General Biology 2 5-8 Modules - PDF

General Biology 2 Modules 5-8 MODULE 5.1: THE EVOLUTION & DIVERSITY OF Most reproduce sexually, with the diploid stage ANIMALS usually dominat...

General Biology 2 Modules 5-8 MODULE 5.1: THE EVOLUTION & DIVERSITY OF Most reproduce sexually, with the diploid stage ANIMALS usually dominating the life cycle. Animals: Multicellular, heterotrophic eukaryotes with Cleavage: It is the cell division that the zygote tissues that develop from embryonic layers. undergoes after a sperm fertilizes an egg. Most animals are mobile and use traits such as Cleavage leads to the formation of a multicellular, strength, speed, toxins, or camouflage to detect, hollow blastula. capture, and eat other organisms. Ex: Chameleon captures insect prey with its The blastula undergoes gastrulation, forming a long sticky, quick-moving tongue. gastrula with different layers of embryonic tissues. Nutritional Mode: Heterotrophs that ingest their REPRODUCTION AND DEVELOPMENT OF ANIMALS food. Most animals have at least one larval stage. Larva: It is sexually immature and morphologically CELL STRUCTURE AND SPECIALIZATION OF ANIMALS distinct from the adult; it eventually undergoes Overall animals have the following characteristics in metamorphosis (frogs and caterpillars) to become terms of their cell structure: a juvenile. Multicellular eukaryotes There are NO cell walls Juvenile: It resembles an adult but is not yet sexually Bodies are held together by structural mature. proteins such as collagen Hox Genes: A class of homeotic genes that provide Nervous Tissue & Muscle Tissue: These are the positional information during animal embryonic unique, defining characteristics of animals. development. Most animals, and only animals, have these Tissues: Groups of similar cells that act as a genes that regulate the development of functional unit body form. REPRODUCTION AND DEVELOPMENT OF ANIMALS Although the Hox family of genes has been highly conserved, it can produce a wide diversity of animal morphology. 1  Paralogues: When two species share similar Key events in life’s history include the origins of ancestral genes. Two segments of DNA that unicellular and multicellular organisms and the have shared ancestry. colonization of land History of Animals spans more than half a billion Geologic Record: It is divided into Hadean, years Archaean, Proterozoic, and Phanerozoic eons. More than 1.3 million animal species have been named to date; far more are estimated to exist. The common ancestor of all living animals likely lived between 700 and 770 million years ago. The Fossil Record documents the history of life Fossil Record: It reveals changes in the history of life on Earth. It shows changes in the kinds of organisms on Earth over time. Sedimentary Rock: These are deposited into layers called strata and are the richest source of fossils. Radiometric Dating: This is how the absolute ages of fossils can be determined The Phanerozoic eon includes the last half billion A radioactive “parent” isotope decays to a years. It is divided into 3 eras: “daughter” isotope at a constant rate. Paleozoic Mesozoic Cenozoic PHOTOSYNTHESIS AND THE OXYGEN REVOLUTION O2 produced by oxygenic photosynthesis reacted with dissolved iron and precipitated out to form banded iron formations. By about 2.7 million years ago, O2 began accumulating in the atmosphere and rusting iron-rich terrestrial rocks. This oxygen revolution from 2.7 to 2.3 billion years ago caused the extinction of many prokaryotic groups (they found it to be toxic). Some groups survived and adapted using cellular respiration to harvest energy. 2  THE FIRST EUKARYOTES The origin of multicellularity requires the evolution of The oldest fossils of eukaryotic cells date back to 1.8 new ways for cells to adhere (attach) and signal billion years. (communicate) to each other. Eukaryotes have a nuclear envelope, mitochondria, Molecular Analysis: Revealed similarities between endoplasmic reticulum, and a cytoskeleton. genes coding for proteins involved in adherence and attachment in choanoflagellates and animals. The Endosymbiotic (Endosymbiont) Theory: The CCD Domain: The protein present in animals prokaryotic ancestors of mitochondria and plastids and is also involved with choanoflagellates. probably gained entry to the host cell as undigested prey or internal parasites. NEOPROTEROZOIC ERA (1 Billion - 542 Million Years Ago) In the process of becoming more interdependent, Multicellular eukaryotes were formed during this the host and endosymbionts would have become era. a single organism. Ediacaran Biota: An assemblage of larger and more diverse soft-bodied organisms that lived about 560 million years ago (Mollusks, Sponges). Early animal embryos and evidence of predation have also been found in Neoproterozoic rocks. Ex: The 550-million-year-old fossil of Cloudina was attacked by a predator that bore a hole through its shell. PALEOZOIC ERA (542 - 251 Million Years Ago) THE ORIGIN OF MULTICELLULAR ANIMALS Cambrian Explosion: This marks the earliest fossil A second wave of diversification occurred when appearance of many major groups of living animals multicellularity evolved, giving rise to algae, plants, (535 - 525 million years ago). These groups include fungi, and animals. arthropods (insects), echinoderms, and chordates. Choanoflagellates: These are a group of protists Bilaterians: These were most of the fossils found that have morphological and molecular evidence in the Cambrian explosion and these organisms as the closest relatives to animals. have the following traits: Bilaterally symmetric form Complete digestive tract One-way digestive system The Cambrian Explosion also refers to the sudden appearance of fossils resembling modern animal phyla in the Cambrian period. A few animal phyla appear even earlier: sponges, cnidarians, and mollusks. 3 Hypotheses regarding the Cambrian Explosion and The ancestors of plesiosaurs were reptiles that the decline of the Ediacaran Biota are the returned to the water. following: New predator-prey relationships Dinosaurs were the dominant terrestrial vertebrates. A rise in atmospheric oxygen levels The first mammals emerged. The evolution of the Hox gene complex CENOZOIC ERA (65.5 Million Years Ago to the Present) The beginning of the Cenozoic Era followed the mass extinctions of both terrestrial and marine animals. These extinctions included the large, non flying dinosaurs and the marine reptiles. Mammals increased in size and exploited vacated ecological niches. Lastly, the global climate cooled. BIG FIVE MASS EXTINCTION EVENTS In each of the five mass extinction events, 50% or more of marine species became extinct. The Colonization of Land Animal diversity continued to increase through the Paleozoic but was punctuated by mass extinctions. Fungi, plants, and animals began to colonize land about 500 million years ago. Factors that might have contributed to Mass Arthropods and tetrapods are the most widespread Extinctions