9. Reproduction and Embryogenesis

A) One

Explanation: One egg (ovum) is produced as a result of one meiotic series of cell divisions, along with three polar bodies that typically degenerate.

B) Assists in endometrial regrowth

Explanation: Progesterone assists in the regrowth of the endometrial lining, which is crucial for maintaining a pregnancy. It also inhibits the release of FSH and LH.

A) Efforts to improve the genetic quality of the human population

Explanation: Eugenics refers to efforts aimed at improving the genetic quality of the human population, often through selective breeding or genetic manipulation.

B) They may outpace current regulations

Explanation: There is concern that rapid advancements in reproductive technologies could outpace existing regulations, leading to potential ethical and legal challenges.

C) Multiple sperm fusion results in a non-viable embryo

Explanation: If the mechanism to prevent polyspermy fails, multiple sperm fusion occurs, resulting in a non-viable embryo that dies within days.

D) It is involved in calcium metabolism

Explanation: Estrogen is involved in calcium metabolism, which is crucial for maintaining proper calcium levels in the body.

C) 28 days

Explanation: The average duration of both the ovarian and menstrual cycles is 28 days, although they can range from 22 to 32 days.

B) Young are born alive and receive nourishment directly from the female

Explanation: In viviparity, young are born alive and receive nourishment directly from the female, which is a key characteristic distinguishing it from other reproductive strategies.

C) The endometrium degenerates as progesterone levels drop

Explanation: If no implantation occurs during the Secretory Phase, the endometrium degenerates as progesterone levels drop, starting the next menstrual cycle.

C) They are not directly connected

Explanation: The oviducts extend from the uterus to the ovaries but are not directly connected. The fimbriae help guide the egg into the oviduct.

C) It must implant into the uterine wall

Explanation: The embryo must implant into the uterine wall within seven days to survive, ensuring it can receive nutrients and continue developing.

B) Epithelial and neuronal tissues

Explanation: The ectoderm forms epithelial and neuronal tissues during the neural system formation in vertebrates, playing a crucial role in the development of the nervous system.

C) Invertebrates like earthworms, slugs, tapeworms, and snails

Explanation: Hermaphroditism is common in invertebrates such as earthworms, slugs, tapeworms, and snails.

C) Clitoris

Explanation: The tissue that produces a penis in males produces a clitoris in females, making them homologous structures.

C) Progesterone

Explanation: During the Secretory Phase (Days 15 - 28), progesterone from the corpus luteum maintains the endometrium, preparing the uterus to accept a fertilized egg.

C) Prophase I

Explanation: The primary oocyte starts meiosis but is arrested in prophase I at birth, remaining in this stage until puberty.

D) XX

Explanation: In mammals, individuals with two X chromosomes (XX) are female.

B) Individuals start as female

Explanation: Protogyny, meaning 'first female,' refers to individuals that start their lives as females and may later change to males.

A) Oysters

Explanation: Oysters are an example of protandry, where individuals start as males and later become females to lay eggs.

B) Formation of a zygote

Explanation: Fertilization is the process in which sperm and egg fuse to form a zygote, which is the initial cell formed when two gamete cells are joined by means of sexual reproduction.

B) Depression

Explanation: Depression is a side effect of menopause that can significantly affect mental health, often due to hormonal changes and other physical symptoms.

B) To release eggs and prepare endocrine tissues

Explanation: The ovarian cycle is responsible for preparing endocrine tissues and releasing eggs, which are crucial for reproduction.

B) By mating with another of their species and fertilizing each other

Explanation: Hermaphrodites typically mate with another of their species, fertilizing each other and both producing offspring.

B) A corpus luteum

Explanation: After ovulation, the ruptured follicle transforms into a corpus luteum, which plays a role in hormone production before eventually degenerating.

C) Produce a thick, alkaline fluid

Explanation: The seminal vesicles produce a thick, alkaline fluid that includes mucus, fructose, enzymes, ascorbic acid, and prostaglandins, which accounts for 60% of semen volume.

C) By environmental factors

Explanation: In species with environmental sex determination, sex is determined by environmental factors rather than chromosomes. For example, in alligators, some turtles, and tuataras, the temperature during the middle third of egg development determines the sex.

B) To differentiate into various cell types needed by the organism

Explanation: Embryonic stem cells have the potential to differentiate into various cell types needed by the organism, making them crucial for development.

B) A surgical alternative to vaginal delivery

Explanation: A Caesarian Section is a surgical procedure used as an alternative to vaginal delivery when necessary for the safety of the mother or baby, though it involves post-surgical risks.

B) External fertilization

Explanation: External fertilization is when the fusion of sperm and egg occurs outside the female's body, as seen in frogs.

B) They help the sperm degrade the glycoprotein matrix protecting the egg

Explanation: Acrosomal reactions help the sperm degrade the glycoprotein matrix protecting the egg, allowing the sperm to transfer its nucleus into the egg.

C) To form the placenta and provide nourishment to the embryo

Explanation: The Trophoblast forms the placenta and provides nourishment to the embryo, playing a crucial role in early development.

D) In the Inner Cell Mass

Explanation: Embryonic stem cells are located in the Inner Cell Mass of the blastocyst, where they have the potential to differentiate into various cell types needed by the organism.

C) To restart stalled labor

Explanation: Synthetic oxytocin, known as Pitocin, is used to restart labor if it stalls before stage two, helping to ensure the progression of childbirth.

C) Moderate temperatures

Explanation: In some crocodiles and turtles, moderate temperatures produce males, while both warm and cool temperatures produce females. This demonstrates the variability in environmental sex determination.

B) The uterus and vaginal muscles contract in waves

Explanation: In females, the orgasm phase is characterized by the contraction of the uterus and vaginal muscles in waves.

B) To release a fluid that neutralizes acid residue in the urethra before ejaculation

Explanation: The Bulbourethral (Cowper’s) Gland releases a fluid that neutralizes acid residue in the urethra before ejaculation, ensuring a safer passage for sperm.

C) Insomnia

Explanation: Insomnia, or difficulty sleeping, is a common physical change during menopause, often caused by hormonal fluctuations and other symptoms like hot flashes and night sweats.

B) Frog reproduction

Explanation: Frog reproduction is an example of external fertilization, where the fusion of sperm and egg occurs outside the female's body.

B) To prepare and maintain the uterine lining

Explanation: The menstrual cycle's primary function is to prepare and maintain the uterine lining, making it suitable for potential implantation of a fertilized egg.

C) To develop and surround eggs

Explanation: The cortex of the ovaries contains follicular cells that surround and develop eggs, playing a crucial role in the reproductive process.

C) 22-32 days

Explanation: Both the ovarian and menstrual cycles occur concurrently over a period of 22-32 days, with an average duration of 28 days.

B) Enlargement of the nipples, clitoris, labia, and penis

Explanation: During the excitement phase, vasodilation leads to increased blood flow (vasocongestion) in erectile tissues, resulting in the enlargement of the nipples, clitoris, labia, and penis.

B) They prepare eggs for release

Explanation: During menstruation, the follicular cells in the cortex of the ovaries prepare eggs for release, which is a key part of the menstrual cycle.

C) Neural tube

Explanation: The central region of the ectoderm forms the neural tube, which is crucial for the development of the brain and the spinal cord.

C) Common in both terrestrial and some aquatic animals

Explanation: Internal fertilization is common in terrestrial animals but is also used by some aquatic animals, indicating its versatility across different environments.

B) They are discarded as polar bodies

Explanation: During egg production, extra chromosomes and chromatids are discarded as polar bodies.

C) Blastula

Explanation: The cells rearrange themselves to form a hollow ball with a fluid-filled or yolk-filled cavity called the blastula.

B) It inhibits the release of GnRH, FSH, and LH

Explanation: Rising testosterone levels trigger a negative feedback system that inhibits the release of GnRH, FSH, and LH, thereby regulating hormone levels and spermatogenesis.

B) It inhibits the release of GnRH and FSH

Explanation: Inhibin inhibits the release of GnRH and FSH, which slows down spermatogenesis when sperm count is high.

C) Fertilized eggs are retained in the female’s body

Explanation: In ovoviparity, fertilized eggs are retained in the female’s body, and the embryos get nourishment from the yolk until they hatch inside or just before being laid.

B) From the yolk

Explanation: In ovoviparous animals, embryos get nourishment from the yolk until they hatch inside or just before being laid.

C) Testosterone

Explanation: The release of testosterone from male gonads in utero causes the undeveloped reproductive tissues to differentiate into male sexual organs.

B) The reproductive accessory glands and tubules contract to move semen into the urethra

Explanation: In males, during the orgasm phase, the reproductive accessory glands and tubules contract, moving semen into the urethra, which then contracts to expel the semen.

