Biology Test 2 Study Guide PDF

Questions ​ What increases faster, surface area, or volume? Volume ​ What type of tissue lines a surface? Epithelium ​ What type of tissue is blood? Connective ​ Explain how a thermostat works using a negative feedback loop when the temperature is too low. ○​ Controlled co...

Questions ​ What increases faster, surface area, or volume? Volume ​ What type of tissue lines a surface? Epithelium ​ What type of tissue is blood? Connective ​ Explain how a thermostat works using a negative feedback loop when the temperature is too low. ○​ Controlled condition: Temperature ○​ Receptor: Thermometer ○​ Control center: Thermostat (sends information to the effector if the temp is too low) ○​ Effector: Heater ○​ ​ What part of a negative feedback loop responds to instructions to cause a change? Effector ​ What is mastication and where does it happen? Chewing; oral cavity ​ Food passes through the digestive tract of which animal twice? Rabbit ​ What law relates pressure to volume? Boyle's Law relates pressure and volume. ​ What happens to the volume of the lungs when the diaphragm contracts? When the diaphragm contracts, it moves downward, increasing the volume of the thoracic cavity and the lungs. ​ What happens to the pressure in the lungs? As the volume of the lungs increases, the pressure inside the lungs decreases. ​ What happens to atmospheric pressure? Atmospheric pressure remains relatively constant, but when the lung pressure becomes lower than atmospheric pressure during inhalation, air moves into the lungs to equalize the pressure. ​ Describe the movement of air when the diaphragm contracts. As the diaphragm contracts and the volume of the lungs increases, the pressure inside the lungs becomes lower than the atmospheric pressure. This causes air to move into the lungs from the atmosphere, a process known as inhalation. Features of the Animal Kingdom Multicellularity: ​ Many have complex bodies ​ Most have complex tissue structure Heterotrophy: Obtain energy and organic molecules by ingesting other organisms Active Movement: Move more rapidly and in more complex ways Diversity of Form and Size: Range in size from microscopic to enormous Most Exhibit Sexual Reproduction: Offspring pass through developmental stages Determined/Fixed Body Plan: Morphology of animals determined by developmental cues Complex Tissue Structure ​ Lack Cell Walls ​ Unique Intracellular Communication: Gap junctions Types of Tissues: ​ Connective tissues – Cells embedded in an extracellular matrix (e.g., bone, cartilage) ​ Epithelial tissues – Covers, lines, protects, and secretes ​ Nervous tissue – Coordinates movement, maintains homeostasis ​ Muscle tissue – Powers locomotion Animal Reproduction and Development Most Animals are Diploids (2n): ​ Somatic cells: Diploid ​ Gametes: Haploid Most Animals Reproduce Sexually: ​ Haploid egg and sperm unite (fertilization or syngamy) → diploid zygote ​ Distinguishes them from fungi, many protists, and prokaryotes Exceptions to Sexual Reproduction: ​ Several groups have an asexual phase (e.g., cnidarians, flatworms) ​ Social insect males are often haploid ​ Budding and fragmentation – Hydra, sea anemones ​ Parthenogenesis: Haplodiploidy ○​ Unfertilized eggs → Males (haploid) ○​ Fertilized eggs → Females (diploid) ○​ Found in some vertebrates and insects ○​ Pros/cons: Potential buildup of deleterious mutations, often no need to find mates Early Development After Zygote Forms: 1.​ Cleavage – Series of mitotic cell divisions ○​ After three divisions → 8-cell stage  ○​ Cells continue to divide and rearrange 2.​ Blastula – 6 to 32-cell hollow ‘ball’ ○​ Blastocoel: Internal cavity 3.​ Gastrulation – Forms gastrula ○​ Invagination forms blastopore and archenteron (embryonic gut) ○​ Establishes ectoderm (outer), endoderm (inner), and often mesoderm (middle) germ layers Features Used to Classify Animals Classification Based on Morphology and Development: ​ Symmetry ​ Number of tissue layers ​ Origin of mouth and anus ​ Body plan and cavities Animal Characterization - Based on Body Symmetry Types of Symmetry: ​ Asymmetrical: No symmetry (e.g., Porifera/sponges) ​ Radial: Arranged around a central axis (e.g., jellyfish, comb jellies) ○​ Oral vs. aboral sides ○​ Suited for encountering the environment from any direction (good for stationary or planktonic lifestyles) ​ Bilateral: Divides the body into right and left halves (e.g., most animals) ○​ Allows for cephalization (concentration of sense organs in the head) ○​ Suited for moving forward Animal Characterization - Based on Embryological Development Major Groups: ​ Parazoa (‘beside’ animals): No true tissues or symmetry (e.g., sponges – Phylum Porifera) ​ Eumetazoa (‘true’ animals): Have distinct tissues & symmetry Symmetry and Germ Layers: ​ Radiata (diploblasts): Two germ layers (ectoderm, endoderm), radial symmetry (e.g., cnidarians, ctenophores) ​ Bilateria (triploblasts): Three germ layers (ectoderm, mesoderm, endoderm), bilateral symmetry (most animals) Germ Layers and Specialization: ​ Endoderm: Inner lining of the digestive tract, trachea, lungs ​ Mesoderm: Muscle, bone, cartilage, blood, visceral organs ​ Ectoderm: Outer body epithelium, central nervous system Body Cavity (Coelom) Classification ​ Acoelomates: No body cavity (e.g., flatworms) ​ Pseudocoelomates: "False" body cavity (e.g., nematodes) ​ Coelomates: True body cavity lined with mesoderm (most animals) Early Animal Evolution: ​ Eumetazoa (‘true animals’): Differentiated tissues (e.g., sponge choanocyte cells) ​ Parazoa: No true tissues (e.g., sponges – Porifera) ​ Both groups evolved from a common ancestor resembling modern choanoflagellates Precambrian & Cambrian Periods: ​ Ediacaran Period (635–543 mya): ○​ Ediacaran biota evolved from protists ○​ Choanoflagellates resemble sponge choanocytes ​ Cambrian Period (542–488 mya): ○​ "Cambrian Explosion" – Rapid evolution of many animal phyla ○​ Rise in O2 levels and ocean calcium levels ○​ Predator-prey dynamics and genetic innovations (Hox genes) Post-Cambrian Period: ​ Cretaceous-Paleogene (Tertiary) Boundary (~66 mya): ○​ Meteorite impact + volcanic activity → Severe climate change ○​ Extinction of many species → Opened niches → Mammal & bird radiation Animal Body Plans and Metabolism ​ Symmetry Evolution: ○​ Sponges = No symmetry ○​ Eumetazoa = Radial or Bilateral symmetry ​ Size, Shape, and Metabolism: ○​ Small, unicellular organisms rely on diffusion for nutrients ○​ Surface area-to-volume ratio limits cell size → Larger organisms have more cells, not larger cells Body Planes & Cavities: ​ Sagittal Plane: Divides into right and left portions ​ Midsagittal Plane: Equal right and left halves  ​ Frontal Plane: Separates front and back ​ Transverse Plane: Divides upper and lower portions Four Main Types of Animal Tissues: ​ Epithelial: Lines cavities, open spaces, and surfaces ​ Connective: Provides support, connects tissues ​ Muscle: Generates movement ​ Nervous: Sends electrical signals Squamous Epithelial: avascular ​ Simple: one layer, flat cells (Ex. lungs) ​ Stratified: multiple layers, name the cell shape based on the top layer of cells, is protective since multiple layers (Ex. esophagus) Cuboidal Epithelial: avascular ​ Simple: look like rings, single layer of cells, cube-shaped cells - look at nuclei; very very round (Ex. Thyroid gland) Simple Columnar: avascular ​ single layer of cells, look at the outer layer, has connective tissue. ​ Oval-shaped: cells are stretched out. ​ Microvilli: fuzzy surface at the top, they are in charge of absorption, there to increase surface area. (Ex: Kidneys, intestines) ​ Goblet cells: single-cell glands that produce mucus Pseudostratified Ciliated Columnar Epithelial: avascular ​ It looks like it's stratified (multiple layers of cells) BUT every cell is connected to a basement membrane. SO, only one layer of cells. Has goblet cells. (Ex: Trachea) ​ Cillia: for movement; move the mucus back up to be swallowed and digested, longer than microvilli Connective tissue: Consists of cells (fibroblasts) embedded in a non-cellular matrix ​ Matrix: usually composed of a ground substance ○​ Ground substance: usually contains some combination of collagen, elastic, or reticular fibers used to connect different tissues or give the body structure (blood has unique functions) ​ Fibroblast: build/make fibers (“-blast” means to make something) ​ Adipocyte: an adipose cell, for long-term energy storage, normally in living tissue and filled with lipids so the nucleus will be pushed over to the side, and provide texture and insolation. It looks similar to lung tissue so look at the nuclei. ​ Hyaline(means waxy/glossy) cartilage: the most abundant cartilage in the body,(Ex: makes up the rings of the trachea) ○​ Chondrocytes cartilage cells: located in the lacunae ​ Dense Regular Connective Tissue: cells with matrix in between and filled with collagen fibers, arranged in nice, parallel layers which gives the tissue strength when pulled. (Ex: tenlonds/ligaments) (THIS IS THE ONLY THING THAT SURFACE AREA INCREASES FASTER)  ​ Aereolar: looks like a bunch of strings (fibers), tissue glue; holds other tissues together, not a lot of cells, mostly cells that we see are fibroblasts. The really big fibers are collagen. The thin fibers are elaston fibers to provide stretch. (Ex: around blood vessels to connect muscles) ​ Blood ​ Bone: ○​ Compact: always on the surface, arranged in structures called osteons; Haversian canal in the center and then lamellae (layers), then in the layers you have your osteocytes which are in the lacunae ○​ Spongy: always internal, no Haversion canal in the center so you don't have osteons. Have layers and osteocytes. The matrix in between the bone is very hard (osteoblast) Muscle Tissue: for movement  ​ Skeletal: on the skeleton and tongue, moves your skeleton, the only type that is consciously controlled, very long cells arranged in a parallel fashion and multi-nucleus. Conformed from the fusion of many cells. Nuclei are peripheral - pushed to the sides. Are striated. ​ Cardiac: Striated - very fine lines. Only in the cardiac muscle of the heart, branching cells, have one nucleus each, and have striations. Where