and diverse land animals. #1: Intense volcanism in what is now Siberia. Tetrapods evolved from lobe-finned fishes around Global warming and ocean acidification 365 million years ago. result from large amounts of CO2 emission from the volcanoes. MESOZOIC ERA #2: Anoxic conditions resulting from nutrient (251 - 65.5 Million Years Ago) enrichment of ecosystems. Coral reefs emerged, becoming important marine ecological niches for other organisms. #3: The presence of iridium in sedimentary rocks suggests that a meteorite impacted 65 million years ago. 4  Clouds caused by the impact would have Bilateral Symmetry: Two-sided symmetry is called blocked sunlight and disturbed the global bilateral symmetry. Bilateral animals often move climate. actively and have a central nervous system. Is a Sixth Mass Extinction Under Way? TISSUES Animal body plans also vary according to the Scientists estimate that the current rate of extinction organization of the animal’s tissues. is 100 to 1,000 times the typical background rate. Tissues: These are collections of specialized cells Extinction rates tend to increase when global isolated from other tissues by membranous layers. temperatures increase. During development, three germ layers give rise to Data suggest that a sixth, human-caused mass the tissues and organs of the animal embryo. extinction is likely to occur unless dramatic action is taken. Ectoderm: The germ layer covering the embryo’s surface. MODULE 5.2: THE ANIMAL FORM Endoderm: The innermost germ layer and lines Animals can be characterized by “Body Plans” the developing digestive tube, called the archenteron. Body Plan: A set of morphological and developmental traits. Sponges and a few other groups lack true tissues. Some body plans have been conserved, while Diploblastic Animals: These animals have an others have changed multiple times over the ectoderm and endoderm (cnidarians and a few course of evolution. (See Hox Genes) other groups. Triploblastic Animals: Aside from the endoderm and SYMMETRY ectoderm, these animals have an intervening Animals can be categorized according to the mesoderm layer (bilaterians). symmetry of their bodies, or lack of it. These include flatworms, arthropods, vertebrates [chordates], and others. Radial Symmetry: Some animals have radial symmetry, with no front and back, nor left and right. BODY CAVITIES Bilaterally symmetrical animals have: Coelomates: Animals that possess a true coelom. A dorsal (top) side and a ventral (bottom) True body cavity is called a coelom and is side derived from the mesoderm. A right and left side Anterior (front) and posterior (back) end Pseudocoelomates: Triploblastic animals that Many have sensory equipment, such as a possess a pseudocoelom. brain, concentrated in their anterior end Pseudocoelom: A body cavity derived from the mesoderm and endoderm. Radial Animals are often sessile or planktonic (drifting or weakly swimming). Acoelomates: Triploblastic animals that lack a body cavity. 5  #3: Eumetazoa (“true animals”) is a clade of animals with true tissues. #4: Most animal phyla belong to clade Bilateria. PROTOSTOME AND DEUTEROSTOME DEVELOPMENT #5: There are three major clades of bilaterian They differ based on the early development of the animals, all of which are invertebrates, except animal. Chordata, which are classified as vertebrates. Indeterminate Cleavage: Each cell in the early stages of cleavage retains the capacity to develop into a complete embryo. Makes possible identical twins, and embryonic stem cells. The bilaterians are divided into three clades. Coelom Formation: If only mesoderm is involved, then it’s protosome. If both mesoderm and the Deuterostomia: Includes hemichordates (acorn archenteron, then it’s deuterostome. worms), echinoderms (sea stars and relatives, and chordates. Also includes vertebrates and Fate of the Blastophore: The Blastophore forms invertebrates. during the gastrulation and connects the archenteron to the exterior of the gastrula. Ecdysozoa: A clade of invertebrates that shed their exoskeletons through a process called ecdysis. THE DIVERSIFICATION OF ANIMALS Zoologists recognize about three dozen animal Lophotrochozoa: Have a feeding structure called a phyla. Phylogenies now combine morphological, lophophore. Others go through a distinct molecular, and fossil data. developmental stage called the trochophore larva. Five important points about the relationships among living animals are reflected in their phylogeny #1: All animals share a common ancestor. #2: Sponges are basal animals. (Parazoa) 6 Invertebrates are animals that lack a backbone. DEUTEROSTOMIA EXAMPLES Phylum Description They account for more than 95% of known animal species. They are also morphologically diverse and Echinodermata Coelomates with bilaterally occupy almost every habitat on Earth. (sea stars, sea symmetrical larvae and five-part urchins) body organizations as adults Unique water vascular system Has an endoskeleton. Chordata Coelomates with notochord; dorsal, (lancelets, hollow nerve cord tunicates, vertebrates) Has pharyngeal slits; post-anal tail LOPHOTROCHOZOA EXAMPLES Phylum Description Chordates (phylum Chordata) have a notochord Platyhelminthes Dorsoventrally flattened and a dorsal, hollow nerve cord. (flatworms) acoelomates These are bilaterian animals that belong to the Gastrovascular cavity or no digestive clade Deuterostomia. Chordates also comprise all tract. vertebrates and two groups of invertebrates, the urochordates and cephalochordates. Rotifera Pseudocoelomates with alimentary (rotifers) canal (digestive tube with mouth an anus) CHORDATES All chordates share a set of derived characters. Jaws (trophi) and a head with Some species have some of these traits only during ciliated crown embryonic development. Lophophorates; Coelomates with lophophores There are four key characters of chordates. Ectoprocta, (feeding structures bearing ciliated Brachiopoda tentacles) Notochord: It is a longitudinal, flexible rod between Mollusca Coelomates with 3 main body parts the digestive tube and nerve cord. It provides (clams, snails, (muscular foot, visceral mass, skeletal support throughout most of the length of a squids) mantle) and coelom reduced chordate. Most have a hard shell made of Dorsal, Hollow Nerve Cord: The nerve cord of a calcium carbonate chordate embryo develops from a plate of Annelida Coelomates with segmented body ectoderm that rolls into a tube dorsal to the (segmented wall and internal organs (except notochord. worms) digestive tract) The nerve cord develops into the central nervous system: the brain and the spinal cord. Pharyngeal Slits or Clefts: These are grooves in the pharynx that are called pharyngeal clefts. These 7 develop into slits that open to the outside of the Size and shape affect the way an animal interacts body. with its environment. The body plan of an animal is programmed by the genome, itself the product of They have the following functions: millions of years of evolution. Suspension-feeding