Exam 2
Discuss what causes a neural membrane to become refractory.
Repolarization/hyperpolarization: refractory period caused by an excess outward flow of ions
Parasympathetic Nervous System
Rest and digest response
Repolarization
Return of the cell to resting state, caused by reentry of potassium into the cell while sodium exits the cell (decrease in membrane potential from efflux of K+)
Double Fertilization (male)
- 2N microsporocytes develop inside pollen sacs in the anthers and each one undergoes meiosis I and II, producing four 1N microspores - Each microspore undergoes mitosis, resulting in a pollen grain containing two 1N sperm cells - Upon landing on stigma, a pollen tube containing 2 sperm cells grows through the style and penetrates the ovules
Describe the fate of the 8 cells in the micropyle.
- 3 1N antipodal cells that dissolve - 2 1N nuclei that fertilizes the future endosperm mother cell - 1 1N egg cell that is fertilized by the sperm - 2 1N synergids that dissolve
Flatworms
- Acoelomate worms lack circulatory and respiratory systems - Nervous system includes longitudinal ventral nerve cords interconnected by nerve fibers that permits coordinated movements during locomotion - Anterior concentration of nervous tissue serves as a primitive brain - Free-living species have eye spots
List the events involved in neurotransmitter release.
- Action potential reaches axon terminal of presynaptic neuron - Ca2+ enters axon terminal - Neurotransmitter released by exocytosis - Neurotransmitter binds to postsynaptic receptor - Ion channel associated with receptor in postsynaptic membrane opens/closes
Describe an action potential, and identify which voltage-gated ion channels are open/closed or activated/inactivated at each stage of an action potential.
- Action potential: basic signaling unit of the nervous system - Membrane at resting potential: both activation gates are closed - Above threshold potential: Na+ activation gates open, causing rapid inward flow of positive charges that raise membrane potential - About 1 msec later, K+ gates open and Na+ inactivation gates close channel on a timer - Membrane above threshold: outward flow of K+ along concentration gradient compensates for inward movement of Na+ ions and causes membrane potential to being to fall - Below threshold potential: Na+ activation gates close, Na+ inactivation gates open, K+ gates remain open - Excess outward flow causes hyperpolarization - Hyperpolarized: Na+ activation gates remain closed, Na+ inactivation gates open and K+ gates close (back to resting potential)
Charles and Francis Darwin (1880)
- Asked what part of the coleoptile senses light by removing the tip, covering the tip with an opaque cap, covering the tip with a transparent cap, and covering the site of curvature by an opaque shield - Determined that the tip sensed the location of light
Venus Fly Traps
- Attract insects with a flower-like reddish color and fruity smell - Have trigger hairs on the modified leaves that sense movement by insects and generate action potentials when bent - When 2 of the trigger hairs are stimulated within a 20 second time period the trap closes and ensnares the insect - Plant secretes digestive enzymes and "eats" the insect
Describe how the acid-growth hypothesis helps explain how auxin causes the bending response of coleoptiles.
- Auxin triggers the pumping of H+ into the cell wall - Activated expansion breaks cross-bridges between cellulose microfibrils (cross-bridges break) - Cellulose microfibrils loosen (cell expansion) - Ultimately increases turgor
Explain why Earth is referred to as a Goldilocks planet.
- Because of its distance from the sun, it has an average surface temperature that isn't too hot or cold (between freezing and boiling points of water) - Gravitational forces are large enough to permit formation of an atmosphere, but not so large that they prevent the evolution of large body sizes and flight
Monoecious Plants
- Both male and female - Each plant produces both reproductive structures
Describe how the water in the xylem facilitates the movement of sucrose into "sink" cells.
- Bulk flow of sucrose from source to sink: sucrose is produced and actively transported to the sieve tubes - Increased sucrose concentration decreases the water potential in sieve tubes, pulling water from xylem vessels - Water influx increases turgor pressure in upper sieve tubes and effectively pushes the sucrose-rich phloem sap down toward the roots - In roots, sucrose is transported out of the sieve tubes into root cells, which lowers turgor pressure, increases water potential, and causes water to flow back into the xylem vessels
Biennial Plants
- Carrot, parsley, onion, shallot - Roots, stems and leaves develop in first season and reproduction occurs in second season with limited secondary growth
Discuss the significance of the casparian strip.
- Casparian strip (water impermeable) forces water and minerals in apoplastic pathway to pass through endodermal cell wall - Without the strip, the plant would have no control over what minerals or other types of chemical flowed into the plant
Flatworms Nervous System
- Cephalization (nerve cells concentrated in one end of the body: the head) where the ganglia constitutes a simple brain that is connected by two longitudinal nerve cords the run the length of the body - Brain and longitudinal nerve cords constitute simple central nervous system that contains interneurons and the conduction of action potentials along neural pathways is one-way with afferent and efferent fibers - Brain integrates inputs from sensory receptors, including a pair of anterior eyespots, and can localize the source of stimuli and generate movements towards or away from the stimuli (eg: intense light)
Explain how electrical or chemical gradients cause molecules to move through membranes against their concentration gradient.
- Chemical gradient: chemical driving force causes molecules to move away from concentrated area - Electrical gradient: electrical driving force causes molecules to move towards the opposite charge
Drupe
- Cherries, peaches, cashews, almonds, pecans - Fleshy fruit with hard, dry seed inside
Describe the pathway that mediates the knee-jerk reflex, and its functional significance.
