Question 1

Which of the following describes the way in which monozygotic twins occur?

Accepted Answer

Monozygotic twins are formed when a single fertilized egg (zygote) splits into two separate embryos. This occurs randomly and is not influenced by genetics or environmental factors. Therefore, it is an example of a spontaneous mutation.

Question 2

Emily and her husband are thrilled as they peer into Emily's uterus by means of an ultrasound. The physician reports that the pregnancy appears normal, and that their baby's fingers, toes, heart, and circulatory system are developing as expected. The couple learns that the baby is only an inch long. Given this information, the current stage of prenatal development is the ________.

Accepted Answer

The embryonic period is the stage of prenatal development that occurs from fertilization to about 8 weeks of gestation. At this stage, the major organs and systems of the body are forming, and the embryo is most vulnerable to teratogens (agents that can cause birth defects). At an inch long, the baby described in the scenario is likely around 6-7 weeks gestational age, which falls within the embryonic period. The germinal period refers to the first two weeks of gestation, while the zygotic period is not a recognized stage of prenatal development. The fetal stage occurs from about 9 weeks until birth.

Question 3

The germinal period ________.

Accepted Answer

The germinal period occurs during the first two weeks after fertilization, when the zygote undergoes rapid cell division and becomes implanted in the uterine wall.

Question 4

Ashley and Mary-Kate are twins who are genetically identical. What type of twins are they?

Accepted Answer

Ashley and Mary-Kate being genetically identical indicates that they were formed from a single fertilized egg that split into two, making them monozygotic twins.

Question 5

Which of the following terms is used to describe any substance, such as a drug, chemical, or virus that can bring about a birth defect?

Accepted Answer

A teratogen is any substance or agent that can cause or increase the likelihood of a birth defect or malformation in the developing embryo or fetus. Examples of teratogens include certain drugs, chemicals, viruses, and environmental factors such as radiation or pollution. It is important to note that the effect of a teratogen on a developing fetus depends on the timing, duration, and intensity of exposure.

Question 6

The specialized organ that provides nourishment and filters away waste products from the developing baby is called the ________.

Accepted Answer

The placenta is the specialized organ that develops during pregnancy and provides nourishment to the developing baby. It also filters away waste products from the baby's bloodstream. The uterus is the organ in which the baby grows and develops during pregnancy. The umbilical cord is the cord that connects the baby to the placenta, allowing for the exchange of nutrients, oxygen, and waste products. The embryo is the early stage of development before it becomes a fetus.

Question 7

Monozygotic twins ________.

Accepted Answer

Monozygotic (identical) twins come from a single fertilized egg and therefore have the same genetic makeup.

Question 8

Times during which some environmental influences can have a major impact on development are called ________.

Accepted Answer

Critical periods are times during development when certain environmental influences can have a major impact on the development of a particular characteristic. These periods are often specific to certain developmental processes and may vary depending on the individual. Fetal periods refer specifically to the time during prenatal development when the fetus is developing, while germinal periods are the very early stages of prenatal development. Latency periods refer to a period of relatively little change during middle childhood. Therefore, the best choice is B, critical periods.

Question 9

The union of the ovum and sperm is called ________.

Accepted Answer

Fertilization is the process of the union of the ovum and sperm, resulting in the formation of a zygote. The zygote is the first stage of development that leads to the formation of an embryo, which then grows and develops into a fetus. Therefore, option A, fertilization, is the correct answer. Option B, the fetal period, refers to a later stage in prenatal development, after the embryonic period, when the developing organism is referred to as a fetus. Option C, a zygote, is the result of fertilization and the earliest stage of development. Option D, an embryo, is the stage of development after the zygote and before the fetal period.

Question 10

Tameeka is at a point in her pregnancy during which the major organs and structures of her baby are first developing. Which period of prenatal development is Tameeka currently experiencing?

