Transcript What is life?

Cell Composition
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Botany 1010
September 9, 1999
Lecture #3
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Composition of Living Things
1 All living things are composed of ?
2 The smallest unit of living matter is ?
3 The automatic tendency to maintain
appropriate internal environment is called ?
4 Four characteristics of living things are ?
5 Biological growth occurs from the ?
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Biological growth occurs from the ?
Cells reproduce from a blue print called DNA,
– Dioxy-ribo-nuclaeic Acid
• Asexual reproduction:
a copy of the blue print splits into 2 individual
• Sexual reproduction:
two parents blue prints combine to form a new individual
• Metabolism is responsible for growth,
maintenance, and reproduction
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Evolutionary Change
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Charles Darwin theorized that ?
These changes were selected because they ?
This Theory is referred to as ?
And occurs at the _____ level within a
_______ ?
5 Various populations of different species
(birds) that interact are communities
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Properties of _____ are:
Species
• ?
• ?
• ?
• ?
• ?
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Population
• ?
• ?
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• ?
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Biological Organisms
can be organized
based on differences in
• Chemical
• Cellular
• Multicullular
• Ecological
• Functional
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Taxonometry is ?
• K
–P
•C
–O
»F
*G
>S
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How many Kingdoms of Life ?
What are they?
An organisms Scientific name is?
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Reasoning
• Using general principles or experience to
infer more detailed predictions is ?
• Using specific examples to draw a general
conclusion ?
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The scientific method?
Is a process of critical review & skepticism
• recognize a problem
• make observations
• developing an educated guess, a hypothesis
• test your guess through experimentation
• evaluate your results
• have results peer reviewed
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Guidelines for scientific thought
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hypothesis consistent with what is known
hypothesis must be testable
the test must be repeatable
it must be falsifiable
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IF berries are blue,
THEN they are blue berries
IF berries are NOT blue,
THEN they are NOT blue berries
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Be Skeptical, Be Objective
• Sources of ERROR
– BIAS
– ATYPICAL SAMPLE
• Probability of ERROR (r^2)
– ACCURACY
– PRECISION
• Theory: predictions made using the theory as a
guide are consistently accurate and precise
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Chemistry of Life
Atoms:
Molecules:
composed of atoms held together by
ionic or covalent bonds
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ATOMS
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Composed of Protons, Neutrons, and Electrons
Atomic Nucleus contains Protons and Neutrons
Neutrons and Protons have similar mass (weight)
Electrons have a very small mass
and spin around the Atomic Nucleus
• Atoms have equal number of protons (+)
and electrons (-)
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Elements
• A substance that cannot be broken down
into a simpler substance, and still maintains
its characteristics
• 92 naturally occurring elements
• Latin / English names
• Denoted by a two letter chemical symbol
• Elements have a fixed number of protons
• This number is an elements Atomic Number
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Elements
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H
O
N
C
Na
P
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Hydrogen
Oxygen
Nitrogen
Carbon
Sodium
Phosphorous
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Atomic Number
a subscript
written to the left of the Atomic Symbol
• 1H
• 8O
• 23/11 Na
• Hydrogen
with 1 proton
• Oxygen
with 8 protons
• Sodium
12 neutrons,
11 protons, and an
atomic mass of 23 (11+12)
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Molecules
• Two atoms combine to form a molecule
• 8O + 8O = O2
• Common notation
O + O = O2, Oxygen Molecule
Molecules and or Atoms combine in fixed
ratio’s to form Compounds
2 H + 1 O = H2O, Water Molecule (compound)
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Chemical Bonds
Covalent
• electrons are shared between atoms in a
molecule or compound
– Single bond: share one electron
• (hardest to break apart)
– Double bond: share two electrons
– Triple bond: share three electrons
• (easiest to break apart)
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Covalent Bonds
Nonpolar Covalent bonds
• Atoms have equal attraction for electrons
– O2, each Oxygen shares electrons equally
Polar Covalent bonds
• Atoms have different attraction (affinity) for
shared electrons
– H2O, Hydrogen atoms are electro-positive (2*-1)
– Oxygen atoms are electro-negative (1*-2)
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Ionic Bonds
• Polar: Electrons from one atom are
transferred to another
• One atom gains an electron and becomes
negatively charged (ANION)
• The other atom looses an electron, thus
there are more protons than electrons in the
atom, causing a positive charge (CATION)
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Ionic Compounds
• Cations and Anions are held together by
their opposite charges (mutual attraction)
• Na (Sodium) donates electron (cation)
– (positive charge = +1)
• Cl (Chlorine) receives electron (anion)
– (negative charge = -1)
• NaCl, Ionic Compound called SALT
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Ionic Compounds
• It takes a great deal of energy to overcome
the electrical attraction in solid substances
that have ionic bonds
• Ionic bonds dissolve easily (split apart) in
water, WHY?
• Hydrogen (+charge) attracts anion (Cl-)
• Oxygen (-charge) attracts cation (Na+)
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Water Chemical Properties
• Water is an excellent SOLVENT
– It easily dissolve ionic bonds
• Process is called HYDRATION
• Polar compounds are water loving
Hydrophillic
• Non Polar compounds are water hating
Hydrophobic (oil & water don’t mix)
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Water Properties
• Unique biological solvent
• Capable of dissolving other substances
• … because it is polar, its electrons from one
atom can be given to another atom/molec.
• It is Cohesive: pulling other things with it
• It is Adhesive: sticking to other surfaces
Is Water important to biological processes ?
… your body 70%; cells 80% of weight
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Water Properties
• Changes temperature more slowly than
other substances
• Specific Heat: temperature required to increase
one gram of a substance one degree centigrade
• High Heat of Vaporation: sweat cools us by
getting rid of excess heat, evaporation
• Salts dissociate in water and conduct electrical
current (nerve impulses, etc.) as electrolytes
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Water Properties
• Acids ionize in water to yield
hydrogen ions and an anion, (negative charge = -1)
• Bases dissociate in water to produce
hydrogen ions and a cation, (positive charge = +1)
• The negative logarithm of the concentration of
hydrogen ions are measured as pH
• pH of water is 7.0
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