Absorption: the movement of nutrients out of the lumen of the gut into the body bile salts: organic compounds derived from cholesterol that are secreted by the liver into the gut lumen and that emulsify fats
Accommodation: changing the shape of the lens in order to keep objects at different distances focused on the retina
Adaptation: the possession by organisms of characteristics that suit them to their environment or their way of life
Adenosine triphosphate (ATP): a molecule produced in the cell that provides energy for cell processes
Aging: A process common to all living organisms, eventually resulting in death or conclusion of the life cycle
Allele: alternative forms of a single gene chromosome: a long strand of DNA with supporting proteins, that contains many genes
Alveoli: the milk-producing areas within the mammary glands
Alveolus: the thin-walled, saclike lung structure where gas exchange takes place
Amino acid: the subunit that makes up larger molecules called proteins
Amplexus: a form of pseudocopulation seen in amphibians, where the male mounts and grasps the female so that their cloacae are aligned, and eggs and sperm are released into the water in close proximity and at the same time
Amygdala: subcortical brain structure related to emotional expression anthropomorphism: attributing human characteristics to animal behavior
Androgens: the general term for a variety of male sex hormones, such as testosterone and dihydrotestosterone
Anisogamy: reproduction using gametes unequal in size or motility asexual
Anosmia: the clinical term for the inability to detect odors
Anterior pituitary gland: the front portion of the pituitary gland, which is attached to the base of the brain; the source of luteinizing hormone (LH) and follicle stimulating hormone (FSH)
Anthropomorphism: attributing human characteristics or states of mind to animals
Antibody: protein produced by lymphocytes, with specificity for a particular antigen
Antigen: chemical that stimulates the immune system to respond in a very specific manner
Aorta: the major arterial trunk, into which the left ventricle of the heart pumps its blood for transport to the body
Apes: large, tailless, semierect anthropoid primates, including chimpanzees, gorillas, gibbons, orangutans, and their direct ancestors—but excluding man and his direct
Aposematic coloration: brightly colored warning coloration that toxic species use to advertise their distastefulness to would-be predators
Archenteron: the primitive gut cavity formed by the invagination of the blastula; the cavity of the gastrula
Arrhenius equation: a mathematical function that relates the rate of a reaction to the energy required to initiate the reaction and the absolute temperature at which it is carried out.
Artery: a blood channel with thick muscular walls which transports blood from the heart to various parts of the body
Articular: pertaining to bone joints bone: the dense, semirigid, calcified connective tissue which is the main component of the skeletons of all adult vertebrates
Atria: the two chambers of the heart, which receive venous blood from the body (via the right atrium) or oxygenated blood from the lungs (left atrium)
Australopithecines: nonhuman hominids, commonly regarded as ancestral to man
Autotomy: the self-induced release of a body part mimicry: a type of defense in which an organism gains protection from predators by looking like a dangerous or distasteful species
Bacteria: single-celled microorganisms that are often the cause of infectious diseases in animals
Binocular vision: the ability to utilize image information from both eyes to form a single image with depth information
Biodiversity: the total of all living organisms in an environment
Blastula: an early stage of an embryo which is shaped like a hollow ball in some animals and a small, flattened disc in others; contains a cavity called the blastocoel
Brainstem: lowest or most posterior portion of the vertebrate brain, including midbrain, pons, and medulla oblongata; controls “housekeeping” functions such as breathing and heartbeat
Calcification: calcium deposition, mostly as calcium carbonate, into the cartilage and other bone-forming tissue, which facilitates its conversion into bone
Capillaries: the very fine vessels in various tissues, which connect arterioles with venules; it is here that the exchange between blood and the extracellular fluid takes place
Carbohydrate: an organic molecule containing only carbon, hydrogen, and oxygen in a 1:2:1 ratio; often defined as a simple sugar or any substance yielding a simple sugar upon hydrolysis
Cardiac output: the amount of blood ejected by the left ventricle into the aorta per minute
Cartilage: elastic, fibrous connective tissue which is the main component of fetal vertebrate skeletons, turns mostly to bone, and remains attached to the articular bone surfaces
Catalyst: a chemical species that initiates or speeds up a chemical reaction but is not itself consumed in the reaction.