one cell meets another there are intercalated disks: only cardiac muscle has this. ​ Smooth: located everywhere, no striations - smooth appearance. Spindle-shaped: widest in the center where the nucleus is and then tapers off at the ends. Nervous Tissue: ​ Neurons: send electrical messages but cannot divide and do not get repaired (repair only happens in the peripheral nervous system) ○​ Dendrites: how a neuron receives messages ​ Neuroglia: for support and nourishment of neurons, can divide Homeostasis/Thermoregulation: ​ Homeostasis aims to keep internal conditions around a set point ○​ If conditions stray too far from the set point homeostatic mechanisms kick in ​ Negative feedback loops (reverses): The set point can potentially change over time (alteration), but homeostasis will still work towards a new set point, much more common (Ex: Fever) ○​ Counteracts any internal changes (reverses the direction of the change) ○​ Most biological systems are on negative feedback (Ex: Temperature, Glucose, pH, Blood Calcium)  ​ Acclimatization: changes in one organ system to maintain a set point in another organ system (altitude example - Kidneys produce EPO) ​ Positive feedback loop (build): Maintains and potentially strengthens the response to a stimulus, Not many biological systems are on positive feedback (Ex: Childbirth, Platelet plug formation) ​ Must maintain a relatively constant internal temperature to keep enzymes working and avoid denaturation ​ Thermoregulatory control by the hypothalamus ​ Temperature is maintained in several different ways; heat can be exchanged by four mechanisms: ○​ Radiation ○​ Convection: transfer of heat through liquid or gas ○​ Conduction: heat transfer by direct contact ○​ Evaporation: sweat evaporates from your skin Digestion: ​ Herbivores are animals whose primary food source is Plant-based, Also known as primary consumers. ​ Carnivores are animals that eat other animals. ○​ Obligate carnivores are those that rely entirely on animal flesh to obtain their nutrients. ○​ Facultative carnivores are those that also eat non-animal food in addition to animal food, but generally do best, eating animals. ​ Omnivores are animals that eat both plant- and animal-derived food – and do well eating either Digestive Tracts: ​ Incomplete: single opening = Gastrovascular cavity (Ex: Planarian) Food enters through the mouth and muscular pharynx, Wastes exit through the mouth and muscular pharynx, Lacks specialized parts. ​ Complete: two openings = Alimentary canal (Ex: Earthworm) Food enters through the mouth Wastes exit through the anus Tongue ​ Mastication: Keeps food between the teeth during chewing. ​ Deglutition: Aids in swallowing. Teeth ​ Mastication: Chewing increases the surface area of food, allowing enzymes to act more efficiently. Salivary Glands ​ Parotid, Submandibular, Sublingual: Produce saliva. ​ Saliva: Moistens food to form a bolus and contains digestive enzymes. ​ Lingual Lipase: Digests fats, not active until in the stomach ​ Salivary Amylase: Breaks down starches into disaccharides. Swallowing (deglutition) ​ Pharynx: Where digestive and respiratory passages come together. The soft palate closes off the nasopharynx. ​ Epiglottis: cartilage covered with a mucus membrane that moves down to close the opening into the trachea. Keeps food from air passages (most of the time). Takes food to the stomach by the peristalsis. ○​ Peristalsis: rhythmic muscle contraction to move contents in tubular organs. Not necessary unless lying down. Contracts behind the bolus of food and relax in front of the bolus of food to push it toward the stomach and through the intestines Stomach ​ Food becomes chyme after digested, and lingual and gastric lipase are active here to turn triglycerides into monoglycerides and fatty acids (breaks ester bonds between glycerol and fatty acids). ​ Stomach wall: has deep folds(rugae) that disappear as the stomach fills to an approximate volume of one liter. ○​ We have three layers to help churn food together. ​ Epithelial Lining: has millions of gastric pits which drain gastric glands. ​ Pepsin: a hydrolytic enzyme that acts on breaking down proteins to produce peptides. ○​ Pepcynigen: inactive form. ​ Pecyniden + HCL = Pepsin HUMAN DIGESTIVE TRACT ​ Food mixed with gastric juices becomes chyme. The junction between the stomach and small intestine is controlled by a sphincter. When the sphincter relaxes, a small quantity of chyme passes into the small intestine. Small Intestine ​ Duodenum ○​ First Segment of the small intestine ○​ The liver, gallbladder, and pancreas are all attached here ○​ Chyme from the stomach enters the duodenum ○​ Mixes with secretions from the liver and pancreas Liver ​ Produces bile, which is stored in the gallbladder ​ Bile contains bile salts which break up fat into fat droplets via emulsification. ​ Helps maintain glucose concentration in blood by converting excess into glycogen Pancreas ​ Endocrine gland: Produces insulin and glucagon which control blood glucose levels  ​ Exocrine gland: Produces pancreatic juice and digestive enzymes that can break down