Flashcards in [Chapter 39] Reproduction Deck (172)
What is a zygote?
The first cell of a new individual formed by the fusion of one gamete from each parent.
Give a short description of the genetic basis of sexual reproduction.
Meiosis and the formation of gametes typically occur in two prospective parents. At fertilization, a gamete from one parent fuses with a gamete from the other and forms the first cell of the new individual—the zygote.
Give a short description of asexual reproduction.
A single organism produces its own offspring. In asexual reproduction, one parents has all its genes represented in its offspring.
Is sexual or asexual reproduction better for an environment that does not vary over time?
Asexual reproduction is better, as the gene combinations that allowed the parent to reproduce can be expected to do the same for their offspring.
Why is sexual reproduction good for environments that change over time?
Every individual inherits a different combination of parental genes, increasing the odds that some offspring will have a gene combination that suits the changing environment.
Why is sexual reproduction costly?
Only half of a parent's genes end up in the offspring; resources and energy must be allocated to forming gametes. Timing of gamete formation must be synchronized between partners, and there has to be a partner.
Why does sexual reproduction require timing?
Sperm in one individual must mature at the same time as eggs of another individual.
What is internal fertilization?
The union of sperm and egg within the female body.
What is yolk?
A thick fluid that contains proteins and lipids that nourishes the embryo until it can feed.
How are humans nourished in embryo?
Through a nearly yolk-less, fertilized egg and through physical changes in the mother's bloodstream.
True or False: Separation into male and female sexes requires special reproductive cells and structures, and neural and hormonal control mechanisms.
True. They also require "forms of behaviour", whatever the heck that means.
What are the six stages of animal reproduction and development?
1. Gamete Formation2. Fertilization3. Cleavage4. Gastrulation5. Organ Formation6. Growth, Tissue Specialization
Describe the stage Gamete Formation.
Eggs form and mature in female reproductive organs. Sperm form and mature in male reproductive organs.
Describe the stage Fertilization.
A sperm penetrates an egg. Their nuclei fuse, and a zygote is formed.
Describe the stage Cleavage.
Mitotic cell divisions form a ball of cells called a blastula. Each cell gets regionally different parts of the egg cytoplasm.
A ball of cells that enclose a cavity (blastocoel) filled with their own secretions.
Describe the stage Gastrulation.
Cells self-organize as an early embryo (a gastrula) that has two or three primary tissue layers, which make the germ layers of a new individual.
An early embryo.
What are Germ Layers?
The forerunners of the adult animals's tissues and organs.
What are the Germ Layers of the Gastrula?
The Ectoderm, Endoderm, and Mesoderm.
What is the Ectoderm?
The outer germ layer. It forms first, and gives rise to nervous tissue and to the outer layer of skin or other body covering.
What is the Endoderm?
The inner germ layer, it is the tart of the respiratory tract and gut linings.
What is the Mesoderm?
In most kinds of animals, the mesoderm forms between the ectoderm and the endoderm. This layer is the source of all muscles, connective tissues, and the circulatory system.
Describe the stage Organ Formation.
Details of the body plan fill in as different cell types interact and form tissues and organs in predictable patterns.
Describe the stage Growth, Tissue Specialization.
The final stage of animal development, the tissues and organs grow in size and slowly begin to take on their final sizes, shapes, proportions, and functions.
What does sperm consist of?
Parental DNA and a bit of equipment that helps in swim to and penetrate an egg.
What is an oocyte?
An immature egg that has far more cytoplasm compared to the sperm. The cytoplasm has yolk proteins that will nourish a new embryo, mRNA transcripts for proteins that will by translated in early development, tRNAs and ribosomes to translate the mRNA transcripts, and proteins required to build mitotic spindles.
What is cytoplasmic localization?
When certain components are not distributed all through the egg cytoplasm, they are localized in one particular region or another. It helps guide development.
What is cytoplasmic localization a feature in all of?
Oocytes (immature egg).
