evolution of life

Question 1

what are the seven characteristics of life?

Answer 1

1. Display order
2. Harness and utilize energy
3. Reproduce
4. Respond to stimuli
5. Exhibit homeostasis
6. Grow and develop
7. Evolve

Question 2

what defines a cell?

Answer 2

metabolism, reproduction, and composition

Question 3

define metabolism

Answer 3

• Process through which organisms produce and consume energy to sustain themselves.

Question 4

why is reproduction required for cells?

Answer 4

All cells arise from previous cells

Question 5

what are the complex organic molecules that cells are composed of?

Answer 5

• Polymers (large organic molecules): protein, polysaccharides, fats, nucleic acids
Made of monomers: amino acids, monosaccharides, glycerol + fatty acids, nucleotides

Question 6

what is dehydration synthesis?

Answer 6

• Monomers forming polymers (condensation reactions)

Question 7

what is hydrolysis?

Answer 7

•

Polymers—> monomers

Question 8

what is required for living cells to form?

Answer 8

• Formation and aggregation of organic molecules

* A means of reproduction

Question 9

what stages led to produce simple cells on early earth?

Answer 9

• Chemical and physical processes on early earth may have produced very simple cells through a sequence of stages:

1. Abiotic synthesis of small organic molecules
2. Joining of these small organic molecules to form macromolecules
3. Packaging of molecules into “protocells”
4. Origin of self- replicating molecules

Question 10

what conditions allowed for the abiotic synthesis of small monomers?

Answer 10

• 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

Question 11

what was the miller urey experiment?

Answer 11

• 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

Question 12

what is the hypothesis of how polymers were formed on early earth?

Answer 12

• 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

Question 13

what are protocells? why are they important?

Answer 13

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

Question 14

how were molecules packaged into protocells?

Answer 14

• 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

Question 15

what direction does the central dogma go?

Answer 15

DNA - RNA - PROTEIN

Question 16

how did the first cells make/copy information?

Answer 16

• 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

Question 17

why did proteins become dominant macromolecules?

Answer 17

• 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

Question 18

describe early energy harvesting pathways

Answer 18

• 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

Question 19

3 hypotheses of origin of life

Answer 19

reducing atmosphere, deep-sea vents, and extraterrestrial origins.

Question 20

what lead to a rise in oxygen in the atmosphere of early earth?

Answer 20

• 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.

Question 21

what did cyanobacteria lead to?

Answer 21

rise in oxygen in earths atmosphere

Question 22

how is oxygeneic photosynthesis used today? what has it lead to?

Answer 22

• 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

Question 23

what two features distinguish eukaryotes?

Answer 23

(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

Question 24

what does the theory of endosymbiosis suggest?

Answer 24

• 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.

Question 25

what six lines of evidence suggest the theory of symbiosis is true?

Answer 25

1. Morphology. The shape and size of both mitochondria and chloroplasts are similar to those of prokaryotic cells
2. Reproduction. A cell cannot synthesize a mitochondrion or a chloroplast. Both chloroplasts and mitochondria divide by binary fission, which is how prokaryotic cells divide
   Genetic information. If the ancestors of mitochondria and chloroplasts were free-living cells, then these organelles should contain their own DNA.
3. Transcription and translation. Both chloroplasts and mitochondria contain a complete transcription and transla-tional machinery
   Electron transport. Similar to free-living prokaryotic cells, both mitochondria and chloroplasts have electron transport chains and the enzyme ATP synthase
   Sequence analysis Sequencing of the genes that encode the RNA component of the ribosome (ribosomal RNA or rRNA) firmly establishes that these organelles belong on the bacterial branch of the tree of life
   The sequence of chloroplast rRNA most closely matches that of cya-nobacteria, and the sequence of mitochondrial rRNA is most similar to that of heterotrophic bacteria

Question 26

how did endosymbiosis occur?

Answer 26

only plants and algae contain both mito-chondria and chloroplasts. This fact suggests that endosymbiosis occurred in stages (see Figure 21.17), with the event leading to the evolution of mito-chondria occurring first.