Unit 7: Evolution & Classification

Name: Unit 7: Evolution & Classification
Uploaded: 2017-10-05T19:33:28+00:00
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Description: Unit 7: Evolution & Classification

Unit 7: Evolution & Classification
Ch 12 & 13 (Evolution, Adaptation, & Speciation)

The theory that species have changed gradually over time.
Evolution The theory that species have changed gradually over time. change in the gene pool of a population from generation to generation by such processes as mutation, natural selection, and genetic drift

Evidence to support the Theory of Evolution
Ch 12.1 Evidence to support the Theory of Evolution Indirect Evidence Fossil Record Comparative Anatomy Comparative Embryology Comparative Biochemistry Direct Evidence Current observations Indirect  don’t actually see happening… Direct  see happening….

Indirect Evidence: Fossil Record
Evidence of: change in organisms over time age of the Earth Evidence of change over time—types of organisms change from one layer to the next… in general, simpler body structures found in older layers & more complex structures found in younger/more recent layers… However, many of the simpler life forms still exist Fossil record is incomplete Age of the Earth James Hutton( ) Earth formed by slow and gradual processes – not sudden violent events Change itself is natural - not an unusual event

Indirect Evidence: Fossil Record
Once living remains of organisms Limited: Type of material preserved (bone, shell, impressions, amber) Incomplete record Easily disrupted Fossils are the traces or impressions of organisms from the past, mineralized in sedimentary rocks Fossils w/in layers show that a succession of organisms have populated Earth throughout time Fossilization is an exceptionally rare event b/c most organisms tend to decompose quickly after death to be fossilized must be covered in sediment as quickly as possible… (this is why more fossils of shells & aquatic organisms) Exceptions… frozen, dried, anoxic environment…

Formation of Sedimentary Rock Layers & Fossilization
Principle of original horizontality… Law of superposition Correlation (of layers & fossils) ex. across river..

Law of Superposition Which layer is youngest? oldest?
Explain your reasoning…

Law of Superposition Lower layers = older Upper layers = younger

Indirect Evidence: Comparative Anatomy
Compares structures of different organisms living today Homologous structures Analogous structures Vestigial structures

Homologous Structures similar structure w/ modifications common ancestor divergent evolution becoming more different Homologous Structures – Parts on different organisms that are similar in structure (and sometimes function) and seem to indicate common origin – common ancestor. Indicate divergent evolution – things becoming more different.

2. Analogous Structures similar function but not structure do NOT have common ancestor convergent evolution becoming more similar Unrelated organisms look similar b/c of common environmental conditions Ex. fins of fish/whale

3. Vestigial structures reduced size or function Often no apparent use evidence that organism has changed

Indirect Evidence: Comparative Embryology
Embryonic development Pattern Early stages  very similar Later stages  more distinction Inherited same basic body plan from common ancestor More similar developmental stages  more closely related Fish, salamander, tortoise, chick, hog, cat, rabbit, human

Indirect Evidence: Comparative Embryology
Trilobites & Horseshoe crab larvae

Indirect Evidence: Comparative Biochemistry
Similar organic compounds coded for by similar DNA Ex. proteins hemoglobin Cytochrome c is a protein used in cellular respiration

DNA  most reliable form of evidence Human & chimpanzees 98% similar Humans & other mammals 80% similar Ex. amino acid sequences….

What is the significance of 2 very different species sharing large amounts of the same DNA? phylogeny Phylogeny = Evolutionary history of a living organism based on such factors such as fossil evidence & biochemical comparisons Relationships shown through phylogenetic tree

Indirect Evidence: Genetic Evidence
Each generation of organisms in a population shows some variation result of: mutations genetic recombination Variation result of mutations (new alleles) & genetic recombination [from meiosis (crossing over during prophase 1 & how chromosomes line up during metaphase 1) & fertilization during sexual reproduction] Speeds up evolution b/c creates more variety Selective breeding (artificial selection) humans directing selection of organisms w/ desirable traits…  directing evolution

Direct Evidence: Observation
Rapid evolution Antibiotic resistant bacteria Resistance of insects to pesticides HIV strains

Antibiotic resistant bacteria MRSA

2. Pesticide resistant insects

Mechanisms for Evolution
HOW evolution happens…. Jean Baptist Lamarck Charles Darwin Alfred Wallace

