Question 1

The earliest metazoans to have neurons were the

Accepted Answer

Cnidarians, which include jellyfish and sea anemones, are the earliest metazoans to have neurons. They have a simple nerve net, which is a diffuse network of neurons that allows for coordinated movement and response to stimuli. Sponges, nematodes, and echinoderms do not have true neurons.

Question 2

The first organisms to have more than one type of cell were the

Accepted Answer

Metazoans are multicellular organisms with more than one specialized cell type. They include animals such as sponges, jellyfish, and humans. Protozoans, on the other hand, are unicellular organisms and do not have multiple cell types. Vertebrates and protostomes are types of metazoans, but the development of multiple cell types occurred earlier in evolution than the emergence of these specific groups.

Question 3

The theory that an organism develops by gradually changing to acquire new, more complex structures is called

Accepted Answer

The theory of epigenesis proposes that an organism develops by gradually acquiring new, more complex structures, as opposed to preformation theory which suggests that all the complex structures of an organism are already present in miniature form within the sperm or egg. Micrographia refers to the study of microscopic objects, and rationalism is a philosophical belief that emphasizes the use of reason and deduction to understand the world.

Question 4

The modern synthesis of evolution postulated that

Accepted Answer

The modern synthesis of evolution, also known as neo-Darwinism, proposed that parents pass along discrete units of inheritance, now known as genes, to their offspring. This concept was crucial in explaining the mechanism of natural selection and the process of evolution.

Question 5

The phenotype of an individual organism or cell refers to the

Accepted Answer

The phenotype of an individual organism or cell refers to their physical characteristics displayed at a particular time. This can include things like height, eye color, and behavior. It is determined by a combination of genetic and environmental factors and can change over time. Therefore, choice A is the best fit for the definition of phenotype.

Question 6

Regions of a gene that do not encode for any mRNA are

Accepted Answer

Regions of genes that do not encode any mRNA are non-coding regions or introns. They are not degraded during gene transcription, and are not remnants of ancestral genes that are no longer needed. Instead, they are used to regulate gene expression by controlling the splicing and stability of the mRNA that is produced. Non-coding regions are still present in vertebrate genes.

Question 7

Molecules that regulate gene expression are called

Accepted Answer

Molecules that regulate gene expression are called transcription factors. Promoters describe the DNA sequence that initiates transcription, exons are the coding regions of DNA, and translation factors assist in protein synthesis.

Question 8

If cells follow their particular fate regardless of what their neighboring cells do, they are said to have _______ specification.

Accepted Answer

If cells follow their particular fate regardless of what their neighboring cells do, it means that cell fate is predetermined and not dependent on cell-to-cell signaling. This is a characteristic of mosaic specification, in which each cell has a specific fate that is determined early during development and is not affected by the surrounding cells. Conditional specification, on the other hand, refers to a situation in which cell fate is determined later in development and can be influenced by signals from neighboring cells. Regulatory specification refers to a process in which the fate of a cell is determined by signals from other cells, and spontaneous specification is not a term commonly used in developmental biology.

Question 9

How can an organism like C. elegans, which follows an invariant pattern of mitosis, develop different cell types in a dividing zygote?

Accepted Answer

The mother deposits different transcription factors in different parts of the egg, which help to establish different cellular identities in the dividing zygote. This is known as maternal determinants.

Question 10

The first recognizable structure that embryos form is the

Accepted Answer

The answer of The first recognizable structure that embryos form...

Question 11

From earliest to latest in development, what is the correct order of vertebrate embryological ontogeny?

Accepted Answer

The correct order in vertebrate embryological ontogeny is blastula (single layer of cells), gastrula (formation of three germ layers), and neurula (formation of neural tube).

Question 12

Which germ layer provides the cellular precursors to the nervous system?

Accepted Answer

The ectoderm is responsible for the development of the nervous system, including the brain and spinal cord. The cells within the ectoderm become neuroblasts, which give rise to neurons and other cells in the nervous system.

Question 13

The crease formed by the primitive streak is more pronounced at one end, called the node, which will form the

Accepted Answer

The node formed by the primitive streak is structurally and functionally important for the development of the brain and head.

Question 14

The neural tube will give rise to the _______, while the neural crest will give rise to the _______.

Accepted Answer

The neural tube develops into the central nervous system (CNS), which includes the brain and spinal cord, while the neural crest cells contribute to the formation of the peripheral nervous system (PNS), among other structures.

Question 15

What experimental result demonstrates the concept of self-regulation?

Accepted Answer

Surgically removing a chick limb bud causes remaining nearby cells to create a new one, which demonstrates the concept of self-regulation. This process is known as compensatory regeneration and is a form of self-regulation where the body is able to compensate for the loss of tissue or organ by regenerating it using its own cells. This process occurs in various organisms and is a key aspect of development and homeostasis. The other options describe different developmental phenomena but do not demonstrate self-regulation in the same way.

Question 16

If you introduce stem cells with a new gene into a mouse blastula, and that mouse grows up to produce pups that also have that transgene, what can you conclude about the fate of those original transgenic stem cells?

Accepted Answer

The stem cells with the new gene must have differentiated into germ cells (sperm or eggs) in the parent mouse. This is the only way the transgene could be passed on to the offspring through sexual reproduction, indicating that the transgenic stem cells contributed to the mouse's germ line.

Question 17

The process by which one tissue directs the differentiation of another tissue is called

Accepted Answer

The process by which one tissue directs the differentiation of another tissue is called induction.

Question 18

If developing cells communicate with one another to induce a particular fate in neighboring cells, the very first cells must receive their instructions of what to become from

Accepted Answer

The term "organizer" refers to a group of cells that secrete signaling molecules that induce neighboring cells to adopt a specific fate during embryonic development. The very first cells would need to receive their fate instructions from an organizer in order for subsequent cell specification to occur. Mosaic specification refers to the differentiation of cells based on their position in the embryo, but does not account for how the first cell received its fate instructions. Mitotic lineage simply refers to the series of cell divisions that give rise to differentiated cells, and conditional specification refers to cells adopting a particular fate based on environmental cues rather than signaling from neighboring cells.

Question 19

In their search for the organizer signal, the hypothesis the researchers developed after exposing frog embryos to lithium chloride was that lithium chloride may

Accepted Answer

Lithium chloride increases the expression of the organizer.

Question 20

Organizer proteins _______ TGFβ receptor signaling, thus inducing _______ development.

Accepted Answer

The answer of Organizer proteins _______ TGFβ receptor signaling, thus...

Quiz 1: Cell Differentiation and Neural Induction