- Circuits in spinal cord mediate rapid reflexive responses to prevent danger (like falls or burns to our hands) - Tap on the tendon connected to quadriceps muscle initiates reflex, stretch receptors in quadriceps muscle sense sudden stretch of the muscle caused by tap and stimulate afferent neurons, afferent neurons transmit impulses to spinal cord, afferent neurons make excitatory connections with only a single synapse involved to efferent neurons, afferent neurons synapse with inhibitory interneurons in spinal cord, interneurons inhibit efferent neurons that lead to hamstring muscle, excited efferent neurons stimulate flexor muscle to contract, efferent neurons transmit inhibitory signals that keep the extensor muscle from contracting
Indicate how cohesion and adhesion facilitate transpiration.
- Cohesion of water molecules themselves (water molecules attracted to each other and pull other water molecules up with them) - Adhesion of water molecules to wall of vessel elements (water molecules attracted to wall of vessel element)
Explain how the water potential gradient provides the force that pulls water up through the plant body, driving transpiration.
- Cohesion-tension theory: water is pulled up xylem by negative pressure - Water potential becomes increasingly negative as you move up from the soil so water can effectively diffuse from the soil up to the atmosphere
Amphibians
- Most have thin moist skin that is major site of gas exchange (some adults have saclike lungs) - Typically eggs are laid in water - Adults may be aquatic, amphibious or terrestrial, largely dependent on aquatic environments (particularly for reproduction and larval growth)
Distinguish the different types of flow-down gradients.
- Concentration, electrical potential (ions), pressure, temperature - Transport of "stuff" (ions, molecules, blood, and air) is a critical process at all levels of organization in an organism: frequently described by simple diffusion model - Entropy is driving force for diffusion: causes molecules/ions to flow down their own concentration gradient until they reach equilibrium on both sides of a membrane - Capillary walls: osmotic gradient pulls water into capillary and hydrostatic pressure pushes water and dissolved solutes out of a capillary - Neuron membrane: high intracellular K+ concentration can cause efflux of K+ from a neuron and electrical gradient can cause influx of K+ back into the same neuron
Peter Boysen-Jensen (1913)
- Conducted an experiment to determine how the signal for phototropism is transmitted by separating the tip with gelatin (water-permeable barrier) and mica (water-impermeable barrier) - Determined that a water-permeable chemical was released and mediated phototropism
Phloem
- Consists of sieve-tube members that conduct solutes from leaves to other tissues - Sieve-tube members connect end to end, forming a sieve tube, and their perforated end walls are called sieve plates - Specialized companion cells help move sugars in and out of sieve-tube members and may help regulate metabolism - Mature sieve tube members are all alive
Haploid
- Contain one set of chromosomes (1N) - Formed through meiosis - Occur in gametophyte tissues
Dipoloid
- Contain two sets of chromosomes (2N) - Created when haploid cells fuse or when diploid cells undergo mitosis - Occur in sporophyte tissues
Xylem
- Contains stacks of vessel elements and tracheids - Each type of xylem cell connects end-to-end, forming hollow tubes that run throughout the plant body - They convey water and dissolved mineral salts from the roots to the rest of the plant and provide structural support for the plant - Mature vessel element and tracheids are dead cells but still convey water through the plant
Fungi
- Decomposers that break down and absorb biological molecules from dead organisms (includes mushroom-forming fungi and yeasts) - Some mycorrhiza fungi form mutualistic symbioses with plants - Case study involving yeast: high levels of yeast manufactured enough alcohol to make man legally drunk
Intensity
- Defined by action potential firing rate and, in some cases, the types of sensory cells that are stimulated - As intensity of stimulus increases, frequency of action potentials increases
Location
- Defined by source of sensory information - Determined by pattern of stimulation across both sides of the body
Indicate how the Miller-Urey experiments provided evidence for the evolution of life on Earth.
- Devised simple experiment where boiling water produces water vapor and, using a condenser to form water droplets, stimulates the water cycle on early Earth at the bottom and the top contains the primordial soup gasses that stimulates the early Earth's atmosphere to see how they interact and what they produce - Reliable generated the building blocks of complex biological molecules: amino acids, fatty acids, purines and pyrimidines, sugars, phospholipids
Double Fertilization (female)
- Each 2N megasporocyte undergoes meiosis I and II, resulting in four 1N megaspores - Subsequently, three of the megaspores disintegrate and the remaining megaspore undergoes mitosis three times without cell division, resulting in an 8N cell that differentiates into a megaspore - One sperm cell fertilized the egg cell to form the 2N zygote while the other fuses with the two polar nuclei to form the 3N endosperm - Antipodal cells and synergids subsequently degenerate.
Explain how an action potential regenerates itself as it travels down an axon.
- Each firing segment induces adjacent populations of voltage-gated Na+ channels to open, causing the action potential to move along the axon - Propagation of action potentials is self-regenerative
Describe the anatomy of the ear canal, middle ear, and cochlea.
- Ear canal: entrance to the ear - Middle ear: three bones that vibrate to transfer the sound wave - Cochlea: vibrations of the oval window create fluid waves (contains vestibular duct, organ of corti, tympanic duct) - Organ of corti: contains basilar membrane, cilia, auditory nerve, tectorial membrane, outer/inner hair cells
Describe the composition of the "primordial soup" and explain what conditions permitted organic molecules to build up to high concentrations.
