Microorganisms (1670s)

With the use of his own handcrafted microscopes, Dutch lens grinder and scientist Anton Van Leeuwenhoek (1632 - 1723) became the first to discover and describe a whole new world of living organisms, which he referred to as animalcules, now termed as microorganisms. He also studied bacteria, muscular fibers, sperm and red blood cells. His observations provided the basis for the establishment of the new science of microbiology.

Photosynthesis (1770s)

Dutch chemist and physiologist Jan Ingenhousz (1730 - 1799) noticed how plants responded differently in the presence of sunlight than when it was placed in the shade, a step that became essential in the discovery and greater understanding of the process of photosynthesis. Photosynthesis is a metabolic process by which plants, algae and some bacteria convert light energy into chemical energy. In addition to light, carbon dioxide and water are absorbed by its leaves and roots respectively. Sunlight created a reaction that produces carbohydrates (food for the plants such as glucose and sucrose) and oxygen (the end-product released into the environment). Almost all life on Earth are either directly or indirectly dependent on this process for their source of energy.

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The Cell Nucleus (1830s)

Scottish botanist Robert Brown (1773 - 1858) was examining orchids under a microscope when he noticed an opaque structure inside the cells, which he labeled as the “nucleus.”

Cell Division - Mitosis (1870s)

German physician Walther Flemming (1843 - 1905) carefully investigated the process of animal cell division by stages and the resulting chromosome distribution; and named the process mitosis. On the other hand, Polish-German botanist Eduard Strasburger (1844 - 1912) independently observed a similar process in plants.

Cell Division - Meiosis (1880s)

German biologist August Weismann (1834 - 1934) observed that sex cells or gametes (spermatozoa and ova) divide differently from other cells of the body. The divided cell end up with only half of a chromosomal set in a process called meiosis. His experimentation with the sexual reproduction of sea urchins led him to conclude that variations in offspring are the result of the union of essence from both parents, referring to this essence as “germ plasm.” The magnitude of the work of Weismann, Flemming and Strasburger was finally realized with the rediscovery of Gregor Mendel’s (1822-1884) work on heredity in the early 20^th century. Their discovery of mitosis, meiosis and chromosomes is regarded as one of the greatest scientific discoveries of all times.

Cellular Differentiation (1880s onwards)

A number of scientists contributed to the discovery of cellular differentiation that ultimately led to the isolation of embryonic stem cells in humans. Cellular differentiation is the process in which less specialized cells as these embryonic stem cells developed into highly specialized cells or tissues that make up the body like lungs, heart and skin. These differenciations are largely attributable to highly-controlled modifications in gene expression, that is, certain genes are deactivated while others are activated in order for a cell to turn into tissues that perform a specific function. Every undifferentiated cell has the potential to become any type of cell.

Mitochondria (1880s onwards)

Few scientists discovered mitochondria, which are sometimes referred to as “cellular power plants.” It’s because these tiny structures within animal cells are primarily responsible for metabolism and conversion of food into chemicals, specifically adenosine triphosphate (ATP), a source of energy that cells use. Other functions of mitochondria include a wide variety of processes, such as cellular differentiation and regulation of cell cycle from cell growth to cell death. Many researchers currently think that they are a specialized form of bacteria with their own genetic make-up.

Neurotransmission (1890s - 1930s)

The discovery of neurotransmitters led to a greater understanding of how they coordinate bodily functions by sending signals from one nerve cell to another by means of electrical signals or chemical substances. Examples of neurotransmitters include dopamine (associated with voluntary movement and addiction); serotonin (sleep and temperature regulation); and epinephrine (alertness and arousal). Lack of formation and action of necessary neurotransmitters can cause bodily malfunctions, such as that insufficient dopamine formation is at least in part to blame for Parkinson’s disease.

Hormones (1900s)

English physiologists William H. Bayliss (1860 - 1924) and Ernest H. Starling (1866 - 1927) introduced the concept of hormones, coining the term and revealing its role as chemical messengers. They discovered the peptide hormone secretin, a substance released into the blood stream from the duodenum (a portion of the intestine) that reduces acid secretion from the stomach and stimulates digestive pancreatic enzyme secretion into the intestine.

The Krebs Cycle (1930s)

German biochemist Hans Krebs (1900 - 1981) and Hungarian physiologist Albert Szent-Györgyi (1893 - 1986) identified a series of enzyme-induced chemical reactions which a cell undergoes to convert carbohydrates, proteins and fats into energy. Also known as citric acid cycle, it is a function of great significance in all living cells that utilize oxygen for cellular respiration, and contributes to the breakdown of carbohydrates, protein and fats into carbon dioxide and water.

Archaea (1970s)

American biologist Carl Woese (1928 - ) found that bacteria are not the only unicellular organisms in the world without a nucleus, and classified these unique organisms under a new kingdom of Archaea. Most of these organisms are observed to be extremophiles, that is, they live in harsh environment. Some survive at exceedingly high or low temperatures, while others in highly acidic, alkaline or saline waters. Some even thrive on sewage, marshland and soil. Unlike bacteria, archaea are not harmful and do not cause diseases. Their discovery has proven to be significant in biotechnology as they are used in the creation of environmentally-friendly processes in green chemistry to synthesize organic compounds, food processing at high temperatures, sewage treatment and more.

Ecosystem (1930s onwards)

English botanist Arthur George Tansley (1871 - 1955) championed the term “ecosystem” and became a pioneering influence in bridging the science of ecology with fields of biology, physics, chemistry and other scientific fields that describe the environment into one coherent whole. An ecosystem is defined as a natural unit comprising of all biological factors (animals, plants and microorganisms) functioning together in a set of highly inter-dependent relationships with all the non-living physical and environmental factors. Species diversity, better known as biodiversity, is often used to gauge the health of biological systems. The greater degree of biodiversity of an ecosystem is thought to contribute to the greater degree of resilience of an ecosystem. Studying the reason why a wider variety of species exist in the tropics permits modern scientists to help protect life on Earth.

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