Free IB Biology Questions and Answers — Questions and Answers

Question 1: A DNA mutation known as a ___________ alters the DNA sequence but does not modify the amino acids in a protein.

Insertion mutation
Silent mutation (Correct answer)
Deletion mutation
Frameshift mutation

Correct answer: Silent mutation

A silent mutation is a type of point mutation where a change in a single DNA nucleotide base occurs, but this change does not alter the amino acid sequence of the protein produced. This is possible because the genetic code is degenerate, meaning multiple codons can code for the same amino acid. Therefore, even with a DNA sequence change, the resulting protein remains functionally identical.

Question 2: In an experiment, helminthes infection was given to mice, and population shifts were tracked. It was discovered that as mice got worse, their numbers fell. This connection is an illustration of ________.

Parasitism (Correct answer)
Competition
Commensalism
Mutualism

Correct answer: Parasitism

Parasitism is a symbiotic relationship where one organism, the parasite (in this case, helminthes), benefits at the expense of the other organism, the host (the mice). The observation that the mice's condition worsened and their numbers fell due to the infection clearly indicates that the helminthes are harming the mice, which is the defining characteristic of a parasitic relationship.

Question 3: The existence of ________ in plant cells sets them apart from animal ones.

Cytoplasm
Cell wall (Correct answer)
Cell membrane
Nucleus

Correct answer: Cell wall

Plant cells are uniquely characterized by the presence of a rigid cell wall, primarily composed of cellulose, located outside the cell membrane. This structure provides essential support, protection, and helps maintain cell shape. Animal cells, in contrast, lack a cell wall, relying solely on their cell membrane for their outermost boundary.

Question 4: Which two different types of chemicals are involved in translation?

mRNA and protein (Correct answer)
mRNA and DNA
DNA and tRNA
RNA and DNA

Correct answer: mRNA and protein

Translation is the biological process where the genetic information encoded in messenger RNA (mRNA) is used to synthesize proteins. During this process, ribosomes read the mRNA sequence, and transfer RNA (tRNA) molecules bring specific amino acids, which are then linked together to form a polypeptide chain, ultimately creating a protein. Thus, mRNA provides the template, and proteins are the final product.

Question 5: Which of the following is not a part of the endocrine system?

heart
liver
Testis (Correct answer)
lung

Correct answer: Testis

The endocrine system comprises glands that secrete hormones directly into the bloodstream to regulate various bodily functions. While the heart and liver have some endocrine functions (e.g., producing ANP and IGF-1, respectively), and the testis is a major endocrine gland producing testosterone, the lung's primary role is gas exchange. Although it has some metabolic functions, it is not typically classified as a primary endocrine gland in the same manner as the testis.

Question 6: Which of the groups below has the fewest species, out of the following?

Phylum
Genus (Correct answer)
Order
Kingdom

Correct answer: Genus

The biological classification system organizes living organisms into a hierarchical structure, moving from broader to more specific categories. The order of these taxonomic ranks is Kingdom, Phylum, Class, Order, Family, Genus, and Species. Among the given options, Genus is the most specific category, meaning it contains the fewest species compared to Phylum, Order, or Kingdom.

Question 7: Which of the following best describes how a fertilized egg develops?

Zygote-embryo-blastula-morula
Zygote-morula-blastula-embryo (Correct answer)
Zygote-blastula-morula-embryo
Morula-blastula-zygote-embryo

Correct answer: Zygote-morula-blastula-embryo

After fertilization, the single-celled zygote undergoes rapid cell division, a process called cleavage, to form a solid ball of cells known as a morula. The morula then develops into a hollow structure called a blastula (or blastocyst in mammals). This blastula subsequently implants and further differentiates into an embryo, establishing the correct developmental sequence.

Question 8: The location of protein synthesis is which of the following?

Vacuoles
Cell wall
RNA polymerase
Ribosomes (Correct answer)

Correct answer: Ribosomes

Ribosomes are cellular organelles responsible for protein synthesis, a process known as translation. They read the genetic code carried by messenger RNA (mRNA) and facilitate the assembly of amino acids into polypeptide chains. This crucial function makes ribosomes the primary site where proteins are manufactured within the cell.

Question 9: Blood typing is frequently used to establish biological paternity. X, Y, and Z are three males that could be the fathers of a child who has a blood type B. The mother's blood type is O, according to a blood test. Which blood type must a potential father have in order to rule them out as a parent?

B
A (Correct answer)
AB
None of the above

Correct answer: A

The child has blood type B, and the mother has blood type O (genotype ii). This means the child inherited an 'i' allele from the mother and an I^B allele from the father. Therefore, the father must possess at least one I^B allele. A man with blood type A (genotype I^A I^A or I^A i) cannot contribute an I^B allele, thus ruling him out as the biological father.

Question 10: It is known as _________ when genetic material is transferred between a pair of chromosomes.

Translocation (Correct answer)
Substitution
Transcription
Transduction

Correct answer: Translocation

Translocation is a type of chromosomal abnormality where a segment of one chromosome breaks off and attaches to a different, non-homologous chromosome. This transfer of genetic material between non-homologous chromosomes can lead to changes in gene dosage or expression, often with significant genetic consequences.

Question 11: A researcher is looking into how the qualities of eye color and hair color, which are encoded by two distinct genes, are inherited. Green eyes are subordinate to brown eyes, while brunette hair is preferred to blond hair. What is the odds that a child will be born with green eyes and blond hair if parent A is homozygous for both brown eyes and brunette hair and parent B is heterozygous for both brown eye color and brunette hair?

0% (Correct answer)
15%
20%
25%

Correct answer: 0%

Let brown eyes (B) be dominant to green eyes (b), and brunette hair (H) be dominant to blond hair (h). Parent A is homozygous for both dominant traits (BBHH), meaning they can only pass on 'B' and 'H' alleles. For a child to have green eyes (bb) and blond hair (hh), they must inherit 'b' and 'h' alleles from both parents. Since Parent A cannot contribute 'b' or 'h' alleles, the probability of having a child with green eyes and blond hair is 0%.

Free IB Biology Questions and Answers

A DNA mutation known as a ___________ alters the DNA sequence but does not modify the amino acids in a protein.