Life 103- week 7
Life 103- week 7 LIFE 103
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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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