BIOA01H3 Lecture Notes - Archaea, Cell Theory, Cell Nucleus

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Published on 24 Apr 2012
Biological Sciences
BIOA01H3F- Unifying Principles
Lecture 2
Biology: bio- life; -logy: study of
Biology became very progressive after Watson and Crick discovered the structure of
DNA in 1953
Embryos of chicken, frogs, and humans look basically the same very early on.
All species depend on other organisms
What is life?
In order for an organism to be alive it has to be able to metabolize (cellular respiration
and photosynthesis; making energy from the “food” that the organism takes in),
reproduce, have cells, be able to react to its surroundings, be able to grow, maintain
homeostasis, adapt to environment.
Living organisms consist of cells
All cell membranes are basically the same; all have the same function to separate the
outside of the cell from the interior
Cell theory
1. Cells are the basic units of life
2. All organisms are made up of cells
3. The cells always come from pre-existing cells
Heritable genetic information is passed from generation to generation
Info is held in the nucleic acid called DNA
This information get translated into proteins
Differences in the expression of proteins is what makes diversity in organisms
Living organisms use energy and matter from surroundings for metabolism
Living organisms respond to environmental change leading to diversity
2.5 million species discovered
Estimated between 5-200 million species
Most successful group is insects; half of species discovered are insects
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Diversity intrigued him
He wondered why there were different types of similar species
Theory of Evolution through Natural Selection
Unity of Life
All organisms
1. Are cellular
2. Based on water
3. Consist of 6 elements
4. similar macromolecules
5. Have RNA and DNA from same nucleotides
6. Genome composed of RNA or DNA (replication)
7. Have ribosomes acting as sites of protein synthesis
8. Undergo rapid metabolic reaction catalyzed by proteins
9. Osmotically active membranes of similar structure
10. Use formation/hydrolysis of ATP for energy flow
With all of these similarities, it is assumed that there is a common ancestor
Lecture 3
What is meant by the "Tree of Life"?
modern classifications is phylogenetic based on:
-obvious similarities
-evolutionary relationships
•still a 'work in progress'
•active debate about Kingdoms and lower levels of taxonomic hierarchy
archaea bacteria do not depend on photosynthesis to survive like most organisms
•they depend on chemical energy instead of light energy
What does the "Tree of Life" tell us?
can tell us the history of life on Earth
•can be considered a web of life since there are so many connections between
•at least 5 mass extinctions (90% of the Earth's species went extinct)
How do biologists organize the world?
1) by naming the organisms
2) by organizing organisms by evolutionary relationships
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3) by looking at where organisms live (e.g. ecological hierarchy)
4) by looking at what organisms do (e.g. food chains/food webs)
Emergent Properties of Life
unique characteristics associated with one level of organization that are not seen at
lower levels
the 'whole' is greater than the 'sum of its parts'
•DNA molecules are not alive, neither are proteins, lipids or carbs
•life emerges from inert matter because of unique interaction between
Lecture 3 (added notes)
Tree of Life
All of the living organisms are classified in groups
There are three domains and six kingdoms
The way they are sorted is phylogenetic, meaning that they are classified according to
their obvious similarities between species (evolutionary relationships)
the ancestor of all life is believed to be soft-bodied and microscopic
the tree of life is still a work in progress and is changing constantly
the domains in the tree of life have only been around for about 30 years
fungi are the most closely related to animals in the eukarya domain of the tree of life
in the 1970s, the archaea bacteria were discovered
Archaea bacteria live in areas of high temperature, low pressure, no light, etc.
This changed the perspective of life because it was always thought that light had to
depend on photosynthesis
The archaea bacteria are capable to use energy stored from chemical bonds to create
sugars just like plants do with light energy
Scientists believe that there are over 10 million species on Earth, but less than 2 million
have actually been discovered
The tree of life can help to tell us the history
Since there are so many relations between organisms, the tree of life can be seen as a
web of life
There have been 5 major extinction periods (90% of species were wiped out)
The earth could be going through a mass extinction now
This is the first time that it was actually caused by a biological organism
All species have their own species name
Every ecosystem food chain/web starts off with a producer
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