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Lecture 7

BIOL215 Lecture 7 Notes.pdf

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Biology (Sci)
BIOL 215
Neil Price

BIOL215 Lecture 7 Notes What caused the Cambrian Explosion as discussed in class: • Abundant mutations • Radiation • Climax change • Breakup of land masses, though the time period is still too early A Cambrian "Explosion?": • How did so many body plans arise and why have so few, if any, arisen since the Early Cambrian? There were only 35 animal phyla in the body plan Adaptive radiation? Maybe there were too highly specialized • • too specialized upon appearance in the fossil record to have originated in the Cambrian Explosion: origin and radiation occur together • Geological conditions (Snowball theory) • Rising oxygen levels Predator-prey relationships • Molecular Clock: origin first, radiation later • Large body size • Acquired skeletons - availability of Ca3O • Consider how accurate the fossils are Radiation facilitated by: • Highly conserved developmental genes Of 1.2 billion (fossils - 500 million) years of animal evolution, modern humans have been on the planet only 200,000 years Scientists discovered the genes that control development and that these genes are highly conserved across all animals. It turns out that the genes found in fruit flies are shared across all animals An example is PAX6 which is the gene that code for eye development. However, as we see with flies, humans, and frogs, we all have different eyes, as such, we know that PAX6 eyeless gene is highly conserved but will evolve independently Developmental change and evolution: • Gene regulation has emerged as a central mechanism explaining developmental and evolutionary change • Jacob referred to evolution as bricolage (tinkering), a term that rightly places the emphasis on modification of existing genes. You don't change the physical structure of the gene but rather the regulatory region of the gene to affect the turning on or off of the gene • Without changing the physical structure of the gene, you can start changing where the gene gets turned on and off Understand homeobox genes and see Figure 12A/B/C to understand expression of Hox genes Plants, fungi and animals are the three kingdoms of multicellular organismLand plants are known to have evolved from organisms similar to some living g
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