BIOL 240W - Exam One Notes
BIOL 240W - Exam One Notes BIOL240
Popular in Biology: Function and Development of Organisms
verified elite notetaker
verified elite notetaker
verified elite notetaker
verified elite notetaker
verified elite notetaker
verified elite notetaker
Popular in Science
This 37 page Bundle was uploaded by Sabrina Sayoc on Thursday August 4, 2016. The Bundle belongs to BIOL240 at Pennsylvania State University taught by Dr. Waters and Dr. Axtel in Spring 2016. Since its upload, it has received 20 views. For similar materials see Biology: Function and Development of Organisms in Science at Pennsylvania State University.
Reviews for BIOL 240W - Exam One Notes
Report this Material
What is Karma?
Karma is the currency of StudySoup.
You can buy or earn more Karma at anytime and redeem it for class notes, study guides, flashcards, and more!
Date Created: 08/04/16
Chapter 47: Animal Development 47.2 Morphogenesis in animals involves specific changes in cell shape, position, and survival Introduction ● Morphogenesis the cellular and tissuebased process by which the animal body takes shape ● During gastrulation, set of cells at or near surface of the blastula move to interior location, establishing cell layers, and forming primitive digestive tube ● Organogenesis the formation of organs Gastrulation Introduction ● Gastrulation reorganization of hollow blastula into twolayered or threelayered embryo called a gastrula ○ Germ layers cell layers produced ■ Ectoderm forms outer layer ■ Endoderm lines the embryonic digestive compartment or tract ■ Mesoderm forms between ectoderm and endoderm ● Cnidarians and other radially symmetrical animals only have ectoderm and endoderm and are called diploblasts ● Triploblasts have all three germ layers Gastrulation in Sea Urchins ● Gastrulation involves migration and invagination (the infolding of a sheet of cells into the embryo) ○ Extensive rearrangement forms deeper, narrower, blindended tube called archenteron (future digestive tube) ■ Open end will become the anus, called the blastopore, other forms mouth ● Deuterostomes mouth develops from second opening of the embryo ● Protostomes mouth develops from the first opening formed during gastrulation ○ Present in mollusks, annelids, and arthropods Gastrulation in Frogs ● Frogs are deuterostomes ● Frogs and other bilaterally symmetrical animals have a dorsal side and ventral side, a left side and right side, and an anterior end and posterior end ○ Gastrulation begins at dorsal side of blastula, opposite where sperm entered egg ● Each germ layer contributes to a distinct set of structures in vertebrates Ectoderm (outer layer of Mesoderm (middle layer of Endoderm (inner layer of embryo) embryo) embryo) ● Epidermis of skin ● Skeletal and ● Epithelial lining of and its derivatives muscular systems digestive tract and ● Nervous and ● Circulatory and associated organs sensory systems lymphatic systems ● Epithelial lining of ● Pituitary gland, ● Excretory and respiratory, adrenal medulla reproductive excretory, and ● Jaws and teeth systems reproductive tracts ● Germ cells ● Dermis of skin and ducts ● Adrenal cortex ● Thymus, thyroid, and parathyroid glands Gastrulation in Chicks ● Gastrulation starts with embryo consisting of epiblast and hypoblast lying atop a yolk mass ○ All cells that form embryo come from epiblast ○ The hypoblast cells later segregate and form part of the sac that surrounds the yolk ● During gastrulation, epiblast cells move toward midline of blastoderm and detach, forming a thickening called a primitive streak ○ Primitive streak lengthen and narrows; becomes counterpart of blastopore lip Gastrulation in Humans ● 1. End of cleavage, embryo has more than 100 cells arranged around central cavity and has reached uterus → is called blastocyst (mammalian version of blastula) ○ Inner cell mass group of cells at one end of central cavity ● 2. Trophoblast (outer epithelium of blastocyst) initiates embryo implantation ○ Break down endometrium, allowing invasion of blastocyst ○ Inner cell mass forms inner layer of cells called the epiblast and an outer layer called the hypoblast (embryo develops mostly from epiblast) ● 3. Trophoblast continues to expand into endometrium and four new membranes appear ○ Extraembryonic membranes arise from embryo; enclose specialized structures outside the embryo ■ Some remain as ectoderm, others move inward through primitive streak and form mesoderm and endoderm ● 4. End of gastrulation embryonic germ layers have formed (extraembryonic mesoderm and four distinct extraembryonic membranes surround embryo) ○ Cells of invading trophoblast, the epiblast, and adjacent endometrial tissue contribute to form the placenta ○ Placenta immediates the exchange of nutrients, gases, and nitrogenous wastes between developing embryo and mother Developmental Adaptations of Amniotes ● Mammals and birds have four extraembryonic membranes: chorion, allantois, amnion, and yolk sac ○ Appeared because all vertebrate embryos require an aqueous environment for their development (shell eggs of birds and reptiles or uterus of marsupials) ■ Mammals and reptiles are thus called amniotes ● Chorion site of gas exchange ● Amnion fluid physically protects the developing embryo ● Allantois disposes of wastes in the reptilian egg; incorporated into the umbilical cord in mammals where it forms blood vessels that transport oxygen and nutrients from the placenta to the embryo and rids the embryo of carbon dioxide and nitrogenous wastes ● Yolk sac encloses yolk in eggs of reptiles; in mammals, site of early formation of blood cells (later migrates to embryo proper) Organogenesis Neurulation ● Neurulation the early steps in the formation of the brain and spinal cord in vertebrates ○ Begins as cells from the dorsal mesoderm form the notochord (a rod that extends along the dorsal side of the chordate embryo ○ Signaling molecules cause ectoderm above the notochord to form neural plate ■ Occurs through induction (a process in which a group