Mix Examples - Heredity and Evolution Questions in English

(A) Natural selection is a key mechanism of evolution. It acts on the heritable variations within a population,favoring individuals with traits that provide a survival or reproductive advantage in a specific environment. Over generations,these advantageous traits become more common,leading to adaptations that better suit the population to its environment,thereby directing the course of evolution.

(B) The statement is $False$.
Experiences acquired by an individual during its lifetime are known as acquired traits.
Acquired traits do not cause any change in the $DNA$ of the germ cells (reproductive cells).
Since only changes in the $DNA$ of germ cells are inherited by the progeny,acquired experiences cannot be passed on to the next generation.

(A) The statement is $True$. Fossils are the preserved remains,impressions,or traces of organisms that lived in the past. These are found in sedimentary rocks and provide evidence for the process of evolution.

(B) The statement is $False$. While relative dating (often based on fossil layers) and carbon dating (radiometric dating) are methods used to determine the age of fossils and geological strata, they are not methods to 'know about evolution' in the sense of explaining the mechanisms of evolutionary change. They are tools used to establish the chronological sequence of life forms, which provides evidence for evolution, but they do not explain the process of evolution itself.

(B) The differences found among individuals of the same species are known as $Variation$.
$Variation$ refers to the genetic differences between individuals of the same species, which arise due to sexual reproduction, genetic recombination, and mutations.
These variations are the raw material for evolution, as they provide the basis for natural selection to act upon.

(C) Heredity is the process by which traits or features are passed from parents to their offspring.
This transmission of genetic information ensures the continuity of characteristics from one generation to the next.
Evolution refers to the gradual change in inherited traits over many generations.
Mutation refers to a sudden change in the $DNA$ sequence.
Therefore,the correct term for the continuity of features is heredity.

(B) Gregor Johann Mendel,known as the father of genetics,conducted his pioneering experiments on the garden pea plant. The scientific name of the garden pea is $Pisum$ $sativum$. He chose this plant because it has several contrasting traits,a short life cycle,and is easy to cross-pollinate.

(C) In Mendel's monohybrid cross,the parent generation $(P)$ consisted of a homozygous tall plant $(TT)$ and a homozygous dwarf plant $(tt)$.
The $F_{1}$ generation resulted in all heterozygous tall plants $(Tt)$.
When the $F_{1}$ plants were self-pollinated $(Tt \times Tt)$,the $F_{2}$ generation produced genotypes in the ratio $1 TT : 2 Tt : 1 tt$.
Phenotypically,this corresponds to $3$ tall plants and $1$ dwarf plant.
The ratio of dwarf plants is $1$ out of $4$,which is $25\, \%$.

(C) In human beings, sex determination is a genetic process.
Humans have $23$ pairs of chromosomes.
Out of these, $22$ pairs are autosomes, and the $23$rd pair consists of sex chromosomes ($XX$ in females and $XY$ in males).
These chromosomes carry specific $genes$ that dictate the development of male or female reproductive organs.
Therefore, sex is determined by the $genes$ present on the sex chromosomes.

(C) Scientific evidence,including fossil records and genetic studies,indicates that modern humans $(Homo\,sapiens)$ originated in Africa.
Genetic diversity studies show that the greatest genetic variation is found among African populations,which supports the 'Out of Africa' theory.
This theory suggests that early humans migrated from Africa to other parts of the world over thousands of years.

(A) Organs that have a similar basic structural design and developmental origin but perform different functions are known as $Homologous$ $organs$.
These organs provide evidence for divergent evolution,as they suggest a common ancestry.
Examples include the forelimbs of humans,whales,and bats,which share the same skeletal structure but are adapted for different functions like grasping,swimming,and flying,respectively.

(B) The Earth's crust is formed in layers,where the deeper layers represent older geological periods and the upper layers represent more recent periods. Therefore,if a fossil is found in a deeper layer,it indicates that the organism lived and became extinct a long time ago,specifically thousands of years ago.

