Chapter 9 Heredity and Evolution Solutions
Question - 21 : - A study found that children with light-colored eyes are likely to have parents with light-colored eyes.
Answer - 21 : - On this basis, can we say anything about whether the light eye color trait is dominant or recessive? Why or why not?
Answer
Knowledge of at least 3 generations is required for finding if an attribute is dominant or recessive. Hence, it is not possible to identify if the given trait is dominant or recessive.
Question - 22 : - How are the areas of study – evolution and classification – interlinked?
Answer - 22 : - Classification and evolution are two related fields of biology. Evolution pertains to how organisms evolve and classification deals with finding out how two species are related to each other. For example, evolution and fossil evidence point to the fact that Australopithecus afarensis is considered one of our earliest ancestors. And classification tells us that Australopithecus afarensis belongs to the genus Homo, which is also the same genus as modern humans.
Question - 23 : - Explain the terms analogous and homologous organs with examples.
Answer - 23 : -
Homologous organs are those organs that have the basic structural design as well as origin, however, serve different functions. For example: The forelimbs of humans and the wings of bats are anatomically similar.
Analogous organs are those organs that have a different structural design as well as origin, however perform similar functions. For example: The wings of birds and insects.
Question - 24 : - Outline a project which aims to find the dominant coat color in dogs.
Answer - 24 : - Dogs have a certain set of genes that govern coat color. There are a minimum of eleven known sequence series (A, B, C, D, E, F, G, M, P, S, T) that influence the colour of a dog. A dog inherits one copy from each of its parents. As an example, within the B series, a dog is genetically black or brown. Assume that one parent is homozygous black (BB), whereas the other parent is homozygous brown (bb).
In this case, all the offsprings are going to be heterozygous (Bb).
Since black (B) is dominant, all the offsprings are going to be black. However, they are going to have each B and b alleles. If such heterozygous pups are crossed, they are going to produce 25 homozygous blacks (BB), 15 heterozygous black (Bb), and 25 homozygous brown (bb) offsprings.
Answer - 25 : -
Fossils give evidence about:
(a) The organism and their paleobiology
(b) Even behaviour of an organism can be deduced to some extent (for example, paleontologists) had unearthed a site with more than 10,000 skeletons of a dinosaur called Hadrosaurus. This implies that the dinosaur lived in herds.
Question - 26 : - What evidence do we have for the origin of life from inanimate matter?
Answer - 26 : -
The evidence on the origin of life from inanimate matter was provided by Stanley L. Miller and Harold C. Urey’s experiment, which was conducted in 1953. They created an artificial environment which was reminiscent of the early earth’s atmosphere – it contained ammonia, hydrogen and other gases which were thought to have existed during primordial earth.
This concoction of gases was kept at a temperature slightly below 100 ° C. Additionally, sparks were generated to simulate lightning, which was also thought to be common during that period. At the end of the experiment, he was able to create 11 out of the 20 amino acids which is required for life.
Question - 27 : - Explain how sexual reproduction gives rise to more viable variations than asexual reproduction.
Answer - 27 : - How does this affect the evolution of those organisms that reproduce sexually?
Answer
Sexual reproduction causes a lot of viable variations because of the following reasons:
(a) Error in copying of DNA (though it was rare)
(b) Random segregation of paternal and maternal chromosome at the time of sex cell formation.
(c) Exchange of genetic material between homologous chromosomes during the formation of gametes.
(d) Accumulation of variations occurred because of reproduction over generation after generation and choice naturally created wide diversity.
(e) In case of asexual reproduction, variation is severely limited as there is only one parent involved. Hence, the offspring is genetically similar to the parent
Question - 28 : - How is the equal genetic contribution of male and female parents ensured in the progeny?
Answer - 28 : -
Equal genetic contribution of male and female parents is ensured in progeny through the inheritance of equal numbers of chromosomes from both parents. There are 23 pairs of chromosomes but not all is paired. The 22 pairs are called autosomes while the remaining 1 pair is called the sex chromosomes (represented as X and Y.)
Females have two sets of X-chromosomes while males have 1 X-chromosome and 1 Y-chromosome.
During the process of reproduction, fertilization takes place, where the male gamete fuses with the female gamete and it results in the formation of a diploid zygote. Furthermore, the zygote receives an equal contribution of genetic material from both parents. The male contributes 22 autosomes plus, 1 X or Y chromosomes. The female contributes 22 autosomes, plus 1 X-chromosome.
Question - 29 : - Only variations that confer an advantage to an individual organism will survive in a population.
Answer - 29 : -
Do you agree with this statement? Why or why not?
Answer
The statement holds true – only variations provide an advantage to individual organisms that will survive in a population. For example, variations that lead to the increase in heat-resistance in bacteria is very useful for survival if it finds itself in an environment where there is a sudden increase in ambient temperature. This will determine the difference between life and death for the bacteria.