BIO 161 Midterm 2

Make a table to organize information about how abscisic acid (ABA) influences stomatal aperture and water loss. The column headings are: *

Access to water: closes stomata to respond to water stress ABA present/absent: growth stops when ABA is not present Ion movement: deactivates ion movement into cells guard cell turgor pressure: ABA changes turgor pressure in guard cells to stop ion movement, trigger stomata to close Stomata (open/closed): ABA causes stomata to close

As shown below, fish gills use countercurrent exchange, with blood and water flowing in opposite directions; bird lungs use crosscurrent exchange, with blood flowing perpendicular to air; and mammals have an open pool model, in which there is no set direction between blood and air flow. Predict the relative efficiency of these flow patterns for respiration.

Countercurrent > Crosscurrent > Open pool

Diagram the steps in which rhizobia colonize a root. (flavonoid, infection thread, cytoplasm, nodule, cell division)*

1. Sugar is released from roots to attract rhizobium 2. Rhizobium release nod factors (molecules that signal to the root that it wants to be taken up) 3. Rhizobium proliferate/increase inside to root hair 4. Rhizobium enters into the root cortex through the root hair plasma membrane

What is the primary function of roots? What other functions can modified roots serve?*

• The primary function of roots is to anchor the plant to the ground and transport water/nutrients from the soil to the plant's shoot. • Modified roots such as adventitious roots can hold the plant to other surfaces and provide support against wind as the roots develop from the shoot system. Pneumatophores are another modified root, allowing for gas exchange when oxygen diffuses through aerial roots if part of the plant is submerged in an area of low oxygen concentration. Storage roots are formed from a large taproot and can store carbohydrates that provide energy for the plant's reproductive process.

What is the primary function of shoots? What other functions can modified shoots serve?*

• The primary function of shoots is to allow for light and carbon dioxide to be absorbed in different places on the plant body, which results in photosynthesis. • Modified shoots such as cactus stems are able to store large amounts of water. Stolons and rhizomes are two other types of modified shoots that grow horizontal along the ground (underground for rhizomes), which allows for asexual reproduction because a new plant forms at the shoot's nodes. Tubers function underground as shoots, storing large amounts of carbohydrates, and thorns can protect the plant against herbivores.

Articulate the important concept illustrated in figure 34.7 (genes, environment, plasticity)*

• This figure is an example of phenotypic plasticity because the leaves came from the same tree, but they differ in size due to their different environmental conditions. • The leaf from the plant grown in the shade is thinner and larger because of the need to absorb as much light as possible through its leaves. Even though the leaves are larger which can cause high transpiration, this is less of an issue for the plant because of the cool environment. • The leaf from the plant grown in the sun is thicker with a smaller surface area to reduce the amount of transpiration when it is difficult to replenish H2O in such a hot environment. The leaf also doesn't need to be as large because light isn't as much as an issue, so it doesn't need to increase its surface area to absorb more light.

Describe how cells are organized into tissues, organs, and systems of organs within an animal. *

• Tissues are organized into organs with epithelial tissue on the outside, then connective, nervous, and muscle tissue. • Systems of organs are organized by different connected organs and chambers to perform functions.

Describe how the insect tracheal system delivers oxygen through the body (spiracles, tracheae, diffusion, bulk flow).

• Tracheae connects to spiracles (holes in the insect's exoskeleton) that are highly branched at the ends and open/close to allow for bulk flow of air to pass through or minimize water loss • Tracheae is alternatively compressed so that contractions change the partial pressure within the insect's body to increase/decrease diffusion rate • When muscles are stimulated, gases move by diffusion rather than through the insect's tracheal system • Larger tracheae in some larger insects decrease resistance to air flow and allow diffusion rate to increase

Compare and contrast the causes, prevalence, and treatments of type I and type II diabetes mellitus. *

• Type I (early-onset): pancreas stops producing insulin, resulting in high blood sugar ◦ Treatment: insulin injections • Type II (late-onset): cells don't respond to insulin due to other causes of high blood sugar ◦ Treatment: diet, exercise, drugs

Describe the four steps by which oxygen moves from the environment to cells in the body and carbon dioxide moves from cells to the environment (convection, bulk flow, diffusion).

• Ventilation: movement of the respiratory medium (air/water) over the respiratory surface (lung/gill) ◦ Convection (bulk flow of a fluid from one place to another) ◦ Part of respiratory system • Gas exchange: movement of oxygen from air/water into the blood; movement of CO2 from the blood into the air/water ◦ Diffusion (movement of individual gas molecules) ◦ Part of respiratory system • Circulation: process of moving gases/nutrients around the body ◦ Convection ◦ Part of circulatory system • Cellular respiration: drives the metabolic rate by the rate of the use of O2 and production of CO2 ◦ Gas exchange occurs when there are low levels of O2 and high levels of CO2 ◦ Diffusion

Water flows from cell A into cell B. How do the water potentials (ψ) of these two cells differ (which is higher)?

• Water flows from a region of high water potential to a region of low water potential • Cell B has a lower water potential than cell A

Explain the relationship between wilting and turgor pressure.

• When a plant loses water faster than it is being absorbed (usually in hot/dry conditions when the plant's stomata is open), the positive turgor pressure from the roots is reduced. Reduced turgor pressure makes it unable for the plant to push water up through the xylem, which causes the plant to dehydrate or wilt.

How does leaf senescence benefit a plant? (nutrients, recycling)

• When leaf senescence occurs, the cells in the abscission zone (attaching the leaf to the stem) die and the leaf falls off the plant. • The nutrients from the leaf can provide NO3- to the soil and be used in the plant's roots to recycle NH4.

How does the current atmosphere differ from that in which photosynthesis evolved? (O2, CO2) How does the current Earth atmosphere reduce the efficiency of rubisco? (photorespiration)

• When photosynthesis evolved 3.5 billion years ago, there were higher levels of CO2 than O2 in the atmosphere, so when rubisco evolved there wasn't a selectivity for CO2. • Now 20% of gas in the atmosphere is O2 and 0.05% is CO2, so since photosynthesis evolved there has been a huge decrease in CO2 (slight increase in recent years) and increase in O2. • The efficiency of rubisco is reduced in the current atmosphere because rubisco doesn't have a selectivity for CO2, so O2 and CO2 compete for active sites on the enzyme. If rubisco uses O2 as a substrate to catalyze RuBP due to increased concentrations of the molecule inside the leaf, photorespiration occurs and there is a loss of fixed carbon and energy.

Describe the role of antidiuretic hormone in the formation of concentrated urine in mammals (blood pressure, hypothalamus, hormone, aquaporin).

• When you're dehydrated, the ADH hormone is released from the hypothalamus to reduce water loss by producing concentrated urine. ADH triggers aquaporins in the collecting duct of the nephron, which allows water to cross its membrane via facilitated diffusion with the aquaporins.

Briefly summarize the Wood Wide Web hypothesis and site evidence (from lecture or on-line) that supports the idea of the Wood Wide Web. (fungi, carbohydrates)

• Wood Wide Web Hypothesis: there are permanent fungi underground that interact with tree roots and create a mutualistic relationship for the exchange of carbohydrates

Identify the three zones of the root. In which zone does most nutrient uptake occur? How is the structure of this zone specialized for this function?* (root hairs)

• Zone of cell differentiation, zone of cell elongation, zone of maturation • Nutrient uptake occurs in the zone of maturation which located directly after the root cap and includes root hairs. • Root hairs are specialized for nutrient absorption with a high surface area, thin cell walls for absorption, and membranes with pumps/channels for active transport/facilitated diffusion

Mammals that have evolved at high altitude, such as llamas, have left-shifted hemoglobins compared to related species that occur at lower altitude. Which statement is correct?

Llama hemoglobins have adapted to enhance oxygen uptake in the lung. A left shift increases the oxygen affinity of hemoglobin, enhancing its ability to load oxygen at lower partial pressures.

State a hypothesis to explain why giant insects existed 300 million years ago, but could not survive today. *

• 300 million years ago, there were higher concentrations of oxygen than there is today (today only 20% of gas in the atmosphere is O2), which led to a large difference in the partial pressure between the atmosphere and the insect. This likely led to the evolution of large tracheal tubes because of the increased diffusion rates from the large difference in partial pressure. Now the atmospheric O2 percentage is much lower which decreased the difference in partial pressure in insects and decreased their overall diffusion rate, so large tracheal tubes and a larger body size weren't supported by the atmospheric conditions.

Describe an experiment you could do to determine the role of auxin in establishing apical dominance (Hint: you will do this in lab).

• A possible experiment would be to remove the tip of plants where light is perceived, then compare two plants (one treated with auxin and without at the tip of the plant). The two plants can be compared with growth from their apical meristem and axillary meristems.

Describe the difference between adaptation and acclimatization/acclimation. (population, individual, genes, time, evolution, mutation, selection).

• Acclimatization: phenotype differences that occur in the natural world due to different environmental conditions • Acclimation: phenotype differences that occur in a lab setting due to different mimicked environmental conditions • Acclimatization and acclimation result in different phenotype differences of an individual from the same species as two types of phenotypic plasticity. Adaption is long-term and results from a mutation of an individual that is naturally selection and passes this trait on to its offspring through evolution. Acclimatization/acclimation is the individual's short-term response to its environmental conditions and it occurs within the individual's lifetime while an adaption occurs over a long period of time.

Explain the acid-growth hypothesis (auxin, H+ pump, turgor pressure, expansin). How does acid-growth relate to phototropism?

