Chapter 46 Animal Reproduction Flashcards
What is a hermaphrodite?
Organism that can function as both a male and female.
What are the 2 major forms of reproduction?
- sexual reproduction
- asexual reproduction
What is sexual reproduction?
Creation of an offspring by fusion of a male gamete (sperm) and female gamete (egg) to form a zygote
What is asexual reproduction?
Creation of offspring without the fusion of egg and sperm
What are 4 examples of asexual reproduction?
- Binary fission
- Budding
- Fragmentation
- Pathogenesis
What is fission?
Separation of a parent into two or more individuals of about the same size
What is budding?
When a small bud grows out of the parent, but the parent doesn’t split into two.
- Bud eventually separates
What is fragmentation?
Breaking of the body into pieces where some of all of which develop into adults
- Initial parent splits into more than two pieces
What is parthenogenesis?
The development of a new individual from an unfertilized egg
What must be accompanied by fragmentation?
Regeneration: Regrowth of lost body parts
What is the “twofold cost” of sexual reproduction?
Sexual females have half as many daughters as asexual females
Which form of reproduction is expected to be most advantageous in stable, favorable environments, asexual or sexual reproduction?
Asexual reproduction
What are reproductive cycles controlled by?
- Hormones and environmental cues
What is ovulation?
Release of mature eggs at the midpoint of a female cycle
What can decrease reproductive success?
Climate change
How do several genera of fishes, amphibians, and lizards reproduce?
Via a complex form of parthenogenesis
What is hermaphroditism?
Individual has male and female reproductive system
What can hermaphrodites do? (2)
- Two can mate with each other
- Some can self-fertilize
What is fertilization?
Union of egg and sperm, play an important part in sexual reproduction
What happens in the external fertilization.
eggs shed by the female are fertilized by sperm in the external environment
What is required for external fertilization?
A moist habitat is required for the sperm to swim to the egg, and prevents gametes from drying out
What is spawning?
Clustering of individuals in the same area to release their gametes into the water at the same time.
What triggers spawning?
Sometimes it’s chemical signals, other times it is environmental cues
What happens in internal fertilization?
Sperm are deposited in or near the female reproductive tract, and fertilization occurs within the tract
What does internal fertilization require?
- Behavioral interactions
- Compatible copulatory organs
What does all fertilization all require?
- critical timing, often mediated by environmental cues, pheromones, and/or courtship behavior
What is internal fertilization associated with? (2)
- Production of fewer gametes, but higher amount of zygotes survive
- Mechanisms to provide protection of embryos and parental care of young
What are gonads?
Organs that produce gametes (testes and ovaries)
What are some types of embryos?
- Internal embryos
- Embryos that have eggs with calcium and protein containing shells/several internal membranes
What is a spermatheca?
A structure where sperm is stored during copulation of female insects
What is a cloaca?
Common opening b/w the external environment and the digestive, excretory, and reproductive systems
Where is cloaca most commonly found?
In nonmammalian vertebrates
What does reproductive organs do?
Produce and transport gametes
What are the male’s external reproductive organs? (2)
- Scrotum
- Penis
What are the male’s internal reproductive organs? (3)
- Gonads –> produce sperm and hormones
- Accessory glands that secrete products for sperm movement
- Ducts –> Carry sperm and glandular secretions
Why do the testes drop from the abdomen?
B/c sperm needs to produce in a less heated area;
Abdomen area has too high of a body temperature
What are testes?
Male gonads that consist of highly coiled seminiferous tubules surrounded by connective tissue
What happens in the seminiferous tubules?
Sperm is formed here
What does leydig cells produce?
Produce hormones and are scattered b/w the tubules
Where are the leydig cells located?
In the interstitial fluid outside of the seminiferous tubules
What is the scrotum?
Location of where testes are held b/c temperature is lower compared to the abdominal cavity
What happens in the epididymis?
Sperm is passed to here from the seminiferous tubules of the testes
What happens during ejaculation?
- sperm are propelled through the muscular vas deferens and the ejaculatory duct,
- then exit the penis through the urethra
What is semen composed of?
composed of sperm plus secretions from three sets of accessory glands
What does the two seminal vesicles do?
Contribute to about 60% of the total volume of semen
Where does the prostate gland secrete their products?
Secretes it directly into the urethra through several small ducts
What does the bulbourethral glands secrete?
A clear mucus before ejaculation that neutralizes acidic urine remaining in the urethra
What is the penis composed of?
Composed of 3 cylinders of spongy erecticle tissue
What happens during sexual arousal?
The erectile tissue fills with blood from the arteries, causing an erection
What does the head of the penis or glan consist of?
Consists of thinner skin covering than the shaft and is more sensitive to stimulation
What is the prepuce or foreskin?
A fold of skin that surrounds the glans
What does the female external reproductive structures consist of?
- Clitoris
- Two sets of labia
What does the internal organs of the female reproductive anatomy?
- Pair of gonads
- System of ducts and chambers that carries embryos and house embryos and fetus
What are the female gonads?
Ovaires that lie in the abdominal cavity
What does the ovaries contain? (2)
- Follicles
- Oocyte: partially developed egg
How does the egg cell travel from the ovary to the uterus?
Via an oviduct or fallopian tube
What is another name of the uterus lining?
Endometrium
What is another name for the uterus?
Womb
What does the uterus do? (2)
Narrows at the cervix
Opens into the vagina
What is the vagina?
Muscular but elastic chamber that is the repository for sperm during copulation and serves as the birth canal
What is the outside of the vagina? (5)
- Vulva
- Labia majora
- labia minora
- hymen
- clitoris
What are the mammary glands?
