Categories
Coretan Kecil

Menanti yang Datang

SEMANGAT untuk sahabat semua yang sama-sama akan melanjutkan studi ke jenjang perkuliahan!!! Perjalanan kita dengan status siswa sudah tinggal menghitung hari, mungkin tanpa terasa dan tanpa sadar kita menjadi berstatus MAHAsiswa. Namanya juga MAHA tentu sesuai nama kita harus lebih besar daripada siswa. Bukan besar dari segi fisik saja, namun yang terpenting adalah besarnya pemikiran kita. Pemikiran yang besar akan memberi kekuatan untuk berkata hal yang besar manfaatnya, kata yang besar manfaatnya akan menggerakkan kita untuk melakukan tindakan yang bermanfaat, tindakan yang bermanfaat jika dilakukan terus menerus akan menjadi kebiasaan dan kebiasaan yang baik akan membentuk kita menjadi pribadi yang baik pula. Jadi siapkah kita berjuang bersama untuk meraih kemampuan berpikir besar? Tentu harus! Bukan maksa ya.. hehe..
Sahabat… Sudah tak lama lagi kita akan segera melepas seragam putih abu yang selalu dipakai setiap berburu ilmu. Bukan pakaian putih abunya yang kita rindukan, lebih dari itu kita akan rindu saat keadaan kelas ketika kita memakainya, sambil melihat sahabat sekelas, melihat mereka tertawa, melihat guru yang tak pernah mengeluh dalam membimbing kita, terima kasih Guruku… dan juga melihat semua keadaan kelas yang sudah pasti tak mungkin terulang lagi. SEMANGAT!!! Perpisahan bukan sekedar berpisah, seperti kata sahabat saya “Perpisahan adalah untuk menambah kerinduan” Luar biasa yang diucapkannya!!! 🙂
Nah sesuai dengan judul postingan kali ini saya pengen berbagi seputar impian nih. Setiap orang mempunyai keinginan, tapi tak semua orang yang mempunya impian. Mengapa demikian? Nih… Kata sahabat saya sesuatu yang kita inginkan itu namanya keinginan, Ya tentu donk, dan keinginan yang disertai dengan tindakan itulah impian. Kita bisa saja berkata bahwa kita punya impian untuk menjadi seorang juara dalam bidang yang kita geluti, tetapi selama tidak diikuti dengan tindakan keinginan itu tidak akan berubah menjadi kenyataan yang kita harapkan. Jangan takut untuk bermimpi, jangan takut mimpi kita ditertawakan oleh orang lain. Prinsipnya, kalau orang lain menertawakan impian yang kita miliki, impian yang sedang kita perjuangkan artinya orang itu belum memiliki pemikiran sebesar pemikiran kita. Masa bermimpi saja takut, bagaimana bisa menghadapi kehidupan yang nyata ini? Nanti Apa kata dunia??? Hehe… 
Kalau sudah punya mimpi, maka lukiskanlah mimpi itu secara detail. Gambarkan dengan indah, jelaskan pada diri sendiri kapan kita akan mendapatkan mimpi itu, tanggal berapa, di mana, pkpknya usahakan aturan 5W+1H nya terjawab deh. Penggambaran mimpi secara detail seperti itu sangat penting. Misalnya saja kita bertekad untuk bangun lebih pagi dari pada biasanya. Dalam pikiran kita hanya memikirkan – Saya harus bangun lebih pagi -,  hasilnya apa? Jam  1 malam kita sudah bangun, karena masih mlam kita tidur lagi, tidak lama kemudian kita bangun lagi, karena memang otak pikiran bawah sadar kita bingung menerjemahkan tekad kita. Berbeda lagi hasilnya jika kita bertekad untuk bangun lebih awal dengan berpikir – Saya harus bangun pukul 3, mau melanjutkan membaca buku biologi (misalnya) karena besok ada ulangan-, hasilnya apa? Apa? Tetap kesiangan juga? Ada yang salah dengan tekadmu… Haha…
Mimpi kita ibarat air, diri kita ibarat wadahnya. Untuk menampung air yang banyak tentu perlu sebuah wadah yang berukuran besar, begitu pun dengan mimpi besar yang kita miliki, untuk meraihnya kita juga harus berusaha menjadi pribadi yang berpikir besar. Kalau di buku ada juga kan tentang Berpikir dan Berjiwa Besar. Bukan promosi… 

