Bio 120 - Unit 1

Null Hypothesis

(in a statistical test) the hypothesis that there is no significant difference between specified populations, any observed difference being due to sampling or experimental error. A null hypothesis is used when determining whether or not there is a correlation between two events. A null hypothesis is the hypothesis that results obtained (and any variation contained in them) are a consequence of random chance. i.e: placebo drug

Evolutionary change occurs by what two mechanisms?

- Horizontal gene transfer - Vertical descent with mutation

Theory

A theory is a reasoned explanation of known facts or phenomena that serves as a basis of investigation to reach the truth. Theories are just under laws in terms of reliability because they are dependent upon a collection of known facts. An example is the theory of evolution which states that mutation within a chromosomal DNA can change the physical characteristics of an individual. If this change is passed on to other individuals in a population and gives those "unique" individuals a survival advantage, a population can change over time.

A hypothesis must make ______ that can be tested, and a hypothesis must be ______, which means it can be shown to be incorrect.

Blank 1: predictions Blank 2: falsifiable

The two mechanisms that lead to evolutionary change are -- descent with modification/mutation and -- gene transfer.

Blank 1: vertical or vertical evolution Blank 2: horizontal or lateral

If the results of an experiment are statistically significant, it means that the differences observed between the experimental group and the control group --

are NOT likely to be due to chance.

Scientists often conduct their experiments in a parallel manner on two groups: an experimental group and a ______ group, one in which the key variable is kept constant.

control

When should a hypothesis be rejected?

When the data from the control and experimental groups are NOT statistically different from one another.

Facts

a thing that is known or proved to be true. -- A fact is a truth established by observation. A single fact is sometimes referred to as a datum. It can be quantitative (associated with a unit) or qualitative (yes/no; +/-). A collection of facts/datum is referred to as data. Hence, the term data is plural. An example of a fact is that humans have 23 (haploid) or 46 (diploid) unique chromosomes.

All living organisms contain genetic material that is composed of:

deoxyribonucleic acid (DNA (genes))

Researchers typically follow two general types of approaches while conducting biological investigations:

discovery-based science and hypothesis testing.

A proposed explanation for a natural phenomenon is called a --

hypothesis

The observation, identification, experimental investigation, and theoretical explanation of natural phenomenon can be defined as --

science In conclusion, we can say that science is the relentless pursuit of truth regarding the composition and natural formation of the universe.

Select all the characteristics of a scientific hypothesis.

should be falsifiable (if incorrect), must make predictions

When differences between control and experimental data are not attributed to random chance, the data are considered:

statistically significant

Biological Evolution

the change over time in populations of organisms

Hypothesis

A hypothesis is a tentative explanation or interpretation of data. It must be verifiable or falsifiable or else it is just a guess. Usually, scientific hypotheses are specific, easy to falsify, and difficult to verify. Associated with a hypothesis is a null hypothesis. A null hypothesis is a statistical hypothesis that one variable has no association with another or that experimental results do not differ from those that might be expected by the operation of chance alone. In other words, a null hypothesis predicts what the outcome would be if there were no outside influences (extrinsic factors) affecting the results of an experiment. An example of a hypothesis is that some segments of human chromosomes are more subject to mutation than others. The null hypothesis, then, would be that all chromosomes are equally subject to mutation.

Laws

A law is a statement regarding a sequence of phenomena that is invariable under given conditions. The key elements of this definition relate to the idea that certain phenomena never deviate under identical conditions. An example of law is that a human will always beget a human, a horse a horse, etc. because of the law of inheritance.

Horizontal Gene Transfer

A process in which an organism incorporates genetic material from another organism without being the offspring of that organism

What determines the function of a biological molecule?

It's structure

Following Paradigms

Following paradigms is sometimes referred to as normal science. It consists of continuing in some direction of puzzle-solving steps that may have been started by yourself or someone else. In other words, it is set in motion by a body of earlier research within a given, specific area of study. Today, scientists often follow a line of research and seek to make new observations to add to the knowledge base. In this manner of inquiry, hypothesis testing is of secondary importance.

