The History of Evolution Darwin Lamarck Cuvier

We’ll talk more about these later. Evolution Defined: the process of biological change by which descendants come to differ from their ancestors. 5 factors that lead to evolution: Genetic drift Gene flow Mutations Sexual selection Natural Selection We’ll talk more about these later.

Species lion tiger liger Species: group of organisms that can interbreed and produce fertile offspring Different species rarely breed Interspecies (between different species) 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 Problem: Traits acquired after fertilization cannot be passed to offspring Early Belief: Giraffes & Long Necks Long necks are result of stretching to reach leaves Extra length was passed on to offspring

Geologic Change Early belief: “New” Observations 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 past geologic events can be explained by phenomena and forces observable today; the classical concept that 'the present is the key to the past'

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 are another example. Finches with strong, thick beaks live in areas with a lot of large, hard shell nuts. Finches with delicate beaks live in areas where small insects and fruits are readily available.

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

Butterflies won't lay eggs on plants with fake egg spots

Can you find the geckos?

Gross....bird poop...or is it???

Causes of Genetic Variation Genetic variation increases chances some organisms 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: During meiosis, genes recombine in varying patterns

Variation: 4 Different Gametes Chromatids copied Crossing- over Crossing- Over finished Genetic variation! Four differing chromatids

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