Studying%20Life

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Studying Life
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1 Studying Life

• 1.1 What Is Biology?
• 1.2 How Do Biologists Investigate Life?
• 1.3 Why Does Biology Matter?

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1 Studying Life

• More than one-third of the worlds amphibian
  species are threatened with extinction.
• Tyrone Hayes studies one of the threats to
  amphibiansagricultural pesticides such as
  atrazine, which impact breeding and reproduction.

Opening Question Could atrazine in the
environment affect species other than amphibians?
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1.1 What Is Biology?

• Biology is the scientific study of living things
  (organisms).
• Living things are all descended from a common
  origin of life that occurred almost 4 billion
  years ago.

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Figure 1.1 The Many Faces of Life (Part 1)
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Figure 1.1 The Many Faces of Life (Part 2)
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1.1 What Is Biology?

• Characteristics of living organisms
• Made of a common set of chemical components
  carbohydrates, fatty acids, nucleic acids, amino
  acids
• Most are made of cells enclosed by plasma
  membranes
• Convert molecules from their environment into new
  biological molecules

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1.1 What Is Biology?

• Extract energy from the environment and use it to
  do biological work
• Contain genetic information that uses a universal
  code to specify proteins
• Share similarities among a fundamental set of
  genes, and replicate this genetic information
  when reproducing

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1.1 What Is Biology?

• Exist in populations that evolve through changes
  in frequencies of genetic variants over time
• Self-regulate their internal environment,
  maintaining conditions that allow them to survive

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1.1 What Is Biology?

• The diverse organisms alive today all originated
  from one life form.
• If life had multiple origins, we would not expect
  to see such striking similarities in gene
  sequences, genetic code, and amino acids.

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1.1 What Is Biology?

• Earth formed 4.6 to 4.5 billion years ago but it
  was 600 million years or more before life
  evolved.
• The history of Earth can be pictured as a 30-day
  month.

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Figure 1.2 Lifes Timeline
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1.1 What Is Biology?

• Complex biological molecules probably arose
  through random physical associations of
  chemicals.
• Experiments simulating conditions on early Earth
  show that this is possible, and even probable.

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1.1 What Is Biology?

• Nucleic acids were essential molecules that
  could reproduce themselves and serve as templates
  for synthesis of proteins.
• Another step was enclosure of biological
  molecules by membranes. This created an internal
  environment in which reactions could be
  controlled and integrated.

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Figure 1.3 Cells Are Building Blocks for Life
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1.1 What Is Biology?

• For 2 billion years, life consisted of single
  cells called prokaryotes.
• The two main groups of prokaryotes emerged early
  bacteria and archaea.

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1.1 What Is Biology?

• Some early prokaryotes began to live in close,
  interdependent relationships and eventually
  merged to form a third major lineage of life, the
  eukaryotes.
• Eukaryotic cells have internal membranes that
  enclose specialized organelles within their
  cells, including the nucleus, which contains the
  genetic material.

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1.1 What Is Biology?

• At some point, eukaryotic cells did not separate
  after division and started living as colonies.
• This opened the way for some cells to specialize
  for certain functions, which led to multicellular
  organisms.

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1.1 What Is Biology?

• About 2.5 billion years ago, photosynthesis
  changed the nature of life on Earth.
• This process transforms sunlight energy into
  biological energy.
• Photosynthesis is the basis of most of life on
  Earth it provides food for other organisms.

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1.1 What Is Biology?

• Early photosynthetic cells were probably similar
  to cyanobacteria (prokaryotes).
• The atmosphere of early Earth had no O2, but it
  began to increase as photosynthetic prokaryotes
  increased.
• Organisms that could tolerate O2 proliferated.

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Figure 1.4 Photosynthetic Organisms Changed
Earths Atmosphere
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1.1 What Is Biology?

• Abundant O2 opened up new avenues of evolution
  because aerobic metabolism is more efficient than
  anaerobic metabolism and allows organisms to grow
  larger.

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1.1 What Is Biology?

• O2 in the atmosphere also allowed life to move
  onto land.
• Accumulating O2 led to formation of the ozone
  (O3) layer, which absorbs damaging UV radiation.
• By 500 million years ago, there was enough ozone
  for organisms to leave the protection of the
  water.

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1.1 What Is Biology?

• Genome the sum total of all the DNA in a cell.
• DNA consists of repeating subunits called
  nucleotides.
• Gene a specific segment of DNA that contains
  information for making a protein.

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Figure 1.5 DNA Is Lifes Blueprint
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1.1 What Is Biology?

• All the cells of a multicellular organism have
  the same genome, yet different cells have
  different functions and structures.
• Different cells are expressing different parts of
  the genome.

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1.1 What Is Biology?

• The genome must be replicated when cells
  reproduce.
• The process is not perfect errors are called
  mutations.
• Discovery of DNA and how it functions transformed
  biological science.

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1.1 What Is Biology?