What does cytoplasmic localization give rise to?
It gives rise to the polarity that characterizes all animal eggs.
What pole has most of the yolk in a yolk-rich egg?
The vegetal pole has most of the yolk and the animal pole has little.
In amphibian eggs, at what pole is pigment most concentrated?
Close to the animal pole.
True or False: Cleavage puts different parts of the egg cytoplasm into the same blastomeres.
False, cleavage puts different parts of the egg cytoplasm into different blastomeres.
True or False: The amount of yolk influences the pattern of cleavage division.
True, large volumes of yolk can slow or block the cuts that lead to division while in nearly yolk-less eggs the cuts slice straight through.
At what stage do cells start to migrate around and rearrange themselves?
They start to move at gastrulation. A portion at the embryo's surface will move inward.
What initiates gastrulation?
Signals from the cell of the dorsal lip.
True or False: Cleavage divides a fertilized egg into a number of small cells, increasing the original volume.
False. The division into multiple cells does not increase the original volume.
Define Selective Gene Expression.
When different cell lineage express different subsets of genes.
Define Cell Differentiation.
The process by which cell lineage becomes specialized in composition, structure, and function.
About how many differentiated cell types does an adult human body have?
The complete genetic material of an organism.
Does a differentiated cell still retain the entire genome?
Yes, making it possible to make a genetic copy (a clone) of an adult animal from one of its differentiated cells.
What are Morphogens?
Molecular signals that are encoded by master genes.
What is Embryonic Induction?
When embryonic cells produce signals that alter the behaviour of neighbouring cells.
True or False: Intercellular signals can encourage differentiation.
True. Example: secretion of morphogens in embryonic cells.
The process by which the tissues and organs form.
What happens to the body during morphogenesis?
The body begins to take shape as cells migrate, with entire sheets of tissue folding and bending, and with specific cells dying on cue.
What three main steps occur during morphogenesis?
1. Cells migrate to specific locations.2. Sheets of cells expand and fold as cells change in shape. This is caused by the controlled assembly and disassembly of microtubules and microfilaments.3. Programmed cell death helps sculpt body parts.
What is the process Apoptosis?
The programmed cell death hat helps sculpt body parts. Signals from certain cells activate the tools of self-destruction in target cells.
What is Pattern Formation?
The process by which certain body parts form in a specific place.
What does the tissue Apical Ectodermal Ridge (AER) stimulate to develop?
AER stimulates the mesoderm to develop, but earlier positional cues have already determined what the mesoderm will become.
What are Homeotic Genes?
Genes that regulate development of specific body parts. All animals have similar homeotic genes.
What three constraints influence body plans?
1. Physical constraints (ex. surface-to-volume ratio)2. Architectural constraints (as imposed by the body axes)3. Phyletic (evolutionary) constraints
What imposes the constraints on the body plan?
The constraints are imposed by interactions among genes that regulate development in a lineage.
True or False: Mutations led to a variety of forms among animal lineages by creating new genetic trails.
False. Mutations led to a variation of animal forms by modifying existing developmental pathways.
Human gametes form in primary reproductive organs (gonads). What are theres in males and what do they produce and secrete?
There are a pair of gonads in males called testes that produce sperm and secrete the sex hormone testosterone.
The stage of development when reproductive organs mature.
What is the first pair of coiled ducts that immature sperm travels through?
The epididymis, where secretions from glands in the walls will trigger events that put the finishing touches on sperm cells. The last part of the epididymis stores mature sperm.
How much sperm is matured per day and where do the unused sperm go?
100 million sperm is matured everyday, and unused sperm is resorbed or passed in urine.
Where is mature sperm propelled in a sexually aroused male?
Into the Vasa Deferentia, a pair of thick-walled ducts. It continues into paired ejaculatory ducts and then into the urethra, through the penis and out at the tip.
What is Semen?
A thickened fluid that gets expelled from the penis during sexual activity, made by sperm mixing with glandular secretions while travelling to the urethra.
