Introduction to Natural Selection - AP Biology
- Identify a factor that can cause genetic drift.
- Random events like natural disasters. Random sampling effects that change allele frequencies regardless of fitness.
- Explain 'disruptive selection'.
- It favors extreme phenotypes over intermediate ones. Promotes genetic diversity by selecting against intermediate forms.
- Who proposed the theory of natural selection?
- Charles Darwin. English naturalist who formulated the theory in the 19th century.
- What is meant by 'variation' in a population?
- Differences in physical traits among individuals of a species. Essential for natural selection as it provides diverse traits to select from.
- What is sympatric speciation?
- Speciation that occurs without geographic separation. Reproductive isolation develops within the same geographic area.
- What is the bottleneck effect?
- A sharp reduction in population size due to environmental events. Randomly eliminates genetic variants, reducing overall diversity.
- What is sexual selection?
- Selection based on traits that improve mating success. Favors traits that enhance reproductive success rather than survival.
- What is natural selection?
- A process where organisms better adapted to their environment tend to survive and reproduce. The driving mechanism of evolution where favorable traits increase survival rates.
- What results from natural selection over many generations?
- Evolution of species. Gradual change in species characteristics through accumulated adaptations.
- What is an evolutionary arms race?
- A cycle of adaptations and counter-adaptations between competing species. Continuous reciprocal adaptations between interacting species.
- Identify the four main principles of natural selection.
- Variation, inheritance, high rate of population growth, differential survival and reproduction. These conditions must exist for natural selection to operate effectively.
- What is gene flow?
- Transfer of genetic variation from one population to another. Migration between populations homogenizes genetic differences.
- How does mutation contribute to evolution?
- It introduces new genetic variations. Creates novel alleles that provide raw material for selection.
- Describe 'stabilizing selection'.
- It favors average phenotypes and reduces variation. Maintains population stability by eliminating extreme variants.
- Describe the founder effect.
- Loss of genetic variation when a new colony is established by a few individuals. Small founding populations carry limited genetic representation.
- Identify an example of a physiological adaptation.
- Camels storing fat in their humps for energy. Internal body function that enhances survival in harsh desert conditions.
- What is a selective advantage?
- A characteristic that improves an organism's chances of survival. Confers higher fitness compared to alternative trait variants.
- How does artificial selection differ from natural selection?
- Artificial selection is human-directed; natural selection is environment-driven. The agent of selection differs between natural and human-controlled processes.
- What is directional selection?
- Selection that favors one extreme phenotype over others. Shifts population characteristics toward one end of the trait spectrum.
- What is speciation?
- The formation of new and distinct species in the course of evolution. Reproductive isolation leads to divergent evolutionary pathways.
- What is artificial selection?
- Selective breeding by humans to enhance desired traits in organisms. Human intervention replaces natural environmental selection pressures.
- Identify a consequence of reduced genetic diversity.
- Increased vulnerability to diseases. Limited genetic variation reduces adaptive potential and disease resistance.
- How does the environment influence natural selection?
- It determines which traits are advantageous for survival. Environmental factors create selection pressures that favor certain traits.
- How does natural selection affect allele frequencies?
- It can increase or decrease allele frequencies based on fitness. Beneficial alleles increase while harmful alleles decrease in frequency.
- What is a species?
- A group of organisms that can interbreed and produce fertile offspring. Reproductive compatibility defines the boundaries of species classification.
- What is an adaptation?
- A trait that improves an organism's ability to survive and reproduce. Results from natural selection favoring beneficial characteristics.
- Identify an example of sexual selection.
- Peacock's tail feathers attracting mates. Ornamental display that signals genetic quality to potential mates.
- What role does 'inheritance' play in natural selection?
- Traits must be heritable for natural selection to act upon them. Only heritable traits can be passed to offspring and accumulate over generations.
- Identify a selection pressure in an environment.
- Predation, competition, climate change. Environmental factors that influence which traits are advantageous.
- Define 'fitness' in an evolutionary context.
- The ability of an organism to survive and reproduce in its environment. Measured by reproductive success and adaptation to environmental pressures.
- What is a behavioral adaptation?
- An action or behavior that helps an organism survive in its environment. Learned or instinctive responses that increase survival chances.
- What is a niche in ecological terms?
- The role and position a species has in its environment. Defines how an organism interacts with its physical and biological environment.
- Describe allopatric speciation.
- Speciation that occurs due to geographic isolation. Physical barriers prevent gene flow between diverging populations.
- Explain the term 'survival of the fittest'.
- Organisms best adapted to their environment survive and reproduce. Refers to reproductive fitness, not physical strength or dominance.
- How do adaptations arise in a population?
- Through mutations and natural selection over time. Mutations provide variation, selection determines which variants persist.
- Why is overproduction of offspring important for natural selection?
- It leads to competition, ensuring only the fittest survive. Creates resource scarcity that intensifies selection pressure.
- Give an example of a structural adaptation.
- The long neck of a giraffe for reaching high leaves. Physical modification that enhances feeding efficiency and survival.
- What does 'differential survival' mean?
- Some organisms are more likely to survive and reproduce than others. Creates unequal reproductive success based on trait advantages.
- What is the significance of genetic variation in a population?
- It provides the raw material for natural selection to act upon. Without variation, all individuals would respond identically to selection pressures.