Heredity and Evolution | Ruturaj Jadhav’s Classes
Chapter Summary: (Just for understanding)
Heredity and Evolution
Heredity Evolution
-Central Dogma -3 Theories:
-Transpiration (Theory of Evolution
-Translation Darwin’s Theory
-Translocation Lamarck’s Theory)
-6 Evidences of Evolution
-Speciation
-Human Evolution
Heredity:
Heredity is the transfer of biological characters from 1 generation to another
via genes.
The science of heredity is useful for diagnosis, treatment, production of
hybrid varieties of animals & plants, etc.
Points important for objective type questions:
Johann Mendel is the father / pioneer of modern genetics.
Dr.Har Govind Khorana discovered triplet codons for 20 amino acids.
George Beadle and Edward Tatum discovered that protein synthesis
occurs through genes.
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Central Dogma
1. The genes participate in the functioning of the body.
2. Synthesis of proteins is necessary for the body.
3. The flow of genetic information to perform protein synthesis is called as central
dogma.
4. In this process, the DNA is transcribed into RNA and RNA is translated and
translocated into proteins.
Transcription
1. An enzyme called RNA polymerase reads the DNA and converts it to RNA.
2. The newly formed RNA is single stranded and is known as messenger RNA
(mRNA).
3. This process of RNA synthesis in the nucleus is called transcription.
4. The sequence of nucleotides in mRNA is always complimentary to the DNA
strand.
5. DNA has thymine but RNA has uracil instead of it.
Translation
1. The mRNA formed due to transcription comes out of the nucleus into the
cytoplasm.
2. The mRNA contains codes for amino acids.
3. The code for each amino acid consists of three nucleotides. It is called as
'triplet codon'. Each mRNA is made up of thousands of triplet codons.
4. The tRNA (transfer RNA) converts the message of mRNA into Amino acids.
5. For this process the tRNA has an anti-codon for the codon on mRNA.
6. This process is called as ‘Translation’.
Translocation
1. When the mRNA comes out in the cytoplasm from the nucleus, the ribosomes
bind them.
2. The tRNA releases amino acids which are bonded by peptide bonds with the help
of rRNA.
3. During this process, the ribosome keeps on moving from one end of mRNA to the
other end by the distance of one triplet codon.
4. This process is called as 'Translocation'.
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Heredity and Evolution | Ruturaj Jadhav’s Classes
Theory of Evolution
1. The first living material (protoplasm) has been formed in ocean.
2. In due course of time, unicellular organism was formed.
3. Changes occurred in the unicellular organisms from which larger and complex
organisms were formed.
4. These changes were gradual and took about 300 million years.
5. This continuous process of multi-dimensional changes, is known as evolution. It
has led to different types of organisms.
Darwin’s Theory
This theory was published in the book ‘Origin of Species’ by Charles Darwin. This
theory is also called as ‘Theory of Natural Selection’ or ‘Concept of survival of the
fittest’.
1. All organisms reproduce prolifically.
2. The off-springs compete with each other in a life-threatening manner.
3. In this competition, only those organisms sustain which show modifications for
winning the competition.
4. Natural selection also plays important role because nature selects only those
organisms which are fit to live and the rest perish.
5. Sustaining organisms can perform reproduction and give rise to the new species.
Objections raised against Darwin’s theory:
1. Natural selection is not the only factor responsible for evolution.
2. Darwin did not mention anything about useful and useless modifications.
3. No explanation about slow and abrupt changes.
Jean-Baptiste Lamarck's Evolutionary Theory:
1. Lamarck proposed that morphological changes drive evolution.
2. These changes were caused by an organism's activities or laziness.
3. He named this idea the principle of 'use or disuse of organs.'
4. According to Lamarck, organs develop or degenerate based on their usage.
5. Lamarck further proposed that the acquired characters transfer from 1
generation to another and named it as ‘Theory of inheritance of acquired
characters’.
