III Acquiring the Characteristics of Life C Metabolic

III. Acquiring the Characteristics of Life C. Metabolic Pathways - Solution - reverse evolution A B C D E

III. Acquiring the Characteristics of Life C. Metabolic Pathways - Solution - reverse evolution suppose E is a useful molecule, initially available in the env. E

III. Acquiring the Characteristics of Life C. Metabolic Pathways - Solution - reverse evolution suppose E is a useful molecule, initially available in the env. As protocells gobble it up, the concentration drops. E

III. Acquiring the Characteristics of Life C. Metabolic Pathways - Solution - reverse evolution D Anything that can absorb something else (D) and MAKE E is at a selective advantage. . . E

III. Acquiring the Characteristics of Life C. Metabolic Pathways - Solution - reverse evolution D Anything that can absorb something else (D) and MAKE E is at a selective advantage. . . but over time, D may drop in concentration. . . E

III. Acquiring the Characteristics of Life C. Metabolic Pathways - Solution - reverse evolution C D So, anything that can absorb C and then make D and E will be selected for. . . E

III. Acquiring the Characteristics of Life C. Metabolic Pathways - Solution - reverse evolution A B C D and so on until a complete pathway evolves. E

III. Acquiring the Characteristics of Life D. Genetic Systems - conundrum. . . which came first, DNA or the proteins they encode? DNA RNA (m, r, t) protein

III. Acquiring the Characteristics of Life D. Genetic Systems - conundrum. . . which came first, DNA or the proteins they encode? DNA stores info, but proteins are the metabolic catalysts. . . RNA (m, r, t) protein

III. Acquiring the Characteristics of Life D. Genetic Systems - conundrum. . . which came first, DNA or the proteins they encode? - Ribozymes info storage AND cataylic ability

III. Acquiring the Characteristics of Life D. Genetic Systems - conundrum. . . which came first, DNA or the proteins they encode? - Ribozymes - Self replicating molecules - three stage hypothesis

Stage 1: Self-replicating RNA evolves RNA

Stage 1: Self-replicating RNA evolves RNA m- , r- , and t- RNA PROTEINS (REPLICATION ENZYMES) Stage 2: RNA molecules interact to produce proteins. . . if these proteins assist replication (enzymes), then THIS RNA will have a selective (replication/reproductive) advantage. . . chemical selection.

DNA m- , r- , and t- RNA PROTEINS (REPLICATION ENZYMES) Stage 3: Mutations create new proteins that read RNA and make DNA; existing replication enzymes replicate the DNA and transcribe RNA.

Can this happen? Are their organisms that read DNA and make RNA?

Can this happen? Are their organisms that read DNA and make RNA? yes - retroviruses. .

DNA m- , r- , and t- RNA Already have enzymes that can make RNA. . . PROTEINS (REPLICATION ENZYMES) Stage 3: Mutations create new proteins that read RNA and make DNA; existing replication enzymes replicate the DNA and transcribe RNA.

DNA This is adaptive because the two-step process is more productive, and DNA is more stable (less prone to mutation). m- , r- , and t- RNA PROTEINS (REPLICATION ENZYMES) Stage 4: Mutations create new proteins that replicate the DNA instead of replicating the RNA. . .

DNA m- , r- , and t- RNA This is adaptive because the two-step process is more productive, and DNA is more stable (less prone to mutation). And that's the system we have today. . PROTEINS (REPLICATION ENZYMES) Stage 4: Mutations create new proteins that replicate the DNA instead of replicating the RNA. . .

IV. Early Life - the first cells were probably heterotrophs that simply absorbed nutrients and ATP from the environment. - as these substances became rare, there was strong selection for cells that could manufacture their own energy storage molecules. - the most primitive cells are methanogens, but these are NOT the oldest fossils.

IV. Early Life - the second type of cells were probably like green-sulphur bacteria, which used H 2 S as an electron donor, in the presence of sunlight, to photosynthesize.

IV. Early Life - the evolution of oxygenic photosynthesis was MAJOR. It allowed life to exploit more habitats, and it produced a powerful oxidating agent! These stromatolites, which date to > 3 bya are microbial communities.

IV. Early Life - about 2. 3 -1. 8 bya, the concentration of oxygen began to increase in the ocean and oxidize eroded materials minerals. . . deposited as 'banded iron formations'.

IV. Early Life - 2. 0 -1. 7 bya - evolution of eukaryotes. . endosymbiosis.

IV. Early Life "We share half our genes with the banana. Robert May is a UK Chief Scientist. In New Scientist magazine (July 1, 2000) on page 5 he stated, "We share half our genes with the banana. " One can only guess (with a fertile imagination) what the common ancestor between people and bananas looked like! In addition, there are fish that have 40% the same DNA as people, but hopefully no evolutionist would claim that the fish are 40% human - or people are half bananas. " From Ken Forbes, youngearth@comcast. net.

"We share half our genes with the banana. Robert May is a UK Chief Scientist. In New Scientist magazine (July 1, 2000) on page 5 he stated, "We share half our genes with the banana. " One can only guess (with a fertile imagination) what the common ancestor between people and bananas looked like! In addition, there are fish that have 40% the same DNA as people, but hopefully no evolutionist would claim that the fish are 40% human - or people are half bananas. " FRom Ken forbes, youngearth@comcast. net. uh, no; we evolutionists wouldn't claim that. So why represent the argument like this, as IF that's the only interpretation?

IV. Early Life - 2. 0 -1. 7 bya - evolution of eukaryotes. . endosymbiosis.

IV. Early Life - 2. 0 -1. 7 bya - evolution of eukaryotes. . endosymbiosis. 2, 000, 000 years. 1/2 of life's history. . . common ancestor - ancestral eukaryotic cells. . niether banana nor wade-like. .

IV. Early Life Eukaryote Characteristics - membrane bound nucleus - organelles - sexual reproduction You see, the two major themes in biology are diversity AND unity. Although we have so many different species and life forms, at a fundamental cellular level they all work in THE SAME BASIC WAY. And evolution explains both this similarity and diversity at the same time. . .

IV. Early Life Origins infolding of membrane

IV. Early Life B. Origins endosymbiosis - mitochondria and chloroplasts (Margulis - 1970's)

IV. Early Life Relationships among life forms - deep ancestry and the last "concestor" A "top-heavy" view, suggesting greater diversity among eukaryotes. . .

IV. Early Life Woese - r-RNA analyses reveal a deep divide within the bacteria, and greater genetic diversity among both clades of "bacteria' than among eukarya