Evidence of Evolution

• Evidences of Evolution

  1. Fossil Records
  2. Artificial Selection
  3. Geographic Distribution
  4. Homologous and Analogous Structure
  5. Molecular Homologies
  6. Embryology
• Fossil Records


  • Different traces or remains of an organism changed over time and preserved by natural process.
• Fossils

  • are the remnants of a creature from the primitive times. They are generally formed when an organism is covered by sediments that can harden into sandstones, slate, mudstone, or flint. Organisms also fossilized when buried in volcanic ash or entombed in tar or tree sap.
• According to experts, fossil provides direct evidence for evolution because it can tell what has happened. By simply studying fossils occurring in different strata of rocks, geologists can reconstruct evolutionary change time and course. It can show that variation in time has happened. When fossils are set in the order of how old they are, we can directly compare their body structures. Through these, fossils' experts can confirm that species are not fixed but can evolve into other species over time.
• Artificial Selection


  Species Variation occurred through mutation and sexual reproduction, but humans select features that are beneficial.
• Steps of Artificial Selection:

  • Choose a species.

  • Choose a trait of interest.

  • Breed them together.

  • Identify which individual shows the desired trait strongly.

  • Breed that trait for the next generation.

  • Repeat 4 & 5 steps for many generations
• Geographic Distribution


  It is the natural arrangement of various species of living organisms in their appropriate habitats on the Earth.
• The study of geographic distribution of all species, and abiotic factors affecting their distribution is known as biogeography.
• Convergent Evolution


  when two different species that do not share a recent common ancestor develop similar traits. This occurs because the two species live in similar environments and fill a similar role within it. Therefore, each species independently evolves to have some of the same traits because they help that species survive and reproduce in its environment
• Divergent Evolution

  when individuals in one species, or closely related species, acquire enough variations in their traits that it leads to two distinct new species. Divergent evolution can occur when members of the same species develop different traits that allow them to fill different niches in their environment. If the differences become great enough it can eventually lead to an entirely new species evolving. This is what happened with the different finch species that Darwin observed on the Galapagos Islands
• Homologous structures 


  are similar physical features in organisms that share a common ancestor, but the features serve completely different functions. An example of this are the limbs of humans, cats, whales, and bat
• Analogous Structure


  same function, different structure, do not share common ancestor
• The discipline of comparative anatomy is vital in understanding relationships among creatures
• Homologous structures

  Have similar embryonic origins
• Analogous structures


  Are identical only in function
• Comparable structures

  • Birds' and flies' wings
  • Birds' wings and the foreleg of a frog
• Birds' and flies' wings serve the same function but have different embryonic origins
• Birds' wings are made of bone and flesh and flies' wings are mainly composed of non living chitin
• Birds' wings and the foreleg of a frog have different functions but their embryonic origins are alike</b>
• For some comparative anatomists, homologous structures are important because they imply an evolutionary linkage between two species. However, comparing the anatomy and the development of organisms reveals a unity of plan among those strictly connected. The more species have the same functions in terms of body, the nearer they are related.
• Analogous Structure


  are similar structures in organisms without shared ancestry. These structures evolved independently to serve the same purpose.
• Molecular homologies


  are similarities between species on the molecular level. Identifying this involves looking at the DNA of different species and comparing them to each other. If the same DNA sequences are found in different species, that means they probably came from a common ancestor
• Embryology


  A study of organism's embryonic progress provides further clues to its evolutionary past. Scientists proclaimed that "ontogeny summarizes phylogeny." Simply means that this theory proposes that if a certain organism undergo its embryonic development (ontogeny), it duplicates (recapitulates) the stages in its evolutionary history (phylogeny). For example, during your development, human folds in the neck area are referred to as pharyngeal pouches, which in some animals become gills. This notion of embryology as an "instant replay" of evolution has been called the biogenetic law
• Human embryo has a tail at the 4th week which disappears during the 8th week. Pharyngeal pouches become gills in fish, parts of throat/ears in humans. Embryos of vertebrates develop in the same way.