DATING FOSSILS
Dating a fossil is determining when that organism was alive. Paleontologists use many ways of dating individual fossils in geologic time, including stratigraphy, observations of the fluctuations of the Earth's magnetic field, radioisotope-dating, and looking at nearby index fossils.

DECIDUOUS
Deciduous plants lose their leaves seasonally, usually for the dry season. Some deciduous plants include ash, beech, hickory, maple, and oak.

DECOMPOSER
Decomposers are organisms like fungi and some bacteria that break down and digest the remains of organisms.

DECOMPOSITION
Decomposition is the decay or breakdown of things into more basic elements. For example, after a plant dies, it decomposes into organic nutrients.

DEFORESTATION
Deforestation is the loss of forest. Deforestation has many causes, including man's cutting down trees, forest fires, severe drought, changes in sea level, disease, etc.

DEHISCENT
A dehiscent is a structure on some plants that opens to release seeds or pollen grains.

DEHISCENT FRUIT
A dehiscent fruit splits open when it is maturite, causing the dispersal of its seeds. Some dehiscent fruits include cotton, poppy, peanuts, milkweed, magnolia, and all beans.

DEHYDRATE
To dehydrate is to lose a lot of water. Plants can become dehydrated in dry, hot weather.

DENDROCHRONOLOGY
Dendrochronology is the science in which tree rings are studied to determine conditions in the past.

DENDROCLIMATOLOGY
Dendroclimatology is the science in which tree rings are studied to determine climate changes in the past.

DESERT
A desert is a very dry area that receives less than 10 inches (25 cm) of rainfall each year. Desert organisms have adapted to life with little water.

DETRIVORE
A detrivore (or detritus feeder) is an organism that eats the dead remains of other organisms (detritus). Examples of detrivores include some bacteria and fungi.

DIASPORE
A diaspore (also called a disseminule) is a part of a plant that is separated from the plant and dispersed (sent or taken away from the plant) for reproduction. Diaspora include seeds, fruits, and spores.

DICHOTOMOUS KEY
A dichotomous key is a method for determining the identity of sometihing (like a butterfly, a plant, or a rock) by going through a series of choices that lead the user to the correct name of the item. At each step of the process, the user is given two choices; each alternative leads to another questions until the identification is completed. For example, a question in a dichotomous key for trees might be something like, "Does it have flat or needle-like leaves?" Dichotomous means "divided in two parts".

DICHOTOMOUS VENATION
Dichotomous venation is a pattern of leaf veins in which the veins branch in two over and over again. Ferns are dichotomousy veined. A few angiosperms and gymnosperms (like gingkos) have dichotomous venation.

DICOT
A dicot (Class Magnoliopsida) is a type of flowering plant (an angiosperm) whose seed has two embryonic leaves (cotyledons). The leaf veins are usually net-like (and not parallel). Taproots are often present. Beans and peas are examples of dicots.

DICTYOSTELE
A dictyostele is a siphonostele (a cylinder of vascular tissue) that has two or more overlapping leaf gaps (as in ferns). It is a divided stele located in the outer cortex (instead of in the center of the stem). Dictyosteles are composed of individual vascular bundles.

DIMORPHISM
Dimorphism means having two forms. It usually means that an organism has two different types, for example, males and females of some species look different, and are said to be sexually dimorphic.

DIOECIOUS
A dioecious plant has the male and female flowers on different plants. For example, date trees are dioecious. (Compare with monoecious.)

DIPLOID
A diploid cell has the same number of chromosomes that most other cells of that organism have (except the gametes, like the sperm and the egg, which are haploid).

DIRT
Dirt is another name for soil. Soil is a natural, constantly-changing substance that is made up of minerals, organic materials, and living organisms. Plants grow in soil.

DISPERSAL
Dispersal is the process in which an organism spreads out geographically. Seeds are dispersed by the winds and by animals.

DISPERSERS
Dispersers are animals that spread plant seeds. Some dispersers include birds, insects, bats, and furry animals like monkeys.

DISSEMINULE
A disseminule (also called a diaspore) is a part of a plant that is separated from the plant and dispersed (sent or taken away from the plant) for reproduction. Dissemules include seeds, fruits, and spores.