A) Cortex and medulla

Explanation: The ovaries are composed of the medulla, which contains nerves and blood vessels, and the cortex, which is the functional part containing follicular cells.

C) Ovaries

Explanation: In the absence of testosterone, primitive gonads develop into ovaries.

B) The size of a fist

Explanation: The uterus is approximately the size of a fist, which provides a reference for its dimensions within the female reproductive system.

C) Prostate gland

Explanation: The prostate gland surrounds the urethra and produces a thin, milky fluid containing citrate, enzymes, and PSA, which accounts for about 30% of semen volume.

B) The physiological changes from the first three phases reverse

Explanation: During the resolution phase, the physiological changes from the excitement, plateau, and orgasm phases reverse, returning the body to its normal state.

B) Ligaments

Explanation: The ovaries are held in place by ligaments within the abdominal cavity, ensuring their proper positioning and function.

C) Testes

Explanation: In the presence of testosterone, primitive gonads develop into testes.

C) To supply milk

Explanation: The primary function of the ducts in the breast is to supply milk, which is rich in nutrients and antibodies, to the nursing child.

B) The combination of reproductive cells from two individuals to form genetically unique offspring

Explanation: Sexual reproduction involves the combination of reproductive cells (gametes) from two individuals, resulting in offspring that are genetically unique.

C) Mammary glands and fat

Explanation: Breasts are composed of mammary glands and fat, which together determine their structure and function.

C) Suckling

Explanation: Suckling triggers the release of prolactin, which is responsible for milk production, and oxytocin, which aids in milk ejection, providing essential nutrients and immunity to the baby.

B) Warmer temperatures

Explanation: In many turtles, warmer incubation temperatures produce females, while cooler temperatures produce males. This is an example of how environmental factors can influence sex determination.

C) Production of sperm

Explanation: The penis functions in urine excretion, as a copulatory organ, contains erectile tissue, and expels semen through the urethra during ejaculation, but it does not produce sperm.

C) Nine weeks

Explanation: The content specifically mentions that fetal development is shown at nine weeks gestation, indicating this particular stage of pregnancy.

B) Rapid and precise movements of cells

Explanation: Organogenesis is characterized by rapid and precise movements of the cells within the embryo, which are crucial for the proper formation of organs.

C) Cervical thinning and dilation to about 10 cm

Explanation: The first stage of labor involves cervical thinning and dilation to about 10 cm.

C) Due to the Nazi eugenics programs in the 1930s and 40s

Explanation: Eugenics was discredited after the Nazi eugenics programs in the 1930s and 40s, which involved unethical and inhumane practices aimed at improving the genetic quality of the population.

C) Ectoderm

Explanation: The ectoderm is the outermost germ layer and is responsible for forming the nervous system, including the brain and spinal cord.

B) LH

Explanation: Luteinizing Hormone (LH) is responsible for inducing ovulation in females, which is a critical part of the reproductive process.

B) It facilitates uterine lining regrowth and inhibits FSH and LH release

Explanation: Progesterone produced by the corpus luteum facilitates the regrowth of the uterine lining and inhibits the release of FSH and LH, preparing the body for potential pregnancy.

C) Endoderm

Explanation: The endoderm is the germ layer that gives rise to cells in the digestive system and other internal organs.

B) Decreased bone density

Explanation: Calcium loss from bones leads to decreased bone density, which can result in conditions such as osteoporosis.

B) First fetal movements

Explanation: During the second trimester, the mother typically feels the first fetal movements, which is a notable milestone in pregnancy.

C) It completes meiosis and becomes a mature oocyte

Explanation: Twenty-four hours before fertilization, the egg has completed meiosis and is a mature oocyte, ready for fertilization.

B) Contraction of glands and accessory organs

Explanation: Ejaculation involves the contraction of glands and accessory organs, leading to the expulsion of semen through the urethra.

D) Intrauterine devices (IUDs)

Explanation: Barrier methods include condoms, cervical caps, and diaphragms, which block sperm from entering the uterus. IUDs are not considered barrier methods.

C) Notochord

Explanation: The notochord is a rod-shaped structure in the mesoderm that forms the central axis of the body, providing structural support during development.

B) The embryo

Explanation: The Inner Cell Mass, also known as the Embryoblast, will develop into the embryo, which is the developing organism.

B) Internal fertilization

Explanation: Internal fertilization occurs inside the body of the female, as seen in humans.

A) Segments along the length of the body

Explanation: In a five-week-old human embryo, somites are segments that form along the length of the body, playing a crucial role in the development of the vertebral column, ribs, and associated musculature.

C) In the fallopian tube

Explanation: In humans, fertilization typically occurs in the fallopian tube soon after the oocyte leaves the ovary.

B) Stratified squamous epithelial cells

Explanation: The vagina is lined with stratified squamous epithelial cells, which provide protection against friction and potential pathogens.

C) Abstinence

Explanation: Abstinence is the only method that is completely effective in preventing conception, as it involves refraining from sexual activity altogether.

D) Behind the female

Explanation: The male toad grasps the female from behind during the fertilization process, which is a common behavior in many amphibian species to ensure successful fertilization.

B) Heart

Explanation: The heart is typically the first organ to form during vertebrate organogenesis, beginning to beat and circulate blood early in development.

B) A spherical layer of cells surrounding a fluid-filled cavity

Explanation: A blastula is characterized by a spherical layer of cells, known as the blastoderm, surrounding a fluid-filled cavity called the blastocoel.

C) Drop in progesterone levels

Explanation: The drop in progesterone levels, caused by the degeneration of the corpus luteum, initiates the next menstrual cycle.

B) To guide the egg into the tube

Explanation: The fimbriae are finger-like projections at the ends of the oviducts that help guide the egg into the tube, ensuring it enters the oviduct for potential fertilization.

C) To move the egg towards the uterus

Explanation: The ciliated walls of the oviducts consist mostly of smooth muscle that helps move the egg towards the uterus, facilitating its journey for potential fertilization and implantation.

C) By the X and Y chromosomes

Explanation: In mammals, sex determination is genetically controlled by the X and Y chromosomes. XX individuals are female, and XY individuals are male.

C) Seminiferous tubules

Explanation: Sperm are produced in the seminiferous tubules, which are located within the testes. These tubules are the site of spermatogenesis, the process of sperm production.

C) Growth factors

Explanation: Growth factors signal some ectoderm cells to become epidermal, while others form the neural plate, which is essential for the development of the neural system.

B) Monitoring menstrual cycle changes

Explanation: Natural family planning involves monitoring menstrual cycle changes, such as temperature rise and cervical mucus, to prevent pregnancy.

C) Because they have limited mobility or are not motile

Explanation: Self-fertilization is more common in animals with limited mobility or that are not motile, such as barnacles and clams.

C) Third trimester

Explanation: Rapid fetal growth is specifically noted to occur during the third trimester, which is a critical period for the development and maturation of the fetus.

D) 8-9 days

Explanation: Implantation of the fertilized oocyte into the uterine wall occurs approximately eight or nine days after fertilization.

B) Progesterone

Explanation: Progesterone inhibits the release of FSH (Follicle Stimulating Hormone) and LH (Luteinizing Hormone), which are essential for the regulation of the menstrual cycle and ovulation.

B) Externally as the eggs are deposited

Explanation: In toads, the male grasps the female from behind and externally fertilizes the eggs as they are deposited, ensuring that the sperm comes into contact with the eggs immediately.

C) Birth control pills

Explanation: Birth control pills are a reversible contraceptive method that offers short-term contraception and can be discontinued if pregnancy is desired.

B) Fetal viability

Explanation: A voluntary termination of pregnancy, or abortion, is often regulated based on fetal viability and is subject to varying state laws.

C) Testes

Explanation: The testes are the primary reproductive structures in the human male, responsible for producing sperm and testosterone.

B) Cleavage

Explanation: Cleavage is the term used to describe the rapid division of the zygote into multiple smaller cells, which is a crucial step in early embryonic development.

D) Urethra

Explanation: The urethra is a tube that serves both the male reproductive system, by transporting semen, and the urinary system, by transporting urine.

B) Days 6 - 14

Explanation: The Proliferative Phase occurs from Days 6 to 14 of the menstrual cycle, during which the endometrium regrows due to rising estrogen levels.

C) Zygote

Explanation: At conception, the egg becomes a zygote, which is the initial cell formed when a sperm cell fertilizes an egg cell.

A) Ectoderm, Mesoderm, Endoderm

Explanation: The three germ layers in the animal body are the ectoderm, mesoderm, and endoderm. These layers give rise to different cell types and tissues during embryonic development.

