BIO226 Exam 1 - Photosynthesis, Herbivores & Plant Adaptations - PDF

Energy and Nutrient Relations: Autotrophs – use energy from inorganic sources to synthesize organic compounds, grow and reproduce Heterotrophs – use energy from organic sources (i.e. other organisms) to grow and reproduce Chemoautotrophs – Energy from the oxidation of electron donors in the envir...

Energy and Nutrient Relations: Autotrophs – use energy from inorganic sources to synthesize organic compounds, grow and reproduce Heterotrophs – use energy from organic sources (i.e. other organisms) to grow and reproduce Chemoautotrophs – Energy from the oxidation of electron donors in the environment (e.g. H2, H2S, CH4) -​ Nitrifying bacteria are important chemosynthetic organisms in terrestrial systems -​ Use CO2 as their carbon source, but get energy via the oxidation of ammonium (NH4) -​ Critical players in the biosphere’s cycling of nitrogen -​ Chemosynthetic bacteria that are symbiotic with communities of animals living on sea floor near volcanic activity -​ Use CO2 as their carbon source and get energy via oxidation reactions -​ Discovered an entirely NEW ecosystem in 1970’s -​ Not dependent on solar energy but chemosynthetic energy – this was a BIG deal!! Photoautotrophs – Energy from sunlight (Photosynthesis) -​ Light can be defined as a wave or particle (photon) -​ Infrared (IR) Long-wavelength, low energy -​ Interacts with matter, increasing motion -​ Ultraviolet (UV) Short wavelength, high energy -​ Can destroy biological machinery -​ Photosynthetically Active Radiation (PAR) -​ Between IR and UV is used for photosynthesis Photosynthetically Active Radiation (PAR) -​ Quantified as photon flux density -​ Number of photons striking square meter surface each second -​ Chlorophyll absorbs light as photons Two stages of photosynthesis Light reactions -​ Use light energy -​ Take place in chloroplast thylakoid membranes -​ Produce ATP, NADPH and O2 Calvin cycle -​ Occurs in chloroplast stroma -​ Uses ATP and NADPH to synthesize carbohydrate from CO2 Photosynthetic Pathways C3 Photosynthesis -​ Used by most plants and algae -​ CO2 + ribulose bisphosphate (5 carbon sugar) combine and immediately break into two phosphoglyceric acid (PGA) molecules -​ PGA is a 3-carbon acid, this is were C3 gets its name -​ Trade off: To fix carbon, plants must open their stomates to let in CO2 -​ Water escapes as CO2 enters Photorespiration = Calvin cycle running backwards!!! Rubisco functions as a carboxylase -​ RuBP + CO2 → PGA Rubisco can also be an oxygenase -​ Adds O2 to RuBP eventually releasing CO2 -​ This is called photorespiration -​ Using O2 and liberating CO2 is wasteful Photorespiration most likely in hot/dry environments (Favored when CO2 is low and O2 is high) C4 Photosynthesis minimizes photorespiration: -​ Reduce internal CO2 -​ Increases rate of CO2 diffusion inward -​ Needs fewer stomata open -​ Conserves water C4 Acids produced during carbon fixation move to specialized bundle sheath cells -​ The unavoidable tradeoff between CO2 gain and H2O loss is an extremely strong selection pressure in hot, dry environments. CAM Photosynthesis -​ CAM = Crassulacean Acid Metabolism -​ Mainly in succulent plants in arid environments -​ Carbon fixation takes place at night (reduce water loss) -​ Low rates of photosynthesis -​ Extremely high water use efficiency Compare water use efficiency -​ C3 plants lose 380 to 900 g H2O per g tissue -​ C4 plants lose 250 to 350 g H2O per g tissue -​ CAM plants lose ~ 50 g H2O per g tissue So why don’t all plants utilize the C4 or CAM pathways? A: Trade offs: -​ C4 plants require more solar energy than C3 plants (they need to build their “CO2 pump” -​ CAM plants grow very slowly At the global scale, where do you predict to find the most C4 plants? Warm and sunny areas – low latitudes C4 (warm sunny) Cooler wetter areas – high latitudes C3 (colder) -​ C3 plants are LESS efficient in fixing CO2 than C4 plants. -​ But C3 plants do better than C4 plants in cool, wet environments with low solar radiation. Herbivores: Must overcome plant physical defenses: -​ Thorns -​ Silica Must overcome plant chemical defenses: -​ Cellulose and lignin (C:N ratio) Must overcome plant chemical defenses: Herbivore pressure is greater in the tropics -​ Toxins -​ Digestion Reducing Compounds Detritivores: Consume food rich in carbon and energy, but poor in nitrogen. Adaptations: Camo: some insects have elaborate disguises that make them resemble twigs, leaves, bird droppings etc Mimicry: -​ Müllerian mimicry – noxious species converge -​ Batesian mimicry – palatable mimic copies unpalatable model Armor and weaponry -​ Turtle shells provide strong defense -​ Beetle exoskeleton -​ Horns and antlers can be used in defense Symbioses between autotrophs and heterotrophs: ex plants and myco fungi What five elements account for 93 - 97% of the biomass of plants, animals, fungi, bacteria, protozoa? CHO- organic molecules N-amino acids, DNA, etc. P - ATP, phospholipids etc. What makes up the remaining 3 - 7%? K, Ca, Mg, S, Cl, Fe, Mn, B, Zn, Cu, Mo, Na*, I * *required by animals but not plants STOICHIOMETRY: -​ deals with conservation of matter in chemical reactions -​ helps define the chemical constraints that organisms face in their trophic interactions C to N ratio: Plants C:N ~ 25:1 Animals C:N ~ 5:1 Bacteria C:N ~ 5:1 Fungi C:N ~ 10:1 -Herbivores must eat alot of plant matter to get enough nitogen (plant tissue has more c than n) Herbivores and carnivores experience different problems in getting energy from their