Big Idea 2 2.A: Growth, reproduction, and maintenance of the organization of living systems require free energy and matter.

An Introduction to Metabolism (chapter 8) Metabolism: The totality of an organism’s chemical processes; managing the material and energy resources of the cell Arises from interactions between molecules w/in the cell Bioenergetics: How organisms manage their energy resources

Catabolic pathways: degradative process such as cellular respiration; releases energy which is now available for work ex. Transport, ciliary beating Anabolic pathways: aka biosynthetic pathways - building process; Consumes energy Ex. protein synthesis, photosynthesis

Thermodynamics – study of E transformations Energy (E)~ capacity to do work (cause change) Kinetic energy~ energy of motion; Heat(thermal energy) – associated with random movement of molecules Potential energy~ stored energy – chemical energy – due to location/structure Closed system vs open system 1st Law: conservation of energy; E transferred/transformed, not created/destroyed 2nd Law: transformations increase entropy (disorder, randomness) All energy is not used, some is released as heat. Living systems increase entropy in their surroundings Combo: quantity of E is constant, quality is not Energy flows in as light and leaves in the form of heat

Free energy (G) Free energy: portion of system’s E that can perform work (at a constant T) ∆G = ∆H - t ∆s Change in free e = enthalpy – (Temp x change in entropy) Enthalpy: total E ∆G = G final state – G initial state Use ∆G to determine if a process will be spontaneous (occur on its own) or nonspontaneous (needs E added to occur)

Exergonic reaction: net release of free E to surroundings – causes a decrease in G; ∆G if negative = spontaneous Endergonic reaction: absorbs free E from surroundings – stores free E; ∆G is positive = nonspontaneous Closed systems reach equilibrium – can do no work A cell at equilibrium is dead Living organisms have a constant interaction w/ environment – this keeps pathways from reaching equilibrium

Energy Coupling & ATP E coupling: use of exergonic process to drive an endergonic one (ATP) Adenosine triphosphate – primary source of all E ATP tail: high negative charge ATP hydrolysis (use of water to break apart molecules) : releases free E Phosphorylation (phosphorylated intermediate)~ enzymes – transfer of a phosphate group to another molecule – transfers E

Metabolism: sum of all energy-requiring biochemical reactions (chapter 40) Catabolic processes of cellular respiration Calorie (cal);kilocalorie(kcal or C) Bioenergetics – flow of energy through an animal Harvest energy from food they eat – 1st used for cellular resp then biosynthesis Endotherms: bodies warmed by metabolic heat – high energy strategy – birds, mammals Ectotherms: bodies warmed by environment – smaller energy cost – fish, amphibians, reptiles Basal Metabolic Rate (BMR): minimal rate powering basic functions of life (endotherms) Standard Metabolic Rate (SMR): minimal rate powering basic functions of life at a particular temp (ectotherms)

Excess/insufficient g (free energy) G greater than required for smr/bmr used for growth or energy storage Reproduction – requires much additional g Species try to limit this extra requirement in different ways Seasonal, biennial, reproductive diapause (arrested development of sex cell production/hormone production) May lead to increases in population size G lower than required for smr/bmr May lead to cell death = loss of mass or possible death to the organism May lead to decreases in population size

Ecosystems, Energy, and Matter (chapter 54) An ecosystem consists of all the organisms living in a community As well as all the abiotic factors with which they interact Ecosystems can range from a microcosm, such as an aquarium To a large area such as a lake or forest Regardless of an ecosystem’s size Its dynamics involve two main processes: energy flow and chemical cycling Energy flows through ecosystems While matter cycles within them

ecologists view ecosystems As transformers of energy and processors of matter The laws of physics and chemistry apply to ecosystems Particularly in regard to the flow of energy Energy is conserved But degraded to heat during ecosystem processes Energy and nutrients pass from primary producers (autotrophs) To primary consumers (herbivores) and then to secondary consumers (carnivores) A change in the free energy can lead to a change in other levels

Energy flows through an ecosystem Entering as light and exiting as heat Figure 54.2 Microorganisms and other detritivores Detritus Primary producers Primary consumers Secondary consumers Tertiary consumers Heat Sun Key Chemical cycling Energy flow

Primary production in an ecosystem Is the amount of light energy converted to chemical energy by autotrophs during a given time period Ecosystem Energy Budgets The extent of photosynthetic production Sets the spending limit for the energy budget of the entire ecosystem The Global Energy Budget The amount of solar radiation reaching the surface of the Earth Limits the photosynthetic output of ecosystems Only a small fraction of solar energy Actually strikes photosynthetic organisms

Total primary production in an ecosystem = gross primary production (GPP) Not all of this production Is stored as organic material in the growing plants Net primary production (NPP) = GPP minus the energy used by the primary producers for respiration Only NPP Is available to consumers

Different ecosystems vary considerably in their net primary production And in their contribution to the total NPP on Earth Lake and stream Open ocean Continental shelf Estuary Algal beds and reefs Upwelling zones Extreme desert, rock, sand, ice Desert and semidesert scrub Tropical rain forest Savanna Cultivated land Boreal forest (taiga) Temperate grassland Tundra Tropical seasonal forest Temperate deciduous forest Temperate evergreen forest Swamp and marsh Woodland and shrubland 10 20 30 40 50 60 500 1,000 1,500 2,000 2,500 5 15 25 Percentage of Earth’s net primary production Key Marine Freshwater (on continents) Terrestrial 5.2 0.3 0.1 4.7 3.5 3.3 2.9 2.7 2.4 1.8 1.7 1.6 1.5 1.3 1.0 0.4 125 360 3.0 90 2,200 900 600 800 700 140 1,600 1,200 1,300 250 5.6 1.2 0.9 0.04 22 7.9 9.1 9.6 5.4 0.6 7.1 4.9 3.8 2.3 65.0 24.4 Figure 54.4a–c

Energy transfer between trophic levels is usually less than 20% efficient The secondary production of an ecosystem = the amount of chemical energy in consumers’ food that is converted to their own new biomass during a given period of time When a caterpillar feeds on a plant leaf Only about one-sixth of the energy in the leaf is used for secondary production The production efficiency of an organism = the fraction of energy stored in food that is not used for respiration

Usually ranges from 5% to 20% Trophic efficiency Is the percentage of production transferred from one trophic level to the next Usually ranges from 5% to 20% This loss of energy with each transfer in a food chain Can be represented by a pyramid of net production Figure 54.11 Tertiary consumers Secondary Primary producers 1,000,000 J of sunlight 10 J 100 J 1,000 J 10,000 J

One important ecological consequence of low trophic efficiencies Can be represented in a biomass pyramid Most biomass pyramids Show a sharp decrease at successively higher trophic levels Figure 54.12a (a) Most biomass pyramids show a sharp decrease in biomass at successively higher trophic levels, as illustrated by data from a bog at Silver Springs, Florida. Trophic level Dry weight (g/m2) Primary producers Tertiary consumers Secondary consumers Primary consumers 1.5 11 37 809

Certain aquatic ecosystems Have inverted biomass pyramids Figire 54.12b Trophic level Primary producers (phytoplankton) Primary consumers (zooplankton) (b) In some aquatic ecosystems, such as the English Channel, a small standing crop of primary producers (phytoplankton) supports a larger standing crop of primary consumers (zooplankton). Dry weight (g/m2) 21 4