NIOS Class 12 Biology Worksheet 1 Solution helps students clearly understand the important concept from the first lesson on Origin and Evolution of Life and Introduction to Classification.
This solution covers the chemosynthetic theory of origin of life, the stages of evolution, evidences of organic evolution, Darwin’s theory and Neo-Darwinism, sources of variation, natural selection, speciation based on NIOS Class 12 Biology (314) study material. This worksheet solution is useful for quick revision and exam preparation.
Origin and Evolution of Life and
Introduction to Classification Worksheet Solution
Q1. This figure is related
to origin of life on earth. Answer the following questions:
a. Name the scientist who proposed this experiment.
b. What did he confirm from this experiment?
c. What is coacervates?
d. How did they confirm the chemosynthesis theory of evolution.
Explain.
Answer
(a) Stanley Miller
(b) He confirmed that simple organic molecules like amino acids can be formed from simple gases (NH3, CH4 ,H2, H2O ) under conditions similar to the primitive earth using electric sparks or lightning.
(c) Coacervates are microscopic droplet like aggregates of large organic molecules surrounded by a thin boundary. They are believed to be the precursors of the first living cells.
(d) Miller and Urey filled an apparatus with gases believed to be present in the early atmosphere (ammonia, methane, hydrogen and water vapour). They passed electric sparks through it to imitate lightning and heated water to imitate the primitive oceans. After one week, the liquid collected in the tarp contained amino acids and other organic compounds.
This proved that organic molecules of life can be formed from inorganic substances under primitive earth conditions, this confirms Oparin’s chemosynthetic theory.
Q2. Charles Darwin had
given a statement,” in organic evolution, the nature selects for greater
reproduction only the organisms suited to live in their environment.” Give
reasons in support of your answer.
Answer
According to Charles Darwin’s theory of natural selection, organism produce more offspring than can survive. Because environment resources are limited and there is struggle for existence. The nature selects for greater reproduction only the organisms who have following characteristics:
i. Individual show variations.
ii. Those organisms which possess favourable variations.
These organisms survive longer and reproduce more and organisms with unfavourable variations are eliminated.
Over many generations, these favourable traits accumulate and the species gradually changes. So, the nature selects only those organisms for greater reproduction which are best suited to live in their environment. This proves Darwin’s statement.
Q3. “Evolution is slow and
gradual process. “Do you agree or not. Explain your views about its favour and
against both.
Answer
Yes, I partly agree with this statement. Mostly
evolution is slow and gradual but sometimes it is rapid.
Evolution is slow and gradual
According to Charles Darwin and the method of Phyletic
Gradualism, evolution occurs through small changes over very long geological
time.
Following evidences support that evolution is gradual and continuous.
i. Fossils records
ii. Morphological and embryological similarities show that organisms changed very slowly from simple to complex forms over millions of years.
Evolution can be rapid
According to Punctuated equilibrium proposed by Niles Eldredge and Stephen Jay Gould:
i. New species may appear suddenly due to major genetic changes.
ii. After that they remain unchanged for long periods.
Examples: - DDT resistant mosquitoes, industrial
melanisms in peppered moth
Conclusion
Evolution is mostly slow and gradual but, in some
cases, it can appear rapid due to sudden genetic changes.
Q4. “Industrial melanism
is good example of natural selection in action.” Justify this statement.
Answer
Industrial melanism is explained with the example of
the peppered moth Bitson betularia.
Before factories and pollution, the trunks of trees
were covered with light coloured lichens. At that time, most moths were also
light coloured. Because of this,they could easily hide on the tress and birds could
not see them. Sometimes a black moth was also seen but birds quickly notice and
ate it.
Afte the industrial revolution, smoke from factories covered
the trees with black soot and the lichens disappeared, now the light-coloured
moths became clearly visible to birds and were eaten.
The black moths could hide easily on the dark tree
trunks so they lived longer and produce more young ones and on the other hand
light coloured moths disappear. So industrial melanism is considered a very good
examples of natural selection.
Q5. Two squirrel’s species
live on opposite side of the Grand Canyon show similar adaptive process.
Describe the phenomenon and justify how they give evidence for evolution.
Answer
Two squirrel species are found on opposite sides of the
Grand Canyon. Long ago, they were part of the same population. When the canyon
was formed, a deep geographical barrier separated them.
Because of this separation, the two groups could non
meet or interbreed. Each group lived in a different environment and faced
different conditions. Over a very long time, small variations occurred in both
groups. Natural selection acted differently on them according to their
surroundings.