food. Herbivores: -​ Low N in plant tissues. -​ Plant defensive compounds and structures. Carnivores: -​ Energy, speed and cunning is often required to capture herbivores. -​ Many herbivores fight back! IV. Optimal Foraging Theory: Predicts that organisms feed as an optimizing process that maximizes or minimizes some quantity, such as energy intake or predation risk. -​ Energy supplies are limited. -​ Organisms cannot simultaneously maximize all of life’s functions (principle of allocation). -​ Natural selection favors individuals that are the most efficient at acquiring energy (optimization). Experimental evidence that both animals and plant forage optimally In theory, if plants forage optimally, then what do you predict enriching soils with N, P, K, and water should do to plant allocation to roots versus shoots? A: Fertilizing soil should cause plants to allocate relatively less to roots and more to shoots. Behavioral Ecology = Interactions between organisms and the environment mediated by behavior. Sociobiology = Branch of biology concerned with study of social relations. Fitness = # offspring contributed by an individual relative to the # of offspring produced by other members of the population (… relative genetic contribution to future generations) Reproductive strategies: - Asexual = reproduction without the formation of gametes so no male-female separation is necessary a)​ e.g. budding, fission, parthenogenesis, spore formation and vegetative propagation. b)​ many bacteria, some fungi, some plants, a few animals - Hermaphroditic = having both male and female reproductive organs on the same individual a)​ E.g. many flowers, some animals b)​ simultaneous hermaphrodites have both sexes in the same individual at the same time c)​ Sequential hermaphrodites manifest different sexes at different times - Separation of sexes = having males and females on DIFFERENT individuals d)​ This strategy leads to mate choice and sexual selection What distinguishes males and females ? -​ Females produce larger, more energetically costly gametes. a)​ Female reproduction thought to be limited by access to resources b)​ Females of some species select mates based on the male’s ability to provide resources -​ Males produce smaller, less energetically costly gametes. a)​ Male reproduction thought to be limited by access to mates Natural Selection Selection for attributes (physical or behavioral) that contribute to fitness. Sexual Selection Selection for attributes (physical or behavioral) that contribute to reproductive advantage. Two distinct processes generate sexual selection and result in differences in mating success: -​ Intrasexual Selection = Individuals of one sex compete among themselves for mates. -​ Intersexual Selection = Individuals of one sex consistently choose mates among members of opposite sex based on a particular trait. Runaway sexual selection posits that extreme male traits can evolve through a process in which the male trait and the female preference for that trait become genetically linked. The male trait does not necessarily have to be beneficial to the male in any way, it only has to attract females...and increase the male’s reproductive success Why did the Irish Elk go extinct? Trade-offs are common in nature!  -​ Sexual selection for elaborate traits, such as enormous antlers or bright coloration, may be balanced by other sources of natural selection such as food acquisition or predator avoidance Evolution of sociality (group living) is generally accompanied by: -​ Cooperative feeding -​ Defense of the social group. -​ Restricted reproductive opportunities. Cooperation generally involves exchanges of resources or other forms of assistance. Highest Degree of Sociality Eusociality (= true sociality) Three major characteristics: 1)​ Individuals of more than one generation living together. 2)​ Cooperative care of young. 3)​ Division of individuals into non-reproductive and reproductive castes. Naked mole rat – the only known eusocial mammal Benefits of group living: -​ Greater acces 2 food -​ Greater protec from predators Costs of group living: -​ Often, only a few individuals in the group reproduce and everyone else helps them raise the young. -​ The increased fitness of a few mating individuals occurs at the expense of the fitness of the helping individuals. -​ In fitness terms, this is a BIG cost. Does this defy the premises of evolution through natural selection? Does the eusocial reproductive system –with only a few individuals reproducing - defy the premises of evolution through natural selection? NO Cooperative behaviors pose an evolutionary dilemma- if natural selection selects individuals who leave the most offspring (i.e. those with the highest fitness ), then how can cooperative behavior that may limit the reproductive output of some individuals evolve? -​ The concepts of inclusive fitness and kin selection help explain the evolution of cooperative behavior, so that it does NOT defy the premises of evolution through natural selection. Inclusive fitness = calculating fitness to include not only your own reproduction but also that of your genetic relatives. Cooperation may not improve your individual fitness but your inclusive fitness.  -​ includes not only your own reproduction but that of your genetic relatives Kin selection = selection in which individuals increase their inclusive fitness by helping increase the survival of relatives (kin) that are not their own offspring. -​ provides an explanation of how cooperation can evolve through the process of natural selection.