1. Energy Flow in Ecosystems
Semester 1: Unit 2:
Energy Flow in Ecosystems

2. Obtaining and Using Energy

3. What do you know? What is energy? What do you need energy for?
How does your body use/store energy?

4. What is energy?

5. Energy is the ability to do work.
Without ability to obtain & use energy, life would NOT exist.
One of the most important compounds that cells use to store & release energy is adenosine triphosphate (ATP).

6. ATP consists of:
-adenine (nitrogenous base)
-a 5-carbon sugar called ribose
- three phosphate groups

7. ATP can easily release and store energy by breaking and re-forming the bonds between its phosphate groups.
This characteristic makes ATP very useful as a basic energy source for cells

8. Storing Energy
Adenosine diphosphate (ADP) -has 2 phosphate groups instead of 3.
-contains some energy (not as much as ATP)
When a cell has energy available, it stores small amounts by adding a phosphate group to ADP, making ATP.
ADP is like a rechargeable battery that powers the cell.

9. Releasing Energy
Cells release the energy stored in ATP by breaking the bonds between the 2nd & 3rd phosphate groups.
A cell can add (+) or subtract (-) these phosphate groups giving it an easy way of storing & releasing energy as needed.

10. Storing Energy
*ADP into ATP=
stored energy
(fully charged
battery)

11. Intro to Photosynthesis

12. Types of Organisms
Autotrophs- organisms that make their own food (carry out photosynthesis)
Ex: plants, algae, some bacteria
Heterotrophs- organisms that obtain food by consuming other living things
Ex: humans, insects, cheetah, mushroom, etc

13. Photosynthesis During photosynthesis-
organisms convert energy from sunlight into chemical energy stored in the bonds of carbohydrates.

14. Energy from the sun travels to Earth in the form of light
Sunlight is a mixture of different wavelengths & make up a color spectrum. (ROYGBIV)

15. Plants gather the sun’s energy with light-absorbing molecules- pigments.
plants’ main pigment is chlorophyll
2 types in plants: - chlorophyll a
- chlorophyll b
Both chlorophylls absorb light in the blue- violet & red regions of the spectrum

16. Green plants do NOT absorb in the green region
have chlorophyll b which reflects green light, which is why plants look green.

17. Red plants do NOT absorb in the red region
have chlorophyll a which reflects red light, which is why plants look red.

18. Why to leaves change in the fall?
Leaves turn red from green during the fall because chlorophyll b breaks down, leaving other pigments to show their colors

19. Photosynthesis uses the energy of sunlight to convert water & carbon dioxide into high-energy sugars & oxygen.

20. Photosynthesis involves 2 reactions sets:
1- light-dependent reactions
2- light-independent reactions (Calvin cycle)

21. Light-Dependent Reactions:
Water & light energy = in
Oxygen, ATP, & NADPH = out

22. Light-Independent Reactions (Calvin cycle):
CO2, ATP & NADPH = in
high energy sugars/carbohydrates = out

23. Factors Affecting Photosynthesis
The 3 main factors that affect photosynthesis are:
Temperature
Light intensity
Availability of water

24. Temperature:
photosynthesis reactions are due to enzymes that function between 0°C & 35°C
Temps above or below that range may slow down the rate of photosynthesis or stop it entirely.

25. Light: High light intensity increases rate of PS.
After light intensity reaches a certain level, plants reach the maximum rate of PS.

26. Water: Water shortage can slow or stop PS.
Water loss can also damage plant tissues.
Plants living in dry conditions have waxy coatings on leaves to reduce water loss.
Too much water can drown plants

27. Intro to Cellular Respiration

28. Cellular Respiration

29. Heterotrophs get energy from food.
Food molecules release chemical energy when chemical bonds break.
Cells break down food & use the stored energy to produce ATP to power the cell’s activities.

