Life ?
What is life ?
Life is the aspect of existence that processes, acts, reacts, evaluates, and evolves through growth (reproduction and metabolism). The crucial difference between life and non-life (or non-living things) is that life uses energy for physical and conscious development.
What is darwinian evolution ?
Darwinism is a theory of biological evolution developed by the English naturalist Charles Darwin (1809–1882) and others, stating that all species of organisms arise and develop through the natural selection of small, inherited variations that increase the individual's ability to compete, survive, and reproduce.
Is water an Organism ?
Living things need food to grow, they move, respire, reproduce, excrete wastes from the body, respond to stimuli in the environment and have a definite life span. Water, sun, moon and stars do not show any of the above characteristics of living things. Hence, they are non-living things.
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Non-living things are inanimate objects or forces with the ability to influence, shape, alter a habitat, and impact its life. Some examples of non-living things include rocks, water, weather, climate, and natural events such as rockfalls or earthquakes.
Why does life exist on planet Earth ?
Life exists only on Earth because Earth has all the basic necessities that are required for an organism to survive. The temperature and atmosphere of Earth makes life comfortable for the organism.
We tend to accept that it is 'natural' for humans to inhabit the cosmos. We ask ourselves how it could be otherwise. What would be the point of the Universe if it had not allowed us to exist ? If we are here, why not many others could exist in the universe ? Wouldn't it be arrogant to think we are the only intelligent living civilization in the universe ? See also 'Drake equation' in one of the other pages on this website.
We have, however, not yet found the existence of anyone else in the Universe. Life is far from inevitable, according to scientists, and our presence here on Earth may simply be the result of a series of lucky events.
The existence of life on Earth rests on five main pillars:
1. the distance from the Sun, neither too close nor too far away, just enough for liquid water to exist on the planet
2. the magnetic core, which protects the atmosphere from the drag of the solar wind and life from cosmic radiation
3. the atmosphere itself, whose greenhouse effect prevents water from freezing
4. Water, naturally, the universal solvent of life
5, Oxygen, which allows us to breathe
But note that only if these components are combined in the right order, can we have life... similar to the preparation of a good recipe !
Building blocks of life
There are 68 molecules that contribute to the synthesis and primary structures of the 4 fundamental macromolecular components of all cells:
1. nucleic acids
DNA and RNA are produced from the 8 nucleosides. Although deoxyribose (d) and ribose (r) are saccharides, they are an integral part of the energetically charged nucleoside building blocks that are used to synthesize DNA and RNA.
2. proteins
There are 20 natural amino acids used in the synthesis of proteins.
3. glycans
Glycans derive initially from 32, and possibly more, saccharides used in the enzymatic process of glycosylation and are often attached to proteins and lipids, although some exist as independent macromolecules.
4. lipids
Lipids are represented by 8 recently classified categories and contain a large repertoire of hydrophobic and amphipathic molecules.
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Details on the human body can be found on the following website: https://www.britannica.com/science/human-body
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The number of molecular building blocks does not directly infer the relative structural complexity of the repertoire of each component. Not shown are the many different post-synthetic modifications of the molecules within these components.
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Putting things in perspective:
The human body consists of 10^13 cells and 10^14 bacteria
The universe consists of 10^22 stars
The oceans of planet Earth consists of 10^30 organisms
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For life to exist you at least need Carbon (C) and Water (H2O) !
Why Carbon ?
All known life uses Carbon-based organic compounds !
C forms strong chemical bonds with other atoms (eg. H, O, N, S, P, Fe, ....)
C compounds dissolve in water....
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Why Water ?
Life needs a MEDIUM (...)
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Organisms have adapted to
1. Pressure
2. Acidity
3. Salinity
4. Radiation
5. Toxicity
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Interesting videos to watch on YouTube - the 'our planet' series by Sir David Attenborough and the following videos:
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What is an ecosystem ? (source: National Geographyc Society)
An ecosystem is a geographic area where plants, animals, and other organisms, as well as weather and landscape, work together to form a bubble of life.
Ecosystems contain biotic or living, parts, as well as abiotic factors, or nonliving parts.
> Biotic factors include plants, animals, and other organisms.
> Abiotic factors include rocks, temperature, and humidity.
Every factor in an ecosystem depends on every other factor, either directly or indirectly. A change in the temperature of an ecosystem will often affect what plants will grow there, for instance. Animals that depend on plants for food and shelter will have to adapt to the changes, move to another ecosystem, or perish.
Ecosystems can be very large or very small. Tide pools, the ponds left by the ocean as the tide goes out, are complete, tiny ecosystems. Tide pools contain seaweed, a kind of algae, which uses photosynthesis to create food. Herbivores such as abalone eat the seaweed. Carnivores such as sea stars eat other animalsin the tide pool, such as clams or mussels. Tide pools depend on the changing level of ocean water. Some organisms, such as seaweed, thrive in an aquatic environment, when the tide is in and the pool is full. Other organisms, such as hermit crabs, cannot live underwater and depend on the shallow pools left by low tides. In this way, the biotic parts of the ecosystem depend on abiotic factors.
The whole surface of Earth is a series of connected ecosystems. Ecosystems are often connected in a larger biome. Biomes are large sections of land, sea, or atmosphere. Forests, ponds, reefs, and tundra are all types of biomes, for example. They're organized very generally, based on the types of plants and animals that live in them. Within each forest, each pond, each reef, or each section of tundra, you'll find many different ecosystems.
What are the threats to ecosystems ?
Pollution, including the use of chemicals, fossil fuels and plastics, which disrupts the earth's ecosystems, injuring species and changing their habits. Rapidly increasing climate change, which is changing growing patterns, food availability and migration patterns faster than ecosystems and species can adjust.
There are six major threats to an ecosystem:
1. climate change
2. habitat loss and degradation
3. pollution
4. invasive species
5. over-exploitation
6. epidemics/pandemics