all four classes of macromolecules (proteins, lipids, nucleic acids, carbohydrates) into the duodenum. Also produces bicarbonate which is important to raise the levels of pH so that the enzymes work since the chyme is very acidic. ○​ Pancreatic amylase: Digests starch to (disaccharides) maltose ○​ Trypsin: Digests protein to peptides ○​ Pancreatic Lipase: Digests fat droplets to glycerol and fatty acids ​ Epithelial cells of the intestine also produce enzymes (brush border enzymes that have microvilli) that complete the digestion of peptides (proteins) and sugars. CARBOHYDRATE DIGESTION ​ Digestion of carbohydrates is performed by several enzymes. ○​ Amylase and maltase: Break down starch and glycogen into glucose ○​ Sucrase and lactase: Break down sucrose (table sugar) and lactose (milk sugar) ​ Gigunum: middle part of the small intensive which is the main site of absorption. PROTEIN DIGESTION ​ Starts in the stomach with pepsin breaking down proteins into peptides (short chains of 4-9 amino acids). ​ In the duodenum, trypsin, elastase, and chymotrypsin reduce peptides to smaller peptides. ​ Brush Border Enzymes: Carboxypeptidase, dipeptidase, and aminopeptidase reduce peptides to free amino acids. (absorbable) LIPID DIGESTION ​ Begins in the stomach with lingual lipase and gastric lipase. ​ The bulk of digestion occurs in the small intestine due to pancreatic lipase. ​ When chyme enters the duodenum, CCK hormonal responses trigger the release of bile, produced in the liver and stored in the gallbladder. ​ Bile aids in lipid digestion, primarily triglycerides, through emulsification. STEPS OF DIGESTION: ABSORPTION ​ Only monosaccharides can be absorbed. ​ The mucous membrane of the small intestine has ridges and furrows, giving it a corrugated surface. ​ Lacteals: Lymphatic capillaries that travel through the lymph before going into the blood. ​ Villi: Ridges on the surface, which contain smaller ridges, and microvilli, greatly increasing the absorptive area.  ○​ Each villus contains blood capillaries and a lymphatic capillary (lacteal). Large Intestine ​ Includes cecum, colon, rectum, and anal canal ​ Larger in diameter, but shorter in length than the small intestine ​ Absorbs water, salts, and some vitamins ​ Cecum has a small projection – appendix ​ Colon is subdivided into ascending, transverse, descending, and sigmoid colons. ​ Opening to the anal canal – Anus for elimination Liver ​ Bile Production: Bile emulsifies lipids, making them more soluble in water for enzymatic action. Gallbladder ​ Bile Storage: Stores bile produced by the liver. Pancreas ​ Duodenum: the first part of the small intestine where the liver and gallbladder connect to the pancreas ​ pH Regulation: Makes the small intestine more alkaline. ○​ Enzyme Production: Produces enzymes that break down carbohydrates, lipids, proteins, and nucleic acids. Digestive Systems in Different Animals Carnivores - Dentition: Pointed incisors and enlarged canines for tearing flesh; jagged molars for tearing. Herbivores - Dentition: Sharp incisors for tearing leaves; large, flat molars for grinding plant material. Omnivores - Dentition: Combination of chisel-shaped incisors, pointed canines, and flat molars for a varied diet. Birds ​ Crop: Stores food, part of the GI tract. ​ Proventriculus: Contains digestive enzymes. ​ Gizzard: Mechanical digestion with grinding action. ​ Cloaca: One opening to excrete urine and feces Ruminants (e.g., cows, goats) Four Stomachs: ​ Rumen and Reticulum: contains prokaryotes and protists/or microbes in the rumen and reticulum to digest cellulose fiber. ​ Omasum: removes water. ​ Abomasum: enzymes produced by the animal. Regurgitation -Chewing cud for further breakdown. Monogastric Systems ​ Humans: Single stomach, small and large intestines, small cecum. ​ Rabbits digest food twice, a large cecum is used for fermentation, and cecotropes are re-ingested for additional nutrition. NUTRITION: CARBOHYDRATES ​ Carbohydrates are present in food in the form of sugars, starch, and fiber. ○​ Monosaccharides: ​ Glucose ​ Fructose ○​ Disaccharides: ​ Lactose (milk sugar) ​ Sucrose (table sugar) ○​ Polysaccharides: ​ Plants store glucose as starch and cellulose ​ Animals store glucose as glycogen NUTRITION: PROTEINS ​ Adequate protein formation requires 20 different types of amino acids. ​ Adults require 8 essential amino acids from the diet; children require 9. ​ Some foods, such as meat, milk, and eggs, provide all 20 amino acids (complete proteins). ​ Vegetables supply one or more essential amino acids but are deficient in at least one. ​ Vegetarians should combine plant products to provide all the essential amino acids. ​ Kids also need Arginine. NUTRITION: LIPIDS ​ Fat, oils, and cholesterol ​ Essential for the storage and activity of fat-soluble vitamins A, D, E, and K. ​ Provide energy, at nine calories per gram. ​ Fat storage is essential to protect internal organs and help insulate against cold temperatures. ​ Saturated fats: ○​ Solids at room temperature ○​ Usually come from animals ○​ Found in butter and meats, such as marbled red meats