Evolution: Life On Earth Is One Big Extended Family
- In 1858, Charles Darwin and Alfred Russel Wallace independently proposed a theory of biological evolution to explain the diversity of life on Earth. Since then the fossil record and DNA studies have added, and
continue to add, overwhelming support for this view of life's history. Evolution today is one of the best documented and widely accepted principles of modern science. Life on Earth has changed dramatically through
time. The theory of evolution proposes selection and other natural events over millions of generations, living things diversity, branching from one species into many. This means that all living things are related to one
another through common ancestry with earlier, different life forms. In other words, if you follow your family tree far enough back in time, you will find a common ancestor not only with every other living thing, but with
every thing ever lived.
Life's family tree
- This Tree of Life is drawn from the human point of view. That is why humans are the final branch and most Tree of Life's details are found in vertebrates (animals with a backbone). A Tree of Life drawn from a bacterial
point of view would look very different!
- Trace any branch back through time to see how it connects to any other of life's major branches. Use the curved time scale to find when their common ancestor lived. Five mass extinctions are marked by an abrupt
decrease in life's diversity, followed by renewed diversity (flowchart): 1) Oceans rust: Bacteria; Archaea; Eukaryotes; Plants; Red Algae; Amoebas; Fungi; Sponges; Placozoans; Ctenophores; Corals; Acoel Flatworms; 2)
Global Ice Age: Protostomes; Echinoderms; 3) Cambrian Explosion: Starfish; Hagfish; Sea squirts; Lancelets; Armored fish - extinct; Etc; 4) Mass Extinction: Sharks; Salmon; Fish; Herring; Etc; 4) Mass Extinction:
Coelacanth; Lungfish; Amphibians; Reptiles; 5) Mass Extinction: Birds; Mammals.
All the major and many of the minor living branches of life are shown on this diagram, but only a few of those that have gone extinct are shown. Example: Dinosaurs - extinct | Leonard Eisenberg. All rights reserved -