Overview
This lecture covers key terms from Chapter 18 of Biology 2e, focusing on evolution, speciation, and mechanisms of reproductive isolation.
Evolution and Speciation Concepts
- Adaptation is a heritable trait or behavior helping survival and reproduction in a specific environment.
- Adaptive radiation describes one species splitting to form several new species.
- Allopatric speciation occurs when new species arise due to geographic separation.
- Sympatric speciation is when new species form in the same geographic area.
- Speciation is the formation of a new species.
- Divergent evolution refers to groups evolving in different directions from a common ancestor.
- Convergent evolution is when unrelated groups independently evolve similar traits.
- Natural selection is the process where individuals with favorable traits survive and reproduce, leading to evolutionary change.
Mechanisms of Reproductive Isolation
- Reproductive isolation means a species is reproductively independent due to behavior, location, or barriers.
- Prezygotic barriers prevent fertilization before zygote formation (e.g., behavioral, habitat, temporal isolation, gametic barriers).
- Postzygotic barriers occur after zygote formation (e.g., low hybrid viability).
- Behavioral isolation prevents reproduction due to specific behaviors or their absence.
- Habitat isolation arises when populations live in different habitats.
- Temporal isolation involves differences in breeding times.
- Gametic barriers occur when egg and sperm cells are incompatible.
Models and Patterns in Speciation
- Gradual speciation model shows species split slowly over time in small steps.
- Punctuated equilibrium describes rapid speciation after a population becomes isolated.
- Reinforcement is continued divergence due to low fitness of hybrids.
- Dispersal is allopatric speciation when a few individuals relocate to a new area.
- Vicariance is allopatric speciation where an environmental change divides a population.
Other Important Terms
- Allopolyploid results from combining chromosomes of two different species.
- Autopolyploid arises from chromosome duplication within one species.
- Aneuploidy is the presence of extra or missing chromosomes.
- Hybrid refers to offspring from two closely related individuals, not the same species.
- Hybrid zone is an area where two related species interact and form hybrids.
- Variation means genetic differences within a population.
- Homologous structures are similar structures with a common ancestor.
- Vestigial structures are present but nonfunctional traits from ancestors.
- Species are groups that can interbreed and produce fertile offspring.
Key Terms & Definitions
- Adaptation — inheritable trait aiding survival and reproduction.
- Adaptive radiation — one species splits into several new ones.
- Allopatric speciation — new species form via geographic separation.
- Sympatric speciation — new species form in the same area.
- Speciation — process of forming a new species.
- Reproductive isolation — mechanisms preventing interbreeding.
- Prezygotic barrier — isolation before zygote formation.
- Postzygotic barrier — isolation after zygote formation.
- Gradual speciation model — slow, stepwise divergence.
- Punctuated equilibrium — rapid speciation after isolation.
- Hybrid — offspring of two different species.
- Variation — genetic diversity within populations.
- Homologous structures — traits with shared ancestry.
- Vestigial structure — nonfunctional trait from ancestors.
Action Items / Next Steps
- Review these key terms for understanding of evolution and speciation.
- Prepare for next lecture by reading the Chapter 18 summary.