Chapter 26 Reproduction and Development

Reproduction:

The creation of new individuals from existing ones.

Asexual Reproduction:

Reproduction without sex, producing genetically identical offspring.

Budding:

Formation of a new individual from an outgrowth of the parent.

Fission:

Separation of a parent into two or more offspring of about equal size.

Fragmentation:

Breaking of the body into pieces followed by regeneration.

Genetic Diversity:

Variation in genetic material important for survival in changing environments.

Sexual Reproduction:

Fusion of haploid gametes (sperm and egg) resulting in a zygote with genetic variability.

Gametes:

Haploid sex cells (sperm and egg).

Zygote:

The diploid cell formed by fusion of sperm and egg.

External Fertilization:

Release of eggs and sperm into the environment, common in aquatic animals.

Internal Fertilization:

Sperm deposited inside female’s body, common in terrestrial animals.

Testes:

Male gonads producing sperm and testosterone.

Epididymis:

Stores and matures sperm.

Vas Deferens:

Transports sperm during ejaculation.

Urethra:

Passage for sperm and urine.

Penis:

Organ for copulation and ejaculation.

Accessory Glands:

Seminal vesicles, prostate, and bulbourethral glands that produce semen fluids.

Scrotum:

Holds testes and regulates temperature.

Vasectomy:

Surgical removal of vas deferens to prevent sperm release.

Ovaries:

Produce eggs and hormones.

Fallopian Tubes:

Site of fertilization and egg transport.

Uterus:

Site of implantation and fetal development.

Cervix:

Gateway between uterus and vagina, dilates during childbirth.

Vagina:

Birth canal and sperm entry site.

Follicles:

Cells surrounding and nourishing eggs in ovaries.

Ovulation:

Release of a mature egg from the ovary.

Tubal Ligation:

Female sterilization by severing fallopian tubes.

Ectopic Pregnancy:

Implantation of embryo outside uterus, usually fallopian tube.

Gametogenesis:

The formation of haploid gametes by meiosis.

Spermatogenesis:

Formation of sperm in seminiferous tubules of testes.

Oogenesis:

Development of egg cells; primary oocytes pause in meiosis until ovulation.

Ovarian Cycle:

Follicle development, ovulation, and corpus luteum formation.

Menstrual Cycle:

Monthly buildup and shedding of the uterine lining (endometrium) if fertilization does not occur.

Hormones involved:

Follicle Stimulating Hormone (FSH), estrogen, progesterone, human chorionic gonadotropin (HCG).

HCG (human chorionic gonadotropin)

Maintains corpus luteum during early pregnancy.

Fertilization:

Union of sperm and egg to form a zygote; occurs in fallopian tubes with enzymes in sperm acrosome aiding egg penetration.

Zygote:

Single cell formed by fusion of nuclei within 24 hours of fertilization.

Cleavage:

Rapid mitotic divisions producing blastocyst.

Blastocyst:

Hollow fluid-filled ball with inner cell mass that forms the fetus.

Gastrulation:

Formation of three embryonic layers.

Organogenesis:

Formation of organs from embryonic layers.

Apoptosis:

Programmed cell death important in development (e.g., separation of fingers).

Gestation:

Pregnancy duration, about 280 days or 40 weeks.

Trimesters:

Three stages of fetal development (first, second, third trimester).

Placenta:

Organ that facilitates nutrient and waste exchange between fetus and parent.

First Trimester:

Organ formation and early body structures.

Second Trimester:

Rapid growth, maturation, fetal movements, development of hair, nails, senses.

Third Trimester:

Final growth, organ maturation, fat accumulation, immune development, fetal positioning for birth.

Childbirth (Labor) stages:

Dilation of cervix, expulsion of baby, delivery of placenta.

Hormones:

Progesterone and estrogen decrease to allow uterine recovery; prolactin promotes milk production.

Lactation:

First colostrum then mature milk secretion by mammary glands.

In Vitro Fertilization (IVF):

Assisted reproductive technology where eggs are fertilized outside the body and viable embryos are implanted into the uterus.