- Early Earth's atmosphere consistent of methane (CH4), ammonia (NH3), water vapor (H2O), and hydrogen (H2) - 1920s: Aleksandr Oparin and JBS Haldane proposed that given the abundant energy from UV radiation, lightning and volcanic activity, organic molecules could have formed and these organic molecules would have accumulated to high levels in the oceans because there was no atmospheric O2 or microbes that would have destroyed them - "Primordial soup" of organic molecules (together with abundant energy) could have permitted formation of complex biological molecules
Dioecious Plants
- Either male or female - Each plant produces only male or female reproductive structures
Distinguish between the electrical and chemical driving forces acting on a resting neural membrane, and explain how they contribute to the resting membrane potential.
- Electrical gradient is caused by K+ flowing down concentration gradient through non-gated channels (creates a negative charge inside cell so some K+ is drawn back into the cell) - Concentration gradient force is greater because the inside of the cell is negative
Primary Growth
- Elongation of shoots and roots: enables plant to continuously seek sunlight (shoots) and water (roots) - Shoots and roots elongate by cell divisions in shoot/root apical meristematic tissues and elongation of new cells - Involves apical meristems
Describe the structure and function of the epidermis, and the different epidermal specializations.
- Epidermis: covers the upper and lower surfaces of a leaf - Leaf epidermal cells secrete a protective, waterproof layer (cuticle) composed of waxes embedded in cutin - Trichomes secrete various substances including THC which is released upon contact and deters insect pests - Root hairs develop from root epidermis and collect water and minerals from the soil and convey them to xylem cells - Stomata are pore-like openings that have pairs of crescent-shaped guard cells that allow minerals and products of photosynthesis to pass through the cuticle (open when sunny/humid and close to conserve water)
Describe the structure of the leaf, and distinguish the three different classes of tissue.
- Epidermis: covers the upper and lower surfaces of a leaf - Mesophyll: inside the leaf, rich in chloroplasts - Palisade: vertically elongated, tightly packed cells that are filled with chloroplasts and are the main sight for photosynthesis - Spongy: spaces to allow for gaseous exchange through stomata - Veins: contain vascular tissues that transport minerals in/out of the leaf
Describe how commercial growers use ethylene and gibberellin to manipulate their fruits products in the supermarket.
- Ethylene mediates seed germination, fruit ripening, senescence of flowers/leaves - Fruit shippers have developed massive climate-controlled ripening facilities that provide precise control of temperature and ethylene concentration for 1000s of boxes of bananas - Gibberellin promotes cell divisions, elongation of stems, and development of seeds and fruits so when sprayed on plants, it stimulates growth of flowers/larger fruits
Animals
- Eukaryotic multicellular organisms with cells - Lack cell walls, specialized tissues and organ systems that deliver nutrients to cells and carry away waste - Heterotrophic - Use oxygen to metabolize food - Motile at some time in their lives - Most have sensory and nervous systems that allow them to receive, process and respond to information - Most animals are radially or bilaterally symmetrical (except sponges)
Explain the relationship between the micropyle, fertilized egg, endosperm, and fruit.
- Fertilized micropyle develops into a seed, which is subsequently encased within a fruit structure - A fruit is a mature or ripened ovary, which promotes the dispersal of seeds - The endosperm alone provides nutrients for the seeds.
Describe how fossil fuels were formed.
- Fossil fuels: fuels made from decomposing plants and animals - Sugars, starches and cellulose from plants can be fermented into ethanol - Cellulose from plant cell walls is important source of ethanol for cars - Plant oils are modified to create biodiesel
Describe the modular organization of the cerebral cortex.
- Frontal lobe: coordinates information from other association areas, controls some behaviors - Parietal lobe: sensory information from skin, musculoskeletal system, viscera, and taste buds - Temporal lobe: smell and hearing - Occipital lobe: vision
Outline the experiments that revealed that it is the duration of uninterrupted darkness that determines when some (but not all) plants flower.
- Gave plants different periods of uninterrupted darkness to determine which ones flowered and which ones did not. Ultimately determined that short day plants flower only when the night is longer than a critical night length (16 hrs) - Some plants flower under long-night conditions and others under short-night conditions
Explain what is unusual about the meristematic tissue of grasses.
- Grasses lack apical meristem - Meristem occurs between regions of mature tissue just above ground level and growth occurs at these intercalary meristems
Monocots
- Grasses, irises, cattail, palm trees, corn - Inside seeds, there is one cotyledon - Usually three (or multiples of 3) floral parts - Leaf veins usually running parallel - One pore or furrow in pollen grain surface - Vascular bundles distributed throughout ground tissue, usually branching fibrous root system
Chordates
- Have a notochord that supports embryo from head to tail - Segmental muscles in body wall and tail that allow each muscle block to contract independently - Dorsal hollow nerve cord that forms a central nervous system with anterior ganglion or brain - Perforated pharynx including out-pocketings, perforations or slits in pharynx that occur at some stage of the animals life cycle
Vertebrates
- Have internal skeleton that provides structural support for muscles and protection for nervous system and other organs - The skeleton and muscles attached to it enable them to move rapidly through the environment - Only animals that have bone - Teleosts: most diverse/successful bony fish
Tree Nut
- Hazelnuts, chestnuts, acorns - Dry fruit that consists of a hard shell covering a single seed
Mammals
- High metabolic rate, 4-chambered heart and high pressure circulatory systems permit high rate of O2 delivery to tissues, body temperature, and levels of activity under many conditions - Specializations of jaw, teeth and respiratory system including strong jaw muscles, 4 types of teeth (incisors, canines, premolars, and molars) that permit them to feed efficiently on many different types of food and ability to nose-breath permits them to respire while chewing food - Parental care where mammary glands produce energy-rich milk and in placental mammals, extended development in uterus provides more carefully regulated conditions across development - Complex brain permits higher level information processing and learning relative to other taxa - Marsupial, monotreme, placental
Distinguish between the hormonal response pathways that generate quick versus more delayed responses.
