Biology in Your World

Preserving Our Environment

Overpopulation – over 7 billion people on Earth! Has a significant impact on other organisms and the environment

Tropical Rain ForestDestruction- Home to many species of plants and animals- Potential medicines and new foods

Other Environmental Issues:

Conservation and preservationGlobal warmingOzone depletionAcid rainEndangered species

AND . . . . . .

Improving the Food Supply

Genetic engineering of crop plants (GM) - transfer genes from one kind of organism to another

Has created plants: Resistant to herbicides Poisonous to insect pests but not humans New varieties with improved nutrition and protein content

ex. Rice with genes that increased vitamin A

and iron

Understanding the Human Genome

Genome - complete genetic material (DNA) contained in an individual

Human Genome Project “completed” 6/26/2000

The Human Genome contains: 3 billion pairs of nucleotides.

Have identified most human genes

Much research still needed to lead to: cures and therapy

treatment new medicines

Fighting Disease

AIDS (acquired immune deficiency syndrome)

HIV (human immunodeficiency virus) - the virus that causes AIDS by attacking and destroying the immune system

Have developed a combinationof drugs to slow progression

No vaccine yet - virus mutatesrapidly

Cancer - a tumor in which the cells begin dividing at an uncontrollable rate and become invasive

Results from a breakdown in the controls for cell division

Many types of cancer can be treated if detected early

Progress in cures for cancer

Emerging Diseases

Increase in infection because of overpopulation andease of transportation.

Ex.

Swine Flu

Gene therapy - replacement of a defective gene with a normal version of the gene

Clinical trials for: cystic fibrosis - a fatal genetic disorder in which excessive amounts of mucus are secreted, blocking intestinal and lungs (bronchial ducts) and causing difficulty in breathing and digestion

Embryonic Stem Cell Research

Organ Transplants

Cloning

Common stages of the “scientific method” – organized approach to solving a problem

1. Observations

2. Asking questions

3. Forming Hypothesis

4. Making predictions

5. Confirming predictions with experiments

6. Drawing conclusions

Observation – the process of obtaining information by using the senses

Asking Questions –observationsraise questions

Hypothesis – an explanation that isbased on observations and thatcan be tested

Prediction – a statement made in advance that expresses the resultsthat will be obtained from testinga hypothesis (if the hypothesisis supported)

WHY?

Confirming predictions by: Performing an experiment

Experiment – a procedure that is carried out under controlled conditions to discover, demonstrate or test a fact, theory or general truth

Controlled experiment – an experiment set up in duplicate in which a single factor is changed in one set up but not the other

Control group – the part of an experiment that does NOT contain the variable

Experimental group - the part of an experiment that contains the variable being tested

Variable – single factor that is isolated and tested in an experiment

Independent variable – the factor that is deliberately manipulated in the experiment

ex.

Dependent variable – in an experiment, the variable that is changed or determined by manipulation (of one or more factors); RESULTS

ex.

Drawing Conclusions

Data is collected and analyzed, and then a conclusion is made as to whether data supports the hypothesis

Hypothesis may be supported or rejected

A Case Study: John Harte’s Study on Tiger Salamanders in the Rockies

Collecting Observations:

John Harte (1984-1988) observed a decline of tiger salamanders in the Rockies

David Bradford (1988) observed that 98% of frogs had disappeared from lakes in the Sequoia and Kings Canyon National Parks

Reported observations to other biologists and found that amphibian elsewhere were declining

Harte had studied salamanders for years: knew their behavior, diet, reproduction, etc.

He visited their ponds regularly and sampled the water.

Rocky Mountain precipitation is acidic

Asking Questions

WHY are the number of salamanders dropping?

WHY is Rocky Mountain precipitation acidic and more acidic in May?

Power plants release pollutants that cause acid precipitation

In the spring, snow melts and releases high levels of acid (all the winters snow)

Forming Hypotheses and Making Predictions

Harte’s 2 hypotheses:

1. Acids formed in the upper atmosphere by pollutants were falling as acid precipitation in

the mountains in the winter snows.

2. Melting snow in spring makes ponds suddenly acidic and harms salamander embryos.

Expected outcome if Harte’s hypothesis is accurate

1. Would find increased acidity in ponds after snow melts.

2. There would be enough acid in ponds to harm embryos.

Confirming Predictions - Experiment

Harte gathered data from many years of observations on the pH of ponds.

pH – a value used to express the acidity or alkalinity (base) of A solution; scaledFrom 0 to 14

Data confirmed the1st prediction:Melting snow causedIncreased acidityIn ponds

Harte performed a controlled experiment

1. Allowed captive salamanders to: lay eggs in regular pond water

2. Collected and divided eggs into 5 groups:

Control group: eggs placed in pond water with neutral pH

4 experimental groups: eggs placed in pond water with different acidic pHVARIABLE IS :_________

3. Found that: Many salamanders never hatched from eggs in

acidic water

Some that did hatch had developmental abnormalities

Drawing Conclusions

Harte’s data supported his hypothesis (for Tiger Salamanders in the Rockies)

Viewing Conclusions in Context

Scientists are working together to determine the cause of the global decline of amphibians

Have found (through more experiments):Chemical pollutants (acid rain) enter through skinHabitat destructionNon-native species outcompeting local populationsAmphibians have a high rate of fatal infections by parasites

Theory –a set of related hypotheses that have been tested and confirmed many times by scientists(an explanation for some phenomenon that is based on observation, experimentation and reasoning)

A theory unites and explains a broad range of observations

Ex. Cell theoryGerm Theory of Disease