of cells or tissues influences the development of another group through closerange interactions) ○ Neural plate rolls itself into the neural tube, which runs along the anteriorposterior axis of the embryo ■ Neural tube will become brain in the head and the spinal cord along the rest of the body ■ Notochord disappears before birth ● Error in neural tube formation results in spina bifida, which can cause nerve damage resulting in varying degrees of leg paralysis Cell Migration in Organogenesis ● Two sets of cells that develop near neural tube migrate in the body before assuming developmental fate ● Neural crest develops along the borders where neural tube pinches off from ectoderm; form a variety of tissues that include peripheral nerves and parts of the teeth and skull ● Somites migratory cells formed when groups of cells located in strips separate into blocks; play a significant role in organizing the segment structure of the vertebrate body ○ Some dissociate into mesenchyme cells, which can form the muscles associated with the vertebral column and the ribs ● Somites (serially repeating structures) form repeated structures in the adult Organogenesis in Chicks and Insects ● Early organogenesis in chicks is similar to that of frogs, and by the time the chick embryo is 3 days old, rudiments of major organs are readily apparent ● Organogenesis is somewhat different in invertebrates Chapter 42: Circulation and Gas Exchange 42.5 Gas exchange occurs across specialized respiratory surfaces Introduction ● Gas exchange the uptake of molecular O from the environment and discharge of CO to 2 2 the environment Partial Pressure Gradients in Gas Exchange ● Partial pressure the pressure exerted by a particular gas in a mixture of gases ○ A gas always undergoes net diffusion from a region of higher partial pressure to a region of lower partial pressure Respiratory Media ● Conditions for gas exchange depend on whether the respiratory medium (source of O ) is 2 air or water ○ Gas exchange with water is much more demanding Respiratory Surfaces ● Specialization is apparent in the structure of the respiratory surface (the part of an animal’s body where gas exchange occurs), which is always moist ● Movement of O and C2 across2espiratory surfaces occur by diffusion ○ Rate of diffusion is proportional to the surface area which it occurs, and inversely proportional to the square of the distance through which the molecules must move ■ Gas exchange is fast when the area is large and the path is short ■ Respiratory surfaces tend to be large and thin ● In simple animals, every cell in the body is close enough to external environment that gases can diffuse quickly between any cell and environment ○ Skin serves as a respiratory organ ● For most animals, evolutionary solution is a respiratory organ that is extensively folded or branched, such as gills, trachea, and lungs Gills in Aquatic Animals ● Gills outfoldings of the body surface that are suspended in water ● Ventilation movement of the respiratory medium over the respiratory surface; maintains partial pressure gradients of O 2d CO 2 ● Countercurrent exchange the exchange of a substance or heat between two fluids flowing in opposite directions ○ Maximizes efficiency of gas exchange in fish (80% of the O dissolved in the 2 water diffuses into the blood) ○ Also contributes to temperature regulation and the functioning of the mammalian kidney Tracheal Systems in Insects ● Tracheal system a network of air tubes that branch throughout the body Lungs Introduction ● Lungs localized respiratory organs present in organisms with open circulatory systems ○ Infolding of body surfaces, subdivided into numerous pockets ● Circulatory system transports gases between lungs and the rest of the body ● Use of lungs for gas exchange varies ○ Amphibians rely heavily on diffuse across external body surfaces ○ Most reptiles and all mammals depend entirely on lungs for gas exchange Mammalian Respiratory Systems: A Closer Look ● Air enters through the nostrils, then flows through the maze of spaces in nasal cavity ● Nasal cavity leads to pharynx (intersection where paths for air and food cross) ● When food is swallowed, larynx tips epiglottis over glottis (opening of the trachea (windpipe)), allowing food to go down the esophagus to the stomach ● Otherwise, glottis is open, enabling breathing ● Air goes from larynx into the trachea, which branches into two bronchi, one leading to each lung ● Within the lung, bronchi branch into finer tubes called bronchioles ● Gas exchange in mammals occur in the alveoli (air sacs clustered at the tips of the tiniest bronchioles) ○ Alveoli produce surfactant (a mixture of phospholipids and proteins that coat the alveoli and reduce surface tension) 42.6 Breathing ventilates the Lungs Introduction ● Breathing the alternating inhalation and exhalation of air How an Amphibian Breathes ● Positive pressure breathing inflating the lungs with forced airflow ○ Muscles lower the floor of amphibian’s oral cavity to draw in air, then the floor rises with the mouth and nostril closed to force air down the trachea How a Bird Breathes ● Birds use eight or nine air sacs situated on either side of the lungs ○ Parabronchi tiny channels; sites of gas exchange in bird lungs ○ Require two cycles of inhalation and exhalation; only in one direction How a Mammal Breathes ● Mammals breathe by negative pressure breathing (by changing the air pressure within its lungs relative to the pressure of the outside atmosphere ● Negative pressure breathing pulling, rather than pushing, air into the lungs ○ Inhalation is always active and requires work, while exhalation is usually passive ● Diaphragm a sheet of skeletal muscle that forms the bottom wall of the cavity ○ Contracts and expands the thoracic cavity downwards during inhalation ○ Relaxes and the thoracic cavity moves upward during exhalation ● Tidal volume the volume of air inhaled and exhaled with each breath ● Vital capacity tidal volume during maximum inhalation