Sekarang muncul pertanyaan yang baru. Bagaimana cara kita menjadi pribadi yang berpikir besar? Singkat saja, jadilah pribadi yang berpegangan ahlussunah wal jama’ah yaitu percaya pada takdir Allah, tetapi juga percaya pada ikhtiar yang dianjurkanNya. Masih ingat rumus pada postingan yang lalu? I+D=T Artinya? Cari sendiri ya kan supaya ikhtiar. Hehehe… Waduh akhirnya beres juga postingan ini. Lho kok simpel banget? Iya lah karena rumus I+D=T sudah muncul artinya ilmu untuk menjadi bekal selama penantian sudah kita daptkan. Ya… Bagi saya I+D=T adalah sesuatu yang luar biasa… 🙂 


Categories
Coretan Kecil

Mulai dari Akhir

Ini adalah awal dari postingan saya di abuddy-26 ini. Saya kurang yakin dengan apa yang saya tulis ini sapi saya sangat yakin bahwa saya memang harus menuliskannya.
Kita semua tentu pernah merasa sakitnya sebuah kekecewaan, katakanlah kegagalan. Memang kegagalan itu adalah keberhasilan yang tertunda. Tapi, kalau keberhasilan itu terus menerus tertunda alias gagal terus!!! Bagaimana ayo?? Ya banyak diantara kita yang setelah mengalami kegagalan yang bertubi-tubi merasa bahwa dirinya ditakdirkan untuk menjadi orang yang gagal. Huh… Na’udzubillah! Tergantung kepada bagaimana kita menyikapinya. Apakah dengan menurunkan W (usaha)  dan menaikan V (kecepatan) atau mungkin sebaliknya, murung, dan menujukkan gejala 5L (Lemah, Letih, Lesu, Leuleus, Letoy) wah.. bisa jadi 7L tuh.. Hehe.
Terkadang kita terjerumus pada pandangan orang kebanyakan, yaitu melihat seseorang itu dari kesuksesannya, bukan dari kegagalannya. Kita melihat seseorang berhasil maka muncul lah keinginan untuk menjadi seperti dirinya, tanpa ingin tahu bagaimana perjuangannya. Sahabat meskipun memang agama kita mnganjurkan kita untuk tidak terjatuh pada lubang yang sama, tapi janganlah menghitung berapa kali kita terjatuh pada lubang yang sama itu, tapi hitunglah berapa kali kita bangun dan bangkit lagi dari lubang itu.
Ada juga seorang Fisikawan wanita yang menyatakan bahwa “kesempatan itu tidaka datang satu kali, tetapi 2, 3, bahkan bisa sampai beberapa kali, selama V = Konstan dan W = Semangat”. Jadi, tidak ada lagi alasan bagi kita untuk tidak segera bangkit dari keterpurukan ini. Keterpurukan yang saat ini sedang memayungi generasi muda, tidak semua generasi muda, tapi mekipun hanya segelintir saja ini merupakan kewajiban kita untuk membersihkannya dan menggantikannya menjadi generasi harapan, agen perubahan yang membawa perubahan pada peradaban. Kita harus bisa merebut kembalai api kejayaan yang telah dinyalakan oleh generasi muda islam dahulu. hehe… Koko jadi terbakar begini ya semangat saya. Memang enak kalau menulis malam-malam begini, suasananya sepi dan tenang, tapi ngantuk… Hehe.. Dah…

Categories
Kamus Biologi

Abjad Z

JEJAK
MAHASISWA
..:: KAMUS BIOLOGI JEJAK MAHASISWA ::..
Dibuat
12/19/2011
A B C D E F G H I J K L M
N O P Q R S T U V W X Y Z
Glosarium ini diambil dari Buku Biologi Campbell | Jejak Mahasiswa

zygote
The diploid product of the union of haploid gametes in conception; a fertilized egg.
Categories
Kamus Biologi

Abjad Y

JEJAK
MAHASISWA
..:: KAMUS BIOLOGI JEJAK MAHASISWA ::..
Dibuat
12/19/2011
A B C D E F G H I J K L M
N O P Q R S T U V W X Y Z
Glosarium ini diambil dari Buku Biologi Campbell | Jejak Mahasiswa

yeast 
A unicellular fungus that lives in liquid or moist habitats, primarily reproducing asexually by simple cell division or by budding of a parent cell.
yolk sac 
One of four extraembryonic membranes that supports embryonic development; the first site of blood cells and circulatory system function.
Categories
Kamus Biologi

