Life103-Week 14 Notes
Life103-Week 14 Notes Life 103
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This 8 page Class Notes was uploaded by Addy Carroll on Saturday April 30, 2016. The Class Notes belongs to Life 103 at Colorado State University taught by Dr. Dale Lockwood and Dr. Tanya Dewey in Winter 2016. Since its upload, it has received 17 views. For similar materials see Biology of organisms-animals and plants in Biology at Colorado State University.
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Date Created: 04/30/16
Life 103 Notes Adapted from the lecture notes of Dr. Tanya Dewey The Immune System • Immunization: the process of generating an immune response in an individual in order to protect against disease • Inoculation: exposure to a disease agent in order to prompt a reduced infection and then immunity from the disease • Vaccination: exposure to modified disease agents (dead or altered) to induce an immune reaction that confers immunity to a disease • Herd immunity -When the largest proportion of a community is immune (cannot get or carry the disease), then it reduced the probability that people who are not immune will contract the disease • Immune system (see textbook figure 43.2) -Prevent entry of pathogens -Detect entry of pathogens (distinguish non-self) -Eliminate pathogens -Innate Immune System: first responders (found in all animals) -Adaptive Immune System: requires activation (found in all vertebrates) • Innate Immunity -Barrier Defenses ~Prevent things from entering -Skin -Mucous membranes trap pathogens in mucous -Secretions bathe surfaces; contain lysozymes that destroy cell walls of some bacteria -Acidic body pH kills many pathogens -Cellular Innate Defenses ~Detect invader and alert first responders via TLR receptors (see textbook figure 43.6) ~TLR receptors bind alien molecules not found in animals (viruses, bacteria, fungi)=reliable signals of invasion -Double stranded RNA’s and DNA with unmethylated CG sequences -Lipopolysaccharides -Flagellin -Trigger phagocytosis (the process where a cell engulfs/ingests/eliminates another cell) (see textbook figure 43.3) ~Neutrophils: found throughout blood ~Macrophages: found throughout whole body (blood and tissues) ~Dendritic cells: in tissues that contact the environment; once activated they migrate to lymph nodes and stimulate adaptive immune system ~Natural killer cells: recognize infected or cancerous cells and trigger lysis (rupture of cell membrane) or apoptosis (cell death) ~Antimicrobial proteins: pathogen recognition triggers production of proteins that disrupt cell membranes or viral replication ~Inflammatory response: injury or infection prompts a systemic response that involves signaling molecules (see textbook figure 43.8) -Most cells release histamine (signaling molecule) -Histamine causes dilation and increased permeability of blood vessel; fluid in tissues, swelling -Cytokines released by specialized cells promote blood flow; redness and heat -Pus: phagocytic cells and debris • Adaptive Immunity (see textbook figure 43.20) -Recognition of specific pathogens -Specific response to those pathogens -Lymphocytes ~B cells ~T cells -Antigen: a toxin or other foreign substance that induces an immune response in the body, activating B or T cells (lymphocytes) -B cell antigen recognition (see textbook figure 43.9, 43.10) ~B cells detect intact antigens on cells or circulating free in the body via specific antigen binding sites ~Antigen specific binding with B cell receptor causes activation -Clonal proliferation of that type of B cell (clonal selection) -Proliferation of plasma cells that secrete antibodies specific to that antigen -Memory B cells -T cell antigen recognition (see textbook figure 43.11, 43.12) ~T cells recognize antigens displayed on MHC molecules on host cell surfaces (dendritic cells) via specific antigen binding sites ~Activation causes -Proliferation of that T cell (clonal selection) -Proliferation of helper T cells and cytotoxic T cells -Memory T cells -4 Characteristics of Adaptive Immunity ~Diversity of lymphocytes and receptors -Random rearrangements of genes that code for variable, joining, and constant regions in antigen receptor sites and different combinations of light and heavy chains contributes to tremendous diversity (3.5 million) (see textbook figure 43.13) ~Self tolerance -B and T cells tested for reaction to self as they mature, self reactive combinations are destroyed ~Cell proliferation (clonal selection) (see textbook figure 43.14) -Interaction with an antigen activates cells to proliferate ~Immunological memory (see textbook figure 43.15) -This is the adaptive (or acquired) part and is the result of memory cells • Improper Immune System Function -Allergies: specific B cells that target parasitic worms ~Developed regions have high incidence of allergies and