"AKC SCIENCE CLASSES"
CLASS 10 TH (CBSE AND MP BOARD)
CHAPTER 09
HEREDITY AND EVOLUTION
EXERCISE QUESTIONS AND ANSWERS
Q.01:- A Mendelian experiment consisted of breeding tall pea plants bearing violet flowers with short pea plants bearing white flowers. The progeny all bore violet flowers, but almost half of them were short. This suggests that the genetic make-up of the tall parent can be depicted as :-
(a) TTWW
(b) TTww
(c) TtWW
(d) TtWw
Ans:- (c) TtWW
TtWW (tall, violet) ✖ ttww (short, white)
Genotypic ratio :- TtWw : ttWw = 1 : 1
Phenotypic ratio :- Tall, Violet : Short, Violet = 1 : 1
Q.02:- An example of homologous organs is
(a) our arm and a dog's fore-leg
(b) our teeth and an elephant's tusks
(c) potato and runners of grass
(d) all of the above
Ans:- (d) All of the above because all the pairs are similar in structure and origin.
Q.03:- In evolutionary terms, we have more in common with
(a) a Chinese school-boy
(b) a chimpanzee
(c) a spider
(d) a bacterium
Ans:- (a) a Chinese school-boy as he is also of the same species (Homo sapiens) as we are.
Q.04:- A study found that children with light-colored eyes are likely to have parents with light-colored eyes. On this basis, can we say anything about whether the light eye color trait is dominant or recessive? Why or why not?
Ans:- As the trait is expressed in all the children of such parents, the parents are homozygous for light eye color. However, it cannot be concluded whether the light eye color is dominant or recessive.
Q.05:- How are the areas of study-evolution and classification-interlinked?
Ans:- Classification of organisms is based on relative similarities and differences among organisms. Resemblances in organisms are because they have arisen from a common ancestor and differences in them are due to adaptations to different types of environment. As the organisms can be graded in order of increasing complexity it indicates at the concept of evolution.
Q.06:- Explain the terms analogous and homologous organs with examples.
Ans:- Homologous organs :- These are organs which perform different functions but have similar structures. For example, a wing of a bat, flipper of a seal, front leg of a horse and arm of a man perform different functions but have the same structural plan.
Analogous organs :- These are organs which have similar appearance and functions but have different structures. For example, wings of a butterfly, of a bat and of a bird perform similar function of flying but are very different structurally.
Q.07:- Outline a project which aims to find the dominant coat color in dogs.
Ans:- A black homozygous male is mated with a white homozygous female. If the progeny has all black dogs then the dominant coat color is black.
Q.08:- Explain the importance of fossils in deciding evolutionary relationships.
Ans:- Fossils are impressions or imprints left by some previous organism in the soft mud which subsequently hardened or the moulds and casts of entire organisms which became preserved. Fossils tell about the organisms that lived ago. They tell about the structure of such organisms and the time period during which they lived. The fossils found in upper strata of rocks are considered to be newer than those found in the lower strata. It is also seen from the fossils that the organisms become more complex in the upper strata when compared to the lower strata which indicates towards the evolutionary process. Also transitional fossils like Archeopteryx are known which were intermediaries between reptiles and birds.
Q.09:- What evidence do we have for the origin of life from inanimate matter?
Ans:- Miler and Urey conducted an experiment in 1953 in which they assembled the inorganic gases, known to be prevalent in early earth and maintained the temperature at 100 degree Celsius and passed sparks over the mixture of gases. At the end of a week, 15% of the carbon (from methane) was converted to simple compounds of carbon including amino acids which are the building blocks of proteins. This shows that complex organic molecules can be arise from simple inorganic molecules under certain conditions which prevailed during the early period in earth's life. These complex molecules are building blocks of cells they can give rise to a living organism capable of self duplication.
Q.10:- Explain how sexual reproduction gives rise to more viable variations than asexual reproduction. How does this affect the evolution of those organisms that reproduce sexually?
Ans:- Sexual reproduction involves segregation of chromosomes into gametes by meiosis. The process of gamete formation itself introduces many variations in the chromosomes. When the gametes fuse, the normal chromosomes have become different from the parents. At each change in generation there is a notable variation in the genetic material, which over time makes the progeny very different from the ancestors. In case of asexual reproduction only the very small changes due to DNA duplication are seen in the progeny which is more or less genetically similar to the parent. Thus, it can be concluded that evolution in sexually reproducing organisms proceeds at a faster pace than in asexually reproducing organisms.
Q.11:- How is the equal genetic contribution of male and female parents ensured in the progeny?
Ans:- Genetic material in most organisms is present in pairs of chromosomes. Gametes in sexually reproducing organisms are formed by the process of meiosis (a type of cell division occurring mainly in reproductive cells for the formation of gametes) during which half of the genetic material goes into each gamete. When the gametes form male and female parents fuse with each other during sexual reproduction, the normal complement is restored. Half of the genetic material comes from the female and half from the male. Thus, process of meiosis is necessary to ensure equal genetic contribution of male and female parents through gametes.
Q.12:- "Only variations that confer an advantage to an individual organism will survive in a population". Do you agree with this statement? Why or why not?
Ans:- Variations which confer an advantage to an individual organism may or may not survive in the population depending upon the social behaviour of the organism. A variation in a social animal like ant may not survive in a population while a variation in an animal like a leopard may survive.
CHAPTER 09 :- BASIC CONCEPTS CLICK HERE
CHAPTER 09 :- INTEXT QUESTIONS AND ANSWERS CLICK HERE
