Class 10 - Biology - Heredity and Evolution

Question 1.

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

  • TTWW
  • TTww
  • TtWW
  • TtWw

Answer.

Genetic makeup of bore violet flowers with almost half of short plants will be (c) TtWW.

T – indicate tall plants

t – indicate short plants

W – violet flowers

w – white flowers

 

 

Question 2.

An example of homologous organs is

  • our arm and a dog’s fore-leg.
  • our teeth and an elephant’s tusks.
  • potato and runners of grass.
  • all of the above

Answer.

All the above examples have same structural design but different in appearance and functions. Hence, the answer will be (d) all of the above.

 

 

 

Question 3.

In evolutionary terms, we have more in common with

  • a Chinese school-boy.
  • a chimpanzee
  • a spider
  • a bacterium

Answer.

We share common characteristics with Chinese school boy, as we both belong  to same group Homo sapiens. Hence, the answer is (a) a Chinese school boy.

 

 

Question 4.

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?

Answer.

Data is insufficient to predict the recessive and dominant traits. We require more information for this.

Sometimes, recessive traits show over the dominant once.

 

 

Question 5.

How are the areas of study – evolution and classification – interlinked?

Answer.

Classification is grouping of organisms based on similarities between them. Organisms are classified using the evolutionary history.

Classification is most important to explain evolution.

On the basis of similarities and differences, we can predict the evolution for which we need to classify the organisms.

More the similarities between two species, more closely they are related. Evolution and classification are closely linked to each other.

 

 

Question 6.

Explain the terms analogous and homologous organs with examples.

Answer.

Homologous organs are those which have same basic structural organization and origin but have different functions. For example: forelimbs of humans and wings of birds.

Analogous organs are those which have different basic structure and origin but have similar functions. For example: Wings of birds and insects.

 

 

Question 7.

Outline a project which aims to find the dominant coat color in dogs.

Answer.

Let us take two coat colors of dogs, white and brown. White colored dog is mated with brown colored bitch (female dog).

If F1 generation has 3 out of 4 white coat colored progeny, it means white color is dominant.

If F1 generation has 3 out of 4 brown coat colored progeny, it means brown color is dominant.

 

 

Question 8.

Explain the importance of fossils in deciding evolutionary relationships.

Answer.

Fossils help us to study the organisms which are no longer alive.

They provide us evidences and missing link between different organisms.

For example: archaeopteryx which is no longer living, provide evidences showing a connecting link between reptiles and birds.

The study shows that it has characteristics of both birds and reptiles and birds evolved from reptiles.

Fossils help in measuring the geological times. Hence, fossils are very important in deciding evolutionary relationships.

 

 

 

Question 9.

What evidence do we have for the origin of life from inanimate matter?

Answer.

The evidence for origin of life from inanimate matter was provided by an experiment conducted by Urey and Miller in 1953.

They replicated the conditions of primitive atmosphere in a chamber.

The chamber contained molecules like ammonia, methane, water and hydrogen sulfide but lack oxygen since there was no oxygen on primitive earth.

The temperature was maintained at about 100 degree C and electrical sparks were passed through the mixture which imitated the lightning during that time.

Simple amino acids were formed which are basic building blocks of proteins.

 

 

Question 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?

Answer.

Asexual reproduction involves vegetative propagation, budding, fragmentation, etc.

They involve the production of organism from one parent only.

In sexual reproduction, a progeny have genetic contribution of two parents (50 per cent from each parent).

Hence, more variations are possible in sexual reproduction. There is random segregation of chromosomes at the time of gamete formation.

There is recombination of chromosomes.

 

 

Question 11.

How is the equal genetic contribution of male and female parents ensured in the progeny?

Answer.

Human male contains XY chromosomes and human female contains XX chromosomes.

When egg is fertilized by sperm, zygote receives either X or Y from father and one X from mother.

Hence, a progeny shares 50 per cent characters of both the parents. So, progeny has equal genetic contribution of male and female parent.

 

 

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Question 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?

Answer.

The statement in the question is not true in every situation.

All variations have variable chances of surviving in population.

Sometimes variations which lead to better adaptations of an organism have better chances of surviving in environment.

Example, heat resistance in bacteria give them better chance to survive so the variation survived.

Some variations are not even functional still they exist, for example: free or fixed earlobes.

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