• A population is a group of individuals of the
  same type of organismthe same speciesthat
  interact with one another.
• Evolution acts on populations it is change in
  the genetic makeup of populations through time.

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1.1 What Is Biology?

• Evolution is the major unifying principle of
  biology.
• Charles Darwin compiled factual evidence for
  evolution.
• He argued that differential survival and
  reproduction among individuals in a population
  (natural selection) could account for much of the
  evolution of life.

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1.1 What Is Biology?

• Darwin proposed that all organisms are descended
  from a common ancestor.
• Some mutations give rise to changes in organisms
  genetic variants may change in frequency in the
  population the population evolves.

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1.1 What Is Biology?

• Darwin knew that humans select for specific
  traits in domesticated animals (artificial
  selection) the same process could operate in
  nature (natural selection).
• Only a small percentage of an individuals
  offspring survive to reproduce thus traits that
  confer an increase in the probability of survival
  and reproduction will spread in the population.

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1.1 What Is Biology?

• Natural selection leads to adaptations
  structural, physiological, or behavioral traits
  that enhance an organisms chances of survival
  and reproduction.

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Figure 1.6 Adaptations to the Environment
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1.1 What Is Biology?

• As populations become isolated and evolve
  differences, they are eventually considered
  different species.
• Species that share a recent evolutionary history
  are generally more similar to each other than
  species that share a more distant ancestor.

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1.1 What Is Biology?

• Each species has a distinct scientific name, a
  binomial
• Genus name species name
• Example Homo sapiens
• A genus is a group of species that share a recent
  common ancestor.

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1.1 What Is Biology?

• Our understanding of evolutionary relationships
  has been greatly enhanced by molecular techniques
  such as the ability to sequence genomes.
• A phylogenetic tree illustrates the evolutionary
  histories of different groups of organisms.

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Figure 1.7 The Tree of Life
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1.1 What Is Biology?

• Three domains of life
• Bacteria (prokaryotes)
• Archaea (prokaryotes)
• Eukarya (eukaryotes)

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1.1 What Is Biology?

• For more than half of Earths history, all life
  was unicellular. Unicellular species remain
  ubiquitous and highly successful in the present.
• Multicellular Eukarya (plants, animals, and
  fungi) evolved from protistsunicellular
  microbial eukaryotes.

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1.1 What Is Biology?

• Cells became specialized in multicellular
  organisms a biological hierarchy emerged
• Differentiated cells are organized into tissues.
  Different tissue types form organs (e.g., a
  heart) and organs are grouped into organ systems.

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Figure 1.8 Biology Is Studied at Many Levels of
Organization (1)
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1.1 What Is Biology?

• A group of individuals of the same species is a
  population.
• Populations of all the species that live and
  interact in a defined area are called a
  community.
• Communities together with their abiotic
  (nonliving) environment constitute an ecosystem.

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Figure 1.8 Biology Is Studied at Many Levels of
Organization (2)
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1.1 What Is Biology?

• Individuals may compete with each other for
  resources
• Or they may cooperate (e.g., in a termite
  colony).
• Plants also compete for light and water, and many
  form complex partnerships with fungi, bacteria,
  and animals.

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1.1 What Is Biology?

• The interactions of plant and animal species are
  major evolutionary forces that produce
  specialized adaptations.
• Species interactions with one another and with
  their environment is the subject of ecology.

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1.1 What Is Biology?

• Organisms acquire nutrients from their
  environment.
• Nutrients supply energy and materials for
  biochemical reactions.
• Some reactions break nutrient molecules into
  smaller units, releasing energy for work.

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1.1 What Is Biology?

• Examples of cellular work
• Movement of molecules or the whole organism
• Synthesisbuilding new complex molecules from
  smaller chemical units
• Electrical work of information processing in
  nervous systems

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Figure 1.9 Energy Can Be Used Immediately or
Stored
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1.1 What Is Biology?

• Organisms must regulate their internal
  environment, made up of extracellular fluids.
• Maintenance of the narrow range of conditions
  that support survival is known as homeostasis.

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1.2 How Do Biologists Investigate Life?

• Scientific investigations are based on
  observation, data, experimentation, and logic.
• Observation has been improved by new
  technologies.
• Information, or data, must be quantified using
  mathematical and statistical methods.

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Figure 1.10 Scientific Methodology
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1.2 How Do Biologists Investigate Life?

• The hypothesisprediction approach traditionally
  has five steps
• 1. Making observations
• 2. Asking questions
• 3. Forming hypotheses, or tentative answers
• 4. Making predictions based on the hypotheses
• 5. Testing the predictions

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1.2 How Do Biologists Investigate Life?

• Inductive logic uses observations or facts to
  develop a tentative answer or hypothesis.
• Deductive logic is used to predict what facts
  would also have to be true to be compatible with
  the hypothesis.
• Experiments can then be designed to test the
  prediction.

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1.2 How Do Biologists Investigate Life?