(B) Speciation is the evolutionary process by which populations evolve to become distinct species.
$(i)$ Significant changes in the $DNA$ of germ cells (mutations) lead to variations that can be inherited,which is a primary driver of speciation.
$(ii)$ If there is no change in the genetic material,no new variations arise,and thus no new species can be formed.
$(iii)$ Reproductive isolation,where mating does not take place between two groups,prevents gene flow and allows them to diverge into separate species.
Therefore,both $(i)$ and $(iii)$ contribute to the formation of new species.

(C) Homologous organs are those organs that have the same basic structural design and developmental origin in different species,even though they may perform different functions.
These organs provide evidence for evolution because they suggest that the organisms sharing these structures have inherited them from a common ancestor.
For example,the forelimbs of humans,whales,bats,and cheetahs have the same basic bone structure (humerus,radius,ulna,carpals,metacarpals,and phalanges),indicating a common evolutionary origin.

(C) Homologous organs are those that have the same basic structural design and developmental origin but perform different functions.
$A$,$B$,and $D$ represent structures with similar anatomical origins (forelimbs or modified forelimbs) adapted for different functions like walking,swimming,or flying.
However,the wings of butterflies (insects) and the wings of bats (mammals) are analogous organs.
They perform the same function (flying) but have different structural designs and evolutionary origins (butterfly wings are outgrowths of the exoskeleton,while bat wings are modified forelimbs).
Therefore,the wings of butterflies and bats are not homologous.

(A) The differences that arise among individuals of the same species are known as $Variation$.
$Variation$ refers to the genetic or phenotypic differences between individuals of a population.
$Evolution$ is the gradual change in the heritable characteristics of biological populations over successive generations.
$Heredity$ and $Inheritance$ refer to the passing of traits from parents to offspring.

(C) Variation is the degree by which progeny differ from their parents.
In asexual reproduction,the offspring are genetically identical to the parent,resulting in very little or no variation.
In sexual reproduction,the fusion of gametes from two different parents involves the recombination of genetic material and the process of meiosis.
This leads to significant genetic diversity and a higher degree of variation among the offspring compared to asexual reproduction.

(B) In sexually reproducing organisms, gametes (sperm and egg cells) are haploid cells containing half the number of chromosomes compared to the parent cell.
This reduction in chromosome number is achieved through a specialized type of cell division called $Meiosis$.
During $Meiosis$, a diploid parent cell undergoes two successive divisions to produce four haploid daughter cells, which then differentiate into gametes.
$Mitosis$ is involved in growth and repair, while $Multiple fission$ and $Fragmentation$ are types of asexual reproduction.

(B) Genetic traits are transmitted from parents to offspring through the $DNA$ present in the gametes (sperm and egg). When fertilization occurs,the male and female gametes fuse to form a $Zygote$. This $Zygote$ contains the combined genetic material from both parents,which determines the traits of the future offspring. Therefore,the transmission of genetic traits occurs at the time of the formation of the $Zygote$.

(A) The process by which traits or characters are passed from parents to their offspring is known as $Heredity$ or $Inheritance$.
$Evolution$ refers to the gradual change in the inherited traits of a population over successive generations.
$Variation$ refers to the differences in characteristics among individuals of the same species.
Therefore, the correct term for the transmission of characters is $Heredity$.

(C) The differences observed among individuals of the same species are referred to as $Variation$.
$Heredity$ refers to the transmission of traits from parents to offspring.
$Evolution$ is the gradual change in the heritable characteristics of biological populations over successive generations.
$Similarity$ refers to the likeness between individuals,which is the opposite of variation.
Therefore,the correct term for individual differences is $Variation$.

(B) Variation refers to the differences in characteristics among individuals of the same species.
In sexually reproducing organisms,variation is primarily caused by the recombination of genes during meiosis and the occurrence of mutations.
Genes are the units of heredity that carry information from parents to offspring.
Changes in the $DNA$ sequence of genes,known as mutations,or the shuffling of alleles during sexual reproduction,lead to genetic variation.
Therefore,genes are responsible for the variation observed in populations.

