BI206 - Final - Key Terms

Clone

an individual that carries an exact copy of the nuclear genome of another individual; clones are genetically identical cells or individuals

Asexual reproduction

the reproduction of organisms by mitotic cell division or fragmentation. Offspring are clones of the parent

Budding

a form of asexual reproduction in fungi, plants, and some animals in which a bud forms on the organism and eventually breaks off to form a new organism that is smaller than its parent

Fragmentation

a form of asexual reproduction in which new individuals arise by the splitting of one organism into pieces, each of which develops into a new individual

Parthenogenesis

a form of asexual reproduction in which females produce eggs that are not fertilized by males but divide by mitosis and develop into new individuals

Sexual reproduction

the process of producing offspring that receive genetic material from two parents; in eukaryotes, the process occurs through meiosis and fertilization

Meiotic cell division

a form of cell division that includes only one round of DNA replication but two rounds of nuclear division; meiotic cell division makes sexual reproduction possible

Fertilization

the union of gametes to produce a diploid zygote

Gamete

a reproductive haploid cell; gametes fuse in pairs to form a diploid zygote. In many species, there are two types of gametes

Spore

a reproductive cell capable of growing into a new individual without fusion with another cell

Spermatozoa

the smaller, male gametes

Sperm

the smaller, male gametes

Ova

the larger, female gamete, also called an egg

Egg

the larger, female gamete, also called an ovum

Zygote

the diploid cell formed by the fusion of two gametes

Embryo

an early stage of multicellular development that results from successive mitotic divisions of the zygote

Twofold cost of sex

the observation that population size can increase more rapidly in asexually reproducing organisms than in sexually reproducing organisms because only females produce offspring in sexually reproducing organisms

External fertilization

fertilization that takes place outside the body of the female; in some aquatic organisms, for example, eggs and sperm are released into the water

Internal fertilization

Fertilization that takes place inside the body of the female

r-strategists

a species that produces large numbers of offspring but provides few resources for their support

K-strategists

a species that produces relatively few young but invests considerable resources into their support

Yolk

a substance in the eggs of animals with external fertilization that provides all the nutrients that the developing embryo needs until it hatches

Amnion

in the amniotic egg, a membrane surrounding a fluid-filled cavity that allows the embryo to develop in a watery environment

Chorion

in the amniotic egg, a membrane that surrounds the entire embryo along with its yolk and allantoic sac

Extraembryonic membranes

in the amniotic egg, one of several sheets of cells that extend out from the developing embryo and form the yolk sac, amnion, allantois, and chorion

Ovoviviparity

giving birth to live young, with nutritional support of the embryo from the yolk

Viviparity

giving birth to live young, with nutritional support of the embryo from the mother

Placenta

in placental mammals, an organ formed by the fusion of the chorion and allantois that allows the embryo to obtain nutrients directly from the mother

Gonad

in mammals, the part of the reproductive system where haploid gametes are produced. Male gonads are testes, where sperm are produced. Female gonads are ovaries, where eggs are produced.

Testes

the male gonad, where sperm are produced

Acrosome

an organelle that surrounds the head of sperm containing enzymes that enable sperm to transverse the outer coating of the egg

Flagellum

an organelle that propels the movement of cells; short flagella are also called cilia

Scrotum

a sac outside the abdominal cavity of the male that holds the testes

Seminiferous tubule

a series of tubes in the testes where sperm are produced

Epididymis

an organ that lies above the testes where sperm become motile and are stored prior to ejaculation

Vas deferens

a long, muscular tube that carries sperm from the testes to the ejaculatory duct of amniote vertebrates

Ejaculatory duct

the duct through which sperm travel from the vas deferens to the urethra

Urethra

a tube from the mammalian urinary bladder that in males carries semen as well as urine from the body

Semen

a fluid that nourishes and sustains sperm as they travel in the male and then the female reproductive tracts

Seminal vesicle

two glands at the junction of the vas deferens and the prostate gland that secrete a protein- and sugar-rich fluid that makes up most of the semen and provides energy for sperm motility

Prostate gland

a vertebrate exocrine gland that produces a thing slightly alkaline fluid that helps maintain sperm motility and counteracts the acidity of the female reproductive tract

Bulbourethral gland

glands below the prostate gland that produce a clear fluid that lubricates the urethra for passage of the sperm

Penis

the male copulatory organ

Glans penis

the head of the human penis

Oocyte

an unfertilized egg cell in animals produced by the mother; a developing female gamete

Ovary

the female gonad where eggs are produced

Oviduct

a tube from each ovary, through one of which a release oocyte passes; also called fallopian tube

Fallopian tube

a tube from each ovary, through one of which a released oocyte passes; also called oviduct

Uterus

a hollow organ within the reproductive tract of female mammals with thick, muscular walls that is adapted to support the developing embryo if fertilization occurs and to deliver the baby during birth

Cervix

the end, or neck, of the uterus

Vagina

a tubular channel connecting the mammalian uterus to the exterior of the body; also known as the birth canal

