How are the hereditary changes responsible for evolution?
Formation of new species due to changes in specific characters of several generations of living organisms as a response to natural selection is called as evolution.
Sometimes, minor changes occur when a nucleotide changes its position. This is called mutation and it can bring about evolution.
Organisms which show modifications essential for survival, survive. These beneficial genes are transmitted to the next generation to a greater extent.
The sustaining and selected organisms reproduce and thereby give rise to new species with their own specific characters.
Nature selects organisms and characters which are fit to live and the rest perish.
Thus hereditary changes are responsible for evolution.
Explain the process of formation of complex proteins.
Information about protein synthesis is stored in the DNA.
These proteins are synthesized by DNA through the RNA.
mRNA is produced as per the sequence of nucleotides on DNA. Only one of the two strands of DNA is used in this process.
The sequence of nucleotides in mRNA being produced is always complementary to the DNA strand used for synthesis. Besides, there is uracil in RNA instead of thymine of DNA. This process of RNA synthesis is called as ‘transcription’.
The mRNA formed in nucleus comes in cytoplasm. It brings in the coded message from DNA.
The message contains the codes for amino acids. 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. As per the message on mRNA, amino acids are supplied by the tRNA.
For this purpose, tRNA has ‘anticodon’ having complementary sequence to the codon on mRNA. This is called as ‘translation’.
The amino acids brought in by tRNA are bonded together by peptide bonds with the help of rRNA.
During this process, the ribosome keeps on moving from one end of mRNA to other end by the distance of one triplet codon. This is called as ‘translocation’.
Many such chains come together to form complex proteins
Explain the theory of evolution and mention the proof supporting it.
According to the theory of evolution, first living material (protoplasm) has been formed in ocean.
In due course of time, unicellular organism was formed.
Gradually, changes occurred in the unicellular organisms from which larger and more complex organisms were formed.
All those changes were slow and gradual. Duration of all these changes is almost 300 crore years.
Changes and development in living organisms had been all round and multi-dimensional and this led to evolution of different types of organisms.
Hence, this overall process is called as evolution which is organizational. Progressive development of plants and animals from the ancestors having different structural and functional organization is called evolution.
The various proofs supporting the theory of evolution are: i) Morphological Evidences ii) Anatomical Evidences iii) Vestigial Organs iv) Paleontological Evidences v) Connecting Links vi) Embryological Evidences
Explain with suitable examples importance of anatomical evidences in evolution.
Sometimes organs of different organisms may not seem morphologically similar but their anatomy and structure shows great similarity.
For example, there doesn't seem any superficial similarity between human hand, ox’s foreleg, flipper of a whale and the patagium of a bat. Their use is also different in the respective organism.
However, there is a similarity in the structure of bones and joints of these organs.
This similarity in the anatomy indicates that these animals may have had a common ancestor.
Thus anatomical evidences are an important proof in the theory of evolution.
Define fossil. Explain importance of fossils as proof of evolution.
Large number of organisms get buried due to disasters like floods, earthquake, volcanic eruptions etc. Remnants and impressions of such organism remain preserved underground.
Carbon dating is used in palaeontology and anthropology for determining the age of human fossils.
Once the age of the fossils has been determined by such technique, it becomes easy to deduce the information about the other erstwhile organisms.
The depth at which the fossils are found tells us about the order in which they appeared on the earth.
For example, it seems that vertebrates have slowly originated from invertebrates.
Fossils thus provide a proof to the theory of evolution.
Write evolutionary history of modern man.
Approximately seven crore years ago, monkey-like animals evolved from some ancestors who were more or less similar to the modern lemurs.
Tail of these monkey-like animals of Africa is said to have disappeared about 4 crore years ago. (Egyptopithecus)
About 2 crore years ago some of these apes started to live on land as the forests started to decline due to dry environment. (Dryopithecus)
Their lumbar bones developed in such a way that they started to stand in erect posture.
Thus ‘Ramapithecus’ apes evolved one crore years ago.
Afterwards, this ape grew up in size and became more intelligent and thus the ape of South Africa evolved about 40 lakh years ago. (Austrelopithecus)
The morphology of these human-like animals started to appear like the member of the genus Homo, about 20 lakh years ago and skilled human developed.
About 15 lakh years ago, human walking with erect posture was evolved. (Neanderthal)
Evolution of upright man continued in the direction of developing its brain for the period of about 1 lakh years and meanwhile it discovered the fire.
The Cro-Magnon man evolved about 50 thousand years ago and afterwards, this evolution had been faster than the earlier.
About 10 thousand years ago, wise-man started to practice the agriculture and animal husbandry.
Art of writing was invented about 5000 years ago.
Modern sciences emerged about 400 years ago.
Industrial society was established about 200 years ago.