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Life 103- week 7

by: Alexis Darling

Life 103- week 7 LIFE 103

Alexis Darling
GPA 4.0

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About this Document

Sensing the environment, behavior and social structures, and diversity
Biology of Organisms-Animals and Plants
Jennifer L Neuwald; Tanya Anne Dewey
Class Notes
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This 4 page Class Notes was uploaded by Alexis Darling on Friday May 6, 2016. The Class Notes belongs to LIFE 103 at Colorado State University taught by Jennifer L Neuwald; Tanya Anne Dewey in Fall 2016. Since its upload, it has received 11 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
Sensing the Environment Sensory pathway: 1. Reception­ need some receptor to detect stimulus (cells, organs, parts of cells) 2. Transduction­ energy from the stimulus changes membrane potential (the difference in charge  between the inside and outside of a cell from active transport and selective permeability) 3. Transmission­ nerve impulse travels toward brain 4. Perception­ brain interprets the transmission ~Action potential­ generated when the intensity of a stimulus is strong enough     ­either on or off     ­does not vary in intensity but in frequency ~Synesthesia­ condition in which the stimulation of one cognitive pathway (vision, hearing, etc)  involuntarily stimulates a second pathway (ex: hear colors, smell music) ~Amplification­ sensory stimuli are magnified during transduction (like hormones’ effect being  multiplied by catalyzing thousands more molecules for each hormone molecule) ­ Either by accessory structures like middle ear bones ­ Or enzyme catalysis of secondary messengers in cells ~Sensory adaptation­ after repeated stimulation, receptors decrease responsiveness Types of receptors: a. Mechanoreceptors­ for mechanical energy such as touch, stretch, motion, sound Ex: Lateral line system in fish­ if hair cells not bent, they have a regular frequency of  action potential, if bent one way they increase the frequency and if bent the other they  decrease the frequency Ex: Mammalian hearing­ Outer ear (pinnae) captures vibration and directs them to  tympanic membrane, which vibrates against the middle ear bones (malleus, incus,  stapes), which transmit the vibrations into the liquid inside the cochlea and hair cells in  the basilar membrane of the cochlea detect the now magnified waves. Passive hearing Ex: Echolocation­ active hearing by producing a signal and detecting the reflected sound.  Ear shape determines what frequency of sound they detect      b. Chemoreceptors­ for chemicals ● Gustation=taste ● Olfaction=smell ● Vomeronasal organ­ detects pheromones      c. Electromagnetic receptors­ for electromagnetic energy such as visible light, electricity, and  magnetism Ex: Photoreceptor­ senses light by photosensitive proteins (visual pigments which are  stimulated by light) Ex: Compound eyes­ many ommatidia (light detectors) on each lens, and each forms an  image Ex: Vertebrate vision­ iris and pupil and lens to focus light on retina which is lined with  photoreceptors. Rods­more sensitive to light in general. Cones­ detect color. Different animals have different ratio of rods to cones depending on their needs  (nocturnal animals have more rods, less cones) Rhodopsin (in rods)= retinal (molecule to absorb light) + opsin (associated protein);  activated by light and changes membrane potential which causes action potential  transduction Ex: Detect magnetic fields­ some tissues contain magnetite crystals which align to the  earth’s magnetic field (in pigeon beaks) Ex: Detect natural electrical fields­ can sense muscle contractions of prey­ primarily in  aquatic animals because water is a good conductor Ex: Electric “echolocation”­ weakly electric fishes put out a weak electric field around  themselves and interpret how it returns to them      d. Thermoreceptors­ for heat/cold      e. Nocireceptors (pain receptors)­ consist of naked dendrites in the epidermis; so they can  respond (reflexes) before pain is registered in the brain Behavior and Social Structures Definition of behavior: “the actions of organisms or systems in response to stimuli, internal or  external, subconscious or conscious, voluntary or involuntary” ~ Inclusive  fitness­  theory by  Haldane to  explain  altruistic  behaviors­  individuals act to  protect the  potential  survival of  the own  genes  (therefore  altruistic  behaviors  are not  really  selfless) ­ ­ Siblings have a coefficient of relatedness of 50% (average percent of  shared genes) ­ Cousins =12.5%                           would give life to save 2 brothers or 8 cousins ~Parasites can change the behavior of host organisms to benefit themselves Ex: Worm eats from the inside of grasshopper then causes the host grasshopper to jump into  body of water to die so that it softens so the worm can get out into a nice wet environment. ­ About 1.9 million species described, many more undescribed on Earth ­ Extinction rates really high right now Benefits of biodiversity:  Sources of food  Medicine  Inspiration for innovations  Economic services (save agriculture by eating pests) Levels of biodiversity:  Genetic diversity­ great variation of genes within each species and between each local  environment  Species diversity­ richness (count up number of species in  each area and compare)                             ­endemism (how unique a species is to a particular place)             ex: species in Madagascar are ONLY found there=endemic species  Ecosystem diversity­ variation of species and functions across landscapes Threats to biodiversity:  Overharvesting/hunting  Habitat destruction  Invasive species (nonnative species that has a negative impact on the new ecosystem)  Climate change Solutions:  Keystone species­ a few organisms of these species greatly supports ecosystem diversity  Umbrella species­ this species indirectly protects a large number of species in a protected  area  Re­wilding –cores­well protected areas ­carnivores­ predators maintain diversity by keeping populations of other  consumers down (ex: sea otters eat the urchins so that there are not too many urchins  destroy all the kelp which they eat) ­corridors­ link cores of different levels of disturbance to allow dispersal of  species


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