and bacon ○​ Palm oil and coconut oil are high in saturated fats NUTRITION: VITAMINS ​ Fat-soluble: should be taken with food, can overdose because they are stored in fat. Minerals ​ Definition: Inorganic essential nutrients that must be obtained from food. ​ Functions: Help in structure and regulation and act as co-factors. Dogfish Shark ​ Teeth: Specialized for grasping and tearing prey. ​ Liver: Produces a large amount of oil, aiding in buoyancy. ​ Spiral Intestine: Increases surface area for absorption, compensating for a shorter digestive tract. Bullfrog - Digestive System: Adapted for swallowing prey whole. Fetal Pig - Digestive System: Closely resembles that of humans, making it a common model for study. TGE (Transmissible Gastroenteritis) ​ Definition: A highly contagious viral disease affecting the digestive system of pigs that breaks down the villi. ​ Effects: Severe diarrhea and dehydration. Pigs eventually starve. Respiratory and Circulatory Systems  ​ Function: Deliver oxygen to cells and remove carbon dioxide. ​ Oxygen is required. ​ Gas Exchange: Essential for aerobic respiration, producing energy and carbon dioxide as a waste product. ​ Gas Exchange in Multicellular Organisms: Larger organisms require a circulatory system for efficient delivery of gases and waste removal. ​ Role of Partial Pressures: Gases diffuse based on their partial pressures, independent of each other. OXYGEN REQUIREMENT FOR CELLS ​ All cells require oxygen for use in the efficient production of energy through cellular respiration. ​ One of the major physiological challenges facing all multicellular animals is obtaining sufficient oxygen and disposing of excess carbon dioxide. GAS EXCHANGE BETWEEN ALVEOLI AND BLOOD ​ In vertebrates, gases diffuse into the aqueous layer covering the epithelial cells that line the respiratory organs. ​ Diffusion is passive, driven only by the difference in O2 and CO2 concentrations on the two sides of the membranes and their relative solubility in the plasma membrane.​ ○​ High O2 in alveoli moves into the blood. ○​ High CO2 in blood moves into the alveoli. ​ The opposite occurs in the tissue. Diffusion Mechanism ​ Driven by differences in partial pressures of gases. Types ​ External Respiration: Oxygen diffuses into the blood, and carbon dioxide diffuses out (between alveoli and pulmonary capillaries). ​ Internal Respiration: Oxygen diffuses from the blood into cells, and carbon dioxide diffuses into the blood (between systemic capillaries and body tissues). Fick’s Law of Diffusion ​ The rate depends on: ○​ Diffusion constant ○​ Surface area ○​ Partial pressure gradient ○​ Distance Factors Affecting Diffusion ​ Surface Area: Larger = increased rate. ​ Partial Pressure Gradient: Greater difference = increased rate. ​ Distance: Shorter = increased rate. Adaptations in Different Organisms ​ Unicellular Organisms: Rely on direct diffusion. ​ Small Multicellular Organisms: May not need a circulatory system and can rely directly upon the diffusion of gases. ​ Amphibians: Use skin, lungs, and oral cavity for gas exchange. ​ Insects: Have a tracheal system. ​ Fish: Use gills with countercurrent exchange. ○​ Gills: increase surface area for diffusion. ○​ Move water into the mouth through the gills and out of the fish through the open operculum or gill cover. ○​ Blood and gases move in opposite directions (counter-current exchange). ​ Terrestrial Animals: Use lungs to minimize evaporation by moving air through a branched tubular passage. ​ Mammals: Have alveoli to increase surface area in their lung tissue. Partial Pressure Calculations ​ Sea Level: Total pressure = 760 mmHg. ​ Mount Everest Base Camp: Total pressure = 401 mmHg. ​ Partial Pressure of Oxygen: ○​ At base camp: 401 × 0.2095 ≈ 84 mmHg (about half of sea level). Implications for Climbers ​ Reduced Gradient: Less oxygen diffusion at high altitudes. ​ Supplemental Oxygen: Used to increase oxygen diffusion. Lung Structure and Function ​ Mammals: Lungs with millions of alveoli for efficient gas exchange. ​ Ventilation: ○​ Inhalation: Diaphragm contracts, increasing thoracic volume, and decreasing pressure.Passes through the larynx, glottis, and trachea. ​ External Intercostals: the outer layer of muscle that helps to elevate the ribs to expand the thoracic cavity.  ○​ Exhalation: The Diaphragm relaxes, decreasing volume, and increasing pressure. Bifuricates into the right and left bronchi which enter each lung and further subdivide into bronchioles. ​ Bronchi: have cartilage ​ Bronchioles: surrounded by smooth muscle ○​ Produces negative pressure which draws air into the lungs. (Pressure and volume are inversely related). Bird Respiratory System ​ Unidirectional Flow: Most efficient system. ​ Air Sacs: Move air through the lungs. External Vs Internal Respiration External: Gas exchange between the ovuloli in the lungs and the pulmonary capillary (look at the partial pressures of the different gasses, diffuse independently from high partial pressure to low partial pressure.) O2=104 mmHg CO2=40 mmHg Internal: Oxygen will be low in the tissue to make ATP. O2=40 mmHg