what is life? how is it defined?. organized structures
TRANSCRIPT
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What is life?
How is it defined?
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Organized structures
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Homeostasis =
maintaining internal
balance
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Requires energy
Nutrients
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Grow
Reproduce
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Reproduction passes DNA
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Basic Properties of Life
1. Cellular organization all living things are comprised of at least one cell
2. Metabolism all living things process energy which is used to power other processes
3. Homeostasis all living things maintain stable internal environments to optimize conditions for
metabolism and other processes
4. Growth and reproduction all organisms have the capacity for growth and reproduction
5. Heredity all organisms pass genetic information across generations from parents to
offspring
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Living things function and interact with each other on many levels
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Levels of organization
BiosphereEcosystem
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Atoms: elements
all matter is made up of atoms Cannot be broken down or changed 92 elements in nature (total = 116) Can combine to make compounds
Most common elements in life:Oxygen (O)Carbon (C)
Hydrogen (H)Nitrogen (N)
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Nucleus: Neutrons, Protons (+) Electrons (-): Move around
nucleus in shells
Helium
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Isotopes are unstable = radioactive
Unstable because nucleus decays and releases particles
and energy
PET scan – application with radioactive isotope
(example of use of isotopes)
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Molecules
Atoms combine to form molecules
When combining with another atom, atoms will
share an electron or give up an electrons to the
other
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(slightly negative)
(slightly positive)
Water (H2O) is
a polar molecule
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Water Water is essential for life (life in Mars?), has
Unique Properties
1. Heat Storage: temperature changes slowly and holds temperature well
2. High Heat of Vaporization: requires tremendous energy to vaporize
3.Ice Formation: less dense as it freezes
4. Water molecules are sticky
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•cohesion – when one water molecule is attracted to another water molecule•adhesion – when polar molecules other than water stick to a water molecule
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5. The bond within a water molecule breaks spontaneously
H2O OH- + H+
Water Hydroxide Hydrogen
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The amount of ionized hydrogen from water in a solution can be measured as pH
pH in most living cells and their environments is close to 7
Organisms use buffers to minimize pH disturbances
pH = -log[H+]
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The pH scale
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Energy in Living Cells
Energy is the ability to do work There are many forms of energy but all of
them can be converted to heat, which is the most convenient form of energy to measure
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ATPThe Energy Currency of the Cell
The energy from the sun or from food sources must be converted to a form that cells can use: adenosine triphosphate (ATP)
ATP is an energy carrier
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endmost phosphate group is broken off and energy is released
ATP ADP + Pi + energy
• ATP cycle: 1. photosynthesis
Plant cells convert energy from the sun into ATP and to make sugar
2. cellular respirationcells break down the energy in
sugars and convert it ATP
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Scientific InvestigationThe scientific process has six stages
• 1. Observation: of natural phenomena
• 2. Hypothesis: make an educated guess that might be true
3. Predictions: if a hypothesis is correct, then specific consequences can be expected
4. Testing: scientists conduct experiments to attempt to verify predictions made by hypotheses
5. Controls: experiments usually employ a parallel design
6. Conclusion: a hypothesis that has been tested and not rejected is tentatively accepted
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Review Questions
1. The smallest particle into which a substance can be divided and still retain all of its chemical properties is:
A) matter.B) an atom.C) a molecule.D) mass.
2. The source of immediate, or "ready cash" energy in the body is _______________
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3. The attraction of water molecules to other water molecules is called
A) cohesion.B) capillary action.C) solubility.D) adhesion
4. The ability to do work is the definition for:
A) thermodynamics.B) radiation.C) energy.D) entropy.