Unit 7: Evolution & Classification Ch 12 & 13 (Evolution, Adaptation, & Speciation)
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Transcript of Unit 7: Evolution & Classification Ch 12 & 13 (Evolution, Adaptation, & Speciation)
Unit 7: Evolution & Classification
Ch 12 & 13 (Evolution, Adaptation, & Speciation)
Evolution
The theory that species have
changed gradually over time.
Ch 13 & 14
Evidence to support the Theory of Evolution
• Indirect Evidence– Fossil Record– Comparative Anatomy– Comparative Embryology– Comparative Biochemistry
• Direct Evidence– Current observations
Ch 12.1
Indirect Evidence: Fossil Record• Evidence of:
– change in organisms over time– age of the Earth
• Once living remains of organisms
– Limited:1. Type of material
preserved (bone, shell, impressions, amber)
2. Incomplete record
3. Easily disrupted
Indirect Evidence: Fossil Record
Formation of Sedimentary Rock Layers & Fossilization
Law of Superposition• Which layer is youngest? oldest?
– Explain your reasoning…
• Lower layers = older
• Upper layers = younger
Law of Superposition
Indirect Evidence:Comparative Anatomy
• Compares structures of different organisms living today1. Homologous structures2. Analogous structures3. Vestigial structures
1. Homologous Structures• similar structure w/
modifications• common ancestor
• divergent evolution • becoming more
different
Indirect Evidence:Comparative Anatomy
• 2. Analogous Structures – similar function but
not structure• do NOT have
common ancestor– convergent evolution
» becoming more similar
Indirect Evidence:Comparative Anatomy
• 3. Vestigial structures– reduced size or function
• Often no apparent use
– evidence that organism has changed
Indirect Evidence:Comparative Anatomy
Indirect Evidence:Comparative Anatomy
• Embryonic development– Pattern
• Early stages very similar
• Later stages more distinction
– Inherited same basic body plan from common ancestor
Indirect Evidence:Comparative Embryology
• Trilobites & Horseshoe crab larvae
Indirect Evidence:Comparative Embryology
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
Indirect Evidence:Comparative Biochemistry
• What is the significance of 2 very different species sharing large amounts of the same DNA?– phylogeny
Indirect Evidence:Comparative Biochemistry
• Each generation of organisms in a population shows some variation – result of:
• mutations• genetic recombination
Indirect Evidence:Genetic Evidence
Direct Evidence: Observation• Rapid evolution
1. Antibiotic resistant bacteria
2. Resistance of insects to pesticides
3. HIV strains
1. Antibiotic resistant bacteria
• MRSA
Direct Evidence: Observation
Direct Evidence: Observation2. Pesticide
resistant insects
Mechanisms for Evolution• HOW evolution happens….
– Jean Baptist Lamarck– Charles Darwin– Alfred Wallace
Mechanisms for Evolution• Lamarck vs. Darwin
– Jean Baptist Lamarck (1744 – 1829)1. “Theory of Acquired
Characteristics”– use vs. disuse
» acquired traits are passed on & leads to changes in species
2. Increasing complexity– Experimentation failed to support
Lamarckism
• 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?
Mechanisms for Evolution
Charles Darwin (1809-1882)
Darwin’s Explanation:Gathering Data
• 1. naturalist on HMS Beagle (1831-6)– Collected fossils & specimens– Observed tremendous biodiversity
Ch 12.2
•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
Darwin’s Explanation:Gathering Data
–But, Darwin questioned how this change occurred…»Concluded evolution or “descent with modification”
Darwin’s Explanation:Gathering Data
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
Darwin’s Explanation:In the Galapagos
Saddleback
• long neck, curved shell, found on Hood Island, desert like
Dome-shaped
• shorter neck, domed shell, lush vegetation, covers the ground, Isabela island
The Galapagos Islands
DesertLarge rainfall
Intermediate Shell
Domed Shell
Saddle backed Shell
Climate variation throughout
• Darwin was convinced evolution occurs…– Still needed to test
ideas before explaining how or why such changes happen
Darwin’s Explanation:In the Galapagos
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?
• Darwin applied Malthus’ ideas to other life forms– Overproduction of offspring
» Why is this necessary?
» How might this influence Darwin’s thinking?
Darwin’s Explanation: Natural Selection
–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?
Darwin’s Explanation: Natural Selection
– 2nd clue: noted artificial selection (selective breeding)• Used by farmers &
breeders to produce preferred offspring
Darwin’s Explanation: Natural Selection
• Darwin wondered, “Is there a force in nature that simulates artificial selection???”
Darwin’s Explanation: Natural 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?
Darwin’s Explanation: Natural Selection
• 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!!!
Darwin’s Explanation: Natural Selection
• Variations can be adaptations– traits that make an organism better
able to survive in its environment
Darwin’s Explanation: Natural Selection
Pepper Moth “Game” http://www.techapps.net/interactives/pepperMoths.swf
Principles of Natural Selection "Interactive"
Camouflage
• 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”
Darwin’s Explanation: Natural Selection
– 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)
Darwin’s Explanation: Natural Selection
Darwin’s Explanation: Natural Selection
• Ex. Pepper Moths – England– Original color – 99% white (trees w/ light bark)
• Industrial Revolution, 1850s – produced smog– Enviro. changes - 1890s - 99% black (trees w/ dark bark)
Darwin’s Explanation: Natural Selection
Pepper Moth “Game” http://www.techapps.net/interactives/pepperMoths.swfPrinciples of Natural Selection "Interactive"
Adaptive Radiation
Adaptive Radiation: Hawaiian Honeycreepers
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)
Darwin envisioned the
tree of life
Phylogenetic Tree
How would Darwin adjust the description given by Lamarck about the length of giraffes necks?
• 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
Darwin’s Explanation:Wallace’s Same Conclusion
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
• Which trait was a better adaptation and selected for?
• How were frequencies of different alleles affected?
Population Genetics
The “Big Bang” Theory12.3
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?
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
• “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
The First Organisms: Heterotrophs
• 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
Later Organisms: Autotrophs
stromatolites