CO2=46 mmHg (Low partial pressure to high partial pressure). Hemoglobin ​ It consists of four polypeptide chains: two (alpha) and two (beta) ○​ Each chain is associated with a heme group ○​ Each heme group has a central iron atom that can bind a molecule of O2 ​ Hemoglobin loads up with oxygen in the lungs, forming oxyhemoglobin ​ Hemoglobin’s affinity for O2 is affected by pH and temperature ○​ The pH effect is known as the Bohr shift (we want it to happen at the tissues) ​ Increased CO2 in blood increases H+ ​ Lower pH reduces hemoglobin’s affinity for O2 ​ Facilitates oxygen unloading in the tissue ​ If there are high levels of CO2, that means that oxygen is needed – the hemoglobin lets go of the oxygen ○​ Increasing temperature has a similar effect ​ The oxygen dissociation curve demonstrates that, as the partial pressure of oxygen increases, more oxygen binds hemoglobin. However, the affinity of hemoglobin for oxygen may shift to the left or the right depending on environmental conditions. ○​ Reduced affinity means more likely to give it up (right shift) ○​ Carbon dioxide doesn't compete with oxygen. Invertebrate Circulatory Systems  ​ Sponges, cnidarians, and nematodes lack a separate circulatory system ​ Sponges circulate water using many incurrent pores and one excurrent pore ​ Hydra circulates water through a gastrovascular cavity (also for digestion) ​ Nematodes are thin enough that the digestive tract can also be used as a circulatory system ​ Invertabrits: Larger animals require a separate circulatory system for nutrient and waste transport ○​ Open circulatory system ​ There is no distinction between circulating and extracellular fluid ​ Fluid called hemolymph ○​ Closed circulatory system ​ Distinct circulatory fluid enclosed in blood vessels and transported away from and back to the heart ​ Separate from the blood Vertebrate Circulatory Systems ​ Fish, amphibians, reptiles, mammals ○​ Main differences: number of heart chambers and how many circuits there are. ○​ Fish: Blood is pumped through the gills, and then to the rest of the body. ​ Evolved a true chamber-pump heart (2-chambered heart) ○​ Amphibians: Advent of lungs required a second pumping circuit, or double circulation ​ Pulmonary circulation moves blood between the heart and lungs ​ Systemic circulation moves blood between the heart and the rest of the body ​ 3 chambered heart ○​ Reptile: 3-chambered heart ​ 2 atria and 2 ventricles ​ But there is incomplete separation of the ventricles Mammals, Birds, and Crocodilians ​ 4 Chambers: ○​ Right Atrium: Receives deoxygenated blood → Right Ventricle → Lungs. ○​ Left Atrium: Receives oxygenated blood → Left Ventricle → Body. ○​ 4 chambers work to circulate blood efficiently. Characteristics of Blood Vessels ​ Blood Flow Pathway: ○​ Arteries → Arterioles → Capillaries → Venules → Veins → Heart. ​ Arterioles: finest, microscopic branches of the arterial tree ​ Blood Vessel Layers: ○​ Composed of Four Tissues: Endothelium, Elastic Fibers, Smooth Muscle, and Connective Tissue ​ Smooth Muscle: arteries have more smooth muscle than veins do ​ Connective Tissue: Walls too thick for exchange of materials across the wall ○​ Capillaries: Single-layered endothelial cells for rapid gas exchange and metabolites between blood and body cells. Ventilation in Different Organisms ​ Dogfish Shark: Uses gill slits for respiration. ​ Frog Respiration: Uses skin, lungs, and buccal cavity. Invertebrate Nervous Organization/Evolution of the Nervous System: ​ Hydras ○​ Nerve net - composed of neurons in contact with one another ○​ Also in contact with contractile epitheliomuscular cells ​ Planarians ○​ Ladder-like nervous system ○​ Cephalization - a concentration of ganglia and sensory receptors in the head ​ Annelids, Arthropods and Mollusks ○​ Complex animals ○​ True nervous systems (true brain) ​ Changes in the forebrain (the most recently evolved portion of the brain) ​ Starfish (seastar) ○​ Nerve ring relay station - no brain ​ Arthropods ○​ Dorsal brain-3 parts; ventral segmental ganglia (act as brains!) ​ Vertebrates ○​ Separation of the central and peripheral nervous systems. Nervous Tissue ​ Neurons ○​ The cell body contains the nucleus ○​ Dendrites receive signals from sensory receptors ​ Axon ○​ conducts nerve impulses ○​ Covered by myelin sheath ○​ Any long axon is also called a nerve fiber Neuron Communication ​ Signals are possible because each neuron has a charged cellular membrane (a voltage difference between the inside and the outside). The charge of this membrane can change in response to neurotransmitter molecules released from other neurons and environmental stimuli. ​ Charged Membranes ○​ Voltage-gated ion channels regulate the relative concentrations of different ions inside and outside the cell. ○​ The difference in total charge between the inside and outside of the cell is called the membrane potential ○​ Sodium Potassium Pump: It actively transports sodium (Na⁺) and potassium (K⁺) ions across the cell membrane. Specifically, it pumps 3 sodium ions out of the cell and 2 potassium ions into the cell. ○​ Leakage