Animal Reproduction Lecture Notes

Flashcards reviewing animal reproduction, reproductive anatomy, and physiology.

Reproduction Types

Asexual: an individual produces new, genetically identical organisms through mitosis; Sexual: gametes from two individuals unite to form a new organism that is genetically different from the parents.

Asexual Reproduction Forms

Binary fission in unicellular organisms, budding, fragmentation, and parthenogenesis.

Fission

Division of a cell that produces two identical daughter cells.

Gemmation/Budding

Production of mini individuals or buds over the individual, seen in sponges and anemones.

Fragmentation

Division of the body into parts, each fragment can regenerate the remaining parts, seen in flatworms and annelids.

Parthenogenesis

Development of individuals from non-fertilized eggs, seen in nematodes, wasps, and some reptiles and fish.

Totipotency

Preserves a unique genotype.

Advantage of Asexual Reproduction

Increases population size rapidly; offspring are clones that respond uniformly to environmental changes.

Sexual Reproduction

Requires specialized sexual organs (gonads) to produce gametes via meiosis; energetically costly.

Advantage of Sexual Reproduction

Increases genetic variability, leading to greater responses to environmental changes.

Life Cycle - Sexual

Animals exhibit alternation of diploid and haploid stages; gametes unite to form a diploid zygote that divides by mitosis to develop into a multicellular diploid organism.

Dioecious

Individuals have separate male and female sexes with respective gonads.

Monoecious/Hermaphrodites

A single individual possesses both male and female sexual organs.

Fertilization

Union of male and female gametes to form a new organism (zygote).

External Fertilization

Occurs outside the body, requiring a moist environment to prevent desiccation.

Internal Fertilization

Occurs inside the female reproductive tract.

Male Gonads

Testes; produce spermatozoa via spermatogenesis in the seminiferous tubules and testosterone in Leydig cells.

Spermatogenesis

Cannot occur at body temperature; testes are located outside of the abdominal cavity in the scrotum.

Epididymis

Site for maturation and storage of spermatozoa until ejaculation.

Semen

Spermatozoa and secretions from three accessory glands.

Seminal Vesicles

Secrete a fluid rich in fructose and prostaglandins.

Prostate Gland

Secretes an alkaline fluid that neutralizes the acidity in the vagina.

Bulbourethral Glands

Neutralizes the acidity in the male urethra and lubricates the passage of spermatozoa.

Penis

Male copulatory organ consisting of the glans, prepuce, and trunk.

Process by which spermatozoa travel from the epididymis to the exterior.

Ejaculation

Female External Structures

The external structure of the female reproductive system comprised of the vulva, hymen, clitoris, labia majora and minora, and the opening to the vagina.

Female Internal Organs

Ovaries, fallopian tubes (oviducts), uterus, and vagina.

Ovaries

Female gonads that produce eggs (ova) via oogenesis.

Oogenesis

Site of egg production, hormones such as estradiol and progesterone are created here.

Uterus

Muscular chamber where the embryo develops; the inner surface is covered by a highly vascularized endometrium.

Insemination

The introduction of sperm into the female tract.

Vagina

Site where the baby passes throughout birth.

Clitoris

Erectile organ, similar to the penis, containing nerves that produce sexual pleasure.

Endometriosis

A condition of endometrial tissue development outside of the Uterus.

Gametogenesis

Production of gametes by meiosis; differs between males and females.

Spermatogenesis

Production of spermatozoa. If semen contains less than 20 million spermatozoa/mL, the male is considered sterile.

Spermatozoa

Small and motile; produced continuously from puberty onwards; contributes mostly DNA to the zygote; can survive in the female tract for up to 5 days.

Oogenesis at Birth

At birth, each ovary contains approximately 1 million ovarian follicles, each formed by an oocyte.

Oogenesis after Puberty

At sexual maturity, an oocyte can develop into and is released as an ovum via oogenesis; remains in metaphase II and does not finalize meiosis.

Differnces between Oogenesis and spermatogenesis

One functional ovum is produced per meiosis. Spermatogenesis forms four spermatozoa. Production of sperm is continuous, whereas oogenesis includes long interruptions and halts to occur at menopause

Reproductive Cycles

Related to seasons of the year.

Hormones Under Control of Hypothalamus-Pituitary-Gonad Axis

GnRH (hypothalamus), FSH and LH (anterior pituitary), estradiol, progesterone, and testosterone (gonads).

Tropic Hormones

Regulate function of tissues or endocrine glands.

Reproduction

Regulated by luteinizing hormone (LH) and follicle-stimulating hormone (FSH).

Role of LH in Males

Stimulates testes to produce testosterone; testosterone and FSH stimulate spermatogenesis in testes.

Inhibin

Secreted by Sertoli cells to inhibit FSH secretion in the pituitary.

Role of LH and FSH in Females

Stimulate ovaries to produce estrogen and progesterone.

Estrogen Role

Regulates oogenesis and development of secondary sexual characteristics.

Progesterone Role

Prepares the reproductive tract to receive and nourish the zygote.

Pituitary Produces Non-Tropic Hormones

Prolactin (PRL).

Oocyte Development

Develops into Ovary Cycle

Endometrium

Develops into Menstrual Cycle

Contraception Methods

Inhibition of uterine lining development, egg implantation, fertilization, and other systems of reproduction.