Question 1

During the rapid cell division that occurs after fertilization, cells increase rapidly in number, but the embryo stays the same size. The cells of this very early embryo must

Accepted Answer

The cells of the early embryo undergo a very short interphase, allowing for rapid cell division without an increase in overall size. This allows for the formation of a larger embryo later on during development. Choices A, B, and D are not relevant or accurate to describe the process of early embryo development.

Question 2

The human embryo develops in a fluid-filled sac, called the

Accepted Answer

The fluid-filled sac in which the human embryo develops is called the amnion. The uterus is the organ in which the embryo implants and grows, while the endometrium is the layer of tissue lining the uterus. The yolk sac is another membrane surrounding the developing embryo, but it is not the primary fluid-filled sac.

Question 3

In humans, the exchanges of materials between the embryo and its mother occur through the

Accepted Answer

The umbilical cord connects the developing fetus to the placenta, which is attached to the mother's uterus. Through the umbilical cord, the fetus receives nutrients, oxygen, and hormones from the mother's blood while also eliminating waste products.

Question 4

This graph shows the normal concentration of morphogens A and B throughout a Drosophila embryo. 
If morphogen B is injected into the head end of an embryo, the embryo is likely to develop

Accepted Answer

The answer of This graph shows the normal concentration of...

Question 5

Different versions of the protein hemoglobin are found in a baby's blood cells at different stages of development. Changes in the hemoglobin type present are most likely the result of

Accepted Answer

Different versions of hemoglobin are the result of different genes being transcribed during development. As a baby grows, different genes are activated in different tissues and at different stages, resulting in the production of different types of hemoglobin to meet the changing needs of the growing organism.

Question 6

By the end of a normal first trimester, the zygote

Accepted Answer

By the end of the first trimester, the embryo has developed recognizable arms and legs, although they are not fully formed.

Question 7

Embryonic stem cells have the greatest potential for creating medical treatments because they

Accepted Answer

Embryonic stem cells have the ability to become any type of body cell, which makes them extremely versatile and useful for creating medical treatments. This property means that they could potentially be used to treat a wide range of conditions, from diabetes to spinal cord injuries. Additionally, embryonic stem cells can divide and multiply indefinitely in culture, making them a valuable resource for researchers studying cell biology and disease. While other types of stem cells, such as adult stem cells, also have potential for medical treatments, they are more limited in their ability to differentiate into different cell types.

Question 8

Which of the following does not affect development in animals?

Accepted Answer

Hemoglobin is a protein found in red blood cells that is responsible for oxygen transport, but it does not play a direct role in animal development. Morphogens, genes, and hormones are all important factors that can affect the development of an animal. Morphogens are signaling molecules that provide spatial information to cells to control their differentiation and patterning. Genes provide the blueprint for an animal's development and determine traits such as its physical characteristics and behaviors. Hormones are signaling molecules that regulate various developmental processes, such as growth and maturation.

Question 9

The body retains stems cells after embryonic development is complete because

Accepted Answer

Stem cells are responsible for the production and regeneration of various cells in our body which can be lost due to injury or wear and tear. Stem cells give rise to gametes in males throughout their life. Hence, all the given options are correct.

Question 10

The shape of the beak of a hummingbird (very long and skinny) and that of a finch (short and fat) is controlled by the same set of genes. Which of the following could account for the differences between these two bird beaks?

Accepted Answer

The differences in beak shape can be attributed to the duration for which the genes are active during development, leading to variations in growth patterns.

Question 11

Stem cells

Accepted Answer

Stem cells have the ability to differentiate into various types of cells or tissues, making them crucial for growth and repair in the body. They are able to develop into specific cell types in response to different signals or cues.

Question 12

In fruit flies, morphogens

Accepted Answer

Morphogens are signaling molecules that regulate gene expression and cell differentiation during development. In fruit flies, they play a crucial role in organizing the body plan and specifying different cell fates. By switching genes on and off in a concentration-dependent manner, morphogens create a gradient of gene activities across the developing embryo, leading to the formation of distinct tissues and organs. Morphogens are not composed of nucleic acids, nor are they receptor proteins, and they are not restricted to the eggs but are produced and distributed throughout the developing embryo.

Question 13

In humans, the yolk sac

Accepted Answer

The answer of In humans, the yolk sac
...

Question 14

The "quality" of human eggs and sperm declines as people age. One possible reason for this is

Accepted Answer

As people age, their cells accumulate more mutations, and egg and sperm precursor cells may acquire harmful mutations that affect the quality of eggs and sperm. This can lead to increased risk of genetic abnormalities and developmental disorders in offspring.

Question 15

Examine this close-up of the placenta (on the left of the figure). 
Why do the chorionic villi have the shape of a tree?

Accepted Answer

The shape of the chorionic villi resembles a tree with branches, which creates a large surface area for exchange of nutrients and gases between maternal and fetal blood. This allows for efficient transfer of oxygen and nutrients from the mother's blood to the fetus, and for removal of waste products from the fetus's blood. The larger surface area allows for greater exchange and more efficient transfer of molecules.

Question 16

This graph shows the rate of cell division in a developing frog embryo. 
Why does the rate of growth decrease dramatically after the point indicated by the arrow?

Accepted Answer

The most likely reason that the rate of growth decreases dramatically after the indicated point is because development switches from rapid cell growth to cell differentiation and migration. This is when the embryonic cells begin to specialize and acquire specific functions and structures, which requires more time and energy than simply dividing rapidly.

Question 17

Why does an embryo undergo the process of gastrulation?

Accepted Answer

Gastrulation is the process by which cells in the blastocyst differentiate to form embryonic tissues. During this process, the cells move around to create the three germ layers (endoderm, mesoderm, and ectoderm) and establish the basic body plan of the embryo. This is necessary because the cells that form these tissues are not originally located in the right place, and gastrulation moves these cells to the proper position in the embryo.

Question 18

Which of the following would not be exchanged between a mother and her fetus through the umbilical cord?

Accepted Answer

Enzymes are not typically exchanged between a mother and her fetus through the umbilical cord. The exchange of gases (oxygen and carbon dioxide) and immune factors (antibodies) is crucial for the health and development of the fetus.

Question 19

Human females probably involved the ability to live beyond their reproductive years because

Accepted Answer

The "Grandmother Hypothesis" suggests that post-reproductive lifespan in women evolved because grandmothers can help care for their grandchildren, thereby increasing the survival rate of their descendants.

Question 20

In the last few weeks of pregnancy, the level of estrogen in a woman's blood rises. This causes

Accepted Answer

The rise in estrogen during the last few weeks of pregnancy causes the muscles of the uterus to become more sensitive to the hormone oxytocin, leading to an increase in uterine contractions and ultimately the onset of labor. Option A is incorrect as the fetus generally slows down in growth towards the end of pregnancy. Option B is incorrect as the amount of prostaglandin secreted by the placenta increases during the last few weeks of pregnancy. Option D is also incorrect as the pituitary does not release more estrogen during pregnancy.

Quiz 29: Reproduction and Development