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Terms in this set (67)
Records That Provide Evidence For Evolution (Darwin)
1. Anatomical Record
2. Fossil Record
3. Patterns of Distribution
4. Molecular Record
5. Artificial Selection
Considerable variety within a species. So artificial selection is evidence for variety in a population.
-A great dane, chihuahua, poodle - all different
-By breeding together certain animals, these differences can be accentuated.
-People do this breeding, not natural
-Environment will act as a natural selector (some plants able to survive in low precipitation). Darwin and Wallace would species that can't live in that condition would die
-Natural because result of the environment (rain, low nitrogen in soil, polluted water, salinity in water, etc..)
-First Principle: Many individuals must die young, fail to reproduce or produce fewer offspring
-Second Principle: In a natural setting, the variation that helps an organism adapt to the environment is most likely to get passed on
-Third Principle: Over many generations, differential reproduction will result in changes in overall genetic makeup of a population (i.e. evolution)
-Homologous Traits = Structural vs. Homoplastic Traits
-Developmental (Embryonic) Processes
The Fossil Record
-When fossils are arrayed in the order of their age, a progressive series of changes are seen
-history of life as documented by fossils, the remains or imprints of the organisms from earlier geological periods preserved in sedimentary rock
Patterns of Distribution
Inhabitants of ocean islands resemble forms of the nearest mainland
-show the spatial relationship between members of a population within a habitat.
The Molecular Record
The longer organisms have been separated according to the fossil record, the more differences are seen in the structure of their DNA
-data used to compare DNA and protein structures between species.
Similar features in related species that are attributed to inheritance from a common ancestor
-In descent with modification, new species descend from ancestral species by the accumulation of modifications as populations adapt to new environments
-Novel features that characterize a new species are not entirely new, but are altered versions of ancestral features.
-Similarity in characteristics resulting from common ancestry is known as HOMOLOGY
-Similarity in characteristics resulting from similar ecologies or physical solutions to the same problem are known as ANALOGIES
Evolution of Limbs from Fins
-bones of fish hip and shoulder correspond to bones in this early tetrapod (amphibian)
-demonstrates that one type of vertebrate (fish) led to another (amphibian), and allowed emergence from one environment (water) to another (land)
Convergence of Design: Homoplasy (Analogies)
-groups of animals often adapt to habitats that differ from those of most other members of their group
-similar habitats (water, air, land) have similar ecological and physical demands
-see similar body and limb shapes in different ancestrial lineages
-Sometimes, homologies are not obvious in adult organisms but are in embryonic development.
-Ex: pharyngeal pouches present in all vertebrates at some stage in development develop into very different, but still homologous, adult structures, such as the gills of fish or the eustacean tubes that connect the middle ear with the throat in mammals
Novel features aren't novel!
-panda has five digits like most mammals
-true thumb is longer than that of many other mammals
-"thumb" is an enlargement of a wrist bone
-Some of the most interesting homologous structures are vestigial organs
-These structures have marginal, if any, importance to a current organism but have had important functions in ancestors
(ie Primitive snake hind limbs evolved from lizards with four legs & Whale pelvis and hind limb evolved from 4 legged animal, human tailbone, human)
-Human appendix vestigial, function use to be digestion of significant amount of plant material
-During the course of horse evolution, the peripheral toes were lost and the central toe emphasized.
-On rare occasions, however, these "lost" toes or their remnants reappear, testifying to the lingering presence of the underlying ancestral developmental pattern.
-study of past and present geographical distribution of species
-For example, islands have native species closely related to mainland populations.
-Variations develop because of relative isolation.
-Same species found on different continents
-Result of there being land bridges or connections between continents at one time with continental drift afterwards.
