Search results
slideserve.com
- The fossilrecord provides snapshots of the past which, when assembled, illustrate a panorama of evolutionary change over the past 3.5 billion years. The picture may be smudged in places and has bits missing, but fossil evidence clearly shows that life is very, very old and has changed over time through evolution.
evolution.berkeley.edu › lines-of-evidence › fossil-evidence
People also ask
Why are fossils important?
Does the fossil record provide evidence for evolution?
How do fossils show equine evolution?
What do fossils tell us about life?
Fossil evidence. Nicholas Steno’s anatomical drawing of an extant shark (left) and a fossil shark tooth (right). The fossilrecord provides snapshots of the past which, when assembled, illustrate a panorama of evolutionary change over the past 3.5 billion years.
- Transitional features - University of California, Berkeley
And indeed we do find evidence of this transition in the...
- The fossil record provides evidence for evolution.
The Evolution Lab contains two main parts. In the first,...
- Transitional features - University of California, Berkeley
- Overview
- Key points:
- Introduction
- Evolution happens on large and small scales
- The evidence for evolution
- Anatomy and embryology
- Homologous features
- Analogous features
- Determining relationships from similar features
- Molecular biology
Evidence for evolution: anatomy, molecular biology, biogeography, fossils, & direct observation.
•Evidence for evolution comes from many different areas of biology:
•Anatomy. Species may share similar physical features because the feature was present in a common ancestor (homologous structures).
•Molecular biology. DNA and the genetic code reflect the shared ancestry of life. DNA comparisons can show how related species are.
•Biogeography. The global distribution of organisms and the unique features of island species reflect evolution and geological change.
•Fossils. Fossils document the existence of now-extinct past species that are related to present-day species.
•Evidence for evolution comes from many different areas of biology:
•Anatomy. Species may share similar physical features because the feature was present in a common ancestor (homologous structures).
•Molecular biology. DNA and the genetic code reflect the shared ancestry of life. DNA comparisons can show how related species are.
•Biogeography. The global distribution of organisms and the unique features of island species reflect evolution and geological change.
•Fossils. Fossils document the existence of now-extinct past species that are related to present-day species.
•Direct observation. We can directly observe small-scale evolution in organisms with short lifecycles (e.g., pesticide-resistant insects).
Evolution is a key unifying principle in biology. As Theodosius Dobzhansky once said, “Nothing in biology makes sense except in the light of evolution.”1
But what, exactly, are the features of biology that make more sense through the lens of evolution? To put it another way, what are the indications or traces that show evolution has taken place in the past and is still happening today?
Before we look at the evidence, let's make sure we are on the same page about what evolution is. Broadly speaking, evolution is a change in the genetic makeup (and often, the heritable features) of a population over time. Biologists sometimes define two types of evolution based on scale:
•Macroevolution, which refers to large-scale changes that occur over extended time periods, such as the formation of new species and groups.
•Microevolution, which refers to small-scale changes that affect just one or a few genes and happen in populations over shorter timescales.
Microevolution and macroevolution aren’t really two different processes. They’re the same process – evolution – occurring on different timescales. Microevolutionary processes occurring over thousands or millions of years can add up to large-scale changes that define new species or groups.
In this article, we'll examine the evidence for evolution on both macro and micro scales.
First, we'll look at several types of evidence (including physical and molecular features, geographical information, and fossils) that provide evidence for, and can allow us to reconstruct, macroevolutionary events.
Darwin thought of evolution as "descent with modification," a process in which species change and give rise to new species over many generations. He proposed that the evolutionary history of life forms a branching tree with many levels, in which all species can be traced back to an ancient common ancestor.
In this tree model, more closely related groups of species have more recent common ancestors, and each group will tend to share features that were present in its last common ancestor. We can use this idea to "work backwards" and figure out how organisms are related based on their shared features.
If two or more species share a unique physical feature, such as a complex bone structure or a body plan, they may all have inherited this feature from a common ancestor. Physical features shared due to evolutionary history (a common ancestor) are said to be homologous.
