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64 Cards in this Set
- Front
- Back
Three modes of selection:
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-Directional selection favors individuals at one end of the phenotypic range
-Disruptive selection favors individuals at both extremes of the phenotypic range -Stabilizing selection favors intermediate variants and acts against extreme phenotypes |
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Hardy-Weinberg
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equation can be used to test whether a population is evolving
p+q=1 ○ 320 red flowers (CRCR) ○ _160 pink flowers (C^RC^W)______________ ○ 200 white flowers (CWCW) – Calculate the number of copies of each allele: ○ CR = (320 ´ 2) + 160 = 800 ○ CW = (20 ´ 2) + 160 = 200 – To calculate the frequency of each allele: ○ _p=freq C^R=800/(800+200)______________ ○ q = freq CW = 200 / (800 + 200) = 0.2 – The sum of alleles is always 1 0.8 + 0.2 = 1 • The Hardy-Weinberg principle describes a population that is not evolving ○ p2 + 2pq + q2 = 1 where p2 and q2 represent the frequencies of the homozygous genotypes and 2pq represents the frequency of the heterozygous genotype |
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The five conditions for nonevolving populations are rarely met in nature:
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◊ No mutations
◊ Random mating ◊ No natural selection ◊ Extremely large population size ◊ No gene flow |
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Natural selection
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-Natural selection is the only mechanism that consistently causes adaptive evolution
– Gene flow tends to reduce variation among populations over time |
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Biological Species Concept
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(one way to divide species):
-A species is a group of populations whose members can breed and produce viable, fertile offspring -Ability to mate = formation of a species -Gene flow between populations holds together the phenotype of a population (ongoing exchange of alleles) -The biological species concept emphasizes absence of gene flow |
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Other Definitions of Species
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1. morphological species concept:
-A species is characterized by its body shape -It applies to sexual and asexual species but relies on subjective criteria 2. ecological species concept: -A species is characterized by its ecological niche -It applies to sexual and asexual species and emphasizes the role of disruptive selection 3. phylogenetic species concept: -A species is the smallest group of individuals that share a common ancestor -It applies to sexual and asexual species, but it can be difficult to determine the degree of difference required for separate species |
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Speciation can occur in two ways:
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Allopatric speciation
Sympatric speciation -In a sympatric speciation, various factors can limit gene flow: -Polyploidy -Habitat differentiation -Sexual selection |
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radiometric dating
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-The absolute ages of fossils can be determined by radiometric dating
-A “parent” isotope decays to a “daughter” isotope at a constant rate -Each isotope has a known half-life, the time required for half the parent isotope to decay -Radiocarbon dating can be used to date fossils up to 75,000 years old -For older fossils, some isotopes can be used to date sedimentary rock layers above and below the fossil |
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Geological record
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endosymbiont theory
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-The endosymbiont theory proposes that mitochondria and plastids (chloroplasts and related organelles) were formerly small prokaryotes living within larger host cells
-An endosymbiont is a cell that lives within a host cell |
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Key evidence supporting an endosymbiotic origin of mitochondria and plastids:
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-Inner membranes are similar to plasma membranes of prokaryotes
-Division is similar in these organelles and some prokaryotes -These organelles transcribe and translate their own DNA -Their ribosomes are more similar to prokaryotic than eukaryotic ribosomes |
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Plate Tectonics
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-At three points in time, the land masses of Earth have formed a supercontinent: 1.1 billion, 600 million, and 250 million years ago
-According to the theory of plate tectonics, Earth’s crust is composed of plates floating on Earth’s mantle -Tectonic plates move slowly through the process of continental drift -Oceanic and continental plates can collide, separate, or slide past each other -Interactions between plates cause the formation of mountains and islands, and earthquakes |
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Consequences of Continental Drift
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-Formation of the supercontinent Pangaea about 250 million years ago had many effects
--A deepening of ocean basins --A reduction in shallow water habitat --A colder and drier climate inland |
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Hierarchial Classification
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Domain, Kingdom, Phylum, Class, Order, family, genus, species
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Alternation of Generations and Multicellular, Dependent Embryos
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-Plants alternate between two multicellular stages, a reproductive cycle called alternation of generations
-The gametophyte is haploid and produces haploid gametes by mitosis -Fusion of the gametes gives rise to the diploid sporophyte, which produces haploid spores by meiosis -The diploid embryo is retained within the tissue of the female gametophyte -Nutrients are transferred from parent to embryo through placental transfer cells -Land plants are called embryophytes because of the dependency of the embryo on the parent |
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Walled Spores Produced in Sporangia
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-The sporophyte produces spores in organs called sporangia
