Evolution || Class 9 Science Notes

Evolution

1. Short answer type questions: 

a. Define organic evolution.

→ Organic evolution is the process of gradual and older changes in organisms from one form to another.

b. What are fossils?

= Traces and preserved remnant of dead animals and plants are called fossils.

c. Define embryo.

 → An embryo is defined as a multi-cellular structure, that is developed from the zygote which give rise to offspring generally present inside the female tissue or egg -membrane.

d. Define palaeontological evidence. 

= Palaeontological evidence is considered as the strongest evidence of evolution.   

e. Define homologous organs. 

→Homologous organs are those organs which have a similar embryonic origin and basic structure but different functions.

f. What are analogous organs? 

= Analogous organs are those organs of different organisms that have the same function but different anatomy.

g. What are mutagens? 

→ The effects of radiation and chemicals chrome comes that factors are called mutagens.

h. Give any five examples of vestigical organs in human.

→ Canine teeth, hairs on the body, etc.

i. What is the sudden chromosomal change in organisms called? 

= The sudden chromosomal change in organisms is called mutation.

j. Who suggested natural selection as the main cause of evolution? 

= Charles Darwin suggested natural selection as the main causes of evolution.

k. Who suggested use use and disuse of causes of evolution? 

= Jean Baptiste de Lamrack suggested and disuse of organs as the main causes of evolution. 

l. Who suggested mutation theory? 

= Hugo de Vries suggested mutation theory.

m. Mention any two types of mutation.

→ The two types of mutation are:

i. Neutral mutation

i. Beneficial mutation

n. Define continuous variation. 

→ Continuous variation the possibility of intermediate character as well.

o. Define discontinuous variation. 

→Discontinuous variation is that in which there is no possibility of intermediate character.

2. Long answer type questions:

a. Mention any four evidences of organic evolution. 

= i. Evidence from fossils or palaeontological evidence.

ii. Evidence from embryos or embryological evidence.

iii. Evidence from geographical distribution of organisms

iv. Evidence from connecting animals.

b. How do homologous and analogous organs give evidence of evolution?

= Homologous and analogous organs have same basic structure, there ancestors might be same so, they give evidence of evolution.

c. What are vestigial organs? How are they different from homologous organs? 

→ Those organs which are functionless and present as reduced structures in the body. called vestigial organs. They are different from homologous organs because they are functionless and present as reduced structures in the body whereas homologous organs have different functions.

d. Write in short about Lamarckism natural selection and Variation.

→ Jean Baptiste de Lamarck is a French philosopher and biologist, who brought forward the scientific explanation of the mechanism of evolution for the first time.

* Natural selection ⇒ Natural selection is defined. process of selection of living organisms by the of suitable presence variation in organisms. Because such variation help the organisms to compete, survive and reproduce.

* Variation =Variation is morphological or physiological change in organisms due to either genetic or environmental reason. It also may be continuous on discontinue. It may he somatogenic or blastogenetic.

e. What are the drawbacks of Lamarckism and Darwinism?

→ → The drawbacks of Lamarckism are:

i. Lamarck has not proved experimentally that use and disuse of organs can modify organisms.                                                            ii. It is absolutely incorrect that new organs can be developed according to the need and wish of an organism.

iii. All the acquired characters are not inherited into new generation.                           

=  The drawbacks of darwinism are:

i. Darwinism doesn't explain the origin of variation.

ii. It is not always the case that useful variation's are selected.

iii. Natural selection is not the sale cause of speciation bud it is only a guiding factor new species also arise due to the mutation.

iv. Darwinism doesn't explain the presence of organs found in organisms.

f. What is natural selection? How does it lead to evolution.

→ The process of selection of living organism by the presence of suitable variations in organisms is called natural selection Natural selection lead t the evolution through advantages variation. The variation acquired by an organism are transmitted to the next generation and won. After a long time, these variations give to entire new species which is quite different that of its ancestors.  

g. Mention the major paint of Darwinism. 

→ The major point of Darwinism are:

i. Enormous fertility = Every species tends to multiply in geometric ratio. It means that a population doubling its number in one year increases four times in the second year and night time: in the third year.

ii. Struggle for existence → All the offspring do not survive and reproduce for. their average life span. They have to complete among themselves for food and shelter and it is called struggle for existence.

iii. Variation and heredity → Even though the offspring are very similar to their parents they are not identical. They differ from each. other to some or more extent in size, shape, colour, behaviour,etc which is called variation.

iv. Natural Selection = Instead of term natural selection used by Darwin, Herbert Spencer used survival of the fittest. The process of selection of living organisms by the presence of suitable variations in organisms is called natural selection .   

v. Origin of new species of variation: → Due to these changed useful characters, individuals Survive and may acquire more useful characters to survive in the struggle. After many generation, these individuals become quite different from their ancestors and they solve evolve into new species.

h. Describe continuous and discontinuous variation with two examples of each.

= Continuous variation is that in which there is the possibility of intermediate character as well. There is the possibility of different heights between. very tall and very short person. For example: skin colors,  intelligence.