- Hormones that bind to plasma-membrane receptors can initiate a relatively immediate response (eg: activate a proton pump over a period of a sec to a min) - Hormones that bind to internal receptors (in cytosol or nucleus) typically initiate a more delayed response (eg: initiate protein synthesis over a period of hrs to days)
Explain how plant chemistry has been exploited to solve pervasive health problems like malaria.
- Improved nutrients in plants - Protozoan (Plasmodium) causes malaria in humans - Cinchona tree bark contains quinine which kills Plasmodium but Plasmodium is evolving resistance to quinine - Artemisia annua has antimalarial activities: developing Artemisia varieties that produce higher concentrations of artemisinin
Segmented Worms
- Includes earthworms and leeches - Body wall muscles and some organs are divided into similar repeating segments by septa - Complete digestive system and closed circulatory system - No respiratory system (gasses diffuse through the skin) - Excretory system composed of paired metanephridia - Simple brain in the head - Ganglia in every segment - Sensory organs detect chemicals, moisture, light, touch
Mollusks
- Mostly marine - Visceral mass contains digestive, excretory, reproductive systems and heart - Muscular head-foot permits locomotion and escape, mantle may secrete a calcium carbonate shell - Most have open circulatory system (hemolymph/blood in an open cavity that bathes the tissues)
Arthropods
- Includes more than half the animal species on Earth - Segmented body is encased in a rigid exoskeleton periodically shed during molting - Muscles attached to exoskeleton - Three body regions in many but not all (head, thorax, abdomen) - Heart pumps hemolymph through open circulatory system - Gas exchange mechanisms vary by group - Highly organized central nervous system with a wide array of sensory systems
Secondary Growth
- Increase in girth of shoots and roots - Enables plant to increase their strength and create more vascular tissue for water conduction and transport of nutrients - Shoots and roots increase in girth by cell divisions in lateral meristem - Involves lateral meristems (vascular cambium)
Explain why more plants evolved sexual methods of reproduction.
- Increases genetic variation in the offspring by mixing the alleles from both parents so the offspring may have novel and potentially adaptive traits - Provides opportunities for DNA repair (UV light or radiation can damage DNA) because cells can repair some of this DNA damage during meiosis when homologous chromosomes are aligned with one another and they use identical or nearly identical sequence of the homologous chromosome as a template for repairing the break - Permits complementation because in the diploid state, many deleterious and recessive mutations are masked
Contrast the ionic composition of the intracellular and extracellular fluids of a neuron.
- Intracellular fluids are more negatively charged than extracellular fluids because of the efflux of K+ inside the cell - Initially, there is a high intracellular [K+] and high extracellular [Na+]
Sponges
- Lack true tissues - Body consists of cells imbedded in a hydrogel (can be compressed) - Flagellated larvae are released and attached to substrates and undergo metamorphosis into sessile adults - Inner surface lined with flagellated collar cells, filter feeders
Cephalochordata
- Lancelets contain many organs and organ systems that are closely related to those of modern fish but in more primitive form
Be able to distinguish the different types of plants.
- Land plants - Vascular plants - Seed plants - Flowering plants
Explain the Panspermia hypothesis.
- Life forms became trapped in debris ejected into space and survived the journey to Earth - Discovery of extremophiles on Earth: because they can thrive in the harshest environments on Earth, they may survive the journey through space on meteors - Allan Hills 84001: meteorite found in 1984; analysis indicated that it came from Mars ~4 bya when Mars was thought to have liquid water on its surface and some suggested that it contained microscopic fossils of Martian bacteria
Mimosa
- Light touch reduces turgor pressure in the secondary pulvini, while hard touch reduces turgor pressure in the primary and secondary pulvini - Rapid response is mediated by action potentials: mechanoreceptor cells generate action potentials which travel to the pulvini and cause them to lose turgor
Reptiles
- Live in dry habitats because of tough waterproof skin containing keratin and lipids (prevents dehydration) - Amniote eggs that can survive and develop on dry land - Use uric acid as waste product for nitrogen metabolism
Explain how the brain determines which part of the basilar membrane is vibrating in response to a particular frequency of sound.
- Low frequency sounds cause vibrations at distal (far) end and high frequency sounds cause vibrations in proximal (close) region - When vibrations occur in a specific region, the cilia of the inner hair cells in the same region will bend and send neural signals to the brain which provides the brain with a means to distinguish between different frequencies of sound
Discuss the strategies that botanists are using to alleviate hunger and nutritional deficiencies.
- Making plants more drought tolerant: provide a more reliable food supply - Mutation of enhanced drought tolerance1 gene (edt1) can increase plant's tolerance to drought stress - Larger root system (selective breeding for it)
Eudicots
- Maple and oak, roses, sunflowers, garden beans, peas, poppies, cacti - Inside seeds, there are two cotyledons - Usually four/five (or multiples of) floral parts - Leaf veins usually in netlike array - Three pores or furrows (or furrows with pores) in pollen grains - Vascular bundles organized as ring in ground tissue, usually a main taproot with smaller lateral roots
Annual Plants
- Marigold and corn - Growth and reproduction completed in one growing season - Mainly primary growth
Archaea
- Microscopic unicellular organisms that are referred to as extremophiles (inhabit extreme environments) - Some are aerobic and some are anaerobic - Share DNA and RNA organizational features with eukaryotes
Bacteria
- Microscopic unicellular organisms that display incredible metabolic diversity (can be producers, consumers or decomposers) - Some are aerobic and others are anaerobic - Some can move via flagella but most lack motile structures - Live in a diverse range of environments - Microbial biofilms: complex communities of bacteria and fungi that display enhanced resistance to antibiotics and the immune system of humans (ex: dental plaque)
Discuss the lines of support for the endosymbiotic theory.
