Evolution Integrated Science

Evolution All the changes that have formed life on earth from its earliest beginnings to the diversity that characterizes it today. Changes in the gene pool of a population over time or descent with modification. The study of genetics helps us to understand how changes in genotypes and phenotypes come about. These changes lead to variation within a population causing them to evolve.

Evolution The Theory of Evolution states that species change over time. The primary mechanism is natural selection.

Evidence Fossil Remains Similarities in morphology (development) Biochemical: DNA, RNA, & Protein sequences Comparative Anatomy Modern Organisms Biodiversity

Determining Age on the Geologic Time Scale Relative Age - The age of a rock or an event as compared with some other rock or event. Based on the Geologic Time Scale Law of Superposition - in any sequence of layered rocks, a given bed must be older than any bed on top of it.

Determining Age on the Geologic Time Scale Absolute Age – The approximate age of a geologic event, feature, fossil, or rock in years. 'Absolute' ages are determined by using natural radioactive 'clocks'. Radiometric dating – a method used to determine the age of rocks and fossils by studying the rate of decay of radioactive isotopes. Half-life – the number of years it takes for 50%(half) of the original sample to decay (I.e., C14 has a half-life of 5730 years) Half-life is not affected by temperature, pressure, or other environmental variables

Half-Life: the Time it Takes for Half of the Original Atoms in a Sample to Decay to a "Daughter" Product The daughter product may also be radioactive, and may decay into another product. Parent Daughter Half Change in... Carbon-14 Nitrogen-14 5730 years Uranium-235 Lead-207 704 million years Uranium-238 Lead-206 4.5 billion years Barium -139 Lanthanum-139 86 minutes Radium-226 Radon-222 1600 years Radon -222 Polonium-218 3.82 days

Parent Daughter Half-Life Carbon-14 Nitrogen-14 5730 years

COMPARISON OF EVOLUTION MECHANISMS: SUMMARY Lamarck's Hypothesis: The Inheritance of Acquired Characteristics 1. A changing environment creates a need for certain features to be developed in order to survive.* 2. "Acquired Characteristics": Through use and/or non-use, those features needed for survival are developed in each individual. 3. Inheritance: Those characteristics developed ("acquired") by individuals are somehow passed on to their offspring, who can continue that development... 4. New Species: Eventually, over many generations, enough differences have developed that we can say we have a new species.

COMPARISON OF EVOLUTION MECHANISMS: SUMMARY Darwin's Hypothesis: Natural Selection 1. Overproduction: More offspring produced than will ultimately survive and reproduce 2. Variation: Inheritable features vary from individual to individual. 3. Change in environment: Changes in climate, topography, food supply, predators, etc. 4. "Struggle for existence": Mainly competition within the species, for food, habitat, survival from being eaten

COMPARISON OF EVOLUTION MECHANISMS: SUMMARY 5. "Survival of the fit" (not necessarily the strongest): Those with more adaptive traits tend to survive longer and/or produce the most offspring; these are the “naturally selected”. 6. Inheritance of "selected" features: Traits involved are already inheritable, but may involve new combinations. 7. New Species, better adapted to the new environment: When the collective traits of the population differ significantly from the earlier population, and can no longer reproduce with the earlier population

COMMON MISCONCEPTIONS TO AVOID 1. Only groups of organisms can evolve (populations or species); individuals never evolve. 2. Adaptations, in the evolutionary sense, as properly used in class and text, can only "develop" as characteristics of a species, generally over a long period of time, involving many generations; these must not be confused with the "adjustments" an individual might make, consciously or otherwise, enabling it to survive better (such as "developing resistance to a disease" or "adapting to higher altitudes", etc.