Evolution and Speciation Flashcards
Evolution
The change in heritable characteristics of a population over time
Allopatric VS Sympatric Speciation
Both lead to formation of new species
Both involve reproductive isolation
Geographic barrier is present
No geographic barrier
Physical barrier to separate species
Reproductive isolation occurs in same area
Caused by geographic changes, dispersal and colonization
Caused by genetic mutation, polyploidy and sexual selection
Initially high then reduced gene flow
Absent gene flow from the beginning
Selective Breeding
Process where humans intentionally choose individuals with desirable traits and breed them together to enhance those specific traits in the population
Challenges for Hybrid Species
Reduced fertility as mismatched chromosomes makes it difficult for hybrids to produce sex cells
Lower fitness as they might not be adapted to either parents’ environment
Advantage of Polyploidy in Crops
Can create instant reproductive isolation as crops won’t be able to interbreed with other parent species which creates a new species
Grow larger and show improved longevity and disease resistance
Adaptive Radiation Process
Group of organism is in new environment with abundant resources and few competitors, therefore presenting variety of unoccupied niches
Organisms exploit different resources within environment which leads to variations in group as different members are exposed to different selection pressures
This makes members evolve different morphological features in response to selective pressures
Eventually genetic differences accumulate within subgroups which prevents them from interbreeding which leads to formation of entirely new species
The new species continue to diversify by filling even more specialized niches which leads to increase of variety of life forms in the ecosystem
Darwinism VS Lamarckism
Lamarckism suggests that organisms acquire traits during their lifetime through use and disuse and pass them to offspring, while Darwinism states that variation already exists, and natural selection favors beneficial traits, leading to evolution over generations.
Homologous VS Analogous Structures
Similar structure but different function
Similar function but different structure
Share common ancestor
Don’t share common ancestor
Result of divergent evolution where related species evolve to become more different from each other usually due to different niches
Result of convergent evolution where different species develop similar structural similarities due to similar environmental conditions and adaptation to it
Evidence for Evolution from Base Sequences in DNA and Amino Acid Sequences
DNA is universal, and the same DNA codons code for the same amino acid in almost all organisms
Essential proteins show high levels of similarity in amino acid sequences across organisms
Adaptive Radiation
Common ancestor splits into multiple species to different variations and exploit different ecological niches
Autopoliploidy VS Allopolyploidy
Duplication within a single species
Duplication from two different species
Can lead to sterility or fertility
Often initially sterile but polyploidy can restore fertility
Can lead to speciation within a species
Can create entirely new species =
Abrupt Speciation
Combining of genetic material from two different species (hybridization) and doubling chromosome number )(polyploidy)
Selective Breeding Evidence for Evolution
Creates significant differences between domesticated breeds and their wild ancestors
Demonstrates how traits can change dramatically over short time scales
Often differ significantly in traits like size and behaviour
Humans select desirable traits which leads to rapid changes in populations
Implications of Speciation
Speciation increases biodiversity by increasing total number of species on Earth
Speciation can also decrease biodiversity§ as extinction can result from speciation which decreases number of species