and exhalation ● Residual volume air that remains after forced exhalation ● Lungs lose resilience and residual volume increases with age ● Maximum P in alveoli is always considerably less than in the atmosphere, and also less O2 in mammals than birds because mammals have unidirectional air flow Controls of Breathing in Humans ● Breathing control centers neural circuits in the medulla oblongata that establish breathing rhythm ○ Negativefeedback mechanism prevents lungs from overexpanding ● Sensors in the medulla and in major blood vessels can detect changes in pH and in response, increase/decrease the depth and rate of breathing ● Breathing control is only effective if ventilation is matched to blood flow through alveolar capillaries 42.7 Adaptations for gas exchange includes pigments that bind and transport gases Introduction ● High metabolic demands necessitate the change of large quantities of O and CO 2 2 Coordination of Circulation and Gas Exchange ● Partial pressures of O an2CO in 2e blood vary as gases move between air, blood, and other body tissues Respiratory Pigments Introduction ● O h2 low solubility in water, and thus low solubility in blood ● Animals consequently transport most of their O bound to2roteins called respiratory pigments, which greatly increase the amount of O carried in circulatory fluid 2 ○ Respiratory pigments circulate with the blood or hemolymph and often contained within specialized cells ● Variety of respiratory pigments have evolved in animals, and usually have a distinct color and consist of a metal bound to a protein ○ Hemocyanin blue; copper is its oxygenbinding component; found mollusks and many arthropods ○ Hemoglobin found in almost all vertebrates and many invertebrates; contained in erythrocytes and has four subunits (each with heme group and iron atom) so it can carry four molecules of O 2 ■ Also assists in buffering blood ○ Bohr Shift where CO producti2 is greater, hemoglobin releases more O , 2 which can then be used to support more cellular respiration Carbon Dioxide Transport ● Only about 7% of the CO released b2respiring cells is transported in solution in blood plasma, while the rest diffuses into erythrocytes and reacts with water Respiratory Adaptations of Diving Mammals ● One adaption is the capacity to store large amounts of O in the body 2 ● Another adaption is myoglobin (oxygenstoring protein located in the muscle cells) Chapter 40: Basic Principles of Animal Form and Function Overview: Diverse Forms, Common Challenges ● Anatomy biological form; the structure of an organism ● Physiology biological function; the processes and functions of an organism ● Example: the ears of a jackrabbit both provide an acute sense of hearing and help shed excess heat ○ Anatomy blood flowing through the ears transfers heat to the surrounding air ■ Physiology Increased blood flow in the cold, but reduced blood flow in the heat to maintain the proper body temperature 40.1 Animal form and function are correlated at all levels of organization Introduction ● The body plan, shape and size, of an animal is the result of a pattern of development programmed by the genome and thus a product of evolution Evolution of Animal Size and Shape ● Physical laws govern strength, diffusion, movement, and heat exchange ● Physical laws constrain evolution ○ Natural selection often results in similar adaptations between diverse organisms in facing similar environmental challenges ■ Example: the adaption of sharks, penguins, dolphins, and seals to have a streamlined body contour, a shape that is fusiform (tapered at both ends), to reduce drag while swimming ○ These laws influence body plans with regard to maximum size ■ As body dimensions increase, thicker skeletons are required for support and more muscle is required for proper locomotion ■ Examp le: the Tyrannosaurus rex stood more than 6m tall but could only run about 30 km/hr (19 miles/hour) Exchange with the Environment ● Animals must exchange materials with their environment, thus imposing limitations on body plans ○ Exchange occurs as substances dissolved in aqueous solutions move across the plasma membrane of each cell ○ Rates of exchange for nutrients, waste products, and gases are proportional to membrane surface area ○ The amount of material that must be exchanged to sustain life is proportional to volume ● Many animals with simple internal organization utilize direct exchange between cells and their environments ○ Example: the ponddwelling hydra has a saclike body that is two cell layers thick, exposing both the inner and outer cells to the pond water ○ Example: the flat shape also maximizes exposure such as that of a tapeworm ● Most animals are composed of compact masses of cells with complex internal organization, such that increasing the number of cells decreases the ratio of outer surface area to total volume ○ To overcome this, there is the evolutionary adaption of specialized surfaces that are extensively folded or branches to enable sufficient exchange ■ Example: in humans, the internal exchange surfaces of the digestive, respiratory, and circulatory systems have an area more than 25 times greater than that of the skin ● Internal body fluids exchange surfaces to body cells ○ Exchange between interstitial fluid and circulatory fluids, such as blood, enables cells to obtain nutrients and get rid of wastes ■ Interstitial fluid the fluid filling the spaces between cells and most animals ● A complex body plan is especially advantageous for land animals with highly variable external environments Hierarchical Organization of Body Plans ● Cells form a functional animal body based on emergent properties (properties that arise by way of successive levels of structural and functional organization ● Cells → tissues → organs → organ system → organism ○ Tissue an integrated group of cells with a common structure, function, or both ○ Organ a specialized center of body function composed of several different types of tissues ○ Organ system a group of organs that