structures in many invertebrate chordates Gas exchange in vertebrates (except EVOLUTION OF ANIMAL SIZE AND SHAPE vertebrates with limbs, the tetrapods) Physical laws govern strength, diffusion, movement, Develop into parts of the ear, head, and and heat exchange. neck in tetrapods. Properties of water limit possible shapes for fast Muscular, Post-Anal Tail: Chordates have a tail swimming animals. posterior to the anus. In many species, the tail is greatly reduced during embryonic development As animals increase in size, thicker skeletons are (ex: urochordates - during larval stage). required for support. The tail contains skeletal elements and muscles. It Convergent Evolution: results in similar adaptations also provides propelling force in many aquatic of diverse organisms facing the same challenge. species. In the ocean, fast swimmers have a streamlined fusiform shape. EXCHANGE WITH THE ENVIRONMENT Nutrients, Waste Products, and Gases: It must be exchanged across the cell membranes of animal cells. Rate of exchange: Should be proportional to a cell's surface area while amount of exchange material is proportional to a cell's volume. Single-celled organism living in water has sufficient surface area to carry out all necessary exchange. Multicellular organisms with a saclike body plan have body walls that are only two cells thick, facilitating diffusion of materials. MODULE 6: THE MULTICELLULAR ANIMAL BODY Interstitial Fluid: In flat animals (e.g. tapeworms), Animal form and function are correlated at all most cells are in direct contact with its environment levels of organization. = the interstitial fluid of other animals. Anatomy: It is the biological form of an organism. Evolutionary adaptations of more complex organisms enable sufficient exchange with the Physiology: It is the biological functions an organism environment. performs. 8 In vertebrates, the space between cells is filled with pseudostratified (a single layer of cells of interstitial fluid, which allows for the movement of varying length). material into and out of cells. The Polarity of Epithelia HIERARCHICAL ORGANIZATION OF BODY PLANS Most animals are composed of specialized cells Polarity: It means two different faces. The organized into tissues that have different functions. Epithelial has two surfaces: Apical surface (outer) and Basal surface. Tissues make up organs, which together make up organ systems. Connective Tissue: It mainly binds and supports other tissues. It contains sparsely packed cells Some organs, such as the pancreas, belong to scattered throughout an extracellular matrix. The more than one system. matrix consists of fibers in a liquid, jellylike, or solid foundation. Three Types of Connective Tissue Fiber All of these are made of protein. Collagenous Fibers: It provides strength and flexibility. Reticular Fibers: It joins connective tissue to adjacent tissues. Elastic Fibers: It stretches and snaps back to their original length, The connective tissue also contains cells, including: Fibroblasts: These secrete the protein of EXPLORING STRUCTURE AND FUNCTION IN ANIMAL extracellular fibers. TISSUES Macrophages: These are involved in the Different tissues have different structures that are immune system. suited to their functions. Six Major Types of Connective Tissue Tissues are classified into four main categories: Epithelial, Connective, Muscle, and Nervous. Loose Connective Tissue: It binds epithelia to underlying tissues and holds organs in place. Epithelial Tissue: It covers the outside of the body and lines the organs and cavities within the body. It Fibrous Connective Tissue: It is found in tendons is a barrier against mechanical injury, pathogen (attach muscles to bones) and ligaments and fluid loss [tight junction]. (connects bones at joints). Shape: Be cuboidal (like dice), columnar (like Bone: It is mineralized and forms the skeleton. bricks on end), or squamous (like floor tiles). Bone cells are called Osteocytes. Arrangement: May be simple (single cell layer), Adipose Tissue: It stores fat for insulation and stratified (multiple tiers of cells), or fuel. Its cells are called adipocytes. 9  Blood: Blood cells and cell fragments in blood plasma. COORDINATION AND CONTROL It is in response to stimuli. It depends on the Cartilage: It is a strong and flexible support endocrine system and the nervous system. material. Its cells are called chondrocytes. Endocrine System: It transmits chemical signals Muscle Tissue: It is responsible for nearly all types of called hormones to receptive cells throughout the body movement. Muscle cells consist of filaments of body via blood. the proteins actin and myosin, which together enable muscles to contract. A hormone may affect one or more regions throughout the body [depending on cells that have Divided in the vertebrate body into three types: receptors for it]. Skeletal Muscle (Striated Muscle): It is Hormones are relatively slow acting, but can have responsible for voluntary movement. long-lasting effects. Smooth Muscle: It is responsible for involuntary Nervous System: It transmits information between body activities. specific locations via the axons. Cardiac Muscle: It is responsible for contraction The information conveyed depends on a signal’s of the heart. pathway, not the type of signal. Nerve signal transmission is very fast. Nervous Tissue: It functions in the receipt, processing, and transmission of information. It contains: Neurons, or nerve cells, that transmit nerve impulses Glial cells, or glia (support cells) The Chemical Factor Animals may regulate some environmental variables while conforming to others. Regulator: It uses internal control mechanisms to control internal change in the face of external fluctuation. Conformer: It allows internal conditions to vary with certain external changes. 10  Circadian Rhythm: In animals and plants, it governs physiological changes that occur roughly every 24 hours. Metabolic activities undergo daily cycles in response to the circadian clock. Acclimatization: A process by which homeostasis HOMEOSTASIS can adjust to changes in the external environment. Used to maintain a “steady state” or internal balance regardless of external environment. Birds and mammals can vary their insulation to acclimatize to seasonal temperature changes. In humans, body temperature, blood pH, and glucose concentration are each maintained at a When temperatures are subzero, some ectotherms constant level. produce “antifreeze” compounds to prevent ice formation in their cells. Mechanisms of Homeostasis It controls changes in the internal environment. Homeostatic processes for thermoregulation involve Fluctuations above or below a set point serve as a form, function, and behavior stimulus; these are detected by a sensor and trigger a response. Thermoregulation: It is the process by which animals maintain an internal temperature within a tolerable The response returns the variable to the set point. range. Feedback Control in Homeostasis Endothermic: Animals can generate heat by metabolism; birds and mammals are endotherms. Negative Feedback: Homeostasis in animals relies largely on negative feedback, which Ectothermic: Animals gain heat from external helps to return a variable to a normal range. sources; ectotherms include most invertebrates, fishes, amphibians, and nonavian reptiles. Positive Feedback: It amplifies a stimulus and does not usually contribute to homeostasis in Variation in Body Temperature animals. Poikilotherm: The body temperature of a poikilotherm varies with its environment. Homeotherm: The body temperature of a homeotherm is relatively constant. Alterations in Homeostasis The relationship between heat source and body Set points and normal ranges can change with age temperature is not fixed (that is, not all poikilotherms or show cyclic variation. are ectotherms). 