• Acid-growth hypothesis: when auxin is pumped into the cell, it causes a proton pump to move from the cytoplasm to the plasma membrane of the cell, pumping protons into the cell wall. As protons are pumped into the cell wall, it decreases the pH and causes the cell wall to be more acidic. • Ions are likely pumped into the cell as protons are pumped outwards, causing the concentration of solutes to increase in the cell which lowers its water potential. As water moves towards the area of lower water potential, it causes turgor pressure as cytoplasm of the cell tries to expand. • Expansion proteins are secreted from the cell as the cell wall becomes more acidic, which cute hemicellulose and allow for cellulose microfibrils to expand away from each other. As cellulose microfibrils are no longer as attached as before, the cell wall expands in response to the turgor pressure.

Define an adaptation (trait, natural selection, survival, reproduction).

• Adaptation: evolution by natural selection; individuals with valuable, heritable traits in an environment are more likely to survive and reproduce to pass that trait along to their offspring • Increases ability to reproduce other individuals with that trait and pass it along as the frequency of those alleles increases in future generations

What are the advantages and disadvantages to a plant of OPENING stomata? And of CLOSING stomata?

• Advantages of OPENING stomata: allows for diffusion of CO2 into the leaf and O2 into the atmosphere, maintains high levels of CO2 and low levels of O2 within the leaf to allow for photosynthesis and prevent the loss of fixed carbon in photorespiration • Disadvantages of OPENING stomata: water is lost to the environment through transpiration • Advantages of CLOSING stomata: limits water lost from the plant to the environment when conditions are dry • Disadvantages of CLOSING stomata: O2 levels increase and CO2 levels decrease, results in photorespiration (rubisco uses O2 as a substrate), energy in the form of ATP is used up and fixed carbon is lost to the environment

The presence of clay in soil provides both nutritional challenges and advantages for plants. What are the challenges? What are the advantages? (nutrients, cations, leaching)

• Advantages: cations are attracted to clay since it is negatively charged which prevents them from washing away; H+ can be pumped out of root hairs for cation exchange, so H+ is attracted to clay and other cations in the soil are absorbed into the root hairs as nutrients for the plant • Disadvantages: limits the plant's access to positively charged nutrients; if cation exchange occurs between clay/root hair during heavy rain, then leaching occurs and cations are lost

Leaves have a higher SA/V (surface-area-to-volume) ratio than other structures in the plant. What are the benefits and costs to the plants? (water, photosynthesis, gas exchange)*

• Advantages: more surface area to absorb light which allows for rapid light reactions and photosynthesis, more surface area for gas exchange (CO2 entering into the leaves) which allows for efficient photosynthesis • Disadvantages: more surface area for transpiration

Give examples of some events that occur "downstream" of a receptor protein. (phosphorylation, gene expression, membrane permeability, export, cascade)*

• After a receptor protein changes shape for in response to the external signal, it catalyzes a phosphorylation reaction after a phosphate group from the protein is transferred from ATP. • A phosphorylation cascade of other proteins within the cell starts after the initial protein is phosphorylated, resulting in a phosphate group. • The phosphorylated receptor protein might also trigger the release of a second messenger for the cell's vacuole. • The phosphorylated proteins or second messengers either activate/repress transcription of DNA in the nucleus, change membrane permeability, or activate/repress translation.

Identify the three main types of nitrogenous wastes produced by animals, and give examples of animals that produce each type. *

• Ammonia: low energy cost, high toxicity, diffuses into aquatic environment either through gills (freshwater/marine bony fishes) or urine (freshwater fish), breakdown of amino acids and nucleic acids ◦ most fish and aquatic animals • Urea: medium energy cost, medium toxicity, ammonia/amino groups are synthesized in liver ◦ Mammals, amphibians, sharks, some bony fish • Uric acid: high energy cost, low toxicity, not very soluble in water compared to ammonia, releases excess nitrogen without losing a lot of water ◦ Birds, reptiles, insects, snails

Identify the costs and benefits of each type of nitrogenous waste (ATP, water, solubility, toxicity).

• Ammonia: low energy cost, high toxicity, high solubility, high water loss • Urea: medium energy cost, medium toxicity, medium solubility, medium water loss • Uric acid: high energy cost, low toxicity, low solubility, low water loss

Compare the anatomy of xylem (vessel elements, pits) and phloem (sieve tubes, cytoplasm, plates).

• Anatomy of the phloem ◦ Sieve tubes: alive at maturity; lack a nucleus, mitochondria, and protein synthesis; connect to each other with sieve plates that allow sap to pass through, connect to other cells with plasmodesmata from their cytoplasm ◦ Companion cells: every sieve tube cell is linked to a companion cell to support it (plasmodesmata); contains a nucleus, mitochondria, and protein synthesis • Anatomy of the xylem ◦ Vessel elements: allow for water to be easily conducted through the cells; perpetrations between vessel elements and pits on the outer walls of the cells for water transport

Explain the relationship between these terms: apical meristem, axillary meristem, branching.

• Apical meristem: meristem cells at end of the plant shoot/root, lengthen the plant vertically through mitosis and cell differentiation (primary growth) • Axillary meristem: pockets of meristem cells that have potential to add new on new structures to the plant through nodes • Branching: cells from axillary meristem differentiate to lengthen the plant horizontally

Compare apoplastic, transmembrane, and symplastic transport of water. Explain how the casparian strip of the endodermis promotes "filtering" of water that reaches the vascular tissue. (suberin, plasma membrane, plasmodesmata)*

• Apoplastic transport: water transport outside of the plasma membrane; inside porous cell walls and between cells • Transmembrane transport: water transport through the plasma membrane with the assistance of aquaporin proteins • Symplastic transport: water transport through cell walls that occurs in the plasma membrane by the plasmodesmata • Casparian strip: contains suberin and acts as a wax to prevent endodermal cells to touch eachother, controls where water can enter the cell

What are the major structural components of the cell wall and how are they organized? (cellulose microfibrils, hemicellulose)

• Cellulose microfibrils: strands of cellulose that create structure to cell wall • Hemicellulose: sugar molecules that makes bonds to cellulose microfibrils to tie them together and create elasticity in the cell wall • On the interior of the cell wall, the plasma membrane holds proteins and proton pumps, one of which synthesizes B glucose into strands of cellulose that weave together to form cellulose microfibrils.

Review the structure of the chloroplast and know where the light reaction and the Calvin cycle take place.

• Chlorplasts contain an inner and outer membrane. • Stroma: liquid matrix within the inner membrane • Thylakoid membrane: sac structure throughout the chloroplast, connecting to create a granum (grana if plural) • Lumen: the space inside of the thylakoid membranes • Pigments (mostly chlorophyll) are found in the thylakoid of chloroplasts. • Light reactions occur in the thylakoid lumen and the Calvin Cycle occurs in the stroma.

Explain how the presence of chyme in the digestive tract leads to the release of enzymes from the pancreas and bile from the liver, including the relevant hormones and the organs that release them. *

• Cholecystokinin as a hormone stimulates the release of bile from the gallbladder into the small intestine. • Chyme in the digestive tract activated the release of bile from the liver as its hydrophilic properties are attracted to larger triglycerides in it.

Describe how steroid hormones are produced from cholesterol, focusing on the example of estrogen production (enzymes, aromatase).

• Cholesterol binds to the cholesterol side-chain cleavage enzyme, forming pregnenolone that eventually becomes a sex hormone through enzyme canalization. The enzyme aromatase catalyzes an aromatic ring on androgen to form estrogen. • Steroid hormones diffuse through the plasma membrane and bind to intracellular receptors and hormone receptor complexes, entering the nucleus to modify transcription and change gene expression within the cell.

Why do the sieve elements of the phloem require companion cells? Why DON'T the tracheids and vessel elements of the xylem require companion cells? (Note: these cell types will be covered in more detail later.)*

• Companion cells maintain the plasma membrane and cytoplasm of the sieve-tube elements, supporting their overall metabolic activity. • Tracheids and vessel elements conduct water throughout the plant while sieve-tube elements and companion cells transport sugars through the cytoplasm (plasmodesmata)

Explain the advantages of a complete digestive system vs. an incomplete digestive system (specialization, batch vs. continuous flow).

• Complete digestive system: gastrointestinal tube is continuous from mouth to anus with specialized organs ◦ Advantages: digestion and excretion can happen independently and continously • Incomplete digestive system: alternates between digestion and excretion (batch flow) with only one opening so there is less specialization (food/waste passes the same cells) ◦ Advantages: simpler cavity

Describe the pathways for heat exchange between animals and their environments and explain how countercurrent heat exchangers minimize heat loss (conduction, convection, radiation, evaporation, thermal gradient, surface area). *

• Conduction: heat transfer between body and solid material • Convection: heat transfer between body and moving fluid (ex. Water) • Radiation: heat transfer via electromagnetic radiation (ex. sun) • Evaporation: heat transfer by changing water from liquid to gas (ex. panting, sweating) • Countercurrent heat exchangers: a structural component of an animal that allows for minimum heat loss when there is a thermal gradient formed by two liquids flowing in opposite directions

Make a list of the costs and benefits to the plant of symbiosis with rhizobium.