- Mitochondria originated from aerobic prokaryote and chloroplast originated from photosynthetic prokaryotes - Mitochondria and chloroplasts are similar in size to bacteria - Both organelles divide by process similar to binary fission and contain circular chromosomes that resemble bacterial chromosomes - Both typically contain circular DNA molecules that closely resemble bacterial chromosomes - Both genomes contain codes for ribosomes that resemble those found in bacteria rather than those found in eukaryotes - Both are surrounded by 2 or more membranes, the innermost of which has a chemical composition similar to that of bacterial plasma membrane - Chloroplasts resemble cyanobacteria in their internal structure, including the presence of particular chlorophylls and the existence of thylakoids - DNA sequence analysis indicated that chloroplast DNA most closely resemble extant cyanobacteria DNA
Discuss the different ways that flowering plants reproduce asexually.
- Mother-of-thousands plant: each tiny plant growing from the leaf margin can became a new, independent adult plant - Potatoes: new plants can be created from potatoes or even parts of a potato - Clonal colonies: colonies derived from the same underground rhizome - Grafting: act of aligning vascular cambia of one plant with that of another in such a way that a union will be formed and the partners will continue to grow
Diffusion
- Movement of a substance through an open system/across a membrane - Involved movement of a substance down its concentration gradient, passive process (no ATP required), net movement continues until system reaches dynamic equilibrium
Describe the alternating generations in plants.
- Multicellular gametophyte tissues produce 1N gametes - When sperm and egg fuse they form a 2N zygote - Zygote develops into multicellular embryo within a seed and then into a mature 2N sporophyte - Meiotic divisions in flower of sporophyte produce 1N spores that give rise to new gametophyte generation
Cnidarians and Echinoderms Nervous System
- Nerve nets (networks of neurons) that permit detection of food and objects in the environment via sensory neurons but do not permit localization of the stimulus on the body so animals generate the same motor output irrespective of where a stimulus contacts their body - Lack clearly differentiated dendrites and axons but still generate and conduct action potentials (no brain but nerve cells may be more concentrated in some regions like around mouth)
Discuss why plant oils and biodiesel fuel sources are a promising alternative to traditional fossil fuels.
- New bio-energy crops are under development that can grow on land unsuitable for food production - Carbon in plants can also serve as sources of biorenewable and biodegradable resources which require hydrocarbons - Biodiesel fuels have equivalent energy density to fossil fuels
Roundworms
- Occupy nearly every habitat on Earth - Consume detritus, microorganisms, plants or animals - Some are parasites of plants or animals - Body is cylindrical and tapered at both ends - Covered in a tough, flexible, water-resistant cuticle - Move by alternating muscle contractions - Have an open circulatory system, respiratory system, simple brains, olfactory and touch systems
Describe how secondary growth occurs in the stems of eudicots.
- Ongoing divisions displace the cambial cells, moving them steadily outward even as the core of xylem increases the stem or root thickness - Causes the formation of annual "rings"
Know the parts of a flower.
- Petal - Carpel (female reproductive organs: stigma, style, pollen tube) - Stamen (male reproductive organs: anther, filament) - Sepal - Receptacle - Stem
Explain how sucrose is loaded into phloem cells.
- Photosynthetic cells in leaves are a common source of carbohydrates that must be distributed through a plant - Small, soluble forms of these compounds move from cells into phloem (in leaf vein) - Pumping of H ions out of the cell creates a gradient that drives the transport of sucrose into the cell
Explain how ethylene contributes to autumn foliage changes in deciduous trees.
- Plant senescence is a tightly regulated process of aging in plants. When plants senesce their leaves, they first recycle nitrogen and carbon and transport it to storage organs (revealing underlying pigments) - Leaf senescence is initiated by ethylene (removal of seed pods from soybean plant inhibited ethylene production and delayed leaf senescence) - Ethylene stimulates production of enzymes that digest cell walls in abscission zone at the base of the leaf petiole
List the different mechanisms that plants have evolved for dispersing their pollen.
- Plants lure flying insects to flowers with sugar-rich nectar and when insects contact the stamen, pollen is deposited on their body. When the same insect contacts the stigma of a conspecific flower, pollen is frequently released and may fertilize one of the seeds - Some plants have made their stigma more apparent to insect pollinators that can perceive UV wavelengths of light - Some insects, birds, and bats consume nectar in flowers and as they imbibe the nectar, pollen on the anthers sticks to them so when they visit a second conspecific flower some of the pollen can become dislodged and pollinate the flower - Some plants use abiotic methods to disperse pollen (ex: wind) by releasing pollen into the air (lack bright floral displays to maximize exposure to wind)
Vestibular System
- Provides information about motion, spatial orientation relative to gravity, and balance (senses movement) - Located in ear
Frits Went (1926)
- Removed the tips of the coleoptiles and placed them on agar blocks that he predicted would absorb the signaling chemical and then, under dark conditions, placed the agar block either over the entire tip-less coleoptile or on the left/right side of the tip-less coleoptile - If the chemical (auxin) was sufficient to produce a bending response, it should function independently of light - Determined that chemical was sufficient to produce bending and that it diffused down the coleoptile selectively to cells directly below the source of the chemical.