11  Ectothermic marine fishes and invertebrates Behavioral Responses: Both endotherms and inhabit waters with such stable ectotherms use behavioral responses to control temperatures. body temperature. Bats drop from 40°C to a few degrees above zero when they enter hibernation. Some terrestrial invertebrates have postures that minimize or maximize absorption of solar heat. Balancing Heat Loss and Gain Organisms exchange heat by four physical Honeybees huddle together during cold weather to processes: radiation, evaporation, convection, and retain heat. conduction. Adjusting Metabolic Heat Production: HEAT REGULATION IN MAMMALS Thermogenesis is the adjustment of metabolic heat It often involves the integumentary system (skin, production to maintain body temperature. hair, and nails). Thermogenesis is increased by muscle activity such Five adaptations help animals thermoregulate: as moving or shivering. insulation, circulatory adaptations, cooling by evaporative heat loss, behavioral responses, and Physiological Thermostats adjusting metabolic heat production. Thermoregulation in mammals is controlled by a region of the brain called the hypothalamus. Insulation: A major thermoregulatory adaptation in mammals and birds. Skin, feathers, fur, and blubber The hypothalamus triggers heat loss or heat heat flow between an animal and its environment. generating mechanisms. Some ectothermic organisms seek warmer environments to increase Circulatory Adaptations: Many endotherms and their body temperature in response to certain some ectotherms can alter the amount of blood infections. flowing between the body core and the skin (vasodilation and vasoconstriction). The arrangement of blood vessels in many marine mammals and birds allows for countercurrent exchange. They transfer heat between fluids flowing in opposite directions and thereby reduce heat loss. Cooling by Evaporative Heat Loss: Many types of animals lose heat through evaporation of water from their skin. Sweating or Bathing: It moistens the skin, helping to cool an animal down. Energy Allocation and Use Organisms can be classified by how they obtain Panting: It increases the cooling effect in birds chemical energy. and many mammals. Autotrophs: Harness light energy to build energy-rich molecules (ex: plants). 12 Heterotrophs: Harvest chemical energy from food (ex: animals). QUANTIFYING ENERGY USE Metabolic Rate: It is the amount of energy an animal uses in a unit of time. Activity and Metabolic Rate It can be determined by: Activity greatly affects metabolic rate for An animal’s heat loss endotherms and ectotherms. The amount of oxygen consumed or carbon dioxide produced In general, the maximum metabolic rate an animal Measuring energy content of food can sustain is inversely related to the duration of the consumed and energy lost in waste activity. products. For most terrestrial animals, the average daily rate Metabolic Rate and Thermoregulation of energy consumption is 2-4 times BMR (endotherms) or SMR (ectotherms). Basal Metabolic Rate (BMR): Metabolic rate of an endotherm at rest at a “comfortable” The fraction of an animal’s energy budget devoted temperature. to activity depends on several factors: environment, behavior, size, and thermoregulation. Standard Metabolic Rate (SMR): Metabolic rate of an ectotherm at rest at a specific temperature. MODULE 7.1: THE INTEGUMENTARY SYSTEM INFLUENCES ON METABOLIC RATE THE SKIN Ectotherms have much lower metabolic rates than It consists of the cutaneous membrane and its endotherms of a comparable size. accessory organs and comprises three layers of tissue. Other key factors: age, sex, size, activity, temperature, and nutrition. Outer Epidermis: Made of stratified squamous epithelium Size and Metabolic Rate Metabolic rate is proportional to body mass to the Middle Dermis: Made of fibrous connective tissue power of three quarters (m3/4). Hypodermis: It is also known as the inner Smaller animals have higher metabolic rates per subcutaneous layer. gram than larger animals. The skin also contains several accessory organs, Higher metabolic rate ⇒ leads to a higher oxygen which include the hair (hair root and hair shaft), hair delivery rate, breathing rate, heart rate, and follicle, pili arrector muscle, sebaceous gland, greater (relative) blood volume. sudoriferous gland (sweat gland), nails, and the mammary gland. 13  FUNCTIONS OF THE INTEGUMENTARY SYSTEM which provides a smaller surface area in the blood vessels, resulting in less heat loss. Protection: There are three factors, which include the chemical, physical, and biological factors in the Vasodilatation By Arterioles: Vasodilatation in skin. the dermis layer provides a larger surface area in the blood vessels, resulting in greater heat The Chemical Factors loss. Sebum (or oil): From the sebaceous glands is Cutaneous Sensation: These are any of the senses slightly acidic, retarding bacterial colonization that are dependent on receptors in the skin on the skin surface. sensitive to contact, pressure, vibration, temperature, or pain. Sweat from Sudoriferous Glands: It is slightly hypertonic and can flush off most bacteria on Nerve Receptors: These are found in the dermis the skin's surface. layers and detect sensations such as heat, cold, pain, pressure, and touch, allowing the body to Melanin (skin pigment): From melanocytes, be aware of these stimuli. avoid excessive ultraviolet radiation that penetrates the skin layers. Vitamin D Synthesis: The epidermal layer of human skin synthesizes vitamin D when exposed to UV The Physical Factors radiation. In the presence of sunlight, a form of vitamin D3 called cholecalciferol is synthesized from Stratified squamous epithelium: It is found in the a derivative of the steroid cholesterol in the skin. epidermis layer and provides many layers of cells, preventing most bacterial invasion. Ultraviolet Radiation: It results in Vitamin D through a series of chemical reactions Keratinized Cells: It is found in the stratum activated by sunlight. This is due to a chemical corneum layer of the epidermis and provides a modification of cholesterol to absorb