How Do Biologists Study Life

1
Chapter 1

• How Do Biologists Study Life?

2
Key Questions

• How do biologists come up with questions and then
  answer them?
• How do biologists use statistics to plan and
  evaluate experiments?
• How are all organisms alike?
• Why are all the members of a species alike?
• How do organisms become different?

3
What is Science?

• Asking questions about the world around us
• Biology is asking about life How does it work?
  How can we modify it? curing diseases
• Use scientific method to answer questions

4
Scientific Method

• The scientific method is the way scientists
  approach a question
• Focus on a single answerable question
  reductionism
• Observation, either with our senses or
  instruments
• Create a hypothesis or model a guess of how
  things work that also makes predictions
• Test the hypothesis, are predictions right?

5
Testable Hypothesis

• Scientific method only works on testable
  hypotheses
• Testable if experiments could disprove it, if it
  were incorrect
• If testable, hypothesis will make predictions
  that can be tested by experiment

6
Experiments

• Procedure carried out under controlled conditions
• Controls a version of the experiment that is the
  same except for the variable being tested minus
  drug, for example
• Replicates, because each organism is unique
  Then compare averages with statistics

7
Results

• Results of scientific tests may support a
  hypothesis, but cannot prove it
• Results may disprove a hypothesis
• May require redesign of experiment

8
Reductionism and Emergent Properties
9
Reductionism and Emergent Properties
10
Theory

• A group of related hypotheses that have withstood
  rigorous experimental testing.
• How does this differ from the idea of theory
  held by the general public?

11
Living Organisms

• What is life? Living things have these things in
  common
• Are organized
• Are made of cells
• Perform chemical reactions
• Obtain energy
• Respond to environment
• Change over time (growth)
• Reproduce
• Have common evolutionary history

12
Thinking About the Possibilities

• Which of the following is alive and why?
• A neutered dog or cat that cannot reproduce.
• A gasoline-powered chain saw takes in energy,
  metabolizes the fuel, responds to stimuli (it
  will start if you pull the cord). They even
  change with time, their teeth getting duller and
  their paint chipping.
• Some adult insects never eat. They just lay eggs
  and die. Since they are not obtaining energy from
  their surroundings, are they alive?

13
Regulation

• Organisms must create barriers between the
  outside world and the organism skin, cell
  membrane
• Resist change maintain homeostasis
• Detecting change
• Counteracting change
• Animals regulate temperature, thirst, hunger,
  sperm production

14
Cell Types

• Basic building blocks of organisms
• 100s of kinds of cells just in humans
• Two basic types
• Prokaryotic no nuclei or other membrane-bound
  organelles all bacteria are prokaryotes
• Eukaryotic, have nuclei and other membrane-bound
  organelles plants, animals, fungi, and protists
  are all eukaryotes

15
Classification of Organisms

• Three domains
• Archaea
• Eubacteria
• Eukarya, has 4 kingdoms
• Plantae
• Animalia
• Fungi
• Protista

16
Archaea

• Bacteria that live in extreme environments hot
  springs, salt ponds

17
Eubacteria

• Bacteria that live and grow in common
  environments our gut and skin, fresh and salt
  water, and almost every other environment on Earth

18
Plantae

• Multicellular plants, from mosses to redwood
  trees
• Have cellulose cell walls, perform photosynthesis

19
Animalia

• Multicellular animals
• Sponges,worms, insects, birds, fish, mammals
• Have no cell walls obtain energy from other
  organisms

20
Fungi

• Multicellular, with cell walls containing chitin
  obtain food by absorption
• Mushrooms, yeast

21
Protista

• Single celled eukaryotes live mostly in water
• Amoebas, algae, water molds, slime mold

22
The Kingdoms of Life
23
Diversity

• There are about 1.4 million named species, but
  there may be as many as 100 million living
  species this is only about 1 of the species
  that have ever lived most are extinct
• This diversity has arisen by evolution we are
  all related and are descended from a common
  ancestor

24
Genetics

• Genes determine the structures, appearance, and
  to some extent, the behavior of an organism
• Genes are inherited by offspring from their
  parents
• Genes are made of DNA DNA is used to make
  proteins, the working parts of a cell

25
Adaptations

• Members of a species share adaptations
  structures and behaviors that make them fit for a
  particular environment
• Adaptations are inherited those that promote
  survival and reproduction will be inherited more
  often by the next generation
• Diversity comes from different types of
  adaptations to different environments

26
Evidence for Evolution

• Fossils are preserved remnants of organisms some
  are very different from any organisms alive today

27
Natural Selection

• Charles Darwin suggested a mechanism for
  evolution Natural Selection his reasoning came
  from agriculture

28
Statistics

• Statistics are used to evaluate experimental
  results
• They measure probability that what we see is not
  a random effect
• It is almost always more realistic to measures a
  sample of a population, rather than an entire
  population

29
Sampling a Population
30
Sampling

• Because we cannot use an entire population, we
  must use a small number that represent the entire
  population a random sample
• Non-random samples may skew the results sample
  size can also skew results. In general, the
  larger the sample the better.
• Statistics can be used to determine if two
  populations are different, based on the variation
  in data using the idea of the standard deviation

31
Standard Deviation

• Measures how much individuals vary from the
  average or norm
• Is accurate only in normal groups those that
  have equal numbers on each side of the average
  (bell curve)

32
Normal Distribution
33
Standard Deviation
34
Distribution of IQ scores
Distribution of SAT Scores
35
The Eight Major Themes for AP Biology

• Science as a Process Science is a way of
  knowing. It can involve a discovery process using
  inductive reasoning, or it can be a process of
  hypothesis testing.
• Evolution Evolution is the biological change of
  organisms that occur over time and is driven by
  the process of natural selection. Evolution
  accounts for the diversity of Life on Earth.
• Energy Transfer Energy is the capacity to do
  work. All living organisms are active (living)
  because of their ability to link energy reactions
  to the biochemical reactions that take place
  within their cells.
• Continuity and Change All species tend to
  maintain themselves from generation to generation
  using the same genetic code. However, there are
  genetic mechanisms that lead to change over time,
  or evolution.
• Relationship of Structure to Function The
  structural levels from molecules to organisms
  ensure successful functioning in all living
  organisms and living systems.
• Regulation Everything from cells to organisms to
  ecosystems is in a state of dynamic balance that
  must be controlled by positive or negative
  feedback systems.
• Interdependence in Nature Living organisms
  rarely exist alone in nature.
• Science, Technology, and Society Scientific
  research often leads to technological advances
  that can have positive and/or negative impacts
  upon society as a whole.