6. The theory of use or disuse of organs was widely accepted but the inheritance
theory was rejected. Because, genetic characters are transferred and not acquired
characters.
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6 Evidences of Evolution:
1. Morphological Evidences
2. Anatomical Evidences
3. Vestigial Organs
4. Paleontological Evidences
5. Connecting links
6. Embryological Evidences
Evidence What is How it is proved?
proved?
Morphological Evidences Plants: Similarity in characters like
leaf shape and leaf venation
Animals: Similarity in structure of
mouth, eyes and body hair
Anatomical Evidences Similarity in structure of bones and
joints
Vestigial Organs An organ which is vestigial for 1
organism may be useful to other
These organisms.
organisms had Example: Appendix in humans in
common useful for ruminants and muscles of
ancestors ear pinna are useful for monkeys
Connecting links Some plants and animals show
morphological similarities with 2
different groups, hence they are
called as connecting links.
Ex:
1. Peripatus is connecting link
between Annelida and
Anthropoda.
2. Duck Billed Platypus is
connecting link between
mammals and reptiles.
Embryological Evidences Similarity during initial stages in
embryo
Important points from connecting links:
1. Mammals have evolved from reptiles
2. Amphibians have evolved from fishes
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Paleontological Evidences:
What are Fossils and why are they important for study of evolution?
1. Fossils are the remains and impressions of organisms which died long back.
2. They are preserved underground over millions of years.
3. Fossils help us discover which organisms lived long ago.
4. They explain Earth's history, showing effects of disasters like floods and
volcanoes.
5. Fossils are important in the study of evolution, helping us understand how species
have changed over time.
Carbon Dating: (developed by Willard Libby)
1. The method used to find the age of human fossils and manuscripts is called as
Carbon Dating.
2. When plants or animals die, their body starts decaying. This makes changes in
C12 and C14.
3. C12 is non-radioactive and C14 is radioactive.
4. The age of the fossil is found from:
a. change in ratio of C12 and C14
b. change in radioactivity of C14
5. This study shows that: VERTEBRATES ORIGINATED FROM INVERTIBRATES
Aves (Birds) Cenozoic era
Mammals
Reptiles Mesozoic era
Reptiles
Amphibia Paleozoic era
Pisces
Vestigial Organs:
1. Degenerated or underdeveloped useless organs are called as vestigial organs.
2. Organisms can’t develop new organs suddenly.
3. Therefore, existing organs gradually change.
4. However, if these organs become useless or harmful, they are degenerated.
5. This is because of Principal of Natural Selection and takes 1000s of years.
6. Such useless organs may be useful for other organisms. For example:
Tail bone (coccyx), wisdom teeth and body hairs of humans.
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Human Evolution:
Lemur 7 crore years ago Monkey-like animals evolved from
ancestors similar to the modern
lemurs
Egyptopithecus 4 crore years ago Tails of these animals disappeared in
Africa
Dryopithecus 2.5 crore years 1. Developed due to - Enlarged brain
and improved hands
2. Erect posture due to – lumbar
bone development
Ramapithecus 1 crore years ago Evolved into ape like animals who
used hands for eating food. FIRST
RECORD OF HUMAN LIKE ANIMAL
Austrelopithecus 40 lakh years ago Ape grew in size and became more
intelligent
Skilled Human 20 lakh years ago Appeared like member of genus
Homo
Man with erect 15 lakh years ago Walking with erect posture
posture
Neanderthal 1.5 lakh years ago Brain developed and discovered fire
Cro-Magnon Man 50 thousand Evolved fast to become modern man
years
Farming, raising animals, building 10,000 years ago
cities, and creating culture
Started writing 5,000 years ago
Modern Science Began 400 years ago
Industrial society formed 200 years ago
Specification
1. Evolution Leads to New Species. Different types of plants and animals appear as
evolution happens.
2. A species is a group of organisms that can reproduce naturally and have fertile
offspring.
3. Differences in genes, environment, and how they reproduce can create new
species. Isolation also contributes.
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