1. Introduction: Biology Today
Chapter 1
Introduction: Biology Today

2. What is Biology ? Derived from Greek words:
Life Study of
Biology is the scientific study of life and living organisms.
The study of biology encompasses
a wide scale of size and
a huge variety of life, both past and present.
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3. Biology and Society: Biology All Around Us
We are living in a golden age of biology.
Biology provides exciting breakthroughs changing our culture.
Molecular biology is solving crimes and revealing ancestries.
Ecology helps us address environmental issues such as the causes and consequences of global climate changes
Neuroscience and evolutionary biology are reshaping psychology and sociology.
Biology is the scientific study of life.
Life is structured on a size scale ranging from the molecular to the global.
Biology’s scope stretches across the enormous diversity of life on Earth.
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4. What is Life
Life can not be explained in a simple, one-sentence definition
Life is recognized by what living things do
Life has properties and processes
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5. The Properties of Life Order (Cells and organization)
Regulation and homeostasis
Growth and development
Energy utilization
Response to environmental changes
Reproduction
Biological evolution

6. a) Order: All living things exhibit complex but ordered organization, as seen in the structure of a pinecone.
Figure 1.1ba
b) Regulation: The environment outside an organism may change drastically, but the organism can adjust its internal environment, within limits.
Figure 1.1bb
Order: All living things exhibit complex but complex, ordered organization as seen in the structure of pinecone
Regulation and Homeostasis One way that organisms can respond to environmental variation is to change themselves. The growth of thick fur in the winter time is an example. Living cells & organism regulate their cells and bodies, maintaining relatively stable internal condition (homeostasis). Most mammals and birds maintain constant body temperature in spite of changing environmental temperature whereas reptiles and amphibians tolerate a wider fluctuation in body temperature

7. c) Growth and Development: Information carried by genes controls the pattern of growth and development.
Figure 1.1bc
d) Energy Utilization: Organisms take in energy and use to perform all of life’s activities.
Figure 1.1bd
(c) Growth and development
Growth and development: growth produces more or larger cells, whereas development produces organisms with a defined set of characteristics – series of changes in the state of cells, tissues, organ or organism etc. An early stage chicken embryo is just a ball of cells that all look alike. But as it develops, all of the cells differentiate-some become muscles, some become bone, some become feathers, and so on.
Energy processing. Living things must be able to convert energy from one form to another.
Producers convert the energy from the sun into a form their cells can use. Plants, photosynthetic bacteria and many protists do this by photosynthesis. This is why plants form the base of any food web.
Consumers depend on energy from the producers through cellular respiration. For example-butterflies get energy from plant nectar, birds get energy from eating butterflies, cats get energy from eating birds, and so on.
During every transfer of chemical energy, some is lost as heat.
Decomposers such as fungi, bacteria, and worms, feed on dead organisms, releasing energy that may be used by other organisms. Chemical nutrients continually cycle through an ecosystem.
If cells cannot convert energy into a usable form, the cells will die. If enough cells die, the organism will die. Energy intake, conversion, and flow through the ecosystem are essential for survival.

8. e) Response to the Environment: All organisms respond to environmental stimuli.
Figure 1.1be
Response to the environment. For example, at this time of year in Houston, it is essential to be able to respond appropriately to heat. Some animals sweat, some pant, some hide from the sun, but they all have developed ways to adapt.

9. f) Reproduction: Organisms reproduce their own kind.
g) Evolution: Reproduction underlies the capacity of populations to change (evolve) over time. Evolutionary change has been a central, unifying feature of life since life arose nearly 4 billion years ago.
Figure 1.1bg
Figure 1.1bf
Reproduction: To sustain life over many generations, organisms must reproduce. All living things have DNA as their genetic material. DNA (deoxyribonucleic acid) provides instructions for constructing the body of an organism and for controlling how that body functions. Specific sequences of nitrogenous bases in DNA are called genes.
Growth involves the reproduction of single cells. When a cell divides, it makes a copy of its DNA to pass down to the new cell that is produced.
When an organism reproduces, it also must pass down its DNA.
Regulation of cell division and genetic inheritance is important for all species.
Biological evolution: populations of organisms change over the course of many generations. Evolution results in traits that promote survival and reproductive success. The appearance of katylid insect help them to camouflage with its surroundings and escapes from its predators. They survive to reproduce and if these traits are genetic, they will be passed down to the offspring, so that more individuals in the next generation will have them.