Most Organisms Don't Fossilize
-Hominid leaves foodprints in the mud
-Hominid dies near water
-Vultures and other scavengers pick away at muscles/organs
-Remaining flesh rots away, leaves bones behind
-Water level rises, covering bones and footprints
-Thick sequence of sediments accumulates over bones, gradually fossilize bones
-Hundreds of years later, erosion exposes bones to footprints
Occasionally Soft Tissues Fossilize
-Burgess shale in the Canadian Rockies in British Columbia CA
-505 million years ago
Fossils may provide clues about...
Scanning Electron Microscopy Provides Evidence of Cellular Structure
-Structure of melanosomes suggests striking plumage for 150 million year old protobird, Anchiornis.
CAT Scans Help Determine Function of Hadrosaur Crest
-Crest connected to nasal cavity
-Sound generated by blowing air
-Ears tuned to this frequency
-Fossil record very incomplete & discontinuous
-Many missing gaps, but can predict what intermediate forms might have existed and look for them
(ie Whales. If evolved from quadrupedal form, intermediate forms should have limbs or remnants of limbs)
-Coelacanth Fins are Homologous to Tetrapod Forelimb. Fossil record should document transition from fins to forelimbs
Charles Darwin (1809-1882) Early Years
-Attended University of Edinburgh to study medicine but disliked surgery
-Christ College, Cambridge University to prepare for clargy
-Studied under Rev. John Henslow, a botanist
HMS Beagle Journey
-Darwin offered a position as an unpaid naturalist and companion to Captain Robert Fitzroy on HMS Beagle. Departed in 1831
-22 and no formal training in science
-Took the Bible, Paradise Lost by Milton, and mad books on geology
-Given Lyell's Principles of Geology by Fitzroy
Darwin's Observations (Cape Verde)
-Initial Observations at Cape Verde Islands
-Concurrently reading Lyell's book, Principles of Geology (1830-1833)
-Book + observations transform Darwin's thinking from catastrophism (changes in world's crust resulted from sudden, violent, unusual events) to uniformitarianism (changes in earth's crust have resulted from continuous/uniform process)
Darwin's Observations (South America)
-South American Biota are distinct from those of Europe and Africa
-Temperate SA species similar to tropical SA
-SA fossils similar to living SA forms
-Geologic processes (earthquakes, volcanic activity) shape the earth
-Volcanic islands have biota similar to mainland near them
Darwin's Observations (end of Journey)
-puzzled that similar islands with similar physical ecologies could have such different flora/fauna
-flora/fauna of such islands more similar to nearby mainland
-surmised that only through colonization from mainland would Cape Verde Islands have African-like species and Galapagos Islands have American-like species
Darwin Back in England
-1836-1842: Darwin in London
-Presents geological finding to the Royal Society
-Contact and discussions with Lyell and others
-Has his collection and analyzed and catalogued
-Writes a naturalist's voyage on the Beagle (1839)
-Devises theory for the slow formation of coral reefs by slow accumulation of coral skeletons
-Discovers Malthus' essay in 1838
-Is Secretary of Geological Society of London (1838-1844)
-Married cousin Emma Wedgewood and moves to Kent (1839)
Thomas Malthus (1766-1834)
-Essay on Principle of Population
-observed that plants and animals produce far more offspring than can survive
-stated that Man too is capable of overproducing if left unchecked
-concluded that unless family size was regulated, man's misery of famine would become a global epidemic and eventually consume man
Darwin's Early Speculations (Tortoises)
Wondered if tortoise speciation on islands would be correlated with a difference in vegetation among the islands
Darwin's Early Speculations (Finches)
-Darwin speculated that all the different types of finches could have descended from a single type of mainland finch
-none of the island finches were mainland species
-Earth's island arcs arose via volcanic activity
-Live changed unidirectionally according to local climate and food present at each island within the island arc
-Geographic diversification (eg galapagos islands) species originated from a mainland form and increased in number
"most curios is perfect gradation in size of beaks in different species of Geospiza"
Summary of Darwin's shiz
-Observations of volcanic islands during travels alters Darwin's thinking from catastrophism to uniformitarianism.