Accepted Answer

The embryonic period is the stage of prenatal development from approximately the second week after fertilization until the eighth week. During this time, the major organs and structures of the embryo begin to form.

Question 11

Which of the following describes the embryonic period?

Accepted Answer

The embryonic period is the period during which the major organs and structures of the organism first develop. This period lasts from implantation (around week 2) through the end of the 8th week of pregnancy. During this time, the embryo is very susceptible to environmental factors that can affect development.

Question 12

________ develop when two eggs each get fertilized by different sperm cells, resulting in two zygotes in the uterus at the same time.

Accepted Answer

Dizygotic (or fraternal) twins develop when two separate eggs are fertilized by two different sperm, resulting in two zygotes (embryos) growing in the uterus at the same time. This is in contrast to monozygotic (identical) twins, which develop from a single fertilized egg that splits into two embryos. Wombmates and fraternal twins are colloquial terms and not commonly used in scientific literature.

Question 13

In the process of fertilization, the ________ and ________ unite, resulting in a single cell.

Accepted Answer

Fertilization occurs when a sperm (male gamete) and an ovum (female gamete) unite to form a zygote, a single cell that contains genetic material from both the mother and father. Therefore, option A is the correct choice. Option B is incorrect because a zygote is formed only after fertilization. Option C is incorrect because an embryo is formed after the fertilized egg undergoes several cell divisions, and a fetus is formed later in the pregnancy stage. Option D is also incorrect because a fetus is formed after several stages of development, which come after fertilization.

Question 14

The study of ethical and moral issues brought about by new advances in biology and medicine is called ________.

Accepted Answer

Bioethics is the study of ethical and moral issues raised by new advances in biology and medicine. Germinal staging refers to the early stages of embryo development. Axiology is the philosophical study of values. Twenty-first century moral standards may be relevant to bioethics, but do not describe the field itself.

Question 15

Fraternal twins are ________ similar genetically than are regular, non-twin siblings.

Accepted Answer

Fraternal twins are genetically similar to regular siblings because they come from two separate eggs fertilized by two separate sperm, sharing about 50% of their DNA, just like any other siblings.

Question 16

Which kind of cells that form during the germinal period are being examined by researchers for their use for growing new organs and tissue for transplant or to repair neurological damage?

Accepted Answer

Stem cells are the kind of cells that form during the germinal period and are being examined by researchers for their use in growing new organs and tissue for transplant or repairing neurological damage. Stem cells are unique in their ability to differentiate into a variety of different cell types and have the potential to be used in regenerative medicine.

Question 17

The placenta is ________.

Accepted Answer

The placenta is a specialized organ that develops during pregnancy and provides nourishment and filters away waste products from the developing baby. It is not a tube nor the technical name for the "belly button" and it is not the name for the developing organism until it is 8 weeks old.

Question 18

Mary and Juan are twins who developed from two separate fertilized ova that were fertilized by two different sperm. What type of twins are they?

Accepted Answer

Mary and Juan are dizygotic or fraternal twins because they developed from two separate fertilized ova, each fertilized by a different sperm. Monozygotic or identical twins come from a single fertilized egg that splits into two embryos, whereas maternal twins is not a recognized category of twin classification. "Wombmates" is not a scientific term used to describe twins.

Question 19

Marisa is at a point in her pregnancy when the zygote is moving down to her uterus, and the placenta and umbilical cord are beginning to form. Which period of prenatal development is Marisa currently experiencing?

Accepted Answer

The germinal period is the first stage of prenatal development, lasting from conception to about two weeks, during which the zygote moves to the uterus and the placenta and umbilical cord begin to form.

Question 20

Ovum is a term used to describe ________.

Accepted Answer

An ovum is the female sex cell, or egg. It is released from the ovary during ovulation and can potentially be fertilized by a sperm to create a zygote, which then grows and develops into an embryo. Options B, C, and D refer to other stages of development and are not accurate descriptions of an ovum.

Quiz 8: Development Across the Life Span