• Controlled experiments manipulate one or more of
  the factors being tested.
• The factor, or variable, is manipulated in an
  experimental group and the results are compared
  with data from an unmanipulated control group.

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Figure 1.11 Controlled Experiments Manipulate a
Variable (Part 1)
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Figure 1.11 Controlled Experiments Manipulate a
Variable (Part 2)
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1.2 How Do Biologists Investigate Life?

• One variable is manipulated while all others are
  held constant.
• Independent variable the variable being
  manipulated.
• Dependent variable the response that is measured.

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1.2 How Do Biologists Investigate Life?

• Comparative experiments look for differences
  between samples or groups.
• The variables can not be controlled data are
  gathered from different sample groups and
  compared.

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Figure 1.12 Comparative Experiments Look for
Differences among Groups (Part 1)
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Figure 1.12 Comparative Experiments Look for
Differences among Groups (Part 2)
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1.2 How Do Biologists Investigate Life?

• Statistical methods help scientists determine if
  differences between groups are significant.
• Statistical tests start with a null hypothesis
  that no differences exist.

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1.2 How Do Biologists Investigate Life?

• Statistical methods tell us the probability of
  getting a particular result by chance, even if
  the null hypothesis is true.
• Statistical methods eliminate the possibility
  that results are due to random variation.

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1.2 How Do Biologists Investigate Life?

• Model systems using one type of organism to
  understand others.
• This is possible because all life is related by
  descent from a common ancestor, shares a genetic
  code, and consists of similar building
  blockscells.

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1.2 How Do Biologists Investigate Life?

• Arabidopsis thaliana, a relative of the mustard
  plant, is used to understand the genetics of
  plant development.
• Knowledge of animal development, including
  humans, has come from work on sea urchins, frogs,
  chickens, roundworms, mice, and fruit flies.

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1.2 How Do Biologists Investigate Life?

• Distinguishing science and nonscience
• Scientific hypotheses must be testable and have
  the potential of being rejected.
• Science depends on evidence that comes from
  reproducible and quantifiable observations.

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1.2 How Do Biologists Investigate Life?

• Religious or spiritual explanations of a natural
  phenomenon are not testable and therefore are not
  science.
• Science does not necessarily say that religious
  beliefs are wrong they are simply not part of
  the world of science because many religious
  beliefs are not testable using scientific methods.

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1.2 How Do Biologists Investigate Life?

• Many scientific advances that contribute to human
  welfare also raise ethical issues.
• Scientific knowledge allows us to do many things,
  such as use stem cells to repair our bodies, but
  it cannot tell us whether or not we should do so.

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1.3 Why Does Biology Matter?

• Understanding biological principles is essential
  to our lives and for maintaining the functioning
  of Earth as we know it and depend on it.

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1.3 Why Does Biology Matter?

• Modern agriculture depends on biology.
• Knowledge of plant biology has increased food
  production, which has allowed the planet to
  support a larger human population.
• New strains of crop plants are developed to
  resist pests or tolerate drought.

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Figure 1.13 A Green Revolution
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1.3 Why Does Biology Matter?

• Biology is the basis of medical practice.
• Biological research explains how organisms work
  and why they develop problems and diseases.
• We now understand that some diseases result from
  genetic variations.

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1.3 Why Does Biology Matter?

• Evolutionary principles help us to understand how
  disease organisms evolve resistance to our drugs
  and how influenza virus evolves so quickly that
  we need new vaccines every year.

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Figure 1.14 Medical Applications of Biology
Improve Human Health
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1.3 Why Does Biology Matter?

• Biology can inform public policy.
• Our newfound ability to decipher and manipulate
  genomes raises ethical and policy issues.
• Biologists are called on to advise government
  agencies on many issues, such as overfishing of
  bluefin tuna.

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Figure 1.15 Bluefin Tuna Do Not Recognize
Boundaries
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1.3 Why Does Biology Matter?

• Biology is crucial for understanding ecosystems.
• Human activities are resulting in unprecedented
  rates of change in Earth systems.
• Increasing atmospheric CO2 is responsible for
  climate warming, which is contributing to species
  extinctions and spread of diseases.

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Figure 1.16 A Warmer World
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1.3 Why Does Biology Matter?

• Biology helps us understand and appreciate
  biodiversity.
• Observing the living world motivates many
  biologists to learn more.
• Understanding the natural history of organisms
  provides a stronger basis for framing hypotheses.

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Figure 1.17 Discovering Life on Earth
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1.3 Why Does Biology Matter?

• Most humans engage in activities that depend on
  biodiversity, such as bird watching, gardening,
  hunting, fishing, hiking, and camping.
• These interests support the growing industry of
  eco-tourism.
• Learning about biology enhances our enjoyment of
  these activities.

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1 Answer to Opening Question

• An important aspect of science is replication of
  results.
• Many other investigators have now tested the
  feminizing effects of atrazine on many amphibian
  and vertebrate species.
• Molecular mechanisms of atrazines effects are
  similar in amphibians, fish, reptiles, and human
  cell cultures.