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Macroevolution. Website: http://evolution.berkeley.edu/. Through descent with modification over 3.8 billion years all organisms are genetically related. Systematists are the detectives of life’s history. Evidence: Observable characters need to be derived (unique to some)
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Macroevolution Website: http://evolution.berkeley.edu/
Through descent with modification over 3.8 billion years all organisms are genetically related
Systematists are the detectives of life’s history Evidence: Observable characters need to be derived (unique to some) and shared (common ancestor) Such characters are called synapomorphies Result: Produce a tree-like diagram Called phylogeny or cladogram To distinguish a particular clade of mammals within the larger clade that corresponds to class Mammalia, would hair be a useful character? Why or why not? How do scientists reconstruct these relationships?
Phylogenies are evolutionary trees Which of the following is most closely related to the lizard and snake group? a. mammals b. lungfish c. birds d. Amphibians Snakes are tetrapods that don't have legs. What could explain that? a. Snakes are more closely related to fish than lizards. b. Snakes are not reptiles. c. No ancestors of snakes had tetrapod limbs. d. An ancestor of snakes had tetrapod limbs.
Which branch point represents the most recent common ancestor of all bears? ___________ Which branch point represents the most recent common ancestor of the sloth bear and the spectacled bear? ________ Identify the sister taxon to the polar bear. _____________ According to this tree, is the sun bear more closely related to the sloth bear or the polar bear? _____________
Tree thinking challenges; question 1 Complete number 5
Part 3. Trees Place the species (outgroup, A, B, and D) on the following phylogenetic tree based on the presence or absence of the characters 1 thru 4 in the table. Indicate before each branch point the number for the shared derived character that evolved in the ancestor of the clade.
Importance of reconstructing evolutionary histories We can observe large scale patterns through out life’s history
Macroevolution patterns 99% of species that have existed are extinct today Extinction: is the disappearance of an entire species from the face of the Earth Mass extinctions: events that have wiped out anywhere from 50% to 95% species Adaptive Radiation : event in which a group of species rapidly diversifies
Macroevolution Patterns Convergent evolution: Unrelated species develop similarities due to adaptation to similar environments These similarities are called… Analogous characters similar looking structures due to adaptation to similar environments not due to common ancestry Analogous characters are a result of convergent evolution Homologous characters characters in different organisms that are similar because they were inherited from a common ancestor that also had that character
Types of characters Decide whether each of the following pairs of structures more likely represents analogy or homology, and explain your reasoning: 1. a porcupine’s quills and a cactus’s spines: ___________ 2. a cat’s paw and a human’s hand: ___________________ 3. an owl’s wing and a hornet’s wing: __________________
4. The term convergent evolution is most applicable to which of the following features? A. the five-digit condition of human hands and bat wings B. the legless condition found in various lineages of extant lizards C. the bones of bat forelimbs and the bones of bird forelimbs D. the fur that covers Australian moles and North American moles
5. Animals that possess homologous structures probably _____. a. are the result of similar environmental pressures in different evolutionary lineages b. have increased genetic diversity c. are the result of convergent evolution d. evolved from the same ancestor e. are not related
Macroevolution patterns Evolution is not goal oriented Vestigial structures: structures that are of little or no value to the organism, are historical remnants of ancestral structures
6. Over long periods of time, many cave-dwelling organisms have lost their eyes. Tapeworms have lost their digestive systems. Whales have lost their hind limbs. How can natural selection account for these losses? A. The ancestors of these organisms experienced harmful mutations that forced them to lose these structures. B. Under particular circumstances that persisted for long periods, each of these structures presented greater costs than benefits. C. Natural selection cannot account for losses, but accounts only for new structures and functions. D. Natural selection accounts for these losses by the principle of use and disuse.
Macroevolution patterns Evolution is not goal oriented Exaptation: existing structures that evolved and functioned in one setting and were then co-opted for a new function
Importance of reconstructing evolutionary histories We can organize species based on their evolutionary relationships Using phylogenies as a basis for classification is a relatively new development in biology.
This phylogenetic classification system names only monophyletic clades (groups of organisms that are ALL descended from a common ancestor)
7. In a comparison of birds and mammals, having four limbs is A. a character useful for sorting bird species. B. a character useful for distinguishing birds from mammals. C. a shared derived character. D. a shared ancestral character. E. an example of analogy rather than homology.
8. Many crustaceans (for example, lobsters, shrimp, and crayfish) use their tails to swim, but crabs have reduced tails that curl under their shells and are not used in swimming. This is an example of _____. A. a vestigial trait B. natural selection C. a homologous structure D. convergent evolution
Trees matter Venom evolution widespread in fishes: a phylogenetic road map for the bioprospecting of piscine venoms. Drug discovery Tracking a disease to its source
One of the strengths of a theory is that it can be tested using independent lines of evidence Descent with modification as a theory
Comparative anatomy • If descent with modification is correct, then two species that are related to each other should have ________________________ • Right down the answer from the animation
Comparative anatomy 3. Based on the phylogeny constructed using hemoglobin gene sequence, Who is more closely related to ceteceans? Who is more closely related to seals and walruses? 4.Pakicetus (early cetacean) ankle Bone is more similar to a dogs or A pigs?
Fossil record provides snapshots of the past 5. What are the conditions for an organism to get fossilized? 6. If new sediments get accumulated on top of old ones, where do you expect to find older fossils? 7. Do gaps on the fossil record disprove evolution?
Fossil record supports descent with modification 8. If descent with modification is correct, then fossils should show ____________________ Species of whale fossils: Dorudon 36 mya Pakicetus 50 mya Aetiocetus 30 mya Balaenoptera (blue whale) today 9. What is the correlation between the dates of when these species lived and the location of the nostrils?
Transitional forms: Fossils or organisms that show the intermediate states between an ancestral form and that of its descendants 10. This evolutionary tree shows The transitional forms for what?
Geographical distribution of organisms on the earth supports descent with modification 11. If one species descended from another, then their distributions should far apart or close together? ______________________ 12. Answer the question from the video _________________
Look who lives in America and is a marsupial? Marsupial mammals are found in the Americas as well as Australia They are not found swimming across the Pacific Ocean, nor have they been discovered wandering the Asia. How could marsupials have gotten from one place to a location half a world away?
Plate tectonics causes Continental drift Continents have been and are constantly on the move Continental drift in the past
Continental drift shows that continents came together 250 mya and drifted apart 180 mya Marsupials rode the continents to their present positions
DNA and protein sequences support descent with modification 13. If one species descended from another we would exepct that __________________________________ 14. Answer the question from the video
DNA Evidence: Comparing Amino Acid Sequences Whales make milk to feed their babies. Caseins are nutritional proteins that are found in milk. Since all mammals make milk, they all have genes that code for casein. In the mid-1990s, one group of researchers decided to investigate which mammals are most closely related to whales by looking at the amino acid sequences of casein proteins: 15. Build a phylogentic tree using the information above.
Structures present during embryo stages support descent with modification Since embryo development is coded in the DNA (inherited and changeable) Related species will have similar embryo development 16. What are the similarities between a whale embryo and a land mammal?
17. A challenge to traditional (pre-1860) ideas about species came from embryology, when it was discovered that _____. • mutations have a far more dramatic effect on embryos than on adult organisms B. all animals develop similar embryonic gills C. the more advanced the animal, the more slowly it develops D. the embryological development of many plants and animals is almost identical E.embryos of dissimilar organisms, such as sharks and humans, resemble each other
