Transcript The Living World - Chapter 1

Lecture 1
Introduction to Biology
The Diversity of Life
 Biology is the study of living things
 Living things can be divided into six kingdoms
Archaea
Fungi
Protista
Bacteria
Plantae
Animalia
What is Life?
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Biology is the study of life - but what does it mean to be
alive?
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Ludwig von Bertalanffy – life is a system where the whole is greater than the
sum of the parts
Living organisms and many non-living things share three
properties
1.
2.
3.
Complexity
Movement
Response to stimulation
Properties of Life
 All living organisms share five basic properties
1. Cellular Organization
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All living organisms are composed of at least one cell
2. Metabolism
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All living organisms use energy
3. Homeostasis
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All living organisms maintain stable internal conditions
4. Growth and reproduction
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All living organisms grow and reproduce
5. Heredity
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All living organisms possess a genetic system that is based on DNA
(Deoxyribonucleic acid)
The Organization of Life
 Living organisms function and
interact with each other at
many levels
1.
 These levels are organized in
a hierarchy of increasing
complexity:
1. Cellular Level
2. Organismal Level
3. Population Level
2.
3.
Life is an Emergent Property
 Each higher level of organization contains novel properties
not present at the simpler level of organization
 Birth rate & death rate – populations NOT individuals
 Evolution – populations evolve biologically NOT individuals
 These properties are termed emergent properties
 They are a consequence of the structural organization that is the hallmark of
life
 They characterize many aspects of the living world
Five Themes That Unify Biology
1. Evolution
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The gene frequencies change in a species over time
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Causes include:
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Genetic drift
Natural & artificial selection
Founder effects
2. The Flow of Energy
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All living organisms require energy
The sun is the source of energy for most ecosystems
Plants capture energy via photosynthesis
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They then act as an energy source for other organisms
3. Interaction
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Interaction between organisms is critical for evolution
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Social behavior occurs when organisms of the same species live in direct contact
Community dynamics occur when organisms of different species live in direct contact
(Competition, Predation, Symbiosis)
4. Structure Determines Function

Biological structures are well suited to their function

This is true at every level of organization
5. Homeostasis
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All living organisms act to maintain a relatively stable internal environment
Maintaining homeostasis requires energy and a lot of signaling back-and-forth between
cells
How We Learn & Think
 Our brains consist of
billions of interconnected
neurons
 Our senses stimulate
specific neuron pathways
 Pathway residual sensitivity
 Short term memory
 Pathway physical changes
 Long term memory
 Caused by:
 repeated stimulation
 intense emotion
 Sensory input & memory
storage share the same
circuits
 This causes associations
How We Know Things
 Our brains are great at two things
 Recognizing patterns
 Filling in sensory gaps (story telling)
 Both of these can get us into trouble
 Pattern Matching
 Recognizing patterns that are not real
 Not recognizing patterns that are real
 Story Telling
 Not checking to see that our stories are true
 80% of personal disagreements between people begin as wrong
stories each has told himself about the other’s motivations
Science: Testing Our Patterns & Stories
 The Classic Scientific Method
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Observation
Hypothesis
Test
Analysis (observation)
Modify hypothesis if necessary
 The Null-Hypothesis
 No hypothesis is valid if it cannot be tested
 No test is valid if its results cannot disprove the hypothesis
 The null-hypothesis is the formal statement of the hypothesis not
being true and the test results that will support the null-hypothesis
 Minimizing Results Based on Chance
 Control groups: checking to make sure the same results would not
occur without the test intervention
 Statistical analysis: checking to see if the same result could be
caused by chance (e.g. how likely is it to get 4 heads in a row when
flipping coins randomly versus always starting with the coin on tails?)
How Scientists Think
 Inductive Reasoning
 Recognizing patterns
 Is used by scientists to develop
hypotheses about how the
world works
 Deductive Reasoning
 Telling stories based on patterns
 Uses accepted general principles
as a “guide” to explain specific
observations
Inference vs. Observation
 An observation is limited to a description of actions or
events without interpretation
 An inference is a conclusion we draw based on what we
observe
 Inference or observation?
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Example 1 (The cat is happy)
Example 2 (The cat is chewing on the plant leaves)
Example 3 (The cat is sleeping)
Example 4 (The cat is a female)
Theory and Certainty in Science
 A theory is a set of hypotheses that have been tested many
times and not rejected
 It indicates a high degree of certainty
 However, there is no absolute truth in science
 Everything is open to more testing and reinterpretation
 Acceptance of a theory is always provisional
 Note:
 To the general public, the word theory is often used to mean what a
scientist would call a hypothesis, a lack of knowledge or a guess
 To scientists, a theory represents that of which they are most certain,
explanations supported by a wealth of evidence and experimental data
The Limitations of Science
 Science is limited to organisms and processes that can be
observed and measured
 Many spiritual and religious explanations are beyond the scope of science
 Most religious explanations do not allow formation of a realistic null
hypothesis
 However, the physiological and evolutionary basis of spiritual and religious
experience is a current hot research topic in both neurophysiology &
evolutionary biology
 There are also practical limits
 Science can provide options and understanding
 Science cannot be relied upon to solve all problems
 For example, what constitutes “acceptable risk” cannot be answered by
science!
Four Theories Unify Biology & This Class
1. The Gene Theory
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The information that determines what an organism is like is encoded in its genes
Genes are located along DNA molecules
The entire set of DNA instructions that specifies a cell is termed its genome
2. The Cell Theory
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All living organisms are composed of cells
Cells are the basic units of life
All cells come from other cells
3. The Theory of Heredity
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Genes represent traits of an organism and are inherited as discrete units
Chromosomal theory of inheritance: Genes are physically located on chromosomes
4. The Theory of Evolution
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All living organisms are related to one another in a common tree of life
Diversity of the living world is the result of natural selection
The Brain & Study Implications
 3 hours of study at one time is not effective for long term
memory formation
 Studying the same thing 20 minutes, 3 times a day for three
days is more effective for long term memory formation
 Using your brain to rephrase or rework the material is more
effective for long term memory formation than repetitive
reading or listening