Evolutionary Mechanisms MCQ Quiz in मल्याळम - Objective Question with Answer for Evolutionary Mechanisms - സൗജന്യ PDF ഡൗൺലോഡ് ചെയ്യുക

Concept:

• If the concept of evolution has to be encapsulated in a single word, that word must be adaptation or, in a few more words, selection for the fittest.
• One way to show adaptation, dating back to Darwin's On the Origin of Species, is convergent evolution.
• When multiple taxa independently evolved the same trait to cope with the same, or similar, environmental pressures, the trait is likely adaptive in that environment.

Explanation:

• Convergent evolution is a fact in which distinct lineages independently evolve similar trait has fascinated evolutionary biologists for centuries in large part because convergent evolution is often thought to represent a visible manifestation of the power of natural selection.
• Many examples of phenotypic convergence including limbless body plans in burrowing species, drug resistance in pathogens, and antifreeze proteins in arctic and antarctic fishes have similarly intuitive explanations as the result of adaptation to shared environments.
• Convergent evolution can serve as a valuable process for repeated experiments in evolution, and understanding how convergent traits evolve, especially at the molecular level, has the potential to inform general rules about adaptation.
•  In the past decade, low-cost, high-throughput sequencing has ushered in an era of widespread genome sequencing in model and non-model organisms alike, bringing vast new data to bear on understanding convergence at the molecular level.

Concept:

• Charles Darwin's second-most significant hypothesis, proposed in 1871, is sexual selection.
• Sexual selection explains why features that do not improve an individual's chances of survival but are nonetheless selected are not adaptive.
• Only sexual selection can produce these non-adaptive, sexual features, which can be advantageous to the bearer by boosting the individual's reproductive success, even at the expense of their mortality.

Explanation:

• The differences in features between the sexes can be used to identify the impact of significant sexual selection among them.
• Stronger sexual selection occurs for that sex the higher the reproductive variance.
• The highest-performing man will have the most variance if there is an unequal distribution of reproduction among males; as a result, this feature is more strongly sexually selected than that of other sexes.
• Due of their small amount of gametes, females' reproductive success will have a low variance and little sexual selection.
• It is crucial to remember that, in accordance with the sexual selection definition, high sexual selection will result in accentuated dimorphic features in the sex with the biggest variance.

The correct answer is Option 3 i.e.A, B and D

Concept:

• Genetic drift is a random process that can occur in small populations where chance events can lead to changes in the frequency of certain alleles.
• It is one of the mechanisms of evolution, along with natural selection, mutation, and migration.
• The basic idea behind genetic drift is that in small populations, the frequency of alleles can fluctuate randomly from generation to generation due to chance events.
• For example, in a small population, if a few individuals with a particular allele fail to reproduce or do not pass on that allele to their offspring, that allele may become less common or even disappear altogether from the population.
• Conversely, if a few individuals with a particular allele happen to have a lot of offspring, that allele may become more common in the population.

Important Points

Statement A - CORRECT

• Genetic drift is a random process that can occur in small populations where chance events can lead to the loss of certain alleles.
• In other words, some alleles may not be passed on to the next generation due to random sampling.
• This can lead to a reduction in genetic diversity over time, which can have long-term consequences for the population.

 Statement B - CORRECT

• Population bottleneck occurs when a population experiences a drastic reduction in size due to some random event, such as natural disasters, diseases, or human activities.
• As a result of the bottleneck, the remaining population has less genetic diversity than the original population, and certain alleles may become overrepresented or underrepresented.
• Genetic drift is one of the mechanisms that can cause a population bottleneck.

Statement C - INCORRECT

• Genetic drift can still occur in populations of any size, although its effects may be less pronounced in larger populations.
• Once a population has gone through a bottleneck, genetic drift can continue to affect the population if it remains small or if it experiences further reductions in size.

Statement D - CORRECT

• The founder effect occurs when a small group of individuals from a larger population establish a new population in a new location.
• The genetic makeup of the new population can be different from the original population, depending on which individuals migrated and which alleles they carried.
• Genetic drift is one of the mechanisms that can cause a founder effect, as the small size of the new population means that chance events can have a larger impact on the frequency of alleles.