calcium. physical barrier against most invasions. EPIDERMIS: CHARACTERISTICS The Biological Factor It is made of stratified squamous epithelium. It has no blood vessels to supply nutrients to its cells. The White Blood Cells: Macrophages destroy most epidermis surface of the body has four layer of cells: invaded bacteria and other foreign substances. stratum basale, stratum spinosum, stratum granulosum, and stratum corneum. Excretion: Waste materials such as ammonia, urea, and excessive salt are eliminated from sweating. Nutrients from the arterioles in the dermis layer diffuse upward into the epidermis layer, especially Body Temperature Regulation: There are three: to the stratum basale and spinosum layers. sweating, vasoconstriction, and vasodilation. Sweating: This is done by the sweat glands and it promotes evaporation, resulting in a loss of excessive body heat. Vasoconstriction By Arterioles: Vasoconstriction is done by small arteries in the dermis layer, 14  The number of melanocytes and the amount of Stratum Basale (or Stratum Germinativum): The layer melanin production are genetically inherited. It also receives most of the nourishment. protects the DNA in the nuclei of cells. Cuboidal cells Reproduce rapidly using mitosis DERMIS: CHARACTERISTICS New cells will be pushed upward and It is made of fibrous connective tissue. It also become flattened as they move upward contains arterioles for supplying nutrients to its structures and to the epidermis. Squamous cells moving upward in the epidermis receive less and less nutrients as diffusion distance increases. Stratum Corneum: By the time these squamous cells form the stratum corneum, the cells are dead and will be shed off. Keratinization: Cells in the stratum granulosum and stratum corneum undergo this process. Produces a protein called keratin This allows cells to be tough and waterproof. These cells are now called “keratinocytes.” These develop desmosomes between the cells and allow the epidermis to become a stronger Pili Arrector Muscles: It wrinkles the skin and erects physical barrier. the hairs. THICK SKIN VS THIN SKIN Hair Follicles: These are what develop into hair. Stratum Lucidum: It is only found in the palms and Nerves and Nerve Receptors: These detect the soles, It is an extra thin layer beneath the stratum sensations of heat, cold, pressure, touch, and pain. corneum is formed. Sebaceous Gland: These secrete sebum onto skin Thick skin has all 5 layers. It is found in areas where surface (acidic environment). there is a lot of abrasion. It is normally found in the fingertips, palms, and the soles of feet. Sudoriferous Glands: These secrete sweat (hypertonic environment). Thin skin only has 4 layers. It is thin due to the stratum lucidum being absent. HYPODERMIS: CHARACTERISTICS It is made of adipose tissue and loose connective EPIDERMIS: SPECIALIZED CELLS tissue. The collagen and elastic fibers in the loose connective tissue are continuous with the fibers in Melanocytes: Specialized cells in the stratum basale the dermis layer. layer that produce the skin pigment, melanin. Adipose Tissue: These act as a heat insulator against the cold climate and as fat storage. 15 Loose Connective Tissue: These allow the skin to be Sebaceous Gland: It is an oil gland made of bound with underlying muscles. modified cuboidal epithelium. It occurs all over the body except in the palm and sole. The hypodermis also contains large blood vessels (arteries and veins). It is attached to each hair follicle so that sebum can be secreted into the hair root and diffuse ACCESSORY STRUCTURES OF THE SKIN upward. Hair: It is produced by epithelial cells at the hair Sebum: It helps the skin and hair to be papilla. It is made of keratinized cells. It also consists waterproof and retards bacterial growth on skin of two regions: surface (due to its acidity). Hair Root: Located in the hair follicle and it is Sudoriferous Gland: It is the sweat gland that embedded in the dermis layer. secretes sweat to promote evaporation. It is found all over the body except the lips, nipples, and Hair Shaft: Protruded through the epidermis to external genitalia. the outside It is also referred to as “tubular gland” where a long Hair pigment or melanin is produced by tubule coiled in the dermis layer, uses a long duct melanocytes in the hair papilla. Hair growth is to release sweat onto skin surface through a pore. affected by nutrition and hormones. (i.e. testosterone). Nails: It is a scale-like modification of epithelial cells in the epidermis. It is made of keratin. The Hair Cycle The nails protect the ends of fingers and toe and Anagen Phase: Lasts around 2-6 years. This is prevent over sensitization of the nerve receptors in where active growth and the production of extremities. Growing cells are derived from the base new cells occur. of the nail or lunula. Catagen Phase: Lasts around 2-4 weeks. This is BURNS where growth stops due to the hair papilla detaching from the hair follicle. 1st Degree Burns: Only the epidermis is damaged with redness and swelling. Telogen Phase: Lasts around 3-5 months. This is where the follicle rests and prepares for the next 2nd Degree Burns: The epidermis and upper region cycle of growth. Also called “resting” or of dermis is involved. There is redness, swelling, and “shedding.” blisters. Pili Arrector Muscle: It is made of skeletal muscle but 3rd Degree Burns: All layers of skin are burned. A skin under involuntary control. It is attached to each graft is necessary to repair. The skin would look hair follicle, for erecting the hair. cherry red or blackened. Situations such as extreme emotions or extreme SKIN CANCER temperatures can activate its involuntary Most skin tumors are benign. The cause of cancer is contraction. unknown but is probably due to overexposure to ultraviolet radiation in the sunlight. 16 Basal Cell Carcinoma: It is the most common type and is usually benign. The cells of stratum basale The “head” of a myosin molecule binds to an actin are affected, as a result they cannot form keratin filament, forming a cross-bridge and pulling the thin and begin to invade into the dermis. Surgical filament toward the center of the sarcomere. removal (in early detection) is 99% successful. Glycolysis & Aerobic Respiration: These generate Squamous Cell Carcinoma: It arises from the ATP needed to sustain muscle contractions. keratinocytes in stratum spinosum. It is mostly detected in the scalp, ears, or hands. It grows and migrates rapidly. Early detection is critical for successful treatment. Malignant Melanoma: It is the most dangerous and it is the cancer of the melanocytes in the stratum basale. It is only 5% of all skin cancer but the frequency is increasing. It grows and migrates extremely rapidly. Usually deadly. MODULE 7.2: THE MUSCULOSKELETAL SYSTEM VERTEBRATE SKELETAL MUSCLE The Role of Calcium and Regulatory Proteins It is also called striated muscle because of the light and dark bands. Tropomyosin & Troponin Complex: These bind to actin strands on thin filaments when a muscle fiber It moves the bones and the body, as well as it is a is at rest. This prevents actin and myosin from bundle of long fibers running parallel to the length interacting. of the muscle. For a muscle fiber to contract, myosin-binding sites Sarcomere: It is the functional unit of the muscle. It is must be uncovered. bordered by Z lines and is made up of myofibrils. This occurs when calcium ions (Ca2+) bind to the troponin complex and expose the myosin-binding sites. Nervous Control of Muscle In vertebrates, each motor neuron may synapse with multiple muscle fibers. The Sliding-Filament Model of Muscle Contraction Thin & Thick Filaments: Thin (actin) and thick (myosin) filaments slide past each other longitudinally. 