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49 Cards in this Set
- Front
- Back
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Sexual reproduction
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Creation of an offspring by fusion of a male gamete (sperm) and female gamete (egg) to form a zygote
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Asexual reproduction
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Creation of offspring without the fusion of egg and sperm
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Fission
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Separation of parent into two or more individuals of about the same size
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Budding
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New individuals arise from outgrowths of existing ones
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Parthenogenesis
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The development of a new individual from an unfertilized egg
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Fragmentation
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Breaking of the body into pieces, some or all of which develop into adults, must be accompanied by regeneration
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Regeneration
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Regrowth of lost body parts
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Hermaphroditism
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Each individual has male and female reproductive systems
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Follicle
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Housed in each ovary, consists of a partially developed egg surrounded by support cells
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Oocyte
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Partially developed egg surrounded by support cells
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Oviduct
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Fallopian tube, carries the egg from the ovary to the uterus
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Uterus
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Womb
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Endometrium
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The uterus lining containing many blood vessels
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What is meant by the “twofold cost” of sexual reproduction?
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Sexual females have half as many daughters as asexual females
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What are the possible advantages of sexual reproduction compared to asexual reproduction?
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1. Increase in variation of offspring, providing an increase in reproductive success for parents in changing environments
2. Increase in the rate of adaption 3. Shuffling of genes and the elimination of harmful genes from a population |
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What are the similarities and differences between internal and external fertilization?
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Internal fertilization: Sperm are deposited in or near female reproductive tract, and fertilization occurs within the tract. Requires compatible organs
External fertilization: Eggs shed by the female are fertilized by sperm in external environment Both: Require critical timing, mediated by environmental cues, pheromones, and courtship behavior |
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What are the external and internal organs of the female reproductive system?
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External organs: Clitoris (shaft, glans, prepuce) and two sets of labia (minora and majora)
Internal organs: Pair of gonads (ovaries) and system of ducts and chambers (follicles, corpus luteum, oviduct, uterus, cervix, vagina) |
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What happens during ovulation? What happens to the remaining follicular tissue?
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An egg is expelled from the follicle. The remaining follicular tissue grows and forms a mass called a corpus luteum which secretes hormones to help maintain pregnancy. This mass degenerates if the egg is not fertilized.
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What are the external and internal organs of the male reproductive system?
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External organs: Scrotum and penis
Internal organs: Gonads (testes) and accessory glands (two seminal vesicles, prostate gland, bulbourethral gland) |
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Why are the testes of many mammals held outside the abdominal cavity?
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Abdominal cavity temperature is too high for the production of normal sperm.
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What is the sequence of structures through which a sperm cell passes after leaving the seminiferous tubules?
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1. Exit from seminiferous tubules of a testis
2. Travel through tubules of epididymis Ejaculation 1. Sperm travel through vas deferens and ejaculatory duct 2. Exit penis through urethra |
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What is semen composed of?
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Sperm plus secretions from the two seminal vesicles (contribute 60% of volume of sperm, coagulant), prostate gland (secretes anticoagulant), and bulbourethral glands (secrete a clear mucus before ejaculation that neutralizes acidic urine within the urethra).
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What substances comprise the secretions of the seminal vesicles? prostate gland, bulbourethral glad?
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Seminal vesicles: Mucus, sugar fructose (energy for sperm), coagulating enzyme, ascorbic acid, prostaglandins
Prostate gland: Anticoagulant enzymes and citrate (sperm nutrient) Bulbourethral gland: Secrete a clear mucus which neutralizes any acidic urine remaining in the urethra |
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What is meant by the term gametogenesis and how does it differ between males and females?
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Gametogenesis: Production of gametes by meiosis
Spermatogenesis: Form of gametogenesis in males, sperm -Four sperm produced from each cycle of meiosis -Continues throughout life -Continuous sequence Oogenesis: Form of gametogenesis in females, eggs -One egg forms from each cycle of meiosis -Ceases later in life -Long interruptions |
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What are the steps involved in spermatogenesis?
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1. Primordial germ cell in embryo undergoes mitotic divisions-forms haploid spermatogonial stem
2. Spermatogonial stem cell undergoes mitotic divisions-forms spermatogonium 3. Spermatogonium undergoes mitotic divisions-forms primary spermatocyte 4. Primary spermatocyte undergoes meiosis I-forms 2 secondary spermatocytes 5. Secondary spermatocytes undergo meiosis II-each forms 2 early spermatids (4 total) 6. Spermatids undergo differentiation (Sertoli cells provide nutrients)-forms mature sperm cells |
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What is the acrosome and what is its function?
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Acrosome: Tip of head of sperm, secretes enzymes that digest part of the egg membrane to allow for fertilization
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What are the steps involved in oogenesis?
