Chapter 1: Invitation to biology

Once there was a highly intelligent turkey that had nothing to do but reflect on the world's regularities. Morning always started out with the sky turning light, followed by the master's footsteps, which were always followed by the appearance of food. Other things varied, but food always followed footsteps. The sequence of events was so predictable that it eventually became the basis of the turkey's theory about the goodness of the world. One morning, after more than 100 confirmations of the goodness theory, the turkey listened for the master's footsteps, heard them, and had its head chopped off. Any scientific theory is modified or discarded upon discovery of contradictory evidence. The absence of absolute certainty has led some people to conclude that "facts are irrelevant—facts change." If that is so, should we stop doing scientific research? Why or why not?

"Facts change." That is true in scientific research because science is open to new data and new interpretations of old data, which can lead to discarding or modifying formerly-held tenets. This is a strength of science, not a weakness. It is this willingness to accept change that makes the phrase "scientific creationism" meaningless. Creationists have accepted as fact a set of immutable ideas, which are then supported by carefully chosen facts from the realm of science.

Which is the correct format for a scientific name?

(italicizes) Homo sapiens

An experimenter surveyed one-half acre of a desert preserve and found three cactus wren nests. Assuming that the habitat is fairly uniform, how many nests would he expect to be in the entire 200-acre preserve?

1200

You are interviewing a researcher. She states that she does not publish her data from experiments because she does not trust other scientists. How would you respond? (Hint: think about one of the main steps of the scientific method).

A necessary part of science is reporting one's results and conclusions in a standard way, such as in a peer-reviewed journal article. The communication gives other scientists an opportunity to evaluate the information for themselves, both by checking the conclusions drawn and by repeating the experiments. The scientific community consists of critically thinking people trying to poke holes in one another's ideas. Their collective efforts make science a self-correcting endeavor.

A person is declared to be dead upon the irreversible cessation of spontaneous body functions: brain activity, or blood circulation and respiration. However, only about 1% of a person's cells have to die in order for all of these things to happen. How can someone be dead when 99% of his or her cells are still alive?

A person can be considered dead with only a small fraction of their cells being dead, as those cells are responsible for coordinating the action of all the other cells, and for ultimately maintaining the homeostasis of the organism as a whole.

Imagine that a researcher for a large food company believes that he has developed a new drug that increases appetite. He names the drug "EatMore" and designs an experiment to test his hypothesis. He used two groups of mice; one group is given the drug and the other group given a placebo sugar pill. The appetite levels were measured based on the amount of food consumed by mice in each group for one week. At the end of the experiment, he reported that on average, mice that received the "EatMore" drug consumed 2.5g of food/day and mice that received the placebo consumed 5g of food/day. Statistical analysis of the data showed that the difference was statistically significant. Match the following terms with the conditions related to the accompanying experiment: a. independent variable b. dependent variable c. experimental group d. control group (question) The treatment of the "EatMore" drug

A: Independent Variable

Imagine that a researcher for a large food company believes that he has developed a new drug that increases appetite. He names the drug "EatMore" and designs an experiment to test his hypothesis. He used two groups of mice; one group is given the drug and the other group given a placebo sugar pill. The appetite levels were measured based on the amount of food consumed by mice in each group for one week. At the end of the experiment, he reported that on average, mice that received the "EatMore" drug consumed 2.5g of food/day and mice that received the placebo consumed 5g of food/day. Statistical analysis of the data showed that the difference was statistically significant. Match the following terms with the conditions related to the accompanying experiment: a. independent variable b. dependent variable c. experimental group d. control group (question) The amount of food consumed

B. Dependent variable

Imagine that a researcher for a large food company believes that he has developed a new drug that increases appetite. He names the drug "EatMore" and designs an experiment to test his hypothesis. He used two groups of mice; one group is given the drug and the other group given a placebo sugar pill. The appetite levels were measured based on the amount of food consumed by mice in each group for one week. At the end of the experiment, he reported that on average, mice that received the "EatMore" drug consumed 2.5g of food/day and mice that received the placebo consumed 5g of food/day. Statistical analysis of the data showed that the difference was statistically significant. Match the following terms with the conditions related to the accompanying experiment: a. independent variable b. dependent variable c. experimental group d. control group (question) The mice that received the "EatMore" drug

C. Experimental group

Which statement could be considered a scientific theory?

Change occurs in the inherited traits of a population over generations.