C) In the follicles located in the ovary

Explanation: Oocytes develop in follicles, which are located in the ovary. This is a crucial part of the female reproductive system.

B) A female changes sex to become the new dominant male

Explanation: In wrasses, a family of reef fishes, if the dominant male dies, a female will change sex to become the new dominant male, ensuring the continuation of the population.

B) The amount of fat behind the gland

Explanation: Breast size is determined by the amount of fat behind the mammary gland, not by the number of lobes or the size of the mammary glands.

B) Rhythmic, involuntary muscle contractions

Explanation: During the orgasm phase, both sexes experience rhythmic, involuntary muscle contractions, which are a key characteristic of this phase.

C) Brain and spinal cord

Explanation: The neural tube, formed from the central region of the ectoderm, develops into the brain and the spinal cord, which are essential components of the central nervous system.

C) Both A and B

Explanation: Internal fertilization can involve either direct sperm deposition into the female or depositing sperm in a protective structure for the female to pick up, showcasing the different strategies used for successful fertilization.

B) Expulsion of the baby from the uterus

Explanation: The second stage of labor is characterized by the expulsion of the baby from the uterus.

B) The sperm plasma membrane fuses with the egg plasma membrane

Explanation: During the fusion of membranes, the sperm plasma membrane fuses with the egg plasma membrane, enabling the transfer of the sperm nucleus into the egg.

A) The egg releases proteins to block additional sperm

Explanation: After the initial sperm entry, the egg releases proteins to block additional sperm from entering, preventing polyspermy.

B) Establishment of the body plan for organ development

Explanation: Gastrulation is the process where cells in the blastula rearrange to form three germ layers, which establishes the body plan necessary for organ development.

B) Prostate gland

Explanation: The prostate gland produces seminal fluid, which is a component of semen that helps nourish and transport sperm.

A) Most mammals, some cartilaginous fish, and a few reptiles

Explanation: Viviparity is seen in most mammals, some cartilaginous fish, and a few reptiles, where the young are born alive and receive nourishment directly from the female.

B) It forms the placenta

Explanation: The trophoblast in the mammalian blastocyst plays a crucial role in forming the placenta, which provides nutrients and support to the developing embryo.

B) Holoblastic cleavage

Explanation: Holoblastic (total) cleavage is the complete division of the egg and occurs in species with little yolk, such as placental mammals.

B) Contraception specifically refers to preventing sperm and egg from meeting

Explanation: Contraception specifically refers to methods that prevent sperm and egg from meeting, although the terms are often used interchangeably with birth control.

C) Endoderm

Explanation: The endoderm is the germ layer that develops into the lining of the digestive and respiratory systems, as well as other internal organs.

B) Heavy sweating

Explanation: Heavy sweating, especially at night, is a common symptom of menopause, often associated with hot flashes and hormonal changes.

B) To protect the egg

Explanation: The glycoprotein matrix protects the egg, creating a barrier that the sperm must degrade through acrosomal reactions to transfer its nucleus.

D) 60%

Explanation: The seminal vesicles account for 60% of the semen volume, making them a significant contributor to the composition of semen.

A) The vas deferens carries sperm from the testes to the penis.

Explanation: The vas deferens actually carries sperm from the epididymis to the urethra, not directly to the penis. The other statements are true regarding the male reproductive system.

B) They are hermaphrodites

Explanation: Many snails are hermaphrodites, meaning they possess both male and female reproductive organs, allowing them to mate with any other individual of their species.

C) Stimulates development of egg cells (ova) in follicles

Explanation: FSH (Follicle Stimulating Hormone) in females stimulates the development of egg cells (ova) within the ovarian follicles, which is a critical step in the reproductive process.

C) The intentional creation of a child with a disability

Explanation: The ethical debate centers around the intentional creation of a child with a disability, as some parents choose embryos that share their own disabilities for cultural and personal reasons.

C) The implications and regulation of genetic engineering and its affordability

Explanation: Ongoing discussions focus on the ethical implications, regulation, and affordability of genetic engineering as technology continues to advance.

B) Formation of the blastula

Explanation: Cleavage results in the formation of the blastula, which is a spherical layer of cells surrounding a fluid-filled cavity.

C) By regulating the menstrual cycle

Explanation: Estradiol and progesterone prepare the body for pregnancy by regulating the menstrual cycle, ensuring the reproductive system is ready for potential fertilization and implantation.

C) They decrease

Explanation: Without estrogen, blood levels of calcium decrease, which can lead to various health issues.

B) Inner cell mass and trophoblast

Explanation: During the rearrangement of cells in the mammalian blastula, the two layers that are formed are the inner cell mass and the trophoblast.

C) Nutrition, waste management, and hormone production

Explanation: In the second trimester, the placenta takes over the roles of nutrition, waste management, and hormone production (estrogen and progesterone) as the corpus luteum degenerates.

C) Through the oviduct to the uterus

Explanation: After fertilization, the zygote travels through the oviduct (fallopian tube) to the uterus, where it will eventually implant.

B) Seminal vesicles

Explanation: The seminal vesicles produce most of the bulk of semen. They secrete a fluid that is rich in fructose and other substances that provide energy and aid in the motility of sperm.

C) Hot flashes

Explanation: Hot flashes are a common side effect of menopause, characterized by sudden feelings of warmth, which are often most intense over the face, neck, and chest.

C) Humans

Explanation: Humans typically undergo internal fertilization, where the fusion of sperm and egg occurs inside the female's body.

B) The placenta takes over more functions

Explanation: As the fetus enters the second trimester, the placenta takes over more of the functions necessary for the baby's development, such as nutrient and waste exchange.

C) Up to 100 eggs

Explanation: When two snails mate, each individual can produce up to 100 eggs, highlighting their reproductive capacity.

B) One

Explanation: Typically, one egg is produced per menstrual cycle.

B) To use donors with high IQs

Explanation: Robert Klark Graham’s sperm bank aimed to use donors with high IQs in an effort to improve the genetic quality of the human population, but it was unsuccessful and closed in 1999.

C) It involves concerns about the discarding of unused embryos

Explanation: One ethical issue associated with Prenatal Genetic Diagnosis (PGD) is the concern about the discarding of unused embryos, which raises moral and ethical questions about the value and status of these embryos.

B) Neurulation

Explanation: Neurulation is the process during embryonic development that leads to the formation of the neural tube, which eventually becomes the brain and spinal cord.

B) Muscle cells and connective tissues

Explanation: The mesoderm is responsible for forming muscle cells and connective tissues during embryonic development.

B) In the outer layers of the ovaries

Explanation: Oogenesis occurs specifically in the outer layers of the ovaries, where germ cells undergo various stages of development.

B) Osteoporosis

Explanation: Decreased bone density due to calcium loss can lead to osteoporosis, a condition characterized by weak and brittle bones.

C) A sterilization method where oviducts are severed and sealed

Explanation: Tubal ligation is a sterilization method in which the oviducts are severed and sealed, preventing eggs from traveling to the uterus and thus preventing pregnancy.

B) Meroblastic cleavage

Explanation: Meroblastic (partial) cleavage is characterized by partial division of the egg due to substantial yolk content, as seen in species like birds.

B) Some fish, crustaceans, insects, and reptiles

Explanation: The ZW sex determination system is used by some fish, crustaceans, insects (e.g., butterflies and moths), and reptiles.

B) Sperm are present in the bulbourethral gland secretions

Explanation: Withdrawal before ejaculation may not prevent pregnancy because sperm can be present in the bulbourethral gland secretions, which can be released before full ejaculation.

B) Ribs and lungs

Explanation: Somites, formed from the mesoderm, develop into structures such as ribs and lungs, playing a critical role in the formation of the vertebrate body plan.

C) Fertilization

Explanation: Fertilization is the process where a sperm and an egg fuse, leading to the formation of a zygote.

B) Fission

Explanation: The Anthopleura artemisia sea anemone reproduces through fission, a form of asexual reproduction where the organism splits into two or more parts, each of which develops into a new individual.

B) The process of expelling the fetus and placenta from the uterus

Explanation: Labor is defined as the process of expelling the fetus and placenta from the uterus during birth.

C) Delivery of the placenta

Explanation: The third stage of labor involves the delivery of the placenta.

C) Tubal ligation

Explanation: Tubal ligation is a permanent contraceptive method where a woman's fallopian tubes are surgically cut or sealed to prevent pregnancy.

C) Muscles and bones

Explanation: The mesoderm is the middle germ layer that develops into muscles, bones, the circulatory system, and other internal structures.

B) The corpus luteum forms and produces estrogen and progesterone

Explanation: During the luteal phase, the ruptured follicle forms the corpus luteum, which produces estrogen and progesterone, facilitating uterine lining regrowth and inhibiting further FSH and LH release.

