MCQ
The first cellular form of life could have originated
- ✓$2000$ million years back
- B$11000$ million years back
- C$1500$ million years back
- D$500$ million years back
✓
Answer
Correct option: A.
$2000$ million years back
a
$2000$ million years.
$2000$ million years.
Experimental Evidences of Chemical Evolution
Experi ik mentally chemical theory of evolution performed by SL Miller and HC Uray in $1953 .$
He created electric discharge in a closed flask containing $CH _{4}, H _{2}, N H _{3}$ and water vapour at $800\, C .$ He observed formation of amino acids. In similar experiments other the observed, formation of sugar, nitrogen bases, pigments and fats
The first non-cellular forms of life could have originated-$3$ billion years back. The first cellular form of life did not possibly originated till about $2$ billion years ago because the conditions were non-biogenic at that time. This version of biogenesis, $i.e.,$ the first form of life arose slowly through evolutionary forces from non-living molecule was accepted by majority
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A. Tetrad formation is seen during leptotene
B. During Anaphase, the centromere split and chromatids separate.
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(ii) Axial skeleton comprises 80 bones distributed along the main axis of the body.
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(i) In human beings, this system is made up of 206 bones and a few cartilages.
(ii) Axial skeleton comprises 80 bones distributed along the main axis of the body.
(iii) The skull, vertebral column, sternum and ribs constitute axial skeleton.
(iv) Cranial bones are 8 in number. The facial region is made up of 14 skeletal elements which form the front part of the skull.
(v) First vertebra is the atlas and it articulates with the occipital condyles and human skull is bicephalic.
(vi) The number of cervical vertebrae are seven in almost all mammals including human beings.
(vii) Ribs has two articulation surfaces on its dorsal end and is hence called dicondylic.
(viii) Last 3 pairs of ribs are not connected ventrally and are therefore, called floating ribs.
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