(A) The branch of biology that deals with the study of heredity and variation is known as $Genetics$.
$Heredity$ refers to the transmission of characters from parents to offspring,while $variation$ refers to the differences between individuals of the same species.
$Evolution$ is the study of the gradual development of organisms over time.
$Taxonomy$ is the branch of science concerned with the classification of organisms.
Therefore,the correct option is $A$.

(B) Gregor Johann Mendel is known as the 'Father of Genetics'.
He was the first scientist to conduct a systematic series of experiments on pea plants $(Pisum \, sativum)$ to understand the laws of inheritance.
Through his experiments, he demonstrated how traits are passed from parents to offspring (inherited traits) and distinguished them from acquired traits, which are not passed on to the next generation.

(B) The $DNA$ $(Deoxyribonucleic \text{ acid})$ molecule acts as the primary genetic material in most living organisms.
It contains the coded instructions (genes) necessary for the development, functioning, growth, and reproduction of organisms.
During reproduction, $DNA$ is replicated and passed from parents to offspring, thereby ensuring the transmission of genetic information from one generation to the next.

(B) According to Mendel's Law of Dominance,when a pure tall plant $(TT)$ is crossed with a pure dwarf plant $(tt)$,the $F_{1}$ generation offspring are all heterozygous tall $(Tt)$.
Since the allele for tallness $(T)$ is dominant over the allele for dwarfness $(t)$,all plants in the $F_{1}$ generation will express the tall phenotype.

(A) In Mendel's monohybrid cross,the $F_1$ generation consists of all heterozygous tall plants $(Tt)$.
When these $F_1$ plants are self-pollinated $(Tt \times Tt)$,the resulting $F_2$ generation follows the Mendelian ratio of $3:1$ for the phenotype.
This means $75 \%$ of the plants are tall (genotypes $TT$ and $Tt$) and $25 \%$ of the plants are dwarf (genotype $tt$).

(D) When a pure tall $(TT)$ pea plant is crossed with a pure dwarf $(tt)$ pea plant,the $F_{1}$ generation consists of all heterozygous tall $(Tt)$ plants.
Since all $F_{1}$ plants are heterozygous $(Tt)$,they are neither pure tall nor pure dwarf.
Therefore,the statements that some $F_{1}$ plants are pure tall or pure dwarf are incorrect.
In the context of this multiple-choice question,both options $C$ and $D$ are technically incorrect,but $D$ is the most commonly cited incorrect statement in this specific problem set.

(A) In $Gregor \text{ } Mendel's$ experiments with pea plants $(Pisum \text{ } sativum)$, he observed that when a pure tall plant is crossed with a pure dwarf plant, all $F_1$ generation offspring are tall. This indicates that the allele for tallness $(T)$ is dominant over the allele for dwarfness $(t)$. Therefore, tallness is the dominant trait.

(B) In pea plants,the trait for tallness is dominant over the trait for dwarfness.
According to Mendel's law of dominance,a dominant trait is expressed in both the homozygous condition $(TT)$ and the heterozygous condition $(Tt)$.
Therefore,the phenotype of tallness is exhibited by both the homozygous dominant genotype $(TT)$ and the heterozygous genotype $(Tt)$.

(D) In pea plants,height is determined by alleles '$T$' (tall) and '$t$' (dwarf).
'$T$' is dominant over '$t$'.
$A$ tall plant can have a genotype of '$TT$' (homozygous dominant) or '$Tt$' (heterozygous).
$A$ dwarf plant must have a genotype of '$tt$' (homozygous recessive).
Therefore,the statement that a tall plant cannot have a '$Tt$' genotype is incorrect,as '$Tt$' results in a tall phenotype due to the dominance of '$T$'.

