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Animal Kingdom Evolution
5 Defining characteristics of the animal kingdom: 1) Heterotrophic eukaryotes; ingestion 2) Lack cell walls; collagen 3) Nervous & muscular tissue 4) Sexual; diploid; cleavage; blastula; gastrulation; larvae; metamorphosis 5) Regulatory genes: Hox genes
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Animal phylogeny *Monophyletic; colonial flagellated protist ancestor
First split 1- Parazoa vs. Eumetazoa dichotomy: *(Parazoa)~ no true tissues example sponges *(Eumetazoa)~ true tissues all other animals
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Parazoa *Parazoa: No true tissues Invertebrates
No true tissues, unspecialized cells: *Sponges Closest lineage to protists Phylum Porifera
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Phylum: Porifera (“pore bearer”)
*Sessile (attached to bottom) Spongocoel (central cavity) *Osculum (large opening) Choanocytes (flagellated collar cells) *Hermaphroditic (produce both sperm and eggs)
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Eumetazoa: True Tissues: Everything but sponges
2nd split – Body Symmetry Radiata vs.Bilateria dichotomy: 1) *radial body symmetry *Cnidaria (hydra; ‘jellyfish’; sea anemones) & *Ctenophora (comb jellies) 2) *bilateral body symmetry (also: **cephalization) all other animals
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Eumetazoa The Radiata, Diploblastic
Radial symmetry Phy: Cnidaria (hydra, jellies, sea anemones, corals) *No mesoderm; gastrovascular cavity (GVC)(sac with a central digestive cavity) Hydrostatic skeleton (fluid held under pressure) Polyps and medusa Cnidocytes (cells used for defense and prey capture) Nematocysts (stinging capsule) Phy: Ctenophora (comb jellies)
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3. Gasturlation: diploblastic vs. triploblastic
3- Gastrulation: germ layer development; ectoderm (outer), mesoderm (middle), endoderm (inner) diploblastic-2 layers; no mesoderm; Radiata Phy: Cnidaria (hydra, jellies, sea anemones, corals) triploblastic-all 3 layers *bilateria symmetry All others
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4- Acoelomate, Pseudocoelomate, and Coelomate
All are triploblastic animals *acoelomates solid body, no body cavity (Platyhelminthes-flatworms) mesoderm but, GVC with only one opening *Some cephalization *pseudocoelomates body cavity, but not lined with mesoderm called (Rotifers); *1st with a complete digestive track Parthenogenesis: type of reproduction in which females produce offspring from unfertilized eggs Coelomate: true coelom (body cavity) lined with mesoderm called Phy: Nematoda (roundworms) Complete digestive track; no circulatory system
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Animal phylogeny 5 *Protostomes Phylogenetics debated….
1)Phy: Nemertea (proboscis and ribbon worms) *Complete digestion and closed circulatory system (blood) 2) Phy: the lophophorates (sea mats, tube worms, lamp shells)
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The Coelomates: Protostomes, II
3) Phy: Mollusca (snails, slugs, squid, octopus, clams, oysters, chiton) Soft body protected by a hard shell of calcium carbonate Foot (movement), visceral mass (internal organs); mantle (secretes shell); radula (rasp-like scraping organ) Ciliated trochophore larvae (related to Annelida?)
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The Coelomates: Protostomes, III
4) Phy: Annelida (earthworms, leeches, marine worms) True body segmentation (specialization of body regions) Closed circulatory system Metanephridia: excretory tubes “Brainlike” cerebral ganglia *Hermaphrodites, but cross- fertilize
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The Coelomates: Protostomes, IV
5) Phy: Arthropoda trilobites (extinct); crustaceans (crabs, lobsters, shrimps); spiders, scorpions, ticks (arachnids); insects (entomology) *2 out of every 3 organisms (most successful of all phyla) *Segmentation, *hard exoskeleton (cuticle)~ molting, *jointed appendages; open circulatory system (hemolymph); *extensive cephalization
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Insect characteristics
Outnumber all other forms of life combined Malpighian tubules: outpocketings of the digestive tract (excretion) Tracheal system: branched tubes that infiltrate the body (gas exchange) *Metamorphosis…... *•incomplete: young resemble adults, then molt into adulthood (grasshoppers) *•complete: larval stages (looks different than adult); larva to adult through pupal stage
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The Coelomates: *Deuterostomes, I
1) Phy: Echinodermata (sea stars, sea urchins, sand dollars, sea lilies, sea cucumbers, sea daisies) Spiny skin; sessile or slow moving Often pentaradial Water vascular system by hydraulic canals (tube feet)
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Deuterostomes Chordates Next branch
*Notochord: longitudinal, flexible rod located between the digestive and the nerve cord *Dorsal, hollow nerve cord; eventually develops into the brain and spinal cord *Pharyngeal slits; become modified for gas exchange, jaw support, and/or hearing *Muscular, postanal tail
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Invertebrate chordates
Both suspension feeders….. Subphy: Urochordata (tunicates; sea squirt); mostly sessile & marine Subphy: Cephalochordata (lancelets); marine, sand dwellers *Importance: vertebrates closest relatives; in the fossil record, appear 50 million years before first vertebrate *Paedogenesis: development of sexual maturity in a larva (link with vertebrates?)