Vulva

the external genitalia of the female

Labia majora

outer folds of skin in the vulva

Labia minora

inner folds of skin in the vulva that meet at the clitoris

Clitoris

the female homolog of the glans penis

Luteinizing hormone (LH)

a hormone secreted by the anterior pituitary gland of vertebrates that stimulates the gonads to secrete testosterone in males and estrogen and progesterone in females

Follicle-stimulating hormone (FSH)

a hormone secreted by the anterior pituitary gland that stimulates the male and female gonads to secrete testosterone in males and estrogen and progesterone in females

Testosterone

a steroid hormone, secreted by the vertebrate testes, that plays key roles in male growth, development, and reproduction

Estrogen

a hormone secreted by the ovaries that stimulates the development of female secondary sexual characteristics

Progesterone

a hormone secreted by the vertebrate ovaries that maintains the thickened and vascularized uterine lining

Leydig cells

a type of cell in the testes that secretes testosterone

Secondary sexual characteristics

a trait that characterizes and differentiates the two sexes but that does not relate directly to reproduction

Sertoli cell

a type of cell in the seminiferous tubules of vertebrate testes that supports sperm production

Menstrual cycle

a monthly cycle in females of some mammals in which oocytes mature and are released from the ovary under the influence of hormones

Follicular phase

the phase of the menstrual cycle during which FSH acts on granulosa cells, resulting in the maturation of several oocytes, of which, usually, only one becomes completely mature

Luteal phase

the phase of the menstrual cycle of mammals beginning with ovulation

Follicle

a type of cell that makes up the shell of cells surrounding an oocyte that supports the developing oocyte

Corpus luteum

a temporary endocrine structure in the ovaries that secretes progesterone

Human chorionic gonadotropin (hCG)

a hormone released by the developing embryo that maintains the corpus luteum

Menopause

the cessation of menstrual cycles resulting from decreased production of estradiol and progesterone by the mammalian ovaries

Estrus cycle

a cycle in placental mammals other than humans and chimpanzees characterized by phases in which females are sexually receptive

Gametogenesis

the formation of gametes

Spermatogenesis

the formation of sperm

Primary spermatocyte

a diploid cell formed by mitotic division of spermatogonia at the beginning of spermatogenesis

Secondary spermatocyte

a diploid cell formed during the first meiotic division of the primary spermatocyte

Oogenesis

the formation of ova or eggs

Secondary oocyte

a large cell produced by the asymmetric first meiotic division of the primary oocyte

Polar body

a small cell produced by the asymmetric first meiotic division of a primary oocyte

Capacitation

a series of physiological changes that allow the sperm to fertilize the egg

Polyspermy

in animals, fertilization by more than one sperm

In vitro fertilization (IVF)

a process in which eggs and sperm are brought together in a petri dish, where fertilization and early cell divisions occur

Cleavage

the successive mitotic divisions of the zygote after fertilization, in which the single large egg is divided into many smaller cells

Morula

in animals, the solid ball of cells resulting from early cell divisions of the fertilized egg

Blastula

a hollow ball of cells filled with fluid that develops from the morula and is an early stage during embryo development in animals

Pregnancy

the carrying of one or more embryos in the mammalian uterus
Trimester

Fetus

an embryo in mammals

Gastrulation

a highly coordinated set of cell movements in animals in which the cells of the blastula migrate inward, creating germ layers of cells within the embryo

Germ layer

three sheets of cells in animals—the ectoderm, mesoderm, and endoderm—formed by migrating cells of the gastrula that differentiate further into specialized cells and tissues

Ectoderm

in animals, the outer germ layer, which differentiates into epithelial cells, pigment cells in the skin, nerve cells in the brain, and in animals with eyes, the cornea and lens

Mesoderm

in animals, the intermediate germ layer, which differentiates into cells and make up connective tissue, muscle cells, red blood cells, bone cells, kidney cells, and gonad cells

Endoderm

in animals, the inner germ layer, which differentiates into cells of the lining of the digestive tract and associated organs

Organogenesis

the transformation of the three germ layers into all the organ systems of the body in animals

Pathogens

organisms and other agents, such as viruses, that cause disease

Self

describes an organism’s own molecules and cells

Nonself

from the point of view of a given organism, describes molecules and cells that are foreign

Autoimmune diseases

a disease in which tolerance is lost and the immune system becomes active against antigens of the host

Innate immunity

the part of the immune system that provides protection in a nonspecific manner against all kinds of infection; it does not depend on exposure to a pathogen

Adaptive immunity

the part of the vertebrate immune system that is specific to a given pathogen and that responds more strongly to subsequent infections

Cilia

hairlike structures that extend from the surface of cells. Nonmotile cilia don’t move and often have a sensory function; motile cilia propel the movement of cells or fluid surrounding the cell

White blood cells

a type of cell in the immune system that arises by differentiation from stem cells in the bone marrow