work together in performing vital body functions ● There are four main types of animal tissues: epithelial, connective, muscle, and nervous Exploring: Structure and Function in Animal Tissues ● Epithelial cells cover the outside of the body and line organ cavities within the body ○ Occurs as sheets of cells that are closely packed with tight junctions ○ Function has a barrier against mechanical injury, pathogens, and fluid loss ○ All epithelia are polarized (have two different surfaces) ■ The apical surface faces the lumen (cavity) or outside and is thus exposed to fluid or air, but specialized projections often cover this surface ■ The basal surface is attached to a basal lamina, a dense mat of extracellular matrix that separates the epithelium from the underlying tissue ○ Cuboidal epithelium diceshaped spells specialized for secretion ■ Ex: epithelium of kidney tubules, thyroid gland, and salivary glands ○ Simple columnar epithelium large, brickshaped cells often found where secretion or active absorption is important ■ Ex: lines the intestines, secreting digestive juices and absorbing nutrients ○ Pseudostratified columnar epithelium single layer of ciliated cells varying in height that functions to form a mucous membrane that lines portions of the respiratory tract ■ Ex: the beating cilia sweep the film of mucus along a surface ○ Simple squamous epithelium single layer of platelike cells that functions in the exchange of materials by diffusion ■ Ex: lines blood vessels and air sacs of lungs, where diffusion of nutrients and gases is critical ○ Stratified squamous epithelium multilayered and regenerates rapidly; commonly found on surfaces subject to abrasion ■ Example: outer skin and linings of the mouth, anus, and vagina ● Connective tissue, consists of a sparge population of cells scattered through an extracellular matrix, holds many tissues and organs together in place ○ This matrix generally consists of a web of fibers embedded in a liquid, jellylike, or solid foundation and contains fibroblasts (secrete fiber proteins) and macrophages (engulf foreign particles and any cell debris by phagocytosis) ○ Three kinds of connective tissue fibers join together to form different connective tissues ■ Collagenous fibers provide strength and flexibility ■ Reticular fibers join connective tissue to adjacent tissues ■ Elastic fibers make tissues elastic ○ Loose connective tissue most widespread connective tissue that binds epithelia to underlying tissue and holds organs in place; found in skin and throughout body ○ Fibrous connective tissue dense with collagenous fibers found in tendons, which attach muscles to bones, and in ligaments, which connect bones at joints ○ Bone a mineralized connective tissue that forms the skeleton through boneforming cells called osteoblasts depositing a matrix of collagen ○ Blood has a liquid extracellular matrix called plasma, containing water, salts, and dissolved proteins ■ In the plasma are erythrocytes (red blood cells) that carry oxygen, leukocytes (white blood cells) that function in defense, and platelets that aid in blood clotting ○ Adipose tissue stores fat in adipose cells that pads and insulates the body and stores fuel as fat molecules ○ Cartilage contains collagenous fibers embedded in a rubber complex that make a strong yet flexible support material ■ Forms the skeletons of any vertebrate embryos, which is later replaced by bone, and remains in some locations, such as between disks to act as cushions ● Muscle tissue consists of filaments containing the proteins actin and myosin, which together enable the muscles to contract and is thus the tissue responsible for nearly all types of body movement ○ There are three types of muscle tissue: skeletal, smooth, and cardiac ○ Skeletal muscle also called striated muscle, is attached to bones by tendons and is responsible for voluntary movements ○ Smooth muscle spindleshaped cells that lacks striations found in the walls of internal organs that are responsible for involuntary body activities, such as churning of the stomach and constriction of arteries ○ Cardiac muscle striated muscle that forms the contractile wall of the heart ● Nervous tissue functions in the receipt, processing, and transmission of information, and contains neurons and glia ○ In many animals, a concentration of nervous tissue forms a brain, an informationprocess center ○ Neurons also called nerve cells, are the basic unit of the nervous system ■ Receive nerve impulses from other neurons via its cell body and dendrites ■ Transmit nerve impulses via axons, which are often bundled into nerve ○ Glia also called glial cells, help nourish, insulate and replenish neurons; in some cases, modulate neuronal function Coordination and Control ● Coordinated activity between an animal’s tissues, organs, and organ systems require communication ● The endocrine system releases signaling molecules called hormones into the bloodstream to reach all locations of the body ○ Different hormones have different effects, and only cells with the receptors for a particular hormone will respond ○ Hormones may affect a single location or various locations ○ Hormones are relatively slow acting, but are often longlasting, as they can remain in the blood stream for seconds, minutes, or hours ○ This system is well suited for coordinating gradual changes such as growth and development, reproduction, metabolic processes, and digestion ○ Example: only the cells of the thyroid gland have the receptor for thyroidstimulating hormone, which when bonded the thyroid cells release the hormone causing cells in nearly every tissue to increase oxygen consumption and heat production ● In the nervous system, neurons transmit signals called nerve impulses between specific locations in the body, following the same type of pathway no matter the distance ○ Nerve impulses travel along dedicated communication lines consisting of mainly axons, and travel as changes in voltage ○ Four types of cells can receive nerve impulses: other neurons, muscle cells, endocrine cells, and exocrine cells ○ Conveys information by the pathway the signal takes ○ Transmission is extremely fast, taking a fraction of a second to reach the target ○ Last only a fraction of a second ○ This system is well suited for directing immediate and rapid responses in the environment, especially in controlling fast locomotion and behavior ○ Example: a person can distinguish between musical notes because the frequency of each note activates different neurons connecting the ear to the brain 40.2: Feedback control maintains the internal environment in many animals Regulating and Conforming ● Regulator an animal that uses its internal mechanisms to control internal change in the face of external fluctuation ○ Example: the river otter’s temperature is independent of the water it is in ● Conformer an animal that allows its internal condition to change in accordance with external changes in a particular environmental variable ○ Example: the largemouth bass forms to the temperature of the lack it inhabits ● An animal may regulate some internal conditions while allowing others to conform ○ Example: the largemouth bass conforms to the temperature of the surrounding water, but the solute concentration in its blood is independent of the water Homeostasis Introduction ● Homeostasis refers to the maintaining of internal balance ○ In achieving this, animals can maintain relatively constant internal environment despite significantly changing external environment Mechanisms of Homeostasis ● An animal achieves homeostasis by maintain a variable at or near a particular value, called a set point ● Fluctuations above or below this point serve as a stimulus ● Stimulus is then detected by a receptor called a sensor ● After receiving a signal from the sensor, a control sensor generates an output that triggers a response (a physiological activity that helps return the variable to the set point) ● Example: the heating system in a home Feedback Control in Homeostasis ● Homeostasis in animals relies strongly on negative feedback and little on positive feedback ● Negative feedback a control mechanism that reduces the stimulus ○ Ex: the body producing sweat to decrease heat during a workout ● Positive feedback a control mechanism that amplifies the stimulus ○ Help drive process to completions ■ Example: heightening contractions during childbirth ● Homeostasis moderates but does not eliminate internal change, such that there isn’t always a set point, but rather a normal range Alterations in Homeostasis ● Set points and normal ranges can change under various circumstances, and these regulatory changes are even essential to normal body functions ○ Example: the radical shift in hormone balance that occurs during puberty ● Certain cyclic alterations in metabolism reflect a circadian rhythm (a set of physiological changes that occur roughly every 24 hours) ○ Example: the release of melatonin at night during the sleep cycle ● The normal range of homeostasis may also change through acclimatization (the gradual process by which an animal adjusts to changes in its external environment) ○ Acclimatization is a temporary change, not to be confused with adaption ○ Example: An elk moving into the mountains from sea level adjusts its kidney function to keep blood pH in normal range Chapter 46: Animal Reproduction 46.1 Both asexual and sexual reproduction occur in the animal kingdom Introduction ● Two modes of animal reproduction: sexual and asexual ○ Sexual reproduction fusion of haploid gametes forms a diploid cell (zygote) ■ Animal that develop can give rise to gametes by meiosis ■ Egg female gamete; nonmotile and large ■ Sperm male gamete; motile and much smaller ○ Asexual reproduction new individuals generated without fusion of egg and sperm ■ Most reproduction relies entirely on mitotic cell division Mechanisms of Asexual Reproduction ● Budding new individuals arise from outgrowths of existing ones ○ Ex: stony corals ● Fission separation of a parent organism into two individuals of approximately equal size ● Twostep Process ○ Fragmentation breaking of the body into several pieces ○ Regeneration regrowth of lost body parts ○ Ex: Annelid worms, numerous sponges, cnidarians, tunicates ● Parthenogenesis egg develops without being fertilized ○ Occurs in certain species of bees, wasps, and ants; rare in vertebrates ○ Progeny can be either haploid or diploid Sexual Reproduction: An Evolutionary Enigma ● Advantages to sexual reproduction ○ Varied genotypes may enhance reproductive success when environmental factors change rapidly ○ Beneficial gene combinations through recombination might speed up adaptation ■ Only when the rate of beneficial mutations is high and population size is small ● Asexual reproduction is most advantageous in stable, favorable environments ○ More offspring produced per generation when compared to sexual reproduction Reproductive Cycles ● Reproductive cycles are controlled by hormones so that animals reproduce only when sufficient energy sources are available and environmental conditions are favorable ● Ovulation the release of mature eggs; occurs at the midpoint of each cycle ● Seasonal changes are important cues for reproduction; negatively affected by global climate change ● Reproductive cycles are found among animals that reproduce sexually and asexually Variation in Patterns of Sexual Production ● Hermaphroditism where an individual has both male and female reproductive systems ○ Evolutionary adaptation for enhanced reproductive success ● Sex reversal 46.2 Fertilization depends on mechanisms that bring together sperm and eggs of the same species Introduction ● Fertilization union of sperm and egg ○ External fertilization females release eggs into environment, where male then fertilizes them ○ Internal fertilization sperm are deposited in or near the female reproductive tract; fertilization then occurs within the tract ● Moist habitat is almost always required for external fertilization to prevent