During embryonic development, which of the following germ layers forms the nervous system?
A. Ectoderm
B. Endoderm
C. Mesoderm
D. Exoderm
The three germ layers that form during embryonic development are the ectoderm, mesoderm, and endoderm. The ectoderm is the outermost layer, and it gives rise to the skin, hair, nails, and nervous system. The nervous system develops from a specialized region of the ectoderm called the neural plate, which invaginates to form the neural tube. The neural tube ultimately gives rise to the brain and spinal cord, which make up the central nervous system, as well as the peripheral nervous system. The endoderm gives rise to the lining of the digestive and respiratory tracts, while the mesoderm gives rise to the musculoskeletal system, circulatory system, and several other organs. The exoderm is not a germ layer and does not exist during embryonic development.
Therefore, the Correct Answer is A.
More Questions on TEAS 7 Science
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Q #1: Which of the following is an example of a double-blind study?
A. Participants are randomly assigned to a treatment group or a control group
B. Participants and researchers both know which group participants are assigned to
C. Participants do not know which group they are assigned to, but researchers do
D. Both participants and researchers do not know which group participants are assigned to
Answer Explanation
A double-blind study is a research design in which neither the participants nor the researchers know which group participants are assigned to. This is done to minimize bias and ensure that the results of the study are as objective as possible. In a double-blind study, the treatment and control groups are randomly assigned, and the participants and researchers are unaware of which group each participant is assigned to. Option a) is an example of a randomized controlled trial, which is a common research design, but it is not necessarily double-blind. Option b) is an example of an open-label study, in which both the participants and the researchers know which group each participant is assigned to. Option c) is an example of a single-blind study, in which the participants do not know which group they are assigned to, but the researchers do.
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Q #2: What is the function of ribosomes in a cell?
A. To produce energy for the cell
B. To store genetic information
C. To transport molecules within the cell
D. To synthesize proteins in the cell
Answer Explanation
Ribosomes are small, spherical structures found in all living cells, including bacteria, archaea, and eukaryotes. Their primary function is to synthesize proteins using the genetic information stored in the cell's DNA. Ribosomes are composed of two subunits, one large and one small, that come together during protein synthesis.
Ribosomes read the genetic information stored in mRNA (messenger RNA) and use this information to assemble amino acids in the correct order to form a protein. The ribosome moves along the mRNA, adding one amino acid at a time to the growing protein chain until it reaches the end of the mRNA and the protein is complete.
Proteins are essential for a wide variety of cellular functions, including catalyzing chemical reactions, providing structural support, and transporting molecules across cell membranes. Therefore, ribosomes play a critical role in the overall function and survival of a cell.
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Q #3: Which of the following is a type of genetic mutation that involves the insertion or deletion of one or more nucleotides in a DNA sequence?
A. Silent mutation
B. Nonsense mutation
C. Frameshift mutation
D. Missense mutation
Answer Explanation
A frameshift mutation is a type of genetic mutation that involves the insertion or deletion of one or more nucleotides in a DNA sequence. This can cause a shift in the reading frame of the genetic code, resulting in a change in the amino acid sequence of the resulting protein. Frameshift mutations can have significant effects on the function of the protein and can lead to genetic disorders or diseases.
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Q #4: What is the role of calcium in muscle contraction?
A. Calcium binds to tropomyosin to expose the myosin-binding sites on actin.
B. Calcium is released from the sarcoplasmic reticulum to initiate the sliding of actin and myosin filaments.
C. Calcium activates the motor neurons to stimulate muscle contraction.
D. Calcium is required for the relaxation of muscles after contraction.
Answer Explanation
Muscle contraction is a complex process that involves the interaction between actin and myosin filaments in the muscle fibers. The sliding of these filaments is initiated by the release of calcium ions from the sarcoplasmic reticulum, a specialized organelle in muscle cells. The calcium ions bind to the protein troponin, which causes a conformational change in the troponin-tropomyosin complex, exposing the myosin-binding sites on actin. This allows the myosin heads to bind to actin, forming cross-bridges that pull the actin filaments towards the center of the sarcomere, resulting in muscle contraction.