• Costs: requires sugar to feed rhizobium, special structure to house rhizobium (nodules), gene products to help rhizobium (leghemobiobin to bind to O2) • Benefits: access to N2 to convert into NH4+ for the plant's nitrogen metabolism

Be familiar with the classic experiments that established that phototropism results from the unequal distribution of a hormone (auxin) in the stem. Explain what insight is gained from each experiment described on pages 789-790.*

• Darwin (1987): 4 stems with light coming in from the left side (control, tip removed, tip covered, lower portion of coleoptile covered), so that only the control and lower portion of coleoptile covered bent towards the light ◦ The experiment determined that sensing tissue is located at the tip, hormonal signals pass down the stem, and responding tissue causes the stem to bend towards the light. • Fris Went (Fig 37.6): auxin was infused into an agar gell and then placed slightly off one side of two stems, causing the stem to elongate on the side that the hormone had been placed

Explain how peristalsis moves chyme through the digestive tract. *

• Digested food interacts with the HCl in the acidic environment of the stomach. • Peristalsis allows the stomach to use muscular movements to contract above the chyme and relax below it in order to push it through the digestive system. • Chyme enters the small intestine from the stomach where it interacts with bile for further digestion of lipids and nutrients are absorbed into the blood, moving on to the large intestine and then is excreted out of the body as feces.

Give examples of how hormones are involved in normal development.*

• Dopamine: inhibits prolactin • Thyroid hormone: regulates metabolism, stimulates protein turnover • Growth hormones (GH): secreted by the anterior pituitary, controls growth of tissues • Oxytocin hormone: controls milk for nursing • Androgens/estrogens/progestins: gamete development and sex steroid production • Peptide hormones: regulates insulin levels

Define endocrine disruption and give examples of major endocrine disrupting chemicals in the environment.*

• Endocrine disruption: environmental disruption that blocks the receptor to a hormone ◦ Pesticides

Compare and contrast endothermy vs. ectothermy and homeothermy vs. poikilothermy. Are endotherms most commonly homeotherms or poikilotherms? What physiological mechanisms do they use to achieve this? (metabolic rate, metabolic heat production, conductance, behavioral thermoregulation)

• Endotherms: heat is obtained from inner metabolic processes • Ectotherms: heat is obtained from the environment • Homeotherms: body temperature is stable over time • Poikilotherms: body temperature conforms to the environment • Endotherms are more commonly homeotherms because their high metabolic rate and inner metabolic heat production allows their body temperature to stay stable. Since they aren't using the environment for heat, it is rare in animals for their body temperature to conform to the environment.

Describe the interior of a typical leaf. How do gasses move from the atmosphere to the chloroplast? (air space, mesophyll, stomata, diffusion)

• Epidermal cells: surround the leaf, hydrophobic, secrete wax • Mesophyll cells: interior of the leaf, surrounded by air space containing CO2 and O2 • Stromata: openings/pore between epidermal cells surrounded by 2 guard cells that can open/close to allow for gas exchange and allow/prevent water loss • CO2 moves into the leaf and O2 leaves out into the atmosphere by diffusion through the stroma.

What do epiphytes, parasitic plants and carnivorous plants have in common? How do they differ?*

• Epiphytes, parasitic, and carnivorous plants all obtain nutrients from another source rather than the soil • Parasitic: obtain nutrients from a host plant or lives within a host plant ◦ Some tap into the vascular tissue of the host plant • Epiphytes: non-parasitic, grow on other plant's roots/trunks and their leaves hold water/nutrients that they absorb from rain, dust, particles • Carnivorous: obtain nutrients from animals by trapping them

Access to water; ABA present/absent; ion movement; guard cell turgor pressure; stomata (open/closed) 15) What is unique about the hormone ethylene? What are some aspects of plant development influenced by ethylene?*

• Ethylene has a different impact on different types of plants. • Triggers leaf senescence, fruit ripening, and flower development

Define Fick's law, describe how it relates to the structure of respiratory surfaces (e.g., tracheae, lungs, gills), and apply its principles to exchange across other surfaces (area, distance, partial pressure gradient).

• Fick's law: rate of diffusion = K x A x (P2-P1)/D ◦ K = solubility of gas ◦ A = surface area for gas exchange ◦ P2-P1 = partial pressure of gas on either side of the diffusion barrier ◦ D = distance that gas has to travel, thickness of the diffusion barrier • K, A, and partial pressure is proportional to rate of diffusion and the distance gas has to travel is inversely related ◦ By increasing the solubility of the gas, surface area for gas exchange, or partial pressure difference, the rate of diffusion increases ◦ By decreasing the distance gas has to travel and the thickness of the diffusion barrier, the rate of diffusion increases • Gills: large surface area (K) and thin epithelium (D), direct contact with respiratory medium with thin gill lamellae, gases move from high partial pressure in the seawater to low partial pressure in the body • Tracheae: connect to openings in the animal's exoskeleton, highly branched, large in diameter, volume of tracheal system can compress and cause the partial pressure difference to increase (P2-P1) to increase diffusion rate • Lungs: alveolar gas exchange surface is very small, branching to maximize SA (K), O2 doesn't have to travel very far to get to a red blood cell (D) to increase diffusion rate

Identify 6 major parts of the mammalian nephron and describe the major types of active and passive transport that occur at each location to produce small quantities of concentrated urine (filtration, reabsorption, secretion, excretion).

• Filtration (renal corpuscle): water/small solutes across a the semi-permeable membrane into the Bowman's space; blood remains in the capillaries while the water/small solutes continue on into the nephron • Bulk reabsorption (proximal tube): reabsorb glucose, H20, and Na+, active transport of Na+ that creates a concentration gradient that moves ions and nutrients against their concentration gradient and can be diffused into blood, water moves into blood from osmosis • Osmotic gradient (loop of Henle): establishes/maintains a concentration gradient in the tissues of the renal medulla, increases the osmolarity as you go deeper in the tissues, reabsorption of water in the collecting duct ◦ descending limb (more concentrated surrounding tissues), thin ascending limb (decrease osmolarity, increase diffusion), thick ascending limb (active transport of Na+ and Cl- that maintains the concentration gradient) ◦ Vasa recta: surrounding tissue of the nephron that contains blood flowing in the opposite direction (capillaries reabsorb water but not salt) • Regulated reabsorption (distal tube) ◦ aldosterone is released of Na+ is low and it is reabsorbed in the distal tube • Water reabsorption (collecting duct) ◦ ADH is present: cells of the collecting duct produce aquaporins, water channels allow water to cross the membrane via facilitated diffusion, small volume of concentrated urine is released ◦ ADH is not present: cells don't express aquaporins and collecting duct is not permeable to water, large volume of dilute urine ◦ ADH is released if you are dehydrated (less water is lost in urine)

Define a fitness trade-off. Work through and be able to interpret the experiment on cricket trade-offs. *

• Fitness trade-off: a compromise for when an animal invests energy in an adaptation, there is another trait that isn't as developed as maybe was before • In the experiment on cricket trade-offs, the adaption is that male crickets developed to produce larger spermatophores over time. If a male cricket transfers a larger spermatophore over to a female, it will take her a longer time to eat it which correlated to a larger amount of her eggs that are fertilized. By measuring the lytic activity (amount of enzymes produced from previous viral infections) in the male crickets, the results showed that there was a lower amount of activity in crickets that removed spermatophores daily compared to crickets that removed none. In the second part of the experiment, lipopolysaccharide to simulate a bacterial infection was inserted into the same two types of crickets, showing that the crickets that produced more spermatophores were now producing smaller ones. This experiment shows that the fitness tradeoff for crickets producing larger spermatophores is the ability to fight off bacteria/infections.

Give examples of how some structures are modified into shapes that alter surface area to volume ratio (folding, flattening, branching). *

• Flattening: gill lamellae (very flat for a low SA-V ratio) that allow for gas exchange between the water and fish • Folding: intestinal folds and villi (folded for a low SA-V ratio) that allow for nutrient absorption and diffusion • Branching: capillaries (small & thin walled for a low SA-V ratio) that allow for gas, nutrients, waste to diffuse in and out of blood

What is the role of gibberellins in determining plant height? (internode) (Note: the role of GA in seed germination will be covered in a later lecture on plant reproduction.)

• Gibberellins: produces A-amylase, promotes cell elongation and cell division in the internode section of plants compared to plants without gibberellins

How is gravity sensed in roots? How does gravity sensing lead to the root bending down (gravitropism)? (amyloplasts, starch, auxin)*

• Gravitropism: plant's ability to respond to gravity • Roots sense gravity through cells in its root cap (when it is removed, they no longer can sense gravity) that contain starch. • Amyloplasts: cells in the root cap that contain starch that are pulled to the root cap due to the density of starch, activating pressure receptors proteins which might trigger a signal transduction cascade and gravitropic response • Auxin in roots inhibits root elongation, so roots bend away from sunlight and respond gravitropically.

Apply the Hagen-Poiseuille equation to blood flow in vessels. You should be able to compare two vessels and determine which one has a higher flow rate (flow, pressure, length, radius, viscosity).

• Hagen-Poiseuille equation: Q = (pressure difference * pi * radius^4)/(length*8*viscosity of the fluid) ◦ Q = flow rate (V/time) • A vessel with a higher flow rate could have a larger pressure difference of fluid going in/out of the tube, a larger radius, a shorter length, or a smaller viscosity of the fluid compared to a vessel with a lower flow rate

Distinguish between heartwood and sapwood in terms of structure, function, and time of production.*

• Heartwood: lighter-colored wood, outer xylem cells, provides support to the plant • Sapwood: darker-colored wood, inner xylem cells, vascular tissue to conduct water

Predict the food habits of an animal (herbivore, omnivore, carnivore, nectarivore) based on the structure of its teeth and gastrointestinal tract. *

• Herbivore: less sharp teeth and a longer gastrointestinal tract for the breakdown of cellulase • Omnivore: sharp and dull teeth, longer gastrointestinal tract • Carnivore: sharper teeth from mechanical digestion, smaller gastrointestinal tract for the break down of more proteins and lipids

Explain observations that support the role of cytokinin in inhibition of senescence.