DNA
DNA (short for deoxyribonucleic acid) is a complex organic molecule that carries the genetic information of an organism. DNA is the primary constituent of chromosomes. DNA is made up of two strands of amino acid bases (adenosine, cytosine, guanine, and thymine) arranged in a double helix. DNA's chemical instructions are carried to throughout the cell by another nucleotide, RNA.

DOGGER EPOCH
The Dogger epoch was the middle part of the Jurassic period, about 180 to 159 million years ago.

DOMINANT
The dominant plant is the most adundant species in an area, for example, pine trees are dominant in a pine forest.

DORMANCY
Dormancy is a period in which a plant has no active growth in response to harsh environmental conditions (like droughts or cold seasons).

DOUBLE COMPOUND LEAF
A double compound leaf is a leaf in which each leaflet of a compound leaf is made up of secondary leaflets.

DRIP TIP
The drip tip is the long, sharply-pointed tip on some rainforest plant leaves that allows water to flow quickly off the leaf surface. In the rainforest, many leaves have a drip tip. Without it, water would build up on the leaf

The Earth is the third planet from the Sun.

ECOSYSTEM
An ecosystem is the interrelationships between all of the living things in an area.

EDICARA FAUNA
Ediacara fauna is the animal life that lived during the Vendian or Ediacaran period (roughly 650 to 544 million years ago). The Vendian is when the earliest-known animals evolved. Vendian biota (Ediacara fauna), included soft-bodied multi-cellular animals, like sponges, cnidarians, worms, and soft-bodied relatives of the arthropods. The Ediacara was named for the Ediacara Hills in Australia, north of Adelaide, where these early animal fossils were first found (in 1946, by the Australian mining geologist Reginald C. Sprigg). Other Vendian Period fossils have been found in Mistaken Point, Newfoundland and the White Sea off the northern coast of Russia.

EMBRYO
An embryo is a developing plant still inside the seed. The embryo has cotyledons (embryonic leaves), a root cap, a food source and a plumule (shoot), all located inside the protective seed coat.

EMERGENTS
Emergents are giant trees in a rainforest that are much higher (up to 270 feet or 81 m) than the average canopy height. The emergents house many birds and insects in a very dry environment.

ENDANGERED SPECIES
An endangered species is a group of organisms that is dwindling in numbers and may go extinct soon. Many species of plants are endangered.

ENDEMIC
Endemic plants are native to an area and are only found in that area.

ENDOPLASMIC RETICULUM
The endoplasmic reticulum (ER) is a network of membranes in plant cells (and all eukaryotic cells) that control protein synthesis and cellular organization.

EON
Two or more geological Eras form an Eon, which is the largest division of geological time, lasting hundreds of millions of years.

EPHEMERALS
Ephemerals are plants that have an accelerated life cycle. These hardy plants grow and reproduce quickly - they are often dormant during extreme weather (droughts, heat spells, cold spells, etc.). Their seeds are drought resistant. These plants often live in areas with harsh climates, like deserts and very cold areas. Some ephemerals include: Desert Paintbrush, Desert Sand Verbena, Dutchman's Breeches, Mojave Aster, and Yellow Trout Lily.

EPICORMIC SHOOT
An epicormic shoot (also called a coppice 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).

EPICOTYL
The epicotyl is the part of the stem that is above the first leaves.

EPIDERMIS
The epidermis is the outer protective layer of a plant. This tissue helps prevent injury and minimizes water loss by evaporation.

EPIGYNOUS OVARY
An epigynous ovary (also called an inferior ovary) is an ovary located below the flower parts (the calyx, corolla, and androecium). The flower parts are attached to the top of the ovary.

EPIPHYTE
Epiphytes are plants that live attached to a plant (or other structure like a rock, 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 their host).

EPOCH
An epoch is a division of a geologic period; it is the smallest division of geologic time, lasting several million years.

EQUATORIAL 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 tropical rainforests.