Four of the five answers listed below are aspects of the scientific method. Select the exception. a. observation b. hypothesis c. experimentation d. philosophy e. conclusion

D. Philosophy

Imagine that a researcher for a large food company believes that he has developed a new drug that increases appetite. He names the drug "EatMore" and designs an experiment to test his hypothesis. He used two groups of mice; one group is given the drug and the other group given a placebo sugar pill. The appetite levels were measured based on the amount of food consumed by mice in each group for one week. At the end of the experiment, he reported that on average, mice that received the "EatMore" drug consumed 2.5g of food/day and mice that received the placebo consumed 5g of food/day. Statistical analysis of the data showed that the difference was statistically significant. Match the following terms with the conditions related to the accompanying experiment: a. independent variable b. dependent variable c. experimental group d. control group (question) The mice that received the placebo

D: control Group

A scientist randomly divided a group of 100 lab rats into two groups of 50. One group was fed regular rat chow while the other was fed the same amount of rat chow with added DDT. Both groups were housed in the same room with the same environmental conditions. At the end of the experiment, rats were weighed and the mean difference calculated. Refer to the accompanying narrative. What variable or variables were manipulated by the scientist?

DDT only

Hereditary instructions for growth and development are carried in:

DNA

_____ is the transmission of DNA to offspring.

Inheritance

In 2005, researcher Woo-suk Hwang reported that he had made immortal stem cells from human patients. His research was hailed as a breakthrough for people affected by degenerative diseases, because stem cells may be used to repair a person's own damaged tissues. Hwang published his results in a peer-reviewed journal. In 2006, the journal retracted his paper after other scientists discovered that Hwang's group had faked their data. Does the incident show that results of scientific studies cannot be trusted? Or does it confirm the usefulness of a scientific approach, because other scientists discovered and exposed the fraud?

It is unfortunate that the respectable journal did not catch any experimental fraud; however, this is an example of "facts change." The process of science did work, and when the results could not be confirmed the article was retracted. It is important to hold scientists accountable for their work, and this scientist was held accountable and lost his research privileges. As in all professions, just because one person is unethical it is not fair to judge the work of everyone in that profession based on one person's actions.

The cell theory states that all organisms consist of one or more cells, the cell is the basic unit of life, and all cells arise from existing cells. This is a scientific theory. How could the cell theory be disproven?

Like all hypotheses, a scientific theory can be disproven by one observation or result that is inconsistent with it. Therefore, if a scientist discovered a living organism that did not consist of a cell or if they discovered a cell that spontaneously formed on its own, the theory would be disproven.

Refer to the accompanying figure. If only 50 test subjects had been used in this study and it was determined that 40% of people in the experimental group get cramps (rather than 15.8%), what is the most likely reason for the different results?

The Olestra potato chips were given to the wrong group.

Refer to the accompanying figure. What was the independent variable in this experiment?

The consumption of potato chips

Refer to the accompanying figure. What was the dependent variable in this experiment?

The presence of intestinal cramps

Refer to the accompanying figure. What are some variables that were not controlled for in this experiment that may affect the results?

The test subjects were not controlled for their gender, age, weight, health status, medication use, etc.

Why would you think twice about ordering from a cafe menu that lists the genus name but not the specific epithet of its offerings? Hint: Look up Homarus americanus, Ursus americanus, Ceanothus americanus, Bufo americanus, Lepus americanus, and Nicrophorus americanus.

When understanding the complete scientific name, you can see that the genus defines what each of these organisms is: American black bear, New Jersey tea, garden toad, or a snowshoe hare. At a café, you are probably interested in the tea (Ceanothus americanus)!

The eighteenth-century naturalist Carolus Linnaeus is known for creating:

a system for naming and classifying organisms

Imagine that a researcher for a large food company believes that he has developed a new drug that increases appetite. He names the drug "EatMore" and designs an experiment to test his hypothesis. He used two groups of mice; one group is given the drug and the other group given a placebo sugar pill. The appetite levels were measured based on the amount of food consumed by mice in each group for one week. At the end of the experiment, he reported that on average, mice that received the "EatMore" drug consumed 2.5g of food/day and mice that received the placebo consumed 5g of food/day. Statistical analysis of the data showed that the difference was statistically significant. Answer the following questions about the accompanying experiment. a. What is the researcher's hypothesis? b. What would be the researcher's prediction? c. Why may this experiment be performed with a model organism, rather than on humans? d. Was the researcher's hypothesis correct? e. What may be some alternate explanations for the outcome?

a. The researcher's hypothesis is that the "EatMore" drug increases appetite. b. The researcher's prediction would be that "if the EatMore drug increases appetite; then mice that receive the drug will eat more food than control mice that do not receive the drug." c. The researcher performed the experiment using a model organism rather than humans for several reasons. One is that it is easier to control other variables in mice that may affect the outcome. For example, the researcher can select mice of the same age, sex, genetic background, etc. He can also control exactly what mice eat and measure it directly, which he could not do as easily with human subjects. Another reason would be that the drug is not approved by government regulations to be tested on humans if he just developed it. d. No, the researcher's hypothesis is not correct. Mice that received the "EatMore" drug ate less food and therefore did not have an increased appetite. e. Some alternate explanations for the outcome may be that the drug had side effects that influenced how much food the mice ate. Perhaps it made the mice feel sick and not want to eat, or perhaps it made them drowsy, which made them eat less.