What does sperm use as an energy source?
Fructose, making most of semen a fructose-rich fluid.
What are prostaglandins?
Local signalling molecules that can increase the growth rate of cervical and uterine cancers that is secreted into semen.
What are the reproductive organs in males? (5)
1. Testes (2) - sperm, sex hormone production2. Epididymis (2) - sperm maturation site and subsequent storage3. Vas Deferens (2) - rapid transport of sperm4. Ejaculatory Ducts (2) - conduction of sperm to penis5. Penis - organ of sexual intercourse
What are the accessory glands in males? (3)
1. Seminal Vesicle (2) - secretion of large part of semen2. Prostate gland - secretion of part of semen3. Bulbourethral gland (2) - production of mucus that function in lubrication
What is the pH of vaginal fluid and at what pH does sperm swim most efficiently?
The pH of vaginal fluid is about 3.5-4.0. Sperm swims more efficiently at 6.0
Does prostate cancer have a genetic factor?
Yes, having a father of brother with prostate cancer doubles the risk.
What "increase of" do doctors look for in blood tests for prostate cancer?
They look for increases of prostate-specific antigen (PSA).
How long would uncoiled seminiferous tubules from the testis be?
It would be over 125 meters long.
What cells lie between spaces of the seminiferous tubules?
Testosterone-secreting Leydig cells cluster in the spaces.
What are Sertoli cells?
A cell inside the seminiferous tubule that provides metabolic support to spermatocytes.
What are male germ cells called?
What is a mature sperm?
A haploid, flagellated cell. The flagellum allows it to swim toward an egg.
What is in the "head" of a sperm?
DNA and an enzyme-filled cap, to help the sperm penetrate an oocyte.
How long does sperm formation take?
Sperm formation takes 100 days from start to finish.
What four hormones are part of the signalling pathways that control sperm formation?
Testosterone, Luteinizing Hormone (LH), Follicle-Stimulating Hormone (FSH), and gonadotropin-releasing hormone (GnRH).
Hormone Control: What does testosterone do?
It governs the structure and function of the male reproductive tract, induces the development of male secondary sexual traits, promotes sexual and aggressive behaviour.
What are the ovaries and what do they produce and secrete?
The ovaries are a pair of gonads that produce oocytes and secrete sex hormones on a cyclic basis.
Where does the oocyte fertilize?
In the oviduct.
What is the uterus?
A hallow, pear-shaped organ above the urinary bladder.
What is the vagina?
A muscular, mucosa-lined tube, extends from the cervix to the body's surface. Functions as the female organ of intercourse.
What are the Female Reproductive Organs? (5)
1. Ovaries (2) - oocyte production and maturation, sex hormone production 2. Oviducts (2) - tubes between the ovaries and the uterus; fertilization normally takes place here3. Uterus - chamber in which new individual develops4. Cervix - entrance to the uterus; secretes mucus that enhances sperm travel into uterus and reduces embryo's risk of infection5. Vagina - organ of sexual intercourse; birth canal
True or False: Humans females follow an estrous cycle
False, this means they are only fertile and sexually receptive to males at certain times. Females of most mammalian species follow this.
True or False: Human females follow a menstrual cycle
True, their fertile periods are cyclic, intermittent, and not ties to sexual receptivity. They can be responsive to sex at any time but will not always get pregnant.
What is Menopause?
The decline in secretion of sex hormones, the 'twilight' of a female's fertility.
What is PMS?
Premenstrual syndrome, discomfort (among other things) a week or two before a women menstruates due to aldosterone secretion.
What can cause menstrual pain?
Secretion of prostaglandins (stimulate contractions in the uterus wall).Endometriosis, the growth of endometrial tissue in the wrong places of the pelvis.Fibroids, benign uterine tumours.
What can prevent hot flashes during menopause?
Hormone replacement therapy, and living a healthy lifestyle can reduce symptoms.
