Biology

Biology- The science of life – The study of living things.

Organism – A living thing

If an organism is alive, it will share certain characteristics with all living

things:• All living things are made of cells.

Organisms may be unicellular (one-celled) or multicellular (thousands of differentiated cells).

• The cells of living things are organized. Similar cells are organized into tissues. Organisms that are composed only of tissues are classified as colonial. Similar tissues are organized into organs, organs into systems, and systems into multicellular organisms.

• Organisms have a constant energy demand to maintain their metabolism. Metabolism is the sum of all the processes necessary to maintain life. This energy demand means that the organism needs nutrients. Heterotrophs are organisms that must consume nutrients such as a lion. Autotrophs are organisms that are able to make their own nutrients.

• Organisms maintain homeostasis or a stable internal environment such as birds puffing their feathers in cold weather.

• Organisms grow. This growth occurs because of cell division, cell growth, and development of the organism. Simple enlargement such as a sand dune adding on layers cannot be considered true growth.

Organisms are irritable. That is they can respond to their

environment.

• Organisms reproduce. While reproduction is not a requirement of each individual, it is necessary for the species to continue. Organisms produce similar offspring in a process called heredity. DNA or the code for traits form genes which form traits. A large number of genes forms a chromosome which is duplicated in reproduction. Reproduction such as cell division that involves only one parent is considered asexual reproduction. Reproduction that involves the combination of two gametes to form a zygote as in the pollination of a flower is considered sexual reproduction.

The world contains a diverse range of organisms. Many organisms have not been discovered yet. Scientists

have agreed that this diversity or biodiversity is necessary

for our planet to remain stable.

Unifying Themes of Biology

• Cellular Structure and Function

• Reproduction

• Metabolism

• Homeostasis

• Heredity

• Evolution

• Interdependence

Biology Solves Real World Problems

• Preserving our environment

• Improving the food supply

• Understanding the human genome

• Fighting diseases such as AIDS, cancer, and emerging diseases

• Developing gene therapy

The rainforests are being burned at a rate of more than one acre per second.

Genetically engineered crops can be resistant to herbicides, poisonous to some pest, and yield

phenomenal quanities of food.

By understanding the human genome, thousands of gene related medical

mysteries will be solved

Scientific Processes

In the summer of 1988, David Bradford was studying a species of small frogs in some Rocky Mountain lakes. These frogs had inhabited these lakes since records had been kept. Bradford discovered that the frogs had disappeared from 98

percent of their habitat. Bradford reported his findings to other biologists. John Harte who was studying salamanders

in the Rocky Mountains read about Bradford’s findings.

Statement of a Problem

Harte wanted to discover the facts surrounding the disappearance of the

amphibians in the Rockies and began a scientific investigation.

Scientific investigations generally follow a set of steps called the scientific method. The scientific method lends itself to logic thought. It generally contains some sequence of the following steps:

Collecting accurate observations.Asking questions

Forming a hypothesis and making predictionsConfirming predictions with a controlled

experimentDrawing conclusions

Collecting Accurate Observations

Accurate observations are a necessity for the validity of the

whole study.

Harte had his college students help him collect water samples and make other observations of

ponds in the mountains.

Asking Questions

Harte knew by observation that acid rain precipitation was released as the snow melted in the spring causing a sudden change in the ponds and lakes of the

Rockies.

Forming a Hypothesis

A hypothesis is an educated guess or, more precisely, a testable statement. Harte developed

two related hypotheses:

Acids that were formed in the upper atmosphere by pollutants were falling onto the mountains in

winter snows.

Melting snow was making the ponds acidic and harming the salamander embryos.

Harte predicted that the acidity of the ponds would increase as the winter snow melted

and that the acidity would be high enough to harm salamander embryos.

Confirming Predictions With a Controlled Experiment

Harte gathered years of data about the changes in the pH of Rocky Mountain Lakes. Harte's data indicated a distinct drop in the pH of mountain ponds during the May and June

snow melt. Then, it leveled off and began to rise again. Minerals in the rocks probably provided a neutralizing

effect.

To test his second hypothesis, Harte would perform a controlled experiment in which he

would expose salamander embryoes to changes in pH. He would keep one group in

a normal pond water environment as a control. Experimental groups would be

subjected to changes in pH.In the experiment, the factor that Harte

would change, the pH, was the independent varible. The factor that was measured, the health of the embryoes, was the dependent

varible.

Harte found that the drop in pH did have a distinct effect on the health of the

embryoes. In fact, many of the embryoes did not hatch and some that did had

abnormalities that caused them to die.

Drawing Conclusions

Once experimentation was completed and the data organized, Harte had to decide if his hypotheses were supported or rejected. His data distinctly supported

both of his hypotheses and other scientists repeated his findings with many other amphibian groups in the Rocky

Mountains.

Viewing Conclusions in Context

Scientists have communicated their results and worked together to attribute the decline in amphibians worldwide to

4 major factors:

• Habitats are deteriorating and being destroyed.

• Nonnative species are outcompeting native amphibian species.

• Chemical pollutants tend to accumulate in amphibian habitats.

• Amphibians suffer from a high rate of infections.

Scientific Explanations

Like the sculpting of a statue, scientific research chips away at the useless stone of problems such as the decline of amphibians

until the larger problem can be described and studied. It has now been described and a

model has been constructed.

Constructing a Theory

As scientists analyze each other's work and streamline the model, an explanation emerges that is widely

believed because it has been tested many times. This is a

theory.