Discuss the adaptive significance of seed dispersal, and list the different ways that plants disperse their seeds.
- Seed dispersal is important to increase range and diversity of a plant species - Large animals transport "sticky seeds" (ex: burrs) - Water transports buoyant seeds (ex: coconut) - Wind transports fluffy or winged seeds (ex: dandelion and maple) - Exploding dehiscence allows fruit to fling its seeds away (ex: jewelweed)
Compare the functions of the shoot, leaf, vascular and root systems of a plant.
- Shoot system is specialized for photosynthesis and reproduction (stems, leaves, flowers) - Leaf structure and stem positions adapted to maximize light exposure - Vascular tissues conduct water, dissolved minerals, and organic substances - Root system anchors the plant, provides structural support, stores carbohydrates, and absorbs water and dissolved minerals from soil
Cnidarians
- Simplest animals with specialized tissues - Radially symmetrical - Lack organ systems - Diffuse nervous system (nerve net) that enables them to coordinate simple movements - Gastrovascular cavity has a simple opening that serves both digestive and circulatory functions - Gas exchange and excretion occur by diffusion
Explain how the brain discriminates between light and deep touch.
- Skin contains a number of different types of touch-sensitive cells, each of which responds to different qualities of stimulation - Different tactile receptors respond to different types of stimulations
Peanut
- Species of legume - Seeds found in the plant's oblong pods that ripen under the soil
Compare hormonal and neural signaling in terms of their speed of signaling and duration of impact.
- Speed of signaling: endocrine (slow) and neural (fast) - Duration of impact: endocrine (long lasting) and neural (short lived)
Explain how plants benefit from underground starch storage organs, oils, and the phytochemicals that humans extract from them for medicine, spices and perfumes.
- Starch: during harsh times of year, aboveground structures usually die so they use the starch in underground organs to fuel regrowth of new aboveground structures when conditions improve - Essential Oils: attract pollinators, deter herbivores, and prevent attack by mold - Phytochemicals: retard/deter attack from herbivores, mold, and bacteria - Vegetable Oil: oil in seeds helps fuel germination and in fruits attracts seed dispersers
Describe the function of the stomata, and indicate how they open and close.
- Stomata regulates transpiration by opening and closing - Opens when K+ ions enter the guard cells and water follows the K+, which increases turgor pressure and causes guard cells to form a sickle shape - Closes when K+ ions leave the guard cell and water follows the K+, which lowers turgor pressure and causes guard cells to become more linear
Birds
- Strong lightweight skeleton with hollow limb bones - Reduced number of bony elements in wings, skull and vertebral column - Massive flight muscles attach to keeled sternum; flight feathers on wings provide lift - Contour feather features streamline the surface of the body - Down feather form insulating cover close to skin; high metabolic rate provides energy for flight muscles - Use uric acid as waste produce for nitrogen metabolism (uses less water)
Urochordata
- Swimming larvae possess chordate features - Sessile adults secrete a gelatinous or leathery tunic around their bodies and squirt water through siphon - Cilia pull nutrient-laden water into pharynx through incurrent siphon and eject it through the atrial siphon
Perennial Plants
- Trees, woody shrubs, vines, irises, tulips - Growth and reproduction occur year after year - Many species have secondary growth (woody parts)
Explain the relationship between turgidity and hypotonicity in plant cells.
- Turgidity: point at which cell's membrane pushes against the cell wall (high turgor pressure) and occurs when the plant cell is in a hypotonic solution - Hypotonicity: Water flows into the membrane and increases the cells volume
Define turgor pressure and indicate its function importance to plants.
- Turgor pressure provides stability to cells, keeps them fully distended, helps them function normally, keeps stems and leaves erect/fully expanded, provides mechanical support to non-woody tissues - Leave tissues often controlled by loss and gain of turgor pressure
Describe the role of proton pumps in the transport of nutrients across plant cell membranes, using uniporters, symporters or antiporters.
- Uniporters: existing H+ electrical gradient drives positively charged nutrients like NH4+ to the intracellular side of the membrane - Symporters: existing H+ chemical gradient drives cotransport of NO3- or K+ - Antiporters: existing H+ chemical gradient drives the antiport of Na+
Describe how dendrochronology is used to determine the age of archeological sites.
- Use of tree rings for time-keeping
Apoplastic Pathway
- Water moves through nonliving regions (continuous network of adjoining cell walls and tissue air spaces - When it reaches the endodermis, it passes through one layer of living cells (casparian strip)
Symplastic Pathway
- Water passes into and through living cells - After being taken up into root hairs, water diffuses through cytoplasm and passes from one living cell to the next through plasmodesmata
Quality
- Within a given modality, there are different categories of perception - Determined by sensory neurons that are activated
Explain how you can use tree rings to determine the age of a tree.
- Xylem cell diameter changes throughout growing season in temperate areas and spring is favorable for growth, resulting in predominantly large cells - During good years, xylem cells are unusually large which result in thick rings - During bad years, xylem cells are unusually small, resulting in thin rings
Molar equation for photosynthesis.
6CO2 + 6H2O → C6H12O6 (glucose) + 6O2
Indicate what distinguishes plants from other organisms.
