evolution of life Flashcards
what are the seven characteristics of life?
- Display order
- Harness and utilize energy
- Reproduce
- Respond to stimuli
- Exhibit homeostasis
- Grow and develop
- Evolve
what defines a cell?
metabolism, reproduction, and composition
define metabolism
• Process through which organisms produce and consume energy to sustain themselves.
why is reproduction required for cells?
All cells arise from previous cells
what are the complex organic molecules that cells are composed of?
• Polymers (large organic molecules): protein, polysaccharides, fats, nucleic acids
Made of monomers: amino acids, monosaccharides, glycerol + fatty acids, nucleotides
what is dehydration synthesis?
• Monomers forming polymers (condensation reactions)
what is hydrolysis?
•
Polymers—> monomers
what is required for living cells to form?
- Formation and aggregation of organic molecules
* A means of reproduction
what stages led to produce simple cells on early earth?
• Chemical and physical processes on early earth may have produced very simple cells through a sequence of stages:
- Abiotic synthesis of small organic molecules
- Joining of these small organic molecules to form macromolecules
- Packaging of molecules into “protocells”
- Origin of self- replicating molecules
what conditions allowed for the abiotic synthesis of small monomers?
• Oparin/Haldane hypothesis
• Reducing atmosphere, higher UV radiation, lightning -> potential for abiotic synthesis of amino acids, sugars, lipids, nucleotide bases
Miller-Urey experiment in support - created a similar environment
what was the miller urey experiment?
- Stanley Miller and Harold Urey conducted lab experiments that showed that the abiotic synthesis of organic molecules in a reducing atmosphere is possible
- But the existence of such an atmosphere is unlikely for the most part
- Instead of forming in the atmosphere, the first organic compounds may have synthesized near submerged volcanoes and deep sea vents
what is the hypothesis of how polymers were formed on early earth?
- RNA monomers produce spontaneously from simple molecules
- Experiment: polymers of organic molecules produced by combining amino acids/nucleotides on hot sand, clay, or rock
- In space:
- In interstellar spaces
- 4.5 yr old chondrite (= meteorite containing chondrules - small silicate particles) from S. Australia with >80 amino acids
what are protocells? why are they important?
the first cells • Group of abiotically produced organic molecules that are surrounded by a membrane or membranelike structure • Primitive cell-like structures • Some properties of life • May have been precursors of cells
how were molecules packaged into protocells?
- Aggregates of abiotic produced vesicles
- Exhibit simple reproduction and metabolism and maintain an internal chemical environment
- Liposomes (small membrane bound droplets) can form when lipids / other organic molecules added to water
- Experiment showed that vesicles form faster in the presence of a type of volcanic clay though to be common 4bya
- Vesicles exhibit simple reproduction and metabolism and maintain an internal chemical environment
what direction does the central dogma go?
DNA - RNA - PROTEIN
how did the first cells make/copy information?
• 1st genes: probably RNA molecules that polymerized abiotically and able to self replicate
• RNA molecules called ribozymes have been found to catalyze many different reactions including:
• Self splicing (Self replication ability that modern cells can’t do)
• Making complementary copies of short stretches of their own sequence or other short pieces of RNA
Early genetic material might have formed an “RNA world”: RNA to DNA to protein
why did proteins become dominant macromolecules?
- Proteins became dominant structural and functions macromolecules of all cells
- Greater diversity
- Much higher rate of catalysis
- DNA is a more stable molecule than RNA and thus evolved as better repository of genetic information
describe early energy harvesting pathways
- Early metabolism was probably based on simple redox reactions
- As part of energy-harnessing reactions, adenosine triphosphate (ATP) became established as the coupling agent that links energy- releasing reactions to those requiring energy
3 hypotheses of origin of life
reducing atmosphere, deep-sea vents, and extraterrestrial origins.
what lead to a rise in oxygen in the atmosphere of early earth?
• Oxygenic photosynthesis led to a rise in oxygen in the atmosphere
vidence for this comes from dat-ing a type of sedimentary rock called banded iron
oxygen had a biological source, specifically derived from a group of photosynthetic prokary-otic cells called cyanobacteria.
what did cyanobacteria lead to?
rise in oxygen in earths atmosphere
how is oxygeneic photosynthesis used today? what has it lead to?
• Astonishingly, although it evolved perhaps as early as 2.5 billion years ago, oxygenic photosynthesis remains the dominant form of photosynthesis and is used by all plants and algae, as well as present-day cyanobacteria
it led to the next remarkable development in the evolution of early life: aerobic respiration
the pathway of oxidative phosphoryla-tion that required O2 for electron transport results in a huge increase in the amount of ATP that can be generated from the breakdown of food molecules
what two features distinguish eukaryotes?
(1) the separation of DNA and cytoplasm by a nuclear envelope, and (2) the presence in the cytoplasm of membrane-bound organelles with specialized functions: mitochondria, chloroplasts, the endoplasmic reticulum (ER), and the Golgi complex, among others
what does the theory of endosymbiosis suggest?
• The theory of endosymbiosis suggests that mitochondria and chloroplasts evolved from ingested prokaryotic cells
The established model of endosymbiosis states that the prokaryotic ancestors of modern mitochondria and chloroplasts were engulfed by larger prokary-otic cells, forming a mutually advantageous relationship called a symbiosis.
