Asexual reproduction by budding or fragmentation produces offspring that are genetically identical to their single parent.
Correct Answer
True
True. Budding and fragmentation add no genetic material from a second parent, so the offspring carry the same genes as the parent, which lets one individual produce many young quickly.
Category: Asexual Reproduction
Question 2
Asexual reproduction is especially advantageous in rapidly changing, unpredictable environments.
Correct Answer
False
False. Asexual reproduction works best in stable, predictable environments. In changing environments, the genetic variation produced by sexual reproduction makes it more likely that some offspring will be suited to new conditions.
Category: Asexual Reproduction
Question 3
Hermaphroditic animals such as earthworms usually mate with another individual rather than fertilizing their own eggs.
Correct Answer
True
True. Although self-fertilization is possible in some hermaphrodites, they usually mate with a partner, and many species have mechanisms that prevent self-fertilization because it is extreme inbreeding.
Category: Sex Determination
Question 4
In mammals, an individual with two X chromosomes develops as a male.
Correct Answer
False
False. In the mammalian XY system, an XX individual develops as a female, and an XY individual develops as a male because genes on the Y chromosome trigger male development.
Category: Sex Determination
Question 5
In wrasses, a reef fish, the largest female can change sex and take over the role of a dominant male that dies.
Correct Answer
True
True. Wrasses are sequential hermaphrodites. When the dominant male is lost, the largest female changes into a male, an example of protogyny, which means female first.
Category: Sex Determination
Question 6
External fertilization is the most common form of fertilization among land animals.
Correct Answer
False
False. External fertilization usually happens in water, where eggs and sperm can meet without drying out. Internal fertilization is the most common form among land animals.
Category: Fertilization and Development Modes
Question 7
Birds are oviparous, laying fertilized eggs that develop outside the mother's body.
Correct Answer
True
True. In oviparity, eggs are laid after internal fertilization and the embryo develops outside the mother, nourished by the yolk. Birds, most reptiles and insects, and a few mammals such as the platypus reproduce this way.
Category: Fertilization and Development Modes
Question 8
In ovoviviparous animals, embryos retained inside the mother are nourished mainly through a placenta.
Correct Answer
False
False. In ovoviviparity, eggs stay inside the mother until they hatch, but the embryos are nourished mainly by the egg yolk. Nourishment through a placenta is a feature of viviparity in mammals.
Category: Fertilization and Development Modes
Question 9
The trophoblast of a mammalian blastocyst secretes enzymes that allow it to implant in the uterine lining.
Correct Answer
True
True. The trophoblast is the outer cell layer of the blastocyst. Its enzymes let the blastocyst embed in the uterine wall, and it later contributes to the placenta that nourishes the embryo.
Category: Embryonic Development
Question 10
The endoderm is the germ layer that forms the body's muscles and connective tissue.
Correct Answer
False
False. Muscle and connective tissue come from the mesoderm, the middle germ layer. The endoderm, the inner layer, forms the lining of the digestive tract and many internal organs.
Category: Embryonic Development
Question 11
During organogenesis, embryonic cells differentiate by expressing different sets of genes in response to chemical signals from their location.
Correct Answer
True
True. Location-specific chemical signals turn on cascades of gene expression, so cells in different places become different cell types, such as ectoderm cells that become epidermal cells.
Category: Embryonic Development
Question 12
During cleavage, the zygote divides rapidly by meiosis to produce many cells.
Correct Answer
False
False. Cleavage divisions are mitotic, so every cell of the early embryo keeps the full diploid set of chromosomes. Meiosis happens only when gametes are produced.
Category: Embryonic Development
Question 13
The scrotum holds the testes outside the body cavity, keeping them slightly cooler than core body temperature, which favors sperm production.
Correct Answer
True
True. Sperm develop best at a temperature a little below core body temperature. Testes that fail to descend into the scrotum stay too warm, and fertility is reduced.
Category: Male Reproductive System
Question 14
Sperm cells make up most of the volume of semen.
Correct Answer
False
False. Sperm make up only a few percent of semen. Most of the volume comes from the seminal vesicles, prostate gland and bulbourethral glands, which add nutrients, buffers and other substances.
Category: Male Reproductive System
Question 15
Primary oocytes form before a female is born and remain paused in prophase of meiosis I until puberty or later.
Correct Answer
True
True. Oogonia produce primary oocytes during embryonic development, and these stay arrested in prophase I. Beginning at puberty, about one per cycle resumes meiosis.
Category: Female Cycles and Hormones
Question 16
A human secondary oocyte completes meiosis II at ovulation, whether or not it is fertilized.
Correct Answer
False
False. The secondary oocyte is arrested in metaphase II and completes meiosis II only if a sperm fertilizes it. An unfertilized oocyte never finishes the second division.
Category: Female Cycles and Hormones
Question 17
Estrogen is responsible for female secondary sex characteristics such as breast development and widening of the hips.
Correct Answer
True
True. Estrogen, made by developing ovarian follicles, drives the body changes of female puberty, including breast development, wider hips and changes in bone growth.
Category: Female Cycles and Hormones
Question 18
In humans, fertilization usually takes place in the uterus.
Correct Answer
False
False. Fertilization usually occurs in the oviduct, also called the fallopian tube. The resulting embryo then travels to the uterus, where it implants.
Category: Female Cycles and Hormones
Question 19
Oxytocin release during labor is a positive feedback loop, because uterine contractions lead to the release of more oxytocin.
Correct Answer
True
True. Stretching of the cervix signals the hypothalamus to trigger oxytocin release from the posterior pituitary, oxytocin strengthens contractions, and stronger contractions bring more oxytocin until the baby is born.
Category: Pregnancy and Birth
Question 20
In males, testosterone and inhibin stimulate the hypothalamus and pituitary to release more GnRH, FSH and LH.
Correct Answer
False
False. Testosterone and inhibin act by negative feedback, suppressing release of GnRH, FSH and LH so that hormone levels and sperm production stay in a normal range.
Category: Male Reproductive System