Variation in Populations�AP Topic 7.11

• Learning Objectives
• Explain how the genetic diversity of a species or population affects its ability to withstand environmental pressures.

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AP BIOLOGY

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Importance of �Genetic Diversity

• genetic diversity leads to environmental resistance
• affects how populations respond to environmental changes and pressures
• high genetic diversity → greater adaptability & survival chances
• low genetic diversity → increased risk of decline or extinction.

7 Natural Selection & Evolution

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AP BIOLOGY

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Population Dynamics �& Genetic Variation

• Populations with more genetic variation
• have a higher chance of individuals with favorable traits
• can adapt to changing environmental conditions
• e.g., temperature, disease, predators

7 Natural Selection & Evolution

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AP BIOLOGY

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Population Dynamics �& Genetic Variation

• Populations with low genetic variation:
• less adaptable, higher chance of collapse when faced with change
• more vulnerable to genetic bottlenecks and inbreeding depression

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AP BIOLOGY

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Case Study �High Genetic Diversity

• African Cichlids – Diverse colors and feeding strategies allow adaptation to different ecological niches

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AP BIOLOGY

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Low Genetic �Diversity Example

• Cheetahs – Limited genetic variation makes them highly susceptible to disease and environmental changes

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AP BIOLOGY

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Adaptive vs. Deleterious �Alleles in Different Environments

• Alleles that help in one environment may be harmful in another due to selective pressures
• Selective pressures determine whether an allele is adaptive or deleterious

7 Natural Selection & Evolution

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AP BIOLOGY

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Sickle Cell Trait�

• Heterozygote Advantage
• Provides resistance to malaria
• Homozygous Recessive
• Causes sickle cell disease, which is harmful

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AP BIOLOGY

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Rock Pocket Mice

• Dark fur is beneficial on lava rock
• Makes mice more visible on desert sand

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AP BIOLOGY

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Summary�(Topic 7.12)

• Why Genetic Diversity Matters
• Genetic diversity = Population survival & adaptability
• High diversity → More resilience to change
• Low diversity → Higher risk of extinction
• Environmental pressures shape allele frequency over time
• Adaptive traits in one environment may be disadvantageous in another

7 Natural Selection & Evolution

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AP BIOLOGY

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