Have many primary oocytes does a girl have at birth?
About 2 million.
What is the follicular phase of the menstrual cycle?
The menstrual flow lasts 1-5 days as the uterine lining breaks down. Over the next 6-13 days the uterine lining is slowly rebuilt as the oocyte begins to mature.
What happens during the ovulation phase of the menstrual cycle?
Around day 14, one ovary releases an oocyte.
What happens during the luteal phase of the menstrual cycle?
A glandular corpus luteum develops and its secretions cause the endometrium to thicken in preparation for pregnancy. This phase lasts for days 15-28.
What do Estrogens do?
They control how the female reproductive organs develop in embryos, and starting at puberty they control female secondary traits.
Estrogens and what else induce oocytes to mature and help prime the uterus for pregnancy?
What are Fraternal Twins?
Twins that form after two oocytes mature and are released during one menstrual cycle, and then get fertilized. They start as two genetically different zygotes and are no more alike than any other siblings.
What are Identical Twins?
Twins that form when one zygote or early embryo splits. This is a chance event.
What type of twins can run in families?
What hormone causes women to be more likely to have fraternal twins?
FSH, with the average women's FSH levels rising later in life (mid-thirties).
How much sperm can ejaculation put into the vagina?
It can put 150-350 million sperm, which can live for about 3 days after ejaculation.
What is a mature egg called?
Give a brief description of how someone becomes pregnant.
Sexual arousal involves nervous signals and hormones in both males and females. Ejaculation releases millions of sperm into the vagina. Uterine contractions help some of them reach the oviducts, where fertilization usually occurs. Fertilization is over when a sperm nucleus and egg nucleus fuse and form the diploid nucleus of a new individual.
How many eggs form during a woman's lifetime?
As many as 500.
What does Rhythm Methods mean (in the context of Fertility Control Options)?
A form of abstinence where a women avoids sex during her fertile period.
What is a Vasectomy?
Surgery where the doctor makes a small incision into the scrotum, and cuts and ties off each vas deferens. Does not lead to permanent infertility.
What is Tubal Ligation?
A surgery that blocks or cuts the oviducts, resulting in permanent infertility.
What is HPV?
Human papillomavirus. Can cause genital warts and/or cervical cancer. A vaccine can prevent infection if given before the first viral exposure.
What is Trichomoniasis?
Trichomonas vaginalis, a flagellated protist, causes trichomoniasis. Symptoms include vaginal soreness, itching, yellowish discharge. Males usually show no symptoms. Untreated, can damage the urinary tract, cause infertility, invite HIV. An antiprotozoal drug can cure an infection.
What is Chlamydia?
Chlamydia trachomatis causes the disease, antibiotics can kill it quickly. Females will show no symptoms, males can have abnormal discharges from the penis and painful urination. Untreated males will risk inflamed reproductive tract and infertility, male and females could develop PID.
What are Genital Herpes?
Caused by type 2 Herpes simplex virus, small blisters form and causes painful sores. Antiviral drugs can treat it.
What is Gonorrhea?
Caused by Neisseria gonorrhoeae, infected females could suffer painful urination, cramps, fever, vomiting, and scarring leading to infertility. Males have yellow pus discharge. Urination becomes painful. Antibiotics can cure this. There are 16 strains of this STD.
What is Syphilis?
A spirochete bacterium Treponema pallidum causes syphilis. Lesions and scars appear in the skin and liver, bones, and other organs. Chronic immune reactions may damage the brain and spinal cord, and cause paralysis.
What is Aids?
Infection by HIV, the human immunodeficiency virus, leads to AIDS (acquired immune deficiency syndrome). AIDS is presently incurable. The immune system weakens, which opens the door to opportunistic infectious agents.
How long does pregnancy last?
It lasts an average of 38 weeks starting from fertilization.
What is a blastocyte?
The type of blastula that forms in mammals, takes about one week to form.
In what period do all major organs form?