Lamarck vs. Darwin Jean Baptist Lamarck (1744 – 1829) “Theory of Acquired Characteristics” use vs. disuse acquired traits are passed on & leads to changes in species Increasing complexity Experimentation failed to support Lamarckism Proclaimed that all species, including our own, are descended from other species Inheritance of Acquired characteristics Organs became stronger with use Changes due to use or disuse could be then transferred to offspring Body parts used extensively to cope w/ environment became larger & stronger, while those not used deteriorated Also thought that modifications acquired during the life of an organism could be passed on to offspring Classic example  long neck of the giraffe… could acquire longer necks by reaching for leaves on higher branches & would pass this characteristics on to their offspring This sort of evolution, for which Lamarck is most famous today, was only one of two mechanisms he proposed. As organisms adapted to their surroundings, nature also drove them inexorably upward from simple forms to increasingly complex ones.

Do you see any problems with Lamarck’s ideas? Thought acquired traits could be passed on… What information was he lacking? He thought that all life was striving upward in complexity. What do you think of this concept? Acquired traits do not change genes transmitted by gametes to offspring (ex…. Tattoos, piercings, Lamarckian inheritance remained popular throughout the 1800s, in large part because scientists did not yet understand how heredity works. With the discovery of genes, it was finally abandoned for the most part.

Charles Darwin ( )

Darwin’s Explanation: Gathering Data
Ch 12.2 Darwin’s Explanation: Gathering Data 1. naturalist on HMS Beagle (1831-6) Collected fossils & specimens Observed tremendous biodiversity Darwin set sail – most important voyage in the history of biology The captain if the HMS Beagle offers free passage to anyone who will act as an naturalist - voyage takes 5 years!! Not yet 23, had given up plans to be a doctor Indifferent student Avid collector of beetles, mollusks and plants! – why is this so important? Amateur geologist – interested in the formation of the planet – changes!!! By the end of his trip he concluded, life forms can & do change…. Formulated his idea of “Descent with Modification” (changes occur from one group of descendants to the next)

2. Studied work of geologist Charles Lyell “The present is the key to the past.” Darwin  organisms that are adapted to their environments must also change to remain adapted 2. Studied Charles Lyell – geologist “The present is the key to the past.” The same forces acting on earth in the past are continuing today. Clear to Darwin that organisms adapted to their environments must also change to remain adapted. Animals and plants were well adapted to different environments of diff islands!

But, Darwin questioned how this change occurred… Concluded  evolution or “descent with modification” Questioned how this change occurred… ~answers pointed to evolution or “descent with modification” (structural or functional changes occur from one group of descendents to the next) By the end of his trip he concluded, life forms can & do change….

Darwin’s Explanation:
In the Galapagos By the end of his trip he concluded, life forms can & do change….

Darwin’s Explanation:
In the Galapagos noticed unique organisms (yet similar to other forms of the same animals in other parts of the world) Persuaded Darwin that these organisms were all related to other known forms By the end of his trip he concluded, life forms can & do change…. Saddleback long neck, curved shell, found on Hood Island, desert like Dome-shaped shorter neck, domed shell, lush vegetation, covers the ground, Isabela island

Climate variation throughout
The Galapagos Islands Desert Large rainfall Intermediate Shell Domed Shell Saddle backed Shell Climate variation throughout By the end of his trip he concluded, life forms can & do change….

Darwin’s Explanation: In the Galapagos
Darwin was convinced evolution occurs… Still needed to test ideas before explaining how or why such changes happen

Darwin’s Explanation: Natural Selection
2 clues led to Darwin’s explanation of how evolution occurs 1st clue: Studied work of Thomas Malthus (1798) Human population growing faster than resources Malthus concludes  Don’t worry, it will fix itself! How? Why? How did this influence Darwin’s thinking? Upon his return from England he reads an essay by Thomas Malthus. Malthus warns that the human population is increasing too quickly for the planet. Larger the population gets – larger the rate of reproduction W/ pop growth comes competition Malthus concludes – don’t worry – it will fix itself! How? Why? Overproduction  any offspring produced die before reaching maturity due to competition for scarce resources, illness, starvation, etc. How would these ideas have influenced Darwin’s thinking? Darwin extended idea to other organisms.