10. Life at Its Many Levels
Biologists explore life at levels ranging from the biosphere to the molecules that make up cells.
Biosphere: consists of all the environments on Earth that support life.
It takes many molecules to build a cell, many cells to make a tissue, multiple tissues to make an organ etc.
At each new level, novel properties emerge, properties that were not part of the components of the preceding level.
The whole is greater than the sum of its parts.
We’ll take a closer look at two biological levels near opposite ends of the size scale: ecosystems and cells.

11. 1 2 3 4 5 6 10 9 7 8 Biosphere Ecosystems Communities Populations
Organisms 6
Organ Systems
and Organs 10
Molecules and Atoms 9
Organelles 7
Tissues
Atom
Nucleus 8
Cells
Figure 1.2-3

12. 1
Biosphere
Figure 1.2a
Figure 1.2 Zooming in on life (part 1) 12

13. 2 3 13 Ecosystems Communities Figure 1.2b
Figure 1.2 Zooming in on life (part 2) 13

14. 4 5 14 Populations Organisms Figure 1.2c
Figure 1.2 Zooming in on life (part 3) 14

15. 6 15 Organ Systems and Organs Figure 1.2d
Figure 1.2 Zooming in on life (part 4) 15

16. 7
Tissues
Figure 1.2e
Figure 1.2 Zooming in on life (part 5) 16

17. 8 9 17 Nucleus Cells Organelles Figure 1.2f
Figure 1.2 Zooming in on life (part 6) 17

18. 10 18 Atom Molecules and Atoms Figure 1.2g
Figure 1.2 Zooming in on life (part 7) 18

19. Life at many levels Atoms Molecules and macromolecules Cells Tissues
Organs
Organism
Population
Community
Ecosystem
Biosphere
If you follow the figure in opposite direction, you can see the life’s hierarchy from molecules to the biosphere. At each new level, novel properties emerge, properties that were not part of the components of the preceding level. These are called Emergent Properties, the important theme of biology.
The whole is greater than the sum of its parts capture the idea. The emergent properties of whole result from the specific arrangements and interactions of the component parts.

20. Ecosystems Each organism interacts continuously with its environment.
Organisms interact continuously with the living (biotic) and nonliving (abiotic) factors in the environment.
All the living organisms in a specific area, along with all of the nonliving factors with which they interact, form an ecosystem.
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21. Ecosystems The dynamics of any ecosystem depend on two main processes:
recycling of chemical nutrients and
flow of energy.
Within ecosystems
nutrients are recycled but
energy flows through.
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22. Figure 1.3 Nutrient and energy flow in an ecosystem
Outflow
of heat
energy
Inflow
of light
energy
Consumers
(animals)
Chemical
energy
(food)
Producers
(plants and other
photosynthetic
organisms)
Decomposers
(in soil)
Cycling of
nutrients
Figure 1.3 Nutrient and energy flow in an ecosystem
Figure 1.3 Nutrient and energy flow in an ecosystem
Life does not exist in vacuum. Each organism interacts continuously with its environments which include other organisms and nonliving factors. Example, tree.
Nutrients are recycled within an ecosystem, whereas energy flows through ecosystem (the actions of decomposers ensures that nutrients are recycled within an ecosystem)
In contrast to recycling nutrients, an ecosystem gains and loses energy constantly. 22

23. Cells and Their DNA
Cells are the lowest level of structure that can perform all activities required for life.
All organisms are composed of cells.
Cells are the subunits that make up multicellular organisms such as humans and trees.
All cells share many characteristics.
All cells are enclosed by a membrane that regulates the passage of materials between the cell and its surroundings.
Every cell uses DNA as its genetic information.
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Now, come back to the lowest level of biological organization, the cell which has a special place in the hierarchy – it is the level at which the properties of life emerge, the lowest level of structure that can perform all activities required for life. 23

24. The prokaryotic cell is simpler and smaller and contains NO MEMBRANES around the nucleus or organelles.
Bacteria have prokaryotic cells.