the gametes from drying out and to allow sperm to swim to eggs ● Spawning individuals cluster in the same area and release their gametes into the water at the same time ○ Chemical signals that one individual gamete generates in releasing gametes triggers others to release gametes ○ Environmental cues, such as temperature or day length, may trigger gamete release ● When external fertilization is not synchronous of a population, individuals may exhibit courtship ● Internal fertilization is an adaptation that allows sperm to reach an egg even in a dry environment ● No matter how fertilization occurs, the mating animals may use pheromones (chemicals released by one organism that can influence the physiology and behavior of another) ○ Pheromones small, volatile or watersoluble molecules that disperse into the environment and are active at very low concentrations Ensuring the Survival of Offspring ● Internal fertilization associated with fewer gametes but higher fraction of survival ○ Associated with greater protection of embryos and parental care ● Parental care is widespread among animals Gamete Production and Delivery ● Gonads organs that produce gametes; found in many but not all animals ● More elaborate reproductive systems include sets of accessory tubes and glands that carry, nourish, and protect the gametes and sometimes the developing embryos ● Spermathecae sacs in which sperm may be stored for extended periods ○ Part of the female reproductive system in many insect species; allows fertilization to occur under optimal conditions ● Cloaca a common opening for the digestive, urinary, and reproductive tracts found in many nonmammalian vertebrates but in few mammals ○ Males of these species lack a penis and instead release sperm by turning the cloaca inside out ● Monogamy the sustained sexual partnership of two individuals; rare among animals ○ Some mechanisms enhance reproductive success of a male with a particular female and diminish the chance of the female reproducing successfully with another male ○ Females play a major role in determining the outcome of multiple matings 46.3 Reproductive organs produce and transport gametes Human Male Reproductive Anatomy Introduction ● External reproductive organs are the scrotum and the penis ● Internal reproductive organs are the gonads (produce sperm and reproductive hormones), accessory glands (secrete products essential to sperm movement), and ducts (carry the sperm and glandular secretions) Testes ● Testes the male gonads; produce sperm in highly coiled tubes called seminiferous tubules ● Scrotum a fold of the body wall that maintains testis temperature ● Develop in the abdominal cavity then descend into the scrotum just before birth Ducts ● From the seminiferous tubules, sperm pass into the coiled duct of the epididymis ○ Takes three weeks for sperm to travel the 6m length, during which they complete maturation and become motile ● Ejaculation sperm are propelled from each epididymis through a muscular duct called the vas deferens (one from each epididymis) ○ Vas deferens extends around and behind urinary bladder, where it then joins a duct from the seminal vesicle, forming a short ejaculatory duct ● Ejaculatory duct opens into the urethra (outlet tube for both the excretory and the reproductive system) ○ Urethra runs through the penis and opens to the outside at the tip of the penis Accessory Glands ● Three accessory glands (seminal vesicles, prostate gland, and the bulbourethral gland) produce secretions that combine with sperm to form semen (fluid that is ejaculated) ● Two seminal vesicles contribute about 60% of the volume of semen ○ Fluid from here is thick, yellowish, and alkaline; contains sugar fructose (provides most of sperm’s energy), a coagulating enzyme, ascorbic acid, and local regulators called prostaglandins ● Prostate gland secretes its products directly into the urethra through small ducts ○ Fluid from here is thin and milk; contains anticoagulating enzymes and citrate (sperm nutrient) ● Bulbourethral glands a pair of small glands along the urethra below the prostate ○ Before ejaculation, secrete clear mucus that neutralizes acid urine remaining in the urethra Penis ● Contains the urethra and three cylinders of spongy erectile tissue ● During sexual arousal, erectile tissue fills with blood from arteries; resulting erection enables penis to be inserting into vagina ○ Alcohol consumption, drugs, aging, and emotional issues may make this difficult ● All animals rely on penile erection for mating, but some have a bone called a baculum ● The main shaft of the penis is covered by relatively thick skin ○ The glans (head) of the penis has a much thinner outer layer for sensitivity ■ Surrounding by the prepuce (foreskin) Human Female Reproductive Anatomy Introduction ● External reproductive structures are the clitoris and two sets of labia (surround the clitoris and vaginal opening) ● Internal organs consist of gonads (produce eggs and reproductive hormones) and a system of ducts and chambers (receive and carry gametes and house the embryo and fetus) Ovaries ● Ovaries come in a pair; female gonads; flank the uterus and held in place in the abdominal cavity by ligaments ● Outer layer of each ovary is packed with follicles (consists of an oocyte, a partially developed egg) surrounded by supporting cells ○ Supporting cells nourish and protect the oocyte during much of its development Oviducts and Uterus ● Oviduct (fallopian tube) extends from the uterus to a funnellike opening at each ovary ● Upon ovulation, cilia on the epithelia lining of the oviduct help collect the egg and conveying it to the uterus (the womb) ● Uterus thick, muscular organ that can expand during pregnancy to accommodate a fetus ○ Endometrium lining of the uterus; richly supplied with blood vessels ○ Cervix neck of the uterus; opens into the vagina Vagina and Vulva ● Vagina muscular, elastic chamber where the penis is inserted and sperm is deposited ○ Also serves as the birth canal, which opens to