Robert Hooke invented the first optical microscope
In 1665, he discovered many "small chambers" called "celluae" by looking at slices of cork through a self-made microscope. What he saw wasn't living cells but cells of the dead plant xylem.
In 1667, a living ciliate was observed by the Dutch scientist Leeuwenhoek for the first time by his self-made microscope, which was the first time human observed a living cell. Because cell biology was still a very new area and he kept absolute secrecy concerning microscopic techniques, nobody succeeded in his work after his death until more than 100 years later.
Carl Linnaeus proposed the binomial nomenclature and Linnaean classification in the 18th century. He classified almost all organisms known in his time according to their characteristics, and all of them were uniquely named. Thus, the chaos of biological classification and nomenclature was ended.
Biology in the 19th century: cell theory, Darwin's evolution theory
The optical microscope was owned by a few people until the 19th century. When it became popular, more people began to study cells. Schleiden and Schwann summarized the earlier studies and concluded that animals and plants were made up of cells in 1838-1839. In 1858, Rudolf Virchow summarized the work of his predecessors to point out that all the cells were from previous cells. The cell theory broke down the barriers between plant and animal, allowing life to be studied from a more unified view.
Theory of evolution by Charles Darwin was one of the most significant landmarks in 19th-century biology. He proposed that every organism had descended from a common ancestor. In the natural selection, competition to survive resulted in the advantageous characters and the loss of disadvantageous ones. Organisms differentiated into species in a long, slow and gradual process. Darwin's theory took the biological world by storm and had a profound effect on further research.
In 1876, Hertwig observed the fertilization of animal cells. After this, plant fertilization and the phenomenon that germ cells have only a half number of chromosomes were discovered. The genetic law that discovered by G. Mendel 34 years ago received attention again in 1900. People started to recognize that chromosomes and genetic traits were somehow related. In 1910, Morgan discovered that the genes determining genetic traits were located on chromosomes after years of experiments on fruit flies. The classical gene theory described biology from a new perspective and was introductory to molecular biology.
Early 20th-Century Biology: The Prelude to Molecular Biology
High-performance new microscopes, including the polarizing microscope, interference microscope, and phase contrast microscope, were invented in the late 19th century by developments in mathematics, physics and materials. For 100 years, from the mid-19th century to the mid-20th century, cells were studied through optical microscopes and stained sections. The cell membrane, protoplasm, the nucleus, and many organelles were discovered. Amitosis, mitosis, and meiosis were also identified during this time. The investigation of cells was not limited in microscopic observation. The experimental manipulation and in vitro cultures were also included in biology. Humans can control cell activities partially according to their purpose.
With the development of electron microscopes since the 1950s, a whole new microscopic world of ultrastructure had been unveiled. Mitochondria, Golgi apparatus, cell membrane, nuclear membrane, nucleolus, chromatin and chromosomes were shown in much greater detail than before, but also the new organelles were discovered, such as endoplasmic reticulum, ribosomes, lysosomes and the cytoskeleton system.
Biology entered the molecular era, developed rapidly from 1950s
It was from 1950 that molecular biology started growing very fast. The double helix model of DNA was postulated by Watson and Crick from the X-ray diffraction photographs in 1953. Subsequently, the famous Meselson-Stahl experiment demonstrated DNA's semi-conservative replication. This experiment verified that each daughter DNA molecule contains one original strand and one newly synthesized strand after DNA replication. Genetic information was transmitted more accurately in this mechanism. In the early 1960s, the code for protein synthesis was deciphered. The information in gene is transcribed into mRNA. Then, this mRNA will leave nucleus and travel to a ribosome in the cytoplasm, where it tells the ribosome to construct a particular order of amino acids for protein synthesis. This process is called central dogma whose discovery heralded the birth of molecular biology.
By the end of the 1960s, the genetic code had been completely unraveled. Three nucleotides in mRNA code for one amino acid. The tRNAs carrying amino acids bind to mRNA. These amino acids are joined into polypeptides with the help of ribosomes.
PCR (Polymerase Chain Reaction)
The technique was devised in 1983 by American biochemist Kary Mullis. Double-strand DNA dissociates into single strands in hot water. When the water temperature drops, the DNA and nucleotides will re-synthesize into double-stranded DNA by the enzyme. Even a trace amount of DNA molecule samples can be amplified into millions of copies in a short time—through heating and cooling in repeated cycles. This technology applies to a small amount of hair and tissue left at a murder scene, human remains thousands of years old, or even ancient organisms in fossils. As long as a trace of genetic material is found, PCR can amplified it into a large quantity.
Gene Editing
Genome editing (gene editing) allows scientists to delete or add genetic material in the genomes according to their will. Modified genetic material makes organisms exhibit characteristics they never had before. People can precisely alter organisms just like gods. For example, lettuce edited by gene technology contains a lot of Vitamin C equal to kiwi fruit. This technology is having a significant impact on medicine and agriculture. According to the traditional breeding, it will last for years or even decades to improve a species. Even space breeding that is done with the help of cosmic radiation is ineffective, because the naturally created mutations are not easily controlled or random.
In addtion, molecular biology has seen many breakthroughs in biochips, cloning technology, microbial fermentation engineering and the Human Genome Project.