Catastrophism: a geological theory explaining the earth’s history as resulting from great cataclysms (floods, earthquakes, and the like) on a scale not now observed
Cell-mediated immunity: production of lymphocytes that specifically kill cells with foreign antigens on their surface
Cerebellum: second largest part of the brain, manages fine muscle control and muscle memories
Cerebrum: largest part of most vertebrate brains, with areas that control vocalizations, vision, hearing, smell, and taste, as well as voluntary skeletal muscle movements
Cetaceans: plant-eating marine mammals, such as whales, dolphins, and porpoises marine mammals: part of the class of mammals that adapted to life in the sea
Chemical reaction: a process in which the molecules of two or more chemical species interact with each other in a way that causes the electrons in the bonds between atoms to be rearranged, resulting in changes to the chemical identities of the materials.
Chemoreceptor: specialized nervous tissue that senses changes in pH(hydrogen ions) and oxygen
Chemotaxis: an oriented response toward or away from chemicals
Chorion: the outer cellular layer of the embryo sac of reptiles, birds, and mammals; the term was coined by Aristotle
Chromatophores: pigment-producing cells
Chromophore: the molecule which interacts with opsin; absorption of light changes the interaction and starts the phototransduction cascade
Chromosome: a molecule of deoxyribonucleic acid (DNA) that contains a string of genes, which consist of coded information essential for all cell functions, including the creation of new life
Class: the taxonomic category composed of related genera; closely related classes form a phylum or division
Cleavage: cell division in the early embryo that, unlike division in adults, involves little or no growth between divisions
Cloaca: a common opening for the reproductive, urinary, and digestive systems
Clone: an organism that is genetically identical to the original organism from which it was derived
Cognition: Ability to perceive or understand death: the cessation of all body and brain functions
Cognition: transformation and elaboration of sensory input
Cognitive ethology: scientific study of animal intelligence
Cohort: a group of organisms of the same species, and usually of the same population, that are born at about the same time fecundity: the number of offspring produced by an individual
Collagen: a fibrous protein very plentiful in bone, cartilage, and other connective tissue
Colostrum: the precursor to milk that is formed in the mammary gland during pregnancy and immediately after birth of the young
Comparative anatomy: the branch of natural science dealing with the structural organization of living things
Connective tissue: any fibrous tissue that connects or supports body organs
Controlling site: a sequence of nucleotides generally fifteen to sixty nucleotides long, to which a transcriptional activator or repressor binds
Convection: a transfer of heat from one substance to another with which it is in contact
Corona radiata: the layers of follicle cells that still surround the mammalian egg after ovulation
Cortex: thin layer of gray matter that covers surfaces of the cerebrum and cerebellum
Countercurrent exchanger: the process where a medium (air or water) flowing in one direction over a tissue surface encounters blood flowing through the tissue in the opposite direction; this improves the gas diffusion by maintaining a concentration gradient
cuticle: the outermost layer of a hair, made of scales
Cytoplasm: the living portion of the cell that is contained within the cell membrane deoxyribonucleic acid (DNA): the molecular structure within the chromosomes that carries genetic information
Darwinism: branching evolution brought about by natural selection essentialism (typology): the Platonic- Aristotelian belief that each species is characterized by an unchanging “essence” incapable of evolutionary change
Deme: a local population of closely related living organisms
Deoxyribonucleic acid (DNA): the carrier of all an organism’s genetic information
Dermis: layer beneath the epidermis, primarily connective tissue but also containing nerves and blood vessels
Developmental anatomy: the study of the anatomical changes an animal undergoes in the process of growth
Developmental disorders: diseases caused by embryonic or fetal mistakes in normal development
Diastole: relaxation (filling with blood) of the heart chambers
Differentiation: the process during development by which cells obtain their unique structure and function
Diffusion: the process by which gas molecules move from a higher to a lower concentration through a medium or across a permeable barrier; the rate at which gases cross a barrier is increased by the surface area, and gas concentration gradient is decreased by the thickness of the barrier; gas solubility determines the amount that crosses the barrier
Digestion: the process by which larger organic nutrients are broken down to smaller molecules in the lumen of the gut
Diploid: having two chromosomes of each type
Diseases of aging: loss of functions required for health due to age-related degeneration of tissues
Dopamine: neurotransmitter involved in movement and reward systems
Dryopithecines: extinct Miocene-Pliocene apes (sometimes including Proconsul, from Africa) found in Europe and Asia; their evolutionary significance is unclear
Ducts: the tubular structures that carry milk from the alveoli to the outside through the nipple or teat
