Question
How do autotrophs living in an aquatic ecosystem obtain carbon?
A. By diffusion of dissolved carbon dioxide and hydrogen carbonate ions
B. By feeding on heterotrophs and obtaining carbon from carbohydrates
C. By active transport of carbon dioxide directly from the atmosphere
D. By ingesting organisms with carbonate shells
▶️Answer/Explanation
Answer: A. By diffusion of dissolved carbon dioxide and hydrogen carbonate ions
Explanation:
Autotrophs are organisms that make their own food, usually through photosynthesis. In aquatic ecosystems, autotrophs like algae and some bacteria absorb carbon in the form of dissolved carbon dioxide (CO₂) and hydrogen carbonate ions (HCO₃⁻) from the surrounding water. These forms of carbon come from the atmosphere and dissolve into water, where autotrophs take them in by diffusion.
Evaluating the options:
A. Correct – Aquatic autotrophs absorb dissolved CO₂ and hydrogen carbonate ions through diffusion. This is the main way they obtain carbon for photosynthesis.
B. Incorrect – Autotrophs do not feed on heterotrophs; that describes heterotrophic behavior. Autotrophs make their own food.
C. Incorrect – CO₂ enters water from the atmosphere first, and then autotrophs absorb it in its dissolved form. They do not transport gas directly from air.
D. Incorrect – Ingesting other organisms is a heterotrophic process, not how autotrophs obtain carbon
Question
How is a prokaryotic cell different from a eukaryotic cell?
A. Eukaryotic cells are compartmentalized, whereas prokaryotic cells are not.
B. Prokaryotic cells do not contain ribosomes, whereas eukaryotic cells do.
C. Eukaryotic cells contain DNA, whereas prokaryotic cells do not.
D. Prokaryotic cells have a cell wall, whereas eukaryotic cells do not.
▶️Answer/Explanation
Answer: A. Eukaryotic cells are compartmentalized, whereas prokaryotic cells are not.
Explanation:
Prokaryotic cells are simpler, smaller cells without a nucleus or membrane-bound organelles. Their DNA is free-floating in the cytoplasm. Eukaryotic cells are more complex, larger, and have a true nucleus enclosed by a membrane, as well as many membrane-bound organelles like mitochondria and the endoplasmic reticulum.
Evaluating the options:
A. Correct – Eukaryotic cells are compartmentalized with membrane-bound organelles; prokaryotic cells lack this compartmentalization.
B. Incorrect – Both prokaryotic and eukaryotic cells have ribosomes, though prokaryotic ribosomes are smaller.
C. Incorrect – Both cell types contain DNA, but prokaryotic DNA is not enclosed in a nucleus.
D. Incorrect – Many prokaryotes have a cell wall, but some eukaryotic cells (like plant and fungal cells) also have cell walls.
Question
An animal has the following characteristics: bilateral symmetry, mouth but no anus, ribbon shape. Which phylum does the animal belong to?
Mollusca
Cnidaria
Annelida
Platyhelmintha
Answer/Explanation
Answer: D. Platyhelmintha
Explanation:
Animal phyla are classified based on body symmetry, presence of body openings (mouth, anus), and body shape. Bilateral symmetry means the body can be divided into mirror-image halves. A ribbon-shaped animal with a mouth but no anus suggests a simple digestive system with only one opening, which is typical of flatworms.
Evaluating the options:
A. Incorrect – Mollusca typically have a complete digestive system with both mouth and anus and are not ribbon-shaped.
B. Incorrect – Cnidaria (like jellyfish) have radial symmetry, not bilateral, and usually a single opening serving as mouth and anus.
C. Incorrect – Annelida (segmented worms) have bilateral symmetry and a complete digestive tract (mouth and anus).
D. Correct – Platyhelminthes (flatworms) have bilateral symmetry, a ribbon-shaped body, and a single opening serving as the mouth with no anus.
Question
The images show a structure found on members of a phylum of green plants.
What is the name of the phylum to which the organisms belong?
