Evidence of Evolution

Evidence of Evolution

• Fossil records are hardened remains or imprints of organisms that existed long ago.
• They are preserved in snow and sedimentary rocks.
• Fossil records determine the history of life on Earth.
• Radio isotope dating is used to analyze fossil records.
• Biochemical similarities indicate organisms are composed of the same types of molecules like carbohydrates, lipids, proteins, and nucleic acids, and store energy as ATP.
• Molecular records indicates all organisms store hereditary information in DNA.
• Comparative anatomy indicates or studies similarities and differences in structures of different organisms
• Ferns have well developed structures (true structures such as leaves, stem)
• Mosses have structures resembling leaves, stem and roots.
• The arm of a man, the flipper of a whale, the leg of a cat and the wing of a bird are used for different purposes, yet the skeletal structure reveals a similar bone arrangement (pentadactyl plan).
• Embryology shows the early embryos of all land vertebrates (Pisces, amphibian, reptiles, birds and mammals) pass through:
  • Gill slit stage (which make them resemble fishes).
  • Has tail at a certain stage.
• Embryological features show all vertebrates have a common ancestor, because of their extinct relatives.
• Progressive complexity in their structure from fishes (simplest vertebrate class) to mammals, the most complex one is an example of comparative anatomy.
• Evolution of modern horse (equus) from the dawn horse eohippus (first known ancestor) 60 million years ago, is an example of fossil records.
• Plants exhibit an evolutionary trend: Schizophyta, thallophyta, bryophyte, tracheopyhta.
• Vertebrates exhibit an evolutionary trend: Pisces, amphibian, reptiles, aves, mammalian.
• Giraffes evolved from short neck ancestors.

Modern View of Evolution (Neo Darwinism)

• Mutation, gene flow and genetic drift and other natural forces are responsible for evolutionary change.
• Genes are discrete units of inheritance that determine hereditary characteristics.
• Genetic drift is the spread of genes more than others through change.
• Gene flow: recombination and spreading of gene in various ways in a population.
• Mutation is a random change in genetic formation.
• Types of mutation:
  • Gene mutation
  • Chromosome mutation
• Mutation results in variation.
• Hugo De Vries propounded the mutation theory of organic evolution.
• A gene is a segment of a DNA molecule.

Pattern of Evolution

• Divergent evolution: More species evolve as offshoot of a single ancestral species
• Convergent evolution: Similar looking organism arises from different ancestral species
• Co-evolution