Duodenum: the first part of the small intestine, where it joins the stomach
Echolocation: the ability of animals to locate objects at a distance by emitting sound waves which bounce off an object and then return to the animal for analysis
Ecology: the study of the interactions between animals and their environment
Ecosystem: a community of organisms in relation to each other and their physical environment
Ectoparasite: a parasite, such as a tick, that lives on the external surface of the host
Ectotherm: an animal that regulates its body temperature using external (environmental) sources of heat or means of cooling
Ediacarian (Ediacaran) fauna: a diverse assemblage of fossils of soft-bodied animals that represents the oldest record of multicellular animal life on the earth eukaryotic cell: a cell that has a nucleus with chromosomes and other complex internal structures; this is the type of cell which makes up all organisms except bacteria
Ejaculation: the process of expelling semen from the male body endocrine glands: glands that produce hormones and secrete them into the blood
Embryo: a young animal that is developing from a fertilized or activated ovum and that is contained within egg membranes or within the maternal body
Embryology: the study of the development of individual animals evolutionary
Endocannibalism: a form of human cannibalism in which members of a related group eat their own dead
Endometrium: an inner, thin layer of cells overlying the muscle layer of the uterus
Endotherm: an animal that regulates its body temperature using internal (physiological) sources of heat or means of cooling
Enterocytes: the cells that line the lumen of the small intestine
Enzyme: a protein that acts as a catalyst under appropriate physiological conditions to break down bonds of a large protein, fat, or carbohydrate
Epidermis: surface layer of epithelial cells invertebrate: animal without a backbone
Erection: the process of enlargement and stiffening of the penis because of increased blood volume within it
Esophagus: the part of the oral cavity (pharynx) that transfers morsels to the stomach; it is usually a long, muscular tube with no digestive function other than transport
Estrus cycle: hormonally controlled changes that make up the female reproductive cycle in most mammals; ovulation occurs during the estrus (heat) period
Ethology: the study of an animal’s behavior in its natural habitat
Euryhaline: the ability of an organism to tolerate wide ranges of salinity
Evolution: any cumulative change in the characteristics of organisms or populations over many generations
Exocannibalism: a form of human cannibalism in which unrelated humans are eaten
External genitals: the external reproductive parts of the female
Feedback: in endocrinology, this usually refers to one hormone controlling the secretion of another that stimulates the first, usually in the form of negative feedback, in which the second hormone inhibits the first
Female: an organism that produces the larger of two different types of gametes
Fertilization: the process by which the egg and sperm unite to form the zygote gametes: the haploid cells, ova and spermatozoa, that fuse to form the diploid zygote
Fetus: a mammalian embryo from the stage of its development where its main adult features can be recognized, until birth maternal: referring to the female parent
Field observations: observing behavior in naturalistic settings
Fitness: the relative ability of individuals to pass on genes to subsequent generations
Fossil: a remnant, impression, or trace of an animal or plant of a past geologic age that has been preserved in the earth’s crust
Fovea: area, often a pit in the retina, of maximal acuity, where each photoreceptor has its own nerve cell, as opposed to many receptors converging on one nerve cell
Function: Ability, capacity, performance
Gamete: a functional reproductive cell (egg or sperm) produced by the adult male or female
Ganglia: clustered cell bodies of neurons that may form a brain-like center in lower animals
Gaploid: having one chromosome of each type
Gastrula: the stage of development during which the endoderm (gut precursor) and the mesoderm (muscle and connective tissue precursor) are internalized
Gastrulation: the transformation of a blastula into a three-layered embryo, the gastrula; initiated by invagination germ layers: the embryonic layers of cells which develop in the gastrula: ectoderm, mesoderm, and endoderm
Gene flow: the movement of genes from one population to another
Gene pool: the whole body of genes in an interbreeding population that includes each gene at a certain frequency in relation to other genes
Gene: a section of the DNA of a chromosome, which contains the instructions that control some characteristic of an organism
Generalized: not specifically adapted to any given environment; used to describe one group of Neanderthal humans
Genetic diseases: disorders caused by lack of enzymes or structural proteins caused by mutations
Genetic drift: change in gene frequencies in a population owing to chance
Genital area: it is destined to become the penis tip or clitoris
Genital tubercle: a small swelling or protuberance toward the front of an embryo’s
Genitalia: the external sex structures
Genome: all of the genetic material of an organism
Genotype frequency: the relative abundance of a genotype in a population
Genotype: the actual genetic makeup of an organism
