Evolution

• Macroevolution


  Genotypic changes in a population level through time
• Macroevolution


  Can be seen over a few generations, used interchangeably with the term speciation

  
• Macroevolution

  Creation of new species and taxonomic groups, Diversification of species (divergent evolution), Accumulation of traits due to series of microevolution
• Macroevolution: Patterns in the history of life

  
• Macroevolution


  The study of evolutionary changes occurring at the level of species and above, explores the broader patterns and processes of evolution over long periods of time

  
• Speciation


  The formation of new species
• Macroevolution generally refers to evolution above the species level

  
• There are no firsthand accounts to be read, instead we reconstruct the history of life using all available evidence: geology, fossils, and living organisms (similarities)
• Basic evolutionary mechanisms like mutation, gene flow (migration), genetic drift, and natural selection are at work and can help explain many large-scale patterns in the history of life
• Taxonomical groups go from the most inclusive to more exclusive (species level)
• Speciation events are seen through Phylogenetic tree/cladograms
• Understanding phylogenies is like reading a family tree, the root represents the ancestral lineage, and the tips represent the descendants
• When a lineage splits (speciation), it is represented as branching on a phylogeny
• Phylogenies trace patterns of shared ancestry between lineages
• A clade is a grouping that includes a common ancestor and all the descendants (living and extinct) of that ancestor
• Clades are nested within one another, forming a nested hierarchy
• The Linnaean system of classification assigns every organism a domain, kingdom, phylum, class, order, family, genus, and species, which is not based on evolution
• Biologists are switching to a classification system that reflects the organisms' evolutionary history
• Speciations are seen via Phylogenetic tree/cladograms
• Patterns in macroevolution

  • Stasis
  • Character change
  • Lineage-splitting (or speciation)
  • Extinction

  
• Stasis means that lineages don't change much for a long time, some are called living fossils
• Character change can happen quickly or slowly, in a single direction or reverse itself
• Patterns of lineage-splitting can be identified by constructing and examining a phylogeny
• Extinction is extremely important in the history of life, it can be frequent or rare, or occur simultaneously across many lineages (mass extinction)
• The geologic time scale (GTS) is a system of chronological dating that relates geological strata (stratigraphy) to time
• Fossil record refers to the placement of fossils throughout the surface layers of the Earth
• Mass extinction is the extinction of a large number of species within a relatively short period of geological time
• A population is a group of individuals of the same species occupying a particular habitat
• The habitat includes the geographical place where an organism lives and its interactions with other organisms
• Each population has a gene pool which is the sum of genes in a population at a given time
• Evolution is the permanent change in gene frequencies within a population
• Population genetics is the study of genetic variability within a population and of the forces that act on it
• Natural selection is a biological theory that explains why organisms seem to match their environmental niches so well
• Each individual is subjected to several selection pressures at any point of its life, affecting its chance of survival and reproduction
• The main types of natural selection in a population

  • Stabilizing selection
  • Disruptive selection
  • Directional selection
  • Sexual selection
  • Polymorphism
• Artificial selection is the process of intentional or unintentional modification of a species through human actions which encourage the breeding of certain traits over others
• Speciation refers to the evolutionary process of formation of a new species from previously existing species
• Evolution can be studied using evidences such as fossils, homologous structures and similarities in genes and biochemistry
• Mass extinction refers to the extinction of a large number of species within a relatively short period of geologic time, thought to be due to factors such as catastrophic global events or widespread environmental change that occurred too rapidly for most species to adapt. 
• Scientists have come up with a number of theories that they believe caused mass extinctions. These include catastrophic methane release, floods, basalt eruptions, climate change, and impact events.