DAT: CH 12 Reproduction & Developmental Biology

Asexual Reproduction

Process by which one organism produces genetically identical offspring without gametes or fertilization.

Binary Fission

DNA replicates and a septum forms to divide the cell into two identical daughter cells (e.g., prokaryotes, mitochondria).

Budding

small bud forms on the parent, receives a copy of DNA, and detaches as a new organism (e.g., yeast, hydra).

Regeneration

Fragment of an organism grows into a new one or regenerates missing parts (e.g., planaria, hydra).

Parthenogenesis

Unfertilized egg develops into a viable organism; common in bees (haplodiploidy: males haploid, females diploid)

Spermatogenesis

Formation of haploid sperm cells (spermatozoa) from diploid germ cells (spermatogonia) via meiosis.

Spermiogenesis

Final stage of spermatogenesis where spermatids mature into spermatozoa.

Sperm Structure

Head (nucleus + acrosome), midpiece (mitochondria for ATP), tail (flagellum for motility).

Seminal Vesicles

Produce fructose (energy), prostaglandins (urethral contractions), and mucus (lubrication).

Prostate Gland

Secretes alkaline fluid to neutralize uterine acidity.

Bulbourethral (Cowper’s) Glands

Produce viscous mucus that lubricates and cleans the urethra.

FSH (Follicle-Stimulating Hormone)

Stimulates sperm production in seminiferous tubules by activating Sertoli cells.

Sertoli Cells

Nourish developing sperm and secrete inhibin for negative feedback on FSH.

LH (Luteinizing Hormone)

Stimulates Leydig cells to produce testosterone.

Leydig Cells

Produce testosterone for sperm maturation and male secondary sex traits.

Testosterone

Hormone responsible for sperm development and male secondary characteristics.

Oogenesis

Production of a haploid ovum (egg) from diploid oogonia via meiosis with unequal cytoplasmic divisions.

Ovary

Produces ova (eggs) and female hormones.

Fimbriae

Finger-like projections that receive released eggs from the ovary.

Oviduct (Fallopian Tube)

Transports eggs from ovary to uterus; site of fertilization.

Uterus

Muscular organ with three layers — perimetrium (outer), myometrium (muscular), endometrium (inner epithelial) — supports embryo implantation.

Cervix

Narrow passage between uterus and vagina.

Vagina

Muscular canal leading to the outside of the body; site of sperm entry and birth canal.

Follicle

Fluid-filled sac in ovary containing an immature oocyte (arrested in prophase I); later forms corpus luteum.

Corpus Luteum

Structure formed after ovulation that secretes progesterone and estrogen to maintain the endometrium

FSH (Female)

Stimulates follicle growth and estrogen production.

LH (Female)

Triggers ovulation and corpus luteum formation.

Estrogen

Thickens endometrium and develops female secondary sex traits.

Progesterone

Maintains the endometrium and supports pregnancy.

GnRH (Gonadotropin-Releasing Hormone)

Released by hypothalamus to stimulate FSH and LH release from pituitary.

Positive Feedback

Enhances a biological process (e.g., oxytocin during childbirth, prolactin during lactation).

Positive Feedback

inhibits biological pathways (e.g., estrogen and progesterone suppress FSH/LH).

Negative Feedback

Inhibits biological pathways (e.g., estrogen and progesterone suppress FSH/LH).

Follicular Phase

FSH stimulates follicle growth and estrogen production; endometrium thickens.

Ovulation

LH surge releases mature egg from Graafian follicle.

Luteal Phase

Corpus luteum secretes estrogen and progesterone to maintain the endometrium.

hCG (Human Chorionic Gonadotropin)

Hormone from placenta that maintains corpus luteum and endometrial lining during early pregnancy.

Fertilization

Fusion of haploid sperm and egg to form a diploid zygote

Capacitation

Final sperm maturation in the female reproductive tract; increases calcium permeability for hyperactivity.

Acrosomal Reaction

Sperm releases enzymes to penetrate zona pellucida (ZP3 protein) and fuse with egg membrane.

Polyspermy Block

Prevents multiple sperm from fertilizing one egg

Fast Block

Membrane depolarization preventing other sperm entry.

Slow Block

Cortical reaction forming fertilization envelope via calcium release.

Completion of Meiosis II

Triggered in the oocyte after sperm entry, forming mature ovum and polar bodies.

Monozygotic Twins

Identical twins formed from a single fertilized egg that splits.

Dizygotic Twins

Fraternal twins formed from two separate fertilized eggs

Cleavage

Rapid mitotic divisions of the zygote without overall growth, forming blastomeres.

Blastomeres

Smaller cells produced during cleavage.

Axis of Cleavage

Direction of cell division; spiral (protostomes) or radial (deuterostomes).

Regulative (Indeterminate) Cleavage

Cells can form complete embryos (deuterostomes)

Mosaic (Determinate) Cleavage

Cells have predetermined fates (protostomes).

Morula

Solid ball of blastomeres

Blastula

Hollow sphere with fluid-filled center (blastocoel).

Blastocyst

Differentiated blastula that implants into uterine wall.

Gastrulation

Formation of three germ layers: ectoderm, mesoderm, and endoderm.

Blastopore

Opening that forms during gastrulation; becomes mouth (protostomes) or anus (deuterostomes).

Archenteron

Primitive gut formed during gastrulation.

Ectoderm

Forms nervous system, sensory organs, skin, hair, nails, enamel, mammary/sweat glands, and adrenal medulla.

Mesoderm

Forms bones, muscles, cardiovascular system, gonads, spleen, notochord, and adrenal cortex.

Endoderm

Forms epithelial lining of digestive, respiratory, and excretory tracts; and organs like pancreas, liver, thyroid, parathyroid, and thymus.

Stem Cells

Undifferentiated cells capable of differentiating into specific cell types based on potency.

Neurulation

Formation of the nervous system; notochord induces ectoderm to form neural plate → neural tube (CNS).

Notochord

Mesodermal structure that signals ectodermal differentiation; forms basis of spinal column

Neural Crest Cells

Migrate to form teeth, facial cartilage, and pigmentation cells.

Somites

Mesodermal cells that form vertebrae and skeletal muscles.

Amnion

Innermost membrane secreting amniotic fluid to cushion embryo; found in reptiles, birds, and mammals (amniotes)

Chorion

Outermost layer; forms fetal side of placenta in mammals, or gas exchange surface in egg-layers.

Allantois

Sac for waste storage and gas exchange; forms umbilical cord and bladder in mammals

Yolk Sac

Provides early nutrients and first site of blood cell formation before placenta develops.

Embryonic Induction

Process by which organizer cells influence development of nearby cells.

Homeotic Genes

Determine structure placement and body plan; include HOX genes for anterior-posterior axis

Homeobox

Conserved DNA sequence in homeotic genes across species

Egg Cytoplasm Determinant

Uneven yolk distribution (animal and vegetal poles) influences cleavage pattern and cell fate.

Apoptosis

Programmed cell death essential for normal development and tissue sculpting.

Temperature-Dependent Sex Determination

Environmental temperature determines sex in some reptiles (e.g., turtles, crocodiles)