Ability to make their own food (photosynthesis)
Polarization
Acquiring polarity
Conformers
Allow internal environment to fluctuate with external environment
Indicate how the presence of "rusty" rocks in the geological record offered definitive evidence for the appearance of life.
Analyzed different ages for oxidized iron, which is red, to quantify oxygen in Earth's early atmosphere (no rocks containing oxidized iron prior to the GOE)
Describe the biological basis for the expression: "One rotten apple spoils the whole barrel."
As climacteric fruits like apples ripen, they release ethylene and the riper they are (up to a point), the more ethylene they release so a ripe fruit can promote ripening of nearby unripe fruits
Explain why K+ efflux is greater than Na+ influx across neural membranes.
Because there are ~40 times more K+ non-gated channels in the neural membrane
Climacteric Fruits
Can be harvested in an unripe state, shipped to a distribution center, and then ripened in presence of ethylene just before delivery
Long-Term Phototropic Responses
Can cause plant parts to grow into well-lit areas (tree branch grows across a small river to exploit a gap in the forest canopy which is an example of tree growth plasticity or "riverside behavior")
Short-Term Phototropic Responses
Can help plant exploit available light by orienting it's photosynthetic tissues towards a light source (plants change orientation of their leaves to exploit incoming sunlight)
Non-Climacteric Fruits
Can only ripen on the plant so they must be harvested and transported immediately to supermarkets
Interneurons
Central nervous system neurons that internally communicate and intervene between the sensory inputs and motor outputs
Corpus Callosum
Connects two hemispheres of the brain
Complete Flowers
Contain both stamens and carpels
Incomplete Flowers
Contain stamens or carpels but noth both
White Matter of the CNS
Contains myelinated axons and functions like interstate highways, permitting rapid communication both within the brain and between the brain, spinal cord and body
Grey Matter of the CNS
Contains neural circuits that do the thinking
Define the Law of Mass Balance.
Contents of any system or compartment in a system is determined by inputs to and outputs from that system or compartment (keeps the system in equilibrium)
Integrators (Negative Feedback System)
Control center that receives information from sensor and initiates steps to correct the environmental change by comparing the detected change with a set point (in most animals, part of brain or endocrine system)
Hypothalamus
Controls body temperature, hunger, thirst, fatigue, sleep, circadian cycles, kidney function, circadian rhythms
Cerebrum
Controls movement, sensory processing, language and communication, learning and memory, seat of consciousness
Rods
Convert light to a gray scale
Modality
Defined by type of sensory cell that is stimulated
Cones
Detect blue, green, or red wavelengths
Characterize the wavelengths of light that you can (and cannot) detect.
Evolved sensitivity to some of the most abundant wavelengths of light (cannot detect gamma, x rays, UV, infrared, microwaves, radio waves)
Phineas Gage
Experienced traumatic brain injury that changed his personality entirely (prefrontal cortex contributes to attention, impulse control, and cognitive flexibility and is not fully developed until the age of ~30)
Sympathetic Nervous System
Fight or flight response
Distinguish between a fruit and vegetable.
Fruit is a botanical term referring to the seed bearing structure of a plant while vegetable is a culinary term for the edible portion of a plant
Describe the adaptive significance of fruits.
Fruits encourage the dispersal of seeds because they are packaged in structures that are sweet and highly palatable
Function and Structure
Function is determined by structure so examining something's structure can give insight into its function
Eukarya
Includes unicellular organisms and all large multicellular organisms
Baroreceptors
Indicate distention (stretch) of internal cavities
Internal Chemoreceptors
Indicate pH, PCO2, PO2 of blood and cerebral spinal fluid
Negative Feedback
Keeps system in homeostasis
Indicate the sources of the oxygen that we breathe.
Land plants and aquatic plants
Patient SM
Lost both of her amygdala which caused her to lose all fear of dangerous situations but retained other emotions
Regulators
Maintain internal environment in relatively constant state despite changes in external environment
Arthropods, Mollusks, Vertebrates Nervous System
Marked increase in: - Cephalization - Ability to generate complex movements - Process a greater diversity of sensory inputs - Make more subtle and adaptive responses to the environment - Cognitive capacity
Pituitary Gland
Master endocrine gland
Fovea
Mediates high-acuity vision (ex: reading, driving, threading a needle)
Peripheral Retina
Mediates side vision and night vision
Threshold Potential
Membrane potential value that activates voltage-gated Na+ activation gates (~70 mV)
Brain's most important job is thinking
Most important job is to run physiological systems without any conscious thought and these actions free up the brain to focus on thinking (constantly monitors and controls internal status like respiration, heart rate, blood pressure, blood CO2 levels, body position, sensory inputs, blood glucose levels, digestion, urine production, etc)
Efferent Neurons
Motor neurons that carry neural impulses away from the central nervous system and towards muscles to cause movement
Osmosis
Movement of water across a semipermeable membrane in response to its own concentration gradient (equilibrium)
Explain why APs propagate more quickly in myelinated (vs unmyelinated) neurons.
Myelin doesn't cover the entire axon, so action potentials can jump from node to node in myelinated axons and fewer are required to reach the end of the axon
Distinguish the 11 organ systems
Nervous, endocrine, muscular, skeletal, integumentary, circulatory, immune, respiratory, digestive, excretory, reproductive
Local Homeostatic Controls
Regulated by mechanisms within an organ (eg: when a specific muscle is working intensely, circulatory system will increase blood flow to it)
Describe the nature and function of a feed-forward (pre-emptive) response mechanism.
