Biol165 - introduction pages.pdf

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Published on 16 Apr 2013
School
University of Waterloo
Department
Biology
Course
BIOL165
Biol 165: Diversity of Life
!
1. Introduction
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 ~
200mybp/0.2bybp
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
molecules).
DNA replaces RNA as coding molecule (DNA to RNA to
Protein).
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
dominant.
Photosynthetic cyanobacteria evolved, and introduced more
elevated levels of O2 as a byproduct of their photosynthetic
processes and activity – oxygenating and aerobes became
dominant.
Eukaryotes evolved ~ 1.5bybp, including photosynthetic
plants – this probably contributed to the continued increase of
O2 in the atmosphere.
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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
described.
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
amount.
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
Australian Ant.
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.
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Document Summary

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.

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