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Chapter 43
Animal Reproduction
| Question | Answer |
|---|---|
| What happens in sexual reproduction? | two haploid cells form a diploid individual |
| What is gametogenesis? | a process that produces haploid gametes through meiotic cell division |
| what two events in meiosis contribute to genetic diversity? | crossing over between homologous chromosomes and the independent assortment of chromosomes |
| What are the three fundamental steps of sexual reproduction? | 1. Gametogenesis: making gametes 2. Mating: geting gametes together 3. Fertilization: fusing gametes |
| Where does gametogenesis occur in both males and females? | The gonads. In males the gonads are testes and the gametes are motile sperm. In females the gonads are the ovaries and the gametes are non-motile ova, or eggs |
| What is spermatogenesis? | The process that involves two meiotic divisons to produce four haploid spermatids. Through further development, the spermatids becoem compact, streamlined, and motile |
| Describe the embryo stage of oogenesis | The female germ cells divide by mitosis to eventually form primary oocytes. A primary oocyte immediately begins prophase I of meiosis - development stops in many species and primary oocyte grows larger & acquires nutrients |
| Describe the adult stage of oogenesis | When meiosis resumes, the primary oocyte divides into two daughter cells of unequal sizes. 1. Secondary oocyte - cell with more cytoplasm 2. first polar body - smaller |
| The secondary oocyte divides through meiosis. What does it produce? | A large, haploid cell (ootid) that becomes the mature ovum and a second polar body, which degenerates |
| Describe the process of fertilization | the union of a haploid sperm and a haploid egg. It creates a singl diploid cell, called a zygote, which will develop into an embryo |
| What are the steps in fertilization | recognition of sperm and egg, activation of sperm, plasma membranes fuse, additional sperm entry blocked, activation of egg, egg and sperm nuclei fuse |
| What are the functions of the cumulus and zona in mammalian egg cells? | The cumulus is a thick layer surrounding the mammalian egg, and the zona is a glycoprotein envelop beneath the cumulus |
| What occurs when mammalian sperm are deposited in the female reproductive tract? | a species-specific glycoprotein in the zona binds to the head of the sperm, triggering a reaction and releasing enzymes that digest a path through the zona |
| Explain blocks to polyspermy | if more than one sperm enters the egg, the resulting embryo is unlikely to survive. In mammals sperm entry causes calcium influx and cortical ganules fuse with the egg plasma membrane. Enzymes destroy the sperm- binding molecules in the zona pellucida |
| What is external fertilization? | a process that occurs in an aquatic envir when gametes are released into the water. Repro behaviors to ensure fertilization include the release of gametes synchronized by day length, temperature, or weather, and congregating with potential mates |
| What is internal fertilization? | A process that occurs when sperm is released directly into the female reproductive tract. Gonads are the primary sex organs. |
| What are accessory sex organs? | the penis, and vagina, and copulation is the joining of the male and female accessory organs |
| What are diecious species? | Species that have seperate male and female members |
| What are monoecious, or hermaphroditic species? | A single individual may produce sperm and eggs. |
| What is the difference between a simultaneous hermaphrodite and a sequential hermaphrodite? | Simultaneous hermaphrodite can function as a male or female at the same time while a sequential hermaphrodite may funcion as a male or a female at different times |
| Describe reptile and bird reproduction | reptiles and birds evolved an amniote egg to overcome a dry environment. An egg contains food and water and the hard shell reduces water loss. Sperm must reach the egg before the shell forms, requiring internal fertilization and accessory sex organs |
| What are oviparous animals? | animals that lay eggs in the environment and embryos develop outside the mother's body |
| What are viviparous animals? | animals that are live-bearing, retain the embryo in the mother's body during early development |
| What is the difference between the uterus and the placenta? | the uterus, or womb holds the embryo, while the placenta develops in the uterus and enables exchange of nutrients and waste |
| Where does spermatogenesis occur within each testis? | in the seminiferous tubules. |
| What cells produce testosterone? | Leydig cells |
| The epithelial lining of the tubules contains what? | spermatongonia |
| What are Sertoli cells? | cells which provide nutrients for developing sperm, that are closely associated with germ cells in stages of spermatogenesis |
| Where are sperm stored? | In the epididymis, where they mature and become motile |
| How are the urethra and vas deferens related? | The urethra is the common duct for the reproductive and urinary systems - connected to the epididymis by the vas deferens |
| Explain semen | contains mucus, protein, fructose. Secreted mostly by the seminal vesicles (empty into the vas deferens), prostate gland surrounds the urethra and contributes alkaline fluid to semen to reduce acidity in male and female reproductive tracts |
| What are the two steps in which semen is expelled through the vas deferentia and urethra? | 1. Emission: rhythmic contractions move the semen into the urethra at the base of the penis. 2. Ejaculation: contractions by muscles at the base of the penis that force the semen out |
| What is the oviduct? | The fallopian tube - the area where the ovary releases an egg where it can be fertilized |
| What is the structure of the opening of the vagina and urethra in humans? | Humans have two sets of skin folds called the labia minora and majora. At the tip of the labia is the clitoris, erectile tissue that is important in sexual response |
| What is a blastocyst? | After fertilization, a diploid zygote undergoes cell division and becomes a blastocyst which moves down the oviduct and attaches to the lining of the uterus (endometrium) |
| What is implantation? | Implantation occurs when the blastocyst burrows into the endometrium |
| What are the two linked female reproductive cycles ? | The ovarian cycle that produces eggs and hormones, and the uterine cycle that prepares the endometrium for a blastocyst. If a blastocyst does not arrive, the thickened endometrium sloughs off |
| Describe the ovarian cycle | in a human female, the ovarian cycle is ~28 days long but it varies. |
| What happens during the first half of the cycle? | Ovulation. Primary oocycte is nourished by ovarian cells as it matures into an egg (follicle). After about 14 days, follicle ruptures and egg is released |
| What happens during the second half of the cycle? | Ovarian cells develop endocrine functions that stop if the egg is not fertilized |
| On average, how many ovarian cycles will a woman go through in life? | about 450 ovarian cycles |
| What is menopause? | The end of fertility, there may be only a few oocytes left in each ovary |
| What is the corpus luteum? | Formed after ovulation when follicular cells continue to proliferate. It remains in the ovary and functions as an endocrine gland and produces estrogen and progesterone for ~2 weeks. It degenerates unless a blastocyst implants in the endometrium |
| Describe the uterine cycle | parallels the ovarian cycle. Consists of the buildup and breakdown of the endometrium. The endometrium remains prepared for a blastocyst until about 9 days after ovulation |
| What is menstruation? | The sloughing off of the endometrium through the vagina. Most other mammals do not menstruate; the uterine lining is reabsorbed |
| What hormone is secreted after fertilization and implantation, and what purpose does it serve? | human chorionic gonadatropin (hCG)...basis for pregnancy testing. Effects of hCG are the corpus luteum continues to produce estrogen and progesterone, and the endometrium is maintained so menstruation does not occur. |
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cassidylm34
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