the vulva ● Vulva collective term for external female genitalia ● Labia majora encloses and protects the rest of vulva ● Labia minora slender skin folds around the vaginal opening and urethra ● Hymen thin piece of tissue that partly covers the vaginal opening in humans at birth and usually until sexual intercourse or vigorous activity ruptures it ● Clitoris sensitive point for sexual stimulation ● Sexual arousal induces the vestibular glands to secrete lubricating mucus to facilitate intercourse Mammary Glands ● Mammary glands present in both sexes but only produce milk in females ● Not part of the reproductive system, but important for reproduction Gametogenesis ● Gametogenesis the production of gametes ● Spermatogenesis the formation and development of sperm (may take about 7 weeks per sperm) ● Oogenesis the development of mature oocytes (eggs) ○ Immature eggs form in the ovary but do not complete development until years later ● Differences between spermatogenesis and oogenesis ○ Only in spermatogenesis do all four products of meiosis develop into mature gametes; oogenesis produces one large eggs and the smaller cells (polar bodies) degenerate ○ Spermatogenesis occurs throughout adolescence and adulthood; oogenesis is complete before birth and production of mature gametes ceases at about age 50 ○ Spermatogenesis produces mature sperm in a continuous sequence; there are interruptions in oogenesis 46.5 In placental mammals, an embryo develops fully within the mother’s uterus Conception, Embryonic Development, and Birth Introduction ● Fertilization called conception in humans; occurs when sperm fuses with an egg (mature oocyte) in an oviduct ● Zygote begins series of cell divisions called cleavages about 24 hours after fertilization ● Blastocyst a sphere of cells surrounding central cavity; forms about 4 days later ● A few days later, embryo implants into the endometrium of the uterus ● Pregnancy also called gestation; the condition of carrying one or more embryos in the uterus ○ Human pregnancy lasts about 266 days (divided into three trimesters); rodent gestation 21 days; 270 days in cow; 600 days in elephants First Trimester ● Implanted embryo secretes hormones to signal its presence and regulate mother’s reproductive cycle, including human chorionic gonadotropin (hCG) to prevent menstruation ● Ectopic pregnancy fertilized egg lodges in oviduct; cannot often be sustained ● During first 24 weeks, embryo obtains nutrients from the endometrium ○ Trophoblast, outer layer of blastocyst, grows outwards and mingles with endometrium ■ Eventually helps form placenta (contains embryonic and maternal blood vessels), which supplies nutrients, provides immune protection, exchanges respiratory gases, and disposes of metabolic wastes ● Occasionally, embryo splits during first month, resulting in identical (monozygotic) twins ○ Fraternal (dizygotic) twins result when two follicles mature in a single cycle ● Main period of organogenesis development of the body organs ● At 8 weeks, all the major structures of the adult are present in rudimentary form, and the embryo is called a fetus (about 5cm long here) ● In the mother, mucus in cervix forms plug to protect against infection, breasts and uterus get larger, and both ovulation and menstruation cycling stop Second and Third Trimesters ● During second trimester, fetus grows to about 30 cm and is very active ○ Hormone levels stabilize as hCG secretion declines, the corpus luteum deteriorates, and the placenta completely takes over the production of progesterone (the hormone that maintains pregnancy) ● During third trimester, fetus grows to about 50 cm and fetal activity may decrease ○ Mother’s abdominal organs become compressed and displaced ● Childbirth begins with labor a series of strong, rhythmic uterine contractions that push the fetus and placenta out of the body ○ Local regulators (prostaglandins) and hormones (estradiol and oxytocin) induce and regulate further contractions in a positive feedback loop ● Labor has three stages ○ 1. Thinning and opening up (dilation) of the cervix ○ 2. Expulsion, or delivery, of the baby ○ 3. Delivery of the placenta ● Lactation (production of mother’s milk) is a unique aspect of postnatal care Maternal Immune Tolerance and the Embryo of the Fetus ● Mother’s body does not reject fetus as foreign object because the overall regulation of the immune system changes during pregnancy Chapter 42: Circulation and Gas Exchange Overview: Trading Places ● Resources that animal cells require (like nutrients and O ) enter the cytoplasm by 2 crossing the plasma membrane and metabolic byproducts (like CO ) exit 2e cell by crossing the plasma membrane ● Exchange between animal and its surroundings ultimately occur at the cellular level ● Example: Axolotl have feathery red gills, which have tiny blood vessels close to the surface, that allow for exchange 42.1 Circulatory systems link exchange surfaces with cells throughout the body Introduction ● Small, nonpolar molecules can move between cells and their immediate surroundings by diffusion, but this process is very slow for distances farther than a few millimeters ○ Time it takes substance to diffuse is proportional to the square of distance ■ Ex: If it takes 1 second to diffuse 100 micrometers, it takes 100 seconds to diffuse 1 millimeter, and almost 3 hours to diffuse 1 cm ○ This places a constraint on animal body plan ○ Diffusion is only rapid over very small distances ● Natural selection solutions to allow all cells to participate in exchange ○ 1. Body size and shape that keep many or all cells in direct contact with the environment ■ This is only found in certain invertebrates like cnidarians and flatworms ○ 2. A circulatory system that moves fluid between each cell’s immediate surroundings and tissues where exchange with the environment occurs ■ Found in all other animals Gastrovascular Cavities ● Certain animals lack distinct circulatory systems, and in place have central gastrovascular cavities that functions