Darwin applied Malthus’ ideas to other life forms Overproduction of offspring Why is this necessary? How might this influence Darwin’s thinking? Ex. finding nemo… many eggs laid… all but one eaten…. Necessary to ensure that at least some of the offspring survive long enough to reach maturity & reproduce (to pass on genes) Survivors… those best suited for environment (“fittest”) Influence Darwin’s thinking… realized struggle for existence…  competition

Realized w/ decreased resources  struggle for existence Survivors – ~Who are they? ~What influences their survival? ~How did they get these traits? ~Were these traits a response to their environment? Kinds of struggle  Competition for food & space, escape from predators, ability to find shelter EVOLUTION does not occur w/ a purpose… certain features are not developed “in order to” adapt to change in env…. Variation exists in population (usually due to random mutation &/or sexual reproduction) & certain variations become useful when env changes… the organisms w/ the best-suited variations survive & produce offspring while others dies before they can reproduce… in this way a population/species becomes adapted to its environment…

2nd clue: noted artificial selection (selective breeding) Used by farmers & breeders to produce preferred offspring Choose parents w/ desired traits to breed together Darwin reasoned that if we could artificially select traits, then the same process should occur naturally… Evolution is different b/c relies on variation & chance w/o human “interference”

Darwin wondered, “Is there a force in nature that simulates artificial selection???”

Struggle for existence & artificial selection gave Darwin info he needed to explain how evolution occurs In any given population of organisms there will be a large variety of traits. What causes variety? S – sexual reproduction… speeds up evolution b/.c increase genetic variety Darwin did not know about mutations, but did know there was variation!!!!! Variation exists among all groups of organisms Individuals w/ variations for traits adaptive for their environment have a better chance of survival, & thus, leave more offspring b/c variations can be inherited, many offspring will have those same traits Organisms lacking those traits are less likely to survive & tend to leave fewer offspring ~over time, the population consists only of adapted organisms

Sources of variation S – sexual reproduction C – crossing over during meiosis A – arrangement of chromosomes (alleles) during meiosis M – mutations Darwin did NOT have knowledge of genetics!!! What we know about genetics today supports Darwin’s theory of natural selection…

Variations can be adaptations traits that make an organism better able to survive in its environment Pepper Moth “Game” Principles of Natural Selection "Interactive" Camouflage Ex. Desert  adaptations for temp extremes & water availability EVOLUTION does not occur w/ a purpose… certain features are not developed “in order to” adapt to change in env…. Variation exists in population (usually due to random mutation &/or sexual reproduction) & certain variations become useful when env changes… the organisms w/ the best-suited variations survive & produce offspring while others dies before they can reproduce… in this way a population/species becomes adapted to its environment…

Adaptations are NOT a response to the environment just happen to be “useful” when environment changes Any selection that occurs in a population is natural “survival of the fittest” Evolution does not happen according to a plan or goal… EVOLUTION does not occur w/ a purpose… certain features are not developed “in order to” adapt to change in env…. Variation exists in population (usually due to random mutation &/or sexual reproduction) & certain variations become useful when env changes… the organisms w/ the best-suited variations survive & produce offspring while others dies before they can reproduce… in this way a population/species becomes adapted to its environment…

Natural selection & “survival of the fittest” Individuals best adapted for their environment have high levels of fitness Naturally selected for, survive, & reproduce More offspring have favorable adaptation than before (if heritable) Evolution does not happen according to a plan or goal… interaction btwn organisms & environment… Variation exists among all groups of organisms Individuals w/ variations for traits adaptive for their environment have a better chance of survival, & thus, leave more offspring b/c variations can be inherited, many offspring will have those same traits Organisms lacking those traits are less likely to survive & tend to leave fewer offspring ~over time, the population consists only of adapted organisms EX. Insects & pesticide resistance

Ex.  Pepper Moths – England Original color – 99% white (trees w/ light bark) Industrial Revolution, 1850s – produced smog Enviro. changes s - 99% black (trees w/ dark bark) Pepper Moth “Game” Principles of Natural Selection "Interactive"