25. Cells and Their DNA We can distinguish two major types of cells:
The prokaryotic cell is
simpler and usually smaller and
characteristic of bacteria.
The eukaryotic cell is larger, more complex, and
subdivided by internal membranes into different functional compartments called organelles and
contains MEMBRANE-ENCLOSED nucleus and
the nucleus is the largest organelle in most eukaryotic cells
found in plants and animals.
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26. Cells and Their DNA We can distinguish two major types of cells:
The prokaryotic cell is
simpler and usually smaller and
characteristic of bacteria.
The eukaryotic cell is larger, more complex, and contains MEMBRANE-ENCLOSED nucleus and organelles.
The nucleus is the largest organelle in most eukaryotic cells.
subdivided by internal membranes into different functional compartments called organelles and
found in plants and animals.
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27. Two main kinds of cells: prokaryotic and eukaryotic
Prokaryotic cell
(bacterium)
Eukaryotic cell •
Smaller
Simpler structure
DNA concentrated in
nucleoid region, which is
not enclosed by membrane
Lacks most organelles
Organelles •
Larger
More complex
structure
Nucleus enclosed
by membrane
Contains many
types of organelles
Nucleoid
region
Nucleus
Colorized TEM
Figure 1.4
Figure 1.4 Two main kinds of cells: prokaryotic and eukaryotic 27

28. The language of DNA
All cells use DNA as the chemical material of genes.
Genes are the units of inheritance that transmit information from parents to offspring.
The language of DNA
is common to all organisms and
contains just four letters A, G, C, T
The entire book of genetic instructions that an organism inherits is called its genome.
An average-sized gene may be hundreds or thousands of chemical “letters” long.
The nucleus of each human cell packs a genome that is about 3 billion chemical letters long.
Though very much different in structural complexity, both cells have much common at the molecular level. Most importantly, all cells use DNA as the chemical material of genes – the discrete units of hereditary information.
Of course, bacteria and humans different genes, but that information is encoded in a chemical language common to all organism.
Gene encodes the information in its specific sequences of nucleotides with 4 of its building blocks.

29. 29 The four chemical building blocks of DNA A DNA molecule Figure 1.5
Figure 1.5 The language of DNA 29

30. DNA technology in the Drug Industry
Genetic engineering and biotechnology have allowed us to manipulate the DNA and genes of organisms.
Bacteria can make insulin because a gene for insulin production was transplanted into their DNA.
The bacteria can make insulin because a gene for human insulin production has been transplanted into their DNA. It is possible because biological information is written in the universal chemical language of DNA

31. Life in Its Diverse Forms
Diversity is the hallmark of life.
The diversity of known life includes 1.8 million species.
Estimates of the total diversity range from 10 million to over 100 million species.
This is a small sample of biological diversity. Estimates of total no of species range from million. New species are added to the list everyday.

32. Grouping Species: The Basic Concept
Biodiversity can be beautiful but overwhelming.
Taxonomy is the branch of biology that names and classifies species.
It formalizes the hierarchical ordering of organisms.
The three domains of life are
Bacteria
Archaea
Eukarya
Bacteria and Archaea (prokaryotic cells); Eukarya (eukaryotic cells).
Biological diversity is complex but we tend to categorize them into smaller groups. Grouping species that are similar is quite natural for us.

33. 33 DOMAIN BACTERIA Kingdom Plantae DOMAIN ARCHAEA DOMAIN EUKARYA
Figure 1.8
DOMAIN
BACTERIA
Kingdom Plantae
DOMAIN
ARCHAEA
Kingdom Fungi
DOMAIN EUKARYA
Kingdom Animalia
Protists (multiple kingdoms)
Figure 1.8 The three domains of life
The Domain Archaea was recognized recently. 20th century, living things were classified as plant or an animal.
1950s and 1960s, this system failed to accommodate the fungi, protists, and bacteria.
By the 1970s, a system of Five Kingdoms, fundamental distinction between the prokaryotic bacteria and the four eukaryotic kingdoms (plants, animals, fungi, & protists).
Late 1970s the group Archaea was discovered by Dr. Carl Woese and colleagues at the University of Illinois while studying relationships among the prokaryotes using DNA sequences, found that there were two distinctly different groups.
Archaea = Those "bacteria" that lived at high temperatures or produced methane clustered together as a group well away from the usual bacteria and the eukaryotes.
Because of this vast difference in genetic makeup, Woese proposed that life be divided into three domains: Eukaryota, Eubacteria, and Archaebacteria. 33