Option a) is incorrect because calcium does not bind to tropomyosin directly, but rather binds to the protein troponin, causing a conformational change in the troponin-tropomyosin complex. Option c) is incorrect because calcium does not activate motor neurons, but rather is released from the sarcoplasmic reticulum in response to an action potential that travels down the motor neuron to the neuromuscular junction. Option d) is incorrect because calcium is required for muscle contraction, not relaxation. The relaxation of muscles after contraction is due to the active transport of calcium ions back into the sarcoplasmic reticulum, which allows the troponin-tropomyosin complex to return to its resting conformation, blocking the myosin-binding sites on actin and ending the cross-bridge cycle.
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Q #5: Which of the following is the process by which DNA is copied into RNA?
A. Replication
B. Transcription
C. Translation
D. Mutation
Answer Explanation
Transcription is the process by which DNA is copied into RNA. During transcription, the DNA molecule unwinds and RNA polymerase reads the DNA sequence and synthesizes a complementary RNA molecule using the DNA as a template.
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Q #6: What is the name of the genetic disorder caused by the presence of an extra chromosome 21?
A. Turner syndrome
B. Klinefelter syndrome
C. Down syndrome
D. Huntington's disease
Answer Explanation
Down syndrome is a genetic disorder caused by the presence of an extra copy of chromosome 21. It is also known as trisomy 21, because affected individuals have three copies of chromosome 21 instead of the normal two.
The extra chromosome 21 in Down syndrome occurs due to a random error in cell division, which leads to the production of an abnormal gamete (egg or sperm) with an extra copy of the chromosome. When this gamete fuses with a normal gamete during fertilization, the resulting zygote has 47 chromosomes instead of the usual 46, and develops into a fetus with Down syndrome.
Down syndrome is characterized by a range of physical and intellectual symptoms, including developmental delays, intellectual disability, distinctive facial features, heart defects, and increased risk of certain medical conditions such as leukemia and Alzheimer's disease. However, the severity and expression of these symptoms can vary widely among affected individuals.
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Q #7: What is the chemical formula for water?
A. H2O
B. CO2
C. NaCl
D. C6H12O6
Answer Explanation
The chemical formula for water is H2O. It consists of two hydrogen atoms and one oxygen atom.
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Q #8: What is the difference between a physical change and a chemical change?
A. A physical change involves the rearrangement of atoms and molecules while a chemical change involves the formation of new substances with different chemical properties.
B. A physical change involves the change of one state of mater to another while a chemical change involves the change of one substance into another.
C. A physical change involves the breaking of chemical bonds while a chemical change involves the breaking of intermolecular forces.
D. A physical change involves the release of energy while a chemical change involves the absorption of energy.
Answer Explanation
A physical change is a change that affects the physical properties of a substance, but does not change its chemical identity. Physical changes include changes in state, such as melting or boiling, changes in shape or size, and changes in phase, such as the dissolution of a solid in a liquid. In a physical change, the atoms and molecules of the substance are rearranged, but no new substances are formed.
A chemical change, on the other hand, is a change that results in the formation of new substances with different chemical properties. Chemical changes involve the breaking of chemical bonds between atoms and the formation of new bonds to create new compounds. Chemical changes are usually accompanied by a change in color, the formation of a gas or a solid, or the release or absorption of energy.
Overall, the main difference between a physical change and a chemical change is that a physical change only affects the physical properties of a substance while a chemical change results in the formation of new substances with different chemical properties.
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Q #9: What is the role of the epididymis in sperm maturation?
A. The epididymis produces sperm cells.
B. The epididymis stores and protects sperm cells until ejaculation.
C. The epididymis is responsible for the transport of sperm cells from the testes to the urethra.
D. The epididymis provides nourishment to sperm cells.
Answer Explanation
The epididymis is a coiled tube located at the back of each testicle where the sperm mature and are stored until ejaculation. Sperm are produced in the testes and then transported to the epididymis where they undergo maturation and become motile. The epididymis provides a protective environment for the sperm, allowing them to mature and become more resilient to external stressors. During ejaculation, the sperm are transported from the epididymis to the vas deferens and then to the urethra for ejaculation.
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Q #10: Which of the following is a function of the respiratory system?
A. Transport of nutrients to the body
B. Pumping of blood to the lungs
C. Exchange of gases between the body and the environment
D. Digestion of food in the stomach
Answer Explanation
One of the main functions of the respiratory system is to facilitate the exchange of gases between the body and the environment. During inhalation, air enters the lungs and oxygen is absorbed into the bloodstream. During exhalation, carbon dioxide is removed from the body and expelled into the environment.