B) Some bony fish, sharks, lizards, snakes, and some invertebrates

Explanation: Ovoviparity is seen in some bony fish (e.g., platyfish), sharks, lizards, snakes (e.g., garter snake), and some invertebrates (e.g., Madagascar hissing cockroach).

B) Choosing traits like sex, disease resistance, and physical attributes

Explanation: Current practices in genetic engineering are making it increasingly feasible to choose traits such as sex, disease resistance, and physical attributes in 'designer babies'.

C) 30 cm (12 inches)

Explanation: During the second trimester, the fetus grows to about 30 cm (12 inches) in length, marking a significant period of growth.

C) To prepare to accept a fertilized egg

Explanation: During the Secretory Phase, the uterus prepares to accept a fertilized egg, with progesterone from the corpus luteum maintaining the endometrium.

D) Y chromosome

Explanation: The presence of a Y chromosome in mammals leads to the development of male characteristics.

B) It becomes flaccid as blood drains from erectile tissue

Explanation: After ejaculation, the penis becomes flaccid as blood drains from the erectile tissues, returning it to its non-erect state.

A) Primary spermatocyte

Explanation: The primary spermatocyte is diploid, meaning it contains two sets of chromosomes. During spermatogenesis, it undergoes the first meiotic division to form secondary spermatocytes, which are haploid.

B) The follicle ruptures, releasing the egg

Explanation: During ovulation, the mature follicle ruptures and releases the egg, which is a key event in the menstrual cycle.

D) Egg degradation

Explanation: Egg degradation is not a step in the fertilization process. The steps include sperm and egg fusion, formation of a zygote, acrosomal reaction, and transfer of the sperm nucleus.

A) Clitoris

Explanation: The clitoris and the penis share the same embryonic origin, both developing from the genital tubercle during fetal development.

A) Allowing menstrual flow, receiving the penis during intercourse, and delivering offspring

Explanation: The vagina serves multiple functions including allowing menstrual flow, receiving the penis during intercourse, and delivering offspring, making it a crucial part of the female reproductive system.

C) Inhibin

Explanation: Follicle cells produce inhibin, a hormone that inhibits the production of FSH (Follicle Stimulating Hormone), thereby regulating the development of egg cells.

C) The development of organs from the three germ layers

Explanation: Organogenesis is the phase of embryonic development during which the organs form from the three primary germ layers: ectoderm, mesoderm, and endoderm.

B) Miscarriage

Explanation: A miscarriage is a spontaneous termination of pregnancy, usually occurring in early pregnancy due to developmental issues.

C) 20 million/ml

Explanation: Sertoli cells stop releasing inhibin when the sperm count reaches 20 million/ml, allowing the sperm count to increase.

B) Blastocoel

Explanation: The fluid-filled cavity within the blastula is known as the blastocoel, which is surrounded by a spherical layer of cells called the blastoderm.

C) Transports sperm from the epididymis to the urethra

Explanation: The vas deferens is a duct that transports sperm from the epididymis to the urethra in preparation for ejaculation.

D) Oviducts

Explanation: Fertilization typically occurs in the oviducts (Fallopian tubes), where the sperm meets the egg. The fertilized embryo then moves to the uterus for implantation.

C) 3-4 kg (6.5-8.5 lbs)

Explanation: During the third trimester, the fetus grows to approximately 3-4 kg (6.5-8.5 lbs), indicating significant weight gain and development.

C) Below the bladder

Explanation: The prostate gland is actually located below the bladder, not in the testes. It plays a crucial role in the male reproductive system by secreting prostate fluid, one of the components of semen.

C) Animals having both male and female reproductive systems

Explanation: Hermaphroditism involves animals having both male and female reproductive systems, allowing them to produce both eggs and sperm.

B) Brain and spinal cord

Explanation: The neural plate rolls up to form the neural tube, which subsequently develops into the brain and spinal cord, fundamental components of the central nervous system.

B) By spatial reorganization

Explanation: The mesoderm is organized into somites through specific gene expression patterns that lead to spatial reorganization, essential for proper vertebrate development.

C) They have three sex chromosomes

Explanation: Some species, such as swordtail fish, have a complex chromosomal system with three sex chromosomes in a population, which is different from the typical two sex chromosomes found in many other species.

D) Uterus

Explanation: The uterus has an endometrial lining that thickens in preparation to support a developing baby, providing the necessary environment for implantation and growth.

B) Before birth

Explanation: Egg production in females begins before birth but is halted during meiosis until puberty.

B) During meiosis

Explanation: Egg production begins before birth but is halted during meiosis until puberty.

B) It stimulates spermatogenesis

Explanation: Testosterone is crucial for the stimulation of spermatogenesis, the process of sperm production in the male reproductive system.

C) It plays a role in ova development

Explanation: LH in females is crucial for ova development, induces ovulation, and stimulates the production of estradiol and progesterone by the ovaries.

B) Produces secondary sex characteristics

Explanation: Estradiol is responsible for producing secondary sex characteristics in females, such as breast development and the regulation of the menstrual cycle.

C) The corpus luteum degenerates, causing hormone levels to drop

Explanation: If no fertilized egg implants, the corpus luteum degenerates, leading to a drop in estrogen and progesterone levels, which initiates the next menstrual cycle.

C) The uterine lining is shed

Explanation: During the menstrual phase, if no pregnancy occurs, the uterine lining is shed, marking the beginning of the menstrual cycle.

C) Oogonia

Explanation: Oogonia are the germ cells that undergo mitosis to increase in number, resulting in about 1 - 2 million cells in the embryo.

B) After cleavage

Explanation: The mammalian blastula becomes a blastocyst after the cleavage stage, during which the cells rearrange into the inner cell mass and the trophoblast.

B) Blood filling erectile tissues

Explanation: An erection is caused by blood filling the erectile tissues in the penis, leading to its enlargement and rigidity.

C) Ectoderm

Explanation: The ectoderm is the germ layer that gives rise to the nervous system, including the brain and spinal cord.

B) By killing sperm

Explanation: Spermicides are chemicals used to kill sperm and are available in various forms like gels and sponges.

B) Individuals start as male

Explanation: Protandry, meaning 'first male,' refers to individuals that start their lives as males and may later change to females.

A) To increase genetic diversity

Explanation: Many species have mechanisms to prevent self-fertilization due to its association with inbreeding and producing less fit offspring, thereby increasing genetic diversity.

B) At the nipple

Explanation: The ducts in the breast empty at the nipple, which is the point where milk is supplied to the nursing child.

B) Gastrulation

Explanation: Gastrulation is the process that leads to the formation of the three germ layers in an embryo, which are essential for the development of different organs in the animal body.

B) Estrogen

Explanation: Towards the end of the third trimester, estrogen helps receptors on the uterine wall bind with oxytocin, leading to contractions and the release of more oxytocin.

B) The zygote rapidly divides into multiple cells without increasing in size

Explanation: During cleavage, the zygote undergoes rapid cell division, resulting in multiple cells, but the overall size of the zygote does not increase.

C) The nuclear membranes of the egg and sperm dissolve

Explanation: During genomic fusion, the nuclear membranes of the egg and sperm dissolve, combining the two haploid genomes into a diploid genome.

C) Inhibin

Explanation: Sertoli cells produce the hormone inhibin, which is released into the blood when sperm count is high to help regulate spermatogenesis.

C) Ectoderm

Explanation: The ectoderm is the germ layer that develops into the nervous system and the epidermis, which includes the outer layer of skin.

B) Stores and matures sperm

Explanation: The epididymis is a coiled tube where sperm are stored and mature before being transported through the vas deferens.

B) Rising estrogen levels cause the endometrium to regrow

Explanation: During the Proliferative Phase (Days 6 - 14), rising estrogen levels cause the endometrium to regrow, and blood vessels and glands in the endometrium are replenished.

B) Developing into the embryo

Explanation: The inner cell mass in the mammalian blastocyst is responsible for developing into the embryo.

C) Frequent urination

Explanation: Frequent urination is a common maternal discomfort during the third trimester due to the pressure of the growing fetus on the bladder.

B) The ability to change sex during an individual's life

Explanation: Sequential hermaphroditism refers to the phenomenon where some species change their sex during their lives, which can be an adaptive reproductive strategy.

B) The percentage of pregnancies occurring with a method over a year

Explanation: Contraceptive failure rates indicate the percentage of pregnancies occurring with a method over a year, reflecting typical rather than ideal use.

C) To create the circulatory and skeletal systems

Explanation: The mesoderm is primarily responsible for forming the circulatory and skeletal systems, along with muscles and other connective tissues.

