BIO 172 1st Edition Lecture 2Outline of Last Lecture I. Introduction, Major Aspects of Biology, and Started Cell TheoryOutline of Current Lecture I. Four Parts of Cell TheoryII. Redi and Pasteur’s Experiments (with diagrams)III. Theory of Evolution by Natural SelectionIV. The Scientific MethodV. Begin to Review Basic ChemistryCurrent LectureFour Parts of Cell Theory:Cells are the structural unit of life. - All living matter is composed of cells. - Proposed by Schleiden and Schwann (1839)Cells are the functional unit of life.- Cells are the smallest entities that have all the properties of life. - Review: the properties of life are Order, Energy Utilization, Response to Environment, Reproduction, and Evolution.- Each cell is, or can potentially generate, an entire organism.All cells are fundamentally similar.- Hereditary information held in DNA.- All cells have similar structure and organization.- Cells have similar metabolic strategies to use energy.- Specific cell functions can vary, and this is called cell specialization.Cells might have underlying biology that is similar, but their purpose/task is slightly different. As an example, human skin cells are lightly different from cells in our muscles.All cells come from pre-existing cells.- First proposed by Virchow in 1858.These notes represent a detailed interpretation of the professor’s lecture. GradeBuddy is best used as a supplement to your own notes, not as a substitute.- Cells grow and divide.- Life cannot and does not arise from “non-life.”- Most cell biologists do not consider viruses to be cells; viruses are “packets” of hereditary material in coats of protein. They require the hosts’ metabolic machinery to make new viruses, thus they cannot reproduce on their own.- A virus is not the smallest unit of life because it lacks a cell to replicate in. A virus does meet these requirements for life: genetic information enclosed, and a protein coat.Redi and Pasteur disproved “spontaneous generation” through experiments:Francesco Redi- can living organisms arise from nonliving matter?He placed meat in a jar and left it where flies could buzz around. He had three levels of covers for the jars:Redi found that maggots must have come from other flies. Maggots did NOT just arise from the nonliving matter (meat).Louis Pasteur- can microorganisms appear on their own in sterile liquid?He boiled liquid so it was sterilized.Pasteur had previously observed unsterilized liquid sitting in an open container that microorganisms grew in and they soured the liquid. For his new experiment, Pasteur used a flask whose neck did not allow microorganisms to fall into the sterile liquid; diagrams below.Pasteur noted that no microorganisms spontaneously grew in the sterile, protected liquid.But Pasteur noted that when he allowed microorganisms to come into contact with the sterile liquid, the microorganisms were able to grow in the liquid. The liquid was still sterile until it came into slight contact (from him tipping the beaker!), which proved that the dust in the liquid must have helped the other cells/microorganisms grow.Theory of Evolution by Natural SelectionDarwin and Wallace, in 1858, suggested that all species are related from a common ancestor.During the process of reproduction/evolution, inheritable traits that provide a fitness advantageare what is passed on that help species evolve.For Natural selection to happen:1. Individuals in a population must have some heritable traits that are different from one another.2. These differing traits must be advantageous, so that the individuals with those traits must survive and reproduce better than those without the advantageous trait.Three Domains of Life are Recognized:Archaea, Bacteria, and Eukaryotes. They are organized on the tree of life according to the diagram below:Prokaryotes: any cell that lacks a nucleus. Bacteria and archaea are prokaryotes.Eukaryotes: cells that have a membrane-enclosed nucleus. All plant and animal cells.Both prokaryotes and eukaryotes have DNA, because they are two classes of cells.The relationships among living organisms are determined using ribosomal RNA gene sequencing. By looking at the cells of different species and comparing/contrasting their genetic information, we can determine the evolutionary relationship between cells. This practice determines phylogeny, or a tree diagram showing probably evolutionary relationships.For example: Look at the sequence of DNA strands next to each other. Based on how close those DNA sequences are, you can tell which strands are closely related; therefore you cantell which organisms are more closely related. Below, “1” is more closely related to “3” than it is to “2”.Based off ribosomal RNA comparisons, scientists found that Archaea are more closely related to Eukaryotes than to Bacteria. For actions within cells, like transcription, translation, and DNA replication; Archaea is more similar to Eukaryotes than Bacteria.Archaea and Bacteria are both considered to be PROKARYOTES due to their similarities in cellular organization. These similarities in organization include being single celled organisms and that they do not have membrane bound organelles.Some extreme environments host species of Archaea:- Thermophiles: can survive at 90°C to 110°C.- Halophiles: live in environments with high levels of salt.- Acidophiles: thrive at low pH levels (very acidic! pH < 2.0)- Some Archaea and Bacteria like extreme cold or extreme alkaline (basic) pH.The Scientific Method:National Academy of Sciences Definitions:Fact: an observation that has been repeatedly confirmed.Hypothesis: a testable statement about the natural world that can be used to build more complex inferences and explanations.A hypothesis works as a proposed explanation for something.Law: a descriptive generalization about how some aspect of the natural world behaves under stated circumstances. For example: Mendel’s Law of Independent Assortment (does not explain why independent assortment happens, rather, the law is just a description). Laws of motion, gravity, thermodynamics.Theory: an overarching explanation of some aspect of the natural world that is well substantiated and that can incorporate facts, laws, inferences, and tested hypotheses.Order in the Scientific Method:Make Observations. Ask Questions. Form a Hypothesis. Make Predictions. Test your predictions; include controls in your