• High levels of cytokinin with low levels of auxin in a plant promote growth in leaf tissues. • Low levels of cytokinin with high levels of auxin in a plant promote growth in root tissues, so there abscicion zone is more sensitive to cytokinin and leaves become senescent and fall off

Explain how size and the surface area to volume ratio constrain the rates of physiological processes (surface area, exchange, SA/V)

• High surface area to volume ratio: larger animals, longer diffusion time (heat is lost less quickly), increased metabolic rate (requires more energy to function), slower mass specific metabolic rate • Low surface area to volume ratio: smaller animals, less diffusion time (heat is lost quickly), decreased metabolic rate (requires less energy to function), higher mass specific metabolic rate

Define homeostasis (internal environment, stable vs. constant, different parameters).

• Homeostasis: reducing internal changes compared to environmental conditions within the animal's cells, tissues, and organs, not a perfectly constant internal environment (stable with small internal fluctuations)

Define negative feedback as it applies to a hypothalamo-pituitary-(__) axis. Choose an example of an axis and write a step-by-step description of the regulation of release of each hormone in the axis (long-loop feedback, short-loop feedback).

• Hypothalamo-pituitary-(GnRH) axis: 1) hypothalamus increases the release of the neurohormone GnRH into the anterior pituitary through the portal system 2) the increase of GnRH in the portal circulation increases the secretion of FSH and LH into blood circulation from the anterior pituitary 3) FSH and LH acts on endocrine glands or target cells for those hormones, increasing their secretion of sex steroids into the plasma 4) high levels of sex steroids in the blood increase the hormone binding at their target cells ◦ Negative feedback of GnRH: If sex steroids build up in the blood, they inhibit the secretion of FSH or LH from the anterior pituitary OR GnRH from the hypothalamus; if the concentrations of FSH and LH build up in the general circulation system, then they inhibit the secretion of GnRH from the hypothalamus • Long-loop feedback: high concentrations of secreted hormones from the endocrine gland that inhibit the secretion of hormones from the anterior pituitary or hypothalamus • Short-loop feedback: high concentrations of pituitary hormones inhibit the secretion of hormones from the hypothalamus

Create a table showing the major endocrine glands, the hormone(s) they produce, the target tissues of each hormone, and the actions of each hormone.*

• Hypothalamus: growth hormone (releases GH), CRH (releases ATH), Thyrotropin-releasing hormone (releases TSH), GnRH, ADH, Oxycotin which control the release of hormones from the pituitary glands • Pituitary gland: GH (muscle growth), ACTH (cortisol), TSH (thyroid hormones), FSH and LH (sex hormones), PRL (mammary gland) • Paranthyroid gland: parathyroid hormone; regulates blood calcium levels • Adrenal glands: releases hormones (epinephrin, cortisol) in response to stress • Kidneys: EPO hormone for red blood cell production • Pancreas: insulin/glucagon that raise/lower blood glucose levels • Ovaries: estradiol, progesterone that effects secondary sex charact. and development for pregnancy • Testes: testosterone that regulates secondary sex charact in males

-a pump transports Na+ out of the cytoplasm into the surrounding solution (test yourself! Can you think of other changes that could cause ψ of a plant cell to change?

• If Na+ is pumped out of the cytoplasm, it decreases the concentration of Na+ within the cell and that would increase its solute potential (ψs). When the solute potential (ψs) increases, the overall water potential of the cell increases.

Make a diagram similar to figure 37.2 showing the signal transduction pathway for auxin that leads to cell wall loosening. Include the receptors ABP and ARF. How does the auxin pathway differ from the 'generic' signal transduction pathway in the figure? Consider showing how the cellular components differ in the absence and presence of auxin. (ER, H+ pump)

• If auxin is present, it results in a change in localization of the auxin binding protein and proton pump from the ER to the plasma membrane that isn't displayed in the generic signal transduction pathway. As the ABP and proton pump are attached, auxin binding to the ABP result in protons pumped out of the cytoplasm into the cell wall. The pH of the cell wall decreases as protons are pumped outwards, becoming more acidic. • Auxin also binds to auxin response factor proteins that can recruit RNA to induce gene expression in the nucleus, increasing cell wall proteins and proton pumps. • Expansion proteins are secreted from the cell due to a low/acidic environment in the cell wall, which cut hemicellulose that link cellulose microfibrils together. The result of these hemicellulose being cut is that cellulose microfibrils can expand outwards from each other and stretch the cell wall (likely to allow the plant to bend on its shaded sight towards light).

Trees can be killed if a ring of bark and vascular cambium all the way around the trunk are removed (this is called "girdling"). Explain why this kills the plant.*

• If girdling occurs or the ring of bark/vascular cambium is removed, then the phloem/xylem cells are destroyed and water/sucrose transport can't happen.

Describe how ψ of a cell would change in the following conditions: -the cell wall is degraded by enzymes.

• If the cell wall was degraded by enzymes, the wall pressure would decrease and that would decrease the turgor pressure of the cell. Since turgor pressure and pressure potential (ψp) have a direct relationship, the pressure potential (ψp) would decrease if the turgor pressure decreased. Overall, the decreased pressure potential from the degraded cell wall decrease the water potential.

Explain how is the electrochemical gradient used to import K+ and NO3- (channel, cotransport)*

• Import K+: with a H+ ATPase pump, protons are pumped out of the root hairs which creates an electrochemical gradient with a positive charge outside and a negative charge inside the root hair cells ◦ K+ enter into the root hairs through channels since they are attracted to its negative charge • Import NO3-: moves into the cell up its concentration gradient with cotransport as protons are pumped down theirs into the negatively charged root hairs

In C4 and CAM plants rubisco always operates under conditions of elevated CO2. How is this achieved in C4? in CAM plants?

• In C4 plants, carbon fixation occurs in the mesophyll cells that contain the enzyme PEP ase and the Calvin cycle occurs in the bundle-sheath cells that contain rubisco. The enzyme PEP ase fixes CO2 into a 4-carbon organic acid used in the Calvin cycle of bundle-sheath or continue on to form PEP ase within the mesophyll cells (continuing carbon fixation), allowing for more time the leaf's stomata closed. • In CAM plants, carbon fixation occurs at night while the Calvin cycle happens during the day (different times rather than different locations like in the C4 pathway). At night (when conditions are cooler in desert-like areas and water loss isn't as much of an issue), the plants stomata open and CAM plants take in CO2, fixing it into a 4-carbon organic acid with the enzyme PEP ase. The 4-carbon organic molecule is stored in the mesophyll cells' vacuole until daytime when it is processed to release CO2 for the Calvin cycle and regenerate PEP ase from G3P (the excess 3-carbon molecule is useful for other cellular purposes).

Read the section about drought response in Ninebark plants. How does the solute concentration in ninebark leaves differ in June and August? (In your response try to connect [solute] and water potential.)*

• In June there is less solute in the Ninebark leaves and higher solute potential, so there is high water potential in the plant's leaves. Since there is high water potential in the leaves, water is less likely to flow towards the leaves and be transpired. • In August there is more solute in the Ninebark leaves and lower solute potential, so there is low water potential in the plant's leaves. Since there is low water potential in the leaves, water will likely flow towards the leaves and be transpired into the hot environment.

Predict the relative success of C3, C4 and CAM plant in a cool, wet environment and in a hot dry environment. -cool and wet enviroment- water loss is less of an issue (c3), c3 is less of an investment (should be used when it can because its "cheap"

• In a cool, wet environment, water loss is less of an issue (the leaves can spend more time with the stromata open) and the C3 pathway would be successful as less of an investment than the C4 and CAM pathway. • C4 and CAM plants would be more successful in a hot, dry environment since their stomata is closed more than C3, resulting in less water loss, and carbon fixation would still occur.

Suggest an explanation for why phloem transport requires living cytoplasm in the sieve tube members (remember that xylem cells are dead at functional maturity.) (active transport, membrane, concentration)

• In order for sucrose to be transported from the sieve tubes into the companion cells with active transport, decreasing the concentration of sucrose, then there needs to be a living cytoplasm.

The light reaction of photosynthesis begins when pigments in the chloroplast absorb light energy (photons). At the end of the light reaction, where is the energy derived from the photons stored? (ATP, NADPH, reduced molecules) (Figure 10.16 is particularly helpful)

• In the light reaction, the electron transport chain produces ATP and NADP+ is reduced to NADPH as excited electrons from Photosystem I interact with Ferredoxin. • At the end of the light reaction, ATP and NADPH are stored as reduced molecules and later oxidized in the Calvin Cycle to reduce CO2.

How is ψ of the phloem different in the source and the sink? Draw a diagram showing how pressure and sucrose concentration influence ψ. What are the contributions of solute and pressure?

• In the phloem, there is a high concentration of sugar in the source and high pressure as water moves from xylem into the phloem. Since there is a high concentration of sugar, water from the xylem moves into the the source since it has high water potential compared to the xylem. • There is low pressure in the sink compared to the source, so there is low water potential (even though there is a low concentration of sugar in the sink). The sugar then moves from the source to the sink or from high water potential (high pressure potential, low solute potential) to low water potential (low pressure potential). **diagram in notebook

Explain how inactive enzyme precursors are released and then activated in the gut (zymogen).