34. Bacteria and Archaea have prokaryotic cells
DOMAIN
BACTERIA
DOMAIN
ARCHAEA
Figure 1.8a
Figure 1.8 The three domains of life (part 1) 34

35. Domain Eukarya Eukarya includes Kingdom Plantae Kingdom Fungi
Kingdom Animalia
Protists (multiple kingdoms)
Protists are
generally single celled.
Most plants, fungi, and animals are multicellular
Kingdom Plantae
Kingdom Fungi
Kingdom Animalia
Protists multiple kingdoms LM

36. Mode of Nutrition
These three multicellular kingdoms are distinguished by how they obtain food.
Plants produce their own sugars and other foods by photosynthesis.
Fungi are mostly decomposers, digesting dead organisms.
Animals obtain food by eating and digesting other organisms.

37. Test Yourself
Match the following description to its most likely domain and/or kingdom
a. A foot-tall organism capable of producing its own food from sunlight
Bacteria
b. A microscopic, simple, nucleus-free organism found growing in a riverbed
2. Eukarya/Animalia
c. An inch-tall organism growing on the forest floor that consumes material from dead leaves
3. Eukarya/fungi
d. A thimble-sized organism that feeds on algae growing in a pond
4. Eukarya/Plantae

38. Unity in the Diversity of Life
Diverse forms of life in diverse environments
how, in adapting to their environments, organisms have developed different traits
Underlying the diversity of life is a striking unity, especially at the lower levels of structure.
For example, all life uses the genetic language of DNA.
All life displays a common set of characteristics
all organisms have the same types of DNA molecules
many seemingly unrelated organisms share similar features
Biological evolution accounts for this combination of unity and diversity.
Underlying the diversity of life is a striking unity, especially at the lower levels of biological organization
The universal genetic language

39. EVOLUTION: BIOLOGY’S UNIFYING THEME
Life evolves.
Each species is one twig of a branching tree of life extending back in time through ancestral species more and more remote.
Species that are very similar, such as the brown bear and polar bear, share a more recent common ancestor.
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40. polar bear and brown bear
Giant panda
Spectacled bear
Ancestral
bear
Sloth bear
Sun bear
Common ancestor
of all modern bears
American black bear
Asiatic black bear
Common ancestor of
polar bear and brown bear
Polar bear
Brown bear 30 25 20 15 10 5
Millions of years ago
Figure 1.10
This tree is based on both the fossil record and a comparison of DNA sequences among modern bears.

41. The Darwinian View of Life
The evolutionary view of life came into focus in 1859 when Charles Darwin published The Origin of Species.
Darwin’s book developed two main points:
Descent with modification
Natural selection
The evolutionary view of life become popular after Darwin published his book, The origin of species. Darwin’s book developed two main points:
Descent with modification: the diversity of bears is based on different modifications of a common ancestor from which all bears descended
Natural selection: he proposed a mechanism for descent with modification and called this process, natural selection.

42. Natural Selection
Darwin was struck by the diversity of animals on the Galápagos Islands.
He thought that adaptation to the environment and the origin of new species were closely related processes.
As populations separated by a geographic barrier adapted to local environments, they became separate species.
Darwin synthesized the theory of natural selection from two observations
Darwin gathered important evidence for his theories during the world voyage.
Darwin was struck by the diversity of animals on the Galápagos Islands. The finches in Galapagos Island probably descended from one type of ancestor and then, due to isolation and through chance, different climates and natural forces such as food availability and type, they evolved into thirteen different types of finches.
He thought that adaptation to the environment and the origin of new species were closely related processes.
Natural selection is, that the strongest survive and propagate and therefore increase the strength of the species.

43. Darwin’s Inescapable Conclusion
Observation 1: Overproduction and competition
Observation 2: Individual variation
Conclusion: Unequal reproductive success
It is this unequal reproductive success that Darwin called natural selection.
The product is adaptation, the accumulation of favorable variation in a population over time
Example, fur color in polar and brown bear
Observation 1: Overproduction and competition
Any population of a species has the potential to produce far more offspring than the environment can possibly support with available resources such as food and shelter.
This overproduction leads to competition among the varying individuals of a population for these limited resources
Observation 2: Individual variation
No two individuals in a population are exactly alike. Individuals in a population of any species vary in many inherited traits.
Example, polar and brown bears, as closely related as they are, ech display an evolutionary adaptation that resulted from natural selection operating in their respective environment.
Conclusion : in the struggle for existence, those individuals with trait best suited to the local environment will, on average, have the greatest reproductive success. They will leave greatest number of surviving, fertile offspring.

