Cycle 10 - Diversity of Life Flashcards
Approximately how old is the Earth?
4.6 bya
How can the age of Earth be determined?
Radiometric dating - rate of rock decay
What do the four essential macromolecules tell us about the first cells?
- nucleic acid, proteins, carbohydrates, lipids
- first cells must have some of these essential macromolecules so simpler forms of them must have existed before cells
- abiotic synthesis
What did the atmosphere look like 4 bya? What molecules were present?
hot surface = water vapour
H2, CH4, CO2, NH3
almost complete absence of O2
Why was the early atmosphere considered a reducing atmosphere? What does this indicate for the evolution of the first cell?
RA = large concentration of H2, NH3, CH4 etc
so large complex ORGANIC molecules could form to create macromolecules because of the present molecules bonding capabilities
What is today’s atmosphere classified as? How does this compare with reducing atmosphere?
OXIDIZING ATMOSPHERE
- large complex organic molecules cannot form because large presence of oxygen = oxygen react = everything reduced to water
What is the impact of the Ozone layer (O3) in the young and present atmosphere?
Present: ozone layer present
Young: ozone layer not present = UV light and lightening able to provide energy for macromolecule creating reactions why reaching lower atmosphere
What was the Miller Urey experiment? What did it prove?
reducing atmosphere apparatus
- gaseous inorganic molecules sparked with electrode energy and boiling water for early water cycle
- showed that organic molecules did form (amino acids, fatty acids, sugars, phospholipids)
What is the clay hypothesis?
clay has a thin layer of minerals, a charged surface allowing for the formation of short polymers of proteins and nucleic acids prior to enzymes in the early Earth
What environment must have the first cells originate from?
ocean floor at the sites of alkaline hydrothermal vents
Why do scientists believe alkaline hydrothermal vents are where first cells originated?
- water temperature 100ºC-150ºC
- rich in molecules
- strongly alkaline
- calcium carbonate chimneys that are honeycombed with microscopic pores that water can move through
What are the seven common features for all forms of life on earth?
- Cells with lipid bilayer membrane
- DNA genetic system
- Central Dogma
- Ribosomes for protein assembly
- Proteins for as the major structural and catalytic molecule
- ATP chemical energy currency
- Common pathways of energy transformation
as well as ~ 50 genes
What are the two majoy distinctions between eukaryores and prokaryotes?
- seperation of DNA and cytoplasm by a nuclear envelope
- membrane-bound organelles (mitochondria, chloroplasts, EF, golgi complex
Why was cyanobacteria essential to Earth’s development/species?
photosythetic bacteria created oxygen so aerobic species evolved and greater amounts of ATP could be generated for breaking down glucose molecules (step towards eukaryotes)
What is the endosymbiosis model for mitochondria and chloroplasts?
Prokaryotic ancestors of mitochondria and chloroplasts were engulfed by large prokaryotic cells that formed a symbiotic relationship between them and the host cell
What evidence is available for mitochondria and chloroplasts to derive from prokaryotic bacteria?
- shape and size are similar to prokaryotic cell
- cells cannot synthesize mitochondria or chloroplast, instead they divide from preexisting in through binary fission
- contain their own circular DNA
- contain ribosomes and tRNA for transcription and translation
- Electron transport chains and ATP synthase for chemical energy
- Sequencing analysis shows chloroplasts are similar to cyanobacteria and mitochondria is similar to heterotrophic bacteria
What does the fact that chloroplasts are only in plants tell us about the endosymbiosis timeline for chloroplasts and mitochondria?
mitochondria first, chloroplasts second
What is the hypothesis for eukaryotes developing membranes around organelles?
infolding plasma membrane surrounded nucleus and formed ER
What is vertical gene transfer?
inheritance from one generation to the next
What is horizontal gene transfer? What is an example of this?
movement of genetic material between organisms other than by descent
ex. bacterial endosymbiosis
When the mitochondria/chloroplasts fused, how were their genetic material integrated?
- redundant genes were lost
- many genes in the proto-mitochondrion and protons-chloroplast were relocated to nucleus
What is strata? What is their importance in fossils?
layer of sediment of different colours, mineral composition that can show fossils from lowest/oldest to highest/newest
What are the characteristics of LUCA?
- cellular
- prokaryotic and likely bacterial
- anaerobic (doesn’t need oxygen b/c oxygen was scarce)
- autotrophic (synthesize sugars using chemical energy from vent for food)
What were the evolved characteristics from bacteria to archaea?
cell membrane/cell wall