Hypothesis-making

Hypothesizing involves making a general claim (hypothesis) from which one devises experiments to test whether or not it is true. The experimental design must include methods to try and falsify the hypothesis. If the claim cannot be tested, it is not a hypothesis. Hypothesis making is based upon deductive reasoning. A problem with this method of inquiry is that the scientist must ensure that a hypothesis is easily falsifiable. In other words, it must be easy to test whether or not it might be false. Additionally, it has the limitation that it is good until someone proves it wrong. Deductive reasoning argues a conclusion based upon more general statements, or what are referred to as premises. In this manner, deductive reasoning links general statements with conclusions. For instance, if we hold the general premise that all birds have feathers, then we are told that a certain animal is a bird, we can deduce that it must have feathers.

Intervention/Experimentation

Intervention or experimentation necessitates the isolation of the subject. It does allow one to simplify or control the phenomenon being studied. Also, it allows a scientist to change one variable at a time to observe and record the effect of such change. It is based on inductive reasoning. Some problems unique to this scientific method are the inherent nature of subjectivity and the limitation of the predictive value for generalizations. Inductive reasoning is a type of logic in which a specific observation leads to a general conclusion. It creates generalizations from observations which are believed to be representative of a population or group. For instance, we might record that A and B are observed together several times, and therefore induce that A and B coincide.

Hypothesis

It is a proposed explanation for observations of a natural phenomenon.

Ideally, control and experimental groups should differ in how many variables?

One - If the control and experimental groups differ in more than one variable, it will not be possible to tell which variable is responsible.

Researchers design and conduct experiments in order to test which of the following?

Predictions

Q, P, R, C

Question: What question was being asked by the scientist(s) that conducted the experiment(s)? Protocol: How did the scientist(s) obtain the data? What was the protocol or method employed in the experiment(s)? Results: What are the data? Or, what are the result(s) of the experiment(s)? Conclusions: What do the data mean? What conclusions can be drawn? How should the data be interpreted or evaluated?

Systematic Observation

Systematic observation requires the gathering of facts by sampling. One fundamental problem with systematic observation is the interpretation of what we observe. What we see and what we perceive may be different. Our objectivity may be clouded by bias in asking questions. What is repeatable in one lab may not be in another because of some nuance which we did not take into consideration. Statistics can be used to manipulate data in a biased manner, either intentionally or unintentionally. The samples we obtain may not accurately reflect an entire population.

There are four general methods that scientists employ to find truth:

Systematic observation, intervention or experimentation, hypothesis-making, and following paradigms.

P-Values

The probability, computed assuming the null hypothesis is true, that the statistic would take a value as extreme as or more extreme than the one actually observed, in the direction specified by the alternative hypothesis. P is the probability that the result obtained could occur by random chance. P-values are between 0 and 1. If the p-value is high, that means there is a high probability that the variation is due to random chance (i.e., the data probably supports the null hypothesis). If the p-value is low, that means there is a low probability that the variation is due to random chance, meaning something else probably caused the variation (i.e., the data probably supports the hypothesis). There is a value selected as the cut-off for p-values being low or high. When p < 0.05, that is considered a low probability that the variation was due to random chance. This is a general value used in all of science. Any value above 0.05 means that there is a high probability that the variation is due to random chance. This p = 0.05 (5%) threshold we are discussing is defined as the alpha level. The rule of thumb is to assume an alpha level of p = 0.05 unless conditions warrant otherwise. Generally, if a greater level of confidence in the experimental results is desired, the a priori (before the fact) alpha level is decreased prior to conducting the experiment or analyzing the data.

How do scientists determine whether the results of an experiment differ between an experimental group and a control group?

They analyze the data with statistics.

Arrange the following steps of the scientific method in the correct order, beginning with the first step at the top.

observation, hypothesis presented, experiment, data analysis, hypotheses supported or rejected

Vertical Evolution

occurs in a lineage - the traditional way to study evolution is to examine a progression of changes in a series of related ancestral species.