17 Motor Unit: It consists of a single motor neuron and TYPES OF SKELETAL MUSCLE FIBERS all the muscle fibers it controls. It is classified by the source of ATP powering the muscle activity or by the speed of muscle Action Potential: This is produced by a motor contraction. unit and it results in all muscle fibers within the motor unit to contract. Nervous Control of Muscle Tension Contraction of a whole muscle is graded, which means that the extent and strength of its contraction can be voluntarily altered. There are two basic mechanisms by which the nervous system produces graded contractions. No. of Contracted Fibers: Varying the number of fibers that contract Stimulant: Varying the rate at which fibers are stimulated. Recruitment: The recruitment of multiple motor neurons results in stronger contractions. Twitch: It results from a single action potential in a motor neuron. Summation: The term for more rapid delivery of In terms of source of ATP action potentials that produce a graded contraction by summation. Oxidative Fibers: It relies mostly on aerobic respiration to generate ATP. It has many Tetanus: It is a state of smooth and sustained mitochondria, a rich blood supply, and a large contraction produced when motor neurons deliver amount of myoglobin. a volley of action potentials. Myoglobin: This is a protein that binds oxygen more tightly than hemoglobin does. Glycolytic Fibers: It uses glycolysis as their primary source of ATP. It has less myoglobin than oxidative fibers and tire more easily. In poultry and fish, light meat is composed of glycolytic fibers, while dark meat is composed of oxidative fibers. In terms of speed of muscle contraction Most skeletal muscles contain both slow-twitch and fast-twitch fibers in varying ratios. 18 Slow-twitch Fibers: It contracts more slowly but rhythmic waves of muscle contractions from sustains longer contractions. All are oxidative fibers. front to back. Fast-twitch Fibers: It contracts more rapidly but Exoskeletons: A hard encasement deposited on the sustains shorter contractions. It can be either surface of an animal. It is found in most molluscs glycolytic or oxidative. and arthropods. In producing its characteristic mating call, the male Arthropods: They have a jointed exoskeleton toadfish can contract and relax certain muscles called a cuticle, which can be both strong and more than 200 times per second. flexible. The polysaccharide chitin is often found OTHER TYPES OF MUSCLES in arthropod cuticles. Cardiac Muscle: It is found only in the heart, consists Endoskeletons: It consists of a hard internal skeleton, of striated cells electrically connected by buried in soft tissue. It is found in organisms ranging intercalated disks. It can generate action potentials from sponges to mammals. without neural input. A mammalian skeleton has more than 200 bones. Smooth Muscle: It is found mainly in walls of hollow Some bones are connected at joints by ligaments organs such as those of the digestive tract. Its that allow freedom of movement. contractions are relatively slow and may be initiated by the muscles themselves. The contractions may also be caused by stimulation from neurons in the autonomic nervous system. Skeletal systems transform muscle contraction into locomotion TYPES OF LOCOMOTION Most animals are capable of locomotion, or active Skeletal Muscles: These are attached in travel from place to place. In locomotion, energy is antagonistic pairs, the actions of which are expended to overcome friction and gravity. It is coordinated by the nervous system. classified by the location at which it occurs. The skeleton provides a rigid structure to which Locomotion on Land: Walking, running, hopping, or muscles attach. crawling on land requires an animal to support itself and move against gravity. TYPES OF SKELETAL SYSTEMS It is composed of hydrostatic skeletons (lack hard Diverse adaptations for locomotion on land have parts), exoskeletons (external hard parts), and evolved in vertebrates. The air poses relatively little endoskeletons (internal hard parts). resistance. Hydrostatic Skeletons: These consist of fluid held Maintaining balance is a prerequisite for walking, under pressure in a closed body compartment. It is running, or hopping. Crawling animals must exert the main type of skeleton in most cnidarians, energy to overcome friction. flatworms, nematodes, and annelids. Swimming: Friction is a bigger problem than gravity Peristalsis: Annelids use their hydrostatic skeleton underwater. Fast swimmers usually have a sleek, for peristalsis, a type of movement produced by torpedo-like shape to minimize friction. 19 Animals swim in diverse ways: Paddling with their legs as oars Jet propulsion Undulating their body and tail from side-to-side or up and down Flying: Active flight requires that wings develop enough lift to overcome the downward force of Essential Amino Acids: Animals require 20 amino gravity. acids. These must be obtained from food preassembled. Many flying animals have adaptations that reduce body mass. Meat, eggs, and cheese provide all the essential Birds have no urinary bladder or teeth and amino acids and are thus “complete” proteins. have relatively large bones with air-filled regions. Most plant proteins are incomplete in amino acid content. Individuals who eat only plant proteins need MODULE 8.1: THE DIGESTIVE SYSTEM to eat specific plant combinations to get all essential amino acids. NUTRITION Process: food is taken in, taken apart, and taken up Essential Fatty Acids: It must be obtained from the in the process of animals. diet and include certain unsaturated fatty acids. In general, animals fall into three categories: Animals can synthesize most fatty acids needed Herbivores: eat plants and algae (although deficiencies in fatty acids are rare). Carnivores: eat other animals Omnivores: consume animals, plants, or These synthesize phospholipids, signal molecules, algae and fat storage. An animal’s diet must provide: Vitamins: These are organic molecules required in Chemical energy for cellular processes the diet in very small amounts. There are 13 vitamins Organic building blocks for macromolecules essential for humans. There are also two categories: Essential nutrients fat-soluble vitamins and water-soluble vitamins. ESSENTIAL NUTRIENTS Materials that an animal cannot assemble from simpler organic molecules. It must be obtained from an animal’s diet. It is involved in biosynthesis reactions (conversion of energy from food). There are 4 classes: essential amino acids, essential fatty acids, vitamins, and minerals. Minerals: These are simple inorganic nutrients, usually required in small amounts. Ingesting large amounts of some minerals can upset the homeostatic balance. 