Life103-Week 15 Notes
Life103-Week 15 Notes Life 103
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This 6 page Class Notes was uploaded by Addy Carroll on Friday May 6, 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 22 views. For similar materials see Biology of organisms-animals and plants in Biology at Colorado State University.
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Date Created: 05/06/16
Life 103 Notes Adapted from the lecture notes of Dr. Tanya Dewey Sensing the Environment • Sensory Pathways -Reception: sensory receptor (cells, organs, part of cells) detects a stimulus -Transduction: converts the energy from a stimulus to a membrane potential (charge) -Transmission: the stimulus travels as nerve impulses -Perception: the brain interprets the transmission -Sensory receptor (cells, organs, parts of cells) detects a stimulus (reception), which results in a change of membrane potential in the receptor (transduction) -Graded response: magnitude of membrane potential change is influenced by stimulus intensity -Transduction converts the energy from a stimulus to a membrane potential (charge) -Membrane Potential: A difference in charge between the inside and outside of a cell (see textbook figure 48.6) ~i.e. voltage difference; positive outside and negative inside -Selectively permeable membrane -Active transport and selective permeability maintains membrane potential -Perception is the processing of stimuli in the brain -Synesthesia: stimulation of one sensory or cognitive pathway leads to automatic, involuntary experiences in a second sensory or cognitive pathway • Amplification -Sensory stimuli are strengthened during transduction either via accessory structures (middle ear bones, for example) or enzyme catalysis of secondary messengers in cells • Sensory adaptation -Receptors decrease responsiveness with continued stimulation • Sensory receptors -Mechanoreceptors respond to mechanical energy such as pressure, touch, stretch, motion, and sound ~Example: Lateral line system (see textbook figure 50.14) -Hair cells detect motion (see textbook figure 50.11) -Direction of movement changes the trajectory and pattern of the membrane potential (action potential) ~Example: mammalian hearing (see textbook figure 50.10) -Outer/middle/inner ear -Vibrations in air cause vibration of tympanic membrane -Tympanic membrane contacts middle ear bones -Middle ear bones amplify and transmit vibrations to inner ear fluid in cochlea -Vibrations detected by hair cells in basilar membrane ~Example: echolocation-detecting reflected sound -Note differences in ear (pinna) shape and size -Ear shape determines what frequencies of sound are most efficiently detected-both reflected sound and direct sound -Chemoreceptors respond to chemical stimuli (smell or taste) ~Gustation: taste (see textbook figure 50.24) ~Taste receptors in taste buds ~Olfaction: smell (see textbook figure 50.25) ~Thousands of odorant receptors ~Each detects a single odorant ~Over 3% of human genes ~Dogs have 300 million olfactory receptors while humans only have 6 million olfactory receptors ~Vomeronasal organ (Jacobson’s organ): detects pheromones, detects molecules at very low concentration ~Flehmen and “tasting” the environment -Electromagnetic receptors detect electromagnetic energy such as visible light, electricity, and magnetism ~Single evolutionary origin of vision indicated by shared genes that control photoreceptor development ~Photoreceptor: cell that converts light into stimulus via photosensitive proteins (visual pigments) ~Example: simple eyes detect light (see textbook figure 50.15) ~Example: compound eyes (see textbook figure 50.16) -Many ommatidia (light detectors), each with a lens ~Example: vertebrate vision (see textbook figure 50.17) -Iris and pupil -Lens focuses light -Retina lined with photoreceptors -Rods are more sensitive to light and cones detect color -Retinal: light absorbing molecule -Opsin: associated protein -Light absorption changes retinal arrangement and activates opsin -Activating rhodops causes signal transduction via enzyme cascade -Changing membrane potential ~Example: detecting magnetic fields -Magnetite crystals in tissues orient to Earth’s magnetic field -Birds, bats, whales, others ~Example: detecting natural electrical fields, such as those produced by muscle contractions -Primarily in aquatic animals because water is an excellent conductor -Evolved from mechanoreceptors (lateral line system) -Passive electroreception vs. active electroreception -Electric “echolocation” -Thermoreceptors detect heat or cold and help regulate body temperature by signaling surface and body core temperature -Pain receptors (nociceptors) are a class of naked dendrites in the epidermis Behavior and Social Structures • Behavior -Actions of organisms or systems in response to stimuli (external or internal, subconscious or conscious, voluntary or involuntary -Proximate: questions that have to do with something that is entirely within the life cycle of the individual -Ultimate: questions that have to do with survival and reproduction, and, as a result, evolution, so not entirely within the life cycle of the individual • Tinbergen’s Four Questions -What stimulus elicits the behavior and what physiological mechanisms mediate the response? (proximate) ~Fixed action patterns: an innate behavior that is initiated by a set stimulus and must run to completion once started; “hard-wired” behavior, but they are also influenced by the environment (see textbook figure 51.2) ~Circadian and circannual rhythms: daily, seasonal, or yearly changes in behavior, physiology, etc., typically influenced by light/dark cycles or lunar cycles (tides) -Examples: patterns of activity, migration, reproduction -Correlated with food availability but not driven by food availability ~Communication and Pheromones (see textbook figure 51.6) -Communication: exchanging information between individuals -Most animals use forms of communication -Pheromones: communicate information about the condition of an individual (sexually