Genus: the first part of the scientific name of an organism; members of the same genus but different species are closely related, but cannot mate and produce fertile offspring
Geoffroyism: an early theory of evolution in which heritable change was thought to be directly induced by the environment
Gestation: the term of pregnancy hormone: a substance produced by one organ of a multicellular organism and carried to another organ by the blood, which helps the second organ to function
Gill: an evaginated organ structure where the membrane wall turns out and forms an elevated, protruding structure; typically used for water respiration
Gland: a tissue composed of similar cells that produce a hormone
Gonad: the organ responsible for production of gametes—the testis in the male, the ovary in the female
Gonadotropin: a hormone that stimulates the gonads to produce gametes and to secrete other hormones
Gonochorism: sexual reproduction in which each individual is either male or female, but never both
Gopulation: the individuals of a species that live in one place and are able to interbreed
Gracile: slender and light-framed, as opposed to robust
Gray matter: region of the brain or spinal cord that contains cell bodies of neurons, where information processing and storage occur
Growth: the increased body mass of an organism that results primarily from an increase in the number of body cells and secondarily from the increase in the size of individual cells
Haploid: having one of each chromosome; a normal state for animal gametes
Heat: that part of the estral cycle when the female is receptive to male copulatory behavior
Heliotherm: an animal that uses heat from the sun to regulate its body temperature homeostasis: the maintenance by an animal of a constant internal environment
Heritability: the extent to which variation in some trait among individuals in a population is a result of genetic differences
Hermaphrodite: a single organism that produces both eggs and sperm
Hermaphroditism: sexual reproduction in which both male and female reproductive organs are present in the same individual, either at the same time or at different times
Homeotherm: an animal that strives to maintain a constant body temperature independent of that of its environment
Hominid: an anthropoid primate of the family Hominidae, including the genera Homo and Australopithecus
Hormone: a blood-borne chemical messenger receptor: a protein molecule on or in a cell that responds to the hormone by binding to it and initiating a series of events that compose the response
Humans: hominids of the genus Homo, whether Homo sapiens sapiens (to which all varieties of modern man belong), earlier forms of Homo sapiens, or such presumably related types as Homo erectus and the still earlier (and more problematic) Homo habilis
Humoral immunity: production of antibodies specifically reactive against foreign antigens carried in body fluids (humors)
Hypertonic: describes a solution with a higher osmotic pressure, one containing more osmotically active particles relative to the same volume, than the solution to which it is being compared
Hyperventilation: an increase in the flow of air or water past the site of gas exchange (lung, gill, or skin)
Hypotonic: a solution with a lower osmotic pressure, fewer osmotically active particles relative to the same volume, than the solution to which it is being compared
Hypoxia: from two Latin words, hypo and oxia, meaning “low oxygen”
Immune system: system that produces antibodies and cells that attack foreign substances and pathogens that invade the body
Insight learning: using past experiences to adapt and to solve new problems
Interbreeding: the mating of closely related individuals, which tends to increase the appearance of recessive genes
Intestine: the part of the digestive system involved in completing the process of digestion and absorption of nutrients; usually divided into the small intestine and the large intestine, which opens to the exterior by way of the anus
Invagination: the turning of an external layer into the interior of the same structure; formation of archenteron
Invertebrates: animals lacking a backbone phylogeny: the evolutionary history of a group of species
Isogamy: reproduction in which all gametes are equal in size and motility male: an organism that produces the smaller of two different types of gametes
Isotonic: a solution having the same osmotic pressure, the same number of osmotically active particles relative to the same volume, as the solution to which it is being compared
keratin: a tough fibrous protein, seen in large quantities in epidermal structures such as hair
Labial folds: the paired ridges of tissue on either side of the embryo’s genital area, which become penis and scrotum in males and labia in females
Lactation: the process of producing and delivering milk to the young; also, the time period during which milk is produced
Lamarckism: an early evolutionary theory in which voluntary use or disuse of organs was thought to be capable of producing heritable changes scale of being (chain of being): an arrangement of life forms in a single linear sequence from “lower” to “higher”
Larva: a newly hatched form of an organism that looks very different from adults of the species and must undergo metamorphosis to the adult form
Lexigrams: symbols associated with objects or places in keyboard communication experiments with primates
