Selection Pressures Shaping Life Around Us
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Selection Pressures Shaping Life Around Us
Understanding how environmental forces drive evolutionary change Real-world examples from Australian ecosystems Year 11 Biology - NSW Curriculum
What Are Selection Pressures?
Environmental factors that influence survival and reproduction Include predation, climate, disease, competition for resources Drive changes in allele frequencies over time Result in adaptations that increase fitness
Case Study 1: The Peppered Moth
Analyze the Moth Data
In groups of 6, examine the peppered moth frequency data Identify the selection pressure acting on the population Explain why dark moths became more common Predict what happened after pollution controls were introduced
Case Study 2: Cane Toads in Australia
Introduced in 1935 to control cane beetles Rapidly spread due to lack of natural predators Toxic to native predators - strong selection pressure Native species evolving shorter legs, smaller mouths
Cane Toad Impact Analysis
{"left":"Advantages for cane toads: No natural predators, Abundant food sources, Suitable climate, High reproductive rate","right":"Effects on native species: Poisoning of predators, Competition for food, Habitat disruption, Evolutionary pressure to adapt"}
Case Study 3: Prickly Pear Control
Prickly pear invaded 25 million hectares by 1920 No natural enemies - population exploded Cactoblastis moth introduced as biological control New selection pressure reduced prickly pear by 99%
Synthesis Question
How do these three case studies demonstrate that selection pressures can drive rapid evolutionary change? What role do humans play in creating new selection pressures? Why is understanding selection pressures important for conservation?