autoimmune disorders, while regions with common parasitic infections have low incidence -Autoimmune diseases: not recognizing self -Immunodeficiency: SCID, AIDS -Hygiene hypothesis: lack of exposure to infections and parasites suppresses development of the immune system Hormones and Chemical Signaling • Hormones and Chemical Signaling: communicating and coordinating among tissues • Anti-diuretic hormone (ADH, vasopressin) -Function: retain water in body tissues by increasing absorption of fluids in the collecting duct of the nephron (diuresis=production of excessive urine) -Hypothalamus detects increased osmolarity of blood -Nerve impulse is sent to pituitary gland, which secretes ADH -ADH receptors in kidney -Increased permeability of membranes to water in the collecting duct and distal tubule causes increased water re-absorption -Integration between nervous system and endocrine system (i.e. chemical signaling) -Feedback mechanisms (here it is a negative feedback mechanism) -Chemical signals act on distant tissues (collecting duct and distal tubule) -Result: maintaining homeostasis • Modes of chemical signaling (see textbook figure 45.2) -Endocrine: global-endocrine glands secrete hormones into the blood stream to reach target cells anywhere in the body -Paracrine: local-target cells are near the diffusing cell -Autocrine: local-secreting cells are also target cells; secretes something that also has an effect on self -Synaptic signaling: local-neurotransmitters diffuse across synapses -Neuroendocrine signaling: global-neurons secrete hormones into the bloodstream to reach target cells anywhere • Endocrine System -Endocrinology: the study of the endocrine system, hormones, and their role in physiological regulation of the body -Endocrine system: set of glands that secrete hormones into the bloodstream -Endocrine: ductless glands (secret into blood; secretes something to an area within your body) -Exocrine: ducted glands (ducts carry secretions directly onto surfaces or into body cavities; secretes something to an area outside your body) -Functions: ~Maintain homeostasis ~Integrate and regulate growth and development ~Control sexual reproduction • Hormones -Hormones: chemical secreted into the bloodstream that travels to have an impact on specific target cells -Target cells have hormone-specific receptors -Often regulate cell reactions by changing gene expression (i.e. they are transcription factors) -Hormones have large impacts at low concentrations ~Signal transduction -The transmission of molecular signals from a cell’s exterior to its interior -Molecule can bind to receptors at the cell membrane or pass through membrane and bind to receptors in the cell ~Amplification -Molecular signals can be amplified at any step, resulting in a large impact from low concentrations of molecules -Hormone solubility influences signal transduction (see textbook figure 45.5) ~Water soluble: cannot diffuse through plasma membranes; requires receptor proteins on the cell surface ~Lipid soluble: can diffuse through plasma membranes; receptor proteins can be inside of a cell -Water-soluble hormone: epinephrine (see textbook figure 45.6) ~Hormone binds with receptor protein coupled with G protein ~Catalyzes cAMP synthesis ~Activates protein kinase A ~Catalyzes glycogen breakdown -Glycogen: energy storage polysaccharide -Lipid-soluble hormone: estradiol (see textbook figure 45.7) ~Hormone diffuses through plasma membrane ~Binds with receptor protein ~Receptor protein+hormone complex causes change in gene expression -Multiple impacts of hormones ~Hormones bind with target receptors ~Target receptors can be found in many tissues ~Specific response to hormone binding can vary with tissue type -Same receptors-different responses -Different receptors • Pheromones -Chemicals secreted in body fluids to influence the behavior of other individuals ~Important in eusocial and social animals ~Influence social dynamics in many ~Involve communication between individuals or species • Negative feedback regulation-example -Stimulus: Low pH triggers endocrine secretion of hormone -Hormone reaches target cells (pancreas) -Bicarbonate is released, causing increased pH -Increased pH removes stimulus -Response reduces stimulus • Positive feedback regulation-example -Stimulus: suckling causes neurohormone release -Hormone reaches target cells (mammary glands) -Milk is produced -Milk production causes suckling, etc. -Response enhances stimulus • Coordination of nervous and endocrine systems-the hypothalamus (see textbook figure 45.13) -Receives information from nerves -Initiates endocrine responses via pituitary glands Producing Offspring • What is reproduction? -Reproduction: the production of offspring (young, children, descendants, etc.) by asexual or sexual processes -A population outlives its members only by reproduction, the