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

2. 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

3. 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

4. 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

5. 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)

6. 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

7. 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

8. 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)

9. 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

10. 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

11. 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

12. 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

13. 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

14. 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

15. 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

16. 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

17. 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

18. 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

19. 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