Coniferophyta
Angiospermophyta
Filicinophyta
Bryophyta
Answer/Explanation
Answer: A. Coniferophyta
Explanation:
roductive structures. Coniferophyta are gymnosperms seed-producing plants with cones (like pine trees). Angiospermophyta are flowering plants with seeds enclosed in fruits. Filicinophyta are ferns with spores and large fronds but no seeds. Bryophyta are non-vascular plants like mosses, which do not produce seeds or true vascular tissue.
Evaluating the options:
A. Correct – Coniferophyta are seed plants with cone structures, typical of gymnosperms. The images likely show cones or needle-like leaves characteristic of conifers.
B. Incorrect – Angiospermophyta have flowers and fruits, which are not shown in the images.
C. Incorrect – Filicinophyta (ferns) reproduce by spores and have large, divided leaves (fronds), not cones.
D. Incorrect – Bryophyta (mosses) are small, non-vascular plants without seeds or cones.
Question
A locust is an arthropod. For invertebrate groups, which recognition feature is found only in arthropods?
Bilateral symmetry
Jointed appendages
Wings
Segmented body
Answer/Explanation
Answer: B. Jointed appendages
Explanation:
Arthropods are animals without backbones that include insects, spiders, and crabs. Their most unique feature is jointed legs or limbs. These joints help them move easily. Other features like body segments or symmetry are shared with other animals too, but only arthropods have jointed appendages.
Evaluation of Each Option:
A. Incorrect – Bilateral symmetry (same left and right sides) is common in many animals, not just arthropods.
B. Correct – Jointed appendages (like legs with bends or joints) are found only in arthropods.
C. Incorrect – Wings are found in some insects, but not in all arthropods, and also in birds and bats.
D. Incorrect – A segmented body (body divided into parts) is also found in worms, so it’s not just for arthropods
Which is a characteristic of both bryophyta and filicinophyta?
A. Vascular tissue
B. Membranous leaves
C. Release of spores
D. Evergreen spines
Answer/Explanation
Answer: C. Release of spores
Explanation:
Bryophyta (like mosses) and filicinophyta (like ferns) are two groups of non-flowering plants. Bryophyta are very simple and do not have vascular tissue, while filicinophyta do have vascular tissue (xylem and phloem). However, both groups reproduce using spores instead of seeds or flowers.
Evaluation of Each Option:
A. Incorrect – Only filicinophyta have vascular tissue. Bryophyta do not, so this is not a shared characteristic.
B. Incorrect – Membranous leaves (thin, soft leaves) are more typical of bryophyta. Ferns have broader, more complex leaves called fronds. So this is not shared by both groups.
C. Correct – Both bryophyta and filicinophyta release spores to reproduce. They do not produce seeds or flowers.
D. Incorrect – Evergreen spines are found in some conifers, not in mosses or ferns.
Question
Which term describes the whole of the genetic information of an organism?
A. Genome
B. DNA
C. Gene pool
D. Allele frequency
▶️Answer/Explanation
Answer: A. Genome
Explanation:
The genome is the complete set of genetic information in an organism. It includes all of the DNA — both the genes (which code for proteins) and the non-coding sequences. Every cell with a nucleus in the body has a full copy of the genome.
Evaluation of Each Option:
A. Correct – The genome is the entire genetic material of an organism. It includes all of its genes and other DNA.
B. Incorrect – DNA is the molecule that carries genetic information, but the genome refers to all the DNA in an organism. So DNA is part of the genome, but not the same as the genome.
C. Incorrect – The gene pool refers to all the genes in a population, not in a single organism.
D. Incorrect – Allele frequency is the measure of how common a certain form of a gene (allele) is in a population. It’s not the name for all genetic information.
Question
A pregnant woman had fetal cells removed by chorionic villus sampling and tested. The following karyogram was produced.
What does this show?
A. The child is female with Down syndrome.
B. The child is female without Down syndrome.
C. The child is male with Down syndrome.
D. The child is male without Down syndrome.
▶️Answer/Explanation
Answer: D. The child is male without Down syndrome.
Explanation:
A karyogram is an image of all the chromosomes in a cell, arranged in pairs. It is used to check for abnormalities in chromosome number or structure. Humans normally have 46 chromosomes (23 pairs), including one pair of sex chromosomes.