-Observations that species on volcanic islands are similar to those from nearest mainland alters Darwin's thinking about species being specially created for a specific environment.
-Linking of observations and economic ideas on human populations provides concept of struggle for existence amongst individuals.
-Slowly amasses evidence for his ideas
Alfred Russel Wallace
-Traveled in the Amazon & Malaysia
-In 1855 essay on his observations about the varieties within and among species
-Proposed that every species came into existence coincident in space and time with a pre-existing, closely allied species
-Life and Earth evolved together
-Noted by Lyell but mostly ignored by others. Darwin paid attention after Lyell showed him
-Recognized in 1858
Darwin's 3 Premises
1. Creatures produce more offspring than can survive
2. Great variation within a species
3. Some of that variation is passed on to future generations
Darwin's First Premise
"The struggle for existence"
-Creatures produce more offspring than can survive.
-Darwin got the idea from Malthus that the population of a species grows faster than the food supply.
-∴ There is a competitive struggle for food and a struggle to survive.
-Those more "fit" will be better competitors, better survivors, will live, and may have offspring.
Darwin's First Conclusion
Since the populations of many organisms are rather stable over time, many individuals must die young, fail to reproduce, produce fewer offspring, or produce non-fit offspring.
Darwin's Second Premise
-There is great variation within a species.
-From collections on the Beagle, as well as in observations of pigeons, dogs, other domesticated animals, and the human species, Darwin noted huge variety within a species.
-Wallace also noted variation in species in the Amazon and Malaysia.
-Thought that variation might have a positive or negative affect on individuals
Darwin's 2nd Conclusion
-Natural Selection. in a natural setting, the variation that helps an organism adapt to the environment (i.e., obtain food, escape predators, and find a mate) is most likely to be passed on.
-Varieties could become new species!! Given the geologic age of the earth outlined by Lyell, the variation occurring within a species could become so great that varieties would become new species.
-Likewise, Wallace concluded that varieties would form new species as they diverged from the parental type.
Darwin's Third Premise
-Some of that variation is passed on to future generations.
-Although Darwin knew nothing of genetics, he knew that some of the variation that occurs within a species is passed on from parent to offspring.
Darwin's 3rd Conclusion
-Over many generations, differential reproduction will result in changes in overall genetic makeup of a population = evolution
-Given enough time, all species could have evolved from one prototype
Comparison of Darwin's and Lamarck's Model Providing a Mechanism for Transmutation of Species
LAMARCK: Change in an individual's lifetime is passed on to offspring
-Evolution always results in greater complexity.
-Evolution is purposeful, goal-oriented.
DARWIN & WALLACE: Change occurs in a population over generations.
-Evolution results in greater adaptation to the environment & better ability to procure food while avoiding predators.
-Evolution has no goal; Many changes are possible.
Points about Natural Selection and Evolution
-Variations are produced by chance mutations; this process is RANDOM & does not necessarily produce well-adapted species.
-Natural selection chooses between alternate varieties available - this process is NOT random - it can drive a species in a particular direction because it allows individuals with mutations to survive longer and produce more offspring throughout a population.
-Combination of RANDOM mutations and NON-RANDOM natural selection leads to NON-RANDOM evolution.
But evolution is not goal oriented at the outsetl
What is the Mechanism for Inheritance
-How are traits inherited?
-Only mechanism proposed at time was Lamarck's
-Little was known about cell replication, although chromatin had been discovered.
-Gregor Mendel had not yet published and would be ignored even after publishing.
-Subsequent editions of The Origin tried to deal with inheritance ... but unsuccessfully.