generation of new individuals from existing ones -Offspring share genes to varying degrees with parents (depending on mode of reproduction) -The genes that survive, and in turn the organisms they make, are the winners in the existence game • Asexual reproduction -Offspring arise from a single organism and inherit the genes of that parent only -Offspring are genetic copies of parents -Reproduction without the fusion of gametes -Primary form of reproduction in Archaeabacteria (Archaea), Eubacteria (Bacteria), and protists -Common form of reproduction in fungi and plants -Rare in animals -Some forms of asexual reproduction ~Binary fission: parent cell divides into two -Not in animals ~Fragmentation: new organism grows from part of the parent -In some sponges, flatworms, annelids, and echinoderms ~Budding: new individuals form from outgrowths (“buds”) of mature organisms -In some sponges, cnidarians, acoel flatworms, and echinoderms ~Parthenogenesis: formation of a new individual from an unfertilized egg -In some arthropods, rotifers, flatworms, snails, reptiles, amphibians, and sharks -Costs of asexual reproduction ~Offspring are identical to parents -Benefits of asexual reproduction ~Offspring are identical to parents ~Every individual can reproduce • Sexual reproduction -Fusion of gametes (sperm and egg) to form a new individual (zygote) -Gametes are formed via meiosis (reduction in ploidy) -Primary form of reproduction in plant and animals -Costs of sexual reproduction ~Halves the number of organisms that can have offspring relative to asexual species ~Find mates (correct species, correct gender, appropriate timing, etc.) ~Offspring represent typically only 50% of genes of the parent ~Mating can be dangerous -Benefits of sexual reproduction ~Offspring are genetically variable -In spite of the costs, sexual reproduction dominates multicellular organisms • Why reproduction is important -Recombination ~Combine beneficial mutations ~Avoid effects of deleterious mutations ~Generate novel genotypes -Red Queen Hypothesis ~Reduce susceptibility to parasites, diseases, or predators; a co- evolutionary “arms race” -Remove deleterious mutations from a lineage -Evidence ~Sexual reproduction occurs in new or changing environments ~Asexual reproduction occurs in constant or unchanging environments -In simulations, if death is random and all else is equal, then asexual reproduction wins (faster and less costly reproduction) -If death is not random (through disease, parasite, or predator), sexual reproduction generates more genes to fight the disease, parasite, or predator and sexual reproduction wins (generates more variability) • Hormonal control of reproduction -Hormones regulate sexual behavior, such as courtship displays, aggression, parental care, etc. • Pheromonal control of reproduction -Pheromones: hormones used to communicate between individuals -Used to communicate sexual receptivity and convey individual information -Used in social control to suppress the reproductive activity of conspecifics • Challenges of producing offspring -Generate gametes ~Females, by definition, produce eggs=smaller number and higher investment per gamete ~Males, by definition, produce sperm=larger number and vastly lower investment per gamete ~This pattern is called anisogamy -Find a mate ~Sessile or solitary species have a very hard time finding mates ~Danger of interacting with potential mates ~Hermaphrodism: has both male and female reproductive organs ~Simultaneous hermaphrodism: male and female at the same time -Fertilization-internal vs. external ~Synchronous external fertilization is spawning ~Asynchronous external fertilization requires coordination between individuals ~Both require water ~Internal fertilization does not require water ~Typically requires cooperation and coordination of reproductive anatomies ~Females can “cheat,” so males evolve strategies to increase competitiveness of their sperm -Support during development ~Pre-hatching or birth ~Nutrition supplied to developing embryo (yolk, gestation, etc.) ~Protection, such as nests, gestation, or guarding ~Post-hatching or birth ~Providing nourishment, protecting, teaching, etc. • Reproductive success -The passing of genes from one generation to the next or the number of offspring of an individual that survive and reproduce -How do animals maximize reproductive success? ~There are many strategies ~Example: Sequential hermaphrodism in fish (one sex at a time, both sexes during the lifetime) ~Protandrous: male first, female second -Larger body mass=produce more eggs -So large females have higher reproductive success ~Protogynous: female first, male second -Larger body mass=better ability to control resources in a territory and have multiple female mates -So large males have higher reproductive success
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