A hydra forms a small outgrowth on its body that develops into a new individual and then detaches. Which type of asexual reproduction is this?
Budding
✓
Fission
Fragmentation
Parthenogenesis
Correct Answer
Budding
In budding, a new individual grows as an outgrowth of the parent and breaks away once it is developed, as in hydras and corals. Fission is the splitting of the body into two parts that each regenerate the missing half. Fragmentation is the breaking of the body into pieces that each regrow into a whole animal. Parthenogenesis is development of an offspring from an unfertilized egg.
Category: Asexual Reproduction
Question 2
Some sea stars can regrow a complete body from a detached arm that includes part of the central disc. Which type of asexual reproduction does this show?
Budding
Fragmentation
✓
Parthenogenesis
Spawning
Correct Answer
Fragmentation
Fragmentation occurs when an animal's body breaks into pieces and each large enough piece regenerates into a full individual, as in sea stars, sponges and some annelids. Budding produces a new individual as an outgrowth of an intact parent. Parthenogenesis is the development of an unfertilized egg. Spawning is the release of eggs and sperm into water during sexual reproduction.
Category: Asexual Reproduction
Question 3
In honeybees, what kind of individual develops from an egg that is never fertilized?
A diploid female
A haploid female
A haploid male
✓
A diploid male
Correct Answer
A haploid male
In bees, ants and wasps, unfertilized eggs develop by parthenogenesis into males with one set of chromosomes, while fertilized eggs become females. A diploid female comes from a fertilized egg, not an unfertilized one. A haploid female does not arise in this system, because haploid bees are male. A diploid male is not the normal product of an unfertilized egg, which carries only the mother's single chromosome set.
Category: Asexual Reproduction
Question 4
In birds, which pair of sex chromosomes produces a female?
ZZ
XX
XY
ZW
✓
Correct Answer
ZW
Birds use the ZW system, in which the female carries two different sex chromosomes and the male carries two of the same. ZZ is the combination found in male birds. XX is the female combination in the mammalian XY system, not in birds. XY is the male combination in mammals.
Category: Sex Determination
Question 5
In alligators and many turtles, what determines whether an embryo develops as male or female?
The incubation temperature of the egg
✓
The sex chromosome carried by the sperm
The day length during mating
The number of eggs in the clutch
Correct Answer
The incubation temperature of the egg
These reptiles show temperature-dependent sex determination: the temperature during the middle part of egg development sets the sex of the embryo. The sex chromosome carried by the sperm determines sex in mammals, not alligators. The day length during mating can cue breeding in some animals but does not set offspring sex. The number of eggs in the clutch has no role in deciding sex.
Category: Sex Determination
Question 6
Earthworms have both male and female reproductive systems at the same time in one individual. What is this condition called?
Parthenogenesis
Hermaphroditism
✓
Protandry
Viviparity
Correct Answer
Hermaphroditism
Hermaphroditism is the presence of both male and female reproductive systems in one animal, seen in earthworms, snails, slugs and tapeworms. Parthenogenesis is development from an unfertilized egg. Protandry is a change from male to female over an animal's lifetime, not having both systems at once. Viviparity is giving birth to live young that developed inside the mother.
Category: Sex Determination
Question 7
Oysters begin life as males and later change to females that lay eggs. What is this pattern of sex change called?
Protogyny
Budding
Protandry
✓
Fragmentation
Correct Answer
Protandry
Protandry, meaning first male, describes animals that are born male and later become female. Protogyny is the reverse pattern, in which an animal starts as female and later becomes male. Budding is a form of asexual reproduction, not a change of sex. Fragmentation is also asexual reproduction, in which body pieces regrow into new individuals.
Category: Sex Determination
Question 8
Which of these animals typically reproduces by external fertilization, with eggs and sperm meeting in the water?
Birds
Mammals
Reptiles
Frogs
✓
Correct Answer
Frogs
Most frogs release eggs and sperm into water, where fertilization takes place outside the body, as do most fish, corals and many other aquatic animals. Birds use internal fertilization and lay shelled eggs. Mammals use internal fertilization. Reptiles also fertilize internally, which suits their life on land.
Category: Fertilization and Development Modes
Question 9
In which mode of development do the young grow inside the mother's body, receive nourishment from her and are born alive?
Viviparity
✓
Oviparity
Ovoviviparity
Parthenogenesis
Correct Answer
Viviparity
In viviparity, offspring develop within the mother and are fed by her, through a placenta in most mammals, before a live birth. Oviparity means fertilized eggs are laid and develop outside the body on yolk. Ovoviviparity means eggs stay inside the mother until hatching but the embryos are nourished mainly by yolk. Parthenogenesis is development from an unfertilized egg, not a mode of nourishment.
Category: Fertilization and Development Modes
Question 10
During fertilization, enzymes released from which structure at the tip of the sperm head help the sperm penetrate the egg's protective layers?
Flagellum
Acrosome
✓
Mitochondrion
Centriole
Correct Answer
Acrosome
The acrosome is a lysosome-like cap on the sperm head whose enzymes digest a path through the coverings around the egg, allowing the sperm and egg membranes to fuse. Flagellum is the tail that moves the sperm, not a source of digestive enzymes. Mitochondrion refers to the organelles in the sperm's midpiece that supply energy for swimming. Centriole is involved in organizing microtubules and does not release enzymes.
Category: Embryonic Development
Question 11
Why is it important that only one sperm fuses with an egg?
