Patterns of Evolution
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Homology, embryology, fossil record, phylogeny
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Patterns of Evolution
- 1. Life Science Patterns of Evolution Changes Over Time
- 2. In your lab notebook, please answer as best you can: Week 13 Review Quiz Bonus: What is the geologic column? - a sequence of rock layers that combines all the known fossils and rock formations on Earth arranged from oldest to youngest 1. Name two factors that increase an organism’s chance of fossilization. • Hard parts (shell/bone), quick burial (slows decomposition), location of death (dry/cold vs. harsh or warm/wet) 1. When all members of a certain species die, they are said to be… • Extinct 1. Are fossil molds & casts found in ice, tar, sedimentary rock, or amber? • Rock 1. An opinion that prevents the objective analysis of a set of facts is a… • Bias 1. What is dendrochronology? • Tree-ring dating (the technique of dating rock layers and fossils by cross- dating the patterns of annual growth rings in tree trunks)
- 3. What is Evolution? • Simple: "change over time“ • Biological Evolution: "descent with modification" – many, many, MANY small changes over LOOOOOOOOONG periods of time that result in the formation of many DIFFERENT types of organisms
- 4. Types of Evolution • Microevolution – Small changes within a species' set of genes that result in phenotypic differences – Decades or centuries (short time) – Under certain environmental conditions, can produce new, closely-related species • Macroevolution – descent with modification – the process by which modern organisms have descended from ancient ancestors due to many small changes over millions of years (long time)
- 5. Speciation • A lineage-splitting event that produces a new, separate species is called speciation – reproduced in lab experiments – populations change so much that they no longer can interbreed and exchange genes – requires geographic isolation • Macroevolution = speciation on a grand scale • Individuals DO NOT evolve over time, but POPULATIONS do!
- 6. Week 13 Lab Paper Airplane AdaptationsObservation -A mutation is a change in the nucleotide base sequence of a gene (in a cell’s DNA) that results in the manufacture of altered proteins which determine an inherited trait. -Mutations are rarely beneficial and only passed to offspring if they occur in germ cells or gametes. -Adaptations are traits caused by mutations that increase an organism’s or population’s survival and/or ability to reproduce. -Evolutionary fitness describes a population’s ability to survive and reproduce in its current environment. -Natural selection describes how a more fit population may be “chosen” by their environment to survive. (This is really an awkward way of saying that a less fit population that lacks adaptations will probably not survive or pass on their genes.) -Biological evolution occurs over long periods of time within populations of living things due to differences in the frequency and combination of genes that determine or influence inherited traits.
- 7. Paper Airplane Adaptations - For this activity, paper airplanes will represent organisms of the same species. Paper clips will represent food, which the organisms will be competing for by trying to reach the box. Certain airplane designs may provide an advantage for the “organism” to reach the food sooner and stay alive. If your airplane is the last to reach the box in the center of the circle, your organism will die and you will have to sit out for the rest of the game!
- 8. The Geologic Column • Assembled from different strata from around the world with a bias towards evolution • Assumes sedimentation occurs evenly and slowly over millions of years “the present is key to the past” • Large gaps remain in the fossil record – they may be still hidden, have been destroyed, or never existed • Out of place fossils & lack of transitional fossils is puzzling
- 9. The "Cambrian Explosion" • Evidence in the fossil record shows that all major phylla were established in the transition from Late Precambiran to Early Cambrian time • In the creationist model, these animals represent descendants of original created kinds that became extinct during the Flood of Genesis. • Gradual evolution struggles to account for the sudden appearance of so many types of life at one time. – "Punctuated Equilibrium" is one solution • It is puzzling why there are little to no "precursor" fossils to all these varieties of life.
- 11. Homologous Features • A structure found in different species, but derived from a common ancestral structure. – The structure may or may not be used for the same function in the species in which it occurs. Examples: • skeletal structure of vertebrate limbs • embryonic similarities • similarities in DNA, RNA, & the proteins the code for
- 12. Embryologic Development • Structures that have different mature forms but develop from the same embryonic tissues • Limbs are structurally similar but have different functions • Recent developments in biochemistry show "similarity does not imply a genetic relationship" Alligator Turtle Primitive Fish Mammal
- 16. Inherited Traits • Neo-Darwinism sites the similarities of genetics between species as evidence of evolution • Other scientists look DNA and see the complexity and efficiency of information transfer as evidence for a single, intelligent “designer”
- 17. Phylogeny • The evolutionary history of a species • Relationship to other species is based on : – Fossil record – Morphology (similar physical structures) – Embryological patterns of development – Genetic similarities (DNA)
- 18. Cladograms • A cladogram is based on sorting similar organisms into groups called clades that prioritize evolutionary relationships (phylogeny) over traditional shared characteristics (Linnaean classification) • Cladistics is a relatively new system of grouping that identifies similar derived characteristics to represent evolutionary relationships. • Organisms on the same “branch” descended from a common ancestor • The branching pattern identifies speciation events (splits in two where changes occur) • Relies most heavily on genetic similarities (DNA)
- 19. Six Kingdoms • Archaebacteria • Eubacteria • Protists • Fungi • Plants • Animals • This phylogenetic tree is VERY simplified! • First true cells are thought to have arisen from aquatic, anaerobic, "protocells" 6 EUBACTERIA ARCHAEBACTERIA
Editor's Notes
- RBC’s lack mitochondria and nuclei – they use glycolysis to produce ATP and only live about 3 months before being replaced. Microorganisms that can live without oxygen, such as the lactobacilli that turn milk products into yogurt and cheese, use fermentation to generate ATP.
