Evidence of Evolution: Evolution is a genetic transformation of a large group of living organisms over time. It clarifies how life changed and diversified from one or more common ancestors of a species. Natural selection is a gradual process that leads to evolution. Natural selection increases the frequency of advantageous inherited traits (allowing them to survive and reproduce) and decreases the frequency of detrimental inherited traits. 

Jared Diamond once said, “Biology is science. Evolution is the concept that makes biology unique”. So many kinds of evidence of evolution have come with a scientific understanding of biological evolution. Fossils of long-extinct animals are one common form of evidence of evolution.

Define Evidences of Evolution

“Scientists proposed many pieces of evidence through which the evolution of life forms can be proved. Several different lines of evidence convinced Darwin and his contemporary scientists that the modern organisms arose by evolution from more ancient forms” (Source: Arihant Biology Handbook)

Categories for Evidences of Evolution

The evidence of evolution can be categorized as:
A. Direct evidence of evolution
B. Indirect evidence of evolution.

A. Direct evidence of evolution: The visible evidence that takes us back in time and shows how an organism has changed is the direct evidence of evolution. Example: Paleontological evidence (Fossils). Fossil gives us traces of reptiles evolving into birds.

B. Indirect evidence of evolution: The evidence that shows some kind of evolutionary connection between organisms is indirect evidence of evolution.Example: anatomical, embryological, morphological, and molecular.

What are the Evidence of Evolution?

Many necessary pieces of evidence are present in our nature which shows that evolution has indeed taken place on Earth. Some significant convincing evidence for the descent with modification comes from Paleontology, Morphology and Comparative Anatomy, Embryology, Molecular patterns.

Paleontological Evidence

a. Paleontology is the study of the history of life on Earth based on fossils.
b. Fossils are the remains of plants, animals, bacteria that lived a long time ago and have been replaced by rocky material or preserved in rock.
c. The evidence of evolution, if gained from the knowledge of fossils, is called paleontological evidence.
d. The fossil record provides evidence that species have changed over time.
e. Based on fossil evidence, scientists can recreate the physical appearance of species that are no longer alive on Earth.
f. After an animal dies, any soft tissues animals do not eat break down. Only the dead animal’s complex parts, such as bones, shells, and teeth, remain. Under rare conditions, these parts become fossils.
g. The connections, compression and impressions, intact preservation, petrification, casts, and molds are various modes of fossilization.

Fig: The Fossil

h. Relative-age dating helps scientists determine the relative order in which species have appeared on Earth over time.
i. The geologic time scale is a chart that divides Earth’s history into different time units.

Fig: Geologic Time Scale

j. The fossil record contains evidence of the appearance of many new species over time.
k. Biological evolution is the change over time in populations of related organisms.
l. The fossil record is evidence that horses descended from organisms for which only fossils exist today.

Fig: Evolution of Horse

Morphological and Comparative Anatomical Evidence

Morphology refers to the external structure of an organism, and anatomy refers to the internal structure and functional organisation. By comparing the morphology and anatomy, we can find the similarities and differences between the present living and remote extinct organisms.

a. Homologous organs are body parts of organisms similar in structure and position but different in function.
1. Homologous organs in plants: The tendrils of Vitis, spines of Duranta, phylloclade of Opuntia and rhizome of ginger are all modified stems. These are all stems that have been modified into different structures to perform various functions, but all these share a common ancestry.
2. Homologous organs in animals: The forelimbs of the wings of a bird, flipper of a whale, hands of a man, etc., are different sizes, but their placement and structure suggest common ancestry.

Fig: Homologous Organs

b. Analogous organs are body parts of organisms that perform a similar function but differ in structure.
1. Analogous organs in plants: Phylloclade of Opuntia is a modified stem, and phyllode of Acacia is a modified petiole that performs the same function as photosynthesis. They both are analogous organs.
2. Analogous organs in animals: Wings of an insect, bird and bat can fly, but they are different in origin and internal structure.