Abjad X

JEJAK
MAHASISWA
..:: KAMUS BIOLOGI JEJAK MAHASISWA ::..
Dibuat
12/19/2011
A B C D E F G H I J K L M
N O P Q R S T U V W X Y Z
Glosarium ini diambil dari Buku Biologi Campbell | Jejak Mahasiswa

xylem 
(ZY-lum) The tube-shaped, nonliving portion of the vascular system in plants that carries water and minerals from the roots to the rest of the plant.
Categories
Kamus Biologi

Abjad W

JEJAK
MAHASISWA
..:: KAMUS BIOLOGI JEJAK MAHASISWA ::..
Dibuat
12/19/2011
A B C D E F G H I J K L M
N O P Q R S T U V W X Y Z
Glosarium ini diambil dari Buku Biologi Campbell | Jejak Mahasiswa

water potential
The physical property predicting the direction in which water will flow, governed by solute concentration and applied pressure.
water vascular system
A network of hydraulic canals unique to echinoderms that branches into extensions called tube feet, which function in locomotion, feeding, and gas exchange.
wavelength
The distance between crests of waves, such as those of the electromagnetic spectrum.
wild type
An individual with the normal phenotype.
wobble
A violation of the base-pairing rules in that third nucleotide (5′ end) of a tRNA anticodon can form hydrogen bonds with more than one kind of base in the third position (3′ end) of a codon.
Categories
Kamus Biologi

Abjad V

JEJAK
MAHASISWA
..:: KAMUS BIOLOGI JEJAK MAHASISWA ::..
Dibuat
12/19/2011
A B C D E F G H I J K L M
N O P Q R S T U V W X Y Z
Glosarium ini diambil dari Buku Biologi Campbell | Jejak Mahasiswa

vaccine
A harmless variant or derivative of a pathogen that stimulates a host’s immune system to mount defenses against the pathogen.
vacuole
A membrane-enclosed sac taking up most of the interior of a mature plant cell and containing a variety of substances important in plant reproduction, growth, and development.
vagina
Part of the female reproductive system between the uterus and the outside opening; the birth canal in mammals; also accommodates the male’s penis and receives sperm during copulation.
valence shell
The outermost energy shell of an atom, containing the valence electrons involved in the chemical reactions of that atom.
vas deferens
The tube in the male reproductive system in which sperm travel from the epididymis to the urethra.
vascular cambium
A continuous cylinder of meristematic cells surrounding the xylem and pith that produces secondary xylem and phloem.
vascular plants
Plants with vascular tissue, consisting of all modern species except the mosses and their relatives.
vascular tissue system
A system formed by xylem and phloem throughout the plant, serving as a transport system for water and nutrients, respectively.
vascular tissue
Plant tissue consisting of cells joined into tubes that transport water and nutrients throughout the plant body.
vegetative reproduction
Cloning of plants by asexual means.
vein
A vessel that returns blood to the heart.
ventilation
Any method of increasing contact between the respiratory medium and the respiratory surface.
vertebrate
A chordate animal with a backbone: the mammals, birds, reptiles, amphibians, and various classes of fishes.
vessel element
A specialized short, wide cell in angiosperms; arranged end to end, they form continuous tubes for water transport.
vestigial organ
A type of homologous structure that is rudimentary and of marginal or no use to the organism.
viroid
(VY-roid) A plant pathogen composed of molecules of naked RNA only several hundred nucleotides long.
visceral muscle
Smooth muscle found in the walls of the digestive tract, bladder, arteries, and other internal organs.
visible light
That portion of the electromagnetic spectrum detected as various colors by the human eye, ranging in wavelength from about 400 nm to about 700 nm.
vitalism
The belief that natural phenomena are governed by a life force outside the realm of physical and chemical laws.
vitamin
An organic molecule required in the diet in very small amounts; vitamins serve primarily as coenzymes or parts of coenzymes.
viviparous
(vy-VIP-er-us) Referring to a type of development in which the young are born alive after having been nourished in the uterus by blood from the placenta.
voltage-gated channel
Ion channel in a membrane that opens and closes in response to changes in membrane potential (voltage); the sodium and potassium channels of neurons are examples.
Categories
Kamus Biologi