EQUISETUM
Equisetum (a modern genus of horsetail) is a primitive, spore-bearing plant (a sphenopsid) with rhizomes. Itsside branches are arranged in rings along the hollow stem. Other genera of horsetail were common during the Mesozoic Era, like Neocalamites, Calamites etc. Horsetails date from the Devonian period 408-360 million years ago, but are still around today and are invasive weeds.

ER
ER stands for endoplasmic reticulum. The ER is a network of membranes in plant  (and all eukaryotic cells) that control protein synthesis and cellular organization.

ERA
Two or more geological periods comprise an Era, which is hundreds of millions of years in duration.

ETHNOBOTANY
Ethnobotany is the science which studies how plants are used in various cultures.

EUKARYOTE
A eukaryote (which means "true nucleus") is an organism whose cells have internal membranes (which divide the cell into regions that have different functions) and a structurally-discrete nucleus. They also have a cytoskeleton which controls their shape. Eukaryotes include plants, animals, fungi, and protists (they do not include blue-green algae, bacteria, viruses, and other primitive microorganisms).

EURASIA
Eurasia is the combined, joined land masses of Europe and Asia.

EUTROPHICATION
Eutrophication is when the concentration of nutrients in a waterway increases; this occurs when sewage, fertilizers, or sediments enter the water. This increase in the concentration of nitrogen and/or phosphorous may result in an algal bloom (an overabundance of blue-green algae that depletes the water of oxygen, killing other organisms).

EVAPORATION
Evaporation is the process in which a liquid is transferred into gaseous form.

EVAPOTRANSPIRATION
Evapotranspiration is the process in which rain water evaporates from trees and returns to the atmosphere.

EVERGLADES
The Everglades is a swamp located in southwestern Florida. It contains over 2,000 different types of plants, including saw grass (Cladium jamaicense), mangroves (including the red, black and white mangroves), alligator flag (Thalia geniculata), strangler fig (Ficus aurea), gumbo-limbo (Bursera simaruba), mahogany (Swietenia mahagoni), saw palmetto, pond cypress (Taxodium ascendens), bald cypress (Taxodium distichum), moonvine (a morning glory), coontie, and various willows, slash pine (Pinus elliottii densa) and other pines, and oaks with Spanish moss hanging form the limbs. Many epiphytes (air plants) like the night-blooming epidendrum (Epidendrum nocturnum) also live in trees.

EVERGREEN
Evergreen plants do not lose their leaves seasonally. Pines and firs are examples of evergreens. (Compare with deciduous plants.)

EVOLUTION
Evolution is a process in which the gene pool of a population gradually (over millions of years) changes in response to environmental pressures, natural selection, and genetic mutations. All forms of life came into being by this process.

EVOLVE
To evolve is to develop by the process of evolution, changing in some way as an adaptation to the environment.

EXTINCT
An animal species that is extinct has died out. Most animal species that ever existed have gone extinct, including all the dinosaurs.

EXTINCTION
Extinction is the process in which groups of organisms (species) die out.

EXTINCTION-LEVEL EVENT
An Extinction-Level Event is a catastrophic event (such as a large asteroid or comet hitting the Earth, a large change in the Earth's temperature/sea level, tremendously increased volcanism, etc.) that is capable of causing a mass extinction. This event would greatly damage the ecosphere of Earth, causing many groups of organisms to die.

EXTRACTIVE RESERVE
An extractive reserve is an area in a rain forest in which people are allowed to harvest crops, such as rubber or Brazil nuts.

EYE
An eye is an axillary bud on an underground plant part such as a tuber (e.g., potato) or in the area where the stem joins the tuberous root (e.g., dahlia).

FAMILY
In classification, a family is a group of related or similar organisms. A family contains one or more genera (plural of genus). A group of similar families forms an order.

FAST PLANTS
Fast Plants are fast-growing plant varieties that were developed at the University of Wisconsin, Madison, Wisconsin, USA. Fast Plants complete their life cycles about 45 days after planting. Fast plants are used in classrooms and laboratories around the world for teaching and research. The first plants in space were Fast Plants.

FEN
A fen is a wet area rich in peat and other organic matter.