To give one classic example, the forelimbs of whales, humans, birds, and dogs look pretty different on the outside. That's because they're adapted to function in different environments. However, if you look at the bone structure of the forelimbs, you'll find that the pattern of bones is very similar across species. It's unlikely that such similar structures would have evolved independently in each species, and more likely that the basic layout of bones was already present in a common ancestor of whales, humans, dogs, and birds.
Some homologous structures can be seen only in embryos. For instance, all vertebrate embryos (including humans) have gill slits and a tail during early development. The developmental patterns of these species become more different later on (which is why your embryonic tail is now your tailbone, and your gill slits have turned into your jaw and inner ear)2 . Homologous embryonic structures reflect that the developmental programs of vertebrates are variations on a similar plan that existed in their last common ancestor.
Sometimes, organisms have structures that are homologous to important structures in other organisms but that have lost their major ancestral function. These structures, which are often reduced in size, are known as vestigial structures. Examples of vestigial structures include the tailbone of humans (a vestigial tail), the hind leg bones of whales, and the underdeveloped legs found in some snakes (see picture at right).3 .
To make things a little more interesting and complicated, not all physical features that look alike are marks of common ancestry. Instead, some physical similarities are analogous: they evolved independently in different organisms because the organisms lived in similar environments or experienced similar selective pressures. This process is called convergent evolution. (To converge means to come together, like two lines meeting at a point.)
For example, two distantly related species that live in the Arctic, the arctic fox and the ptarmigan (a bird), both undergo seasonal changes of color from dark to snowy white. This shared feature doesn’t reflect common ancestry – i.e., it's unlikely that the last common ancestor of the fox and ptarmigan changed color with the seasons4 . Instead, this feature was favored separately in both species due to similar selective pressures. That is, the genetically determined ability to switch to light coloration in winter helped both foxes and ptarmigans survive and reproduce in a place with snowy winters and sharp-eyed predators.
In general, biologists don't draw conclusions about how species are related on the basis of any single feature they think is homologous. Instead, they study a large collection of features (often, both physical features and DNA sequences) and draw conclusions about relatedness based on these features as a group. We will explore this idea further whe...
Like structural homologies, similarities between biological molecules can reflect shared evolutionary ancestry. At the most basic level, all living organisms share:
•The same genetic material (DNA)
•The same, or highly similar, genetic codes
•The same basic process of gene expression (transcription and translation)
•The same molecular building blocks, such as amino acids
These shared features suggest that all living things are descended from a common ancestor, and that this ancestor had DNA as its genetic material, used the genetic code, and expressed its genes by transcription and translation. Present-day organisms all share these features because they were "inherited" from the ancestor (and because any big changes in this basic machinery would have broken the basic functionality of cells).
Oct 31, 2023 · Fossils provide solid evidence that organisms from the past are not the same as those found today; fossils show a progression of evolution. Fossils, along with the comparative anatomy of present-day organisms, constitute the morphological, or anatomical, record.
Learn about the theory of evolution and how it is supported by instances of direct observation, the existence of homologies and fossils, and certain biogeographical patterns. Key points: Evidence for large-scale evolution ( macroevolution) comes from anatomy and embryology, molecular biology, biogeography, and fossils.
- I understand that a fossil not being found doesn't mean the organism didn't exist, simply that it ha...There are multiple possible explanations for those examples you cite. The fossils or their age could have been misidentified. It is also possible t...
- This article admits, under Evidence For Evolution: Fossil Record, that the record is incomplete. So ...Scientific theories are never proven, proofs are for mathematics. The theory of gravity and quantum mechanics are not proven but but you do not que...
- the possible explanations for the examples you may cite not the fossils or the age you could also ha...The identified age is counted as evidence for evolution. In the pictures showing the evolution of horses, there are dates shown. Why do you think t...
Fossils provide solid evidence that organisms from the past are not the same as those found today; fossils show a progression of evolution. Fossils, along with the comparative anatomy of present-day organisms, constitute the morphological, or anatomical, record.
Fossils showing equine evolution. Image credit Wikimedia , CC BY-SA 3.0 . Structural evidence can be compared between extant (currently living) organisms and the fossils of extinct organisms.