Abjad U

JEJAK
MAHASISWA
..:: KAMUS BIOLOGI JEJAK MAHASISWA ::..
Dibuat
12/19/2011
A B C D E F G H I J K L M
N O P Q R S T U V W X Y Z
Glosarium ini diambil dari Buku Biologi Campbell | Jejak Mahasiswa

ultimate causation
The hypothetical evolutionary explanation for the existence of a certain pattern of animal behavior.
unsaturated fatty acid
A fatty acid possessing one or more double bonds between the carbons in the hydrocarbon tail. Such bonding reduces the number of hydrogen atoms attached to the carbon skeleton.
urea
A soluble form of nitrogenous waste excreted by mammals and most adult amphibians.
ureter
A duct leading from the kidney to the urinary bladder.
urethra
A tube that releases urine from the body near the vagina in females or through the penis in males; also serves in males as the exit tube for the reproductive system.
uric acid
An insoluble precipitate of nitrogenous waste excreted by land snails, insects, birds, and some reptiles.
urochordate
A chordate without a backbone, commonly called a tunicate, a sessile marine animal.
uterus
A female reproductive organ where eggs are fertilized and/or development of the young occurs.
Categories
Kamus Biologi

Abjad T

JEJAK
MAHASISWA
..:: KAMUS BIOLOGI JEJAK MAHASISWA ::..
Dibuat
12/19/2011
A B C D E F G H I J K L M
N O P Q R S T U V W X Y Z
Glosarium ini diambil dari Buku Biologi Campbell | Jejak Mahasiswa