• Inactive enzyme precursors of zymogen can be activated in the gut by HCl in the lumin of the stomach, which is produced by parietal cells. • Mucous cells release mucus to coat and protect cells from the release inactive pepsinogen that is activated because otherwise there is an increased risk of stomach ulcers. • If enzyme precursors of zymogen aren't activated then they would digest the digestive tract's own proteins.

Distinguish the major functions of the digestive system (ingestion, digestion, absorption, secretion, excretion, motility).

• Ingestion: something is eaten by the animal • Digestion: food is broken down as it moves through the digestive tract ◦ Mechanical digestion: physically breaking down the food particles into smaller pieces (ex. Chewing) ◦ Chemical digestion: breaking down the macromolecules in the digested food to be small enough to move into the blood and circulate throughout the body • Absorption: broken down molecules are absorbed across the mucosa lining the lumen of the digestive tract and cross the extracellular fluid into the blood • Motility: moves digested molecules along with parastasis (slow to maximize digestive efficiency and fast to excrete undigested waste) • Excretion: undigested waste is excreted from the animal's digestive system to make room for more nutrients

Under what environmental conditions might there be selective pressure to promote internode elongation? Inhibit internode elongation?

• Internode elongation promoted: high competition with neighboring plants for sunlight • Internode elongation inhibited: low competition with neighboring plants, sunlight is more available

Does the surface area to volume ratio impose more of a limit on the upper body size of plants or animals? Why? *

• It imposes more of a limit on animals because it the size of the animal's upper body requires energy, but surface area is necessary to diffuse oxygen/nutrients in and urea/CO2 out. Plants often already have a low surface area to volume ratio to allow for gas exchange and water to be absorbed.

Create a list of macronutrients and micronutrients common to plants and animals.

• Macronutrients: nitrogen, potassium, phosphorus, sulfur, magnesium, calcium • Micronutrients: copper, iron, manganese, zinc, nickel, boron, molybdenum

Define the terms osmolarity, hyperosmotic, and isoosmotic. Compare these terms with the terminology used to describe water potential in plants.

• Osmolarity (osmol/L): overall concentration of solutes in an aqueous solution (taking ALL solutes into account) • Hyperosmotic: more concentrated than another solution • Hypoosmotic: less concentrated than another solution • Isoosmotic: same concentration as another solution (water moves in and out at the same rate) • When describing water potential in plants, water moves from high water potential to low water potential which can be caused by pressure or solute concentration within different regions. High water potential in plants is typically associated with low solute concentration and low water potential is associated with high solute concentration, so water (for short distances in the plant) is typically moving from an environment of low solute concentration to high solute concentration. Similarly, in osmosis water moves from a hypoosmotic environment to a hyperosmotic environment or from an area of less concentrated solutes to an area of more concentrated solutes. This is because there is high osmolarity to less free water in a hyperosmotic solution than a hypoosmotic one, so there is lower water potential and water is flowing in that direction.

Describe how oxygen and carbon dioxide are transported in the blood (bound vs. free gases, hemoglobin, bicarbonate, carbonic anhydrase, HCO3-/Cl- exchanger). *

• Oxygen binds to hemoglobin in red blood cells (98.5%) while 1.5% diffuses into the plasma membrane as a free gas • The rate of O2 unloading into tissues from hemoglobin depends on the partial pressure of O2 in the tissues ◦ High partial pressure of O2 in the blood results in a high percent of hemoglobin saturated and high concentration of O2 unloaded ◦ All hemoglobin is bound to oxygen when the partial pressure of oxygen in the blood is high (cooperative binding) • CO2 diffuses into red blood cells from tissues and most commonly (70%) form HCO3- with the enzyme carbonic anhydrase, exiting with a cotransporter (chloride shift) ◦ As a result Cl- ions enter into the red blood cell ◦ 23% of CO2 binds to hemoglobin at an allosteric site ◦ 7% of CO2 dissolves into the plasma membrane

What is the relationship between blue light and phototropism (signal, receptor, response, phototropin [PHOT1])

• PHOT 1 receptor: receptor protein that activates by absorbing signals of blue light, responding in a shape change as kinase. Kinase can add phosphate groups to proteins or creating phosphorylation of targets, allowing those proteins to be more active in the case of auxin.

Describe how the stomach produces acid and how acid is involved in digestion (parietal cell, proton pump (H+/K+ ATPase), carbonic anhydrase, pepsin, etc.).

• Parietal cells excrete HCl to activate the enzyme pepsinogen (released by chief cells) in order to form pepsin which catalyzes the break down of proteins into peptides for digestion. • Proton pump (H+/K+ ATPase) uses ATP to pump protons into the lumen of the stomach and potassium ions out. • K+ is pumped along the apical membrane of the parietal cells into the lumen. • HCO3- is released into interstitial fluid and Cl- is absorbed into the parietal cell and then into the lumen of the stomach, forming an acidic environment to activate pepsinogen for protein breakdown.

Distinguish between partial pressure and concentration of gases in biological solutions.

• Partial pressure: the amount of a particular gas in a mixture of gases (gases move down a gradient of partial pressure rather than concentration) • Concentration: the total concentration of gases in a mixture

Identify the three major chemical classes of hormones and the location and function of their receptors (intracellular, plasma membrane, nuclear, second messenger).

• Peptides: links of amino acids, receptor is located on the cell surface/plasma membrane, signal transduction cascade at each step that phosphorylates proteins in the cell to turn off/on biochemical reactions • Steroid Hormones: made from cholesterol, maintains proper fluidity of plasma, binds to intracellular receptors for transcription/modification that change the types of enzymes within the cell • Amines (catecholamines): derived from tyrosine, binds to receptors on the cell surface that undergo second messenger to modify enzyme activity • Amines (thyroid hormones): derived from tyrosine/iodine, bind to intracellular receptors for transcription/modification that change the types of enzymes in the cell

No two organisms look exactly alike. Distinguish the roles of genetic diversity and phenotypic plasticity in creating the differences between organisms. (genes, environment, species)

• Phenotypic plasticity results in different phenotypes or forms due to environmental conditions. • Genetic diversity or variation results in different phenotypes or forms due to DNA differences between them. • If two plants that were genetically the same species were placed under different environmental conditions, then the differences would be result of phenotypic plasticity. If two different species of plants were observed under the same environmental conditions (light, altitude, location, etc.), then the differences between the two plants would be a result in genetic variation.

Describe how hormones and the nervous system regulate stress responses in vertebrate animals (cortisol, epinephrine, glucocorticoid, sympathetic, long-term). *

• Phosphorylase becomes a source of blood glucose during a short term stress response. ◦ When epinephrine is present, it activates large amounts of phosphorylase in liver cells. • cAMP levels inside the heart increase from stress and it acts as a second messenger for phosphorylase to increase epinephrine. • Long-term stress is a result of cortisol produced by the adrenal cortex, which activates glucocorticoids for glucose synthesis. The price is that glucocorticoids might lead to muscle degradation or suppress immune repsonses.

Compare and contrast the extent of phenotypic plasticity typically seen in animals and plants. *

• Plants have indeterminate growth, which means that phenotypic plasticity (phenotype differences based on environment) effects them differently than animals that have determinate growth and reach structural maturity at a certain age. • A plant in a competitive environment for sunlight and nearby plants might grow taller vertically than the same plant in an environment with lots of space. • Animals within the same species, but living in different environments have a smaller extent of phenotypic plasticity because they lack the ability to adapt to their environment within their lifetime.

What properties of meristem cells permit plants to grow continuously (i.e. indeterminate growth) throughout life? (mitosis, differentiation)

• Plants have indeterminate or continuous growth throughout their lives due to meristem cells. Meristem cells are clusters of undifferentiated cells that undergo mitosis, either differentiating or remaining in the meristem as a daughter cell. Since some daughter cells as a product of mitosis remain in the meristem and don't differentiate, it allows for the meristem to continue to function by either lengthening, widening, or adding on new parts of the plant structure. • Shoot or root apical meristems lengthen the plant outward. Axillary meristems have the potential to add on new structures to the plant.

Distinguish between positive pressure and negative pressure and explain how either of these two pressures can result in the movement of water. (guttation, cohesion-tension theory)

• Positive pressure: the build up or increase of pressure within a region • Negative pressure: the release of pressure from a region of high pressure • According to the cohesion-tension theory, when transpiration occurs the water molecules extending into the root are pulled upwards due to the polar, hydrogen bonds between them. In addition, the positive pressure in the plant's root is turned into negative pressure as water forced into the xylem cells. • Guttation occurs when there is low transpiration, so water is being pulled upwards through the xylem cells according to the cohesion-tension theory. This causes a build up of pressure in the plant that is released through pores as droplets.

Describe the anatomical connections and physiological relationship between the hypothalamus and anterior pituitary gland, and between the hypothalamus and posterior pituitary gland (portal system, neurohormone, endocrine cell, neuroendocrine cell).

• Posterior pituitary: anatomically an extension of the hypothalamus with neuroendocrine cells; secretes ADH and oxytocin (synthesized in the hypothalamus) into blood vessels that are targeted at kidney nephrons, uterine muscles, and mammary glands • Anterior pituitary: anatomically connected with blood vessels or a specialized portal system; maintains homeostasis; neurohormones (CRH, GnRH, GHRH, TRH, Dopamine) travel from the hypothalamus into the anterior pituitary to stimulate the release of ACTH (adrenal cortex), FSH and LH (testes/ovaries), GH (many tissues), PRL (mammary glands), and TSH (thyroid gland) that act on target tissues

Distinguish between primary growth and secondary growth in plants.

