Chapter 1 Biology and Cell Theory What Does it Mean to Say Something is Alive What Does it Mean to Say Something is Alive Get in your groups and discuss this question Try to list 5 characteristics of every life form What Does It Mean to Say That Something Is Alive All living organisms share five fundamental characteristics All organisms acquire and use energy All organisms are made up of membrane bound cells All organisms process hereditary information encoded in genes as well as information from the environment All organisms are capable of reproduction Populations of organisms are continually evolving The Cell Theory In the late 1660s Robert Hooke and Anton van Leeuwenhoek were the first to observe cells using a crude microscope By the early 1800 s enough data accumulated for a biologist to claim that organisms consist of cells A cell is a Where do cells come from The Cell Theory At the time most biologists believed that They put forth an alternative hypothesis cells do not spring to life spontaneously but are produced only when preexisting cells grow and divide The states that All organisms are made of pattern All cells come from process Doing Biology The Nature of Science All scientists ask questions that can be answered by Science is about formulating hypotheses and finding evidence that supports or conflicts with those hypotheses A hypothesis is a For example using carefully designed experiments biologists test ideas about the way the natural world works by testing the predictions made by alternative hypotheses Hypothesis Testing Hypothesis testing is a two step process 1 State the hypothesis as precisely as possible and list the predictions it makes 2 Design an observational or experimental study that is capable of testing those predictions An experiment to settle the question So which hypothesis is correct Do cells arise spontaneously under certain conditions Or do cells arise only when pre existing cells grow and divide In 1864 Louis Pasteur set out to perform an experiment to settle the question Get in your groups Hypothesis testing is a two step process 1 State the hypothesis as precisely as possible and list the predictions it makes 2 Design an observational or experimental study that is capable of testing those predictions What are the predictions for each hypothesis based on this experiment Microscopy also established that there were two major types of cells lack a membrane enclosed nucleus have a membrane enclosed nucleus The Tree of Life The tree of life is a family tree of organisms that describes the genealogical relationships among species with a single ancestral species at its base Phylogeny is the actual genealogical relationships among all organisms A reflects relationships between species Branches that share a recent common ancestor represent species that are closely related branches that don t share recent common ancestors represent species that are more distantly related Interpreting the Tree of Life The tree of life indicates three major groups of organisms Fungi and animals are more closely related to each other than either is to plants Traditional classification schemes were often inaccurate The location of certain branches on the tree is hotly debated and the shape of the tree will continue to change as databases expand
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