Divergent evolution Finches on different islands ate different foods… beak adaptations that helped them gain more food (& thus survive & reproduce) were selected for & passed on to offspring…. Eventually causing adaptive radiation so that birds on different islands had beaks that were more suited to the type of food available on that island (other beak types that were not well adapted to that food type were selected against)…

Divergent evolution

Divergent evolution Adaptive Radiation

Adaptive Radiation: Hawaiian Honeycreepers
Divergent evolution

On the Origin of Species by Means of Natural Selection (1859)
Summary of Theory of Natural Selection: 1. Overproduction of offspring 2. Variation within population 3. Struggle to survive  competition 4. Successful reproduction – “survival of the fittest” (best adapted) Overproduced variations struggle to successfully reproduce…

Darwin envisioned the tree of life
Phylogenetic Tree Darwin envisioned the tree of life

How would Darwin adjust the description given by Lamarck about the length of giraffes necks?

Darwin’s Explanation: Wallace’s Same Conclusion
1858, Alfred Wallace, arrived at same basic explanation as Darwin Darwin usually given credit but BOTH men should be credited with idea of natural selection By early 1840s Darwin developed major features of theory of natural selection as mechanism for evolution. Reluctant to publish, continued to compile evidence 1858, Alfred Wallace, naturalist working in East Indies, sent Darwin manuscript containing a theory of natural selection essentially identical to Darwin’s. Did not know Darwin had been developing a theory of the process behind evolution Later that year, both Wallace’s paper and extracts of Darwin’s essay were presented to the Linnaean Society of London. Darwin quickly finished The Origin of Species and published it the next year. While both Darwin and Wallace developed similar ideas independently, the essence of evolution by natural selection is attributed to Darwin because he developed and supported the theory of natural selection earlier and much more extensively.

Population Genetics Natural selection acts on individuals, BUT populations evolve Individual’s genes stay the same Population’s gene pool may change evolves as allele frequencies (%) change due to natural selection Remember, population, NOT individual evolves… Individual’s genes stay the same but genes w/in a population may change Gene pool: the entire collection of genes among a population Each new offspring in a population draws its genes from the same gene pool. Allele frequencies  % of an allele in a population (determines frequencies of genotypes & phenotypes in populations)

Population Genetics Which trait was a better adaptation and selected for? How were frequencies of different alleles affected?

The “Big Bang” Theory 12.3

History of Earth Earth ~4.6 bill. yrs old Early earth
hostile environment volcanoes, lightning, meteorites, UV light Alexander Oparin 1936: proposed primitive atmosphere contained: methane, ammonia, hydrogen, water vapor What’s missing? All elements for life present – but no pure oxygen

Origin of Life Life ~3.5 billion years old
Stanley Miller (& Harold Urey) 1953-simulated primitive atmosphere zapped w/ electricity After 1 week produced amino acids & other simple organic molecules (in water) Precursors to 1st cells Zapped w/ electricity (similar to lightning in atmosphere) After 1 week-produced Amino Acids & other simple organic molecules in water (similar to ocean)!

The First Organisms: Heterotrophs
“Primordial Soup Hypothesis” or “Heterotroph Hypothesis” Simple compounds  Complex compounds  Primitive pre-cells  Prokaryotes (1st cells) Heterotrophs could not produce their own food & instead fed on the organic material from the primordial soup (in oceans) give this theory its name

The First Organisms: Heterotrophs
Why were heterotrophs 1st? Similar to some present-day bacteria Obtained energy from simple chemical reactions Heterotrophs first – Why? b/c no oxygen

Later Organisms: Autotrophs
Prokaryotic autotrophs followed heterotrophs What did they release into the atmosphere? produces oxygen – the oxygen revolution! Why is this so important? development of eukaryotes & more complex organisms Autotrophs follow and cause the release of? oxygen Why is this so important? Allows for development of eukaryotes & more complex organism Stromatolites are the oldest known fossils, dating back more than 3 billion years. They are colonial structures formed by photosynthesizing cyanobacteria and other microbes. Stromatolites are prokaryotes(primitive organisms lacking a cellular nucleus) that thrived in warm aquatic environments and built reefs much the same way as coral does today. Cyanobacteria were likely responsible for the creation of earth's oxygen atmosphere. They were the dominant life form on Earth for over 2 billion years. Today they are nearly extinct, living a precarious existence in only a few localities worldwide stromatolites

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