Therefore, the correct combination is Option 3:  A, B, and D.

The correct answer is Option 2 i.e.(i), (iii) and (iv)

Key Points

• A species is said to be extinct when the last known member of the species dies without leaving behind any genetic successor.

Types of extinction - 

1. Phyletic extinction or pseudo-extinction - It refers to the phenomenon where one species disappear but it leaves behind more evolved species in its place.
2. Terminal extinction - It refers to the phenomenon where species is disappeared without leaving behind any descendants. 

Causes of species extinction - 

1. Small population size -
   • Small population sizes are at higher risk of extinction as their reproductive fitness is low as compared to individuals from the large population.
2. Inbreeding and increase in homozygosity -
   • With an increase in inbreeding, homozygosity increases among the individuals of the population which results in a decrease in reproductive fitness and eventually the species disappear.
3. Destruction of natural habitat -
   • If the natural habitat of the species is destroyed, members of that species struggle for existence because their niches are also destroyed.
   • They also face large competition when they are utilizing resources from niches of other species.
4. Demographic change -
   • ​A change in the demographic pattern can result in the extinction of species.
   • There can be a rapid and drastic demographic change in the population when there is sudden death due to disease, environmental causes, climatic factors, etc.
   • This is true for a population that is smaller in size.
5. Climate change -
   • Climate can affect the population size which in turn will change the demographic structure of the population. 

Explanation:

• Statement (i) -
  • An increase in homozygosity leads to the extinction of the species because it decreases reproductive fitness in the population by increasing the frequency of homozygosity of the harmful allele within the population.
• Statement (ii) -
  • ​Increases in heterozygosity are considered good for the species because it increases reproductive success in the population.
• Statement (iii) -
  • A small size population is at a higher risk of extinction because the change in allelic frequency will have a profound effect on the small population rather than the larger population.
  • Also, environmental hazards pose great harm to the smaller population.
  • There is also a higher chance of inbreeding in the smaller population because of which allelic frequency is affected.
• Statement (iv) -
  • Demographic stochasticity refers to changes in the number of individuals in the population due to death and birth.
  • If there is too much death in the population it will pose species at risk of extinction.
• Statement (v) -
  • The unpredictable spatial-temporal changes in the environmental condition are called environmental stochasticity.
  • A decrease in environmental stochasticity refers to less environmental change, which provides a stable environment for species to grow and flourish.

Hence, the correct answer is Option 2.

The correct answer is Option 3 i.e.r > C/B

Key Points

• Hamilton's rule is a mathematical concept that predicts whether or not a particular behavior will be selected in a population based on the degree of relatedness between individuals and the costs and benefits associated with the behavior.
• It was first proposed by William Hamilton in 1964.
• Altruism is a behavior in which an individual incurs a cost to help another individual, usually a relative or member of their social group, with the expectation that they will receive some benefit in return.
• The evolutionary puzzle of altruism arises because it is difficult to explain how such behaviors can evolve since they appear to reduce the reproductive fitness of the individual performing the behavior.
• According to Hamilton's rule, altruistic behaviors can evolve if the benefits to the recipient, adjusted for the degree of relatedness between the individuals, outweigh the costs to the donor.

The rule can be expressed mathematically as:

rB > C

• where,
  • r is the coefficient of relatedness between the individuals (i.e., the probability that a gene present in the donor is also present in the recipient due to shared ancestry)
  • B is the benefit to the recipient, and C is the cost to the donor.
• If the value of rB is greater than C, then the altruistic behavior is predicted to be favored by natural selection, since the benefit to the recipient, adjusted for relatedness, outweighs the cost to the donor.
• In other words, the individual performing the altruistic behavior is still able to pass on their genes to future generations, even if they themselves do not directly benefit from the behavior.
• Therefore, option 3 (r > C/B) is the correct answer to the given question as it indicates that r, the coefficient of relatedness, is greater than the cost-to-benefit ratio (C/B), meaning that the benefit to the recipient, adjusted for relatedness, is greater than the cost to the donor, and therefore altruistic behavior is predicted to be favored by natural selection.

