CHAPTER-9 HEREDITY AND EVOLUTION

Explanation:

Trait B is more likely to arise early than trait A since it has already existed and reproduced in a larger proportion of the population.

Explanation:

Genetic variants allow the species to better adapt to environmental changes. Moreover, it is a crucial evolutionary factor since it permits the frequency of alleles to rise or decrease through natural selection. These variances will decide whether the species is extinct or continues to exist.

Explanation:

Mendel's work on the mono-hybrid cross demonstrated that characteristics might be either dominant or recessive. He conducted the experiment by crossing tall (TT) pea plants with dwarf (tt) pea plants. The F1 (or filial) generation was represented by the plants that developed following fertilization. The F1 plants were all rather tall. Mendel then proceeded to self-pollinate the filial generation plants, resulting in one-quarter of dwarf plants in the F2 generation. Mendel deduced from this experiment that the F1 tall plants were not true-breeding; rather, they possessed characteristics for both tall and dwarf heights. Because the characteristics for tallness were dominant over the ones for dwarfness, a fraction of the plants were tall. This reinforces the idea that qualities can be dominant or recessive.

Explanation:

Mendel's dihybrid cross experiment demonstrates that characteristics are inherited separately. The experiment required him to use two traits: seed form and seed colour. The colour yellow (YY) dominates over the colour green (yy), and the round shape (RR) dominates over the wrinkled form (rr). The dihybrid cross's F2 progeny had a phenotypic ratio of 9:3:3:1; hence, there were 9 plants with round yellow (RRYY) seeds, 3 plants with round green (RRyy) seeds, 3 plants with wrinkled yellow (rrYY) seeds, and one plant with wrinkled green seeds (rryy). He also saw that the wrinkled greens and round yellows are paternal pairings, but the round green and wrinkled yellow are new. A dihybrid cross of two seeds with dominant characteristics (RRYY) and non-dominant traits (rryy) produced four kinds of gametes (RY, Ry, rY and ry). This indicates that each gamete segregates independently of the others, with a frequency of 25% of the total gametes generated.

Explanation:

The information provided is insufficient to determine whether blood group A or O is predominate. In ABO blood, blood type A is always dominant, while blood type O is always recessive. In this case, the father's blood group may be AA (homozygous) or AO (heterozygous), but the mother's blood group may be OA or OO.

Explanation:

Males decide the sex of the offspring in humans. Men are born with XY chromosomes, whereas females are born with XX chromosomes. As a result, if:

• When the male and female X chromosomes join, the mother gives birth to a daughter.

• When the male's Y chromosome joins with the female's X chromosome, a son is born.

Explanation:

An individual characteristic might boost a population in two ways:

(a) Natural selection: If a characteristic is helpful to a population, it will naturally increase.

Mosquitoes that are resistant to a specific insecticide, for example, will pass on their genes to subsequent generations, making them resistant as well. Mosquitoes that are impacted by the insecticide die.

(b) Genetic drift: If a species is wiped out by a catastrophic catastrophe, the remaining group can pass on its characteristics to future generations. This might lead to an increase in the characteristic of the population.

Explanation:

Changes in the DNA of germ cells do not reflect changes gained throughout a lifetime, hence traits acquired during a lifetime cannot be transferred by subsequent generations. A football player, for example, cannot pass on his abilities to his children since they are restricted to non-reproductive cells.

Explanation:

The genetic pool of the species shrinks as the size of the tiger population shrinks. This limits the genetic variants that can be introduced into the tigers' genetic composition. This lack of diversity will have catastrophic consequences. For example, if an infection spreads across the tiger population, it has the potential to wipe out the whole species, perhaps leading to extinction.

Explanation:

The following factors would result in the emergence of a new species:

(a) Mutation. 

(b) Genetic drift. 

(c) Natural selection. 

(d) Geographical isolation.

(e) Generative isolation over lengthy periods of time.

(f) Environmental variables affecting isolated populations.

(g) Quantum of genetic variants transmissible from one generation to the next.

Explanation:

Geographic isolation is typically not a key effect in plant pollination since no new characteristic will become part of the genetic makeup of a self-pollinating plant species. Nonetheless, there is a chance that some environmental changes will cause some deviations.

Explanation:

Geographic isolation cannot be regarded as a concern in asexually reproducing organisms. This is because meiosis does not occur during asexual means of reproduction.

Explanation:

As an example, consider humans and chimps. Chimpanzees can show a wide range of emotions, such as laughing or smiling, which was previously regarded to be a capability exclusive to humans. The grin is associated with limbic system activation, in which the orbicularis oculi muscle automatically contracts and lifts the cheeks, generating wrinkles around the eyes. This means that the grin is real and genuine. Surprisingly, this form of reaction is known as the Duchenne grin. Furthermore, chimps and humans share 98.6% of our DNA, implying that humans and chimps shared a common ancestor long ago. It's also worth noting that chimps are the closest living cousins to humans.

Explanation:

Because they do not share a common ancestor, the wings of a butterfly and a bat cannot be called homologous organs. Despite the fact that both structures help in flight, they originated independently. To demonstrate this, a butterfly's wings are made up of two chitinous membranes, but a bat's wings are made up of a skeletal skeleton replete with blood arteries. As a result, these are similar rather than comparable organs.