- XX = female
- XY = male
Having three copies of chromosome 21 indicates Down syndrome (also called trisomy 21).
Evaluation of Each Option:
A. Incorrect – This would mean the fetus is female (XX) and has Down syndrome (three chromosome 21s). But the correct answer says it’s a normal male.
B. Incorrect – This would be correct if the fetus were XX and had two chromosome 21s. But it’s not female.
C. Incorrect – This describes a male with Down syndrome, which would show XY and three copies of chromosome 21.
D. Correct – If the karyogram shows XY (male) and two normal copies of chromosome 21, this means the child is male without Down syndrome.
Question
The image shows a human karyogram.
From which person was the karyogram obtained?
A. A female with Down syndrome
B. A female without Down syndrome
C. A male with Down syndrome
D. A male without Down syndrome
▶️Answer/Explanation
Answer: B. A female without Down syndrome
Explanation:
A karyogram shows all the chromosomes in a cell, arranged in numbered pairs from 1 to 22 (autosomes), plus the sex chromosomes (X and Y).
- Sex chromosomes determine biological sex:
- XX = female
- XY = male
- Down syndrome is caused by trisomy 21 having three copies of chromosome 21 instead of the normal two.
To determine the correct answer, we check:
- If there are two X chromosomes and no Y = female.
- If chromosome 21 appears twice = no Down syndrome.
Evaluation of Each Option:
A. Incorrect – This would be a female with three chromosome 21s (Down syndrome), but the image shows only two.
B. Correct – Two X chromosomes (XX) = female, and two chromosome 21s = no Down syndrome.
C. Incorrect – A male would have XY, not XX.
D. Incorrect – The person is female (XX), not male.
Question
Where can the entire genome of an organism be found?
A. In the DNA present in plasmids of a bacterial cell
B. In the DNA present in the nucleus of a eukaryotic cell
C. In the DNA present in the nucleus and chloroplasts of a plant cell
D. In the DNA present in the nucleus and mitochondria of an animal cell
▶️Answer/Explanation
The entire genome of an organism includes all of its genetic information. In eukaryotic cells (like plant and animal cells), most of the genome is in the nucleus, but a small part is also found in mitochondria (and in chloroplasts in plant cells). To account for the full genome, we must include all places in the cell where DNA is stored.
Evaluation of Each Option:
A. Incorrect – Plasmids only carry a small part of a bacterial cell’s genetic material. The full bacterial genome is mostly in the nucleoid region, not just plasmids.
B. Incorrect – The nucleus contains most of the genome in a eukaryotic cell, but not all. Mitochondria (and chloroplasts in plants) also contain some of the organism’s DNA.
C. Incorrect – This includes the nucleus and chloroplasts, which together store most of the plant genome, but it leaves out the mitochondria, which also have DNA.
D. Correct – In animals, the genome is found in the nucleus (main part) and mitochondria (small extra part). Together, they make up the entire genome of an animal.
Question
What is a feature of the human genome?
A. Plasmids
B. Messenger RNA
C. Transfer RNA
D. Mitochondrial DNA
▶️Answer/Explanation
Answer: D. Mitochondrial DNA
Explanation:
The human genome is the complete set of genetic information in human cells. It includes all the DNA found in the nucleus and the mitochondria. While RNA (like mRNA and tRNA) is made from DNA and plays important roles in protein synthesis, only DNA—not RNA—is part of the genome. Humans do not have plasmids, which are found in bacteria.
Evaluation of Each Option:
A. Incorrect – Plasmids are small, circular DNA found in bacteria, not in humans. They are not part of the human genome.
B. Incorrect – Messenger RNA (mRNA) is made from DNA to carry genetic instructions, but mRNA itself is not part of the genome.
C. Incorrect – Transfer RNA (tRNA) helps in protein building, but like mRNA, it is produced from DNA. It is not part of the genome.
D. Correct – Mitochondrial DNA is a small part of the human genome, located inside mitochondria. It is inherited only from the mother and is part of the complete genome.