-Diploid cells called sporocytes undergo meiosis to generate haploid spores -Spore walls contain sporopollenin, which makes them resistant to harsh environments |
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Multicellular Gametangia
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-Gametes are produced within organs called gametangia
-Female gametangia, called archegonia, produce eggs and are the site of fertilization -Male gametangia, called antheridia, produce and release sperm |
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Apical Meristems
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-Plants sustain continual growth in their apical meristems
-Cells from the apical meristems differentiate into various tissues |
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Additional derived traits include
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-Cuticle, a waxy covering of the epidermis
-Mycorrhizae, symbiotic associations between fungi and land plants that may have helped plants without true roots to obtain nutrients -Secondary compounds that deter herbivores and parasites |
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vascular tissue
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-Land plants can be informally grouped based on the presence or absence of vascular tissue
-Most plants have vascular tissue; these constitute the vascular plants -Nonvascular plants are commonly called bryophytes -Bryophytes are not a monophyletic group; their relationships to each other and to vascular plants is unresolved -Seedless vascular plants can be divided into clades -Lycophytes (club mosses and their relatives) -Pterophytes (ferns and their relatives) -Seedless vascular plants are paraphyletic, and are of the same level of biological organization, or grade |
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Mosses and other nonvascular plants have life cycles dominated by gametophytes
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-Bryophytes are represented today by three phyla of small herbaceous (nonwoody) plants
+Liverworts, phylum Hepatophyta +Hornworts, phylum Anthocerophyta +Mosses, phylum Bryophyta |
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Moss Life Cycle(Gametophyte)
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-A spore germinates into a gametophyte composed of a protonema and gamete-producing gametophore
The height of gametophytes is constrained by lack of vascular tissues -Rhizoids anchor gametophytes to substrate -Mature gametophytes produce flagellated sperm in antheridia and an egg in each archegonium -Sperm swim through a film of water to reach and fertilize the egg |
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Fern Life Cycle (sporophyte)
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- Sporangia Release spores that develop into gametophytes
- Each gametophyte develops sperm-producing organs called antheridia and egg producing archegonia - Sperm use flagella to swim to the eggs in the archegonia - A zygote develops into a new sporophyte and grows out of the gametophyte -On the underside of the sporophyte's reproductive leaves are spots called sori. |
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Five Derived Traits of Seed Plants
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Plant Groups
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Flower structure
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monocots and dicots
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Embryonic development
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Symmetry
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Diploblastic
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animals have ectoderm and endoderm
-These include cnidarians and comb jellies |
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Triploblastic
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animals also have an intervening mesoderm layer; these include all bilaterians
-These include flatworms, arthropods, vertebrates, and others |
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Body Cavities
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-Most triploblastic animals possess a body cavity
-A true body cavity is called a coelom and is derived from mesoderm -Coelomates are animals that possess a true coelom -A pseudocoelom is a body cavity derived from the mesoderm and endoderm -Triploblastic animals that possess a pseudocoelom are called pseudocoelomates -Triploblastic animals that lack a body cavity are called acoelomates |
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Proto vs Deuter
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Most eudicots and gymnosperms have a taproot system, which consists of:
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-A taproot, the main vertical root
-Lateral roots, or branch roots, that arise from the taproot |
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Most monocots have a fibrous root system, which consists of:
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Adventitious roots that arise from stems or leaves
Lateral roots that arise from the adventitious roots |
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Root structure
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Stem Structure
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Pollination
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-In angiosperms, pollination is the transfer of pollen from an anther to a stigma
-Pollination can be by wind, water, or animals -Wind-pollinated species (e.g., grasses and many trees) release large amounts of pollen |
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Fruits
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Exchange with the Enviornment
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Feedback control maintains the internal environment in many animals
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-A regulator uses internal control mechanisms to moderate internal change in the face of external, environmental fluctuation
-A conformer allows its internal condition to vary with certain external changes -For a given variable, fluctuations above or below a set point serve as a stimulus; these are detected by a sensor and trigger a response -The response returns the variable to the set point -The dynamic equilibrium of homeostasis is maintained by negative feedback, which helps to return a variable to a normal range -Most homeostatic control systems function by negative feedback, where buildup of the end product shuts the system off -Positive feedback amplifies a stimulus and does not usually contribute to homeostasis in animals -Homeostasis can adjust to changes in external environment, a process called acclimatization |
