Evolution

Evolution at its best

Is Evolution a Theory or a Fact?

A theory is a system of ideas that is intended to explain, or answer a series of questions. A theory explains the natural world, based on facts that have been repeatedly confirmed through a wide series of observations and experiments, but a theory is not based upon guesses but actual scientific evidence. A fact is something that has actually occurred. With a fact it is verifiable, or testable. With that said, Evolution is theory because it was never physically observed. There has been many observations supporting that living things evolved over a long period of time into what we currently see and interact with today.

History of the Earth

Below you will find a URL Link that will give you a visual of the following events in order. Also you may like to visit the URL Link to learn more about how Evolution Evolved from beginning to the end.


  1. 4,600 mya (Million Years Ago) - The earth forms and is impacted by meteorites and comets.
  2. 3,800 mya - Precursors of DNA form.
  3. 3,500 mya - Unicellular life evolves (bacteria)
  4. 555 mya - Multi-cellular marine organism are common. The diverse assortment of life includes bizarre looking animals.
  5. 500 mya - Fish like vertebrates evolve, and invertebrates.
  6. 450 mya - Arthropods begin to move onto land. Their descendants evolve into scorpions, spiders, mites and millipedes. (Insects)
  7. 420 mya - Land plants began to evolve, changing earths landscape from dirt to green vegetation.
  8. 360 mya - Four limed vertebrates move onto the land as seeding plants and large forest are beginning to appear. Also the oceans are now supporting large reefs.
  9. 250 mya - Pangaea Forms
  10. 248 mya - 90% of all the marine life and 70% of the terrestrial life (Land) go extinct.
  11. 225 mya - Dinosaurs and mammals evolve. Pangaea has already begun to break apart.
  12. 130 mya - Flowers evolve
  13. 65 mya - Dinosaurs go extinct
  14. 4 mya - Early hominid ("Lucy")
  15. 130 Thousand Years Ago - Modern humans evolve.

As you can see that from 4,600 mya to 130,000 years ago, we humans have evolved into who we are today.

http://evolution.berkeley.edu/evolibrary/article/evo_13

Evolution: It's a Thing - Crash Course Biology #20

Fossils

The above link will show you different pictures of fossils. As you browse through the pictures you might wonder how they actually know how old the fossils are. Well scientist date some fossils by relative dating. With relative dating scientist look at the rocks and sediment that are positioned on the earth in layers. In most cases the oldest layer of rock will be at the bottom and the newest will be at the top. In some cases, this method won't work. The places that relative dating won't work will be in a badly disturbed area, including a place that has experienced a natural disaster, like an earthquake. By looking at the layers scientist look at the order the sediments were deposited in and will tell them relatively how old it is, but we cannot tell and absolute age of the fossil because it is hard to date rock. Another type of fossil dating is absolute dating. With absolute dating, it tells us which sediments were deposited first, but it will tell us the exact age of the sediment and the fossil. To tell how old the sediment is they can use carbon dating. Carbon dating is only able to be done to matter that has once been living and presumed to be in the equilibrium with the atmosphere, taking in carbon dioxide from the air and photosynthesis.

Fossil Evidence of Evolution

Fossil records provide snapshots of the past, and illustrates the panorama of evolutionary change over the past four billion years. For instance, Nicholas Steno's anatomical drawing of an extant shark that was found, and a fossil shark tooth, shows that the fossil teeth indeed came from the mouths of one living sharks and also occurs in some modern day sharks. Another example would be the ammonite fossil, which shows punctures that some scientists have interpreted as some sort of bite mark of a mosasaur, a type of predatory marine reptile. The mosasaur lived at the same time as the ammonite. At the cellular level fossils can tell us about growth patterns in ancient animals. For instance, the thigh bone of the duckbill dinosaur Maiasaura. There are white spaces showing that there were lots of blood vessels running through the bone, which indicates that it was a fast growing bone. This fossil also shows that there was a seasonal pause in the animals growth. Some transitional forms would be the Pakicetus nostirls at the front of the skull and now the gray whale that we are formidably with today. For instance the nostril placement in the Aetiocetus is intermediates between the ancestral form of Pakicetus and the modern day gray whale.

Homologous and Vestigial Structures

Evolutionary theory has predicted that organisms that are closely related will share some similarities that are linked to their ancestry. Similar characteristics due to them being related is called homologous. Homologous can be revealed by comparing the anatomies of different living things, by looking at the cellular similarities and differences, studying embryological development, and also by studying vestigial structures within and individual organism. A vestigial structure is a feature that a organism has inherited from its ancestry and is now less functional than in the past years. Typically, vestigial structures are formed when a lineage experiences a different types of environmental factors than their ancestors experienced.

Embryology

Embryology is one type of evidence of evolution, which is the study of embryos. An embryo is an unborn animal or human. Embryos of many different kinds of animals, mammals, birds, reptiles and fish look very similar and it is often difficult to tell them apart. Many traits of one type of animals appear in the embryo of another type of animal. For example, a fish embryos and human embryos both have gill slits, but in fish they develop into gills, and in humans they disappear before birth.

DNA

DNA affects how an organism looks, how it behaves, and its physiology. Due to evolution it has changed the DNA in organism which has caused changes in all aspect of the life of the organism.

Biogeography

Bio Geography is the study of how species are scattered across the planet, and how they got that way. Wallace, a prisoner of scientific parentheses as in the theory of evolution, came to much of the same conclusion that Darwin published in the Origin of Species: bio geography was simply a record of inheritance. As species colonized new habitats and their old ranges were divided by mountain ranges or other barriers, that took on the distributions they have today. Later years they then finalized the idea of Pangaea or in other teams the super continent.