• Primary growth: lengthening of the plant from shoot or root apical meristem cells, branching of new stems and leaves (cell expansion) from pockets of axillary meristem cells; allows for the plant to compete with neighboring plants, absorb more light and water, higher levels of gas exchange • Secondary growth: increases width of the stem to strengthen the plant for growth, produces vascular tissue to carry water and sap through the plant, new set of xylem cells form (older cells become wood and increase width of stem) and new set of phloem cells form (old set expand thickness of the cork)

Describe the structural and functional relationship between the respiratory and circulatory systems.

• Respiratory system: includes ventilation and gas exchange steps; movement of water/air to a location for gas exchange to occur between the animal and the environment ◦ Gas-exchange surface could be the skin, gills, or tracheae of different animals • Circulatory system: movement of CO2, O2, and nutrients around the body ◦ Supported by blood in a closed circulatory system, hemolymph in an open circulatory system, vessels to carry fluid to other parts of the body, and the heart • O2 moves into the blood from the respiratory system and circulates throughout the body with the circulatory system. CO2 moves into the blood from tissues and is circulated out of the body towards the respiratory system and respiratory surface.

In addition to pumping H+ into the environment, root acidify soil in another way. What is it? (note, This is similar to what causes the Bohr shift in the animal body.)

• Roots can acidify soil by increasing the partial pressure between the roots and the surrounding soil. By creating a larger pressure difference between the partial pressure of one molecule inside and outside of the root, it decreases the pH of the surrounding environment. This would create an acidic environment for a plant's roots without pumping protons and cations would be attracted to root hairs.

Photorespiration is sometimes described as "undoing photosynthesis". Interpret this phrase. A complete response should include TWO ways that photorespiration drains energy from plants. (fixed C, ATP, RuBP)

• Rubisco can use CO2 or O2 as a substrate depending on the concentration of the molecules within the leaf. O2 is favored as a substrate for rubisco to catalyze RuBP when there are high concentrations of O2 and low concentration of CO2 (usually when stomata is closed to prevent loss of H2O), resulting in photorespiration or "undoing photosynthesis". 1. CO2 is lost to the environment when the plant has already worked hard to obtain it (wasteful) 2. ATP is used up in photorespiration; loss of energy that plant worked hard to obtain in light reactions and could've been used in the Calvin cycle for carbon fixation

Explain the mechanism that allows some plants to survive in very salty soil. You should be able to explain the phenotypic difference between the transformed and control plants shown in figure 36.13 (Na+, exclusion, antiporter)*

• Salt-tolerant plants have additional H+/Na+ antiporters in the tonoplast between the plant cells' cytoplasm and vacuole. Although they also have a H+ ATPase pump that pumps protons into the vacuole and creates an electrochemical gradient, H+/Na+ antiporters pump Na+ into the vacuole against its concentration gradient to allow for H+ to leave. As protons leave the vacuole, they can be used to for cation exchange in the soil. • Transformed plants: "salt-tolerant" due to additional H+/Na+ antiporters, ability to thrive in soil with low/high concentrations of salt • Control plants: inability to grow in salty soil, lacks additional H+/Na+ antiporters

Explain why water potential is lower in salty soils. ...lower in dry soil. Is water more or less likely to enter a plant root in these conditions? (solute, tension)*

• Salty soil: water potential is lower because there is a high solute concentration of Na+, so water would be less likely to enter the plant root since it always moves from high to low water potential (the plant root would have high water potential than the soil) • Dry soil: water potential is lower because of the tension between the water and dry soil particles, so water would be less likely to enter into the plant root since it always moves from high to low water potential (the plant root would have high water potential than the soil)

What plant cell types produce lignin? How do plants benefit from lignin production? (hydrophobic, cell wall)*

• Sclerenchyma cells: produce lignin that supports the stems after growth and provides protection to the plant (dead at maturity, no cytoplasm, no secondary cell wall, thin primary cell wall)

For each type of transport across plasma membranes (simple diffusion, facilitated diffusion, primary active transport, and secondary active transport), describe how and why a molecule moves across a membrane. *

• Simple diffusion: small, non polar molecules move through the plasma membrane (passive transport & moves with the concentration gradient) • Facilitated diffusion: larger/polar molecules/glucose/charged ions need the help of a transport protein to cross the plasma membrane through (passive transport & moves with the concentration gradient) • Primary active transport: molecules move against the concentration gradient (low to high concentration), requires energy in the form of ATP • Secondary active transport: molecules move against the concentration gradient (low to high concentration) with proteins along the plasma membrane that use an electrochemical gradient developed from primary active transport

Identify the reasons why water and electrolyte homeostasis are important in animals.

• Since animal cells can't actively pump water, they control the ionic composition within the cells in order for osmosis or passive diffusion to occur and maintain homeostasis. • If animal cells are in an hypotonic environment, then lysis will occur and the cells will burst/swell. • If animal cells are in a hypertonic environment such a solution of NaCl, then crenation will occur and then cells will shrink.

What is the relationship between solute concentration and solute potential (ψs)? What is the relationship between turgor pressure and pressure potential (ψp)?

• Solute concentration and solute potential (ψs) have an inverse relationship; the solute potential (ψs) decreases as the solute concentration increases • Turgor pressure and pressure potential (ψp) have a direct relationship; the pressure potential (ψp) increases as the turgor pressure increases

Distinguish between sources and sinks. Make a list of plant tissues that are sources or sinks keeping in mind that some tissues can switch from one to the other during the plant lifecycle (photosynthesis, storage, respiration)

• Source: location where sugar is exported and enters into the phloem cells (photosynthesis produces sugar that is exported through the plant) ◦ mature leaf, mature storage organ (ex. Potato), seeds during germination • Sink: location where sugar is consumed or exists in the phloem cells ◦ Young/old/shaded leaf, developing storage organ, seeds as they develop, flowers

Describe the events that occur inside cells when they are stimulated by hormones (receptor, signal transduction, second messenger, phosphorylation, transcription, translation).

• Steroid and thyroid hormones bind to intracellular receptors and transported into cell with carrier proteins, resulting in the trasncription/modification of enzymes in the cell. • Peptide and catecholamine hormones are secreted via exocytosis and bind to receptors on the cell surface, resulting in a second messenger that phosphorylate proteins to act as enzymes in a signal transduction cascade.

Sucrose becomes concentrated in the sieve tube elements in source tissue. Explain how this occurs and include the following in your description: companion cell, H+ ATPase, pump, cotransport*

• Sucrose is formed in a mesophyll cell through photosynthesis, which is moved towards a companion cell using ATP into a sieve-tube cell through the plasmodesmata. The sucrose becomes concentrated in the sieve-tube cells of source tissue and moves through the phloem to the sink tissue where there is high water potential and lower pressure potential. A cotransport allows for a electrochemical gradient for protons to be formed from H+ and ATPase.

Give examples of how diverse mouthparts are related to the type of food eaten (e.g., insects, snakes, humans, cichlid fishes, etc.). *

• Suspension feeders: nets or cilia, grab small food particles as they go by in the water ◦ Sponges, tube worms • Deposit feeders: extract nutrients from sediment ◦ Earthworms, sea cucumbers • Suction feeders: suck up sap, nectar, blood ◦ Bees, insects • Mass feeders: large canines, flexible jaws, eat larger chunks of food ◦ Most animals, snakes, cichlid fish (upper and lower pharyngeal jaw)

Describe how hormones are involved in regulation of body growth and body weight (leptin, leptin receptors, "db", "ob", appetite). *

• TSH is secreted from the pituitary gland, which produced T4 and then T3 at target tissues. • Overproduction/hypersecretion of the thyroid would result in a lower body weight. • Decreased leptin stimulates appetite and surpasses energy until energy is restored. • Increased leptin represses appetite and increases energy expenditure.

Explain how tetrapods (terrestrial vertebrates) move air in and out of their lungs and contrast the positive pressure mechanisms found in amphibians and the negative pressure mechanisms found in mammals. *

• Tetrapods or terrestrial vertebrates move air in and out of the alveoli or sacs in lungs through muscular contractions rather than diffusion • Amphibians create positive pressure as nostrils/mouth can be shut to force air into its lungs • Mammals create negative pressure as their lungs expand through the thoriac cavity and increase in volume to decrease the pressure and allow air to flow in

How does anatomical structure relate to physiological function? What is the distinction between anatomy and physiology? Provide specific examples.

• The anatomical structure of tissues, cells, and organ systems supports the physiological functions that the animal performs. This is similar at a cellular level in how cell shapes correlate with its specialized function. • Anatomy: structural components of an animal • Physiology: processes or activities that an animal performs

How do the experiments on page 757 (737 in the 6th edition) support the cohesion-tension theory?*

• The experiment demonstrated that as light intensity on the plant increased, the xylem pressure in leaves decreased. By increasing light intensity, it supported the cohesion-tension theory as more water transpired from the plant, ultimately increasing the water potential and pressure in the leaves.

Describe the most robust type of experimental design for determining the action of a given hormone, the removal-replacement study. Explain what result would support the role of a hormone in a particular bodily function and what result would refute the role of a hormone in that function.*

• The experimental design to determine the action of a given hormone would be to inject an inhibitor for a particular hormone. If the hormone is no longer signaled to release, it would refute the role of a hormone in that function, but if it was released then it would support it.