Concept:

• Sexual reproduction requires two individuals to produce offspring.
•  Sexual reproduction is associated with unique costs.
• Two types of gametes (sperm and eggs) must be made, males and females require specialized body parts to mate with each other, and the two sexes must be able to find each other.
• Yet given that the vast majority of eukaryotic species reproduce sexually, this question has intrigued biologists since the time of Darwin i.e. advantage of sexual reproduction for the perpetuation of a species.

Explanation: 

 Statement A: Sexual reproduction generates genetic heterogeneity through recombination

•  Sexual reproduction allows for greater genetic variation due to genetic recombination.
• Only certain alleles from each parent are passed on, and when a set of genes from one parent mixes with a different set from the other parent, the offspring are never exactly like either of their parents.
• Thus, a hallmark of sexual reproduction is increased genetic variation between successive generations and this statement is true.

Statement B: Sexual reproduction helps in purging ( removal) deleterious mutations

•  Sexual reproduction may facilitate elimination of harmful alleles from a population.
• Sexual reproduction allows for greater mixing of alleles of different genes and thereby may prevent the accumulation of detrimental alleles in a population.
•  The alleles of sexually reproducing populations can be reassorted from generation to generation, thereby producing succeeding generations in which the detrimental alleles are lost from the population.
• thus this statement is true

 Statement C: Sexual reproduction evolved to stay evolutionarily ahead of fast evolving internal parasites. 

• The Red Queen hypothesis proposes that hosts with a co-evolving parasite are more likely to reproduce sexually to increase genetic variation in their offspring so they have a greater chance of evading infection.
• Parasites can then evolve quickly and continuously in response to the ongoing evolution of the host’s defenses.
• This host-parasite arms race therefore offers an evolutionary advantage by helping maintain genetic variation in the population.
• thus this statement is true

​

​hence the correct answer is option 4

​

The correct answer is Option 4 i.e.0.15

Concept:

• The gene and genotype frequency of the Mendelian population is constant generation after generation of selection, mutation, migration, or random drift are absent. This is called Hardy Weinbery law.
• Suppose a plant species has two alleles for a gene, A and a, then their frequency is given by 'p' and 'q' respectively.
• According to the Hardy-Weinberg equilibrium
• \(p+q=1\), the sum of allele frequency is always equal to one.
• Also, \(\begin {equation} \begin{split} (p+q)^2&=1\\ p^2 +2pq+q^2 &=1 \end{split} \end {equation}\)
• So, according to the Hardy-Weinberg law, unless there is any factor influencing these frequencies, the frequency of the p and q will remain constant in a population. 
• Factors affecting the equilibrium are as follows:
• Migration - It is the contribution to the gene pool of a population by an individual that has migrated to the population.
• Mutation - it is a sudden change in the characteristics of the organism.
• Selection - It either operates at gametic selection or zygotic selection.
• Randon drift- This is a random change in the gene frequency of the population due to the chance of sampling error. The change is greater in smaller populations as compared to a larger population.

Explanation:

• 8% of the male population is colourblind. 
• Let "X" represent the normal X chromosome while "\(X^h\)" represent the affected X chromosome for the colourblind. 
• In women,
•  \( \begin{equation} \begin {split} XX &= p^2\\ XX^h & =2pq\\ X^hX^h &=q^2 \end {split} \end {equation}\)
•  But since males have only one X chromosome, hence, in males,
• \(\begin {equation} \begin {split} XY &= p \\ X^hY&= q \end {split} \end {equation}\)       
• So, we do not have the heterozygous condition in males.       
• 8% male population is colourblind, so 0.08 proportion of the male population is colourblind. Thus, the frequency of the recessive allele 'q' \(=\frac{8}{100} = 0.08\)
• According to Hardy Weinberg's equilibrium, \(p+q=1\)
• So, the frequency of the dominant allele \(p=1-0.08 = 0.92\)
• Then the frequency of the dominant allele 'p' = 0.92
• Now, we have to find the proportion of the females that are carriers for the colourblind trait, ie., heterozygous.
• The frequency of the heterozygous is given be 2pq
• Hence, the frequency of the heterozygous female is 
• \(\begin{equation} \begin {split} 2pq&= 2\times 0.92 \times 0.08 \\ &= 0.147 \end {split} \end {equation}\)
• So, the frequency of colourblind females =0.15

Hence, the correct answer is Option 4. 

