Nokea
Why are bacteria and blue-green algae often classified together?
- A. Both are gymnosperms.
- B. Both are prokaryotes.
- C. Both are autotrophs.
- D. Both are pathogens.
Correct Answer: B
Rationale: Bacteria and blue-green algae (cyanobacteria) are often classified together because they are both prokaryotes. Prokaryotes are unicellular organisms that lack a membrane-bound nucleus and other membrane-bound organelles. This characteristic distinguishes them from eukaryotic organisms, which have these membrane-bound structures. Choice A is incorrect because gymnosperms are seed-producing plants with naked seeds, not bacteria or blue-green algae. Choice C is incorrect because being an autotroph (able to produce its own food) is not a reason for classifying them together. Choice D is incorrect because not all bacteria and blue-green algae are pathogens; many of them are beneficial or neutral to other organisms.
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Which statement regarding energy content is true?
- A. Decomposers < secondary consumers
- B. Primary consumers < producers
- C. Producers > secondary consumers
- D. Secondary consumers < primary consumers
Correct Answer: C
Rationale: The correct answer is C: "Producers > secondary consumers." Producers, like plants, are the foundation of the energy pyramid, containing the highest energy content in an ecosystem. They convert solar energy into chemical energy through photosynthesis. Secondary consumers, being organisms that feed on other organisms, have lower energy content compared to producers. This hierarchy in energy content is due to the transfer of energy through trophic levels. Choice A is incorrect because decomposers, though essential for nutrient recycling, typically have lower energy content than secondary consumers. Choice B is incorrect because primary consumers, which feed directly on producers, have lower energy content than producers. Choice D is incorrect because secondary consumers have lower energy content compared to primary consumers.
What is represented by this formula: 6COâ‚‚ + 6Hâ‚‚O → C₆Hâ‚â‚‚O₆ + 6Oâ‚‚?
- A. Glycolysis
- B. Cellular respiration
- C. Photosynthesis
- D. Electronic transport
Correct Answer: C
Rationale: The formula represents the process of photosynthesis, where carbon dioxide (COâ‚‚) and water (Hâ‚‚O) are converted into glucose (C₆Hâ‚â‚‚O₆) and oxygen (Oâ‚‚) using light energy. This process is essential for plants and some microorganisms to produce food and oxygen. Glycolysis and cellular respiration involve breaking down glucose to produce energy, and the electron transport chain is part of cellular respiration, not photosynthesis.
In a strand of DNA, you would expect to see adenine paired with ___________.
- A. cytosine
- B. uracil
- C. thymine
- D. guanine
Correct Answer: C
Rationale: In a strand of DNA, adenine always pairs with thymine through two hydrogen bonds. This pairing is a fundamental aspect of DNA structure, where adenine and thymine complement each other in the double helix. Choice A (cytosine) is incorrect because adenine does not pair with cytosine in DNA. Choice B (uracil) is incorrect as uracil is found in RNA, not DNA. Choice D (guanine) is incorrect as guanine pairs with cytosine, not adenine, in DNA.
Which of these molecules contains glucose?
- A. Proteins
- B. Lipids
- C. Nucleic acids
- D. Carbohydrates
Correct Answer: D
Rationale: Glucose is a type of simple sugar and is classified as a carbohydrate. It is commonly found in various carbohydrate-containing foods such as fruits, vegetables, grains, and sugary snacks. Therefore, the molecule containing glucose would be a carbohydrate, making choice D the correct answer. Proteins (choice A) are made up of amino acids, lipids (choice B) are fats, and nucleic acids (choice C) are DNA and RNA, none of which contain glucose.
What takes place in a lysosome?
- A. Ribosomes are made.
- B. Food is produced.
- C. Water is stored.
- D. Food is digested.
Correct Answer: D
Rationale: In a lysosome, food particles are digested through the action of enzymes. Lysosomes are membrane-bound organelles containing digestive enzymes that break down large molecules into smaller ones, allowing the cell to utilize the nutrients for energy and other processes. Choices A, B, and C are incorrect because ribosomes are not made in lysosomes, food is not produced in lysosomes, and lysosomes do not store water.