Fig: Analogous Organs

c. Vestigial organs are body parts that have lost their original function through evolution. Some examples of vestigial organs in the human body are coccyx (tailbone), nictitating membrane (\(3\)rd eyelid), caecum, vermiform appendix, canines, wisdom teeth, body hair, auricular muscles, mammary glands in males, etc. These organs are also found in some other animals like splint bones in horses, hindlimbs and pelvic girdles in python, wings, and feathers in flightless birds, etc.

Fig: Vestigial Organs

Embryological Evidence

a. Embryology is the study of one type of evidence of the evolution of vertebrates. An embryo is unborn animal or human young in its earliest phases.
b. The comparative study of embryos of fishes, amphibians, reptiles, birds, and mammals are observed at the primary stage that they will appear almost similar.
c. The zygote is the unicellular cell through which all triploblastic animals develop is similar in all cases. The zygote in all cases gives rise to morula, then blastula and then gastrula through cell division.
d. The structure of early embryos in different vertebrates like mammals, birds, reptiles, fish, etc., look almost similar in all cases. In their embryos, pharyngeal gill slits, tail, notochord, etc., are present.
e. They also have three types of kidneys: pronephros, mesonephros and metanephros during developmental stages.
f. Ernst Haeckel proposed Recapitulation theory or Biogenetic law. The law states that ‘Ontogeny Repeats Phylogeny’, which means that the stages of development for an animal embryo passes through its ancestral history. This theory is a theory of development and evolution.

Fig: Comparative Account of Several Vertebrate Embryos

Molecular Evidence

a. Molecular evolution is the process by which change in the sequence composition of cellular molecules such as DNA, RNA, and proteins, gene structure and function takes place across generations.
b. Scientists can study the relationships among organisms by comparing genes and proteins among living species.
c. Organisms with similar DNA share common ancestors.
d. DNA is used as a molecular clock to estimate when organisms diverged. Fewer differences in DNA sequences indicate closeness in evolution. Larger differences indicate early divergence.
e. DNA has only four nitrogenous bases that code for all living things on Earth.
f. Adenine, Guanine, Cytosine and Thymine, all nitrogen bases line up in a specific order and a group of three, or codon, code for one of \(20\) amino acids found on Earth. The order of these amino acids determines what protein is going to form.
g. Over the ages, the genetic code has passed unchanged from parent to offspring.
h. Amino acid sequencing is probably the strongest evidence for relationships among organisms.

Fig: Molecular Evolution

Importance of Evidence of Evolution

1. Evidence of evolution shows how modern living things evolved from ancient life forms that do not exist on Earth.
2. The evolutionary history of organisms is essential for classification. So, evolution and classification are interconnected.
3. Evolutionary relationships among species help scientists to choose the most appropriate organisms for the study of diseases.

Summary

The evidence of evolution is one of the main foundations of recent biological theory. Moreover, it is the only way that may prove all the theories of evolution. Thus, we know that organisms have a common origin through evidence of evolution, and their differences result in modifications. Moreover, the evidence of evolution can be discovered by various methods. It involves the comparison of data, fossil records, anatomy, embryology, and biological molecules.

FAQs on Evidence of Evolution

Q.1. What does the Evidence of Evolution state?
Ans: Evidence of evolution states how modern living things evolved from ancient life forms that do not exist on Earth.

Q.2. What are the major functions of Evidence of Evolution?
Ans: The evidence of evolution is one of the elemental keystones to recent biological theory. Moreover, it is the only way that may prove all the theories of evolution.

Q.3. What is the best theory that explains the Evidence of Evolution?
Ans: The best theory that explains the Evidence of Evolution is the fossil records from early to recent.

Q.4. Explain Evidence of Evolution with an example?
Ans: Homologous organs are body parts of organisms similar in structure and position but different in function. For example, the forelimbs of the wings of a bird, flipper of a whale, hands of a man, etc., are different sizes, but their placement and structure suggest common ancestry.

Q.5. Give some examples of vestigial organs present in humans?
Ans: Some examples of vestigial organs in the human body are coccyx (tailbone), nictitating membrane (\(3\)rd eyelid), caecum, vermiform appendix, canines, wisdom teeth, body hair, auricular muscles, mammary glands in males, etc.

Q.6. What is the most direct Evidence of Evolution?
Ans: The most direct Evidence of Evolution is the fossil records from early to recent.

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