The History of Evolution Darwin Lamarck Cuvier
lion Species • Species: group of organisms that can interbreed and produce fertile offspring • Different species rarely breed • Interspecies breeding often results in sterile offspring • Ex: Horse x Donkey = Mule • Ex: Lion x Tiger = Liger tiger liger
horse donkey mule
Jean Baptiste de Lamarck • Acquired Inheritance: Early theory where organisms could acquire and pass traits after birth • Cause: environmental changes forced individuals to change • Early Belief: Giraffes & Long Necks • Long necks are result of stretching to reach leaves • Extra length was passed on to offspring • Problem: Traits acquired after fertilization cannot be passed to offspring PROVEN WRONG!
Geologic Change • Early belief: • Earth ~6,000 years old • Life remained unchanged • “New” Observations • Rock layers (strata) contained differing fossils • Deeper fossils (older) less complex • Environmental changes thought to affect life characteristics
Charles Darwin • Observed: • Organisms have variations based upon environment • Similarities between extinct fossils & modern life • Marine fossils atop mountains • Natural Selection: Process where organisms with favorable traits survive and reproduce • Major concept in biology published in The Origin of Species (1859)
Variation: Inherited traits that make an individual different from others Green, flat wings of the insect above Adaptation: Variation increases the chance of survival Ability to blend with environment Adaptation & Variation
Butterflies won't lay eggs on plants with fake egg spots
Can you find the geckos?
Causes of Genetic Variation • Genetic variation increases chances some survive in changing environments • Gene Pool: All alleles within a population • Two main causes of genetic variation: 1) Mutations: Random genetic changes may affect phenotypes 2) Recombination(crossing over): During meiosis, genes recombine in varying patterns
Variation: 4 Different Gametes Chromatids copied Crossing- over Crossing- Over finished Genetic variation! Four differing chromatids
Review • When are two organisms considered a different species? • Even though incorrect, why is Lamarck’s theory still relevant? • How can the general age of rocks (and fossils) be determined? • How does a variation and adaptation differ? • What is natural selection?
Quick Review • Features of a species can evolve, or change over time • Natural selection is when favorable traits allow survival & reproduction • Variations allow an organism to be better suited to its environment