Life cycle: the sequence of development beginning with a certain event in an organism’s life (such as the fertilization of a gamete), and ending with the same event in the next generation
Life expectancy: the probable length of life remaining to an organism based upon the average life span of the population to which it belongs
Life span: Length of life from birth to death
Life table: a chart that summarizes the survivorship and reproduction of a cohort throughout its life span
Limbic system: brain structures related to the regulation of emotions
Lipid: an organic molecule, such as a fat or oil, composed of carbon, hydrogen, oxygen, and sometimes phosphorus, that is nonpolar and insoluble in water
Longevity: Length of life
Lumen: the central opening through the digestive tract, which is continuous from the mouth to the anus
Lung: an invaginated organ structure where the membrane wall turns in and forms a pouch or saclike structure
Lymphatic vessels: very thin tubes that carry water, proteins, and fats from the gut to the bloodstream
Lymphocyte: white blood cell that produces either cell-mediated or humoral immunity in response to foreign antigens
Macrophage: mature phagocytic cell that works with lymphocytes in destroying foreign antigens
Mammary glands: the milk-producing glands found in all mammals; for example, the cow’s udder contains the mammary glands
Mate Competition: competition among members of one sex for mating opportunities with members of the opposite sex
medulla: the innermost layer of a hair
Meiosis: reduction division of the genetic material in the nucleus to the haploid condition; it is the process used by animal cells to form the gametes
Menstrual cycle: a series of regularly occurring changes in the uterine lining of a non-pregnant primate female that prepares the lining for pregnancy
Metabolism: the biochemical action by which energy is stored and used in the body to maintain life
Metabolism: the sum of all of the reactions that take place in an animal allowing it to move, grow, and carry out body functions
Metamorphosis: the form changes in a larva that turn it into the adult form motile: able to move about spontaneously oviparous: born from an externally incubated egg
Migration: the movement of individuals, resulting in gene flow, changing the proportions of genotypes in a population
Migration: the movement of individuals, resulting in gene flow, changing the proportions of genotypes in a population
Milk ejection: also known as milk letdown, this is the reflex response of the mammary gland to suckling of the nipple; the hormone oxytocin mediates this reflex
Mineral: one of the many inorganic elements other than carbon, hydrogen, oxygen, and nitrogen that an organism requires for proper body function
Mitochondria: subcellular structures containing DNA used to estimate the relationships between groups of organisms; the more similar the DNA, the more closely related the groups
Mitosis: the process of cellular division in which the nuclear material, including the genes, is distributed equally to two identical daughter cells
Mitotic cells: cells capable of dividing and forming new cells
Morphology: the scientific study of body shape, form, and composition
Morphology: the study of structure; includes gross morphology, which examines entire structures or systems, such as muscles or bones; histology, which examines body tissues; and cytology, which focuses on cells and their components
Mortality rate: the number of organisms in a population that die during a given time interval
Mortality rate: the percentage of a population dying in a year
Morula: a solid ball or mass of cells resulting from early cleavage divisions of the zygote
Mouth: the anterior part of the digestive system, used for ingesting food; it leads into the oral cavity, which opens into the esophagus
Mucosa: the lining of the inner wall of the gut facing the lumen
Mucus: a secretion of the salivary glands and other parts of the digestive system which lubricates passages
Müllerian ducts: the embryonic ducts that will become the female oviducts or Fallopian tubes, uterus, and vagina parthenogenesis: the development of an unfertilized egg
Multicellular organisms: organisms consisting of more than one cell; there are diverse types of cells, specialized for different functions and generally organized into tissues and organs
Mutation: a change in the nucleotide sequence of a gene or of a controlling site; changes in genes alter the protein, whereas changes in controlling sites determine where and how much of a protein is produced
Myocarditus: inflammation of the heart muscle
Myoepithelial cells: the specialized cells within the mammary gland that surround the alveoli and contract to force milk into the ducts during milk ejection
Natality rate: the number of individuals that are born into a population during a given time interval
National Institutes of Health: the United States’ governmental division that monitors and improves public health
Natural selection: any environmental force that promotes reproduction of particular members of the population that carry certain genes at the expense of other members
Neurulation: the process by which the embryo develops a central nervous system notochord: a fibrous rod in an embryo which gives support; a structure that will later be surrounded by vertebrae zygote: the fertilized egg; the first cell of a new organism
Nipple: the raised area on the surface of the skin over the mammary gland that contains the duct openings
Olfaction: the sense of smell
