Origin of life
Ancient Spontaneous generation of life: non living substances turn into living
Greece organisms suddenly
(1920s) Chemical reactions between inorganic molecules @early atmosphere
Alexander occurred using energy from UV light and lightning
Oparin, John - producing simple organic molecules
Haldane - washed down by rain to the ocean, the origin of life
(1953) Test supporting the Oparin-Haldane hypothesis
Miller-Urey - Mixture of CH4, NH4, H2, H2O(g) + electric sparks in an apparatus
experiment - Formation of simple organic molecules including amino acids
Today Origin of life
1. Formation of organic molecules like amino acids, sugars and
nitrogenous bases from inorganic molecules
2. Simple organic molecules joined to form complex organic
molecules like proteins, polysaccharides, nucleic acids
3. Complex organic molecules enclosed by a membrane sac,
allowing an internal environment diff from surroundings
4. Self replicating and catalytic molecules formed inside the
membrane sac, giving rise to a simple cell
Theories of evolution
- Evolution: process by which life forms developed gradually from a common origin into
varieties of organisms over a long period of time
- Life on earth start from common ancestor
- Life on earth began as simple organisms living in water
- Populations evolve (X Individuals)
- reptiles to birds: archaeopteryx with feathers skeletal anatomy
NOS: Scientific knowledge is based on observable evidence (eg. fossil)
Evidence for evolution
Fossils
- Found @sedimentary rock, provide direct evidence for evolution
- Preserved remains/impressions of past organisms which is infiltrated by minerals to
become petrified rocks
, Formation of fossils
1. Corpse sinks to bottom of lake, covered by sediments, soft parts of corpse
decompose, leaving behind hard parts like the skeleton
2. (>M of years) new sediments cover older ones, compress into layers of sedimentary
rocks; minerals in water deposit in skeleton turning it into a fossil
3. Earth movement raises sedimentary rocks above water, expose fossil by further earth
movement and weathering
2 types of fossils
Body fossils Trace fossils
(body parts): bones, teeth, shells, wood (activity): footprints, burrows, nests, eggs,
> kinds, sizes, structures of ancient dung
organisms > behaviour of ancient organisms
- living fossils: horseshoe crab
Fossil record: chronological sequence of fossils
- Estimate age of fossils
- Age of rocks where it is found by radioisotope dating
- Depth and layer where it is found: lowest, oldest
- Evidence for evolution
- Fossils @younger rocks:
- greater diversity of fossils: agree with hypothesis that organisms
evolved from common ancestry
- more complex: agree with hypothesis that organisms evolved from
simple prokaryotic organisms to complex eukaryotic organisms
- Similar to @older rocks: agree with hypothesis that existing life forms
arose from pre-existing life forms
- Diff from @older rocks: agree with hypothesis that organisms have
changed over time to adapt to changing environment
- Determine evolutionary history of organisms
- find missing links of existing organisms (fish to tetrapod)
Limitations: missing links in fossil record
- intermediate forms between related groups of organisms cannot be found
Inability to form fossils Inability to find complete fossil record
- Soft body organisms cannot be - Fossils in inaccessible areas cannot
fossilised be studied deep underground, under
- Remains of organisms eaten by the sea)
other organisms or decomposed - Most fossils are only body parts and
before fossilisation not whole organisms
- Conditions where organisms die are - Fossils may be damaged by earth
not suitable for fossilisation movement
Ancient Spontaneous generation of life: non living substances turn into living
Greece organisms suddenly
(1920s) Chemical reactions between inorganic molecules @early atmosphere
Alexander occurred using energy from UV light and lightning
Oparin, John - producing simple organic molecules
Haldane - washed down by rain to the ocean, the origin of life
(1953) Test supporting the Oparin-Haldane hypothesis
Miller-Urey - Mixture of CH4, NH4, H2, H2O(g) + electric sparks in an apparatus
experiment - Formation of simple organic molecules including amino acids
Today Origin of life
1. Formation of organic molecules like amino acids, sugars and
nitrogenous bases from inorganic molecules
2. Simple organic molecules joined to form complex organic
molecules like proteins, polysaccharides, nucleic acids
3. Complex organic molecules enclosed by a membrane sac,
allowing an internal environment diff from surroundings
4. Self replicating and catalytic molecules formed inside the
membrane sac, giving rise to a simple cell
Theories of evolution
- Evolution: process by which life forms developed gradually from a common origin into
varieties of organisms over a long period of time
- Life on earth start from common ancestor
- Life on earth began as simple organisms living in water
- Populations evolve (X Individuals)
- reptiles to birds: archaeopteryx with feathers skeletal anatomy
NOS: Scientific knowledge is based on observable evidence (eg. fossil)
Evidence for evolution
Fossils
- Found @sedimentary rock, provide direct evidence for evolution
- Preserved remains/impressions of past organisms which is infiltrated by minerals to
become petrified rocks
, Formation of fossils
1. Corpse sinks to bottom of lake, covered by sediments, soft parts of corpse
decompose, leaving behind hard parts like the skeleton
2. (>M of years) new sediments cover older ones, compress into layers of sedimentary
rocks; minerals in water deposit in skeleton turning it into a fossil
3. Earth movement raises sedimentary rocks above water, expose fossil by further earth
movement and weathering
2 types of fossils
Body fossils Trace fossils
(body parts): bones, teeth, shells, wood (activity): footprints, burrows, nests, eggs,
> kinds, sizes, structures of ancient dung
organisms > behaviour of ancient organisms
- living fossils: horseshoe crab
Fossil record: chronological sequence of fossils
- Estimate age of fossils
- Age of rocks where it is found by radioisotope dating
- Depth and layer where it is found: lowest, oldest
- Evidence for evolution
- Fossils @younger rocks:
- greater diversity of fossils: agree with hypothesis that organisms
evolved from common ancestry
- more complex: agree with hypothesis that organisms evolved from
simple prokaryotic organisms to complex eukaryotic organisms
- Similar to @older rocks: agree with hypothesis that existing life forms
arose from pre-existing life forms
- Diff from @older rocks: agree with hypothesis that organisms have
changed over time to adapt to changing environment
- Determine evolutionary history of organisms
- find missing links of existing organisms (fish to tetrapod)
Limitations: missing links in fossil record
- intermediate forms between related groups of organisms cannot be found
Inability to form fossils Inability to find complete fossil record
- Soft body organisms cannot be - Fossils in inaccessible areas cannot
fossilised be studied deep underground, under
- Remains of organisms eaten by the sea)
other organisms or decomposed - Most fossils are only body parts and
before fossilisation not whole organisms
- Conditions where organisms die are - Fossils may be damaged by earth
not suitable for fossilisation movement