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Homeostatic processes for thermoregulation involve form, function, and behavior
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-Thermoregulation is the process by which animals maintain an internal temperature within a tolerable range
The body temperature of a poikilotherm varies with its environment -The body temperature of a homeotherm is relatively constant -The relationship between heat source and body temperature is not fixed (that is, not all poikilotherms are ectotherms) -Five adaptations help animals thermoregulate: =Insulation =Circulatory adaptations =Cooling by evaporative heat loss =Behavioral responses =Adjusting metabolic heat production |
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countercurrent exchange
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-Countercurrent heat exchangers transfer heat between fluids flowing in opposite directions and reduce heat loss
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Thermogenesis
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--the adjustment of metabolic heat production to maintain body temperature
-Thermogenesis is increased by muscle activity such as moving or shivering -Nonshivering thermogenesis takes place when hormones cause mitochondria to increase their metabolic activity -Some ectotherms can also shiver to increase body temperature -Thermoregulation is controlled by a region of the brain called the hypothalamus -The hypothalamus triggers heat loss or heat generating mechanisms -Fever is the result of a change to the set point for a biological thermostat |
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Single and Double Circulation
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-Bony fishes, rays, and sharks have single circulation with a two-chambered heart
-In single circulation, blood leaving the heart passes through two capillary beds before returning -Amphibian, reptiles, and mammals have double circulation -Oxygen-poor and oxygen-rich blood are pumped separately from the right and left sides of the heart -In reptiles and mammals, oxygen-poor blood flows through the pulmonary circuit to pick up oxygen through the lungs -In amphibians, oxygen-poor blood flows through a pulmocutaneous circuit to pick up oxygen through the lungs and skin -Oxygen-rich blood delivers oxygen through the systemic circuit -Double circulation maintains higher blood pressure in the organs than does single circulation |
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Amphibians
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-Frogs and other amphibians have a three-chambered heart: two atria and one ventricle
-The ventricle pumps blood into a forked artery that splits the ventricle’s output into the pulmocutaneous circuit and the systemic circuit -When underwater, blood flow to the lungs is nearly shut off |
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Reptiles (Except Birds)
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-Turtles, snakes, and lizards have a three-chambered heart: two atria and one ventricle
-In alligators, caimans, and other crocodilians a septum divides the ventricle -Reptiles have double circulation, with a pulmonary circuit (lungs) and a systemic circuit |
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Mammals and Birds
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-Mammals and birds have a four-chambered heart with two atria and two ventricles
-The left side of the heart pumps and receives only oxygen-rich blood, while the right side receives and pumps only oxygen-poor blood -Mammals and birds are endotherms and require more O2 than ectotherms |
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Mammalian Circulation
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§ Right ventrical
§ Simelunar valve § Pulmonary arteries § Lungs-capillary beds-loads O2 and unloads CO2 § Pulmonary veins § Left atrium § Atrioventricular valve § Left ventrical § Semilunar valve § Aorta § Coronary arteries (to heart) § Capillary beds in head and arms § Capillary beds in the abdominal organs and legs § Capillaries rejoin, form venules, then veins § Superior vena cava § Inferior vena cava § Right atrium § Atrioventricular valve |
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Fish gills use a countercurrent exchange system, where blood flows in the opposite direction to water passing over the gills; blood is always less saturated with O2 than the water it meets
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Respiratory system
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-Air passes through the pharynx, larynx, trachea, bronchi, and bronchioles to the alveoli, where gas exchange occurs
-Exhaled air passes over the vocal cords in the larynx to create sounds -Cilia and mucus line the epithelium of the air ducts and move particles up to the pharynx Gas exchange takes place in alveoli, air sacs at the tips of bronchioles -Oxygen diffuses through the moist film of the epithelium and into capillaries -Carbon dioxide diffuses from the capillaries across the epithelium and into the air space |
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Osmoregulation balances the uptake and loss of water and solutes
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-Cells require a balance between uptake and loss of water
-Osmolarity, the solute concentration of a solution, determines the movement of water across a selectively permeable membrane -If two solutions are isoosmotic, the movement of water is equal in both directions -If two solutions differ in osmolarity, the net flow of water is from the hypoosmotic to the hyperosmotic solution -Osmoconformers, consisting only of some marine animals, are isoosmotic with their surroundings and do not regulate their osmolarity -Osmoregulators expend energy to control water uptake and loss in a hyperosmotic or hypoosmotic environment -Most animals are stenohaline; they cannot tolerate substantial changes in external osmolarity -Euryhaline animals can survive large fluctuations in external osmolarity |
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Marine Animals
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-Most marine invertebrates are osmoconformers
-Most marine vertebrates and some invertebrates are osmoregulators -Marine bony fishes are hypoosmotic to sea water -They lose water by osmosis and gain salt by diffusion and from food -They balance water loss by drinking seawater and excreting salts |