What happens to the sugar that is produced by photosynthesis? (storage, respiration, sucrose, starch, structure, cellulose)*

• The glucose produced by photosynthesis can be combined with oxygen to be used cellular respiration, generating ATP. • The sucrose from cellular respiration that wasn't used to generate ATP takes the form of cellulose. • The glucose not used in cellular respiration becomes starch, which is beneficial for cell walls or creating the enzyme PEP ase in CAM plants.

Interpret the hemoglobin-oxygen dissociation curve, and identify conditions in which the curve would be shifted to the left or right (pH, pCO2)

• The hemoglobin-oxygen dissociation curve plots the percent saturation of hemoglobin relative to oxygen concentration as the partial pressure of oxygen in the blood increases. At first and when hemoglobin is fully saturated the percent of O2 concentration changes slowly. When PO2 increases a small amount when hemoglobin isn't fully saturated yet, it leads to a large amount of O2 unloaded by hemoglobin. • Right shift: increase in partial pressure of O2 along the x-axis causes a decrease in pH, increase in temperature, increase in the partial pressure of CO2 in the blood, and decrease the affinity for O2 to bind to hemoglobin (O2 is released more readily into tissues) • Left shift: decrease in partial pressure of O2 along the x-axis causes a increase in pH, decrease in temperature, decrease in the partial pressure of CO2 in the blood, and increase the affinity for O2 to bind to hemoglobin (O2 is released less readily to tissues)

Describe why the hypothalamus and pituitary glands are often called the "master glands" of the endocrine system.

• The hypothalamus and pituitary glands are often referred to as "master glands" because the hormones they release trigger the release of other hormones throughout the body known as hypothalamic-pituitary hormone cascades. If levels of hormones increase along the hypothalamic-pituitary hormone cascade, then the production of hormones from the hypothalamus or anterior pituitary is inhibited.

In a typical tree where are the living cells and where are the dead cells? Make a guess about how much of the bulk of the tree is alive vs. dead cells.

• The living cells are in the vascular tissue system that transports water, nutrients, and sugars through the tree, including the most recent xylem (tracheids, vessel elements) and phloem cells (sieve-tube elements, companion cells) formed. • The vascular cambium, separating the new xylem and phloem cells, contains meristem cells that are living and haven't yet differentiated. The cork cambium on the inside of the tree's epidermis also contains meristem cells that differentiate towards the cork. • The dead cells are in the wood and cork of the tree, which contains the older xylem cells as they are pushed outwards when new layers form, and phloem cells when they are crushed to form the cork/bark. • The bulk of most trees is likely dead. Many cells are dead at functional maturity so after cells have differentiated from the immature meristem cells, they are usually dead.

What is the origin of nitrate (NO3-) in soil and how/where does nitrate become reduced? (decomposition, NADH, NADPH)

• The origin of nitrate in soil is from the decomposition of plants. • Nitrate is taken up in the root hairs and reduced with the addition of electron carriers such as NADH and NADPH to create NH4+.

How does the presence of leghemoglobin influence the efficiency of N2 fixation? Which organism (plant or rhizobia) produce this protein?

• The plant produces leghemoglobin • Leghemoglobin contains iron to bind to oxygen, so that the oxygen doesn't effect the rhizobia in the plant's nodule. If oxygen doesn't interact with the rhizobia, then the bacteria can effecting fix N2 into NH4+ for the plant's nitrogen metabolic process to produce macromolecules, proteins, and nucleic acids.

What is the role of hydrogen bonds in water movement from roots to leaves? (Cohesion-tension theory).

• The polar, hydrogen bonds link the water molecules within a plant. According to the cohesion-tension theory, water molecules pull the water molecules behind them as they are transpired due to their hydrogen bonds which extend all the way into the plant's roots.

What is the primary function of leaves? What other functions can modified leaves serve?*

• The primary function of leaves is to serve as a place for photosynthesis and gas exchange in order to produce sugars that support the plant body. • Modified leaves such as bulbs with thick leaf bases and small internodes are able to store nutrients for the plant to use at a later time. Succulent leaves are able to store water and tendril leaves assist the plant in climbing, which can increase the amount of sunlight reaching the plant when there is nearby competition. Floral mimics allow for colorful leaves that attract pollinators, traps like in pitcher plants digest insects that get stuck inside the leaf, and cactus spines function as leaves to protect the stem from herbivores.

Which of the following best describes the osmoregulatory strategy of sharks?

Sharks maintain a similar osmolarity to seawater, but using different solutes.

Hemoglobin would have the lowest oxygen affinity in...

Systemic capillaries in muscle of an exercising human Correct! We expect low pH and high CO2 levels to cause a right shift (reduced affinity) in the oxygen-hemoglobin dissociation curve.

In a typical fish swimming in a typical lake...

The O2 concentration in the lake water is lower than the total O2 concentration in the red blood cells of the fish, but the PO2 is lower in the red blood cells than the lake water. Correct! Oxygen concentration in the red blood cells is enhanced by the binding of oxygen to hemoglobin, but the partial pressure gradient still favors the movement of oxygen from the lake water into the fish's blood.

Which of the following is an example of secondary active transport?

Transport of glucose from the filtrate into kidney proximal tubule cells. Correct! The proximal tubule uses the Na+ gradient set up by the Na+/K+ ATPase to drive glucose out of the filtrate, against its gradient.

What are the characteristics of "essential" nutrients? What is the relationship between the essential nutrients, macronutrients, and micronutrients?*

• "Essential" nutrients are obtained from the environment, and are essential to normal health and development of the plant/animal. • 96% of the "essential" nutrients in a plant/animal is carbon, oxygen, and hydrogen while 3.5% is macronutrients and 0.5% is micronutrients. Macronutrients serve as components of macromolecules such as proteins/nucleic acids that are essential for plant growth. Micronutrients serve are very reactive with organic molecules and serve as enzyme cofactors to help catalyze reactions. ◦ Micronutrients/macronutrients are obtained from soil while the other "essential" nutrients can be obtained from the air.

A cellular response to a chemical or environmental signal begins when the signal is "transduced." Explain what "transduction" means in this context. (receptor, plasma membrane)

• "Transduction" in this context means that sensory cells in the plasma membrane respond to external signals that don't pass through the plasma membrane. The external signal is then changed into an intracellular signal by the receptor that is amplified and required for a cellular response.

When a mammal inspires (takes a breath in)...

Expansion of the chest reduces the air pressure in the alveoli below the atmospheric pressure. This is called negative pressure ventilation.

The largest quantity of water is reabsorbed in which part of the mammalian nephron?

Proximal convoluted tubule

Which statement correctly describes the tracheal systems of insects?

The tracheal system relies on the low viscosity of air.

Which characteristic of insects that live in dry environments makes them more susceptible to dehydration?

They have a high ratio of external surface area to body volume. A high surface area to volume ratio increases the rate of diffusion, including water loss, across the body surfaces.

Consider water as it moves from soil to root to stem to leaf to air. How does the water potential (ψ) in these different regions compare? (xylem)

• As water moves from the soil to the root, there is a lower water potential in the root than the soil. This is because there is a high concentration of solute or ions transported into the root through active transport. A high concentration of solute, lowers the solute potential and decreases the water potential of the root compared to the soil. • As water moves from root to stem, there is a lower water potential in the stem than the root. There is positive turgid pressure within the root due to the build up of water and ions. To release this pressure, the water is forced upwards into the xylem up towards the plant stem. As the water moves from an area of high turgid pressure to low pressure, the pressure potential decreases and the water potential decreases. • As water moves from the stem to leaf, there is lower water potential in the leaf than the stem due to transpiration. In the leaf the wet mesophyll cells release water through transpiration into the environment. This process decreases the pressure potential and therefore the water potential in the leaf, causing water to move from the stem to leaf. • As water leaves the leaf to the air through transpiration, this process occurs when there is lower water potential in the atmosphere compared to the leaf. Under dry and windy conditions compared to humid conditions, there is a lower water potential in the air compared to the leaf, allowing the water to be released from the wet mesophyll cells into the air.

Identify and define the five major classes of chemical signals in animals.

• Autocrine: chemical signal circles back to act on the cell that secreted it • Paracrine: chemical signal acts on nearby cells • Endocrine: secretes hormones that travel through the bloodstream to diffuse into the target cells • Neural: presynaptic cells release chemical signals into a synapse between neurons, sending an electrical signal down the postsynaptic cell • Neuroendocrine: hormones released from neurons that act on cells farther away

Distinguish between autotrophs and heterotrophs.

• Autotrophs: ability to synthesize organic molecules from inorganic sources; make their own nutrition ◦ most plants • Heterotrophs: eat other organisms to get the nutrition they need

How do auxin and cytokinins interact to determine whether tissue develops into root or shoot? Where is each hormone produced and what tissues does each influence?

• Auxin: produced in the shoot apical meristem and influences the root meristem, triggers a phototropic/gravitropic response, inhibits branching from axillary meristems • Cytokinin: produced in the root apical meristem and influences the shoot meristem, inhibits senescence (prolongs the photosynthetic life of leaves) • High auxin concentrations and low cytokinin concentrations result in growth of root tissues. • Low auxin concentrations and high cytokinin concentrations result in growth of leaf tissues.

Distinguish between the roles of bile and lipase in the digestion of fats (emulsify, catalyze). *

• Bile secreted by the liver catalyze the breakdown of larger amounts of lipids in the form of triglycerides. • The amphipathic (both hydrophobic and hydrophilic) properties of bile allow the hydrophilic ends to emulsify the triglyceride into smaller droplets. • The smaller droplets of triglyceride are catalyzed by the pancreatic lipase in the small intestine to form monoglycerides and free fatty acids that can be digested as nutrients and circulated throughout the body.