The control group in an experiment:

allows a standard of comparison for the experimental group

Match the following terms with the appropriate level of organization: oxygen

atom

An experimenter is involved in four of the five tasks below. Select the exception. a. revises a hypothesis as a result of data collected b. manipulates dependent variables c. reviews other research results obtained by other scientists d. examines the effects of independent variables e. draws conclusions based only on appropriate experimental data

b. manipulates dependent variables

Which domain or domains are made up of organisms without nuclei?

both archaea and bacteria

Arrange the following terms in order from least complex to most complex: a. biosphere b. cell c. atom d. population e. organ f. community g. ecosystem

c, b, e, d, f, g, a

Four of the five answers listed below are names of kingdoms. Select the exception. a. Animalia b. Protista c. Eukarya d. Fungi e. Plantae

c. Eukarya

Match the following terms with the appropriate level of organization: red blood

cell

The smallest unit of life that can survive and reproduce on its own is a(n):

cell

Match the following terms with the appropriate level of organization: arctic foxes, polar bears, fish, mosses, shrubs (all species in the arctic tundra)

community

Populations within California's Antelope Valley interact with their physical environment (e.g., sunlight and water) to sustain life. Which level of life's organization is appropriate for this scenario?

community

What term describes "all populations of all species living in the same area"?

community

Grass growing in a field is eaten by a deer. Later on, the deer dies and its body is decomposed, in part, by bacteria. Which organism(s) are consumers?

deer and bacteria

What term describes the process of transformation of the first cell of a new individual into an adult?

development

What is the most diverse and inclusive classification group?

domain

Four of the five answers listed below are necessary characteristics to the life of an individual. Select the exception. a. energy use b. homeostasis c. development d. response to stimuli e. diversity

e. diversity

Match the following terms with the appropriate level of organization: all arctic animals, plants, etc. interacting with their physical environment

ecosystem

Which eukaryotes break down food externally and then absorb nutrients?

fungi

A scientific name consists of which of the following?

genus name and specific epithet

What term refers to an increase in number, size, or volume in the cells of an organism?

growth

As energy is transferred among organisms, some escapes from the environment as ____ energy.

heat

About 12 to 24 hours after the last meal, a person's blood sugar level normally varies from 60 to 90 mg per 100 ml of blood, although it may rise to 130 mg per 100 ml after meals high in carbohydrates. That the blood sugar level is maintained within a fairly narrow range, despite uneven intake of sugar, is due to the bodily process called:

homeostasis

Organisms exhibit this characteristic, which tends to buffer the effects of environmental change

homeostasis

What is the process used by living things to maintain an internal environment within a tolerable range?

homeostasis

In order to arrive at a solution to a problem, a scientist usually proposes and tests:

hypotheses

A testable explanation for a natural phenomenon is a(n):

hypothesis

testable explanation

hypothesis

A scientist is investigating the results of varying temperature on the growth rate of a bacterial culture. In this experiment, temperature is the:

independent variable

Arriving at a conclusion based upon one's observations is known as:

inductive reasoning

Critical thinking is the process of:

judging the quality of information before accepting it

What term describes a consistent natural phenomenon for which there is an incomplete scientific explanation?

law of nature

The capacity to acquire, store, and use energy

metabolism

Match the following terms with the appropriate level of organization: circulatory system

organ system

A process found only in producers

photosynthesis

Which organisms are multicellular eukaryotes, with the majority being photosynthetic producers?

plants

All of the coyotes (Canis latrans) living in the Mojave Desert constitute a(n):

population

Match the following terms with the appropriate level of organization: group of arctic foxes in the arctic tundra

population

statement of what a hypothesis leads you to expect

prediction

measure of chance

probability

Plants use energy from the sun to produce nutrients. Plants are therefore:

producers

In order to reduce bias, scientists usually prefer experiments that lead to what kind of results?

quantitative

Process in which one generation replaces another

reproduction

Suppose that in an experiment, different results are obtained from a subset than the results obtained from the whole. What term would best explain this?

sampling error

A hypothesis that has been repeatedly and rigorously tested and supported is known as a:

scientific theory

time-tested hypothesis

scientific theory

Organisms designated as producers usually obtain their energy from

the enviroment

In an experiment, the experimental group is:

treated exactly the same as the control group, except for one independent variable

An experimental result that is statistically significant is:

unlikely to occur by chance alone

A scientist randomly divided a group of 100 lab rats into two groups of 50. One group was fed regular rat chow while the other was fed the same amount of rat chow with added DDT. Both groups were housed in the same room with the same environmental conditions. At the end of the experiment, rats were weighed and the mean difference calculated. Refer to the accompanying narrative. What dependent variable was measured?

weight