The correct answer is Option 1 i.e. Analogous structures.

Concept:

• When species occupy comparable ecological niches and respond similarly to similar selective pressures, this is known as convergent evolution.
• Analogous structures are traits that result from convergent evolution.
• In contrast to them are "homologous structures," which share a common ancestor.

Explanation:

Option 1:- Analogous structures

• Convergent evolution happens when two creatures that don't share a recent ancestor become increasingly similar as they adapt to the same ecological niche.
• The creatures' convergent phenotypes are known as comparable structures, and they have similar structural shapes
• e.g., such as bird wings and bat wings
• Therefore, Option 1 is correct.

Option 2:- Homologous structures 

• Organs or skeletal components of animals and organisms that are homologous reveal a relationship to a common ancestor because of their similarities.
• The appearance and purpose of these structures need not be identical.
• Therefore, Option 2 is incorrect.

Option 3:- Synapomorphies

• a trait that an original species has and that its evolutionary successors only shared (in a more or less modified form).
• Therefore, Option 3 is incorrect.

Option 4:- Pleiotropic structures

• Pleiotropy is the situation in which a single gene or mutation affects a number of phenotypic features.
• It has wide-ranging effects on evolution, disease, development, and genetics.
• Therefore, Option 4 is incorrect.

The correct answer is A: False, B: True, C: False, D: True

Concept:

• Evolution by natural selection is a fundamental mechanism driving the diversity of life. It favors traits that enhance survival and reproduction in a given environment.
• Adaptation refers to the process where organisms evolve traits that allow them to function better in their environment. However, adaptation does not imply perfection, and various constraints can influence the process.
• The traits we see today are shaped by past environments, and adaptation is not limited to the current environment but reflects historical interactions with selection pressures.
• Natural selection is one of many processes influencing evolution. Other mechanisms, like genetic drift, gene flow, and mutation, also play roles in shaping traits.

Explanation:

• A: False: Adaptation does not imply that organisms are perfectly matched to their current environment. Evolution works on available genetic variation and may lead to traits that are "good enough" rather than perfect. Additionally, environments can change faster than evolution can adapt organisms to them, leaving mismatches.
• B: True: Adaptive traits are shaped by natural selection acting on past environments. Evolution is influenced by historical selection pressures, meaning traits that were advantageous in the past may still persist even if the current environment has changed.
• C: False: While natural selection is a primary mechanism driving adaptation, it is not the only process. Other evolutionary processes, such as genetic drift (random changes in allele frequencies) and gene flow (movement of genes across populations), can also influence traits and their prevalence in populations.
• D: True: Adaptation to current environments may be constrained by adaptations to past environments. For example, traits that evolved for past environments may limit the ability to adapt to new environments, creating evolutionary "trade-offs."

The correct answer is 5.76

Explanation:

• The Hardy-Weinberg equilibrium principle states that allele and genotype frequencies in a population will remain constant from generation to generation in the absence of evolutionary influences.

To calculate the expected genotype frequencies under Hardy-Weinberg equilibrium, we use the formula:

• Frequency of genotype = (frequency of allele 1) × (frequency of allele 2).
• Here, "AaBb" is a genotype that involves heterozygosity for both genes (A and B). For heterozygous genotypes, the calculation combines probabilities of each allele pairing.
• Given Data:
  • Frequency of allele 'a' = 0.2
  • Frequency of allele 'A' = 1 - 0.2 = 0.8
  • Frequency of allele 'b' = 0.1
  • Frequency of allele 'B' = 1 - 0.1 = 0.9
• Genotype AaBb:
  • Since AaBb involves heterozygosity (one dominant and one recessive allele for each gene), the probability can be calculated as follows:
  • Frequency of Aa = 2 × (frequency of A × frequency of a) = 2 × (0.8 × 0.2) = 0.32
  • Frequency of Bb = 2 × (frequency of B × frequency of b) = 2 × (0.9 × 0.1) = 0.18
  • Frequency of AaBb = Frequency of Aa × Frequency of Bb = 0.32 × 0.18 = 0.0576
  • Expected genotype population with AaBb = 5.76%