D) Improved skin elasticity

Explanation: Improved skin elasticity is not a side effect of menopause. Common side effects include headaches, muscle pain, vaginal dryness, and insomnia.

C) 15 to 25

Explanation: Each breast typically has 15 to 25 lobes, which are part of the mammary gland structure.

B) Organogenesis

Explanation: Organogenesis is the process during which the three germ layers formed during gastrulation give rise to the different organs in the animal body.

B) It resumes with each menstrual cycle

Explanation: At puberty, egg production resumes with each menstrual cycle, producing one egg per cycle.

C) Some countries ban non-medical sex selection while others allow it for family balancing

Explanation: Regulations on sex selection vary by country, with some banning non-medical sex selection and others permitting it for purposes such as family balancing.

B) To prevent genetic diseases like sickle cell disease

Explanation: Prenatal Genetic Diagnosis (PGD) is commonly used to screen embryos for genetic diseases, such as sickle cell disease, before implantation to prevent the birth of affected individuals.

C) Rapid cell division called cleavage

Explanation: The development from a zygote begins with rapid cell division known as cleavage, which is the process that leads to the formation of multiple smaller cells from the single-celled zygote.

E) Produces secondary sex characteristics

Explanation: LH does not produce secondary sex characteristics; this function is attributed to estradiol. LH is involved in ova development, ovulation, and stimulating estradiol and progesterone production.

C) Formation of the blastocyst

Explanation: The rearrangement of cells in the mammalian blastula into two layers, the inner cell mass and the trophoblast, results in the formation of the blastocyst.

C) It decreases bone density

Explanation: Estrogen deficiency leads to decreased bone density, making bones more susceptible to fractures and osteoporosis.

C) An inner cell mass and an outer layer

Explanation: In mammals, the blastocyst is characterized by an inner cell mass (embryoblast) and an outer layer (trophoblast), which are crucial for the development of the embryo and the formation of the placenta.

C) ZZ

Explanation: In birds, individuals with two Z chromosomes (ZZ) are male.

C) Mesoderm

Explanation: The mesoderm is the germ layer that forms the muscles, bones, and other connective tissues in the body.

C) It matures

Explanation: At the beginning of the menstrual cycle, the follicle matures in preparation for ovulation.

C) To degrade the glycoprotein matrix protecting the egg

Explanation: The acrosome contains enzymes that help the sperm degrade the glycoprotein matrix protecting the egg, facilitating the transfer of the sperm's nucleus into the egg.

B) An oocyte

Explanation: The light micrograph shows a follicle with an oocyte at its center, highlighting the developmental stage of the oocyte within the follicle.

B) Cooler temperatures

Explanation: In many turtles, cooler incubation temperatures produce males, while warmer temperatures produce females. This is an example of environmental sex determination.

C) Having separate sexes or both sexes in each individual

Explanation: The nature of individuals producing the two kinds of gametes can vary, with some species having separate sexes and others having both sexes in each individual.

C) Enlargement of the outer third of the vaginal wall with blood

Explanation: During the plateau phase, continued stimulation leads to the outer third of the vaginal wall enlarging with blood, along with an increase in breathing and heart rate.

D) Both increase

Explanation: During the plateau phase, both breathing and heart rate increase as a result of continued sexual stimulation.

B) Pre-ejaculatory sperm

Explanation: The withdrawal method has a high failure rate primarily due to the presence of pre-ejaculatory sperm, which can lead to unintended pregnancies even if the penis is withdrawn before ejaculation.

B) In the male's pouch

Explanation: After fertilization, the young seahorses develop in a pouch of the male seahorse until birth, which is a distinctive feature of their reproductive process.

C) Organisms possess both male and female reproductive organs

Explanation: Hermaphroditism is a condition in which an organism has both male and female reproductive organs, allowing them to produce both eggs and sperm.

D) Mammals

Explanation: Fragmentation is observed in sponges, some cnidarians, turbellarians, echinoderms, and annelids, but not in mammals.

B) The placenta forms and takes over nutrient and waste management

Explanation: In the mid-to-late first trimester, the outer layer of the embryo merges with the endometrium, and the placenta forms, taking over the management of nutrients and waste.

C) Uterus

Explanation: The uterus is responsible for housing and nourishing the developing fetus during pregnancy. It provides a protective environment and supplies nutrients to the growing baby.

A) Same tissue as the male scrotum

Explanation: The labia majora derive from the same tissue as the male scrotum.

C) To act as a barrier between the uterus and vagina

Explanation: The cervix acts as a barrier between the uterus and the vagina. It also plays a role in allowing the passage of sperm into the uterus and the exit of menstrual blood from the uterus.

B) They prepare the endometrium for potential pregnancy

Explanation: During the Follicular Phase, estrogens and low levels of progesterone released by the follicles prepare the endometrium for potential pregnancy.

B) They are always hard-shelled

Explanation: The eggs of birds are always hard-shelled, providing protection and a suitable environment for the developing embryo.

C) Seminiferous tubules

Explanation: Each testis is divided into lobules containing seminiferous tubules, where sperm is produced.

B) To support the embryo and fetus during gestation

Explanation: The endometrium lining of the uterus is rich in blood vessels and mucus glands, providing essential support for the embryo and fetus during gestation.

D) Citrate

Explanation: The fluid produced by the seminal vesicles includes mucus, fructose, enzymes, ascorbic acid, and prostaglandins, but not citrate. Citrate is found in the fluid produced by the prostate gland.

B) Linckia multifora

Explanation: Linckia multifora is specifically mentioned as a species of sea star that can reproduce asexually through the process of fragmentation.

D) Testes

Explanation: The testes are part of the male reproductive system, not the female reproductive system. The female reproductive system includes the ovaries, fallopian tubes, uterus, and vagina.

C) The release of eggs and sperm in the same area at the same time

Explanation: Spawning involves one or several females releasing eggs and males releasing sperm in the same area at the same time, facilitating external fertilization.

B) By using synthetic hormones to prevent egg release

Explanation: Hormonal methods of contraception use synthetic hormones to prevent the release of an egg from the ovaries, thereby reducing the likelihood of fertilization.

D) Fallopian tubes

Explanation: Fertilization typically occurs in the fallopian tubes, where the sperm meets and fertilizes the egg before it travels to the uterus for implantation.

B) To maintain the corpus luteum

Explanation: β-HCG maintains the corpus luteum, which is crucial for continued progesterone production, thereby supporting the early stages of pregnancy.

D) In prokaryotic microorganisms and many eukaryotic, single-celled and multi-celled organisms

Explanation: Asexual reproduction occurs in prokaryotic microorganisms (bacteria and archaea) and in many eukaryotic, single-celled and multi-celled organisms, indicating its wide occurrence across different life forms.

C) Internal fertilization

Explanation: Internal fertilization occurs when the male gamete (sperm) is placed inside the female's body, allowing fertilization to take place internally.

C) They degenerate

Explanation: During ovulation, the non-ruptured follicles degenerate, while the most mature follicle ruptures and releases its egg.

B) Leathery eggs

Explanation: Non-avian reptiles and insects typically have leathery eggs, which is a characteristic feature of their reproductive strategy.

C) Hydras and corals

Explanation: Budding commonly occurs in some invertebrate animals such as hydras and corals. These organisms reproduce asexually through the formation of buds that develop into new individuals.

B) Hypothalamus

Explanation: The hypothalamus monitors hormone levels and signals the release of gonadotropin-releasing hormone (GnRH) to the anterior pituitary when reproductive hormones are needed.

C) They are released to lubricate the vagina

Explanation: During the excitement phase, vaginal secretions are released to lubricate the vagina, facilitating sexual activity.

C) Oxytocin

Explanation: Oxytocin is the hormone responsible for milk ejection, which works in conjunction with prolactin to ensure that the baby receives milk during suckling.

B) Increased risk of breast cancer

Explanation: One of the negative side effects of Hormone Replacement Therapy (HRT) in menopause is an increased risk of breast cancer, along with other serious conditions such as stroke, heart attack, and various cancers.

C) They combine to form genetically unique offspring

Explanation: In sexual reproduction, gametes from two individuals combine to form offspring that are genetically unique.

A) Endometrial regrowth, ovulation facilitation, calcium absorption, and secondary sexual characteristics

Explanation: Estrogen assists in endometrial regrowth, facilitates ovulation, aids in calcium absorption, and is responsible for secondary sexual characteristics such as breast development, flaring of hips, and shorter bone maturation period.

B) Rising levels of FSH and LH cause follicle growth

Explanation: During the Follicular Phase (Days 1-14), rising levels of FSH and LH stimulate the growth of follicles on the ovary's surface.