20  Absorption: It is the uptake of nutrients by body cells. Elimination: It is the passage of undigested material out of the digestive system. STRATEGIES FOR EXTRACTING RESOURCES Suspension Feeders: It is seen in many aquatic DIETARY DEFICIENCIES animals and sifts small food particles in water. Malnutrition: It is a failure to obtain adequate Substrate Feeders: These are animals that live in or nutrition. It can have negative impacts on health on their food source. and survival. Fluid Feeders: These suck nutrient-rich fluid from a Deficiencies in essential nutrients: It is can cause living host. deformities, disease, and death. Bulk Feeders: These eat relatively large pieces of Phosphorus deficiency in cattle, deer, and other food. herbivores can be prevented by consuming concentrated sources of salt or other minerals. THE DIGESTIVE PROCESS Golden Rice is an engineered strain of rice with Intracellular Digestion: The food particles are beta-carotene, which is converted into Vitamin A in engulfed by phagocytosis. Food vacuoles, the body. containing food, fuse with lysosomes containing hydrolytic enzymes. (Ex: sponges) STAGES OF FOOD PROCESSING Extracellular Digestion: It is the breakdown of food particles outside of cells. It occurs in compartments that are continuous with the outside of the animal’s body. (Ex: grasshopper, birds) Ingestion: It is the act of eating or feeding. Gastrovascular Cavity: These are seen in Digestion: It is the process of breaking food down animals with simple body plans. It functions in into molecules smaller enough to be absorbed. both digestion and distribution of nutrients. 21  Alimentary Canal: It is a digestive tube with two Swallowing: It causes the epiglottis to block openings (mouth and anus). It is seen in more entry to the trachea. complex animals. It signals a complete digestive tract. Coughing: This occurs when the swallowing reflex fails and food or liquids reach the THE MAMMALIAN DIGESTIVE SYSTEM trachea. It consists of an alimentary canal and accessory Digestion in the Stomach glands that secrete digestive juices through ducts. It stores food and begins digestion of proteins. The The Mammalian accessory glands include: salivary stomach secretes gastric juice, which converts a glands, pancreas, liver, and gallbladder. meal to chyme. Food is pushed along by peristalsis, rhythmic Sphincters prevent chyme from entering the contractions of muscles in the wall of the canal. esophagus and regulate its entry into the small intestine. Sphincters: These are valves that regulate the movement of material between compartments. Gastroesophageal Reflux Disease (GERD): This happens when gastric juices from the stomach flows back to the esophagus. This is caused by weak sphincter muscles at the esophagus or relaxation at the wrong time. CHEMICAL DIGESTION IN THE STOMACH Oral Cavity: This is where the first stage of digestion takes place. Salivary Glands: These deliver saliva to lubricate food. Teeth: These chew food into smaller particles. Tongue: This shapes food into a bolus and helps with swallowing. Throat/Pharynx: This is the junction that opens to Gastric Juice: It has a low pH of about 2, which kills both the esophagus and the trachea. bacteria and denatures proteins. It is made up of hydrochloric acid (HCI) and pepsin. Esophagus: This conducts food from the pharynx down to the stomach by peristalsis. Pepsin: It cleaves proteins into smaller peptides. Trachea: This leads to the lungs. Parietal Cells: These cells secrete hydrogen and chloride ions separately into the cavity of the stomach. 22  In Absorption Chief Cells: These cells secrete inactive pepsinogen, which is activated to pepsin when Villi & Microvilli: It increases the small intestine’s mixed with HCI in the stomach. surface area. It creates a brush border that greatly increases the rate of nutrient absorption. Mucus: This lubricates and protects the stomach Transport across the epithelial cells can be passive lining from gastric juice. or active depending on the nutrient. Chemical Digestion in the Stomach: Positive THE LARGE INTESTINE Feedback In Processing The Cecum: It aids in the fermentation of plant material. It connects where the small intestine and large intestine meet. The human cecum has an extension called the appendix, which plays a minor role in immunity. The Colon: This completes the reabsorption of water that began in the small intestine. Feces: This includes undigested material and bacteria, it becomes more solid as they move through the colon. It is stored in the rectum until elimination through the anus. THE SMALL INTESTINE In Digestion Two sphincters between the rectum and anus control bowel movements Small Intestine: It is the longest compartment of the alimentary canal. Most enzymatic hydrolysis of macromolecules from food occurs in this. Evolutionary adaptations of vertebrate digestive systems correlate with diet Duodenum: This is the first portion of the small intestine. It is where chyme from the stomach mixes The digestive systems of vertebrates are variations with digestive juices from the pancreas, liver, on a common plan. However, there are intriguing gallbladder, and the small intestine. adaptations, often related to diet. Pancreas: It produces proteases trypsin and Dental Adaptations chymotrypsin that are activated in the lumen of the duodenum to neutralize the acidic chyme. Dentition: It is an animal’s assortment of teeth. The success of mammals is due in part to their dentition, Gallbladder: This stores bile that is made in the liver. which is specialized for different diets. The bile aids in digestion and absorption of fats. Nonmammalian vertebrates have less specialized teeth, although exceptions exist. (Ex: Snakes) Stomach & Intestinal Adaptations 23 Many carnivores have large, expandable stomachs. Herbivores and omnivores generally Liver: It is the site for glucose homeostasis. have longer alimentary canal than carnivores, reflecting the longer time needed to digest vegetation. Mutualistic Adaptations The coexistence of humans and many bacteria involves mutualistic symbiosis. Some intestinal bacteria produce vitamins and can also regulate the development of the intestinal epithelium and the function of the innate immune system. Many herbivores have fermentation chambers, where mutualistic microorganisms digest cellulose. REGULATION OF APPETITE AND CONSUMPTION Ruminants: Animals that have the most elaborate adaptations for an herbivorous Hormones: It regulates long-term and short-term diet. appetite by affecting a “safety center” in the brain. Ghrelin: It is a hormone secreted by the REGULATION OF DIGESTION stomach wall, triggers feelings of hunger before meals. Each step in the digestive system is activated as needed. Insulin & PYY: These are hormones secreted by the small intestine after meals, both suppress The enteric division of the nervous system helps to appetite. regulate the digestive process. Leptin: This is produced by adipose (fat) tissue. It The endocrine system also regulates digestion suppresses appetite and plays a role in through the release and transport of hormones. regulating body fat levels. Summary: Mammalian Digestive Organs GLUCOSE HOMEOSTASIS Glucose: It is a major fuel for cellular respiration. It is a key source of carbon skeletons for biosynthesis. Insulin & Glucagon: These are hormones that regulate the breakdown of glycogen into glucose. 