Evolution and Biodiversity Topics

• Theory of Evolution


  Ideas given by Darwin on the theory of natural selection
• Species evolution


  1. Species keep on changing or evolving with time

  2. As the environment changes, the requirements of the organisms also change and they need to adapt to their new environment

  3. Phenomenon of change over a period of time is known as adaptation
• Natural selection


  • Higher changes tend to get naturally selected
  • Lower ones are automatically eliminated
  • Leads to progressive evolution
  • Not all adaptations are able to contribute
• Almost all organisms share a common ancestry with some of the organisms
• All organisms had a common ancestor at some point of time and this kept on diverging since then according to Darwin
• Evolution


  • Gradual and slow process
  • Taken place over a long period of time
  • Billions of years
  • Entire generation of species has been taken over by another
  • Adaptation and changes take a long time to get stabilized
• Observations from Charles Darwin's theories


  • First forms of life in the form of cells appeared about 2000 million years ago on earth
  • Single-celled organisms were followed by multicellular organisms and then invertebrates were formed
  • Different organisms began to invade starting from water and then navigating to land
  • Evolution of the jawless fish
  • Reptiles, amphibians, and some viviparous mammals evolved into existence
• Natural selection


  The mechanism through which living creature populations adapt and change
• Natural selection


  1. Organisms that are able to survive and reproduce with the changing environmental conditions are selected by nature

  2. Organisms that cannot survive are eliminated

  3. Genes responsible for the survival of an organism are passed on to the successive generations
• Individuals in a population are naturally varied, which means they are all unique in some way
• Some people have qualities that are better suited to their environment than others
• Change in a population's heritable features over generations

  A major evolutionary mechanism
• 1. Extinction is a natural process.
  2. The complete disappearance of a species from the earth is called extinction.
  3. It is an important part of evolution.
  4. Species with characteristics like large body size, small population size, feeding at high trophic levels in the food chain, low reproductive rate, etc are more susceptible to extinction.
  5. Natural extinction, mass extinction, and anthropogenic extinction are the three types of extinction processes.
• A species is a group of organisms with similar characteristics and can interbreed to give fertile offspring. Speciation is an evolutionary process of the formation of new and distinct species. The species evolve by genetic modification. The new species are reproductively isolated from the previous species, i.e. the new species cannot mate with the old species.
• Allopatric speciation is the type of speciation caused by geographical isolation. In this, the population is separated by a physical barrier.
• Sympatric Speciation refers to the evolution of new species from the surviving ancestral species in which both species live in the same geographical region.
• Due to some geographical changes, few members of a species get isolated from other members. Later, this isolated group grows in a different land and eventually evolves as a new species with new adaptations according to its environment. Natural selection and genetic drift have a major role to play in this.
• Hybridization is an artificial method of developing a new species. In animal husbandry, two parents from different species are mated to form a third species. Hybridization has numerous impacts on the process of speciation.
• The variety of animals and plants living in a given geographical area is called biodiversity of that geographical area.
•  Kingdom Classification:

  • Monera
  • Protista
  • Fungi
  • Plantae
  • Animalia.
• • Kingdom
  • Phylum
  • Order
  • Family
  • Genus
  • Species
• • Monera
  • These organisms do not have a defined nucleus or organelles and are unicellular.
  • Cell walls present in some organisms of this group.
  • Nutrition: Autotrophic or heterotrophic
  • Examples: Bacteria and blue-green algae
• • Protista
  • Unicellular eukaryotic organisms.
  • Locomotion: By Jair-like cilia or whip-like flagella for moving around in some members.
  • Nutrition: Autotrophic or heterotrophic.
  • Examples: Algae, protozoans {Plasmodium, Entamoeba)
• • Fungi
  • Heterotrophic eukaryotic organisms.
  • Nutrition: Saprophytic they use decaying organic materials as food.
• • Plantae
  • Multicellular eukaryotes with cell walls.
  • Nutrition: Autotrophs use chlorophyll for photosynthesis.
  • • Animalia
  • Multicellular eukaryotes without cell walls.
  • Nutrition Heterotrophs.
• Thallophyta or Algae


  Plants that do not have well-differentiated body design, commonly called algae, predominantly aquatic
• Thallophyta or Algae


  • Spirogyra
  • Ulothrix
  • Cladophora
  • Chora
• Bryophyta


  Amphibians of the plant kingdom, plant body differentiated into stem and leaf-like structures but no specialized tissue for conduction
• Bryophyta


  • Moss (Funaria)
  • Marchantia
• Pteridophyta


  Plant body differentiated into roots, stem and leaves with specialized tissue for conduction of water and other substances
• Pteridophyta


  • Marsilea
  • Ferns
  • Horse-tails
• Gymnosperms


  Plants that bear naked seeds, perennial, evergreen and woody
• Gymnosperms


  • Pines
  • Deodar
• Angiosperms


  Flowering plants, seeds develop inside a modified fruit, plant embryos have cotyledons
• Classification can be carried out based on many factors such as:

  • Presence of nucleus
  • Body design – make up of cells(Single-celled or Multicellular organisms)
  • Production of food
  • Level of the organization in bodies of organisms carrying out photosynthesis
  • In animals – an organization of one’s body parts, development of body, specialized organs for different functions