- Because the fossil record show abrupt appearance and “stasis” (no change), the evolutionary theory of “punctuated equilibrium” was developed by Gould and Eldredge, which basically says we don’t see evolution in the fossil record because it happens fast in small isolated groups. It is an argument from lack of evidence. The Cambrian Explosion makes a shipwreck of their nice neat chart. Rather than seeing simple life forms such as worms and jellyfish appear to be folowed by trilobites and fish and the like, we instead see representations of all major phyla appearing AT THE SAME TIME! This obvious slap in darwin’s face has caused not a few Darwinists to famously modify the theory. Punctuated equilibrium, or “punk eek,” suggests that life exists with only minor adaptations within established kinds [observable microevolution, which no one disputes], but then goes rapid changes in short spurts which leave behind no transitional forms!
- Could be evidence for descent with modification Could be evidence for a single intelligent “creator”
- Do similar embryological forms show common ancestry or a common designer? Ludwig Rutimeyer, a professor of zoology and comparative anatomy, at the University of Basel, reviewed Haeckel's work and Haeckel's mistakes were brought to the attention of the professors at Jena (Rutimeyer 1868). Charged with fraud by five professors and convicted by a university court at Jena, he agreed that a small percentage of his embryonic drawings were forgeries. Haeckel alleged he was merely filling in and reconstructing the missing links when the evidence was thin. During the trial, Haeckel confessed that he had altered his drawings, but excused himself by saying: “I should feel utterly condemned and annihilated by the admission, were it not that hundreds of the best observers and biologists lie under the same charge. The great majority of all morphological, anatomical, histological, and embryological diagrams are not true to nature, but are more or less doctored, schematized and reconstructed”.
- Case Study: Developmental Homologies In 1868, a scientist named Ernst Haeckel published drawings of early vertebrate embryos which he manipulated to look more similar than they actually were. This was because he held preconceived views about evolution. Haeckel’s drawings were eventually recognized as fraudulent, but they are still found in some biology textbooks as good evidence for common ancestry. Haeckel’s ideas continue to spread misconceptions today. In humans at one month, there are throat pouches in the skin near the neck. These are sometimes labeled as ‘gillslits’, suggestive of a fish ancestry. In fish, these pouches do develop into gills. But in humans and other organisms, the middle ear canals develop from the second pouch, and the parathyroid and thymus glands come from the third and fourth. These labels are therefore quite biased. Other common misconceptions include the idea that a human embryo has a ‘yolk sac’ like a chicken and a ‘tail’ like a primate. These parts have now been identified as the blood-forming sac and the coccyx: an important point of muscle attachment necessary for our upright posture.
- Darwin didn’t know about DNA – it hadn’t been discovered yet. Most people of his time believed that things you learned and experienced during your lifetime could be inherited by your offspring. Darwin believed there had to be a system to pass down physical traits and he was right. Since Watson & Crick discovered how nucleic acids transfer genetic material in 1953, a whole new field of genetics has exploded in the realm of science.
- Before 1970, taxonomists classified all forms of life into two kingdoms: Animalia and Plantae. Bacteria, fungi, and photosynthetic protists were considered plants, and the protozoa were classified as animals. In 1969, Robort H. Whittaker proposed a five-kingdom classification scheme that is widely used today, and which we follow in this text. Whittaker identified two kingdoms of primarily unicellular microorganisms based on whether they showed prokaryotic or eukaryotic cellular organization. The kingdom Monera consists of generally single prokaryotic cells, whereas the kingdom Protista consists of generally single eukaryotic cells. All of the organisms in the remaining three kingdoms (Plantae, Fungi and Animalia) are eukaryotic, and most of them are multicellular. They may be classified further on the basis of their way of acquiring nutrients. Members of the kingdom Plantae photosynthesize, and members of the kingdom Fungi secrete enzymes outside their bodies and then absorb the externally digested nutrients. In contrast, members of the kingdom Animalia ingest their food and then digest it, either within an internal cavity or within individual cells. Recently, a sixth kingdom has been proposed. Many microbiologists argue that the cell structure of the Archaea is so different from that of prokaryotic and eukaryotic cells that they should occupy their own kingdom. Following the fashion, this text adopts the updated six-kingdom classification system (Fig. 1.1). 6 Kingdom Classification System Kingdom Eubacteria: true bacteria (formerly in kingdom monera) Kingdom Archebacteria: extremophiles (formerly in kingdom monera) Kingdom Protista (same)