origin of life
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presentation about origin of life, biology, science.
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origin of life
- 1. Welcome!
- 2. E.O. Wilson • Two time Pulitzer Prize Winner • Discovered pheromones! • National Medal of Science • Coined the term Biodiversity
- 3. What is life? What makes something “alive”? How are living things different from non-living? What features are characteristic of living things?
- 4. 1. Complex, ordered structure
- 7. 4. Energy acquisition & transformation
- 8. 5. Response to environment (stimuli)
- 10. 7. Evolutionary change & adaptation
- 11. Physical traits all living things share •Composed primarily of the same atoms – carbon (C), hydrogen (H), and oxygen (O) • The cell is the basic living unit - capable of exhibiting all 7 emergent properties • DNA = the molecule of inheritance and cell functional & structural information
- 12. Sequence of events leading to Life on Earth 1. Origin of Earth & early environment 2. Origin of life molecules (monomers & polymers) 3. Origin of self-replicating molecules 4. Formation of pre-cells “proto-cells” 5. Origin of living cells
- 13. 1. Origin of Earth : 4.4 – 4.6 bya hot gaseous phase cooling, solidification & layering
- 14. Early “energy” environment • Warm atmosphere • High UV radiation (no ozone layer) • Electricity (thunderstorms) Early earth atmosphere • CO2, N2, CH4, NH3, H2O • essentially no oxygen Early earth oceans • shallow • hot • not salty *atmosphere & oceans begin to form about 4.0 bya Earth’s early environment
- 15. 2. Origins of life molecules Where did macro-organic molecules come from? (proteins, carbohydrates, etc.) Most favored hypothesis: abiotic (spontaneous) origins on earth Stanley Miller
- 16. amino acids, nucleotides, glucose, etc. Organic monomers form spontaneously!
- 17. Alternative hypothesis for the first organic monomers: “the cosmological hypothesis” comets & meteorite impacts
- 18. “Murchison” meteorite • 92 amino acids identified in the Murchison meteorite • 19 found on Earth; remaining amino acids are “alien”. • other meteorites contain carbohydrates, nucleic acids
- 19. If organic monomers were present early in Earth history.... Then how were polymers formed?? amino acids, nucleotides, glucose, etc.
- 20. • amino acids, nucleic acids, etc., bind to“clay” •(very small mineral particles) • clay particles hold monomers in close proximity • drying, heating, UV radiation spontaneously forms bonds between monomers = polymers Abiotic synthesis of polymers
- 21. 3. Origin of self-replicating molecules can occur without enzymes some polymers act as more efficient complementary strand templates
- 22. 4. Formation of pre-cells “proto-cells”
- 24. 5. Origin of living cells: Prokaryotes fossilized bacteria living bacteria • prokaryotic cells (bacteria & archaea) • found as fossils: 3.5 billion years old • heterotrophic (not photosynthetic)
- 27. 4 major ERAS • Precambrian • Paleozoic • Mesozoic • Cenozoic The Geologic Timescale
- 28. Origin of living cells: eukaryotic cells Endomembrane system • includes nuclear membrane, endoplasmic reticulum, etc. • derived from plasma membrane Mitochondria & chloroplasts • endosymbiosis • hypothesis for origin of eukaryotic cells • remnants of once free-living prokaryotes took up residence inside transitional prokaryotic-eukaryotic cell mitochondria chloroplasts
- 29. • have own DNA • protein synthesis similar to bacteria • divide / replicate independently Evidence for the endosymbiotic hypothesis Mitochondria & chloroplasts:
- 30. Earliest eukaryotes similar to present-day unicellular members of Kingdom Protista
- 33. Multicellular forms of life probably arose from colony-forming protists
- 35. Appearance of multi-cellular life: animals The earliest multi-cellular eukaryotes (animals) forms of life perhaps 800 million years ago Animals: • all heterotrophic, eukaryotic, multicellular • feed by ingestion • motile at least during some part of life cycle
- 36. How do we keep track of all this diversity? Binomial nomenclature Carolus Linnaeus (1707 – 1778) • Swedish physician, botanist • Developed the concept of taxonomy • Classified similar species (by morphology) into increasingly general categories
- 37. DOMAIN ARCHAEA
Editor's Notes
- Biologists have described more than 1.7 million species of living organisms!!!
- There are 7 Emergent properties of life Complex, ordered structure Reproduction (biogenesis) Growth & development Energy acquisition & transformation Response to environment (stimuli) Homeostasis Evolutionary change & adaptation
- Earth was formed about 4.5 bya Lacked a suitable atmosphere for life, much less a hydrosphere or even land surfaces!
- Early earth was not hospitable to life as we know it: Ammonia, nitrogen, methane, water, carbon dioxide
- Stanley Miller conducted experiments in 1950’s abiotic origins of building blocks of macro-organic compounds Primordial sea in flask in his hand, electrical source above simulates electrical discharge into ancient “atmosphere” Containing ammonia, hydrogen, methane and water vapor These and similar reactions can/have produced all 20 amino acids, several sugars, lipids, nucleotides & ATP! Which can produce the macro-organic molecules needed to build life.
- Some meteorites have crashed to earth containing organic molecules.