As a result, both groups developed similar types of
adaptations suited to their own environment, but they gradually became
different species.
This phenomenon is called allopatric speciation.
This example give evidence for evolution because:
i. It explains how variations and natural selection can lead to formation of new species over time.
ii. It proves that new species arise from a common ancestor through gradual changes.
Q6. Identify the figure and answer the following:
(a). Name the organisms
(b) Give its class
(c) It has connected with evolution
evidences. Give reason in support of your answer.
Answer
(a) Archaeopteryx
(b) Aves
(c) Archaeopteryx is called connecting link between reptiles and birds. It had feathers and wings like birds. It also had teeth in the beak, long bony tail and claws like reptiles. Because it shows feature of both reptiles and birds, it proves that birds have developed from reptiles. Thus, Archaeopteryx provides strong evidence in support of evolution.
Q7. A cat is called billi
in Hindi,biral in Bengal and Chat in French. Give reasons to support to your
answer, why are scientific names considered better than common name.
Answer
A cat is called billi in Hindi,biral in Bengal and
Chat in French. This shows that common names change from place to place and
language to language which can create confusion.
Scientific names are considered better because:
i. A scientific name is same all over the world.
ii. It helps scientists and students identify the exact organism without confusion.
iii. Scientific naming follows a fixed universal system called binomial nomenclature given by Carolus Linnaeus.
iv. Each organism has one unique scientific name made of genus and species.
v. Scientific names are mostly in Latin or Greek so they are universally accepted.
Therefore, scientific names make communication about
organism clear, accurate and uniform everywhere.
Q8. Differentiate between following pairs:
(a) Homologous and analogous organisms
(b) Natural selection and mutation
(c) Isolation and speciation
Answer
(a) Difference between Homologous and Analogous organs
|
Homologous
organs |
Analogous
organs |
|
Similar in structure
and origin |
Different in structure
and origin |
|
May perform
different functions |
Perform same function |
|
Show common
ancestry |
Do not show
common ancestry |
|
Example: Forelimbs
of vertebrates |
Examples: Wings
of insect and bird |
(b) Difference
between Natural selection and Mutation
|
Natural
selection |
Mutation |
|
Process in which
favourable variations are selected by nature |
Sudden genetic
changes in gene or chromosomes |
|
Act on existing
variations |
Produce new
variations |
|
Leads to differential
reproduction |
Creates new
traits in organisms |
|
Example:
Industrial melanism |
Example:
DDT-resistant mosquitoes |
(c) Difference
between Isolation and Speciation
|
Isolation |
Speciation |
|
Separation of
population by geographical or reproductive barriers |
Formation of new
species |
|
Prevents interbreeding
between groups |
Result of long
terms isolation, variation and natural selection |
|
Keep species
genetically distinct |
Produces different
species from common ancestor |
|
Example:
Geographical separation |
Example: Allopatric
and sympatric speciation |
Q9. What is the role of
vestigial organs in our ancestors and in our life? Give reasons in support of
your answer with examples.
Answer
Vestigial organs are small, poorly developed and nonfunctional
parts of the body which were functional in our ancestors.
Role in ancestors
In our
ancestors, these organs were useful and performed important functions. Over time,
due to changes in habits and environment, these organs lost their use.
Role in our present life
In humans, these organs do not perform any important
function. They remain in the body as evidence of our evolutionary past.
Examples:
i. Appendix: - useful in ancestors for digestion of plant food but now it is nonfunctional.
ii. Wisdom teeth: - helped ancestors in chewing hard food but now they are useless.
iii. Tail vertebrae: - ancestors had a tail, now only small bone remains.
iv. Body hair: - ancestors had thick hair for protection but now they reduced.
Vestigial organs prove that humans have evolved from
ancestors in whom these organs were functional. They provide strong evidence in
support of evolution.
Q10. ‘Biologist use
structural features to classify organisms.’ Give reasons to justify your
arguments.
Answer
Biologists group organism by observing their structural (Morphological) features because:
i. Structural features are clearly visible and easy to compare.
ii. Organisms that have similar body structure usually share a common ancestry.
iii. Differences in structure help to place organism into different groups.
iv. Early classification was based mainly on morphology which helped in identifying similarities and differences.
So, studying structural features helps biologists to
arrange organisms into groups and understand their evolutionary relationships.
This worksheet solution helps students understand how life began on earth, how organisms evolved over time and why classification is necessary for studying the vast diversity of living beings. This worksheet strengthens both conceptual clarity and exam preparation.
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