Glands that consist of small sacs of epithelial tissues that secretes milk
What is gametogenesis?
Production of gametes
What is spermatogenesis?
Formation of sperm
How long does it take for sperm to develop?
about 7 weeks
What is oogenesis?
Development of a mature egg
What are the 3 ways that spermatogenesis differs from oogenesis?
- All four products of meiosis develop into sperm while only one of the four becomes an egg
- Spermatogenesis occurs throughout adolescence and adulthood
- Sperm are produced continuously without the prolonged interruptions in oogenesis
What does the Gonadotropin-releasing hormone (GnRH) do?
Secreted by the hypothalamus, it stimulates the release of FSH and LH from the anterior pituitary gland
What does FSH and LH regulate?
Regulate processes in the gonads and the production of sex hormones
What is the main androgen?
Testosterone
What does estrogen consist of? (2)
Estradiol and progesterone
What does FSH promote in males?
Promotes activity of Sertoli cells which nourish developing sperm
What does LH regulate in males?
regulates Leydig cells –> which secrete testosterone and other androgens –> promote spermatogenesis
What does testosterone regulate?
the production of GnRH, FSH, and LH through negative feedback mechanisms
What does the Sertoli cells secrete?
Secrete the hormone inhibin, which reduces FSH secretion from the anterior pituitary
What is menstruation?
Process in which the endometrium is shedded if an embryo isn’t implanted in the endometrium
What happens prior to ovulation?
Endometrium thickens w/ blood vessels in preparation for embryo implantation
What is the uterine cycle?
Changes in the uterus that defines the menstrual cycle
What is the ovarian cycle?
Changes in the ovaries
What happens in the ovarian cycle? (4)
- GnRH is released which stimulates FSH and LH –> further stimulates follicle growth
- Follicle grows and there’s an increase in the hormone estradiol.
- Estradiol growth characterizes the follicular phase of the ovarian cycle
- Follicular phase ends at ovulation, and secondary oocyte is released
What are the 3 phases of the ovarian cycle?
- follicular phase
- ovulation
- luteal phase
What happens in the luteal phase? (2)
- Follicular tissue that is left behind is stimulated into a corpus luteum
- The corpus luteum secretes progesterone and estradiol that exerts a negative feedback on the hypothalamus and pituitary
What are the 3 phases of the uterine cycle?
- Menstrual flow phase
- proliferative phase
- ## secretory phase
What happens in the uterine cycle? (3)
- Thickening of the endometrium during the proliferative phase coordinates with the follicular phase
- Secretion of nutrients during the secretory phase coordinates with the luteal phase
- Shedding of the endometrium during the menstrual flow phase coordinates with the growth of new ovarian follicles
What is an ectopic location?
An abnormal location of where cells of the uterine lining can sometimes migrate to
What is endometriosis?
Swelling of these cells of uterine lining in response to hormone stimulation
What is menopause?
Cessation of ovulation and menstruation
What are estrous cycles? (3)
- The endometrium is reabsorbed by the uterus
- Sexual receptivity is limited to a “heat” period called estrus
- The length and frequency of estrous cycles vary from species to species
What is cleavage?
Process by which the resulting zygote begins to divide by mitosis
What is conception?
Fertilization of an egg by a sperm
What is a blastocyst>
A ball of cells with a central cavity
What does the division of cells give rise to?
Gives rise to blastocysts
What are the 4 phases of the sexual response cycle?
- excitement
- plateau
- orgasm
- resolution
What is vasocongestion?
Filling of tissue with blood
What is myotonia?
Increased muscle tension
What are the steps of a human zygote? (5)
- ovulation
- fertilization
- cleavage
- cleavage continues
- implantation
What is pregnancy or gestation?
Condition of carrying one or more embryos in the uterus
What happens in the first trimester? (4)
- First 2-4 weeks, embryo obtains nutrients from endometrium
- Placenta is formed
- Development of body organs
- Embryo develops into a fetus
What is the trophoblast?
Outer layer of the blastocyst and eventually forms the placenta
What is organogenesis?
Development of body organs
What is a fetus
A developed embryo with all the major structures
What are some changes in the mother? (5)
- Mucus plug to protect against infection
- Growth of the placenta and uterus
- Cessation of ovulation and the menstrual cycle
- Breast enlargement
- Nausea is also very common
What happens during the second trimester? (3)
- The fetus grows and is very active
- The mother may feel fetal movements
- The uterus grows enough for the pregnancy to become obvious
What happens during the 3rd trimester? (2)
- Fetus grows and fill the space with embryonic membranes
- Childbirth happens with push of both the fetus and placenta
What are the 3 stages of labor?
- Thinning and opening of the cervix, or dilation
- Expulsion or delivery of the baby
- Delivery of the placenta
What is contraception?
Deliberate prevention of pregnancy
What are the 3 methods of contraception?
- Preventing release of eggs and sperm
- Keeping sperm and egg apart
- Preventing implantation of an embryo
What is the rhythm method or natural family planning?
Refraining from intercourse when conception is most likely; pregnancy rate of 10-20%
What is coitus interruptus?
Withdrawal of the penis before ejaculation
What is the barrier method?
Covering of the genitals before intercourse
What is a vasectomy?
Sterilization that ties off the vas deferens
What is tubal ligation?
Sterilization that ties off the oviducts of females
What happens during In vitro fertilization (IVF)?
Mixes eggs with sperm in culture dishes and returns the embryo to the uterus at the eight-cell stage
What are two invasive techniques that obtain amniotic fluid or fetal cells for genetic analysis?
- Amniocentesis
- Chorionic villus
What are two female contraceptions for birth control?
- Intrauterine devices (IUDs)
- Birth control pills