FERN
Ferns are non-flowering vascular plants that were plentiful during the Mesozoic Era and usually live in warm, moist areas. Ferns have fronds divided into leaflets. Classification: Plyla: Lycophyta (lower ferns like clubmosses), Pterophyta (ferns), Psilophyta (whisk ferns) (true ferns belong to the Class Filices).

FERTILIZER
Fertilizer is material that is added to soil to increase is fertility and output. Fertilizers include manure, compost, and chemical mixtures.

FILAMENT
The filament is the part of the flower that holds the anther.

FLAGELLUM
A flagellum is a long, thin, whip-like structure that is found on some organisms, including some unicellular algae. Flagella help propel the organism through water.

FLAX
Flax (family Linaceae, genus Linum) is a flowering plant from cool, temperate areas. It has narrow, lance-shaped leaves and blue flowers - the plant grow to be up to about 1.5 to 2 feet tall. Flax is grown for its seeds (which yield oil) and linen fiber (a strong vegetable fiber that is made from the woody stalk of the flax plant).

FLORA
The flora is all the plants that live in an area.

FLOWER
The flower is the reproductive unit of angiosperms. Flowers usually have carpels, petals, sepals, and stamens. Some flowers (called perfect flowers) have both male and female reproductive organs; some flowers (called imperfect flowers) have only male reproductive organs (stamens) or only female reproductive organs (ovary, style, and stigma). Some plants have both male and female flowers, while other have males on one plant and females on another. Complete flowers have a stamen, a pistil, petals, and sepals. Incomplete flowers lack one of these parts.

FLOWERING PLANTS
Flowering plants are Angiosperms (meaning "covered seed"). They produce seeds enclosed in fruit (an ovary). They are the dominant type of plant today; there are over 250,000 species, including grasses, peas, etc. Their flowers are used in reproduction. Angiosperms evolved about 140 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).

FOLIAGE
Foliage is the leaves of plants.

FOLIVORE
A folivore is animal that eats foliage (leaves). For example, the green iguana is a folivore.

FOOD WEB
The food web (or food chain) is all of the interactions between predators and prey in which plants and animals obtain nutrition. The web starts with plants or other autotrophs (organisms that make their own food from light and/or chemical energy) that are eaten by herbivores (plant-eaters). The herbivores are eaten by carnivores (meat-eaters). These are eaten by other carnivores. When any organism dies, it is eaten by tiny microbes (detrivores) and the exchange of energy continues.

FORB
A forb is a small, herbaceous (non-woody), broad-leaved vascular plant (excluding grasses, rushes, sedges, etc.). For example, wild flowers are a type of forb.

FOREST
A forest is an area in which trees are the dominant plant.

FOREST FLOOR
The forest floor is the lowest layer of a rainforest, extending from the ground to about 3 feet (1 m) high. This layer is teeming with animal life, especially insects. The largest animals in the rainforest generally live here.

FOREST SUCCESSION
FOrest or 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).

FOSSIL
Fossils are mineralized impressions or casts of ancient animals and plants. Fossils have been found on every continent on Earth.

FOSSIL FUEL
A fossil fuel is a naturally-ocurring, energy-rich organic (carbon-based) substance (like shale, petroleum (oil), coal, or natural gas) in the Earth's crust that was formed from ancient organic material (mostly plants).

FROND
A frond is the fern-like (or feathery) foliage of a plant that has many divisions. Ferns and palms have fronds. Frond is also used to refer to the main part of a kelp plant (excluding the holdfast).

FRUIT
A fruit is the part of a flowering plant that contains the seeds. Some fruits include apples, oranges, berries, maple pods, and acorns. Some fruit are fleshy and some are dry, like cotton (a dehiscent fruit) and sunflower (an indehiscent fruit). Not all fruit are edible. True (simple) fruits (like the tomato, coconut, watermelon, olive, lemon, and banana) develop from the wall of a single ovary. False (compound) fruits (like the strawberry, rosehip, and pineapple) develop from more than one pistil.

FUNGUS
Fungus (plural fungi) are organisms that obtain energy by breaking down dead organic material and that produce spores. Some fungi include mushrooms, toadstools, slime molds, yeast, penicillin, mold, and mildew. Classification: kingdom Fungus.