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Subphylum: Vertebrata
Retain chordate characteristics with specializations…. *Neural crest: group of embryonic cells near dorsal margins of closing neural tube *Pronounced cephalization: concentration of sensory and neural equipment in the head *Cranium and vertebral column *Closed circulatory system with a ventral chambered heart
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Vertebrate diversity Phy: Chordata Subphy: Vertebrata
Superclass: Agnatha jawless vertebrates (hagfish, lampreys) *Most primitive, living vertebrates
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Vocabulary tetrapods (‘4-footed’) amniotes (shelled egg)
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Superclass Gnathostomata, I
Placoderms (extinct): first with hinged jaws and paired appendages Class: Chondrichthyes~ *Sharks, skates, rays *Cartilaginous fishes; well developed jaws and paired fins; continual water flow over gills (gas exchange); lateral line system (water pressure changes) *Life cycles: *Oviparous- eggs hatch outside mother’s body *Ovoviviparous- retain fertilized eggs; nourished by egg yolk; young born live *Viviparous- young develop within uterus; nourished by placenta
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Superclass Gnathostomata, III
Class: Amphibia *1st tetrapods on land Frogs, toads, salamanders, caecilians Metamorphosis; lack shelled egg; moist skin for gas exchange
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Superclass Gnathostomata, IV
Class: Reptilia Lizards, snakes, turtles, and crocodilians *Amniote (shelled) egg with extraembryonic membranes (gas exchange, waste storage, nutrient transfer); absence of feathers, hair, and mammary glands; *ectothermic; scales with protein keratin (waterproof); lungs; ectothermic (dinosaurs endothermic?)
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Superclass Gnathostomata, V
Class: Aves Birds *Flight adaptations: wings (honeycombed bone); feathers (keratin); toothless; one ovary *Evolved from reptiles (amniote egg and leg scales); endothermic *(4-chambered heart) Archaeopteryx (stemmed from an ancestor that gave rise to birds)
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Superclass Gnathostomata, VI
Class: Mammalia *Mammary glands; hair (keratin); endothermic; 4-chambered heart; large brains; teeth differentiation *Evolved from reptilian stock before birds *Monotremes (egg-laying): platypus; echidna *Marsupials (pouch): opossums, kangaroos, koalas *Eutherian (placenta): all other mammals
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Order: Primates (evolution)
*Characteristics: hands & feet for grasping; large brains, short jaws, flat face; parental care and complex social behaviors Suborder: Prosimii •lemurs, tarsiers Suborder: Anthropoidea •monkeys, apes, humans (opposable thumb) *45-50 million years ago *Paleoanthropology: study of human origins *Hominoid: great apes & humans Hominid (narrower classification): √ australopithecines (all extinct) *√ genus Homo (only 1 exant, sapiens)
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Human evolution Misconceptions:
1- Chimp ancestor (2 divergent branches) 2- Step-wise series (coexistence of human species) 3- Trait unison(all traits at once) vs. mosaic evolution(over time) (*bipedalism, upright, enlarged brain)
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The first humans Ape-human split (5-7 mya)
Australopithecus; “Lucy” (4.0 mya) Homo habilis; “Handy Man” (2.5 mya) Homo erectus; first to migrate (1.8 mya) Neanderthals (200,000 ya) Homo sapiens (100,000 ya?) Multiregional model (parallel evolution) “Out of Africa” (replacement evolution)
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Tissues: groups of cells with a common structure and function (4 types)
Anatomy: structure Physiology: function Type 1- Epithelial: outside of body and lines organs and cavities; held together by tight junctions basement membrane: dense mat of extracellular matrix Simple: single layer of cells Stratified: multiple tiers of cells Cuboidal (like dice) Columnar (like bricks on end) Squamous (like floor tiles) Glandular (can secrete) mucous membrane
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Connective Tissue (6 kinds)
Type 2- Connective Tissue: bind and support other tissues; scattered cells through matrix kinds of fibers: A-Collagenous fibers (collagen protein) non elastic B-Elastic fibers (elastin protein) C-Reticular fibers (thin branched collagen fibers) Loose connective tissue: binds epithelia to underlying tissue; holds organs (has all 3 fiber types) Two types of cells dominate 1-Fibroblasts- secretes the protein for extracellular fibers 2-Macrophages- amoeboid WBC’s; phagocytosis Adipose tissue (specialized form)- fat storage; insulation
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Connective Tissue, Type II