receptive, hurt, etc.) or influence behavior -How does the animal’s experience during growth and development influence the response? (proximate) ~Learned behaviors: behaviors that are modified by experience -Contrast to innate or instinctive behaviors (such as fixed action patterns) because those are behaviors that can be performed without any prior experience -Nature vs. Nurture ~Nature=genetics/instinct ~Nurture=experience ~Vast majority of behaviors are influenced by nature and nurture ~Imprinting: a long-lasting behavior that is established during a sensitive period early in development; during sensitive periods, animals are more sensitive to particular stimuli than at other times of their life (see textbook figure 51.7) ~Spatial Learning and Cognitive Maps: remembering the spatial structure of an environment and the objects in it -Helps with navigating through landscapes and finding resources, including cached foods ~Associative Learning: learning to make associations between experiences (see textbook figure 51.9) -Classical conditioning: learning to associate an arbitrary stimulus with an outcome -Operant conditioning: trial-and-error learning; learning to associate a behavior with a reward; used to shape behaviors in training -Not all associations are possible; depends on the associations that particular animals are sensitive to ~Cognition and Problem Solving: forming a body of knowledge through awareness, reasoning, recollection, and judgment (see textbook figure 51.10) -Once thought to be restricted to apes and some whales (dolphins), now understood to be widespread; self- awareness is important ~Social Learning: learning through observation of others, typically social group members; social learning forms the roots of culture (see textbook figure 51.11) -Tool use and tool creation, language dialects, predation cultures, play -How does the behavior aid survival and reproduction? (ultimate) ~Mating Behavior and Mate Choice: finding and attracting mates, choosing mates, competing for mates, and caring for young; these behaviors are very important in determining reproductive success -Mating systems are variable (see textbook figure 51.14) ~Monogamous: one male and one female, typically seasonal, rarely lifetime ~Polygamous: one individual mates with many of the other sex -Polygyny: one male mate with multiple females -Polyandry: one female mates with multiple males -Mating systems are influenced by patterns of parental investment and certainty of paternity ~Mammals: obligate female parental investment; males can help to a limited extent; polygyny is common, monogamy is rare ~Birds: males and females can contribute to survival of offspring equally; monogamy is common, polygyny and polyandry are also found ~Internal fertilization: males cannot be certain of their paternity, except for employing tactics to prevent other males from mating with a female (guarding, removing or displacing sperm); low incidence of male parental care ~External fertilization: egg laying and mating occur at the same time, so certainty of paternity can be high; higher incidence of male parental care -Mate choice and male competition shape morphology and behavior ~Females choose males, which drives what males have reproductive success; often factors used in choice are ways of assessing male health or attractiveness -What is the behavior’s evolutionary history? (ultimate) ~Behaviors have a genetic basis and so are heritable (subject to evolutionary change) ~Altruism: behaviors that are apparently selfless (do not directly benefit the individual (see textbook figure 51.25) -Example: eusocial animals, alarm behaviors -Altruism can be explained by inclusive fitness (see textbook figure 51.26) ~Selfish behaviors (like parents sacrificing for offspring) clearly benefit an individual so how can we explain altruism? ~Reciprocal altruism: selfless behavior between individuals that are not related; exceptionally rare, but does occur in species with stable social groups; individuals will encounter each other again through their lives and can reciprocate ~Parasites and behavior: parasites can change the behavior of host organisms to benefit themselves Conservation and Global Change • 1.9 million described species on Earth-many millions undescribed • Current extinction rates are 1000 times higher than average past extinction rates • Countess benefits of biodiversity -Sources of food, medicine, and innovations -Economic services ~UP to $53 billion yearly in savings to agriculture from bat eating pests alone -Ecosystem services • Biodiversity (see textbook figure 56.3) -Genetic diversity: within any species there is significant variation in its underlying genetics; this diversity is distributed different across the distribution of the species; it is insufficient to protect only small parts of populations -Species diversity: richness and endemism -Ecosystem diversity: diversity of species and functions across landscapes • Threats to biodiversity -Overharvesting -Habitat destruction ~Few areas of the Earth are untouched by human modification -Invasive species: non-native species introduced into a new ecosystem where they have negative impacts; often released from natural population regulation in their native ecosystem -Climate change: overwhelming scientific consensus that humans are the cause of current rapid rates of climate change ~Animals must move to suitable areas; rapid rate of change makes that problematic • Protecting biodiversity -Keystone species: a species that has a disproportionately large impact on its ecosystem compared to its abundance ~”Architects” of ecosystems -Umbrella species: species that, when protected in appropriate habitat, indirectly protect large numbers of other species ~Typically require large areas of high quality habitat -Re-wilding ~Cores: well-protected areas ~Carnivores: large predators to maintain diversity and ecosystem function ~Corridors: linking habitats of different levels of disturbance to create large scale corridors and support dispersal
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