8.2 Speciation

• Biological Species Concept: A population/group of populations whose members have the ability to breed with one another in nature and produce fertile offspring.
• Morphological Species Concept: Organisms are classified on their appearance (internal and external structures)

  • Easy to use, extremely helpful in communicating characteristics, behaviour and relationships of organisms.
• Hybrids: A cross between two different species that produces offspring that are a mixture of the two parent species.
• Modern Species Concept: Includes both the morphological and biological

  species concepts.

  • Important in evolution because it recognizes that individuals pass genes to the next generation
• Microevolution: Explains how populations evolve (change in allele frequencies)
• Macroevolution: Refers to more dramatic biological changes

  • Origins of different species
  • Extinction
  • Evolution of major new features (e.g. wings or flowers)
• Speciation: Origin of new species

  • Leads to an increase in diversity
• Reproductive Isolation/Barrier: The inability of two organisms to reproduce

  due to some kind of physical or behavioural barrier
• Geographic Isolation: The isolation of a population from other populations due to geographic barriers.
• Splinter” populations may result— causes change in allele frequencies
• Habitat Isolation: When organisms adapt to different niches in the same area yet cannot interbreed
• Temporal Isolation: Different breeding periods
• Behavioural Isolation: Different courtship behaviours prevent mating
• Mechanical Isolation: Incompatible reproductive structures
• Gametic Isolation: Sperm and eggs have molecular markers or proteins that are incompatible
• Hybrid Inviability: Usually dies during fetal development; typically unhealthy
• Hybrid Infertility: Hybrid can mature into adults but are infertile
• Divergent Evolution: The evolution of two or more species that have diverged from a common ancestor.
• Convergent Evolution: Distantly related species living in similar environments

  develop similar adaptations
• Rates of Speciation: Rate of Speciation is the number of new species that arise in a given time period.
• Gradualism: Gradual changes from DNA that accumulate over time
• Punctuated Equilibrium:

  • Steven J. Gould
  • Changes in fossil records can be sudden
  • Genetic Drift and natural selection can cause drastic change in just a few hundred generations
• It took billions of years for present-day

  species to evolve
• In a short period of time, humans have reduced global biodiversity.

  • Other invasive species cause major issues
  • Overhunting and poaching
  • Pollution impacting habitats and health of organisms