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BIOA01H3F Lecture Notes.docx

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Biological Sciences
Mary Olaveson

BIOA01H3F- Unifying Principles Lecture 2 Introduction 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 Darwin 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 organisms 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 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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