Permits organisms to anticipate deviations in homeostasis and reduce the need for negative feedback (ex: flavor of foods elicits variety of pre-absorptive reflexes, joint flexion increases heart rate, drinking water can quench thirst before water is absorbed into the body)
Plants
Photosynthetic multicellular organisms, autotrophic
Discuss why plant (but not animal) cells can tolerate hypotonicity.
Plant cells can tolerate the expansion of the cell by water because of the central vacuole while animal cells cannot
Cerebellum
Plays important role in equilibrium, posture, motor learning
Positive Feedback
Pushes a system out of homeostasis and functions to generate a maximal response
Systemic Homeostatic Controls
Regulated by chamisms in the brain (eg: when blood pressure drops, body will increase heart rate and tension in arteries)
Pons and Medulla Oblongata
Regulates cardiac and respiratory function, consciousness and the sleep cycle; integrates sensory input
Mechanistic Explanations
Seeks insight into components, processes, and proximate causal mechanisms underlying a phenomenon (how)
Functional Explanations
Seeks insight into the function, goal or purpose of a phenomenon (why)
Afferent Neurons
Sensory neurons that carry nerve impulses from sensory stimuli towards the central nervous system and brain
Cartilaginous Fish
Skeletons composed entirely of cartilage
Outline the four steps (proposed by Oparin and Haldane) to explain the origin of the "protobiont."
Step 1: formation of simple molecules that constituted the building blocks of more complex polymers Step 2: formation of polymers that stored information and catalyzed reactions Step 3: once a membrane enclosed the proteins and nucleic acids, it would have constituted a primitive protobiont Step 4: formation of self-replicating molecules like RNA would have permitted inheritance of adaptive characters and natural selection Evidence: step 1 is to assemble building blocks for complex polymers (established plausible by Miller and Urey), step 2 is to polymerize the building blocks (assembly of larger molecules), step 3 is to assemble membranes (phospholipids suspended in water self-assemble into bilayered microspheres), step 4 is to develop self-replication molecules in protobionts
Discuss how the stiffness of the basilar membrane (and hence sensitivity to sound frequencies) changes along its length.
Stiffness of the basilar membrane changes along its length so different frequencies vibrate different parts of the membrane
Proprioception
Stretch receptors in our muscles and joints that permit us to control our movements, keep track of where our body is in space, sense muscle force and effort, maintain balance (activated by movement)
Describe how the relationship between irradiance level and photosynthetic rate differs depending on whether leaves develop under sunny versus shady conditions.
Sun leaves display higher potential rate of photosynthesis while shade leaves are more efficient at harvesting sunlight under low light conditions
Effectors (Negative Feedback System)
System(s) activated by integrator to return the condition to the set point (may include parts of any body tissue or organ)
Tonicity
The ability of a solution surrounding a cell to cause that cell to gain or lose water.
Hyperpolarization
The movement of the membrane potential of a cell away from rest potential in a more negative direction (over compensation to reach resting potential)
Depolarization
The process during the action potential when sodium is rushing into the cell causing the interior to become more positive (rise in membrane potential from influx of Na+)
Young people have learned how to multitask effectively
When people multitask, they are actually switching back and forth between different tasks so error rate increases by ~50% and they take twice as long to do things
Sensors (Negative Feedback System)
Tissue or organ that detects a change in factors subject to homeostatic control like pH or temperature
Explain the following quote: "For life to exist, it must overcome entropy."
Universe seeks to maximize entropy (disperse energy and disrupt any form of organization including life itself) so animals overcome entropy by consuming energy from food sources
Humans typically use only 10% of their brain
Use nearly 100% of your brain at all times throughout the day (to varying degrees)
Summarize the two mechanisms that tomato plants use to defend themselves against caterpillars.
When tomato plants are attacked by caterpillars, they produce chemicals that both disrupt the caterpillar's digestion and attract wasps
~4 bya
Widespread volcanic activity is thought to have released large amounts of water and smaller quantities of other gasses into the atmosphere (as Earth cooled, water vapor condensed into clouds, fell to the surface, and accumulated to form the oceans)
~500 mya
eukaryotes evolved
~3.5 bya
life appeared; origin of cellular life is very mysterious but probably included development of protocells (primitive cell-like structures that have some of the properties of life) - Two main carbon isotopes: 99% C12 and 1% C13 - Bacteria preferentially take up C12 and increases the C12:C13 ratio above 99:1 so C12 enrichment (higher ratio) in sedimentary rocks is interpreted as evidence of presence of living organisms - 3.5 bya Isua Formation in Greenland consists of metamorphosed sediments that are enriched in C12, but cannot reject the possibility that enriched C12 stems from abiotic processes
~2.3 bya
more definitive evidence for life through fossilized cyanobacteria (photosynthetic bacteria that appeared on Earth ~200 million years before O2 started accumulating in the atmosphere) and evidence for the great oxidation event (life before GOE was anaerobic); organisms similar to modern-day cyanobacteria evolved
Describe the timeline of the Great Oxygen Event and discuss the role of cyanobacteria.
~2.5 bya: O2 was produced but most absorbed in oceans and seabed rock ~2-1 bya: O2 starts leaving oceans but most absorbed by land surfaces and growing ozone layer ~1-0 bya: once O2 saturated the organic and inorganic matter, it started to accumulate in the atmosphere - Photosynthesis is the only natural source of oxygen on Earth and only photosynthesizers at the time were cyanobacteria so it follows that a rise in atmospheric O2 must stem from the emergence of cyanobacteria - Cyanobacteria: extra-terrestrial origin that originated from nonliving matter on Earth