- What were the first genes like? Hypothesis: -short strands of RNA that replicated w/o enzymatic proteins -in lab, short RNA strands can assemble spontaneously from nucleotide monomers w/o enzymatic proteins -end up with a bunch of RNA strands all with different, random sequences of nucleotides -some self replicate (varying success among strands), ones with best success increase in frequency ALSO... -RNA are able to self replicate because their are catalytic RNAs called ribozymes -early ribozymes could have catalyzed their own replication
- *cooperation much more efficient if packaged together in a membrane (pre-cells) keeps molecules close, in a solution different from environment *lab experiments show that such pre-cells can form spontaneously from abiotically produced organic compounds Certain types of pre-cells: -have selectively permeable membranes -store energy in form of voltage across their membranes -can discharge this voltage -if also include certain enzymes, pre-cells display a rudimentary metabolism (absorb substrate from surroundings and release reaction products) Left – one way RNA and polypeptides could have cooperated in a prebiotic world Cooperation here is between nucleic acids and polypeptides Right – a membrane enclosed pre-cell Here RNA genes benefit exclusively from their protein products rather than sharing them with other molecular complexes
- From these pre-cells, just a matter of Natural selection to the first living cells! By 3.5 billion years ago, prokaryotes flourishing, All branches of life originated from those ancient prokaryotes! Artist’s rendition of what Earth looked like ~3billion years ago Pad-like objects represent prokaryotes (know from the fossil record)
- Prokaryotes Lived and evolved alone on Earth for 2 billion years! Today found whereever there is life, outnumber all the eukaryotes combined Found in hostile habitats – e.g. thermophiles of hotsprings, walls of a gold mine 2 miles below Earth’s surface Some cause serious illness (Black death (aka bubonic plague), TB, cholera, food poisoning) But also are beneficial (bacteria in our intestines give us vitamins, some in our mouths prevent growth of harmful fungi) Also largely responsible for break-down of dead organic materials *without prokaryotes, live on earth would end (but could do just fine without eukaryotes)
- Shape is important identifier of prokaryotes 3 shapes are: Top left – spirochetes (spirals, e.g. syphilis, Lyme disease) Bottom left – cocci (spheres, from Greek word for berries, e.g. staph – staph infection, streptococcus – strep throat) Bottom right – bacilli (rods) Most prokaryotes are unicellular and very small (but some form colonies, some have simple multicellular arrangement with specialized cells)
- Left – yellow rods are bacteria (Haemophilus influenzae) on skin cells of human nose interior -pathogens transmitted through air, cause pneumonia and other lung infections that kill ~4million people per yr around world Right – tick that carries the Lyme disease and Bull’s eye rash Lymes is currently the most widespread pest carried disease in the US Caused by a spirochaete bacterium carried by ticks that live on deer and field mice Usually starts as a red rash shaped like a bull’s eye around the bite Antibiotics cure if given within a month of the bite Without treatment = arthritis, heart disease, nervous disorders Use insect repellant, wear light colored clothing & check for ticks!
- After photosynthetic prokaryotes evolved, oxygen accumulated in Earth’s atmosphere (~2.5 mya) Prokaryotes had earth to themselves for about 2 billion years and then... Eukaryotes arrived about 1.7 million years ago -explosion in forms of eukaryotes (these were the protists) -then (~1 billion ya) multicellular forms of eukaryotes (again, protists; from colonial single cell forms) Then first animals, followed by... At the beginning of the Paleozoic, was the Cambrian explosion -by the end of this, all major phyla had evolved For first three billion years of Earth – all life was aquatic, -~475 mya, plants and their symbiotic fungi colonize land (even today these plants have their fungi which aid in absorption of water and minerals from soil) Once plants on land, animals follow (amphibians that descended from air-breathing fish with fleshy, weight-supporting fins) Then reptiles from amphibians, birds & mammals from reptiles.
- Eukaryotes evolved about 1.7 million years ago -explosion in forms of eukaryotes (these were the protists) -then (~1 billion ya) multicellular forms of eukaryotes (again, protists; from colonial single cell forms) Eukaryotes differ from Prokaryotes in that.... Thought they got these organelles through endosymbiosis
- Evidence to support this theory includes...
- Earliest forms were similar to present day unicellular members of the Kingdom Protista
- Flagellate algae (Chlamydomonas) – unicellular green algae with a pair of flagella
- For first three billion years of Earth – all life was aquatic, -~475 mya, plants and their symbiotic fungi colonize land (even today these plants have their fungi which aid in absorption of water and minerals from soil) Once plants on land, animals follow (amphibians that descended from air-breathing fish with fleshy, weight-supporting fins) Then reptiles from amphibians, birds & mammals from reptiles.
- Then first animals, followed by... At the beginning of the Paleozoic, was the Cambrian explosion -by the end of this, all major phyla had evolved
- At the highest level of the higherarchy = Domains (3) Used to be the 5 kingdoms but more recent DNA evidence says that -Bacteria & Archaea (both only Prokaryotes) used to be grouped in the same kingdom but now DNA tells us that Archaea are at least as different from bacteria as they are from eukaryotes
- Below domain, we have... Until we are down to a single organism that can be defined by two names: Genus and species Used to be was ordered based on morphology – more and more on genetics Names and groupings change as our understanding of species grows!!!