in distribution of substances and in digestion ○ Fluid bathes both inner and outer tissues, facilitating exchange of gases and waste ○ While not all cells are in direct exchange, the body wall is only two cells allowing exchange through diffusion ○ Example: hydras, jellies, other cnidarians ● Planarians and most other flatworms survive without a circulatory system ○ Have gastrovascular cavity and flat body ■ Flat body optimizes diffusional exchange by increase surface area and minimizing diffusion distances Evolutionary Variation in Circulatory Systems Introduction ● Circulatory system minimizes the distances a substance must diffuse to enter/leave a cell General Properties of Circulatory Systems ● Circulatory system has three basic components: a circulatory fluid, a set of interconnection blood vessels, a muscular pump (the heart) ● Heart powers circulation by using metabolic energy to elevate hydrostatic pressure of the circulatory fluid, which then flows through vessels then back to the heart ● Circulatory system functionally connects aqueous environment of body cells to the organs that exchange gas, absorb nutrients, and dispose of wastes by transporting fluid throughout the body ○ Ex: Inhaled O d2fuses across two layers of cells in the lungs to the blood, which streams through the body powered by the heart, allowing the O in 2 to diffuse a short distance to fluid that directly bathes the cell ● Circulatory systems have arisen during evolution, representing adaptations to constraints ○ Either open or closed, vary with regard to number of circuits in the body, and rely on pumps that differ in structure and organization Open and Closed Circulatory Systems ● Open circulatory system circulatory fluid bathes the organs directly ○ Circulatory fluid, called hemolymph, is also the interstitial fluid that bathes body cells ○ Contraction of heart(s) pumps hemolymph through circulatory vessels into interconnected sinuses (spaces around the organs) where chemical exchange occurs ○ Relaxation of the heart draws hemolymph back in through pores, which are equipped with valves that close when the heart contracts ○ Body movements help circulate hemolymph by periodically squeezing sinuses ○ This is present in arthropods and most molluscs ■ Larger crustaceans also have a more extensive vessel system and an accessory pump ● Closed circulatory system a circulatory fluid, called blood, is confined to vessels and is distinct from the interstitial fluid ○ Heart(s) pump blood into large vessels that branch into smaller ones ○ Chemical exchange occurs between blood and interstitial fluid, and between interstitial fluid and body cells ○ This is present in annelids, cephalopods, and all vertebrates ● There are advantages to each system ○ Closed lower hydrostatic pressures make them less costly in terms of energy expenditure; some circulatory systems have additional functions ■ Ex: spiders use the hydrostatic pressure to extend legs ○ Open higher blood pressure for more effective delivery of O and n2rients, well suited to regulating distribution of blood to different organs Organization of Vertebrate Circulatory Systems Introduction ● Closed circulatory system of humans and other vertebrates is often called the cardiovascular system ● Blood circulates to and from the heart through a network of vessels ● Three main types of blood vessels ○ Arteries carry blood away from the heart to organs ■ Branch into arterioles small vessels that convey blood to capillaries ○ Capillaries microscopic vessels with very thin, porous walls ■ Capillary beds network of capillaries that infiltrate every tissue, allowing exchange of chemicals by diffusion between interstitial fluid ■ Converge into venules, which converge into veins ○ Veins vessels that carry blood back to the heart ● Arteries and veins are distinguished by the direction they carry blood ○ Only exception are portal veins carry blood between capillary beds ● Hearts of all vertebrates contain two or more muscular chambers; number and extent of separation differ substantially between groups of vertebrates ○ Atria chambers that receive blood entering the heart ○ Ventricles chambers that are responsible for pumping blood out of the heart Single Circulation ● Single circulation arrangement in which blood passes through the heart once in each complete circuit ○ Occurs in hearts with two chambers, like those of bony fish, rays, and sharks ○ Blood entering the heart collects in the atrium before transfer to the ventricles which then contracts pumping blood to the gills where exchange occurs ● Blood that leaves the heart passes through two capillary beds before returning to the heart ○ When blood passes through capillary beds, blood pressure drops substantially, limiting the rate of blood blood in the rest of body ■ Contraction and relaxation of muscles as the animal swims helps accelerate circulation Double Circulation ● Double circulation arrangement where the circulatory system has two circuits ○ Pumps for two circuits are combined into a single organ, the heart, which simplifies coordination of the pumping cycles ○ Right side of heart delivers oxygenpoor blood to capillary beds of gas exchange tissues where there is net movement of O in2 the blood and CO out2 ■ Called pulmonary circuit of capillary beds are all in the lungs as in reptiles and mammals ■ Called pulmocutaneous circuit if it includes capillaries in both the lungs and skin as in many amphibians ○ Oxygen rich blood then enters the left side of the heart, which propels it to capillary beds in organs and tissues throughout the body ○ Oxygenpoor blood then returns back to the heart, completing the systemic circuit ● Provides vigorous flow of blood to brain, muscles, and other organs because the heart
Are you sure you want to buy this material for
You're already Subscribed!
Looks like you've already subscribed to StudySoup, you won't need to purchase another subscription to get this material. To access this material simply click 'View Full Document'