evolution bio
evolution
the cumulative change in heritable characteristics of a population.
cumulative change
small changes upon small changes over many generations
heritable characteristics
gene-controlled factors
evidence for evolution
cell division involves creating two cells from one, the goal is to pass down genetic information as well as organelles to the next generation.
Lamarck theory
proposed that species changed as a result of habitual use or disuse of a feature. Excessive use would cause a feature to develop, while continued disuse would cause it to atrophy. Lamarck proposed that these modified features could be passed on to successive generations, changing the species over time. The theory was essentially flawed (cutting the tail off a rat does not produce tailless offspring)
Charles darwin theory
based on a combination of lamarckian ideas and recent fossil discoveries. Theorized that species living today had been changed over time and stemmed from a single (or few) ancestral organisms. Noted that although populations have the capacity to grow uncontrollaly, limiting natural factors will restrict this growth. Organisms which possess traits better suited to conditions would have an adaptive advantage and be more likely to produce, making the trait more common (decent modification or natural selection)
survival of the fittest
proposed by alfred wallace, it is not necessarily the strongest or the most intelligent that survives, but the ones most responsive to change
neo-darwinism
Darwin knew very little about the mechanisms of variation or the biological basis for inheritence. This is the synthesis of darwinian theory and modern genetics (gregor mendel and watson theories)
DNA, RNA, and amino acid sequence - evolution
expect change in genes whenever evolution occurs. These changes happen in the base sequence of DNA or RNA and in the amino acid sequences of proteins made using those base sequences. Evidence for evolution also comes from comparing base sequences of the same gene in different species. The more closely related two species are, in their morphology and other traits, the fewer differences in the base sequence there are
example of evolution in dna, rna and amino acid sequence
the evolution of COVID - many base sequence changes occured in the genes of COVID, affecting the viral traits, causing new variants. Some variants were more successful than earlier ones in spreading through the human population, and so the virus evolved
Phylogenetic tree
shows speciation splits between a certain species and other ones over time
cladograms
based on sequence differences and often match closely with classifications based on morphology and the likely sequence of splits between lineages
example of evidence of evolution from gene families
Hox gene family occurs widely in animal genomes. Genes in this family help to determine the body plan during development. Similarities between hox genes can be explained by common ancestry, with duplication to give multiple copies of the gene and gradual modification for different functions in different lineages. They occur in all animals with a clear head to tail axis, which form a clade known as bilateria
Selective breeding
Selective breeding (also called artificial selection) is the process by which humans breed animals and plants for particular trait. By breeding members of a species with a desired trait, the trait's frequency becomes more common in successive generations, provides evidence of evolution as targeted breeds show significant variation over a short period. E.g domesticated animals, crops, livestock