.

TYPE SPECIMEN
A type specimen is the set of fossil remains of an organism from which a new species is named.

UNDERSTORY
The understory of a rainforest is a dark, cool environment under the leaves in the trees (the canopy) of a forest, but over the ground.

UNICELLULAR
Unicellular organisms consist of a single cells. (Compare with multicellular.)

URANIUM 235
Uranium 235 is a radioactive element; over time, it gradually changes into the element lead. It can be used to date very old rock layers