T cell
A type of lymphocyte responsible for cell-mediated immunity that differentiates under the influence of the thymus.
taiga
(TY-guh) The coniferous or boreal forest biome, characterized by considerable snow, harsh winters, short summers, and evergreen trees.
taxis
(TAKS-iss) A movement toward or away from a stimulus.
taxon
(plural, taxa) The named taxonomic unit at any given level.
taxonomy
The branch of biology concerned with naming and classifying the diverse forms of life.
telomere
The protective structure at each end of a eukaryotic chromosome. Specifically, the tandemly repetitive DNA (see repetitive DNA) at the end of the chromosomeÕs DNA molecule.
telophase
The fourth and final stage of mitosis, during which daughter nuclei form at the two poles of a cell. Telophase usually occurs together with cytokinesis.
temperate deciduous forest
A biome located throughout midlatitude regions where there is sufficient moisture to support the growth of large, broad-leaf deciduous trees.
temperate virus
A virus that can reproduce without killing the host.
temperature
A measure of the intensity of heat in degrees, reflecting the average kinetic energy of the molecules.
tendon
A type of fibrous connective tissue that attaches muscle to bone.
terminator
A special sequence of nucleotides in DNA that marks the end of a gene; it signals RNA polymerase to release the newly made RNA molecule, which then departs from the gene.
tertiary structure
(TUR-shee-air-ee) Irregular contortions of a protein molecule due to interactions of side chains involved in hydrophobic interactions, ionic bonds, hydrogen bonds, and disulfide bridges.
testcross
Breeding of an organism of unknown genotype with a homozygous recessive individual to determine the unknown genotype. The ratio of phenotypes in the offspring determines the unknown genotype.
testis
(plural, testes) The male reproductive organ, or gonad, in which sperm and reproductive hormones are produced.
testosterone
The most abundant androgen hormone in the male body.
tetanus
(TET-un-us) The maximal, sustained contraction of a skeletal muscle, caused by a very fast frequency of action potentials elicited by continual stimulation.
tetrapod
A vertebrate possessing two pairs of limbs, such as amphibians, reptiles, birds, and mammals.
thalamus
(THAL-uh-mus) One of two integrating centers of the vertebrate forebrain. Neurons with cell bodies in the thalamus relay neural input to specific areas in the cerebral cortex and regulate what information goes to the cerebral cortex.
thermoregulation
The maintenance of internal temperature within a tolerable range.
thick filament
A filament composed of staggered arrays of myosin molecules; a component of myofibrils in muscle fibers.
thigmomorphogenesis
A response in plants to chronic mechanical stimulation, resulting from increased ethylene production; an example is thickening stems in response to strong winds.
thigmotropism
(THIG-moh-TROH-piz-um) The directional growth of a plant in relation to touch.
threshold potential
The potential an excitable cell membrane must reach for an action potential to be initiated.
thylakoid
(THY-luh-koid) A flattened membrane sac inside the chloroplast, used to convert light energy to chemical energy.
thymus
(THY-mus) An endocrine gland in the neck region of mammals that is active in establishing the immune system; secretes several messengers, including thymosin, that stimulate T cells.
thyroid gland
An endocrine gland that secretes iodine-containing hormones (T3 and T4), which stimulate metabolism and influence development and maturation in vertebrates, and cacitonin, which lowers blood calcium levels in mammals.
thyroid-stimulating hormon
(TSH) A hormone produced by the anterior pituitary that regulates the release of thyroid hormones.
Ti plasmid
A plasmid of a tumor-inducing bacterium that integrates a segment of its DNA into the host chromosome of a plant; frequently used as a carrier for genetic engineering in plants.
tight junction
A type of intercellular junction in animal cells that prevents the leakage of material between cells.
tissue
An integrated group of cells with a common structure and function.
tonoplast
A membrane that encloses the central vacuole in a plant cell, separating the cytosol from the cell sap.
totipotency
The ability of embryonic cells to retain the potential to form all parts of the animal.
trace element
An element indispensable for life but required in extremely minute amounts.
trachea
(TRAY-kee-uh) The windpipe; that portion of the respiratory tube that has C-shaped cartilagenous rings and passes from the larynx to two bronchi.
tracheae
(TRAY-kee-ee) Tiny air tubes that branch throughout the insect body for gas exchange.
tracheal system
A gas exchange system of branched, chitin-lined tubes that infiltrate the body and carry oxygen directly to cells in insects.
tracheid
(TRAY-kee-id) A water-conducting and supportive element of xylem composed of long, thin cells with tapered ends and walls hardened with lignin.
transcription factor
A regulatory protein that binds to DNA and stimulates transcription of specific genes.
transcription
The synthesis of RNA on a DNA template.
transfer RNA
(tRNA) An RNA molecule that functions as an interpreter between nucleic acid and protein language by picking up specific amino acids and recognizing the appropriate codons in the mRNA.
transformation
(1) The conversion of a normal animal cell to a cancerous cell. (2) A phenomenon in which external DNA is assimilated by a cell.
translation
(1) The conversion of a normal animal cell to a cancerous cell. (2) A phenomenon in which external DNA is assimilated by a cell.
translocation
(1) An aberration in chromosome structure resulting from an error in meiosis or from mutagens; attachment of a chromosomal fragment to a nonhomologous chromosome. (2) During protein synthesis, the third stage in the elongation cycle when the RNA carrying the growing polypeptide moves from the A site to the P site on the ribosome. (3) The transport via phloem of food in a plant.
transpiration
The evaporative loss of water from a plant.
transposon
(trans-POH-son) A transposable genetic element; a mobile segment of DNA that serves as an agent of genetic change.
triplet code
A set of three-nucleotide-long words that specify the amino acids for polypeptide chains.
triploblastic
Possessing three germ layers: the endoderm, mesoderm, and ectoderm. Most eumetazoa are triploblastic.
trophic level
The division of species in an ecosystem on the basis of their main nutritional source. The trophic level that ultimately supports all others consists of autotrophs, or primary producers.
trophic structure
The different feeding relationships in an ecosystem that determine the route of energy flow and the pattern of chemical cycling.
trophoblast
The outer epithelium of the blastocyst, which forms the fetal part of the placenta.
tropic hormone
A hormone that has another endocrine gland as a target.
tropical rain forest
The most complex of all communities, located near the equator where rainfall is abundant; harbors more species of plants and animals than all other terrestrial biomes combined.
tropism
A growth response that results in the curvature of whole plant organs toward or away from stimuli due to differential rates of cell elongation.
tumor
A mass that forms within otherwise normal tissue, caused by the uncontrolled growth of a transformed cell.
tumor-suppressor gene
A gene whose protein products inhibit cell division, thereby preventing uncontrolled cell growth (cancer).
tundra
A biome at the extreme limits of plant growth; at the northernmost limits, it is called arctic tundra, and at high altitudes, where plant forms are limited to low shrubby or matlike vegetation, it is called alpine tundra.
turgid
(TUR-jid) Firm; walled cells become turgid as a result of the entry of water from a hypotonic environment.
turgor pressure
The force directed against a cell wall after the influx of water and the swelling of a walled cell due to osmosis.
Categories
Kamus Biologi

Abjad S

JEJAK
MAHASISWA
..:: KAMUS BIOLOGI JEJAK MAHASISWA ::..
Dibuat
12/19/2011
A B C D E F G H I J K L M
N O P Q R S T U V W X Y Z
Glosarium ini diambil dari Buku Biologi Campbell | Jejak Mahasiswa