channels: let different ions on or out of the cell. Have more potassium leakage channels. ○​ Anions: large anionic negatively charged ions Chemical Synapse ​ Calcium enters -> affects synaptic vesicles in the terminal that contain neurotransmitters (how a neuron sends messages) -> releases a neurotransmitter by exocytosis (electrical message to chemical message) -> neurotransmitter binds to receptor-> receptor is connected to a channel that opens (ligand-gated channel) -> sodium moves through the channel (if we have positive charges coming in, it depolarizes our cell - if a threshold is met, an action potential occurs) ​ Action Potential: involves voltage-gated channels Musculoskeletal System Function ​ General function is to cause or control movement, more specifically: ○​ Support: maintain an upright posture ○​ Allow movement: body transport, manipulation objects ○​ Protect ​ Exoskeleton: External skeleton that consists of a hard encasement on the surface of an organism. ○​ It provides defense against predators, supports the body, and allows for movement through the contraction of attached muscles. ○​ Arthropods such as crabs and lobsters have exos keletons that consist of 30–50 percent chitin ​ a polysaccharide derivative of glucose ​ strong but flexible ○​ Because the exoskeleton is acellular the Skeleton does not grow with organism and Must be shed ​ Endoskelotton: Consists of hard, mineralized structures located within the soft tissue of organisms. ○​ Endoskeletons provide support for the body, protect internal organs, and allow for movement through contraction of muscles attached to the skeleton. Muscular Tissue ​ The body contains three types of muscle tissue: skeletal muscle, smooth muscle, and cardiac muscle, visualized here using light microscopy. ​ Smooth muscle cells are short, tapered at each end, and have only one plump nucleus in each. ​ Cardiac muscle cells are branched and striated, but short. ​ The cytoplasm may branch, and they have one nucleus in the center of the cell Skeletal Muscle Tissue ​ A skeletal muscle cell is surrounded by a plasma membrane called the sarcolemma with a cytoplasm called the sarcoplasm. ​ A muscle fiber is composed of many fibrils, packaged into orderly units. ​ Sarcomere: the region from one Z line to the next Z line. Many sarcomeres are present in a myofibril, resulting in the striation pattern characteristic of skeletal muscle ​ ATP and Muscle Contraction: The cross-bridge muscle contraction cycle, which is triggered by Ca2+ binding to the actin active site, is shown. With each contraction cycle, actin moves relative to myosin. Skeletal Muscle Structure: ​ Muscle Fiber: A single skeletal muscle cell, multinucleated. ​ Sarcolemma: The plasma membrane of a muscle fiber. ​ Sarcoplasm: The cytoplasm of a muscle fiber. ​ Myofibrils: Long protein filaments within the sarcoplasm, responsible for contraction. ​ Sarcomeres: The repeating functional units of a myofibril, containing the contractile proteins. Sarcomere Structure: ​ Zlines (discs): Boundaries of a sarcomere. ​ Thin filaments: Composed primarily of actin, anchored to the Zlines. ​ Thick filaments: Composed primarily of myosin, located in the center of the sarcomere. ​ A band: The region of the sarcomere spanning the entire length of the thick filaments. ​ I band: The region containing only thin filaments, found on either side of the Z line. ​ Zone of Overlap: The area where thick and thin filaments overlap. Sliding Filament Model of Contraction: ​ Muscle contraction occurs when the thin and thick filaments slide past each other, increasing their overlap. ​ Myosin heads on the thick filaments bind to actin on the thin filaments, pulling the thin ​ filaments toward the center of the sarcomere (M line). ​ This shortens the sarcomere, and many sarcomeres shortening simultaneously leads to muscle contraction. Requirements for Contraction: ​ ATP: Provides energy for the myosin heads to detach and reattach to actin during the contraction cycle. ​ Calcium (Ca2+): Essential for the binding of myosin to actin. Excitation-Contraction Coupling: 1.​ Nerve Impulse: A motor neuron releases the neurotransmitter acetylcholine (ACh) at the neuromuscular junction. 2.​ Muscle Action Potential: ACh binds to receptors on the sarcolemma, triggering an action potential (electrical signal) that spreads across and into the muscle fiber via T tubules. 3.​ Calcium Release: The action potential near the sarcoplasmic reticulum causes the release of calcium ions (Ca2+) into the sarcoplasm. 4.​ Calcium Binds to Troponin: Calcium binds to the regulatory protein troponin, causing a shift in the position of tropomyosin. 5.​ Binding Sites Exposed: The shift in tropomyosin exposes the myosin-binding sites on the actin filaments, allowing the contraction cycle to begin. Contraction Cycle:  1.​ Myosin Head Cocked (ATP Hydrolysis): ATP bound to the myosin head is hydrolyzed to ADP and phosphate (Pi), putting the myosin head in a high-energy, "cocked" position. 2.​ Cross-bridge Formation: The energized myosin head binds to the exposed myosin-binding site on actin, forming a cross-bridge. 