44. Natural selection is the mechanism of evolution
Enhances the reproductive success of individuals with beneficial traits 1
Population with varied inherited traits 2
Elimination of individuals with certain traits 3
Reproduction of survivors 4
Increasing frequency of traits that enhance
survival and reproductive success
Figure 1.12
Population with varied inherited traits: initally, the population varies extensively in the coloration of individual beetles, from very light gray to charcoal.
Elimination of individuals with certain traits: for hungry birds that prey on the beetles, it is easiest to spot the lighter ones.
Reproduction of survivors: The selective predation favors survival and reproductive success of the darker beetles. Thus, genes for dark color are passed along to the next generation in greater frequency than genes for light color.
Increasing frequency of traits that enhance survival and reproductive success : Generation after generation, the beetle population adapts to its environment through natural selection

45. Population with varied inherited traits. Initially, the pop
Population with varied inherited traits. Initially, the pop. varies extensively in the coloration
of ind. beetles, from light gray to charcoal.
Elimination of individuals with certain traits. For hungry birds that prey on beetles, it is
easiest to spot the beetles that are lightest in color.
Reproduction of survivors. The selective predation favors survival and reproduction success
of the darker beetles. Thus, genes for the dark color are passed along to next gen. in greater
frequency.
Increasing frequency of traits that enhance survival and reproductive success.
Generation after gen., the beetles pop. adapts to its environment through natural selection.
Figure 1.12

46. Observing Artificial Selection
Artificial selection is the selective breeding of domesticated plants and animals by humans.
In artificial selection, humans do the selecting instead of the environment.
a Vegetables descended
from wild mustard
Cabbage from
terminal bud
Brussels
sprouts from
lateral buds
Kohlrabi
from stem
Kale from leaves
Broccoli from
flower and
stems
Cauliflower
from flower
clusters
Wild mustard
In artificial selection humans were substituting for the environment in screening the heritable traits of populations.
The humans customized crop plants through many generations of artificial selection by selecting different parts of the plant to accentuate as food.

47. (b) Domesticated dogs descended from wolves Gray wolves
Figure 1.13b
The power of selective breeding is apparent in our pets, which have been bred for fancy and for utility.

48. THE PROCESS OF SCIENCE
The word science is derived from Latin verb meaning “to know.”
Science is a way of knowing.
Science developed from people’s curiosity about themselves and the world around them.
Discovery Science
Enables us to describe life at its many levels.
Verifiable observations and measurements are the data of discovery science.
Discovery science can lead to important conclusions based on a type of logic called inductive reasoning.
An inductive conclusion is a generalization that summarizes many concurrent observations.
Example all organisms are made of cells
all organisms are made of cells – this induction was based on 2 centuries of biologists discovering cells in every biological specimen they observed with mocroscope.

49. Figure 1.14a
Figure 1.14 Careful observation and measurement: the raw data for discovery science (part 1)
Figure 1.14 Careful observation and measurement: the raw data for discovery science (part 2) 49

50. Hypothesis-Driven Science
The scientific method consists of a series of steps.
The key element of the scientific method is hypothesis- driven science.
A hypothesis is a proposed explanation for a set of observations—an idea on trial.
Once a hypothesis is formed, an investigator can use deductive logic to test it.
In deduction, the reasoning flows from general to specific.
In the process of science, the deduction usually takes the form of predictions about experimental results.
Then the hypothesis is tested by performing an experiment to see whether results are as predicted.
This deductive reasoning takes the form of “If…then” logic.
The observation of discovery science stimulates us to ask questions and seek explanations. Such investigation make use of what is called the scientific method

51. Applying the scientific method to a common problem
Observation
The remote
doesn’t
work.
Hypothesis
The
batteries
are dead.
Prediction
With new
batteries, it
will work.
Question
What’s
wrong?
Figure
Figure 1.15 Applying the scientific method to a common problem (step 1) 51

52. 52 Observation The remote doesn’t work. Hypothesis The batteries
are dead.
Prediction
With new
batteries, it
will work.
Question
What’s
wrong?
Experiment
Replace
batteries.
Experiment
supports
hypothesis;
make more
predictions
and test.
Figure
Figure 1.15 Applying the scientific method to a common problem (step 2) 52

