What is the sequence of stages thought to have allowed the earliest cells to form?
1. abiotic synthesis of small organic molecules
2. Polymerization of these molecules
3. Packaging into "protobiotns"
4. Rise of self-replicating molecules that allowed inheritance
How old is the earth according to scientific evidence?
4.6 billion years
How are the earliest organic molecules thought to have formed?
contained water vapor and many chemicals released by volcanic eruptions; nitrogen, nitrogen oxides, carbon dioxide, methane, ammonia, hydrogen, hydrogen sulfide
Can these molecules spontaneously polymerize?
small organic molecules polymerize when they are concentrated on hot sand, clay or rock; replication and metabolism are key properties of life
are aggregates of abiotically produced molecules surrounded by a membrane or membrane-like structure; first genetic material was probably RNA, ribosymes have been found to catalyze many different reactions
mostly from sedimentary rocks; information on evolution over billions of years
How are rocks and fossils dated?
absolute ages of fossils are determined through radiometric dating;
each isotope has a half-life, the time required for half the parent isotope to decay (parent->daughter isotope)
When did the earliest prokaryotes appear?
stromatolites; rocklike structures made of layers of bacteria and sediment; 3.5 billion years ago (only prokaryotes on earth: 3.5-2.1 billion years)
What did the earliest prokaryotes contribute?
When did oxygen start to accumulate?
oxygenic photosynthesis: 2.7-2.3 billion years ago
How old are eukaryotic cells?
oldest fossils: 2.1 billion years
How are eukaryotic thought to have arisen?
endosymbiosis: proposes that mitochondria and plastids were formerly small prokaryotes living within larger host cells (explains diversity in algal groups);
evidence includes: similarities in inner membrane structure and function, both have their own circular DNA
What is a chimera?
Greek mythology: part lion, part goat, part serpent;
joining together of parts of organisms into one; applied to endosymbiosis
What is the scientific explanation for the origins of multicellularity?
multicellular organisms evolved about 1.2 billion years ago;
the first multicellular organisms were colonies of autonomously replicating cells
earth's continents are not fixed, they drift on great plates, often the plates side along other plates (pulling and pushing), important geological processes occur at boundaries
many animal phyla diverged at 1billion-700million years ago; major phyla of animals appeared at the first 20million years of the Cambrian period
supercontinent; late Paleozoic era, breakup during mesozoic era, explains similarity of fossils in South America and Africa
Mass extinction events
5 mass extinction events; more than 50% of earth's species became extinct;
sixth human-caused mass extinction is likely to occur
What is adaptive radiation?
is the evolution of diversity adapted to species from a common ancestor upon introduction to new environmental opportunities
How did this phenomenon contribute to the flora and fauna of the Hawaiian Islands?
species are very closely related to each other (Ie. silversword alliance) but are different in appearance/characteristic due to the various environments of the islands