Model Answer:

The steps of the scientific method consist of Observation, Hypothesis, Prediction, Experiment, and Theory. The first step is observation. An observation is a phenomenon that you see occurring in the world around you. It allows you to ask a pointed question about a particular aspect of nature. The second step is formulating a hypothesis. A hypothesis is a tentative explanation or reason your observation occurs. A hypothesis differs from just a “guess” in two important ways: (1) A hypothesis makes predictions as to the results of experiments or other new observations yet unseen, and (2) because a hypothesis makes predictions, it can be tested. The third step in the scientific method is to make a prediction. A prediction allows the hypothesis to be tested experimentally and can often be answered by yes or no. To test the prediction, and ultimately, the hypothesis, you need to run experiments or make new observations. This fourth step of the scientific method is an important one because a hypothesis can be rejected or supported at this point. If the original hypothesis is rejected based on your experiments or new observations, a new hypothesis can be formulated which would then be tested. A test result or observation that supports the initial hypothesis makes the hypothesis less tentative and more certain. When a hypothesis is supported again and again over time, through experiments and observations, it will usually be regarded as an acceptable explanation for what we initially observed. At this point, the hypothesis becomes a theory. For example, the theory of evolution has been tested for more than a century and shown to be a supported explanation of many biological observations.

Model Answer:

A guess is just that. It does not make predictions as to why an observation or event is happening, nor can it be tested to prove that it is right or wrong. A hypothesis is an explanation of that observation or event that predicts the results of experiments or new observations that will be tested. A theory is a broad explanation that accounts for a number of related hypotheses that have been repeatedly supported through vigorous testing, often over a long period of time.

Model Answer:

See Figures 1.6 and 1.7. The first law of thermodynamics states that energy can neither be created nor destroyed; it can only be transformed from one form into another. Living organisms transform energy from the environment into chemical energy that cells can utilize. To convert this energy, the cell has to expend energy and give off heat, which results in the cell giving off as much energy as it initially takes in. The second law of thermodynamics states that the degree of disorder in the universe tends to increase. The amount of disorder in a system is called the entropy of the system. Living organisms are highly organized and thus need a lot of energy to remain this way. This observation does not violate the second law, however, because the cell gives off excess energy as heat, which causes small molecules in the environment to move more. This increase in movement increases the disorder or entropy of the entire system, thus satisfying the second law of thermodynamics.

Model Answer:

A cell is the simplest self-replicating entity that can exist as an independent unit of life. Organisms can either be single-celled (made up of one cell; e.g., bacteria) or multicellular (made up of many cells; e.g., humans). All cells have a discrete boundary that separates their interior from the external environment, and they also all have the ability to harness materials and energy from that environment.

Model Answer:

See Figures 1.8 and 1.9. Experiments done by Francesco Redi and Louis Pasteur tested the hypothesis that organisms arise from other organisms. Through eloquently designed experiments, the scientists were able to show that flies and bacteria arose from other flies and bacteria, respectively. By following the scientific method, these scientists were able to disprove the hypothesis that organisms arise spontaneously.

Model Answer:

An example of how evolution is responsible for both the unity and diversity of life can be found in our own evolution. Using genetic information scientists can relate one species to another, often elucidating information concerning the evolutionary timeline and the divergence of these species from a common ancestor. An example of this unity is found in Figure 1.17 “The tree of life.” Evolution can also account for the diversity of life. Take a look around you. All the people you see are Homo sapiens (or humans) yet no two, without exception, look exactly the same. These differences arise from the genetic differences that exist from one person’s genome to another. Over time, these differences are established in particular groups (e.g., each member of a family having dark curly hair) and can be used to differentiate between organisms of the same species. Diversity can also be seen in the variety of species around you, all related somehow but yet all different.

Model Answer:

Anatomy, physiology and behavior are all features of organisms that shape ecological systems. Often it is not only the features of one species, but the features of many that lead to a diverse ecological system.

Model Answer:

Humans have expanded the populations of certain organisms, many of which are related to the food supply (e.g., corn, yeast, lactose-fermenting bacteria, grapes, etc.). Conversely humans have also reduced populations of other organisms, sometimes to extinction, through hunting and habitat destruction (e.g., dodo birds, white rhinoceros, Bali tiger, etc.). Our ever-expanding population and technological abilities have significantly impacted the amounts and types of gases that enter and exit the Earth’s atmosphere. The identification and harnessing of the powerful antibiotics have both benefited (treating once deadly infections) and harmed (evolution of antibiotic resistant bacterial strains) the human race.

Model Answer:

(1) The scientific method is a deliberate way of asking and answering questions about the natural world. Much of what we know and believe today is due to the process of the scientific method. This method is used to inquire about and determine what is happening in the world around us.

(2) Life works according to fundamental principles of chemistry and physics. Energy is what drives life. The basic rules of energy conservation are observed by every living organism.

(3) The fundamental unit of life is the cell. All living organisms are made up of at least one cell, thus making the cell the simplest biological entity that can exist independently.

(4) Both the features that organisms share and those that set them apart are explained by evolution. Evolution is the process by which certain traits are selected for by pressures in the environment. These traits can at once relate the organism to one species and distance it from another. The tree of life is a good representation of how evolution is both unifying and diversifying.

(5) Organisms interact with one another and with their physical environment, shaping ecological systems that sustain life. An ecological system is typically made up of more than one species. There is a web of behavioral and physical interactions that help support each species in an ecological system.

(6) In the 21st century, humans have become major agents in ecology and evolution. The actions of humans can be felt in almost every facet of life, positively or negatively. Whether it is curing a disease affecting cattle or driving a species into extinction, humans play, and have played, an important role in the development of life as we know it today.