B) Two cell divisions

Explanation: Meiosis involves two cell divisions, which are crucial for separating paired chromosomes and then chromatids, leading to the formation of haploid cells.

C) Enclose the other components of the vulva

Explanation: The labia majora are elongated folds of tissue that run posterior from the mons pubis and enclose the other components of the vulva.

B) The binding of sperm to the zona pellucida

Explanation: The acrosomal reaction is triggered when the sperm binds to the zona pellucida, leading to biochemical changes in the acrosome.

B) It aids in calcium absorption

Explanation: Estrogen aids in calcium absorption, which is important for maintaining bone health.

C) Adherence to the chosen method

Explanation: Compliance or adherence to the chosen contraceptive method significantly affects its success or failure rate. Proper and consistent use is crucial for effectiveness.

B) A form of asexual reproduction where an egg develops without fertilization

Explanation: Parthenogenesis is a type of asexual reproduction in which an egg develops into an individual without being fertilized.

C) The need for reproductive hormones

Explanation: The hypothalamus monitors hormone levels and signals the release of gonadotropin-releasing hormone (GnRH) to the anterior pituitary when reproductive hormones are needed.

B) Provides force for ejaculation

Explanation: The prostate gland provides the force necessary for ejaculation and contributes about 30% of the semen volume.

D) Protection against diabetes

Explanation: Hormone Replacement Therapy (HRT) is thought to protect against colon cancer, heart disease, macular degeneration, and possibly depression, but it is not mentioned as providing protection against diabetes.

B) One secondary oocyte and one polar body

Explanation: The unequal division of the primary oocyte produces one secondary oocyte, which contains most of the cellular material, and one polar body, which has minimal cytoplasm and chromosomes.

C) Liver cancer

Explanation: While Hormone Replacement Therapy (HRT) in menopause has several negative side effects, including stroke, blood clots, gall bladder disease, and possibly dementia, liver cancer is not listed among them.

C) Formation of secondary spermatocytes

Explanation: The primary spermatocyte undergoes meiosis I to produce secondary spermatocytes, which are haploid cells.

C) Through diffusion by the endometrial lining

Explanation: In the early weeks of the first trimester, nutrition and waste for the embryo are managed by the endometrial lining through diffusion, before the placenta is fully formed.

C) A small protrusion on the tubular body

Explanation: The bud initially forms as a small protrusion on the tubular body of the adult hydra before developing a mouth and tentacles.

B) Sertoli cells

Explanation: FSH stimulates Sertoli cells in the testes to facilitate spermatogenesis, which is the process of sperm production.

B) It has a stalk-like body with tentacles growing out the top

Explanation: The hydra has a stalk-like body with tentacles growing out the top, which is a distinctive feature of its morphology.

B) By cutting them in half

Explanation: Fisheries workers attempting to kill sea stars by cutting them in half inadvertently cause them to regenerate, doubling their numbers and increasing the predation on oysters and clams.

C) β-HCG levels

Explanation: Pregnancy tests detect the levels of β-HCG in urine or serum. A positive test indicates the presence of β-HCG, confirming pregnancy.

C) Organs and structures are developing

Explanation: During the first trimester, organs and structures are developing, making the embryo particularly vulnerable to toxins.

C) In invertebrates like water fleas, rotifers, aphids, and some vertebrates like reptiles, amphibians, and fish

Explanation: Parthenogenesis occurs in various invertebrates such as water fleas, rotifers, aphids, and also in some vertebrates like reptiles, amphibians, and fish.

D) Mammals

Explanation: Parthenogenesis is observed in organisms like Komodo dragons, hammerhead sharks, blacktip sharks, and stick insects, but not in mammals.

C) During the third trimester

Explanation: Mammary glands prepare for milk production during the third trimester of pregnancy, ensuring that the mother is ready to provide milk once the baby is born.

B) Hormones

Explanation: Hormones are responsible for triggering primary oocytes to complete the first meiotic division during adolescence.

B) It digests endometrial cells and integrates into the endometrium

Explanation: During implantation, the blastocyst digests endometrial cells and integrates into the endometrium, which is a crucial step for successful pregnancy.

C) It finds its own location for attachment

Explanation: After detaching from its parent, the new hydra is fully developed and will find its own location for attachment, ensuring its survival and growth.

B) The breaking of an individual into parts followed by regeneration

Explanation: Fragmentation is a form of asexual reproduction where an individual breaks into parts, and each part can regenerate into a separate individual if it is large enough.

E) Production of sperm

Explanation: While testosterone influences secondary sexual characteristics such as deepening of the voice, growth of facial hair, and development of sex drive, the production of sperm is directly facilitated by FSH and Sertoli cells.

B) A glycoprotein matrix covering the egg

Explanation: The zona pellucida is a glycoprotein matrix that covers the egg, providing protection and playing a role in the fertilization process.

B) Ectoderm cells differentiating into skin cells

Explanation: An example of cell differentiation is ectoderm cells differentiating into skin cells (epidermal cells), illustrating how specific cell types are formed from embryonic stem cells.

C) Dwayne Meadows

Explanation: Dwayne Meadows, NOAA/NMFS/OPR, is credited with the modification of the work related to Linckia multifora's asexual reproduction.

C) Mid-40s to mid-50s

Explanation: Menopause typically occurs in women between their mid-40s and mid-50s, marking the end of their reproductive years.

C) 8 weeks, 5 cm

Explanation: By eight weeks, the embryo is called a fetus and is about 5 cm (2 inches) long.

C) The outgrowth of a part of the body leading to a new individual

Explanation: Budding is a form of asexual reproduction where a part of the body grows out and eventually separates from the original organism, forming a new individual. This process results in two individuals, one smaller than the other.

C) External fertilization

Explanation: External fertilization occurs when both sperm and eggs are released into the environment, allowing fertilization to take place outside the bodies of the organisms.

C) Prostate gland

Explanation: The prostate gland is a part of the male reproductive system, whereas the ovaries, fallopian tubes, uterus, and cervix are parts of the female reproductive system.

B) Prevents bone loss from osteoporosis

Explanation: One of the primary benefits of Hormone Replacement Therapy (HRT) in menopause is the prevention of bone loss from osteoporosis, which helps maintain bone density and reduce the risk of fractures.

B) The hypothalamus

Explanation: At puberty, the hypothalamus triggers the release of FSH and LH in males, initiating the processes that lead to spermatogenesis and testosterone production.

C) They carry the young in a pouch until birth

Explanation: Unlike almost all other animals, male seahorses carry the young in a pouch until birth, making their reproductive role unique.

B) The fusion of an egg and sperm to form a zygote

Explanation: Fertilization is the process where an egg and sperm fuse to form a zygote, initiating the development of a new organism.

B) It grows into a new sea star

Explanation: In the process of asexual reproduction via fragmentation, an arm that has been shed by Linckia multifora grows into a new sea star.

C) It closes around the blastocyst through wound healing

Explanation: After the blastocyst integrates into the endometrium, the endometrium undergoes wound healing to close around the blastocyst, securing its position.

C) To combine genetic material from two parents

Explanation: Fertilization is the process by which the genetic material from two parents is combined to form a new organism, leading to genetic diversity in the offspring.

C) It results in genetically identical offspring

Explanation: Asexual reproduction results in offspring that are genetically identical to the parent, as there is no combination of genetic material from two individuals.

C) Carries sperm from the epididymis to the ejaculatory duct

Explanation: The vas deferens is responsible for transporting sperm from the epididymis to the ejaculatory duct, which is a crucial step in the process of ejaculation.

B) Beluga and sperm whales

Explanation: Among marine mammals, the beluga and sperm whales have the longest gestation periods, lasting 460 days.

B) They are hairless

Explanation: The labia minora are thin, hairless folds of tissue located centrally within the labia majora.

C) Follicle-stimulating hormone (FSH) and luteinizing hormone (LH)

Explanation: The anterior pituitary releases follicle-stimulating hormone (FSH) and luteinizing hormone (LH) into the bloodstream in response to gonadotropin-releasing hormone (GnRH) from the hypothalamus.

B) At the sides of the vaginal opening

Explanation: The greater vestibular glands are located at the sides of the vaginal opening.

C) Protecting and promoting sperm development

Explanation: Sertoli cells are involved in sperm development by protecting and promoting the growth of sperm cells.

B) A follicle ruptures, releasing an egg

Explanation: During ovulation, one of the follicles in the ovary ruptures, releasing an egg, which is essential for potential fertilization.

B) They produce eggs

Explanation: Female seahorses produce eggs, which are then fertilized by the male seahorse. This is a key aspect of their reproductive process.

B) In aquatic environments

Explanation: External fertilization occurs in aquatic environments where eggs and sperm are released into the water, allowing fertilization to happen when sperm reaches the egg in the water.

