Evolution 🐛🦋🕊💯

• Evolution:

  Change over a period of time
• Biological Evolution/organic evolution

  The process of gradual changes in the organism to form more and more complex,organised and efficient forms over long period of time
• Darwin's Theory of evolution by natural selection: The idea that all living things have evolved from common ancestors through the process of natural selection.
• Natural Selection: A mechanism whereby individuals with advantageous traits are better able to survive and reproduce than those without them.
• Adaptation: Any inherited characteristic which increases an individual’s chance of survival or reproduction in its environment.
• Variations: Differences between members of a species caused by genetic differences.
• Genetic Variation: Genes can vary within a population due to mutations.
• Heredity: Passing on characteristics from one generation to another.
• Mutation: Changes in DNA sequence that may be passed on to offspring.
• Gene Pool: All genes present in a population at any one time.
• Allele: Different versions of genes found at a particular locus.
• Descent with modification is the idea that all living things are related to each other and that they have evolved due to changing environment.
• 4 theories of mechanisms of Evolution

  1. Lamarck's Theory of Inheritance pf Acquired Characters(Lamarckism)
  2. Darwins Theory of Natural Selection(Darwinism)
  3. DeVries Theory of Mutations(Mutation)
  4. Modern Concept of evolution(Synthetic Theory)
• Lamarcks theory states that organisms can pass on traits acquired during their lifetime to their offspring
• Darwins theory states that individuals with advantageous traits will survive and reproduce more, passing these traits onto future generations through natural selection
• De Vries theory suggests that mutations occur randomly and can lead to new species over time
• Lamarckism

  Certain structures or function of organs change in response to changes in the surrounding environment and are inherited by the offsprings
• Adaptive radiation is the divergence in population due to adaptations
• Basic Facts about Darwinism:

  1. Overproduction/rapid multiplication
  2. Limited space and food
  3. Struggle for existence
  4. Variations
  5. Natural selection and survival of fittest
  6. Inheritance of useful variations
  7. Formation of new species
• Prodigality:

  The inherent tendency of living beings to produce offspring in large number for the perpetuation of their race
• Example of prodigality

  • Bacteria🦠
  • Paramecium
  • codfish 🐠
  • oyster
  • elephant🐘
• Types of struggle for existence:

  1. Intraspecific/intranecine struggle (competition among same species)
  2. Interspecific/internecine struggle(competition among different species)
  3. Struggle with environment (changes of environment such as heat,cold,drought,flood,food, storm,famine,etc)
• The useful variations have selective advantage while harmful variations have selective disadvantage
• Sorting out of individuals with useful variations was called natural selection by Darwin and survival of fittest by Wallace.
• Differential reproduction

  Individuals with useful variations survive, reach adulthood and reproduce offspring while others fail to do so
• speciation

  origin of new species by the gradual modification of older ones
• Drawbacks of Darwinism

  1. Theory of pangenesis
  2. Inheritance of small variations
  3. Existence of vestigial organs
  4. overspeacialisation
  5. Arrival or occurrence of variations
• Modern synthetic Theory of Evolution

  According to this thoery population of a species is the unit of Evolution.

  Natural selection operates not only on the genome of any single individual of a species,but on the gene pool of a population.
• Mendelian population:

  A group of individuals of species that live in a geographical area at a particular time and interbreed freely
• Characteristics of mendelian population

  •similar genetic constitution of the members

  •All organism contribute to the same gene pool

  •Random mating among the members allowing gene flow

  •no preferential interbreeding
• Hardy Weinberg principle describe the relationship between gene frequencies and genotype frequencies of allele in a gene pool.