Olfactory receptors: receptor organs which have very high sensitivity and specificity and which are “distance” chemical receptors
Ommatidium: individual unit of the multifaceted compound eye
Oogenesis: gamete formation in the female; it occurs in the female gonads, or ovaries
Opsin: a membrane-bound protein or pigment, which absorbs light
Optic nerve: the main nerve taking information from the eyes to higher processing areas
Optimum Temperature: the narrow temperature range within which the metabolic activity of an animal is most efficient
Organelle: a subcellular structure found within the cytoplasm that has a specialized function
Osmoconformer: an organism whose internal osmotic pressure approximates the osmotic pressure of its environment; such an organism is also referred to as “poikilosmotic”
Osmoregulator: an organism that maintains its internal osmotic pressure despite changes in environmental osmotic pressure; such an organism is also referred to as “euryosmotic”
Osteoblast: a bone cell which makes collagen and causes calcium deposition
Ovary: the female gonad, which produces ova and the hormones estrogen and progesterone
Ovum (pl. ova): the female reproductive cell (gamete); a mature egg cell
Oxytocin: hormone involved with pleasure during bonding
Pacemaker: a specialized group of cardiac muscle cells in the right atrium which initiates the heartbeat; also called the sinoatrial node
Pancreas: an organ derived from the gut that secretes digestive enzymes; it is connected to the gut by a duct through which its secretions enter the gut
Parasites: protozoans, fungi, or animals that survive by obtaining nourishment from a living host, from inside the host or on its surface
Parthenogenesis: a form of asexual reproduction where the young are derived from diploid or triploid eggs produced by the mother without any genetic input from a male
Periosteum: the fibrous membrane which covers all bones except at points of articulation, containing blood vessels and many connections to muscles
Persistent organic pollutants (POPs): chemicals that remain in the environment for a very long time and can be found at long distances from where they are used or released; they are nearly all of human origin
Phenotype: the observable characteristics of an organism (for example, black fur color in a cat)
Pheromone: a hormone produced by an animal and then released into the environment
Pheromones: species-specific compounds (odors) which, acting as chemical stimuli at a distance, have a profound effect on an animal’s behavior
Photon: a unit used to describe light intensity
Photoreceptor: cell containing membranes which house light-sensitive pigments
Phylogenetics: the study of the developmental history of groups of animals
Phylum: the taxonomic category of animals and animal-like protists that is contained within a kingdom and consists of related classes
Physiology: the study of the functions, activities, and processes of living organisms
Pinnipeds: flipper-footed marine mammals, such as sea lions, fur seals, true seals, walruses
Pleistocene epoch: the sixth of the geologic epochs of the Cenozoic era; it began about three million years ago and ended about ten thousand years ago
Plexus: a group of nerve cells and their connections to one another
Poikilotherm: an animal that does not regulate its body temperature, which will be the same as that of its environment
Population: a group of individuals of the same species that live in the same location at the same time; a group of individuals that occupy a common area and share a common gene pool
Precambrian eon: the earliest chapter of the earth’s history, covering the time interval between the formation of the earth, about 4.6 billion years ago, and the beginning of the Cambrian period, about 570 million years ago
Predation: broadly defined, any interaction in which one organism consumes another living organism, including herbivory (predation on plants), parasitism (predation by small organisms), and familiar predation (where one animal kills and eats another animal)
Predator: an organism that kills and eats another organism, generally of a different species
Primary emotions: emotions related to innate motivations
Primates: a group of mammals including apes, chimpanzees, monkeys, humans, lemurs, and tarsiers
Prions: infectious proteins that cause neurological diseases such as “mad cow disease” viruses: noncellular infectious agents that must enter a host cell to infect it
Prokaryotic cell: a primitive cell that lacks a nucleus, chromosomes, and other well defined internal cellular structures
Protein: a substance made up of amino acids; proteins are the chief building blocks of cellular structures
Protogrammar: word coined to signify the early foundation for grammar development found in primates
Random mating: the assumption that any two individuals in a population are equally likely to mate, independent of the genotype of either individual
Recapitulation: stages of human development reappearing in different animal species
Reproduction: reproduction in which genes are not exchanged
Reproductive Success: the number of offspring produced by one individual relative to other individuals in the same population
Respiratory pigment: a protein that “supercharges” the body fluid (blood) with oxygen; the oxygen can bind to the pigment and then be released
Respiratory surface: the gill, lung, or skin site at which oxygen is taken up from the air or water into the animal, with the release of carbon dioxide at the same time and site