53. 53 Experiment does not support hypothesis. Revise. Observation
The remote
doesn’t
work.
Hypothesis
The
batteries
are dead.
Prediction
With new
batteries, it
will work.
Question
What’s
wrong?
Experiment
Replace
batteries.
Experiment
supports
hypothesis;
make more
predictions
and test.
Figure
Figure 1.15 Applying the scientific method to a common problem (step 3) 53

54. Test Yourself
If you are sitting in HCCS cafeteria and watching how many students are eating pizza or burger during lunch time, what kind of science are you performing?
If you come up with a tentative explanation for their dietary behavior and then test your idea, what kind of science you are performing?

55. The Process of Science: Are Trans Fats Bad for You?
Case study is an in-depth examination of an actual investigation.
Dietary fat comes in different forms.
Trans fat is a non-natural form produced through manufacturing processes.
Trans fat
Adds texture
Increases shelf life
Is inexpensive to prepare
A study of 120,000 female nurses found that high levels of trans fat nearly doubled the risk of heart disease.
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One way to better understand how the process of science can be applied to real-world problems is to examine a case study

56. The Process of Science: Are Trans Fats Bad for You?
A hypothesis-driven study published in 2004
Started with the observation that human body fat (adipose tissue) retains traces of consumed dietary fat.
Asked the question: Would the adipose tissue of heart attack patients be different from a similar group of healthy patients?
Formed the hypothesis that it would be
predicted that healthy patients’ body fat would contain less trans fat than the body fat in heart attack victims.

57. The Process of Science: Are Trans Fats Bad for You?
The researchers set up an experiment to determine the amounts of fat in the adipose tissue of 79 patients who had a heart attack.
They compared these patients to the data for 167 patients who had not had a heart attack.
This is an example of a controlled experiment, in which the control and experimental groups differ only in one variable—the occurrence of a heart attack.
The results showed significantly higher levels of trans fat in the bodies of the heart attack patients.

58. Trans fats in adipose tissue (g trans fat per 100 g total fat)
2.0
1.77
1.48
1.5
Trans fats in adipose tissue
(g trans fat per 100 g total fat)
1.0
0.5
Heart attack
patients
Control
group
Figure 1.16
Figure 1.16 Levels of trans fats

59. Theories in Science
What is a scientific theory, and how is it different from a hypothesis?
A theory is much broader in scope than a hypothesis.
Theories only become widely accepted in science if they are supported by an accumulation of extensive and varied evidence.
For example
Hypothesis: “white fur is an evolutionary adaptation that helps polar bears survive in an arctic habitat”.
Theory: “Adaptations evolve by natural selection”

60. The Culture of Science
Scientists build on what has been learned from earlier research.
They pay close attention to contemporary scientists working on the same problem.
Cooperation and competition characterize the scientific culture.
Scientists check the conclusions of others by attempting to repeat experiments.
Scientists are generally skeptics.
Science has two key features that distinguish it from other forms of inquiry. Science
depends on observations and measurements that others can verify and
requires that ideas (hypotheses) are testable by experiments that others can repeat.
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61. Science, Technology, and Society
Science and technology are interdependent.
New technologies advance science.
Scientific discoveries lead to new technologies.
For example, the discovery of the structure of DNA about 60 years ago led to a variety of DNA technologies.
Technology has improved our standard of living in many ways, but it is a double-edged sword.
Technology that keeps people healthier has enabled the human population to double to 7 billion in just the past 40 years.
The environmental consequences of this population growth may be devastating.
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62. Evolution Connection: Evolution in Our Everyday Lives
Antibiotics are drugs that help cure bacterial infections.
When an antibiotic is taken, most bacteria are typically killed.
Those bacteria most naturally resistant to the drug can still survive.
Those few resistant bacteria can soon multiply and become the norm and not the exception.
The evolution of antibiotic-resistant bacteria is a huge problem in public health.
Antibiotics are being used more selectively.
Many farmers are reducing the use of antibiotics in animal feed.
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63. Evolution Connection: Evolution in Our Everyday Lives
It is important to note that the adaptation of bacteria to an environment containing an antibiotic does not mean that the drug created the antibiotic resistance. Instead, the environment screened the heritable variations that already existed among the existing bacteria.
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