24 MODULE 8.2: THE RESPIRATORY SYSTEM More than 80% of the O2 dissolved in the water is removed as water passes over the respiratory Gas Exchange: Uptake of O2 for cellular respiration surface. and disposal of CO2 to the environment. Partial Pressure: The pressure exerted by a particular Tracheal Systems in Insects gas in a mixture of gasses. It also applies to gasses dissolved in liquids such as water. It consists of a network of branching tubes throughout the body. Net Diffusion: Gasses undergo this process from a region of higher partial pressure to a region of The respiratory and circulatory systems are lower partial pressure. separate. Larger insects must ventilate their tracheal system to meet O2 demands. Respiratory Media: In a given volume, there is less O2 available in water than in air. Obtaining O2 from Lungs water requires greater efficiency than air breathing. It is the infolding of the body surface. The circulatory Respiratory Surfaces: Animals require large, moist (open or closed) transports gasses between the respiratory surfaces for exchange of gasses lungs and the rest of the body. between their cells and the respiratory medium, either air or water. The size and complexity of lungs correlate with an animal’s metabolic rate. Gas exchange across respiratory surfaces takes place by diffusion. Respiratory surfaces vary by MAMMALIAN RESPIRATORY SYSTEMS animal and can include the skin, gills, tracheae, A system of branching ducts conveys air to the and lungs. lungs. GILLS IN AQUATIC ANIMALS Nostrils: It is where inhaled air is filtered, warmed, It is the outfoldings of the body that create a large humidified, and sampled for odors. surface area for gas exchange. Pharynx: It directs air to the lungs and food to the Ventilation: It moves the respiratory medium over stomach. the respiratory surface. Aquatic animals move through water or move water over their gills for Larynx: Swallowing moves the larynx upward and ventilation. tips the epiglottis over the glottis in the pharynx (closed). Air passes through the pharynx, larynx, trachea, bronchi, and bronchioles to the alveoli, where gas exchange occurs. Vocal Cords in Larynx: This is where exhaled air Fish Gills: It uses a countercurrent exchange system, passes over to create sounds. where blood flows in the opposite direction to water passing over the gills. Cilia & Mucus: These line the epithelium of the air ducts and move particles up to the pharynx. 25 Alveoli: Air sacs at the tips of bronchioles where gas Negative Pressure Breathing: Pulls air into the lungs. exchange takes place. Governed by the diaphragm, rib cage, and rib Oxygen diffuses through the moist film of the muscles. epithelium and into capillaries. Long Volume: It increases as the rib muscles and Carbon dioxide diffuses from the capillaries across diaphragm contract. the epithelium and into the air space. Tidal Volume: The volume of air inhaled and Surfactants: Secretions that coat the surface of exhaled with each breath. the alveoli and prevent the alveoli from collapsing. Preterm babies lack surfactant. Vital Capacity: The maximum tidal volume. Residual Volume: Air that remains in the lungs Breathing: This is the process that ventilates the after exhalation. lungs. It is the alternation of inhalation and exhalation of air. Control of Breathing in Humans How an Amphibian Breathes It is usually regulated by involuntary mechanisms. An amphibian such as a frog ventilates its lungs by Medulla Oblongata of the Brain: It is where positive pressure breathing, which forces air down breathing control centers are found. It regulates the the trachea. rate and depth of breathing in response to pH changes in the cerebrospinal fluid. COORDINATION OF CIRCULATION AND GAS EXCHANGE Blood arriving in the lungs has a low partial pressure of O2 and a high partial pressure of CO2 relative to air in the alveoli. How a Bird Breathes In the alveoli, O2 diffuses into the blood and CO2 Birds have 8 or 9 air sacs. These function as bellows diffuses into the air. that keep air flowing through the lungs. In tissue capillaries, partial pressure gradients favor Air passes through the lungs in one direction only. diffusion of O2 into the interstitial fluids and CO2 into the blood. Passage of air through the entire system of lungs and air sacs requires two cycles of inhalation and RESPIRATORY PIGMENTS exhalation. These are proteins that transport oxygen, greatly increasing the amount of oxygen that blood can Parabronchi: Site of gas exchange. carry. Ventilation in birds is highly efficient. Hemocyanin: Arthropods and many molluscs have these with copper as the oxygen-binding How a Mammal Breathes component. 26  can store oxygen in their muscles in myoglobin Hemoglobin: Most vertebrates and some proteins. invertebrates use hemoglobin. In vertebrates, it is contained within erythrocytes and has iron as the Diving mammals also conserve oxygen by: oxygen binding component. Changing their buoyancy to glide passively Decreasing blood supply to muscles A single hemoglobin molecule can carry four Deriving ATP in muscles from fermentation molecules of O2, one molecule of each once oxygen is depleted. iron-containing heme group. The hemoglobin dissociation curve shows that a small change in the partial pressure of oxygen can result in a large change in delivery of O2. Hemoglobin plays a minor role in transport of CO2 and assists in buffering the blood. Carbon Dioxide Some of CO2 from respiring cells diffuses into the blood and is transported in blood plasma, bound to hemoglobin. The remainder diffuses into erythrocytes and reacts with water to form H2CO3, which dissociates into H+ and bicarbonate ions (HCO3-). In the lungs the relative partial pressures of CO2 favor the net diffusion of CO2 out of the blood. Respiratory Adaptation of Diving Mammals It allows them to perform extraordinary feats. (Ex: Weddell seals in Antarctica can remain underwater for 20 minutes to an hour) These animals have a high blood to body volume ratio. They stockpile O2 and deplete it slowly. They 27