S phase
The synthesis phase of the cell cycle, constituting the portion of interphase during which DNA is replicated.
SA (sinoatrial) node
The pacemaker of the heart, located in the wall of the right atrium. At the base of the wall separating the two atria is another patch of nodal tissue called the atrioventricular node (AV).
saltatory conduction
(SAHL-tuh-TOR-ee) Rapid transmission of a nerve impulse along an axon resulting from the action potential jumping from one node of Ranvier to another, skipping the myelin-sheathed regions of membrane.
saprobe
An organism that acts as a decomposer by absorbing nutrients from dead organic matter.
sarcomere
(SAR-koh-meer) The fundamental, repeating unit of striated muscle, delimited by the Z lines.
sarcoplasmic reticulum
(SAR-koh-PLAZ-mik reh-TIK-yoo-lum) A modified form of endoplasmic reticulum in striated muscle cells that stores calcium used to trigger contraction during stimulation.
saturated fatty acid
A fatty acid in which all carbons in the hydrocarbon tail are connected by single bonds, thus maximizing the number of hydrogen atoms that can attach to the carbon skeleton.
savanna
(suh-VAN-uh) A tropical grassland biome with scattered individual trees, large herbivores, and three distinct seasons based primarily on rainfall, maintained by occasional fires and drought.
Schwann cells
A chain of supporting cells enclosing the axons of many neurons and forming an insulating layer called the myelin sheath.
sclereid
(SKLER-ee-id) A short, irregular sclerenchyma cell in nutshells and seed coats and scattered through the parenchyma of some plants.
sclerenchyma cell
(skler-EN-kim-uh) A rigid, supportive plant cell type usually lacking protoplasts and possessing thick secondary walls strengthened by lignin at maturity.
second law of thermodynamics
The principle whereby every energy transfer or transformation increases the entropy of the universe. Ordered forms of energy are at least partly converted to heat, and in spontaneous reactions, the free energy of the system also decreases.
second messenger
A small, nonprotein, water-soluble molecule or ion, such as calcium ion or cyclic AMP, that relays a signal to a cell’s interior in response to a signal received by a signal receptor protein.
secondary compound
A chemical compound synthesized through the diversion of products of major metabolic pathways for use in defense by prey species.
secondary consumer
A member of the trophic level of an ecosystem consisting of carnivores that eat herbivores.
secondary growth
The increase in girth of the stems and roots of many plants, especially woody, perennial dicots.
secondary immune response
The immune response elicited when an animal encounters the same antigen at some later time. The secondary immune response is more rapid, of greater magnitude, and of longer duration than the primary immune response.
secondary productivity
The rate at which all the heterotrophs in an ecosystem incorporate organic material into new biomass, which can be equated to chemical energy.
secondary structure
The localized, repetitive coiling or folding of the polypeptide backbone of a protein due to hydrogen bond formation between peptide linkages.
secretion
(1) The discharge of molecules synthesized by the cell. (2) In the vertebrate kidney, the discharge of wastes from the blood into the filtrate from the nephron tubules.
sedimentary rock
(SED-eh-MEN-tar-ee) Rock formed from sand and mud that once settled in layers on the bottom of seas, lakes, and marshes. Sedimentary rocks are often rich in fossils.
seed
An adaptation for terrestrial plants consisting of an embryo packaged along with a store of food within a resistant coat.
selection coefficient
The difference between two fitness values, representing a relative measure of selection against an inferior genotype.
selective permeability
A property of biological membranes that allows some substances to cross more easily than others.
self-incompatibility
The capability of certain flowers to block fertilization by pollen from the same or a closely related plant.
semen
(SEE-men) The fluid that is ejaculated by the male during orgasm; contains sperm and secretions from several glands of the male reproductive tract.
semicircular canals
A three-part chamber of the inner ear that functions in maintaining equilibrium.
semilunar valve
A valve located at the two exits of the heart, where the aorta leaves the left ventricle and the pulmonary artery leaves the right ventricle.
seminal vesicle
(SEM-ih-nul VES-ih-cul) A gland in males that secretes a fluid (a component of semen) that lubricates and nourishes sperm.
seminiferous tubules
(SEM-in-IF-er-us) Highly coiled tubes in the testes in which sperm are produced.
sensation
An impulse sent to the brain from activated receptors and sensory neurons.
sensory neuron
A nerve cell that receives information from the internal and external environments and transmits the signals to the central nervous system.
sensory receptor
A specialized structure that responds to specific stimuli from an animal’s external or internal environment; transmits the information of an environmental stimulus to the animal’s nervous system by converting stimulus energy to the electrochemical energy of action potentials.
sepal
