TwoOldGuys Study Guides
BI-125 Botany
Evolution, Micro-evolution and Macro-evolution
Micro-evolution
Mutation
- genome is collection of DNA sequences that code for traits
- DNA can be altered by ionization
ionizing radiation (such as UV),
chemically induced,
random error
- nucleotide removed from deoxyribose backbone
- if DNA is double helix, repair is possible
by base-pairing during repair
- when DNA is single stranded, repair may be quasi-random
resulting in incorrect sequence, and potentially erroneous code
- erroneous code may produce 'defective proteins'
- frequently confers disadvantage,
and mutation is removed from population by natural selection
- when mutation confers advantage
natural selection will reduce numbers of 'wild-type' phenotype
- description of species may therefore change over time
although species remains same species
- there are numerous documented examples of micro-evolution
Macro-evolution
- refers to the process by which mutation can produce new species
- Darwinian thinking suggested that accumulation of modified traits over time
would lead to the production of species
- current thinking suggests that there must be a isolating mechanism
for a sub-population of one species can become a new species
- reproductive isolation
- geographic barriers
- ecological barriers
- temporal barriers
- mechanical barriers
- In plants:
- hybridization
- autopolyploidy
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