Biol 165: Diversity of Life
• The Earth is 4.5 byo
• Early cellular life at ~ 4bybp
• Prokaryotes evolved 3.5 bybp
o they were the only form of life for ~ 2byrs
• Eukaryotes evolved ~ 1.5 bybp
o multi-cellular organism ~ 0.57 bybp/570 kybp
o plants colonized ~ 0.45 bybp
o Large animals like Dinosaurs evolved ~
o First Modern Humans appeared ~ 200 kybp
Hypothesis on Origin of Life on Earth
• sterile Earth
• prebiotic synthesis of organic molecules
• polymerization of nucleotides to for RNAs
• self-replicating RNAs
• inclusion of RNA in simple lipoprotein vesicles
• early proto-cellular life (RNA as coding and catalytic
• DNA replaces RNA as coding molecule (DNA to RNA to
• Modern cellular life
• This process admittedly requires big jumps from self
replicating RNA that codes for nothing to RNA that codes for
proteins that catalyze the replication of RNA.
Origins of Free Oxygen
• Earth lost its primary atmosphere of H2 and He early.
• The atmosphere developed from volcanic gases that were
reduced by anaerobes and chemotrophs, which were
• Photosynthetic cyanobacteria evolved, and introduced more
elevated levels of O2 as a byproduct of their photosynthetic
processes and activity – oxygenating and aerobes became
• Eukaryotes evolved ~ 1.5bybp, including photosynthetic
plants – this probably contributed to the continued increase of
O2 in the atmosphere.
Biol 165: Diversity of Life
Numerical Breakdown of Species.
Total # of species known to science – 1,740,000
• Insects – 1 mil
• Animals - 365k
• Plants – 321k
• Protists – 65k
• Fungi – 75k
• Prokaryotes – 4.8 mil
There is great diversity, and many undiscovered species still remaining
on Earth. Estimated range from 10-20 million to upwards of 100
million undiscovered species. Only 1.5 mil species have been
Variation in Amount of DNA
• Whist Fern, has largest amount of DNA
• bacteria, least about of DNA
• Protozoa and eukaryotic algae have greatest variation in DNA
• polyploidy: whole replication of a chromosome (or many).
• humans have 46 chromosomes – it had been thought that
there was 48, until the early 1950s. This is referred to as the
Rule of 48.
o human chromosome # 2 is the result of a fusion of 2
chromosomes – the earlier form of 48 chromosomes
still exists in other great apes.
o Robertsonian fussion: fusion of chromosomes.
• Muntiacus vaginalis, lowest # of chromosomes in vertebrates
at 2n=6 or 7.
• For invertebrates, the lowest # of chromosomes is 2n=2 of an
• Xanthisma gracilis, has the least # of chromosomes of
Vascular Plants at 2n=4.
• Ophioglossum reticulatum (Adders Tongue Fern) has most #
of chromosomes at 2n=1260 – likely the result of excessive
polyploidy, which is a common occurrence in more primitive
• Systems of Classification are built from the bottom up.
Biol 165: diversity of life: introduction, this process admittedly requires big jumps from self replicating rna that codes for nothing to rna that codes for proteins that catalyze the replication of rna. Total # of species known to science 1,740,000: insects 1 mil, animals - 365k, plants 321k, protists 65k, fungi 75k, prokaryotes 4. 8 mil. There is great diversity, and many undiscovered species still remaining on earth. Estimated range from 10-20 million to upwards of 100 million undiscovered species. Australian ant: for invertebrates, the lowest # of chromosomes is 2n=2 of an, xanthisma gracilis, has the least # of chromosomes of. Vascular plants at 2n=4: ophioglossum reticulatum (adders tongue fern) has most # of chromosomes at 2n=1260 likely the result of excessive polyploidy, which is a common occurrence in more primitive plants. Classification schemes: systems of classification are built from the bottom up.