Exam 3 Biology

Lignin

A strong polymer embedded in the cellulose matrix of the secondary cell walls of vascular plants that provides structural support in terrestrial species .

Gametangium

Multicellular plant structure in which gametes are formed. Female gametangia are called archegonia, and male gametangia are called antheridia

Seta

The elongated stalk of a bryophyte sporophyte

Seed

An adaptation of some terrestrial plants consisting of an embryo packaged along with a store of food within a protective coat

Tracheid

A long, tapered waterconducting cell found in the xylem of nearly all vascular plants. Functioning tracheids are no longer living .

Sporophyll

A modified leaf that bears sporangia and hence is specialized for reproduction .

Heterosporous

Referring to a plant species that has two kinds of spores; microspores, which develop into male gametophytes, and megaspores, which develop into female gametophytes

Bryophyte

An informal name for a moss, liverwort, or hornwort; a nonvascular plant that lives on land but lacks some of the terrestrial adaptations of vascular plants .

Phloem

Vascular plant tissue consisting of living cells arranged into elongated tubes that transport sugar and other organic nutrients throughout the plant

Archegonium

In plants, the female gametangium, a moist chamber in which gametes develop .

Rhizoid

A long, tubular single cell or filament of cells that anchors bryophytes to the ground. Unlike roots, rhizoids are not composed of tissues, lack specialized conducting cells, and do not play a primary role in water and mineral absorption

Apical meristem

A localized region at a growing tip of a plant body where one or more cells divide repeatedly. The dividing cells of an apical meristem enable the plant to grow in length .

Sporopollen

A durable polymer that covers exposed zygotes of charophyte algae and forms the walls of plant spores, preventing them from drying out .

Microphyll

A small, usually spineshaped leaf supported by a single strand of vascular tissue, found only in lycophytes

Alternation of generations

A life cycle in which there is both a multicellular diploid form, the sporophyte, and a multicellular haploid form, the gametophyte; characteristic of plants and some algae .

vascular tissue

Plant tissue consisting of cells joined into tubes that transport water and nutrients throughout the plant body

Cuticle

A waxy covering on the surface of stems and leaves that prevents desiccation in terrestrial plants; or a tough coat that covers the body of a nematode .

Megaphyll

A leaf with a highly branched vascular system, found in almost all vascular plants other than lycophytes. See also microphyll

Peat

Extensive deposits of partially decayed organic material often formed primarily from the wetland moss Sphagnum .

Vascular Plant

A plant with vascular tissue . Vascular plants include all living plant species except liverworts, mosses, and hornworts .

sporangium

A multicellular organ in fungi and plants in which meiosis occurs and haploid cells develop

homosporous

Referring to a plant species that has a single kind of spore, which typically develops into a bisexual gametophyte

hornwort

A small, herbaceous, nonvascular plant that is a member of the phylum Anthocerophyta

monilophyte

An informal name for a member of the phylum Monilophyta, which includes ferns, horsetails, and whisk ferns and their relatives

lycophyte

An informal name for a member of the phylum Lycophyta, which includes club mosses, spike mosses, and quillworts .

peristome

A ring of interlocking, tooth-like structures on the upper part of a moss capsule (sporangium), often specialized for gradual spore discharge .

strobilus

The technical term for a cluster of sporophylls known commonly as a cone, found in most

sorus

A cluster of sporangia on a fern sporophyll. Sori may be arranged in various patterns, such as parallel lines or dots, which are useful in fern identification .

root

An organ in vascular plants that anchors the plant and enables it to absorb water and minerals from the soil .

foot

The portion of a bryophyte sporophyte that gathers sugars, amino acids, water, and minerals from the parent gametophyte via transfer cells; or one of the three main parts of a mollusc; a muscular structure usually used for movement.

