Species Species group of organisms that can interbreed

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

N O N E ! G R W • 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 P V O R • Problem: Traits acquired after fertilization cannot be passed to offspring

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)

• Finches

Adaptation & Variation • 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

Causes of Genetic Variation • Genetic variation increases chances some survive 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 Crossingover Crossing. Over finished Genetic variation! Four differing chromatids

Review 1) 2) 3) 4) 5) 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?

• 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