The embryonic period, during the second to eighth week of pregnancy.
What is the developing individual called after the embryonic period?
What happens in the fetal period?
From week nine onto birth, organs grow and become specialized. There are three trimesters: the first three months, months 4-6, and months 6-end of pregnancy.
Describe what happens during days 1-2 after fertilization.
The first cleavage furrow extends between the two polar bodies. Later cuts are angled, so cells become asymmetrically arranged. Until the eight-cell stage forms, they are loosely organized, with space between them.
Describe what happens during day 3 after fertilization.
After the third cleavage, cells abruptly huddle into a compacted ball, which tight junctions among the outer cells stabilize. Gap junctions formed along the interior cells enhance intercellular communication.
Describe what happens during day 4 after fertilization.
By 96 hours there is a ball of sixteen to thirty-two cells shaped like a mulberry. It is a morula (after morum, Latin for mulberry). Cells of the surface layer will function in implantation and will give rise to a membrane, the chorion.
Describe what happens during day 5 after fertilization.
A blastocoel (fluid-filled cavity) forms in the morula as a result of surface cell secretions. By the thirty-two-cell stage, differentiation is occurring in an inner cell mass that will give rise to the embryo proper. This embryonic stage is the blastocyst.
Describe what happens during days 6-7 after fertilization.
Some of the blastocyst’s surface cells attach themselves to the endometrium and start to burrow into it. Implantation has started.
What is implantation?
The blastocyte attaches to the uterine lining, and the burrows into the endometrium. The inner cell mass develops into two flattened layers of cells called the embryonic disk.
What is the Amnion?
A membrane that will enclose the embryo in a fluid-filled, buoyant cavity.
What is the Chorion?
A third membrane that lines amnion and yolk sac, becomes part of placenta.
What is the Yolk Sac?
Germ cell source, becomes site of red blood cell formation.
What is the Placenta?
An organ that functions in exchanges of materials between the bloodstreams of a mother and her developing child.
What is the Allantois?
The fourth extraembryonic membrane, source of urinary bladder and blood vessels for the placenta.
Describe what happens during days 10-11 after fertilization.
The yolk sac, embryonic disk, and amniotic cavity have started to form actual from parts of the blastocyst.
Describe what happens during day 12 after fertilization.
Blood-filled spaces form in maternal tissue. The chorionic actual cavity starts to form.
Describe what happens during day 14 after fertilization.
A connecting stalk has formed between the embryonic disk and chorion. Chorionic villi,which will be features of a size placenta, start to form.
What is the inner cell mass of a blastocyte two weeks after fertilization?
A two-layered embryonic disk.
What is the Ectoderm of the Human Germ Layers?
Outer layer (epidermis) of skin; nervous tissue.
What is the Mesoderm of the Human Germ Layers?
Middle layer, connective tissue of skin; skeletal, cardiac, smooth muscle; bone; cartilage; blood vessels; urinary system; gut organs; peritoneum (coelom lining); reproductive tract.
What is the Endoderm of the Human Germ Layers?
Inner layer, lining of gut and respiratory tract, and organs derived from these linings.
What is Spina Bifida?
A birth defect where the neural tube and one or more vertebrae do not form as they should. The spinal cord will protrude out of the vertebral column at birth.
What are somites?
Multiple paired segments that arise from the mesoderm during the end of the third week, the embryonic sources of most bones as well as the head and trunk's skeletal muscles and overlying dermis.
True or False: Vessels of the embryo’s circulatory system extend through the umbilical cord to the placenta, where they run through pools of maternal blood. Maternal and embryonic blooddo not mix; substances diffuse between the maternaland embryonic bloodstreams.
True, all exchange of materials between an embryo and its mother takes place by the placenta.
How big is the embryo after the fourth week?
500 times its starting size, but still less than a centimetre in length.
What happens in the second trimester?