C) Asexual reproduction produces genetically identical offspring, while sexual reproduction produces genetically diverse offspring

Explanation: Asexual reproduction results in offspring that are genetically identical to the parent, whereas sexual reproduction involves the combination of genetic material from two parents, leading to genetic diversity.

B) The fusion of gametes

Explanation: Each gamete has one set of chromosomes, and their fusion during fertilization ensures that the offspring has a complete diploid set.

C) Environmental signals such as water temperature or length of daylight

Explanation: Spawning is often triggered by environmental signals, such as changes in water temperature or the length of daylight, which cue the organisms to release their eggs and sperm.

C) Estrogens and low levels of progesterone

Explanation: During the Follicular Phase, the follicles release estrogens and low levels of progesterone, which help prepare the endometrium for potential pregnancy.

A) 237 days

Explanation: Chimpanzee gestation lasts for 237 days, which is shorter than human gestation but similar to other great apes.

B) By cellular signaling cascades

Explanation: Differentiation is regulated by cellular signaling cascades, which are complex networks of signals that guide cells to express specific genes and become distinct cell types.

C) Removal of a section of the vas deferens

Explanation: A vasectomy involves removing a section of the vas deferens to prevent sperm release and fertilization, serving as a method of male contraception.

C) It produces genetically identical offspring

Explanation: Asexual reproduction produces genetically identical offspring because there is no exchange or recombination of genetic material, unlike in sexual reproduction.

B) It varies among individual species

Explanation: The details of asexual reproduction vary among individual species, indicating that different animals have evolved various methods to reproduce asexually.

C) Release of adrenal hormones

Explanation: The onset of puberty is marked by the release of adrenal hormones, which is necessary for the production of gonadotropin-releasing hormone (GnRH).

D) Fallopian tubes

Explanation: Fertilization typically occurs in the fallopian tubes, where the sperm meets and fertilizes the egg before it travels to the uterus for implantation.

B) A period during which men cannot achieve an erection or ejaculate

Explanation: Men experience a refractory period during the resolution phase, during which they cannot achieve an erection or ejaculate. This period can last from minutes to hours.

B) To produce milk

Explanation: The mammary glands, located in the breasts, are responsible for producing milk, which is essential for nourishing newborns.

C) It stimulates Sertoli cells to facilitate spermatogenesis

Explanation: FSH stimulates Sertoli cells in the testes to facilitate spermatogenesis using negative feedback, playing a crucial role in sperm production.

D) Metaphase II

Explanation: The secondary oocyte is arrested in metaphase II until ovulation.

C) Lophelia pertusa coral

Explanation: Lophelia pertusa coral, like the hydra, can reproduce through budding, where new polyps form and grow from the parent organism.

C) The process where embryonic stem cells express specific genes to become distinct cell types

Explanation: Differentiation is defined as the process where embryonic stem cells express specific genes to become distinct cell types, which is crucial for the development of various tissues and organs.

B) Fertilized eggs are laid outside the female's body

Explanation: In oviparity, fertilized eggs are laid outside the female's body, and development occurs externally with nourishment from the egg's yolk.

D) Accidental damage, predator damage, or natural reproductive processes

Explanation: Fragmentation can occur due to accidental damage, predator damage, or as a natural reproductive process.

C) Testis

Explanation: The testis is a key structure in the male reproductive system, responsible for producing sperm and male sex hormones.

C) It increases the chances of fertilization by releasing large quantities of eggs and sperm

Explanation: External fertilization is advantageous in aquatic environments because releasing large quantities of eggs and sperm increases the chances of successful fertilization.

C) Fruit Flies (Drosophila)

Explanation: Fruit Flies (Drosophila) are used as model organisms to study segmental patterning and gene roles in organogenesis, providing valuable insights into developmental biology.

B) Provide lubrication during intercourse

Explanation: The greater vestibular glands are located at the sides of the vaginal opening and provide lubrication during intercourse.

B) Yes, but they are not stimulated to produce viable eggs

Explanation: During menopause, the ovaries still contain eggs and potential follicles, but they are not stimulated to produce viable eggs due to the loss of sensitivity to FSH and LH.

C) The new individual is smaller

Explanation: In budding, the new individual formed is typically smaller than the original organism from which it separated.

B) It sloughs off

Explanation: During menstruation, the endometrial lining of the uterus sloughs off and is expelled from the body, and then it rebuilds itself for potential implantation in the next cycle.

C) Urethra

Explanation: During ejaculation, semen is expelled through the urethra, which is the same tube that carries urine out of the body.

B) Corpus cavernosum and corpus spongiosum

Explanation: The penis contains three tubes of erectile tissue, specifically the corpus cavernosum and corpus spongiosum, which engorge with blood during an erection.

C) By fragmentation

Explanation: Linckia multifora reproduces asexually through fragmentation, where an arm that has been shed grows into a new sea star.

B) Colon cancer

Explanation: Hormone Replacement Therapy (HRT) in menopause is thought to protect against colon cancer, along with heart disease, macular degeneration, and possibly depression.

C) They undergo the second meiotic division to form spermatids

Explanation: Secondary spermatocytes undergo the second meiotic division to form spermatids, which will eventually mature into sperm cells.

B) Stores and matures sperm

Explanation: The epididymis is a comma-shaped structure on the top and back of the testes where sperm mature, making it essential for the development of functional sperm.

D) Deepening of voice

Explanation: Estrogen is responsible for secondary sexual characteristics such as breast development, flaring of hips, and shorter bone maturation period, but not for deepening of the voice.

C) Some bony fish, reptiles, cartilaginous fish, amphibians, mammals (like platypus and echidna), and all birds

Explanation: Oviparity is seen in a variety of animals including some bony fish, reptiles, cartilaginous fish, amphibians, certain mammals like the platypus and echidna, and all birds.

B) Paired chromosomes are separated

Explanation: During the first cell division in meiosis, paired chromosomes are separated, which is a critical step in reducing the chromosome number by half.

A) A broken arm and a piece of the central disc

Explanation: In some sea stars, a new individual can regenerate from a broken arm and a piece of the central disc.

B) Due to their consistent cell patterns and ability to track cell lineage

Explanation: Nematodes (Caenorhabditis elegans) are used as model organisms in developmental studies because of their consistent cell patterns and the ability to track cell lineage, making them ideal for understanding development.

C) Bacteria

Explanation: Bacteria are prokaryotic microorganisms that reproduce asexually, typically through binary fission, a process where a single cell divides into two identical cells.

B) Follicle-stimulating hormone (FSH) and luteinizing hormone (LH)

Explanation: Follicle-stimulating hormone (FSH) and luteinizing hormone (LH), although named for their roles in female reproduction, are crucial in both sexes for controlling reproductive functions.

B) Labia

Explanation: The tissue that will become the scrotum in a male becomes the labia in a female, making them homologous structures.

B) To aid in childbirth

Explanation: The thick wall of the uterus is composed of smooth muscle, which plays a crucial role in aiding childbirth by contracting to help deliver the baby.

B) Clitoris

Explanation: The clitoris is a structure within the vulva that contains erectile tissue and sensory nerves, providing stimulation during intercourse.

C) Fertilization of an egg

Explanation: Pregnancy begins with the fertilization of an egg, which is the initial step in the development of a new individual.

C) The production of sperm and eggs through meiosis

Explanation: Gametogenesis is defined as the production of sperm and eggs through the process of meiosis, which is essential for sexual reproduction.

D) Uterus

Explanation: The uterus is an internal reproductive organ, whereas the vulva comprises external structures such as the clitoris, mons pubis, labia majora, and labia minora.

D) Sexual reproduction

Explanation: Sexual reproduction is not a method of asexual reproduction. Fragmentation, budding, binary fission, and parthenogenesis are all methods of asexual reproduction.

D) Four

Explanation: Each primary spermatocyte undergoes meiosis to produce four sperm cells, highlighting the efficiency of the spermatogenesis process.

B) To create an environment that prevents egg implantation

Explanation: An intrauterine device (IUD) is inserted into the uterus to create an environment that prevents the implantation of a fertilized egg, thereby acting as a contraceptive.

B) It involves the fusion of gametes

Explanation: Asexual reproduction does not involve the fusion of gametes, which is a characteristic of sexual reproduction. Instead, it occurs without the need for a mate.

C) Sperm is left in the environment for the female to collect

Explanation: In environmental fertilization, sperm is left in the environment, and the female collects it for fertilization.

C) The female deposits eggs into the male's brood pouch

Explanation: In seahorses, the female deposits eggs into the male's brood pouch, and the male releases sperm into the water. The sperm then find their way into the pouch to fertilize the eggs.