(A) The unit of heredity is the $Gene$.
Genes are specific segments of $DNA$ located on chromosomes that carry the instructions for synthesizing proteins, which determine the traits of an organism.
They are passed from parents to offspring during reproduction, thereby serving as the fundamental units of inheritance.

(A) Chromosomes are the structures that carry genetic information in the form of $DNA$.
During sexual reproduction,the fusion of male and female gametes (sperm and egg) occurs.
These gametes are specialized cells that contain half the number of chromosomes $(n)$ compared to somatic cells $(2n)$.
When the male gamete fuses with the female gamete during fertilization,the resulting zygote receives one set of chromosomes from each parent,restoring the diploid number $(2n)$.
Therefore,gametes are the vehicles through which chromosomes are transmitted from parents to the offspring.

(C) Genes are the units of inheritance and are responsible for the transmission of hereditary characteristics from parents to offspring. These genes are located on chromosomes. Therefore,chromosomes are considered the carriers of genes.

(B) Genes are the functional units of heredity and are composed of segments of $DNA$. These genes are physically located on the chromosomes within the nucleus of the cell. Each chromosome consists of a long molecule of $DNA$ coiled around proteins called histones. Therefore,the correct location of genes is on the chromosomes.

(C) human somatic cell contains a total of $46$ chromosomes.
These chromosomes are organized into $23$ pairs.
Out of these, $22$ pairs are autosomes and $1$ pair consists of sex chromosomes ($XX$ in females and $XY$ in males).
Therefore, the correct answer is $23$ pairs.

(A) Some species of snails are hermaphrodites,meaning they possess both male and female reproductive organs. In certain species,they can change their sex depending on environmental conditions or population density to facilitate reproduction. Among the given options,the snail is the organism known for this biological capability.

(B) Humans have a total of $46$ chromosomes, which are arranged in $23$ pairs.
Out of these $23$ pairs, $22$ pairs are known as autosomes, which are identical in both males and females.
The $23$rd pair consists of sex chromosomes, which differ between the sexes ($XY$ in males and $XX$ in females).
Therefore, there are $22$ pairs of chromosomes that are equal in both males and females.

(B) Humans have a total of $46$ chromosomes, which are arranged in $23$ pairs.
Out of these $23$ pairs, $22$ pairs are known as autosomes, which are identical in both males and females.
The $23$rd pair consists of sex chromosomes, which differ between the sexes: females have $XX$ and males have $XY$.
Therefore, there are $22$ pairs of chromosomes that are equal in both males and females.

(C) In humans,there are $23$ pairs of chromosomes in total.
Pairs $1$ to $22$ are known as autosomes,which determine somatic characteristics.
The $23^{rd}$ pair is known as the sex chromosomes (allosomes),which determine the biological sex of an individual.
In females,the $23^{rd}$ pair is $XX$,and in males,it is $XY$.

(A) In humans,there are $23$ pairs of chromosomes in each cell.
Out of these,$22$ pairs are autosomes,and the $23$rd pair consists of sex chromosomes.
In human females,the $23$rd pair of sex chromosomes is identical,represented as $XX$.
In human males,the $23$rd pair consists of one $X$ and one $Y$ chromosome,represented as $XY$.

(A) In humans,there are $23$ pairs of chromosomes. The first $22$ pairs are autosomes,which are identical in both males and females. The $23$rd pair is known as the sex chromosomes. In human males,the $23$rd pair consists of one $X$ chromosome and one $Y$ chromosome,represented as $XY$. In human females,the $23$rd pair consists of two $X$ chromosomes,represented as $XX$.

(C) In humans,the sex of an individual is determined by the sex chromosomes.
Females have $XX$ chromosomes and produce gametes (ova) that always carry an $X$ chromosome.
Males have $XY$ chromosomes and produce two types of sperm: those carrying an $X$ chromosome and those carrying a $Y$ chromosome.
When a sperm carrying an $X$ chromosome fertilizes an ovum (which always carries an $X$ chromosome),the resulting zygote will have $XX$ chromosomes.
An individual with $XX$ chromosomes develops into a female.