Developing nerves and muscles connect up, reflexive movements begin. Legs kick, arms wave about, and fingers grasp. At five months old, its heartbeat can be heard clearly through a stethoscope positioned on the mother’s abdomen. Movements of fetal arms and legs can be sensed. Soft, fetal hair (the lanugo) covers the skin (most will be shed before birth). A thick, cheesy coating protects the wrinkled, reddish skin from abrasion. In the sixth month eyelids and eyelashes form.
What happens at the beginning of the third trimester?
Eyes open (seventh month), all the portions of the brain have formed and have begun to function.
What do B-complex vitamins do for the embryo?
Taken early in the pregnancy, it reduce's the embryos risk of neural tube defects.
Why should pregnant women eat well-cooked meat and avoid cat feces (Besides common sense)?
To minimize the risk of infectious diseases leading to developmental problems, miscarriages, or stillbirth.
What is Fetal Alcohol Syndrome (FAS)?
Alcohol intake during pregnancy that leads to small head and brain, facial abnormalities, slow growth, mental impairment, possible heart problems, and poor coordination. The damage is permanent.
What does smoking lead to during pregnancy?
Increases risk of miscarriage, adversely affects fetal growth and development. Carbon monoxide in the smoke can outcompete oxygen for the binding sites on hemoglobin. Children of smokers are more likely to die of post delivery problems, be smaller, and have more heart defects.
What can Thalidomide lead to?
Infants of some of the women who used it during the first trimester had severely deformed arms and legs or none at all.
What can use of Isotretinoin (Accutane) lead to?
If taken early in a pregnancy, it can cause facial and cranial deformities and heart problems in the embryo.
What is the birth process known as?
What is Afterbirth?
Expelled placenta from the uterus.
What is Lactation?
Milk production from the breast.
What is Prolactin?
A hormone secreted by the mother's anterior pituitary that triggers milk synthesis.
What causes milk production to increase?
A decline in progesterone and estrogens after birth.
What does human milk have to benefit the newborn child?
It's nutrient rich, and has antibodies to protect it from some viruses and bacteria.
Stages of Human Development: What is the Zygote period?
Single cell resulting from fusion of sperm nucleus and egg nucleus at fertilization.
Stages of Human Development: What is the Morula period?
Solid ball of cells produced by cleavages.
Stages of Human Development: What is the Blastocyte (blastula) period?
Ball of cells with surface layer, fluid-filled cavity, and inner cell mass.
Stages of Human Development: What is the Embryo period?
All developmental stages from two weeks after fertilization until end of eighth week.
Stages of Human Development: What is the Fetus period?
All developmental stages from ninth week to birth (about 38 weeks after fertilization).
Stages of Human Development: What is the Newborn period?
Individual during the first two weeks after birth.
Stages of Human Development: What is the Infant period?
Individual from two weeks to about fifteen months after birth.
Stages of Human Development: What is the Child period?
Individual from infancy to about ten or twelve years.
Stages of Human Development: What is the Pubescent period?
Individual at puberty; secondary sexual traits develop; girls between 10 and 15 years, boys between 11 and 16 years.
Stages of Human Development: What is the Adolescent period?
Individual from puberty until about 3 or 4 years later; physical, mental, emotional maturation.
Stages of Human Development: What is the Adult period?
Early adulthood (between 18 and 25 years); bone formation and growth finished. Changes proceed slowly after this.
Stages of Human Development: What is the Old Age period?
Aging processes result in expected tissue deterioration.
Birth before what week is considered premature?
What is the earliest a fetus can be born and live, with modern medicine?
As early as 23 weeks, but it may have disabilities.
What is the Programmed Life Span Hypothesis?
Life span is genetically determined.
What is telomeres?
On chromosomes, caps that are made of DNA and proteins. When only a nub of telomere remains, cells stop dividing and die.
How many times do normal human cells divide?
No more than 50 times.
Why can cancer and germ cells divide indefinitely?
Because they make telomerase, an enzyme that lengthens telomeres.