BIOL 1500 Chapter Notes - Chapter 13: Symbiogenesis, Archaea, Eukaryote

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March 15th, 2016. BIOL1500 Unit 9 (286-308)
Biodiversity and Classification
13.1 Biological Classification
oHow many species exist? Scientists refer to the variety within and amongst living
species as biodiversity, this has been studied to help understand evolutionary
origins of different organisms and their role in healthy biological systems. In
general, a species is a group of individuals that regularly breed together and are
generally distinct from other species in appearance or behaviour. Systematists are
scientists who specialize in describing/categorizing particular groups or
organisms, less than 20% of the total species around are known to scientists.
oKingdoms and Domains: domains are 3 large groups unified by cell structure. The
domains are bacteria, archaea and eukarya. Within each of these domains, there
is a kingdom. Kingdom names are: plantae (multicellular, make their own food),
Animalia (rely on other organisms for food, mobile at one part of time), fungi
(reproduce by spores, body made up of hyphae), Protista single cell), bacteria
(prokaryotic) and archaea (similar to bacteria) Due to sharing of an ancestor, all
species have commonality in DNA, mutations occurred independently.
13.2 The Diversity of Life
oThe Domains Bacteria and Archaea: most ancient fossilized cells are similar in
external appearance to modern bacteria and archaea. Both are prokaryotes which
means they do not contain a nucleus, which provides a membrane bound separate
compartment for the DNA. They lack internal structures bounded by membranes
such as mitochondria and chloroplasts. Most prokaryotes are unicellular (each cell
is an individual organism) hundreds of times smaller than cells that make up our
body. Since they are so small, they are referred to as microbes and studies by
microbiologists. Some bacteria can form endospores which are resistant
structures containing DNA, ribosomes and a little bit of cytoplasm, they are
resistant to extreme temperatures, drying, radiation and the vacuum of outer space
and can generate new living cells after they form. Cyanobacteria do not need
another organism to survive, they can manufacture all components of life from
sunlight, water and air. Bacterial defense against the viruses that can attack them
has resulted in another class of valuable molecules called restriction enzymes
which are proteins that can chop DNA at a specific sequence site and interfere
with the growth of the virus.
oThe origin of the Domain Eukarya: third domain of life, contains all of the
organisms that keep their genetic material within a nucleus inside their cells.
Internal membranes may have segregated the genetic material into a primitive
nucleus and created channels for translating, rearranging and packaging proteins.
According to the endo-symbiotic theory the mitochondria and chloroplasts found
in eukaryotic cells appear to have descended from bacteria that took up residence
in larger primitive eukaryotes. Mutually beneficial symbiosis and the cells
became tied together.
oKingdom Protista: made up of simplest known eukaryotes most are single celled
but have some enormous multi cellular. Most members remain unknown.
Scientists disagree about the phyla (groups below the kingdom) are within. Plant-
like protists that make food via photosynthesis are called algae, made up of
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