Nokea
What impact would the removal of a keystone species have in an ecosystem?
- A. Lead to a decrease in competition among other species
- B. Cause a slight increase in primary productivity
- C. Have a minimal impact on the overall ecosystem structure
- D. Disrupt the food web and cause cascading effects on other populations
Correct Answer: D
Rationale: Keystone species play a crucial role in maintaining the balance and structure of an ecosystem due to their significant influence. If a keystone species is removed, it disrupts the delicate food web dynamics and can trigger cascading effects throughout the ecosystem. The disruption in predator-prey relationships can lead to population declines and even extinctions of other species. Options A, B, and C are incorrect because the removal of a keystone species would not decrease competition among other species, cause a slight increase in primary productivity, or have a minimal impact on the overall ecosystem structure. Instead, it would have a profound impact, disrupting the food web and causing cascading effects on other populations.
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What type of lens is thinner at the center than at the edges and causes light rays to diverge?
- A. Convex lens
- B. Concave lens
- C. Diverging lens
- D. Plano-convex lens
Correct Answer: B
Rationale: A concave lens is thinner at the center than at the edges, causing light rays to diverge when passing through it. This type of lens is also known as a diverging lens because it causes light rays to spread out. Concave lenses are used in various optical devices to correct vision problems and in scientific instruments to diverge light rays for specific purposes. The other choices are incorrect. A convex lens is thicker at the center and converges light rays, while a plano-convex lens has one flat surface and one convex surface, converging light. Diverging lens is a general term that can refer to concave or plano-concave lenses, but in this context, the specific type being referred to is a concave lens.
What scientific term encompasses a permanent alteration in the DNA sequence?
- A. Trait
- B. Mutation
- C. Allele
- D. Variation
Correct Answer: B
Rationale: A) Trait: A trait is a characteristic or feature of an organism that is determined by its genes.
B) Mutation: A mutation is a permanent alteration in the DNA sequence that can result from errors during DNA replication, exposure to mutagens, or other factors.
C) Allele: An allele is a variant form of a gene that can result in different traits or characteristics.
D) Variation: Variation refers to the differences in traits or characteristics among individuals of the same species, which can be influenced by genetic and environmental factors.
In this context, the term that specifically refers to a permanent alteration in the DNA sequence is "mutation."
What is the term for a repetitive, involuntary muscle contraction that can cause pain and stiffness?
- A. Cramp
- B. Spasm
- C. Tic
- D. Fibrosis
Correct Answer: B
Rationale: A spasm is a repetitive, involuntary muscle contraction that can cause pain and stiffness. While cramps are a type of spasm, not all spasms are cramps. Tics are sudden, repetitive movements or sounds made involuntarily. Fibrosis refers to the formation of excess fibrous connective tissue in an organ or tissue as part of a reparative or reactive process. In this context, a spasm best fits the description provided, making it the correct answer. Cramp, although related to spasms, is more specific and not the general term being sought. Tic does not describe a muscle contraction but rather sudden movements or sounds. Fibrosis does not directly relate to muscle contractions but rather to the formation of excess fibrous tissue in organs or tissues.
What is the main component of stomach acid?
- A. Hydrochloric acid
- B. Bicarbonate
- C. Bile salts
- D. Enzymes
Correct Answer: A
Rationale: Stomach acid, also known as gastric acid, is primarily composed of hydrochloric acid. Hydrochloric acid plays a crucial role in the digestive process by helping to break down food and kill bacteria in the stomach. Bicarbonate is a base that helps neutralize stomach acid in the small intestine, but it is not the main component of stomach acid. Bile salts are produced by the liver and stored in the gallbladder, aiding in the digestion and absorption of fats, but they are not the main component of stomach acid. Enzymes are proteins that help catalyze chemical reactions in the body, including the breakdown of food molecules during digestion, but they are not the main component of stomach acid.
Which compound is a component of baking soda and is important for maintaining pH balance in the body?
- A. Potassium
- B. Sodium
- C. Calcium
- D. Sodium bicarbonate
Correct Answer: D
Rationale: The correct answer is D, Sodium bicarbonate. Sodium bicarbonate, commonly known as baking soda, is a compound that plays a crucial role in maintaining pH balance in the body. When ingested, sodium bicarbonate acts as a buffer, helping to regulate the body's pH levels. It is essential for various physiological functions. Choices A, B, and C are incorrect. Potassium, calcium, and sodium are important minerals in the body but are not components of baking soda or directly responsible for maintaining pH balance in the same way as sodium bicarbonate.