Lecture 1 Species Evolution and Cells Species different definition group of organisms that 1 Are physically similar distinct with stable descent Linneaus in 1700s developed hierarchical system for naming and organizing a Not fixed groups can morph from one species to another species 2 Can interbreed in nature Mayr 1940s only works if sexually reproductive a Biological species concept b c Species Genus Family Order Class Phylum Kingdom Domain If they can breed they are the same species Are species stable Does new life have to come from old life or Spontaneous Generation Life could arise from non living substances Common sense for most of human history Maggots fly larvae from dead meat Horsehair worms from horse hairs Mice from stuff Leave out rags and grains and you can spontaneously generate mice Spontaneous Generation Disproved in 1668 for maggots by Redi 1700 s for other multicellular organisms Put rotting meat in an uncovered jar flies come and maggots appear Put rotting meat in a covered jar flies can t enter so maggots don t appear What about cells Invention of microscope Robert Hooke 1655 called hollow pores in cork cells like little rooms Saw rectangular units in cork plants called them cells Van Leeuwenhoek in 1600 s found single celled organisms which he called animalcules The Cell Theory mid 1800s Every animal appears as a sum of vital units cells each of which bears in itself the complete characteristics of life Ominus cellula e cellula All cells are produced by other cells Modern version 1 All living organisms are made of cells and the products of cells 2 All cells are produced by other cells Spontaneous Generation versus All cells are produced by other cells But are all cells produced by other cells or are some made by spontaneous generation Boil broth soup no cells Wait cells appear and it stinks Spontaneous generation of cells Sterile borth generates cells Broth sterilized by heating sterile broth spoiled broth with microorganisms Sterile borth in sealed flash no organisms appear Seal the top Needham 1745 sterile borth still generated life vs Spallanzani no it didn t Even if Spallanzani was correct does that mean there is no spontaneous generation or that life needs air Pasteur s Experiment 1862 Sterile borth in swan neck flask broth spoils Let the cells in get more cells Experiment breaking off swan neck provides access of microorganisms to flask Control U turn traps dust and microorganisms broth remains sterile All cells come from other cells part 2 of the cell theory Cells divide to produce new cells If life cells always comes from life cells is the character of that life stable Species stable over short term but always Stabilit challenged during 1800 s by Geology Earth not 5 000 years old modern estimate 4 6 billion years Fossil record a old species have vanished E g the Carnivora Amphicyon the bear dog Fossil record challenges species stability a Old species have vanished b New species appear Current species missing from old fossils Ex no Panthera fossils earlier than around 4 million years ago Another kind of evidence new species appearing in new habitats New finish species in new habitat Galapagos Islands New volcanic island rises from the ocean new species appear that are not found on mainland Old species on mainland New species evolved from old species New species on new island are descended from the old species Why would species evolve Darwin Wallace and the theory of Natural Selection 1 There is variation of traits within the population of individuals that make up species 2 Those traits are heritable 3 Certain traits allow better survival of individuals a Better able to reproduce and create the next generation Is the theory of natural selection correct Why is there variation in traits Why are traits heritable and how heritable are they If life and traits depend on cells what the heck are cells Core ceoncepts Species Disproof of spontaneous genration of lfie and species Cells and the cell theory Disproff of s