HESI A2
Biology HESI A2 Practice Test
1. Select the cell parts that are present in plant cells but not animal cells (there may be more than one answer):
- A. Cell membrane
- B. Cell wall
- C. Ribosome
- D. Chloroplast
Correct answer: B
Rationale: Plant cells have a cell wall (B) which provides structural support and protection for the cell, a feature that is not present in animal cells. The cell membrane (A) is found in both plant and animal cells. Ribosomes (C) are present in both types of cells and are responsible for protein synthesis. Chloroplasts (D) are unique to plant cells and are responsible for carrying out photosynthesis. Therefore, the correct answers are B and D because the cell wall and chloroplast are specific to plant cells, while the cell membrane and ribosomes are found in both plant and animal cells.
2. Which of the following is true of homozygous traits?
- A. They are haploid
- B. They are denoted AA
- C. They are denoted aa
- D. They are denoted Aa
Correct answer: B
Rationale: Homozygous traits have two identical forms of the gene, either both dominant (AA) or both recessive (aa). Therefore, choices B and C are true for homozygous traits. Choice A is incorrect because being haploid refers to having a single set of chromosomes, not necessarily homozygous traits. Choice D is incorrect as homozygous traits have identical alleles, so they are not denoted as Aa.
3. 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.
4. Which is not a step in the water cycle?
- A. Condensation
- B. Transpiration
- C. Nitrification
- D. Absorption
Correct answer: C
Rationale: Nitrification is a biological process in the nitrogen cycle where ammonia is converted into nitrites and then nitrates by bacteria. It is not a step in the water cycle. The water cycle involves processes like evaporation, condensation, precipitation, and transpiration that are related to the movement and transformation of water in the environment. Choices A, B, and D are all part of the water cycle: condensation is the process where water vapor turns into liquid water, transpiration is the release of water vapor by plants, and absorption refers to the process of water being taken in by soil or other materials.
5. How are molecules of water bonded to each other?
- A. Ionic
- B. Covalent
- C. Hydrogen
- D. Molecular
Correct answer: C
Rationale: Water molecules are bonded to each other by 'hydrogen' bonds. These bonds are not as strong as covalent bonds, which hold the atoms within each water molecule together (Choice B). Ionic bonds (Choice A) involve the transfer of electrons between atoms, which is not the case in water molecules. The term 'molecular' (Choice D) is too general and doesn't specifically describe the type of bond between water molecules.
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