Question 1

Fertilization of an egg without activation is most like

Accepted Answer

Just like placing the key in the ignition of a car does not start the engine, fertilization of an egg without activation does not trigger the start of embryonic development.

Question 2

The proposal that a human sperm contained a miniature human being is consistent with the now-discredited theory of development known as

Accepted Answer

The proposal that a human sperm contained a miniature human being is consistent with the theory of preformation, which was widely accepted in the 17th and 18th centuries. This theory suggested that all living organisms were pre-formed in a miniature form within their respective reproductive cells (sperm or egg) and simply grew into larger organisms during development, rather than being formed from scratch through a process of epigenesis (the gradual differentiation and organization of cells and tissues during embryonic development).

Question 3

In an egg cell treated with EDTA, a chemical that binds calcium and magnesium ions, the

Accepted Answer

The fertilization envelope is formed by the fusion of the egg cell membrane and the cortical granules exocytosed from the egg during the cortical reaction. EDTA treatment blocks the cortical reaction by removing calcium ions, so the fertilization envelope would not be formed.

Question 4

From earliest to latest, the overall sequence of early development proceeds as follows:

Accepted Answer

The acrosomal reaction occurs first during fertilization, followed by the cortical reaction to prevent polyspermy. Then, the synthesis of the embryo's DNA begins, and finally, the first cell division occurs.

Question 5

The cortical reaction functions directly in the

Accepted Answer

The cortical reaction is a process that occurs immediately after the sperm cell fuses with the egg cell, leading to the release of enzymes that form a fertilization envelope. This envelope serves as a barrier to prevent additional sperm from fertilizing the egg, thus providing a fast block to polyspermy.

Question 6

Fertilization normally

Accepted Answer

Fertilization results in the fusion of a haploid gamete from the male parent and a haploid gamete from the female parent, leading to the formation of a diploid zygote. Therefore, fertilization reinstates diploidy.

Note: Option B is incorrect because gastrulation is a process in which the three germ layers of the embryo are formed, which occurs after fertilization. Option C is incorrect because parthenogenesis is a form of reproduction in which an egg develops into an embryo without being fertilized. Option D is incorrect because fertilization merges two haploid cells into one diploid cell. Option E is incorrect because ovulation is the release of the mature egg from the ovary, which occurs prior to fertilization.

Question 7

Compared to sea urchin eggs, those of mammals

Accepted Answer

Sea urchin eggs complete meiosis before ovulation, whereas mammalian eggs do not complete meiosis until after fertilization. Therefore, they have not already completed meiosis at the time of ovulation.

Question 8

Assume that successful reproduction in a rare salamander species, wherein all individuals are females, relies on those females having access to sperm from males of another species but that the resulting embryos show no signs of a genetic contribution from the sperm. In this case, the sperm appear to be used only for

Accepted Answer

The fact that the embryos show no genetic contribution from the sperm suggests that the sperm is not contributing to the creation of a diploid cell or cell differentiation. Morphogenesis and epigenesis involve changes in gene expression and development over time, which also does not seem to be the case here. Therefore, the most likely use for the sperm in this scenario is egg activation, which triggers the beginning of embryonic development.

Question 9

From earliest to latest, the overall sequence of early development proceeds as follows:

Accepted Answer

The correct sequence of early development is cleavage (rapid cell division), followed by gastrulation (formation of three embryonic germ layers), and then organogenesis (differentiation of organs and body structures). Therefore, option C, which lists the sequence as cleavage, gastrulation, and organogenesis, is the best choice. The other options either list the steps in the wrong order or include irrelevant steps.

Question 10

Contact of an egg with signal molecules on sperm causes the egg to undergo a brief

Accepted Answer

Contact of an egg with signal molecules on sperm causes the egg to depolarize its membrane, which serves as a block to polyspermy.

Question 11

Contact of a sperm with signal molecules in the coat of an egg causes the sperm to undergo

Accepted Answer

Contact of a sperm with signal molecules in the coat of an egg triggers the acrosomal reaction, which involves the release of enzymes that help the sperm penetrate the egg. Mitosis and vitellogenesis are not directly related to fertilization, depolarization can occur but is not the primary response, and apoptosis leads to cell death and is not desired during fertilization.

Question 12

In mammalian eggs, the receptors for sperm are found in the

Accepted Answer

The zona pellucida is a thick glycoprotein layer that surrounds the mammalian egg and contains receptors for sperm. These receptors are necessary for fertilization to occur because they allow the sperm to bind to the egg and initiate the process of fusion. The other options listed do not contain sperm receptors in mammalian eggs.