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Transport Epithelia in Osmoregulation
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-Animals regulate the solute content of body fluid that bathes their cells
-Transport epithelia are epithelial cells that are specialized for moving solutes in specific directions -They are typically arranged in complex tubular networks -An example is in nasal glands of marine birds, which remove excess sodium chloride from the blood |
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The nephron is organized for stepwise processing of blood filtrate
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-Proximal Tubule
=Reabsorption of ions, water, and nutrients takes place in the proximal tubule =Molecules are transported actively and passively from the filtrate into the interstitial fluid and then capillaries =Some toxic materials are actively secreted into the filtrate =As the filtrate passes through the proximal tubule, materials to be excreted become concentrated -Descending Limb of the Loop of Henle =Reabsorption of water continues through channels formed by aquaporin proteins =Movement is driven by the high osmolarity of the interstitial fluid, which is hyperosmotic to the filtrate =The filtrate becomes increasingly concentrated -Ascending Limb of the Loop of Henle =In the ascending limb of the loop of Henle, salt but not water is able to diffuse from the tubule into the interstitial fluid =The filtrate becomes increasingly dilute |
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Continued
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-Distal Tubule
=The distal tubule regulates the K+ and NaCl concentrations of body fluids =The controlled movement of ions contributes to pH regulation -Collecting Duct =The collecting duct carries filtrate through the medulla to the renal pelvis =One of the most important tasks is reabsorption of solutes and water =Urine is hyperosmotic to body fluids |
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The Two-Solute Model
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-In the proximal tubule, filtrate volume decreases, but its osmolarity remains the same
-The countercurrent multiplier system involving the loop of Henle maintains a high salt concentration in the kidney -This system allows the vasa recta to supply the kidney with nutrients, without interfering with the osmolarity gradient -Considerable energy is expended to maintain the osmotic gradient between the medulla and cortex -The collecting duct conducts filtrate through the osmolarity gradient, and more water exits the filtrate by osmosis -Urea diffuses out of the collecting duct as it traverses the inner medulla -Urea and NaCl form the osmotic gradient that enables the kidney to produce urine that is hyperosmotic to the blood |
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Nerves
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Action potentials are the signals conducted by axons
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-Changes in membrane potential occur because neurons contain gated ion channels that open or close in response to stimuli
-When gated K+ channels open, K+ diffuses out, making the inside of the cell more negative -This is hyperpolarization, an increase in magnitude of the membrane potential -Opening other types of ion channels triggers a depolarization, a reduction in the magnitude of the membrane potential -For example, depolarization occurs if gated Na+ channels open and Na+ diffuses into the cell |
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Graded Potentials and Action Potentials
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-Graded potentials are changes in polarization where the magnitude of the change varies with the strength of the stimulus
-These are not the nerve signals that travel along axons, but they do have an effect on the generation of nerve signals -If a depolarization shifts the membrane potential sufficiently, it results in a massive change in membrane voltage called an action potential -Action potentials have a constant magnitude, are all-or-none, and transmit signals over long distances They arise because some ion channels are voltage-gated, opening or closing when the membrane potential passes a certain level |
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Generation of Action Potentials: A Closer Look
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-An action potential can be considered as a series of stages
-At resting potential =1.Most voltage-gated sodium (Na+) channels are closed; most of the voltage-gated potassium (K+) channels are also closed -When an action potential is generated 2.Voltage-gated Na+ channels open first and Na+ flows into the cell 3.During the rising phase, the threshold is crossed, and the membrane potential increases 4.During the falling phase, voltage-gated Na+ channels become inactivated; voltage-gated K+ channels open, and K+ flows out of the cell 5.During the undershoot, membrane permeability to K+ is at first higher than at rest, then voltage-gated K+ channels close and resting potential is restored |
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Hearing
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-Vibrating objects create percussion waves in the air that cause the tympanic membrane to vibrate
-The three bones of the middle ear transmit the vibrations of moving air to the oval window on the cochlea -These vibrations create pressure waves in the fluid in the cochlea that travel through the vestibular canal -Pressure waves in the canal cause the basilar membrane to vibrate, bending its hair cells -This bending of hair cells depolarizes the membranes of mechanoreceptors and sends action potentials to the brain via the auditory nerve -The fluid waves dissipate when they strike the round window at the end of the tympanic canal |
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The ear conveys information about
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-Volume, the amplitude of the sound wave
-Pitch, the frequency of the sound wave -The cochlea can distinguish pitch because the basilar membrane is not uniform along its length -Each region of the basilar membrane is tuned to a particular vibration frequency |
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Several organs of the inner ear detect body movement, position, and balance
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-The utricle and saccule contain granules called otoliths that allow us to perceive position relative to gravity or linear movement
-Three semicircular canals contain fluid and can detect angular movement in any direction |