All Free Biology MCQs with Answers

• A. Convergent evolution
• B. Divergent evolution
• C. Natural selecting
• D. Common ancestory

Explanation: Convergent evolution is a process by which organisms that are not closely related independently evolve similar traits as a result of…

• A. Survival of the fittest
• B. The most fit individuals adapt to their environment better than less fit individuals
• C. Those who eat better, arc healthier, and live longer are the most fit within a population
• D. Preservation of traits that lead to increased survival and reproduction

Explanation: Natural selection is the process by which organisms with traits that are better suited to their environment are more likely to survive and…

• A. Some individuals are more successful in surviving and reproduction than others
• B. Individuals within a population are variable
• C. The survival and reproduction of individuals is not random
• D. The survival and reproduction of individuals are random

Explanation: Survival in the struggle for existence is not random,, but depends in part on the hereditary constitution of the surviving individuals.

• A. Homologous organs are functionally different but structurally alike.
• B. Examples of homologous structures are arms of man, forelimbs of cat and flippers of whale.
• C. Examples of analogous structures are wings of bats, birds and insects.
• D. Analogous organs are functionally different but structurally alike.

Explanation: Analogous organs are those which have different structures, but their function is the same in different organisms.

• A. Hardy-Weinberg
• B. Malthus
• C. Lamarck
• D. Alfred Wallace

Explanation: Alfred Wallace, a young naturalist working in the EastIndies, developed a theory of natural selection essentially identical to Darwin's.

• A. The frequency of alleles does not change within the population.
• B. It reduces the number of heterozygous individuals, preventing beneficial alleles from being efficiently selected.
• C. It increases the number of homozygous individuals, allowing potentially harmful recessive alleles to express themselves more frequently.
• D. All of these.

Explanation: Inbreeding does not alter the allele frequency. In this way, it does not allow the individual to adapt to its environment by changing its…

• A. Which lives 45 years and produces 3 offspring.
• B. Which lives 70 years and produces no offspring.
• C. Which lives 27 years and produces no offspring.
• D. Which lives 36 years and produces 6 offspring.

Explanation: An organism is said to be biologically fit if produces more offspring than other organisms in its population.

• A. The number of offspring produced by the organism.
• B. How much food the organism consumes in its lifetime.
• C. How large the organism grows.
• D. The number of offspring produced by the organism's own offspring.

Explanation: The fitness of an organism is typically determined by its ability to produce offspring that can survive and reproduce themselves, rather…

• A. They have the same organs.
• B. They have similar appearance
• C. They have common ancestors
• D. All of above

Explanation: The correct answer is They have common ancestors. Homology is the similarity between structures in different organisms that are the result…

• A. Dmitri lvanovsky
• B. Dmitry Anuchin
• C. Nikolay Shatsky
• D. Alexander Oparin

Explanation: Primordial soup is a fundamental aspect of the heterotrophic theory of the origin of life, first proposed by Alexander Oparin.

• A. Darwin's theory of natural selection.
• B. Lamarck's theory of inheritance of acquired characteristics.
• C. Hardy-Weinberg principle
• D. None of these options are correct

Explanation: Darwin's theory of natural selection is the correct answer because it describes how species adapt to their environments over time through…

• A. They have the same organs.
• B. They have a similar appearance.
• C. They have common ancestors.
• D. All of the above.

Explanation: The correct answer is that they have common ancestors. Genetic and protein similarities are key indicators of evolutionary relationships…

• A. Every man and every woman likes my father; he is the perfect gentleman.
• B. Every man and every woman likes my father, he is the most perfect gentleman.
• C. Every man and every woman likes my father: him being the perfect gentleman.
• D. Every man and every woman likes my father which is the perfect gentleman.

Explanation: This option is correct. The semicolon (;) correctly separates two related but independent clauses.

• A. Gibberellins - Leaf fall
• B. Cytokinin - Cell division
• C. IAA - Cell wall elongation
• D. Abscisic acid - Stomatal closure

Explanation: Gibberellins promote growth, not leaf fall.

• A. Due to the less negative water potential of the external environment than the cell
• B. Due to the more negative water potential of the external environment than the cell
• C. Due to the less positive water potential of the external environment than the cell
• D. Due to more positive water potential of the external environment than the cell

Explanation: When salt is applied to vegetables, it dissolves and creates a solution with a more negative water potential.

• A. Ernst munch
• B. Robert Hooke
• C. Mohl
• D. Darwin

Explanation: The starch-sugar hypothesis is one hypothesis that explains the opening and closing of stomata. It was proposed by German botanist H. Mohl.

• A. Ernst Munch
• B. Charles Darwin
• C. Robert Brown
• D. Robert Hooke

Explanation: The pressure-flow hypothesis was formulated by Ernst Münch in 1930.The pressure flow hypothesis, also known as the mass flow hypothesis…

• A. Companion cells
• B. Sieve tube members
• C. Vessels
• D. Parenchyma

Explanation: Phloem components are sieve tubes, companion cells, phloem fibres, and phloem parenchyma cells.The main components of the xylem are the…

• A. Plasmodcsmala
• B. Cortex
• C. Endodermis
• D. Pith

Explanation: In roots, the apoplast pathway of water is disrupted when water reaches the endodermis.

• A. Hormonal signals affecting guard cells
• B. Change in turgor pressure of guard cells
• C. Role in gaseous exchange
• D. Impact of plant respiration

Explanation: The correct answer is that the opening and closing of stomata are driven by changes in the turgor pressure of guard cells (Option B).