Under what environmental conditions might there be selective pressure to promote branching? Inhibit branching?

• Branching promoted: low competition with neighboring plants, lots of room for plant to extend horizontally for sunlight • Branching inhibited: high competition with neighboring plants, less room for plant to extend horizontally, more vertical growth than branching to obtain more sunlight

What is the advantage to plants of pumping protons (H+) from root cells? (H+ ATPase, cations, clay, electrochemical gradient)

• By pumping protons from root cells from a H+ ATPase pump, it creates an electrochemical gradient so that there is a net positive charge outside the root hairs and a net negative charge inside the cells. • Protons (H+) are attracted to clay due to its negative charge, which attracts cations to the root hairs' negative charge due its electrochemical gradient • Cations can enter root hairs through channels and anions can enter up their concentration gradient with contransporters

Compare and contrast how marine cartilaginous fishes, marine bony fishes, and freshwater bony fishes osmoregulate. For each group, you should be able to identify pathways of passive water and solute movement at the whole animal level and how the animal compensates for these fluxes.

• Cartilaginous fish: rectal gland maintains a low concentration of NaCl in the animal ◦ Na+/K+/ATPase pumps Na+ out of the basolateral surface and K+ in; forms an electrochemical gradient via active transport ◦ Na+/Cl-/K+ cotransporter brings Cl- and K+ into the cell via secondary transport, Na+ enters the cell down its concentration gradient w the cotransporter ◦ Chloride channel diffuses Cl- down its concentration gradient into the lumen side of the rectal gland ◦ Potassium channel diffuses K+ into the interstitial fluid out of the cell ◦ Na+ diffuses into lumen in between cells • Marine bony fishes: obtains Na+ and water through ingestion, but loses Na+ and water in urine and through gills, active transport of Na+ in chloride cells of the gill epithelium ◦ Na+/K+/ATPase and electrochemical gradient ◦ paracellular transport of Na+ out of intersitial fluid and into seawater ◦ potassium channel that diffuses K+ into the interstitial fluid from the chloride cell ◦ Na+/K+/Cl- in cotransporter in basolateral membrane ◦ Chloride channel that diffuses Cl- from the chloride cell in the gill epithelium into the seawater • Freshwater bony fishes: active transport of Na+ back into the body across gills (opposite problem as marine bony fishes) ◦ Na+/K+/Cl- in cotransporter in apical membrane (other side of epithelium) ◦ Different forms of Na+/K+/ATPase ◦ Chloride cells in the gills are sometimes in different locations than in marine bony fishes

Describe the structure and function of the major organs and tissues of the digestive system, and predict how the structure of these organs might be different in other organisms that eat different types of food (e.g., cows, snakes, and others). (mouth, esophagus, stomach, small intestine, large intestine, liver, pancreas) *

• Mouth: location of mechanical digestion or chewing in mammals to make food pieces smaller, salivary amylase and mucus are released to allow food to be swallowed, triglycerides are broken down into diglycerides and fatty acids by lingual lipase from the tongue • Esophagus: muscular tube that connects the mouth to the stomach, peristalsis (a reflex) allows muscles in the esophagus to contract behind the food and relax below it in order to push it down towards the stomach ◦ Birds have a crop or segment of the esophagus for food storage for their offspring or to allow them to eat large amounts of food at once • Stomach: sphincters on the openings of the stomach to limit what substances enter/leave, muscles form a substance from the food pushed down by the esophagus, digests proteins (highly acidic - HCl from parietal cells) ◦ Cows, deer, sheep, goats, etc, have ruminants that digest cellulose rather than proteins in their stomach ◦ Birds have avian gizzards that are more muscular and digests larger/harder food safe from predators • Small Intestine: folded, containing microvilli and villi to increase surface area for nutrient absorption, specialized function depending on nutrient type; polysaccharides are broken down into monosaccharides (lactose, maltose) with pancreatic amylase and lactase/maltase, proteins are digested and broken into amino acids from peptides with the enzyme trypsin (formed from trypsinogen), lipids are broken down from triglyceride as amphipathic bile allows pancreatic lipase to form monoglycerides/free fatty acids • Large Intestine: gut microbes form cellulase to break down cellulose into sugars, fatty acids, vitamin K; compact waste with the addition of water in the colon to form feces ◦ Rabbits, horses, etc. have a cecum at the end of the large intestine for a cellulose femermentation ◦ Humans have a appendix in the large intestine that contains immune system cells • Liver: filters blood coming from the digestive tract, secretes bile • Gallbladder: stores bile for the breakdown of lipids • Pancreas: forms energy from digested food, regulates blood sugar • Rectume: stores feces • Anus: eliminates feces

What is a mycorrhizal fungi and are these fungi helpful or harmful to the plants they interact with? (nutrients, mutualism)

• Mycorrhizal fungi connects multiple plants underground through the root system • Mycorrhizal fungi provides a net transfer of sugars to plants depending on their metabolic need (shaded plants) ◦ Ex. Transfer of sugar from plant in light (obtains sugar through photosynthesis) shade • Mutual relationship: fungi is kept alive while plants in need of sugar benefit

Understand the components of a regulatory feedback loop and apply the concept to different physiological variables. For example, body temperature in a mammal (set point, sensor, integrator, effector, controller, hypothalamus, 37°C). Now apply this to a lizard. What about plants?

• Negative feedback loop: maintains homeostasis, restores the initial conditions to bring the system back it its set point • Positive feedback loop: perpetuates change, amplifies the disturbance to drive the system farther from its original set point • The sensor senses the external/internal environment, the integrator compares the information from the sensor to the ideal set point, the effector generates some kind of change, the amplifier creates a change in the same direction as the disturbance • For mammals, the integrator is the hypothalamus as it compares the body's internal temperature to the set point of 37 degrees celsius. • Since lizards are poikilotherms, they have no internal regulation system, but they can physically move to change their external temperatures. If it is cold, they can move to sun and if is hot, they can move to the shade. • Plants can open/close their stroma to regulate their conditions by allowing for more water to enter/leave the plant and gas exchange.

Identify the 4 major tissue types in animals, and describe how their structures relate to their functions. *

• Nervous tissue: neurons containing dentrites and axons to conduct signals throughout an animal's body ◦ Dendrites are branched to pass a signal to as many nearby cells as possible, axons are very long to pass a signal from the cell body to other cells • Muscle tissue: distinct to animals like nervous tissue, allows for movement through contractile cells ◦ Skeletal muscle: layered with overlapping proteins that attach to bones to create a force for voluntary movement ◦ Cardiac muscle: branches out to signal throughout the heart which results in involuntary movement (pumps blood, contraction, relaxation) ◦ Smooth muscle: tapered at the end to regulate the digestive tract and blood pressure • Epithelial tissues: cover the body, organs, and glands ◦ Simple epithelia: a sheet of cells (one cell thick) to allow for gas, water, nutrients to move across it ◦ Stratified: many layers of closely-packed cells to protect against the environment • Connective tissues: bone, cartilage, tendons, ligaments, blood which consist of tissues with cells loosely arranged ◦ Loose, dense, supporting, and fluid connective tissue for different functions (holding organs together, connecting muscles, proving structure, and transporting materials

Nitrogen is described as being "very expensive" for plants to acquire; explain this statement. (N2, energy, fixation)

• Nitrogen is "very expensive" for plants to acquire because it requires a lot of energy. NH4+ is the starting point of a plant's nitrogen metabolism to create macromolecules, proteins, or nucleic acids, but it requires a lot of energy for the plant to form NH4+ from converting/reducing NH3 present in fertilizer or NO3- present from decomposition. In plants containing bacteria that converts N2 into NH4+ it requires a lot of ATP and NO3- requires NADPH/NADH to be converted into NH4+.

Compare and contrast the osmoregulatory challenges of living in the ocean, in freshwater, and on land (gradient, passive transport, osmosis, active transport).

• Ocean: ocean water is more concentrated than animal internal environment, water is lost through urine/gills • Freshwater: freshwater is less concentrated than animal internal environment, needs to maintain homeostasis by releasing water and active transport of Na+ into the animal across the gills • Land: lose water from skin, respiratory, urine, feces to the environment, water is obtained by ingestion to avoid dehydration

Distinguish between open and closed circulatory systems, and name the animal groups that have each type. *

• Open circulatory system: hemolymph is the fluid pumped by the heart into vessels throughout the animal's body ◦ Ability to come in contact with tissues (exchange of molecules doesn't have to cross a vessel wall) ◦ Hemolymph moves to and from the heart with body movements or internal heart pressure lowers ◦ Insects, crustaceans, spiders, mollusks • Closed circulatory system: blood is the fluid pumped by the heart into vessels throughout the animal's body ◦ Blood is confined by the tissues to create pressure, which results in a high rate of blood flowing in the body that can be directed to specific areas ◦ Earthworms, annelids, squid, octopus

Differentiate between osmoconformers and osmoregulators and give examples of animal taxa that exhibit each pattern.

• Osmoconformers: tissue osmolarity changes with the surroundings ◦ Most non-boney marine/freshwater (total concentration in their body is similar to the concentration of seawater) • Osmoregulators: maintains a blood osmolarity (concentration of water/solutes) regardless of the surroundings ◦ Terrestrial animals, marine invertebrates, marine/freshwater bony fishes