Science is a systematic way of acquiring knowledge about the natural world.
Science is not the same as technology.
The majority of technological advances are the result of scientific investigations.
A new technology, such as your cell phone or a new drug, is based on years of scientific investigations.
There are many challenges facing society despite our technological advances.
Some of the critical challenges that scientists are investigating will be explored in this section.
The total number and relative abundance of species, the variability of their genes, and the different ecosystems in which they live are all known as "biodiversity".
Approximately 2.3 million species have been identified and named so far, and the planet has an estimated 8.7 million species.
It is estimated that we are losing hundreds of species every year due to human activities and that as much as 38% of all species may be in danger of extinction before the end of the century.
Climate change is associated with many extinctions.
Many biologists are alarmed about the current rate of extinction and believe it may eventually rival the rates of the five mass extinctions that occurred during our planet's history.
It is believed to be the first mammal species to go extinct as a result of climate change.
Tropical rain forests and coral reefs are home to many organisms.
Human activities are threatening these ecosystems.
Orchids, insects, and monkeys can be found in the canopy of the tropical rain forest.
Coral reefs, which are found just offshore of the continents and islands near the equator, are built up from calcium carbonate skeletons of sea animals.
Some of the world's most colorful fishes can be found in the coral reef.
Coral reefs are in danger as the human population increases.
25% of all coral reefs have been destroyed by human activities in a few decades, and another 30% have been degraded.
Almost three-quarters could be destroyed in 40 years.
Statistics are available for tropical rain forests.
There are many consequences of the destruction of healthy ecosystems.
We depend on them for food, medicines, and raw materials.
The construction of levees and the draining of the natural wetlands of the Mississippi and Ohio rivers have made farmland undesirable.
The destruction of South American rain forests has killed many species that may have yielded the next miracle drug and has decreased the availability of many types of lumber.
We are starting to realize that we need more services from the ecosystems.
The environment of the biosphere is suitable for the continued existence of humans.
Several studies show that ecosystems can't function properly if they aren't biologically diverse.
The concept of biodiversity will be explored in greater detail in Chapters 44 through 47.
Over the past decade, swine flu, Severe Acute Respiratory Syndrome, and Middle East respiratory syndrome have all been in the news.
Emerging diseases are new to humans.
Increased exposure to animals or insect populations may result in some of them.
Changes in human behavior and use of technology can cause diseases.
The consumption of civets, a type of exotic cat, is thought to have caused the emergence of the disease.
The civets may have been exposed to horseshoe bats.
A large air-conditioning system in a hotel caused the emergence of Legionnaires' disease in 1976.
The cooling tower was the water source for the airconditioning system.
The transport of diseases all over the world was previously restricted to isolated communities.
The first cases of the disease were reported in southern China.
By the end of February 2003 there were nine countries/provinces that had been affected by the disease.
Birds are jumping from one host to another, for example.
Birds were thought to be unaffected by the flu before 1997.
The 1997 outbreak was caused by a strain that jumped to humans.
1.5 million chickens were killed to remove the source of the virus.
Every few years new forms of bird flu are discovered.
Reemerging diseases are a concern.
Unlike an emerging disease, a reemerging disease has been known to cause disease in humans for some time, but has not been considered a health risk due to a relatively low level of incidence in human populations.
Reemerging diseases can cause problems.
The outbreak of the disease in West Africa was an excellent example.
Small groups of humans have been affected.
There was a much larger outbreak.
Over 11,000 people were killed by the disease, but the exact numbers may never be known.
The societies of several West African nations have been disrupted by the outbreak.
Both emerging and reemerging diseases can cause health problems for humans.
Scientists investigate not only the causes of these diseases, but also their effects on our bodies and the mechanisms by which they are transmitted.
We will look at the viruses in Chapter 20.
The term climate change refers to changes in the normal cycles of the Earth's climate that may be attributed to human activity.
Climate change is caused by the chemical cycling of the element carbon.
Normally, carbon is removed from the environment.
More carbon dioxide is being released into the atmosphere because of human activities.
In 1850, atmospheric CO2 was around 280 parts per million.
The increase is due to the burning of fossil fuels and the destruction of forests.
The amount of carbon dioxide released into the atmosphere is twice what remains in the atmosphere.
It is believed that most of this is dissolved in the ocean.
Climate change and global warming are caused by the global average carbon dioxide concentration.
Climate change and global warming are causing significant changes in many of the Earth's ecosystems and are one of the greatest challenges of our time.
Some living organisms have the same characteristics.
An example of a metabolism is photosynthesis.
The stimuli help the organisms react to changes in their environment.
The theory of evolution explains how all living organisms evolved from a common ancestor.
There are changes within a population that create new characteristics.
Natural selection can shape species over time and create new ones from existing ones.
The study of evolutionary relationships between species is called systematics.
There are three domains of life.
Tables or graphs are often used to present the results.
The conclusion is whether the results support the hypothesis or not.
The results can be submitted to a scientific publication.
The theory of evolution is related to biology.
Pick the best answer for the question.
A population is the level of organization that includes organisms of the same species.
Natural selection is the process of passing on genetic information.
A species is the least inclusive level of classification.
Natural selection is the process by which evolution occurs.
A hypothesis is published in a scientific journal.
Experiments look at the contribution to the observation.
Two extinct species are H5N1 and MERS.
The video is called BioNow.
An investigator spills dye on a culture plate and notices that thebacteria live despite their exposure to sunlight.
He wants to know if the dye protects against UV light.
There are two groups of culture plates, one with onlybacteria exposed to UV light and the other withbacteria and dye.
The plates have deadbacteria on them.
When you want to grow large tomatoes, you notice that a name-brandfertilizer claims to produce larger plants than a generic brand.
Some of the planets and moons of our solar system may have life on them.
The basic unit of life is the cell.
We need to understand what cells are made of to explore the various functions of the cell.
We are going to take a quick look at chemistry.
Understanding basic chemistry and the nature of water will be the first thing we do.
The structure of the organic molecule that is used to perform the functions of the cell can be found once we have established this chemical foundation of life.
Cells have to acquire energy and materials in order to survive.
The majority of the chapters in this unit help us understand how cells accomplish their goals.
We will look at how the cell's structure relates to its function, either as a single-celled organisms or as part of a multicellular tissue.
The process of cellular reproduction and response to stimuli will be discussed in later units.
Since the cell forms the foundation for all life, your understanding of these concepts will serve you well as you move into the later parts of the text.