sporophyte

In organisms (plants and some algae) that have alternation of generations, the multicellular diploid form that results from the union of gametes. Meiosis in the sporophyte produces haploid spores that develop into gametophytes

embryophyte

Alternate name for land plants that refers to their shared derived trait of multicellular, dependent embryos

angiosperm

A flowering plant, which forms seeds inside a protective chamber called an ovary

seedless vascular plant

An informal name for a plant that has vascular tissue but lacks seeds

gymnosperm

A vascular plant that bears naked seeds—seeds not enclosed in protective chambers .

antheridium

In plants, the male gametangium, a moist chamber in which gametes develop .

gametophore

The mature gamete- producing structure of a moss gametophyte

spore

In the life cycle of a plant or alga undergoing alternation of generations, a haploid cell produced in the sporophyte by meiosis

stoma

A microscopic pore surrounded by guard cells in the epidermis of leaves and stems that allows gas exchange between the environment and the interior of the plant .

gametophyte

In organisms (plants and some algae) that have alternation of generations, the multicellular haploid form that produces haploid gametes by mitosis . The haploid gametes unite and develop into sporophytes .

moss

A small, herbaceous, nonvascular plant that is a member of the phylum Bryophyta.

sporocyte

A diploid cell within a sporangium that undergoes meiosis and generates haploid spores; also called a spore mother cell .

liverwort

A small, herbaceous, nonvascular plant that is a member of the phylum Hepatophyta

proteonema

A mass of green, branched, one-cell-thick filaments produced by germinating moss spores .

capsule

In many prokaryotes, a dense and well-defined layer of polysaccharide or protein that surrounds the cell wall and is sticky, protecting the cell and enabling it to adhere to substrates or other cells; or the sporangium of a bryophyte (moss, liverwort, or hornwort) .

stigma

The sticky part of a flower’s carpel, which receives pollen grains

micropyle

A pore in the integuments of an ovule

ovule

A structure that develops within the ovary of a seed plant and contains the female gametophyte

flower

In an angiosperm, a specialized shoot with up to four sets of modified leaves, bearing structures that function in sexual reproduction

sepal

A modified leaf in angiosperms that helps enclose and protect a flower bud before it opens .

double fertilization

A mechanism of fertilization in angiosperms in which two sperm cells unite with two cells in the female gametophyte (embryo sac) to form the zygote and endosperm

conifer

A member of the largest gymnosperm phylum. Most conifers are cone-bearing trees, such as pines and firs .

seed

An adaptation of some terrestrial plants consisting of an embryo packaged along with a store of food within a protective coat

magnoliid

A member of the angiosperm clade that is most closely related to the combined eudicot and monocot clades. Extant examples are magnolias, laurels, and black pepper plants .

monocot

A member of a clade consisting of flowering plants that have one embryonic seed leaf, or cotyledon

pollination

The transfer of pollen to the part of a seed plant containing the ovules, a process required for fertilization .

cotyledon

A seed leaf of an angiosperm embryo. Some species have one cotyledon, others two

embryo sac

The female gametophyte of angiosperms, formed from the growth and division of the megaspore into a multicellular structure that typically has eight haploid nuclei

style

The stalk of a flower’s carpel, with the ovary at the base and the stigma at the top

petal

A modified leaf of a flowering plant. Petals are the often colorful parts of a flower that advertise it to insects and other pollinators .

stamen

The pollen-producing reproductive organ of a flower, consisting of an anther and a filament .

dicot

A term traditionally used to refer to flowering plants that have two embryonic seed leaves, or cotyledons. Recent molecular evidence indicates that dicots do not form a clade; species once classified as dicots are now grouped into eudicots, magnoliids, and several lineages of basal angiosperms .

carpel

The ovule-producing reproductive organ of a flower, consisting of the stigma, style, and ovary

pistil

A single carpel (a simple pistil) or a group of fused carpels (a compound pistil)

cross pollination

In angiosperms, the transfer of pollen from an anther of a flower on one plant to the stigma of a flower on another plant of the same species

endosperm

In angiosperms, a nutrient-rich tissue formed by the union of a sperm with two polar nuclei during double fertilization . This material provides nourishment to the developing embryo in angiosperm seeds .

