| Hybrid Breakdown | First-generation hybrids between two species appear normal, but their offspring (second-generation hybrids) experience reduced viability, fertility, or other deleterious effects [Often in plants] |
| Hybrid Breakdown | First-generation hybrids between two species appear normal, but their offspring (second-generation hybrids) experience reduced viability, fertility, or other deleterious effects [Often in plants] |
| Hybrid Breakdown | First-generation hybrids between two species appear normal, but their offspring (second-generation hybrids) experience reduced viability, fertility, or other deleterious effects [Often in plants] |
| Hybrid Breakdown | First-generation hybrids between two species appear normal, but their offspring (second-generation hybrids) experience reduced viability, fertility, or other deleterious effects [Often in plants] |
| Divergent Evolution | Distinct species arise from a common ancestor [Humans + Apes] |
| Convergent Evolution | Two unrelated species independently evolve from respective ancestors to have similar analogous structures, performing comparable functions [Shark + Dolphin] |
| Parallel Evolution | Two species with a common ancestor evolve similar traits independent of one another [Flying squirrel + Phalanges] |
| Coevolution | Process by which two or more species evolve in tandem by exerting selective pressures on each other [bees + pollen] |
| Allopatric Speciation | Geographic isolation of populations, leading to genetic divergence and eventual reproductive incompatibility between separated groups. |
| Parapatric Speciation | New species arise when populations of a single species inhabit adjacent but distinct environments, leading to limited gene flow and the development of unique traits, ultimately resulting in reproductive isolation and the formation of separate species. |
| Sympatric Speciation | Formation of new species within the same geographical area, often driven by ecological or behavioral factors that create reproductive barriers between different groups in the population. |
| Temporal Isolation | 2 species mate at different times of the year [Frogs which live in the same pond but in different seasons] |
| Ecological Isolation | 2 species occupy different habitats [Lions and tigers can potentially interbreed but live in different habitats] |
| Behavioural Isolation | 2 species have diferent courtship behaviours [Certain birds only respond to specific mating calls] |
| Mechanical Isolation | 2 species are too physically different to mate [Some dog breeds are morphologically incapable of mating due to size] |
| Hybrid Inviability | Reduced survival or viability of hybrid offspring due to genetic incompatibilities between different species. [Horse and a donkey mating to produce a mule, which often has health issues and reduced fertility] |
| Hybrid Infertility | Hybrids fail to produce functional gametes [horse and a wild zebra, known as a "zorse," often exhibits reduced fertility or sterility] |
| Hybrid Breakdown | First-generation hybrids between two species appear normal, but their offspring (second-generation hybrids) experience reduced viability, fertility, or other deleterious effects [Often in plants] |
