Chapter 1

  1. Why is life difficult to define?

     1. Life is difficult to define because a definition would be particularly difficult for the theories of the origin of life from nonliving matter, but all living cells share metabolic processes and genetic information that reveal unmistakably their hereditary descent from life’s common ancestor. ==We do not know the origins of non-living matter, which makes it difficult to give life a definition.== The diversity of emergent properties that we see at all levels of the biological hierarchy contributes to the difficulty of giving life a simple description or definition.

  1. What are the basic chemical differences that distinguish living from nonliving systems?

     1. The complex organizational structure of macro-molecules is unique to life: Nucleic acids, Proteins, Carbohydrates, and Lipids. These categories differ in the structures of their component parts, the kinds of chemical bonds that link their subunits together, and their roles in the living systems.

  1. Describe the hierarchical organization of life. How does this organization lead to the emergence of new properties at different levels of biological complexity?

     1. The hierarchical organization of life is

        1. macromolecules (less complex) 2. cells 3. organisms 4. populations 5. species (most complex) 2. And each level builds onto the level below it and has its own internal structure which is also often hierarchical. Each successively higher level of the biological hierarchy is also composed of units of the preceding lower level in the hierarchy. Emergent properties expressed at a particular level of the biological hierarchy are certainly influenced and restricted by properties of the lower-level components. ==Since the levels build onto one another, when another property is emergent in a level, the one below it is responsible.==

  1. What is the relationship between heredity and variation in reproducing biological systems?

     1. Heredity is the faithful transmission of traits from parent to offspring, usually (but not necessarily) observed at the organismal level, and variation is the production of differences among the traits of different individuals. The interaction of heredity and variation in the reproductive process makes organic evolution possible and inevitable.

  1. Describe how evolution of complex organisms is compatible with the second law of thermodynamics.

     1. Living cells maintain complex molecular organization only as long as energy fuels the organization, and the ultimate fate of materials in the cells is degradation and dissipation of their chemical-bond energy as heat. ==So the evolution of complex organisms is compatible with the second law of thermodynamics because, no matter what, complex physical systems always proceed to a greater state of disorder, meaning they evolve with time.==

  1. Using characteristics of how they obtain nutrition, contrast the animals with other major multicellular branches on the tree of life - plants and fungi.

     1. Animals obtain nutrition by eating other organisms, while plants obtain nutrition by using photosynthesis to create their own food internally and fungi obtain nutrition by absorption of small organic molecules from their environments.

  1. Although most mammals have a gut microbiome, many do not depend on their microbiome for survival. Cattle depend for their nutrition on the presence in the foregut of bacteria that digest cellulose. Hypothesize a series of events through which the obligatory condition in cattle evolved from one in which bacteria were present in the gut but were not needed for survival.

     1. A series of events that could cause cattle to evolve from needing bacteria in the gut to not needing it for survival could be if there was a disease that attacks the microbiome and the only cattle that are able to reproduce are the ones who are able to survive and digest their food without the bacteria. So, as generations go on, the cattle that are born do not have the bacteria and are able to digest food without it since the generations that they come from did not have it either.

  1. What are the essential characteristics of science? Describe how evolutionary studies fit these characteristics, whereas “scientific creationism” or “intelligent design theory” does not.

     1. The essential characteristics of science is

        1. Guided by natural law 2. Has to be explanatory by reference to natural law 3. Testable against the observable world 4. Conclusions are tentative and therefore not necessarily the final word 5. Falsifiable 2. These evolutionary studies fit these characteristics because they are based on natural law that allows results to be changed when they are falsified, while “scientific creationism” is a religious, political position advocated by a minority of the American religious community that does not allow their conclusions to be refuted or changed at all.

  1. Use studies of natural selection in British moth populations to illustrate the hypothetico-deductive method of science.

     1. Observation: In industrial areas of England, for more than a century, moths in polluted areas tended to primarily have darkly colored wings and bodies, whereas moths of the same species in unpolluted areas were lightly colored. 2. Question: Why do pigmentation patterns vary according to habitat? 3. Hypothesis: Consumption of soot by caterpillars somehow darkens the pigmentation of the adult moth, null hypothesis: Do contrasting populations from different habitats retain their contrasting characteristics when reared in a common garden? 4. Empirical Test: Reared moths under artificial conditions in a common garden 5. Conclusion: The contrasting wing colors of populations from polluted and unpolluted environments are maintained in the common garden. Offspring of moths from polluted populations retain the dark pigmentation of their parents, whereas offspring of lightly pigmented moths are lightly colored like their parents. ==We thereby reject the hypothesis==.

  1. How do we distinguish the terms hypothesis, theory, paradigm, and scientific fact?

     1. Hypothesis - Often constitute general statements about nature that may explain many diverse observations and can be falsified when a scientist follows the scientific method 2. Theory - A very powerful explanation of a wide variety of things of related phenomena, falsification of one specific hypothesis related to the theory does not fail the theory as a whole, generally accepted 3. Paradigm - Powerful theories that guide extensive research 4. Scientific fact - An explanation for something that has been proven to be true over and over again and is now widely accepted as the “truth” for that specific topic

  1. What are Darwin’s five theories of evolution (as identified by Ernst Mayr)? Which are accepted as face and which continue to stir controversy among biologists?

     1. Perpetual Change - Accepted as fate 2. Common Descent - Accepted as fate 3. Multiplication of Species - Controversy concerning details of this process and the precise meaning of the term “species” 4. Gradualism - Controversial; scientists are actively studying this, but gradualism is known to happen, but it doesn’t explain the origins of all structural differences that we observe among species 5. Natural Selection - Accepted as fate

  1. What major obstacle confronted Darwin’s theory of natural selection when it was first proposed? How was this obstacle overcome?

     1. It lacked a successful theory of heredity. This obstacle was overcome when ==particulate inheritance== was established after 1900 with the discovery of Gregor Mendel’s genetic experiments and was eventually incorporated into what we now call the ==chromosomal theory of inheritance==.

  1. How does neo-Darwinism differ from Darwinism?

     1. Neo-Darwinism differs from Darwinism because it includes the theory of inheritance.

  1. Describe the respective contributions of the genetic approach and cell biology to formulating the chromosomal theory of inheritance

     1. Genetic approach - Mendel’s experiments showed that the effects of a genetic factor can be masked in a hybrid individual, but that these factors are not physically altered during the transmission process. Mendel observed that the inheritance of one pair of traits is independent of the inheritance of other paired traits. 2. Cell Biology - Gave the discovery of chromosomes and because the behavior of chromosomal material during gamete formation parallels that postulated for Mendel’s genes, Sutton and Boveri in 1903 through 1904 hypothesized that chromosomes were the physical bearers of genetic material. This hypothesis met with extreme skepticism when first proposed. A long series of tests designed to falsify it nonetheless showed that its predictions were upheld