Explanation:

The preserved remnants of animals, plants, or other species that died out millions of years ago are known as fossils. These fossils provide information on many extinct organisms as well as insights into how evolution may have occurred. Fossils can help us comprehend how a creature lived and what it could have looked like. Most crucially, we can correlate with both fossils and living creatures to better comprehend their interactions. For example, scientists were able to retrieve protein sequences from the T-rex, confirming its avian ancestry. This suggests that birds are the closest living cousins of (avian) dinosaurs. Furthermore, the pattern of fossil distribution reveals the time in history when certain species evolved or became extinct.

Explanation:

While humans differ in colour and look, their genetic makeup is similar to that of any other human. One of the theories proposed for our significant changes is that they are the result of evolutionary pressure, where the necessity to be clearly recognized drove us to have drastically varied looks.

Explanation:

Environmental demands and pressures influence body design. As a result, we cannot say that one creature has a better body than another. Fish, for example, have evolved a streamlined shape because it is best adapted to an aquatic habitat. A spider or chimpanzee, on the other hand, maybe ill-equipped to live in such watery conditions.

Explanation:

Correct answer – (c)

TtWW might be the tall parent's genetic makeup. Because half of the progenies are short, this means that the parent plant has a collection of short genes as well; all progenies bore violet flowers, indicating that violet is dominant over white.

Explanation:

Correct answer – (d)

Homologous organs have the same origin as the preceding organs but perform distinct roles. Homologous organs are organs from different species that have similar fundamental architecture but diverse functions. The flippers of a whale, the forelimbs of a frog, and the forelimbs of a man, for example, have the same fundamental anatomy but serve distinct roles, which is why they are referred to as homologous organs.

Explanation:

Correct answer – (a)

Humans and chimpanzees are linked since they are members of the same order (Primates) and family (Hominidae). Nonetheless, regardless of race, a schoolboy is still a Homo sapien.

Explanation:

To determine whether a characteristic is dominant or recessive, at least three generations must be studied. As a result, determining whether a given characteristic is dominant or recessive is impossible.

Explanation:

Taxonomy and evolution are two topics of biology that are closely intertwined. Evolution is concerned with how organisms evolve, whereas classification is concerned with determining how two species are linked to one another. Evolution and fossil data, for example, lead to Australopithecus afarensis as one of our oldest ancestors. And categorization tells us that Australopithecus afarensis is a member of the genus Homo, which includes contemporary humans.

Explanation:

Homologous organs are those that share the same fundamental structural design and origin but serve distinct roles. Human forelimbs, for example, are physically similar to bat wings.

Analogous organs are those that have a different structural architecture and origin but execute comparable tasks. For instance, bird and insect wings.

Explanation:

The colour of a dog's coat is determined by a specific set of genes. There are at least eleven recognized sequence series (A, B, C, D, E, F, G, M, P, S, T) that determine a dog's colour. Each of a dog's parents gives it one copy. A dog in the B series, for example, is genetically black or brown. Assuming one parent is homozygous black (BB), while the other is homozygous brown (bb).

In this situation, all of the children will be heterozygous (Bb).

Because black (B) is dominant, all offspring will be black. They will, however, carry both B and b alleles. When such heterozygous pups are bred, they will give birth to 25 homozygous blacks (BB), 15 heterozygous blacks (Bb), and 25 homozygous browns (bb).

Explanation:

Fossils provide information about: 

(a) the creature and its paleobiology.

(b) Even an organism's behaviour may be determined to some extent (for example, palaeontologists discovered a site containing over 10,000 skeletons of a dinosaur called Hadrosaurus). This suggests that the dinosaur lived in groups.

(c) Fossils also give information on the evolution of animals and plants (for instance, palaeontologists have discovered that whales had evolved from goat-sized land-dwelling animals called Pakicetus).

Explanation:

Stanley L. Miller and Harold C. Urey's experiment, undertaken in 1953, revealed evidence for the creation of life from inanimate substances. They produced an artificial environment resembling the early Earth's atmosphere, complete with ammonia, hydrogen, and other gases known to have existed during the primordial Earth.

This gas mixture was held at a temperature just below 100 ° C. Sparks was also created to resemble lightning, which was considered to be prevalent at the time. He was able to produce 11 of the 20 amino acids essential for life at the end of the experiment.

Explanation:

Sexual reproduction results in several viable variants for the following reasons:

(a) A mistake in DNA copying (though it was rare)

(b) Segregation of paternal and maternal chromosomes at random during sex cell development.

(c) The exchange of genetic material between homologous chromosomes during gamete development.

(d) Variation accumulated via reproduction generation after generation, and natural selection produced a wide range of variety.

(e) Because there is only one parent engaged in asexual reproduction, diversity is severely constrained. As a result, the offspring is genetically identical to the parent.

Explanation:

The kids inherit an identical number of chromosomes from both parents, ensuring equal genetic input from both parents. There are 23 pairs of chromosomes, however, not all of them are coupled. The 22 pairs are known as autosomes, whereas the remaining 1 pair is known as sex chromosomes (represented as X and Y.)

Females have two sets of X-chromosomes, whereas men have one X-chromosome and one Y-chromosome.

Fertilization occurs during the reproduction process, where the male gamete fuses with the female gamete, resulting in the development of a diploid zygote. Also, both parents contribute equally to the zygote's genetic material. The male provides 22 autosomes as well as one X or Y chromosome. The female provides 22 autosomes as well as one X-chromosome.

Explanation:

Only variants give an advantage to individual creatures that will survive in a community, according to the statement. Variations that promote heat resistance in bacteria, for example, are particularly important for survival if they find themselves in a setting with a rapid increase in ambient temperature. For the bacteria, this will be the difference between life and death.