eudicot

A member of a clade that contains the vast majority of flowering plants that have two embryonic seed leaves, or cotyledons

pollen grain

In seed plants, a structure consisting of the male gametophyte enclosed within a pollen wall .

basal angiosperm

A member of one of three clades of early-diverging lineages of extant flowering plants. Examples are Amborella, water lilies, and star anise and its relatives

filament

In an angiosperm, the stalk portion of the stamen, the pollen-producing reproductive organ of a flower

anther

In an angiosperm, the terminal pollen sac of a stamen, where pollen grains containing sperm-producing male gametophytes form

integument

Layer of sporophyte tissue that contributes to the structure of an ovule of a seed plant

ovary

In flowers, the portion of a carpel in which the egg-containing ovules develop; or in animals, the structure that produces female gametes and reproductive hormones .

fruit

A mature ovary of a flower. The fruit protects dormant seeds and often functions in their dispersal .

virus

An infectious particle incapable of replicating outside of a cell, consisting of an RNA or DNA genome surrounded by a protein coat (capsid) and, for some viruses, a membranous envelope

prion

An infectious agent that is a misfolded version of a normal cellular protein. Prions appear to increase in number by converting correctly folded versions of the protein to more prions

phage

A virus that infects bacteria; also called a bacteriophage

epidemic

a widespread outbreak of a disease

reverse transcriptase

An enzyme encoded by certain viruses (retroviruses) that uses RNA as a template for DNA synthesis .

capsid

The protein shell that encloses a viral genome. It may be rod-shaped, polyhedral, or more complex in shape

host range

The limited number of species whose cells can be infected by a particular virus .

lysogenic cycle

A type of phage replicative cycle in which the viral genome becomes incorporated into the bacterial host chromosome as a prophage, is replicated along with the chromosome, and does not kill the host

lytic cycle

A type of phage replicative cycle resulting in the release of new phages by lysis (and death) of the host cell .

endemic

Referring to a species that is confined to a specific geographic area

retrovirus

An RNA virus that replicates by transcribing its RNA into DNA and then inserting the DNA into a cellular chromosome; an important class of cancercausing viruses

provirus

A viral genome that is permanently inserted into a host genome

human immunodeficiency virus

The infectious agent that causes AIDS. HIV is a retrovirus

pandemic

a global epidemic

virulent phage

A phage that replicates only by a lytic cycle .

prophase

The first stage of mitosis, in which the chromatin condenses into discrete chromosomes visible with a light microscope, the mitotic spindle begins to form, and the nucleolus disappears but the nucleus remains intact .

temperate phage

A phage that is capable of replicating by either a lytic or lysogenic cycle

bacteriophage

A virus that infects bacteria; also called a phage

restriction enzyme

An endonuclease (type of enzyme) that recognizes and cuts DNA molecules foreign to a bacterium (such as phage genomes). The enzyme cuts at specific nucleotide sequences (restriction sites)

viral envelope

A membrane, derived from membranes of the host cell, that cloaks the capsid, which in turn encloses a viral genome .

vaccine

A harmless variant or derivative of a pathogen that stimulates a host’s immune system to mount defenses against the pathogen .

coelom

A body cavity lined by tissue derived only from mesoderm .

deuterostome development

In animals, a developmental mode distinguished by the development of the anus from the blastopore; often also characterized by radial cleavage and by the body cavity forming as outpockets of mesodermal tissue .

vertebrate

A chordate animal with vertebrae, the series of bones that make up the backbone

radial cleavage

A type of embryonic development in deuterostomes in which the planes of cell division that transform the zygote into a ball of cells are either parallel or perpendicular to the vertical axis of the embryo, thereby aligning tiers of cells one above the other

diploblastic

Having two germ layers