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1. Primordial germ cell undergoes mitotic divisions- forms oogonium
2. Oogonium undergoes mitotic divisions- forms primary oocyte (present at birth, arrested in prophase of meiosis I) 3. Primary oocyte undergoes completion of meiosis I and onset of meiosis II- forms secondary oocyte (arrested at metaphase of meiosis II) 4.Secondary oocyte, after ovulation and sperm entry, undergoes completion of meiosis II-forms fertilized egg |
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Development of the primary oocyte is arrested at which stage of development?
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Prophase of meiosis I
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What stimulates a primary oocyte to resume growth?
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A small group resumes growth at puberty. One follicle fully matures each month. Second meiotic division begins but stops at metaphase.
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Development of the secondary oocyte is arrested at which stage of development?
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Metaphase of meiosis II
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Under what conditions does the secondary oocyte complete meiosis?
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After ovulation and if a sperm penetrates the oocyte
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What are three key differences between spermatogenesis and oogenesis?
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Spermatogenesis: Form of gametogenesis in males, sperm
-Four sperm produced from each cycle of meiosis -Continues throughout life -Continuous sequence Oogenesis: Form of gametogenesis in females, eggs -One egg forms from each cycle of meiosis -Ceases later in life -Long interruptions |
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What is gonadotropin-releasing hormone (GnRH)?
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Gonadotropin releasing hormone (GnRH): Secreted by the hypothalamus, directs the release of FSH and LH from the anterior pituitary
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What is the function of FSH and LH?
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Follicle stimulating hormone (FSH) and luteinizing hormone (LH) regulate processes in the gonads and the production of sex hormones.
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What are the sex hormones and what do they regulate?
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Androgens, estrogens, and progesterone regulate:
1. The development of primary sex characteristics during embryogenesis 2. The development of secondary sex characteristics at puberty 3. Sexual behavior and sex drive |
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In response to LH what do Leydig cells secrete?
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Testosterone
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What is the function of inhibin?
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Inhibin (secreted by sertoli cells) reduces FSH secretion from the anterior pituitary, negative feedback
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What is the function of the negative feedback circuit in the hormonal control of the male reproductive system?
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Maintain androgen production at optimal levels, which promotes spermatogenesis.
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What are the two cycles of female reproduction?
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Ovarian cycle: Release of GnRH, then FSH and LH, which stimulates follicle growth and leads to ovulation, the release of the secondary oocyte
Uterine (menstrual) cycle: Thickening of the endometrium, secretion of nutrients, and shedding of the endometrium, so that a new cycle may begin if no embryo implants in the endometrium |
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What is the role of FSH and LH in the ovarian cycle?
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Stimulate follicle growth
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What is the stimulus for the rupture of the ovary and release of the secondary oocyte (ovulation)?
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A peak in LH levels
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What is the source of estradiol in the ovarian cycle?
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Growing follicle, corpus luteum
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What is the effect of estradiol on the hypothalamus and anterior pituitary? (hint: Be sure to take into account the different estradiol concentrations occurring during the ovarian cycle.)
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Hypothalamus: Stimulated by stradiol to output GnRH. Inhibited by estradiol with progesterone.
Anterior pituitary: Inhibited by low levels of estradiol |
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What hormone or combination of hormones are responsible for transforming the ruptured follicle into the corpus luteum? degeneration of the corpus luteum?
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LH stimulates the ruptured follicle to form the corpus luteum which secretes progesterone and estradiol, while low gonadotropin levels cause the corpus luteum to disintegrate.
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What is the relationship between the levels of progesterone and estradiol produced by the corpus luteum and the secretion of LH and FSH by the anterior pituitary?
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LH stimulates the growth of the follicle, which produces progesterone and estradiol. The progesterone and estradiol rise, exerting negative feedback on the hypothalamus and anterior pituitary, which reduce the secretion of LH and FSH to very low levels.
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What happens during the proliferative phase of the uterine cycle?
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The endometrium is stimulated by estradiol to thicken in preparation for an embryo.
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The level of which hormone coordinates the follicular phase of the ovarian cycle with the proliferative phase of the uterine cycle?
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As estradiol increases, the follicle continues to grow and the hormone signal for the endometrium to become thicker.
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What effect does disintegration of the corpus luteum have on the endometrium of the uterus?
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The disintegration of the corpus luteum causes a sharp decrease in ovarian hormone levels, which causes arteries in the endometrium to constrict and leads to the shedding of the endometrium.
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What happens if the egg is not fertilized and an embryo does not implant?
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If an embryo is not implanted in the endometrium by the end of the secretory phase (secretion of nutrients for an embryo), then a new menstrual flow commences and the next cycle starts.
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