-Known for one of the earliest models of classification; understanding similarities and differences, useful for practical purposes, what organisms are safe to eat
-Eventually came up with questions of how those patterns came about (i.e. whether species can change at all)
-Aristotle's Classification Scheme: Scala Nature -> Scale of Nature; Included inanimate objects -- plants are the lowest organisms, human is at the top; gradually each scale shows different organisms
James Hutton (1726-1797)
-Believed Earth was subject to slow but continuous cycles of erosion and uplift
-Fundamental force at play was subterranean heat that would create chemical reactions to form basalt, granite, and mineral veins that would cause Earth's crust to heat & expand
-Geological changes are accounted by slow, natural processes (suggested Earth was very old)
-Theory of the Earth
-Erosion of rocks help form layers
-Argued that fossil records were a chronology of living creatures from different eras
-Found out through shark teeth and how they are like stones he found previously
-Different rock layers contain distinct fossils, young fossil from one layer is found in a much older layer
-Constructed first geographical map
-Found out that during the life of the organism, the old rock layer was starting to form; therefore, young fossil found in old layer because the organism dies on top of the old layer
-Wrote Principles of Geology: Expanded Hutton's idea that slow changes occurred at a uniform rate -- only a few extinctions occurred at a time, just that it's gradually adding up
-Time & life proceed in cycles such the extinct species could arise again
James Ussher (Christian world view)
-Used old testament listening of ancestries to determine the age of Earth
-Written authority = words
-Scala Natura through the Chain of Being; organisms and non-living things classified by ranks
Carolus Linnaeus (1707-1778)
-Brought order to the practice of classification
-Binomial Nomenclature: Genus (larger group) and Species (smaller group) -- species can interbreed
-Believed in natural theology, that study of nature would reveal the divine order of creation
-Believed in fixity of species
-Linnaeus' Scheme: Did not attribute dispersal of all animals to the ark; believed each pair of animals was created in a particular climatic belt in association with other species designed in similar conditions (function and structure of organism was linked to the environment in which it was created)
-Thought species in genus could change via hybridization as part of God's plan since hybrids of species were constantly present
George Louis LeClerc (1707-1788)
-Science & chemistry gave new way of thinking about the world -- Earth formed according to the laws of physics
-Described all known plants/animals
-Families were fixed but species were not; speculated that species could have descent with modification via environmental change, migration & geographical location
Etienne St. Hilaire (1772-1844)
-Looked at similar structures between species; drew up rules for deciding when structures in 2 different organisms were variants of the same type
-Developed concept of homology based criterion on connections between parts -- two different organisms with same type of structure; suggested that morphological change was not slow and gradual (occurred in bursts caused by change in embryological development or through process of convergent evolution)
-Suggests common descent for various lineages
-Wrote Natural Theology; certain complex objects suggest an intelligence that caused them (Watchmaker argument)
-Even if we don't understand how things come about, it is from the intelligent; God is a designer and some designs may not function properly
Georges Cuvier (1769-1832)
-Founded science of paleontology (study of fossils)
-Believed in fixity of species and creation; used Catastrophism to explain mass extinction -- established extinction as a fact
-Appearance of new fossils in new strata of rocks; after catastrophe, God creates new species
-Studied river bends around Paris - saw that some layers had fossils while others didn't -- Top layer = complex fossil, Bottom layer = less complex; Each series of layers represent different epochs -- Earth was very old
-There was a time before any organism appeared on Earth - after organism appeared, epoch had its own fauna and flora; based on strata, complex fossils (organisms) came after simple ones
-Concluded species do not change over time
-Instead, revolution of destruction wiped out the species and brought new ones
-4 separate creations: Molluscan, Articulated, Radiated, Vertebrate
Jean Baptiste de Lamarck & Lamarck's "Law" of Increasing Complexity
-Work on invertebrates
-Life is polyphyletic (many origins)
-Believed in evolution - complicated structure came from simple ones
-Believed that if organism uses one organ more than its ancestor, organ would change during its lifetime
-First Law: change in environment causes changes in needs of organism; altered behavior leads to greater or lesser use of given structure or organ
-Second Law: All such changes were heritable via pangenes
Lamarck's Premise of Inheritance of Acquired Characteristics
-Linked diversity with adaptation to environment
-Individual traits are malleable and can be shaped through environment
-Information will be collected in the body around a certain favorable trait (evidence is through vestigial organs)
-Individuals strive for change (ascend in ladder of evolution, organisms will not go extinct but become more complex than ever)
Scala Naturae (Chain of Being)
-Strict religious hierarchical structure of all matter and life
-Starts with God on top and processes downwards from stars
-Derived from Aristotle
-Wild beasts dominate over domestic animals, useful animals over docile, mammals over birds etc.