(A) In humans,sex determination is based on the sex chromosomes. Females have $XX$ chromosomes and males have $XY$ chromosomes.
During gametogenesis,females produce eggs containing only the $X$ chromosome,while males produce sperm containing either the $X$ or the $Y$ chromosome.
When a sperm carrying an $X$ chromosome fertilizes an egg,the resulting zygote is $XX$ (female).
When a sperm carrying a $Y$ chromosome fertilizes an egg,the resulting zygote is $XY$ (male).
Since there is an equal probability of an $X$-bearing sperm or a $Y$-bearing sperm fertilizing the egg,the probability of having a male or female offspring is $50 \%$ each.

(C) In humans,the sex of the baby is determined by the sex chromosomes.
Females have two $X$ chromosomes $(XX)$,so every egg produced by the mother carries an $X$ chromosome.
Males have one $X$ and one $Y$ chromosome $(XY)$.
During spermatogenesis,$50\%$ of the sperms receive an $X$ chromosome and $50\%$ receive a $Y$ chromosome.
If a sperm carrying an $X$ chromosome fertilizes the egg,the zygote will be $XX$ (female).
If a sperm carrying a $Y$ chromosome fertilizes the egg,the zygote will be $XY$ (male).
Therefore,the sperm is the decisive factor because it can carry either an $X$ or a $Y$ sex chromosome.

(D) The correct matching is as follows:
$1$. Acquired trait: Docked tail of a mouse $(c)$. Acquired traits are those developed during the lifetime of an organism and are not inherited.
$2$. Evidence of evolution: Fossils $(d)$. Fossils provide direct evidence for the history of life and evolutionary changes.
$3$. Homologous organs: Wings of a bird and forelimb of a lizard $(b)$. These organs have a similar basic structural design and developmental origin but perform different functions.
$4$. Analogous organs: Wings of a bird and wings of a butterfly $(a)$. These organs perform similar functions but have different structural designs and evolutionary origins.
Therefore,the correct sequence is $(1-c), (2-d), (3-b), (4-a)$.

(A) Organs that perform similar functions and appear similar externally but have different basic anatomical structures and embryonic origins are known as $Analogous$ $organs$.
These organs are a result of $convergent$ $evolution$, where different species evolve similar traits independently to adapt to similar environmental pressures.
For example, the wings of a butterfly and the wings of a bird both serve the function of flight, but their internal skeletal structures are completely different.

(A) The age of fossils can be estimated using the carbon dating method (specifically,radiocarbon dating).
This method relies on the decay of the radioactive isotope $C^{14}$ present in the organic matter of the fossil.
By measuring the ratio of $C^{14}$ to $C^{12}$ in the fossilized remains,scientists can calculate how long ago the organism died.
Therefore,the correct method is the carbon dating method.

(B) The process of determining the age of fossils is known as radiocarbon dating.
This method relies on the radioactive isotope of carbon,which is ${}^{14}C$.
Living organisms absorb carbon from the atmosphere,including a small amount of ${}^{14}C$.
After an organism dies,it stops absorbing carbon,and the ${}^{14}C$ present in its remains begins to decay at a known constant rate.
By measuring the remaining amount of ${}^{14}C$ in a fossil,scientists can calculate how long ago the organism died.

(D) The evolution of eyes is a significant milestone in biological history. Among the given options,$Planaria$ (a flatworm) is the first animal known to possess primitive eyespots called ocelli. These structures are capable of detecting light and dark,allowing the organism to exhibit phototactic behavior. While $Paramoecium$ and $Plasmodium$ are unicellular organisms that lack complex sensory organs,and $Peripatus$ is a more complex arthropod-like organism,$Planaria$ represents the earliest evolutionary stage where rudimentary light-sensing organs appeared.