Fibrous connective tissue: parallel bundles of cells 1-Tendons- muscles to bones 2-Ligaments- bones to bones; joints (BOBOLI) Cartilage: collagen in a rubbery matrix (chondroitin); flexible support Bone: mineralized tissue by osteoblast cells Blood: liquid plasma matrix; erythrocytes (RBC’s) carry O2; leukocytes (WBC’s) immunity
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Nervous Tissue, Type III
3-Nervous: senses stimuli and transmits signals from 1 part of the animal to another *Neuron: functional unit that transmits impulses *Cell body (contains nucleus) *Dendrites: transmit impulses from tips to rest of neuron *Axons: transmit impulses toward another neuron or effector
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Muscle Tissue (3 kinds) 4- Muscle: capable of contracting when stimulated by nerve impulses; myofibrils composed of proteins actin and myosin; 3 types: A- Skeletal: voluntary movement (striated) B- Cardiac: contractile wall of heart (branched striated) C- Smooth: involuntary activities (no striations)
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Internal regulation Interstitial fluid: internal fluid environment of vertebrates; exchanges nutrients and wastes *Homeostasis: “steady state” or internal balance *Negative feedback: change in a physiological variable that is being monitored triggers a response that counteracts the initial fluctuation; i.e., body temperature *Positive feedback: physiological control mechanism in which a change in some variable triggers mechanisms that amplify the change; i.e., uterine contractions at childbirth
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Metabolism: sum of all energy-requiring biochemical reactions
*Catabolic processes of cellular respiration Calorie; kilocalorie/C *Endotherms: bodies warmed by metabolic heat *Ectotherms: bodies warmed by environment Basal Metabolic Rate (BMR): minimal rate powering basic functions of life (endotherms) Standard Metabolic Rate (SMR): minimal rate powering basic functions of life (ectotherms)
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Chapter 48 ~ Nervous System
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The Nervous System Neurons Glial cells Axon Dendrite Synapse
Neurons Glial cells Axon Dendrite Synapse Neurotransmitters Action potential Motor neurons Interneurons Sensory neurons Myelin sheath Schwann cells Reflex arc
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Nervous systems Effector cells~ muscle or gland cells
Nerves~ bundles of neurons wrapped in connective tissue Central nervous system (CNS)~ brain and spinal cord Peripheral nervous system (PNS)~ sensory and motor neurons
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Structural Unit of Nervous System
Neuron~ structural and functional unit Cell body~ nucelus and organelles Dendrites~ impulses from tips to neuron Axons~ impulses toward tips Myelin sheath~ supporting, insulating layer Schwann cells~ PNS support cells Synaptic terminals~ neurotransmitter releaser Synapse~ neuron junction
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Simple Nerve Circuit Sensory neuron: convey information to spinal cord Interneurons: information integration Motor neurons: convey signals to effector cell (muscle or gland) Reflex: simple response; sensory to motor neurons Ganglion (ganglia): cluster of nerve cell bodies in the PNS Supporting cells/glia: nonconductiong cell that provides support, insulation, and protection
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Neural signaling Membrane potential (voltage differences across the plasma membrane) *Intracellular/extracellular ionic concentration difference K+ diffuses out (Na+ in); large anions cannot follow….selective permeability of the plasma membrane Net negative charge of about -70mV
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Neural signaling Excitable cells~ cells that can change membrane potentials (neurons, muscle) Resting potential~ the unexcited state of excitable cells Gated ion channels (open/close response to stimuli): photoreceptors; vibrations in air (sound receptors); chemical (neurotransmitters) & voltage (membrane potential changes) Graded Potentials (depend on strength of stimulus): 1- Hyperpolarization (outflow of K+); increase in electrical gradient; cell becomes more negative 2- Depolarization (inflow of Na+); reduction in electrical gradient; cell becomes less negative
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Neural signaling Threshold potential: if stimulus reaches a certain voltage (-50 to -55 mV)…. The action potential is triggered…. Voltage-gated ion channels (Na+; K+) 1-Resting state •both channels closed 2-Threshold •a stimulus opens some Na+ channels 3-Depolarization •action potential generated •Na+ channels open; cell becomes positive (K+ channels closed) 4-Repolarization •Na+ channels close, K+ channels open; K+ leaves •cell becomes negative 5-Undershoot •both gates close, but K+ channel is slow; resting state restored Refractory period~ insensitive to depolarization due to closing of Na+ gates
