Biology 1202 Test 1 How did life begin 11 million species on planet earth earth is 4 6 billion years old life arose by change chemical reactions take place life started with 1 species 4 billion years ago and now there s 11 million species hypothesis about how life changed to become 11 million species today how many cells make up the body Trillions o evolution is the change that took place o theory based on scientific evidence o because of chemical evolution we are multicellular eukaryotic 50 trillion microbes living in your body all living things on the planet are related 200 thousand years ago Homo sapiens before animals came to land they were fish no such thing as a mammal a million years ago A few centuries ago 1 People thought new living things appeared all the time Hypothesis life spontaneously appears o Spontaneous generation theory refuted by Louis Pasteur in mid 1800s Broth in flask is boiled to kill pre existing microorganisms As broth cools condensing water collects sealing the mouth of the flask Unless air could flow into the tube spontaneous generation could not evolve If neck is later broken off outside air can carry microorganisms into broth Theory of spontaneous generation is wrong Conditions on Early Earth Atmosphere today o 1 O2 and O3 were missing oxygen and ozone similar to Jupiter oxygen comes from photosynthesis but there were no trees plants at this time so there was no oxygen or ozone o 2 No free oxygen o 3 Frequent storms with lots of lightning o 4 Frequent volcanic eruptions o 5 Frequent meteor impacts o UV light from the sun o No ozone layer Chemical evolution all results from reactions o Chemical molecules created trillions of bonds and reacted forming new substance Before we had enzymes to catalyze reactions Earth before Life Arose o 1 Earth is about 4 6 billion years old o we know this because of radiometric dating of meteorites and moon rocks o life changed the shape of rocks o tectonic movements subsiding underneath earth o hard to find rocks older than 4 billion years ago o 2 Life arose about 3 8 billion years ago o we know because of chemical traces in rocks 3 8 billion years old o fossil bacteria in rocks 3 5 billion years old o no spontaneous generation now but must have happened then The experiment of Miller and Urey o Set out to try to create life in a laboratory o Water turned a murky sugar color o Failed o Took a hundred million years to create life on earth with conditions similar to this experiment so the experiment would take millions of years fail o 1 in a trillion chance that it would work How to assemble a living thing 1 Accumulation of organic molecules 2 Need something to catalyze reactions enzymes 3 Need something to reproduce from stored genetic info DNA 4 Need something to separate the living thing from the outside environment The chicken or the Egg Now DNA RNA Protein central dogma o Need proteins to synthesize more DNA o Need DNA helicase DNA polymerase and DNA ligase Came from RNA RNA came first So how did earliest cells do it Ribozymes o Catalyze chemical reactions of the RNA o RNA molecule that can catalyze reactions especially those involved in synthesis and processing of RNA itself 1 Conclusion earliest cells used RNA to store info 2 Ribozymes to catalyze reactions Microspheres as Proto cells membranes with phospholipid bilayer all living things just add fat and protein to water then shake the cells that are formed and live eventually evolve over time water elements energy prebiotic soup amino acids nucleotides lipids sugars Microsphere like proto cells surrounding more complex organic molecules like RNA carbohydrates proteins and lipids First prokaryotes common ancestor of all living things Systematics Seeking Order Amidst Diversity Most bacteria do not cause harm but are beneficial to our health well being Symbiosis 2 species living closely together symbiotic relationship o parasidic one species benefits o mutual both species benefit ex ecoli Taxonomy branch of biology concerned with naming and classifying the diverse forms of life on our planet Homo sapiens all people homo genus sapiens species 385 million years ago fish came to land Humans and fish have a common ancestor Taxonomy there are many ways that things may be grouped Now there are 3 domains of life the 3 domains and the kingdoms with in them each have observably different attributes that define them bacteria archaea and eukarya Dr Woesse sequenced ribosomal RNA of individual species across these 3 domains and they all share RNA Eukarya humans Animals Fungi Plants Protists Nodes at common ancestors There s a common ancestor to all living things bacteria archaea eukarya Domain Kingdom Cell Type Cell Number Nutrition Method Archaea 3 prokaryotic unicellular absorption photosynthesis Bacteria 13 15 prokaryotic unicellular absorption photosynthesis Eukarya Protista eukaryotic unicellular absorp photosynthesis ingestion Fungi eukaryotic multicellular absorption Plantae eukaryotic Multicellular photosynthesis Animalia eukaryotic multicellular ingestion Eukaryotes exist sexually and asexually Taxonomic categories 1 The organization of taxonomic grouping arranges organisms in sets o 11 million species can be divided into eukaryote and prokaryote 2 Each set is then grouped with other sets into a larger set 3 The major taxonomic categories from most inclusive biggest set 11 million to least inclusive smallest set are o domain kingdom phylum class order family genus species a the category genus groups together closely related organisms which may or may not interbreed and produce hybrids b this separation based on interbreeding defines the category species biological species concept o dog dog dog o cat cat cat o dog cat nothing a species is the biological group which includes all the organisms which are or have the potential for interbreeding biological species concept b many species were originally distinguished by morphology if 2 organisms look alike they must be the same species c however biological species are based on the ability to reproduce IN NATURE individuals may look different but can reproduce and therefore are the same species like dogs DNA sequence determines what the species is related to Historically taxonomy is an inexact process organisms which were once played together in a certain classification group have been separated when new or better evidence is uncovered DNA sequencing of genomes for example relatedness can be determined by comparing DNA
View Full Document
Unlocking...