(SEE-pul) A whorl of modified leaves in angiosperms that encloses and protects the flower bud before it opens.
sex chromosomes
The pair of chromosomes responsible for determining the sex of an individual.
sex-linked genes
A gene located on a sex chromosome.
sexual dimorphism
(dy-MOR-fiz-um) A special case of polymorphism based on the distinction between the secondary sex characteristics of males and females.
sexual reproduction
A type of reproduction in which two parents give rise to offspring that have unique combinations of genes inherited from the gametes of the two parents.
sexual selection
Selection based on variation in secondary sex character-istics, leading to the enhancement of sexual dimorphism.
shoot system
The aerial portion of a plant body, consisting of stems, leaves, and flowers.
short-day plant
A plant that flowers, usually in late summer, fall, or winter, only when the light period is shorter than a critical length.
sieve-tube member
A chain of living cells that form sieve tubes in phloem.
sign stimulus
An external sensory stimulus that triggers a fixed action pattern.
signal sequence
A stretch of amino acids on polypeptides that targets proteins to specific destinations in eukaryotic cells.
signal-transduction pathway
A mechanism linking a mechanical or chemical stimulus to a cellular response.
sister chromatids
(KROH-muh-tidz) Replicated forms of a chromosome joined together by the centromere and eventually separated during mitosis or meiosis II.
skeletal muscle
Striated muscle generally responsible for the voluntary movements of the body.
sliding-filament model
The theory explaining how muscle contracts, based on change within a sarcomere, the basic unit of muscle organization, stating that thin (actin) filaments slide across thick (myosin) filaments, shortening the sarcomere; the shortening of all sarcomeres in a myofibril shortens the entire myofibril.
small nuclear ribonucleoprotein
(snRNP) (RY-boh-NOO-klee-oh-pro-teen) One of a variety of small particles in the cell nucleus, composed of RNA and protein molecules; functions are not fully understood, but some form parts of spliceosomes, active in RNA splicing.
smooth ER
That portion of the endoplasmic reticulum that is free of ribosomes.
smooth muscle
A type of muscle lacking the striations of skeletal and cardiac muscle because of the uniform distribution of myosin filaments in the cell.
snynaptic knob
The relay point at the tip of a transmitting neuron’s axon, where signals are sent to another neuron or to an effector.
sociobiology
The study of social behavior based on evolutionary theory.
sodium-potassium pump
A special transport protein in the plasma membrane of animal cells that transports sodium out of and potassium into the cell against their concentration gradients.
solute
(SOL-yoot) A substance that is dissolved in a solution.
solution
A homogeneous, liquid mixture of two or more substances.solvent The dissolving agent of a solution. Water is the most versatile solvent known.
somatic cell
(soh-MAT-ik) Any cell in a multicellular organism except a sperm or egg cell.
somatic nervous system
The branch of the motor division of the vertebrate peripheral nervous system composed of motor neurons that carry signals to skeletal muscles in response to external stimuli.
Southern blotting
A hybridization technique that enables researchers to determine the presence of certain nucleotide sequences in a sample of DNA.
speciation
(SPEE-see-AY-shun) The origin of new species in evolution.
species diversity
The number and relative abundance of species in a biological community.
species richness
The number of species in a biological community.
species selection
A theory maintaining that species living the longest and generating the greatest number of species determine the direction of major evolutionary trends.
species
A particular kind of organism; members possess similar anatomical characteristics and have the ability to interbreed.
specific heat
The amount of heat that must be absorbed or lost for 1 g of a substance to change its temperature 1 degree Celsius.
spectrophotometer
An instrument that measures the proportions of light of different wavelengths absorbed and transmitted by a pigment solution.
sperm
A male gamete.
spermatogenesis
The continuous and prolific production of mature sperm cells in the testis.
sphincter
(SFINK-ter) A ringlike valve, consisting of modified muscles in a muscular tube, such as a digestive tract; closes off the tube like a drawstring.
spindle
An assemblage of microtubules that orchestrates chromosome movement during eukaryotic cell division.
spiral cleavage
A type of embryonic development in protostomes, in which the planes of cell division that transform the zygote into a ball of cells occur obliquely to the polar axis, resulting in cells of each tier sitting in the grooves between cells of adjacent tiers.
spliceosome
(SPLY-see-oh-some) A complex assembly that interacts with the ends of an RNA intron in splicing RNA; releases an intron and joins two adjacent exons.
sporangium
(plural, sporangia) A capsule in fungi and plants in which meiosis occurs and haploid spores develop.
spore
In the life cycle of a plant or alga undergoing alternation of generations, a meiotically produced haploid cell that divides mitotically, generating a multicellular individual, the gametophyte, without fusing with another cell.
