4. 1. The earth was formed ~4.5 billion years ago
2. It took ~500 million years for the crust to solidify.
3. The oldest fossils of microorganisms
• 3.5 billion years old,
• embedded in rocks in western Australia
3a. Prokaryotes dominated from 3.5 to 2 billion years ago.
- During this time, the first divergence occurred:
Bacteria and Archae
6. Fossilized evidence of bacteria
Stromatolites are fossilized bacterial mats. Many fossils
of prokaryotes are found in layers that make up the
prokaryotic mats.
12. 4. Oxygen began accumulating in the atmosphere about 2.7
billion years ago.
a. Cyanobacteria are photosynthetic prokaryotes that are
still present today produced oxygen.
13. Banded iron formations are evidence of the age of oxygenic
photosynthesis – approximately 2 BYA in photo
17. Eukaryotic Origins
• A. Invagination of plasma membrane
• B. Endosymbiosis
– Symbiosis : An ecological relationship between
organisms of 2 different species that live
together in direct contact.
– How did this get started?
• prey or parasite
18. Evidence
• modern-day endosymbiotic relationships
– common among protists
• similarity between eubacteria & the
chloroplasts & mitochondria of eukaryotes
– size
– inner membrane systems, enzymes, electron transport
systems
– reproduction resembles binary fission
– circular DNA
19.
20.
21. Note the presence of
two types of cells
(photosynthetic and
hold fast) – evidence
of specialization of
cells functions, that
are important for
development of
multicellular organisms
36. • Laboratory experiments have demonstrated
that RNA sequences can evolve in abiotic
conditions.
• RNA molecules have both a genotype
(nucleotide sequence) and a phenotype (three
dimensional shape) that interacts with
surrounding molecules.
• Under particular conditions, some RNA
sequences are more stable and replicate faster
and with fewer errors than other sequences.
– Occasional copying errors create mutations and
selection screens these mutations for the most
stable or best at self-replication.
41. This 4.5 billion-year-old rock, labeled meteorite ALH84001, is believed to have once been
a part of Mars and to contain fossil evidence that primitive life may have existed on Mars
more than 3.6 billion years ago. The rock is a portion of a meteorite that was dislodged
from Mars by a huge impact about 16 million years ago and that fell to Earth in Antarctica
13,000 years ago. The meteorite was found in Allan Hills ice field, Antarctica, by an
annual expedition of the National Science Foundation's Antarctic Meteorite Program in
1984. It is preserved at the Johnson Space Center's Meteorite Processing Laboratory in
Houston.
Model for origin of eukaryotes
(A) endomembrane system of eukaryotes may have evolved from specialized infoldings of plasma membrane of ancestral prokaryotes
(B) chloroplasts are descendants of photosynthetic prokaryotes, probably cyanobacteria
- proposed ancestors of mitochondria were endosymbiotic bacteria that were aerobic heterotrophs
a. may have first gained entry into larger cells as undigested prey or internal parasites
Be a good skeptic! Where’s the evidence?
size: similar to prokaryotes
inner membranes of chloroplasts & mitochondria may have been derived from the plasma membranes of endosymbiotic prokaryotes, having several of the same enzymes and electron transport systems that resemble those found on the plasma membranes of modern prokaryotes
mitochondria and chloroplasts reproduce by splitting process reminiscent of binary fission in bacteria
Based on molecular tools comparing genetic composition, nucleic acid sequences and percentage composition, DNA in organelles separate from genomic DNA & its composition more like that of prokaryotes than eukaroytes.