Biology 101 exam 1
Terms
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- Adaptation
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⬢An Adaptation is a trait that allows an individual to survive in certain environments relative to individuals without that trait.
⬢Adaptations evolve by genetic change that occurs over generations in response to natural selection in a population. - Ice fish have evolved to:
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• Lose ability to:
– Make red blood cells
– Make hemoglobin
• Developed the ability to use the higher levels of dissolved oxygen found in colder water.
– Absorption: Larger gills and scaleless skin with unusually large capillaries.
– Delivery: Larger heart and greater blood volume. - What is evolution?
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⬢ A change in the frequency of adaptations (traits) in a population over time.
⬢ And therefore, a change in the gene frequencies that code for those adaptations in a population over time. - Acclimatization
- Acclimatization is a phenotypic change that occurs in an individual in response to a short-term change in environmental conditions.
- Trade-Offs
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A Constraint on an adaptation is a trade-off, which may involve expenditures of time or energy.
A trade-off is an inescapable compromise between traits. - Constraints and Trade-Offs
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A Constraint on an adaptation is a trade-off, which may involve expenditures of time or energy.
A trade -off is an inescapable compromise between traits. - Adaptive Structures
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• A structure found in an animal is adaptive—if it helps the individual survive and produce offspring—
• The structure ’s size, shape, or composition often correlates closely with its function - Types of Scaling
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⬢ Quantities that change at the same
rate are isometric.
⬢ Disproportionate changes in anatomical structures or physiological processes with changes in body size are allometric.
⬢ Allometry is the study of these relationships. - ⬢Conformational homeostasis
- - conformation to the external environment.
- ⬢ Regulatory homeostasis
- - a physiological mechanism that adjusts the internal state within a specific value or within tolerable limits, regardless of the external conditions.
- Homeostatic systems
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⬢ A sensor is a structure that senses some aspect of the external or internal environment.
⬢ An integrator is part of the nervous system that evaluates sensory information and "decides" if a response is necessary to achieve homeostasis.
⬢An effector is any structure that helps to restore the desired internal condition. - If body temp is high
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• Dilate blood vessels of skin
– Increase blood flow
– Increase heat loss
• Stimulate sweat glands
– Evaporative heat loss
• Stimulate breathing
– Heat via panting - If body temp is low
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• Constrict blood vessels of skin
– Decrease blood flow
– Decrease heat loss
• Muscle Shivering
– Generates heat
• Stimulate cellular respiration
– Generate metabolic heat - Gaining and Losing Heat
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⬢ An endotherm produces heat in its own tissue;
⬢ An ectotherm relies on heat gained from the environment. - Type of Temperature Homeostasis
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⬢ Homeotherms keep their body temperature constant;
⬢ Heterotherms experience changes in body temperature. - Endotherm Trade offs
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POSITIVES
– enzymes at optimal temperatures at all times
– remain active in winter and at night.
– sustain very high levels of aerobic activities such as running or flying.
NEGATIVES
–must obtain large quantities of energy- rich food - Myelination
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The process of axons being enveloped in myelin sheaths.
Myelin sheaths are membranes made of mostly of lipids.
Lipids are poor conductors of electrical signals. - Membrane Potential
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• Inside cell
– Mostly potassium (K+)
– Some Sodium (Na+)
– Lots of impermeable macromolecules with a negative
charge (-), sulfates (-), & phosphates (-).
• Outside Cell
– Mostly Na+
– Less K+
– Lots Chloride (Cl-), but not important to nerve signals - Voltage-gated Ion Channels
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• Na+ – A Fast opening gate – A slow closing gate
• K+ – A slow opening gate - Stages of Action Potential
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1) Resting State
2) Threshold
3) Depolarization Phase of Action Potential
4) Repolarization Phase of Action Potential
5) Undershoot
6) Back to Resting State - Stages of Depolarization - Resting State
- Resting State – Both sodium and potassium channels are closed and membrane is in the resting state.
- Stages of Depolarization - Threshold
- Threshold - A stimulus opens some Na+ channels. If the influx of Na+ achieves threshold, then more channels are opened, triggering an action potential.
- Stages of Action Depolization - Depolarization phase
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Depolarization Phase- Activation gates of
sodium channels are open, but the potassium channels remain closed. Sodium ions rush into the cell, the interior of the cell becomes more positive. - Stages of Depolarization- Repolarization phase
- Repolarization phase- Inactivation gates close channels, and potassium channels open. Potassium ions leave the cell, and the loss of positive charge causes the inside of the cell to become more negative.
- Stages of Depolarization- Undershoot
- Undershoot - Both gates of the sodium channels are closed, but potassium channels remain open because their relatively slow gates have not had time to respond to repolarization of the membrane. Within another millisecond or two, the resting state is restored and the system is ready to respond again.
- Synapse
- Place where synaptic terminals of one neuron come into contact with another neuron
- Presynaptic Cell
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⬢ Action potential in presynaptic cell
⬢ Depolarization of presynaptic membrane
⬢ Open of voltage-gated calcium channels
⬢ Influx of calcium ion
⬢ Synaptic vesicles fuse with presynaptic membrane
⬢ Neurotransmitter is released from vesicles by exocytosis. - Synaptic Cleft
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⬢ Neurotransmitter diffuses across synaptic cleft.
⬢ Neurotransmitter removed from synaptic cleft. - Postsynaptic Cell
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• Neurotransmitters binds to receptors in membrane.
• Ion channels coupled to the receptor open.
• Membrane potential changes
– Change can be depolarizing (excitatory)
– Change can be hyperpolarizing (inhibitory) - tetrodoxin
- blocks sodium ion channels
- Transduction
- Transformation of one type of energy into electrical impulses in nervous system
- Types of Sensory Receptors
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• Mechanoreceptors
– pressure, touch, stretch, motion, and sound (muscle spindle, hair cell)
• Pain Receptors
– excess heat, pressure, chemicals released from inflammation
• Thermoreceptors
– Cold and Hot, interoreceptors for temperature to anterior hypothalamus.
• Chemoreceptors
– Solute concentration as well to specific molecules.
• Electromagnetic Receptors
– visible light, infrared, ultraviolet, electricity, magnetism. - Interoception
- – sensory processes having to do with conditions on the surface or inside the body
- Exteroception
- – sensory processes having to do with conditions outside the body
- Hair cell physiology
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1. Arrival of pressure wave bends cilia
2. Potassium channels open
3. Membrane depolarizes
4. Depolarization triggers influx of Ca2+ ions
5. Ca2+ causes synaptic vesicles to fuse with cell membrane
6. Neurotransmitter is released