Evolution is a theory that explains how life on earth developed and diversified over millions of years. The most compelling evidence for evolution in the fossil record comes from transitional fossils, which show the gradual change between two different species. Fossils provide evidence for evolution because they are the remains of ancient organisms that once lived on Earth. These fossils give scientists clues about how species have changed over time and how new species may form in the future.
What Fossils Tell Us?
Fossils may tell us how species have changed over time and how new species may form in the future. They are the remains of ancient organisms that once lived on Earth. Fossils provide evidence for evolution because they show changes between two different species, transitional fossils give scientists clues about how life developed and diversified over millions of years.
Permineralization is a process of fossilization that occurs when the organism is covered by sediment or volcanic ash and then heated.
Fossils from permineralization are found in limestone deposits. These fossils include an entire fossilized tree, soft tissues of leaves, flowers and fruits as well as insect wings that were trapped while these organisms were still alive.
Permineralization requires a lot more time than other types of fossilization so when this type occurs you can infer how long ago the extinction event occurred based on how old the associated rock formation is. For example, if scientists find permineralization they know it was over 56 million years ago because at that point North America had been joined with South America for far longer than today meaning there would have been much higher levels of rainfall which caused the formation of the limestone containing these fossils.
Fossils may also consist of the marks left behind by the organism. Trace fossils include tracks and trails, burrows, borings (e.g., in wood), root imprints, dung or egg impressions on the ground.
The Fossil Record
The fossil record is the evidence that fossils provide of how living organisms have changed over time. The earth’s geological history spans about four billion years and records a vast number of life forms.
There are three important factors to consider when thinking about the fossil record:
- Natural disasters can alter or destroy all traces, so not every organism will be preserved in sediments through geologic time;
- Most organisms do not produce hard parts such as shells or bones which means they may leave behind no trace at all – soft-bodied animals would only become part of the rock if their remains were buried by sediment before decaying away;
- Even where an organism leaves some form of trace there may also exist gaps because we’ve only found out.
Evidence for Evolution
Fossils provide solid evidence that organisms from the past have evolved and have given rise to the organisms we see today.
Fossils provide evidence of change in life forms over time, they show how one species can evolve from another over many years.
There are three main ways that fossils reveal evolution:
- Fossil record provides a snapshot of an ancestor’s anatomy at various points in its evolutionary history. The fossil record is incomplete because only hard parts, such as bones or shells, usually survive long enough for us to find them. However, this doesn’t mean there isn’t any evidence left behind after all! There exist plenty of soft tissue substances like feathers or fur which can be preserved under certain conditions (like cementing). Extraordinary cases include amber where even insects frozen inside their own excretion can be found.
- Indirect evidence for evolution is also present in fossils such as how some species are restricted to islands, while others have managed to invade their territories successfully.
- Finally, the transitional forms of a fossil provide strong evidence for an ancestor’s evolutionary history because they show how one animal evolved into another over time.
The process of a once-living organism becoming a fossil is called fossilization. This process occurs over time and is usually a slow, gradual one that can take as long as ten thousand years or more.
Fossils are made of hard tissues such as bone or shell since these do not decay easily
Soft tissues like muscle tissue will eventually rot away completely before they have the chance to become fossils
Most fossils are preserved in one of five processes and these are:
- preserved remains
- molds and casts
Compression– some fossils form when their remains are squished and then fossilized. Squishing them helps to extract liquids from the tissues, which leaves behind a more solid set of remains
Compression fossils can be found in rocks that formed when an animal was buried by sediments or muds. Compressed fossils are rarer than other types because they must be covered quickly with sediment.
Permineralization– is another process that fossilizes a specimen. It is mostly used for bone fossils and it involves minerals flowing into the spaces within that make up the bone. The permineralization process can take many years, because of how long it takes to form mineral crystals in those spaces. Permineralized bones are mainly found near hot springs or geys.
Preserved remains– The rarest form of fossilization is the preservation of original skeletal remains. These types of fossils are rare because the organism must be buried quickly by sediment or muds to prevent decay, and then covered over time with more of these materials.
Molds and casts-In some cases, the original bone or shell dissolves away, but the impression that it left behind in the surrounding rock is preserved. This may result from chemicals, such as when an organism’s body fluids react with minerals to form a type of stone called agate. The remaining hollow mold or cast is like a negative imprint of the original animal and can only be seen by filling in its outline with plaster.
Replacement– When permineralization and replacement occur together, the organism is said to have undergone petrification. In most cases, this is a rare occurrence. But petrification can be fairly common in areas where there are very wet conditions and great expanses of time. However, replacement can occur without permineralization. For instance, a bone may decompose but the organic molecules that make up its structure can be replaced by silicates from groundwater.