So the egg can begin meiosis I
So the zygote remains haploid
So the zygote receives exactly the diploid number of chromosomes
✓
So the sperm's mitochondria are destroyed
Correct Answer
So the zygote receives exactly the diploid number of chromosomes
One haploid sperm plus one haploid egg gives a zygote with exactly two chromosome sets, the diploid number; extra sperm would add extra chromosome sets. So the egg can begin meiosis I is wrong because the egg's meiosis is already underway before fertilization. So the zygote remains haploid is wrong because the zygote is diploid. So the sperm's mitochondria are destroyed is unrelated to blocking extra sperm.
Category: Embryonic Development
Question 12
During cleavage, the zygote divides rapidly into many cells. What happens to the overall size of the embryo during this stage?
It doubles with each division
It shrinks by half with each division
It grows about tenfold
It stays about the same as cell number rises
✓
Correct Answer
It stays about the same as cell number rises
Cleavage divisions split the existing cytoplasm into more and smaller cells without the embryo growing, so its overall size stays about the same. It doubles with each division is wrong because the cells do not grow between divisions. It shrinks by half with each division confuses the size of each cell with the size of the whole embryo. It grows about tenfold is wrong because no significant growth happens during cleavage.
Category: Embryonic Development
Question 13
In a mammalian blastocyst, which part goes on to form the embryo itself?
Inner cell mass
✓
Trophoblast
Blastocoel
Zona pellucida
Correct Answer
Inner cell mass
The inner cell mass is the cluster of cells inside the blastocyst that develops into the embryo. Trophoblast is the outer layer that helps the blastocyst implant and contributes to the placenta. Blastocoel is the fluid-filled cavity, not a group of cells. Zona pellucida is the protective coat around the egg, not part of the embryo.
Category: Embryonic Development
Question 14
Which germ layer gives rise to the nervous system and the epidermis of the skin?
Mesoderm
Ectoderm
✓
Endoderm
Trophoblast
Correct Answer
Ectoderm
The ectoderm is the outer germ layer of the gastrula and forms the nervous system and the epidermis. Mesoderm is the middle layer that forms muscle and connective tissue. Endoderm is the inner layer that forms the lining of the gut and many internal organs. Trophoblast is the outer layer of the blastocyst that contributes to the placenta, not a germ layer.
Category: Embryonic Development
Question 15
Which developmental process rearranges the cells of the blastula into three distinct layers?
Cleavage
Organogenesis
Gastrulation
✓
Implantation
Correct Answer
Gastrulation
In gastrulation, the blastula folds inward and cells migrate to form the three germ layers of the gastrula. Cleavage is the earlier series of rapid divisions that produces the blastula. Organogenesis comes after gastrulation, when the germ layers form organs. Implantation is the attachment of the mammalian blastocyst to the uterine wall.
Category: Embryonic Development
Question 16
After sperm are produced in the seminiferous tubules, in which structure do they mature?
Vas deferens
Prostate gland
Urethra
Epididymis
✓
Correct Answer
Epididymis
Sperm move from the seminiferous tubules into the coiled epididymis, where they mature and become able to swim. Vas deferens is the duct that carries mature sperm onward toward the ejaculatory duct. Prostate gland is an accessory gland that adds fluid to semen. Urethra is the final tube that carries semen and urine out of the body.
Category: Male Reproductive System
Question 17
Which cells in the testes, located between the seminiferous tubules, produce testosterone?
Leydig cells
✓
Sertoli cells
Spermatogonia
Granulosa cells
Correct Answer
Leydig cells
Leydig cells, also called interstitial cells, lie between the seminiferous tubules and make testosterone in response to LH. Sertoli cells respond to FSH, nourish developing sperm and secrete inhibin. Spermatogonia are the stem cells that give rise to sperm. Granulosa cells are found in ovarian follicles, not in the testes.
Category: Male Reproductive System
Question 18
When one primary spermatocyte completes both divisions of meiosis, how many sperm cells result?
Two
Four
✓
One
Eight
Correct Answer
Four
Meiosis I and II together turn one primary spermatocyte into four haploid cells, and all four become sperm. Two is the number of cells after meiosis I alone. One is the number of eggs a primary oocyte yields in oogenesis, along with polar bodies. Eight would require an additional division that does not occur.
Category: Male Reproductive System
Question 19
A sharp surge of which hormone causes the most mature ovarian follicle to rupture and release its egg?
Follicle-stimulating hormone
Progesterone
Luteinizing hormone
✓
Oxytocin
Correct Answer
Luteinizing hormone
Rising estrogen triggers a spike in luteinizing hormone from the anterior pituitary, and this LH surge causes the mature follicle to rupture at ovulation. Follicle-stimulating hormone also rises briefly but mainly stimulates follicle growth earlier in the cycle. Progesterone is made by the corpus luteum after ovulation and suppresses FSH and LH. Oxytocin stimulates uterine contractions during labor.
Category: Female Cycles and Hormones
Question 20
Which hormone, detected by home pregnancy tests, keeps the corpus luteum making progesterone during early pregnancy?
Oxytocin
Prolactin
Testosterone
Human chorionic gonadotropin
✓
Correct Answer
Human chorionic gonadotropin
Human chorionic gonadotropin is secreted by the chorion of the early embryo and keeps the corpus luteum active, so progesterone continues to maintain the uterine lining. Oxytocin triggers uterine contractions during birth. Prolactin stimulates milk production after birth. Testosterone is the main male sex hormone and does not maintain pregnancy.
Category: Female Cycles and Hormones