-Plants were the lowest level
-Ladder of life concept (placing organisms based on complexity of structure & function)
-Slow changes occur at a uniform rate
-Few extinctions occur at a time gradually adding up
-Intrinsic Process: slow continual change in the environment (global ice ages -> melting of ice, extremely large volcanic episodes, periodic mass extinction, mountain building)
-Extrinsic Process: not part of the essential nature, comes from something outside (large meteor hits Earth every 10-50 million years)
Catastrophism (Neptunism and Volcanism)
-Cuvier came up with catastrophism to explain mass extinction -- opposite of uniformitarianism
-Different types of catastrophism: Neptunism: Geology is the result of floods and a recession of the ocean; Volcanism: Geology is the result from violent volcanic activity and uplift, followed by erosion; provides evidence for discontinuity of fossil strata and emergences of new islands in oceans
Natural Selection as a Driving Force for Evolution
-Variations are produced by chance mutations (this is a random process) -- doesn't necessarily make well-adapted species
-Natural selection chooses between alternate varieties available - not random
-Cannot make "better" adapted organisms
-Drive a species to one direction because it non-randomly spreads mutations that allow individuals to survive longer and produce more offspring throughout a population
-Darwin & Wallace: Evolution results in greater adaptation to the environment (get food while avoiding predators)
-Lamarck: Evolution results in greater complexity
-Although artificial selection does occur (guided); competition in nature would cause the same kind of variety by natural selection by any providence
-Natural selection seen as threat to Paley's argument
Evidence for evolution: Why Artificial Selection is a good analogy
-Plants were domesticated in many regions of the world
-Taming can change the coloration of fur for certain animals
-Keep reproducing the wanted genes/characteristics
Evidence for evolution: fossil record, transitional fossils, how fossilization occurs
Fossil Record: Document the course of life through time - most organisms do not fossilize; fossils leave clues about behavior of that specific organism, and provides its development
-CAT scans help determine functions of animal body parts
-Transitional Fossil: Evolutionary change in body size, crown height, molar base, expansion and toe reduction of horses; transition of bone structure seen through fossils of species that are similar to one another -- the middle fossil shows the evolution
-How fossils are formed: Dead organisms decay overtime, replicated some of the chemistry that turns the tissue into rocks, Microbes feed on the cadaver leaving the skeleton behind, skeleton is buried in sediment and ash, water percolates through the sediment and fills up the bone or shell with mineral, sediment turns into rock
Evidence for evolution: Homology/Homoplasy, Ontogeny, Vestigial Organs
-Homology (Darwin): Suggests how species might change via environment, common descent for various lineages, similar traits because of common ancestor; i.e. vertebrate jaws evolved from jawless ancestors
-Homoplasy: Similarity not due to common ancestor -- due to similar ecologies or physical solution to a problem; i.e. wings of bats and birds - common ancestor didn't have similar traits
-Vestigial Organs: Some of the most interesting homologous structures are these organs; had important function for ancestor; silenced genes (i.e. goosebumps on humans)
Evidence for evolution: Biogeography - distribution of animals/species
-Study of past and present geographical distribution of species (i.e. islands have native species which are closely related to homeland species)
-Variation develops because of isolation
-Same species found in different continents
Evidence for evolution: Molecular Record/Clock
The longer organisms have been separated according to the fossil records, the more different are seen in the structure of their DNA
-By evolutionary biologists because each group includes all of the descendants of a particular common ancestor
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