Question 13

In mammals, the nuclei resulting from the union of the sperm and the egg are first truly diploid at the end of the

Accepted Answer

During initial cleavage, the zygote undergoes mitotic cell divisions without significant growth, which results in progressively smaller cells called blastomeres. At the end of initial cleavage, the blastomeres are still haploid, but they eventually fuse to form the first diploid cell of the developing embryo.

Question 14

The "slow block" to polyspermy is due to

Accepted Answer

The slow block to polyspermy is due to the formation of the fertilization envelope, a protective layer that forms around the egg cell following fertilization. This envelope prevents additional sperm from fertilizing the egg by altering the egg's membrane properties and making it impenetrable to sperm.

Question 15

A puppy is born with a malformed right leg. A veterinarian studies the animal and determines that all of the correct types of cells are present, but that the leg simply took on the wrong shape. This is most likely a problem of

Accepted Answer

Morphogenesis refers to the process of shaping or forming organs and tissues, which is exactly what is described in the scenario of the puppy's malformed leg. The cells are present and differentiated correctly, but the leg took on the wrong shape during development. Cell differentiation refers to the specialization of cells into specific types, while histogenesis refers to the formation of tissue from cells. Preformation and fertilization are not relevant to the scenario described.

Question 16

The vitelline layer of the sea urchin egg

Accepted Answer

The vitelline layer of the sea urchin egg has receptor molecules that are specific for binding acrosomal proteins, which aid in fertilization.

Question 17

Molecular genetic evidence that certain genes shared by both humans and fruit flies initiate eye development in both species suggest a common

Accepted Answer

The presence of certain genes responsible for initiating eye development in both humans and fruit flies suggest a genetic toolkit for development that is common to both species. This commonality is likely the result of shared ancestry and evolutionary history. The other options (complete genome, use of ATP in energy-transfer reactions, homunculi, duration of pregnancy) do not directly relate to the evidence of shared genes for eye development.

Question 18

You buy a pie that contains a swirled mixture of chocolate and vanilla filling. When you cut the pie up, you notice that some slices have more chocolate than vanilla and that other slices have more vanilla than chocolate. This uneven distribution of chocolate and vanilla is most like the uneven distribution of

Accepted Answer

Cytoplasmic determinants in a zygote are unevenly distributed, similar to the uneven distribution of chocolate and vanilla in the pie.

Question 19

During fertilization, the acrosomal contents

Accepted Answer

The acrosomal contents released by the sperm during fertilization contain digestive enzymes that are required to digest the protective coat on the surface of the egg, also known as the zona pellucida. This allows the sperm to penetrate and eventually fuse with the egg's plasma membrane, leading to fertilization.

Question 20

As an embryo develops, new cells are produced as the result of

Accepted Answer

New cells are produced as a result of cell division, where the original cell divides into two daughter cells. Differentiation (A) refers to the process by which cells become specialized, while preformation (B) refers to the idea that all the characteristics of an organism are already preformed in the sperm or egg before fertilization. Morphogenesis (D) refers to the development of the organism's physical form, while epigenesis (E) refers to the idea that an organism's characteristics are determined by interactions between genes and the environment.

Quiz 47: Animal Development

Fertilization of an egg without activation is most like

The proposal that a human sperm contained a miniature human being is consistent with the now-discredited theory of development known as

In an egg cell treated with EDTA, a chemical that binds calcium and magnesium ions, the

From earliest to latest, the overall sequence of early development proceeds as follows:

The cortical reaction functions directly in the

Fertilization normally

Compared to sea urchin eggs, those of mammals

From earliest to latest, the overall sequence of early development proceeds as follows:

Contact of an egg with signal molecules on sperm causes the egg to undergo a brief

Contact of a sperm with signal molecules in the coat of an egg causes the sperm to undergo

In mammalian eggs, the receptors for sperm are found in the

In mammals, the nuclei resulting from the union of the sperm and the egg are first truly diploid at the end of the

The "slow block" to polyspermy is due to

A puppy is born with a malformed right leg. A veterinarian studies the animal and determines that all of the correct types of cells are present, but that the leg simply took on the wrong shape. This is most likely a problem of

The vitelline layer of the sea urchin egg

Molecular genetic evidence that certain genes shared by both humans and fruit flies initiate eye development in both species suggest a common

During fertilization, the acrosomal contents

As an embryo develops, new cells are produced as the result of