Retina: the light-sensitive film at the back of the eye
Retina: the light-sensitive membrane at the back of the eye
Secondary emotions: emotions with a strong social component
Secondary metabolite: a biochemical that is not involved in basic metabolism, often of unique chemical structure and capable of serving a defensive role for the organism
Semen: fluid produced by the male reproductive system that contains the sperm
Septum: the bony structure that divides the nose into two sections
Sequester: to store a material derived from elsewhere. In defenses, some predators sequester defensive properties from their prey to defend themselves from their own predators
Sexual dimorphism: an observable difference between males and females in morphology, physiology, and behavior
Sexual reproduction: reproduction in which genes are exchanged between individuals
Sexual selection: selection for reproductive success brought about by the behavioral responses of the opposite sex
shaft: the main hair part, made of dead cells arranged in a complex fashion
Sirenians: plant-eating dugongs and manatees
Speciation: the formation of new species as a result of geographic, physiological, anatomical, or behavioral factors
Species: a category of biological classification ranking immediately below the genus or subgenus, comprising related organisms or populations capable of interbreeding
Species: a group of animals capable of interbreeding under normal natural conditions; the smallest major taxonomic category
Spermatogenesis: gamete formation in the male; it occurs in the male gonads, or testes
Spermatogenesis: the structural and functional changes of a spermatid that lead to the formation of a mature sperm cell
Sphincter: a ring of muscle that can close off a portion of the gut
Stenohaline: the inability of an organism to tolerate wide ranges of salinity
Stomach: the part of the digestive system where mechanical breakdown of food is completed and chemical digestion begins
Stratigraphy: in geology, a sequence of sedimentary or volcanic layers, or the study of them—indispensable for dating specimens
Subspecies: the third part of a scientific trinomial, assigned to one of two groups that can mate and produce fertile offspring, but that have some strikingly different characteristics
Survivorship: the pattern of survival exhibited by a cohort throughout its life span
Symbiosis: “living together”; a term that describes the association between two species in which one species typically lives in or on the other species. Parasitism is a common type of symbiosis
Systematics: the delineation and description of animal species and their arrangement into a classification
Systemic: referring to a group of organs that function in a coordinated and controlled manner to accomplish some end, such as respiration
Systole: contraction (emptying of blood) of the heart chambers
Target: cells that contain hormone receptors
Taxon (pl. taxa): group of related organisms at one of several levels such as the family Canidae, the genus Canis, or the species Canis lupus
Taxonomy: the classification of organisms in an ordered system that indicates natural relationships
Teat: an elongated form of nipple that contains one duct opening
Thermogenesis: the generation of heat in endotherms by shivering or increased oxidation of fats
Triploid: having three of each chromosome; an abnormal state which is unable to produce normal haploid gametes
Turbinates: bony structures that define the internal nasal anatomy
Uniformitarianism: a geological theory explaining the earth’s history using processes that can be seen at work today
Urogenital groove: a slitlike opening behind the genital tubercle that will become enclosed in the penis but remain open in females
Uterus: in female mammals, the organ in which the embryo develops
Valves: specialized, thickened groups of muscle cells in the heart chambers, major arterial trunks, arterioles, and veins which prevent backflow of blood
Ventilation: the movement, often by pumping, of air or water to the site of gas exchange; commonly thought of as breathing
Vertebrate: animal with a backbone made up of individual bones called vertebrae
Vitamin: an organic nutrient that an organism requires in very small amounts and which generally functions as a coenzyme
Vitelline envelope: the protective layers that form around the egg while it is still in the ovary
Viviparous: born alive after internal gestation zygote: a fertilized egg
Viviparous: producing young that are active upon birth (often referred to as live birth); the embryo is nurtured within the uterus
White matter: region of neural tissue that contains axons of neurons that carry electrical nerve impulses from one processing center to another
Wolffian ducts: an embryonic duct system that becomes the internal accessory male structures that carry the sperm
Würm glaciation: the fourth and last European glacial period, extending from about seventy-five thousand years ago to twenty-five thousand years ago
Xenotransplantation: the transplantation of organs from one species to another
Zona pellucida: mammalian protective layer analogous to the vitelline envelope
Zoogeography: the study of the distribution of animals over the earth
Zoology: the study of the mechanisms of evolutionary change and the evolutionary history of animal groups
Zygote: the single cell formed when gametes from the parents (ova and sperm) unite, a one-celled embryo