3.​ Power Stroke: The myosin head pivots and pulls the actin filament toward the center of the sarcomere (M line). ADP and Pi are released during this step. 4.​ Cross-bridge Detachment: A new ATP molecule binds to the myosin head, causing it to detach from the actin filament. The cycle is ready to repeat as long as calcium is present. Reflex Arc: ​ A reflex arc is a neural pathway that controls a reflex, which is an automatic, rapid response to a stimulus. ​ A simple reflex arc involves a sensory receptor, sensory neuron, interneuron (in the spinal cord), motor neuron, and effector (muscle). ​ Example: The withdrawal reflex when you step on a pin. Excretion and Osmoregulation: ​ Excretion: The process of removing metabolic waste products from the body. Different organisms have evolved various excretory organs to carry out this function. ○​ Unicellular organisms: Excrete waste by exocytosis. ○​ Flatworms (Planarians): Use flame cells with cilia to filter and excrete waste through protonephridia. ○​ Earthworms (Annelids): Employ nephridia with a ciliated nephrostome to filter body fluids and excrete waste through nephridiopores. ○​ Insects (e.g., Grasshoppers, Bees): Utilize Malpighian tubules linked to their gut to excrete uric acid and reabsorb salts and water into their hemolymph. ​ Osmoregulation: The active regulation of water and salt balance within the body ○​.Osmoconformers: Marine animals that maintain an internal environment isotonic to their surroundings, thus minimizing water gain or loss. ○​ Osmoregulators: Organisms that actively regulate their internal osmotic pressure to maintain a stable internal environment, despite fluctuations in their external environment. ​ Freshwater fish: In a hypotonic environment, they absorb water through their skin and excrete large amounts of dilute urine to maintain osmotic balance. Additionally, they actively uptake ions from their environment. ​ Saltwater fish: In a hypertonic environment, they lose water through their skin and excrete concentrated urine to conserve water. They also actively excrete excess ions through their gills ​.Terrestrial animals: Face challenges in conserving water. ○​ They lose water through excretion, respiration, and sometimes through specialized salt glands. ○​ They drink water to compensate for water loss. ○​ Some produce uric acid, which requires less water for excretion, as a water conservation strategy. ​ The Nephron: The functional unit of the kidney in vertebrates, responsible for urine formation.  ○​ Filtration: Blood is filtered in the glomerulus, and the filtrate is collected in Bowman's capsule. ○​ Reabsorption: Essential molecules and water are reabsorbed from the filtrate back into the bloodstream. ○​ Secretion: Additional waste products and ions are secreted from the blood into the filtrate. ​ Evolution of the Nephron: ○​ Cartilaginous fish (e.g., Sharks): Have nephrons that reabsorb urea, contributing to their osmoconforming strategy. ○​ Amphibians (e.g., Frogs): Possess nephrons with specialized segments (proximal and distal tubules) that can respond to hormones like antidiuretic hormone (ADH) to regulate water reabsorption. ○​ Mammals (e.g., Pigs, Desert Rats): Exhibit further specialization in nephron structure, including the loop of Henle. Longer loops of Henle are found in animals adapted to arid environments for increased water reabsorption. ​ Nitrogenous Waste: ○​ Ammonia: Highly toxic and soluble in water; common in aquatic animals. ○​ Urea: Less toxic than ammonia, but requires a moderate amount of water for excretion; common inmammals and amphibians. ○​ Uric acid: Requires very little water for excretion, but is energetically expensive to produce; common in reptiles, birds, and insects inhabiting arid environments. Reproduction: ​ Asexual Reproduction: Reproduction without the involvement of gametes (sperm and egg). ○​ Budding: Seen in Hydra. ○​ Splitting/Fragmentation: Observed in flatworms, sponges, annelids, and echinoderms. ​ Parthenogenesis: Development of an unfertilized egg into a complete individual. ​ Sexual Reproduction: Reproduction involves the fusion of gametes from two parents. ○​ Dioecious: Separate sexes (male and female). ○​ Monoecious (Hermaphroditic): Having both male and female reproductive organs in the same individual. ​ Modes of Reproduction: ○​ Oviparity: Laying eggs. Examples: Reptiles, and birds. ○​ Ovoviviparity: Eggs develop internally and hatch within the mother's body but without placental nourishment. Examples: Dogfish sharks, seahorses. ○​ Viviparity: Live birth. Examples: Most mammals. ​ Reproductive Strategies in Different Animals: ○​ Dogfish Sharks: Internal fertilization with ovoviviparous reproduction. Embryos develop in eggs within the mother's uterus and are nourished by a yolk sac. ○​ Amphibians (e.g., Frogs): External fertilization with oviparous reproduction. Males fertilize eggs externally during amplexus. ○​ Mammals (e.g., Pigs): Internal fertilization with viviparous reproduction. Placental mammals nourish and provide oxygen to developing embryos through a placenta.