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Neural signaling “Travel” of the action potential is self-propagating
Regeneration of “new” action potentials only after refractory period Forward direction only Action potential speed: 1-Axon diameter (larger = faster; 100m/sec) 2-Nodes of Ranvier (concentration of ion channels); saltatory conduction; 150m/sec
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Synaptic communication
Presynaptic cell: transmitting cell Postsynaptic cell: receiving cell Synaptic cleft: separation gap Synaptic vesicles: neurotransmitter releasers Ca+ influx: caused by action potential; vesicles fuse with presynaptic membrane and release…. Neurotransmitter
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Neurotransmitters Acetylcholine (most common) •skeletal muscle
Acetylcholine (most common) •skeletal muscle Biogenic amines (derived from amino acids) •norepinephrine •dopamine •serotonin Amino acids Neuropeptides (short chains of amino acids) •endorphin
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Nervous System (know this slide)
Central Nervous System Crainial Nerves Spinal Nerves Peripheral Nervous System Sensory (afferent) Division Sensing external environment Sensing internal environment Motor (Efferent) Division Autonomic Nervous System Sympathetic Nervous System increase energy consumption Parasympathetic Nervous System conservation of energy Somatic Nervous System voluntary, conscious control, muscles
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Vertebrate PNS
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Vertebrate Skeletal Muscle
*Contract/relax: antagonistic pairs w/skeleton *Muscles: bundle of…. Muscle fibers: single cell w/ many nuclei consisting of…. *Myofibrils: longitudinal bundles composed of…. *Myofilaments: Thin~ 2 strands of actin protein and one strand of a regulatory protein Thick~ staggerd arrays of myosin protein
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Vertebrate Skeletal Muscle
Sarcomere: repeating unit of muscle tissue, composed of…. Z lines~sarcomere border I band~only actin protein A band~actin & myosin protein overlap H zone~central sarcomere; only myosin
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**Sliding-filament model
Theory of muscle contraction Sarcomere length reduced Z line length becomes shorter Actin and myosin slide past each other (overlap increases)
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**Actin-myosin interaction
1- Myosin head hydrolyzes ATP to ADP and inorganic phosphate (Pi); termed the “high energy configuration” 2- Myosin head binds to actin; termed a “cross bridge” 3- Releasing ADP and (Pi), myosin relaxes sliding actin; “low energy configuration” 4- Binding of new ATP releases myosin head Creatine phosphate~ supplier of phosphate to ADP
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**Muscle contraction regulation
Relaxation: tropomyosin blocks myosin binding sites on actin Contraction: calcium binds to toponin complex; tropomyosin changes shape, exposing myosin binding sites
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**Muscle contraction regulation
Calcium (Ca+)~ concentration regulated by the…. Sarcoplasmic reticulum~ a specialized endoplasmic reticulum Stimulated by action potential in a motor neuron T (transverse) tubules~ travel channels in plasma membrane for action potential Ca+ then binds to troponin
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The Vertebrate Brain (know this slide)
Forebrain •*cerebrum~ memory, learning, emotion •*cerebral cortex~ sensory and motor nerve cell bodies •*corpus callosum~ connects left (analytical) and right (creative) hemispheres •*thalamus (main input/output from cerebrum); *hypothalamus (hormone production) Midbrain •inferior (auditory) and superior (visual) colliculi Hindbrain •*cerebellum~coordination of movement •*medulla oblongata/ pons~ autonomic, homeostatic functions
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Emotion
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Cerebrum Cerebral hemispheres Cerebral cortex—”gray matter”
Know that there are different lobes for different purposes. You do not need to memorize this information. Cerebral hemispheres Cerebral cortex—”gray matter” Convolutions Cerebral lobes Frontal lobe—conscious thought and muscle control. Parietal Lobes—receive information from skin receptors. Occipital Lobe—receives visual input. Temporal Lobe—has areas for hearing and smelling.
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Pituitary Gland Corpus Callosum
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