B) To produce sperm and reproductive hormones

Explanation: The testes are responsible for producing sperm and reproductive hormones, playing a crucial role in male fertility.

B) When females are isolated from males

Explanation: Parthenogenesis may occur in some species when females are isolated from males, as observed in Komodo dragons, hammerhead sharks, and blacktip sharks.

B) They regenerate missing parts after splitting

Explanation: A common characteristic of organisms that reproduce by fission is their ability to regenerate any missing parts after splitting into two parts.

B) It engorges with blood

Explanation: During an erection, the three tubes of erectile tissue in the penis (corpus cavernosum and corpus spongiosum) engorge with blood, causing the penis to become erect.

B) Through budding

Explanation: Hydra reproduce asexually through a process called budding, where a bud forms on the tubular body of an adult hydra, develops a mouth and tentacles, and then detaches to become a fully developed new hydra.

B) The portion of the uterus that protrudes into the vagina and serves as the birth canal

Explanation: The cervix is the part of the uterus that extends into the vagina and functions as the birth canal during childbirth.

C) Human beta chorionic gonadotropin (β-HCG)

Explanation: The chorion releases human beta chorionic gonadotropin (β-HCG), which is essential for maintaining the corpus luteum and ensuring continued progesterone production during pregnancy.

C) 266 days

Explanation: Human gestation lasts for approximately 266 days, which is similar to the gestation periods of other great apes.

C) The male seahorse

Explanation: In seahorses, the male seahorse fertilizes the eggs produced by the female, which is a unique aspect of their reproductive behavior.

C) Implants and sterilization methods

Explanation: Implants and sterilization methods, such as vasectomy and tubal ligation, are highly reliable contraceptive methods with failure rates of less than 1%.

C) Fertilization happens inside the female's body

Explanation: External fertilization does not involve fertilization inside the female's body; instead, it occurs in the water where eggs and sperm are released and meet.

B) 5 weeks

Explanation: By five weeks into the first trimester, the embryo has developed limb buds, eyes, heart, and liver.

C) Cleavage

Explanation: The blastula forms during the cleavage stage of embryonic development, which involves rapid cell division without growth, resulting in a hollow ball of cells.

B) Chromatids are separated

Explanation: During the second cell division in meiosis, chromatids are separated, which ensures that each haploid cell receives a single set of chromosomes.

B) They become less frequent and cease

Explanation: Menstrual periods become less frequent and eventually cease during menopause, marking the end of a woman's reproductive cycle.

B) It develops into an adult and breaks away from the main body

Explanation: In hydras, a bud forms that develops into an adult and eventually breaks away from the main body, resulting in a new individual.

B) To produce eggs and hormones

Explanation: The primary function of the ovaries is to produce eggs (ova) and hormones such as estrogen and progesterone, which are essential for reproduction and the menstrual cycle.

B) The mechanism that determines which sex an individual develops into

Explanation: Sex determination is the mechanism that determines which sex an individual will develop into, and this mechanism can vary among different species.

D) Produces identical offspring

Explanation: Sexual reproduction does not produce identical offspring; it results in genetically unique offspring due to the combination of gametes from two individuals.

C) Spermatogonia

Explanation: Spermatogonia are the diploid stem cells located at the periphery of the seminiferous tubules that undergo mitosis to initiate spermatogenesis.

B) A round, fatty area overlying the pubic symphysis

Explanation: The mons pubis is a round, fatty area that lies over the pubic symphysis, providing cushioning and protection.

B) To produce eggs and hormones

Explanation: The ovaries are responsible for producing eggs (ova) and hormones such as estrogen and progesterone, which are crucial for the reproductive cycle.

B) Developing follicles

Explanation: Estrogens and progesterone are released from developing follicles in the ovaries.

B) 46

Explanation: A fertilized egg has 46 chromosomes, with 23 chromosomes contributed by each parent.

D) She transfers the eggs to the male's pouch

Explanation: After producing eggs, the female seahorse transfers them to the male's pouch, where they are fertilized and develop until birth.

B) A spike in LH and FSH

Explanation: High estrogen levels cause a spike in LH and FSH, which triggers ovulation by causing the most mature follicle to rupture and release its egg.

C) To break down the zona pellucida

Explanation: Enzymes in the acrosome break down the zona pellucida, allowing the sperm to fuse with the egg membrane during fertilization.

B) They lose sensitivity to FSH and LH

Explanation: During menopause, the ovaries lose their sensitivity to the hormones FSH (Follicle Stimulating Hormone) and LH (Luteinizing Hormone), which leads to the cessation of menstrual periods.

C) To house the testes and maintain a lower temperature for sperm viability

Explanation: The scrotum houses the testes and keeps them external to maintain a temperature about 2°C lower than body temperature, which is crucial for sperm viability.

B) Haploid males (drones) and diploid females (workers and queens)

Explanation: In ants, bees, and wasps, parthenogenesis produces haploid males (drones), while diploid females (workers and queens) result from fertilized eggs.

B) Producing testosterone

Explanation: Leydig cells are responsible for producing testosterone, a key hormone in male reproductive health.

D) Involvement of sexual gametes

Explanation: Budding is a form of asexual reproduction and does not involve sexual gametes. It involves the formation of a new individual from an outgrowth of the original organism.

D) Menstruation

Explanation: Menstruation is the phase of the menstrual cycle that involves the shedding of the uterine lining, which occurs if fertilization does not take place.

B) Spermatogenesis

Explanation: Spermatogenesis is the process of sperm production that occurs in the testes, involving the division and maturation of spermatogonia into mature sperm cells.

C) Uterus

Explanation: The uterus is the site of implantation for a fertilized egg, where it can develop into an embryo and eventually a fetus during pregnancy.

B) To produce sperm and testosterone

Explanation: The primary function of the testes is to produce sperm and the hormone testosterone, which are essential for male fertility and the development of male secondary sexual characteristics.

B) The splitting of an organism into two parts

Explanation: Fission, or binary fission, involves an organism splitting into two parts and regenerating any missing parts, which is a form of asexual reproduction.

B) Planarians

Explanation: Planarians, such as Dugesia dorotocephala, are known to undergo fission by separating into head and tail regions, each regenerating the missing half.

A) By dividing along the oral-aboral axis

Explanation: Sea anemones, such as Anthopleura species, undergo fission by dividing along the oral-aboral axis and regenerating the missing parts.

C) Sea cucumbers

Explanation: Sea cucumbers, such as Holothuria species, divide across the oral-aboral axis and regenerate the missing halves during fission.

B) Concurrently

Explanation: The ovarian and menstrual cycles occur concurrently, meaning they happen at the same time over the course of the cycle period.

B) In the seminiferous tubules of the testes

Explanation: Spermatogenesis occurs specifically in the seminiferous tubules of the testes, which are the site of sperm production.

B) FSH and LH

Explanation: The anterior pituitary releases Follicle Stimulating Hormone (FSH) and Luteinizing Hormone (LH) to regulate female reproductive functions.

C) It stimulates interstitial cells of Leydig to produce testosterone

Explanation: LH stimulates the interstitial cells of Leydig in the testes to produce and release testosterone, which is essential for male secondary sexual characteristics.

B) It completes meiosis II

Explanation: If fertilized, the secondary oocyte completes meiosis II, forming a second polar body and a fertilized egg with 46 chromosomes.

B) African elephant

Explanation: The African elephant has the longest gestation period among land mammals, lasting 640 days.

B) In the inguinal (groin) area

Explanation: The vulva is located in the inguinal (groin) area and comprises several external structures of the female reproductive system.

B) Produces haploid cells with half the chromosome number

Explanation: The outcome of meiosis is the production of haploid cells, which have half the chromosome number of diploid cells, ensuring genetic diversity in sexual reproduction.

C) At adolescence

Explanation: Spermatogonia are inactive until adolescence, when gonadotropic hormones activate them, initiating the process of spermatogenesis.

B) Through the egg's yolk

Explanation: In oviparous animals, the developing embryos are nourished by the yolk present in the egg.

C) Mixture of sperm and secretions from spermatic ducts and accessory glands

Explanation: Semen is a mixture of sperm and secretions from spermatic ducts and accessory glands, which together facilitate the transport and nourishment of sperm.

C) Contains enzymes to penetrate the egg

Explanation: The acrosome in the sperm head contains enzymes that are essential for penetrating the egg, allowing fertilization to occur.

B) Inability to have children

Explanation: A significant result of menopause is the inability to have children, as the ovaries no longer produce viable eggs.

C) Testosterone

Explanation: Testosterone is the primary hormone responsible for the development of male secondary sexual characteristics, such as facial hair, deepening of the voice, and increased muscle mass.