→ Discontinuous variation is that in which there is no possibility of intermediate character. For example we have particular the of blood, special finger print,etc.

i. Write in short about connecting links and embryonic evidence?

= Some animals stand between the and have the characters of bath. groups groups They are called connecting links or bridge animals. Protopterus a lung-fish which possesses fish-like characters.ie. scales, fins, etc as well as amphibians like character i.e. lungs.

* Embryonic Evidence →An embryo is defined as a multi-cellular structure that is developed from the zygote which rise to new offspring generally present inside the female tissue of egg-membrane. A branch of biology that deals with the study of formation and development of the embryos is called embryology.

b. Write the summary of mutation theory. 

→ i. The summary & mutation theory are: Mutations are large, sudden and discontinuous variation in a population.

ii. These changes are inheritable in transfer from generative to generation.

iii. Mutations provide the raw material or basic for organic evolution.

iv. Harmful or negative mutations may persist or get eliminated by nature.

4. Give reason:

a. Lamarckism was rejected after Darwinism. 

→ Because no mechanism was proposed to explain how lamarckism evolution would take place.

b. Six-fingered offspring may be formed from normal fingered parents.

→ Because mutation may be neutral, useful or handful. Due to effect of harmful mutation six-fingered may farm in off-springs.

c. Platypus is considered as a bridge animal between bird and mammals.

→ Because It has a beak, like in birds and mammary glands and hair on its body, like in mammals.

d. In embryonic stage humans, bird, and fish are similar in many aspects.

→ Because the embryonic or internal structure of body of humans, birds and fish are similar.

e. Haecked said that antogeny repeats phylogeny.

= Because when the embryos of different. species of animals are compared, it is seen that they resemble one another at one or the other stage of developments.

f. Our tail and muscles to move ears are in the extinct condition.

= Because we have our ancestors not use them for a long period of time in order to not use of them they are in the extinct condition.  

g. Write in short about:

= * Struggle for existence:

- All the offspring do not survive and reproduce for their average life span They have to compete among themselves for food and shelter and it is called struggle for existence.

* Enormous fertility

- Every species tends to multiply in geometric ratio. It means year that a population doubling its number in one increase four times in the second eight times in the third year.

* Beneficial mutation

→ It causes advantageous effect on mutants. In this mutation, a new type of protein is formed which helps the the mutants to adapt in the surroundings.

4. Differentiate between:

a. Homologous

i. They are those organs which have a similar embryonic basic structure but different functions. 

ii. It is closely related with the morphology and anatomy.

* Analogous

i. They are those organs of different organisms the same function but different anatomy.

ii. It is also closely related with the morphology and anatomy.

b. Lamarckism 

i. Jean Baptiste de Lamarck is the founder of Lamarckism.

ii. He proposed Lamarckism in his book philosophie Zoologique.

* Darwinism

i. Charles Darwin is the founder of Darwinism.

ii. He proposed Darwinism in his book origin of species.

c. Heredity 

i. It is explained by Darwinism.

ii. In heredity, every organisms are fit better into their natural environment than other organisms.

* Variation

i. It is also explained by Darwinism.

ii. In variation, every organisms is differ from each other in size, shape, color, etc.

d. Continuous variation

i. There is possibility of intermediate character as well.

ii. for ex: there is no distinct category of height, People, are not only tall or short.

* Homologous organs

i. There is no possibility of intermediate character.

ii. For ex: except some abnormality we are either male or female: we have a particular type blood group.

e. Homologous Organs

i. They are those organs which have a similar embryonic basic structure but different functions. 

ii. It is similarly intermediate between organisms like forelimbs of whale, horse, bat and birds, etc.

* Vestigial Organs

i. It organs are and present are functionless as reduced structure in the body.

ii. A number of vestigial organs are found in different organism like vermiform appendix, muscles of external ears, hair on body. canine teeth etc.

6. Diagrammatic questions 

a. Sketch the embryos of bird and humans and fish. Also justify that they give evidence of evolution.

= 

b. Answer the following question on the basic of the given diagram:

i. Which organism is shown in the diagram? 

= Archaeopteryx

ii. What characters of birds are found in it? 

= It has wings and feathers like in birds.

iii. What characters of reptiles are found in it? 

= Teeth, long tail and

iv. Why is it called a bridge animal?

= Because It links between reptiles and aves.

c. Answer the questions on the basic of the given diagram. 

i. What type of evidence of evolution is given by the diagram? Explain the evidence in short.

= Evidence from comparative morphology and anatomy is given by the diagram.

= Each group of animals has its own pattern of body organization and it characteristics possesses a common set of characteristics.

ii. What similarity is found in the organs given in the diagram.   

→ They are homologous organs and their internal. structure or organs is same.

iii. Name the bones found in all of them. 

= The bones found in all of them are:

i. Homerus (H)

ii. Radius (R)

iii. Ulna (U) 

iv. Carpals (c)

v. Metacarpals (MC)

vi. Phalanges (D)

iv. How do the bones support organic evolution? 

= The bones supports organic evolution are given below:

1. The structure of whale, horse, human, bat, and bird are having similar and structure as they found from the same ancestors organisms.