sporophyte
The multicellular diploid form in organisms undergoing alternation of generations that results from a union of gametes and that meiotically produces haploid spores that grow into the gametophyte generation.
stabilizing selection
Natural selection that favors intermediate variants by acting against extreme phenotypes.
stamen
The pollen-producing male reproductive organ of a flower, consisting of an anther and filament.
starch
A storage polysaccharide in plants consisting entirely of glucose.
statocyst
(STAT-eh-SIST) A type of mechanoreceptor that functions in equilibrium in invertebrates through the use of statoliths, which stimulate hair cells in relation to gravity.
stele
The central vascular cylinder in roots where xylem and phloem are located.
stereoisomer
A molecule that is a mirror image of another molecule with the same molecular formula.
steroids
A class of lipids characterized by a carbon skeleton consisting of four rings with various functional groups attached.
stoma
(plural, stomata) 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.
strict aerobe
(AIR-obe) An organism that can survive only in an atmosphere of oxygen, which is used in aerobic respiration.
strict anaerobe
An organism that cannot survive in an atmosphere of oxygen. Other substances, such as sulfate or nitrate, are the terminal electron acceptors in the electron transport chains that generate their ATP.
stroma
The fluid of the chloroplast surrounding the thylakoid membrane; involved in the synthesis of organic molecules from carbon dioxide and water.
stromatolite
Rock made of banded domes of sediment in which are found the most ancient forms of life: prokaryotes dating back as far as 3.5 billion years.
structural formula
A type of molecular notation in which the constituent atoms are joined by lines representing covalent bonds.
substrate
The substance on which an enzyme works.
substrate-level phosphorylation
The formation of ATP by directly transferring a phosphate group to ADP from an intermediate substrate in catabolism.
summation
A phenomenon of neural integration in which the membrane potential of the postsynaptic cell in a chemical synapse is determined by the total activity of all excitatory and inhibitory presynaptic impulses acting on it at any one time.
suppressor T cell
(TS) A type of T cell that causes B cells as well as other cells to ignore antigens.
surface tension
A measure of how difficult it is to stretch or break the surface of a liquid. Water has a high surface tension because of the hydrogen bonding of surface molecules.
survivorship curve
A plot of the number of members of a cohort that are still alive at each age; one way to represent age-specific mortality.
suspension-feeder
An aquatic animal, such as a clam or a baleen whale, that sifts small food particles from the water.
sustainable agriculture
Long-term productive farming methods that are environmentally safe.
swim bladder
An adaptation, derived from a lung, that enables bony fishes to adjust their density and thereby control their buoyancy.
symbiont
(SIM-by-ont) The smaller participant in a symbiotic relationship, living in or on the host.
symbiosis
An ecological relationship between organisms of two different species that live together in direct contact.
sympathetic division
One of two divisions of the autonomic nervous system of vertebrates; generally increases energy expenditure and prepares the body for action.
sympatric speciation
A mode of speciation occurring as a result of a radical change in the genome that produces a reproductively isolated subpopulation in the midst of its parent population.
symplast
In plants, the continuum of cytoplasm connected by plasmodesmata between cells.
synapomorphies
Shared derived characters; homologies that evolved in an ancestor common to all species on one branch of a fork in a cladogram, but not common to species on the other branch.
synapse
(SIN-aps) The locus where one neuron communicates with another neuron in a neural pathway; a narrow gap between a synaptic terminal of an axon and a signal-receiving portion (dendrite or cell body) of another neuron or effector cell. Neurotransmitter molecules released by synaptic terminals diffuse across the synapse, relaying messages to the dendrite or effector.
synapsis
The pairing of replicated homologous chromosomes during prophase I of meiosis.
synaptic cleft
A narrow gap separating the synaptic knob of a transmitting neuron from a receiving neutron to an effector.
synaptic terminal
A bulb at the end of an axon in which neurotransmitter molecules are stored and released.
syngamy
(SIN-gam-ee) The process of cellular union during fertilization.
systematics
The branch of biology that studies the diversity of life; encompasses taxonomy and is involved in reconstructing phylogenetic history.
systemic acquired resistance
(SAR) A defensive response in infected plants that helps protect healthy tissue from pathogenic invasion.
systemic acquired resistance
(SAR) A defensive response in infected plants that helps protect healthy tissue from pathogenic invasion.
systole
(SIS-toh-lee) The stage of the heart cycle in which the heart muscle contracts and the chambers pump blood.