30. Occurs in the mitochondria of a cell Chemical equation (symbols):
Cellular respiration- releases energy from food in the presence of oxygen.
Occurs in the mitochondria of a cell
Chemical equation (symbols):
6 O2 + C6H12O6  6 CO2 + 6 H2O + Energy
In words:
Oxygen + Glucose Carbon dioxide + Water + Energy

31. Cellular Respiration:
3 stages (in order) are:
1- Glycolysis
2- Krebs cycle
3- Electron Transport
Chain (ETC)

32. What do you notice about PS and CR?
They are opposites!

33. Photosynthesis & cellular respiration are opposite processes.
PS removes CO2 from the air; CR returns it.
PS releases O2 into the air; CR uses O2 from air to release energy from food.
PS “deposits” energy & CR “withdraws” it.
The reactants of CR are the products of PS & vice versa.

34. Release of energy by
cellular respiration-
in plants, animals,
fungi, protists, most
bacteria.
Energy capture by
photosynthesis-
in plants, algae,
& some bacteria.

35. Intro to Fermentation

36. Fermentation

37. Aerobic- process that requires oxygen
Krebs cycle & ETC are aerobic processes.
Krebs & ETC take place inside the mitochondria.
Anaerobic- does not require oxygen
Glycolysis is an anaerobic process.
Glycolysis takes place in the cytoplasm.

38. -Alcoholic Fermentation -Lactic Acid Fermentation
Fermentation - energy is released from food molecules in the absence of oxygen.
occurs in the cytoplasm of cells.
2 types of Fermentation exist:
-Alcoholic Fermentation
-Lactic Acid Fermentation
Under anaerobic conditions, fermentation follows glycolysis.

39. Alcoholic Fermentation:
Yeast & a few other microorganisms use alcoholic fermentation to produce ethyl alcohol & carbon dioxide.
used to produce alcoholic beverages & causes bread dough to rise.
Chemical equation:
Glucose→ Pyruvic acid + NADH  Alcohol + CO2 + NAD+

40. Lactic Acid Fermentation
Carried out best by human muscle cells under oxygen deprivation.
Lactic Acid is a toxin and causes fatigue, soreness and stiffness in muscles that have been overworked.
Chemical equation:
Glucose → Pyruvic acid + NADH  Lactic acid + NAD+

41. Lactic Acid & Exercise
For this sudden burst of energy, cells use the small amount of ATP they can normally conserve. This supply runs out in seconds.
Then fermentation kicks in to produce more ATP for energy, producing lactic acid as a byproduct.
With the build up of lactic acid in the body system the only way to get rid of it is adding LOTS of oxygen.
This is why heavy breathing is necessary after a race!

42. During fermentation, cells convert NADH made by glycolysis back into the electron carrier NAD+, allowing glycolysis to continue producing ATP.

43. Energy Flow
We’ve learned how energy gets into the cycle of life and used by organisms, but how does it move between living things? How do you think it works? How does an insect get energy? How does a wolf get energy?

44. Intro to Energy Flow

45. Sunlight is the ultimate energy source
Consider This:
Where does the electrical energy needed to power the lights in this room come from? What do you think?
How it works:
Electricity is generated at a thermal power plant by burning coal.
What is coal? A fossil fuel!
Fossil fuels are literally highly pressurized remains of dinosaurs/ancient organisms
Where did the dinosaurs get their energy? Eating plants!
Where did the plants get their energy? The SUN!!!

46. Types of Organisms in an Ecosystem
Autotrophs - capture energy from sunlight or chemicals & convert it into forms that living cells use (primary producers).
Use Photosynthesis
Primary Productivity- rate at which primary producers create organic material.

47. Types of Organisms in an Ecosystem
Heterotrophs (consumers)- get energy & nutrients by ingesting other organisms
Decomposers- Decomposers break down material and make it available for producers to use. (Type of heterotroph)

48. Energy flows in one direction in an ecosystem:
producers → consumers
food chain- series of steps in which organisms transfer energy by eating & being eaten.
food web- all food chains in an ecosystem

50. Pyramid of Energy:
most of the energy used on life processes
Remaining energy released as heat
ONLY 10% of the energy available from 1 level is transferred to the next level.

51. Ex: many insects graze on 1 tree: lots of biomass, 1 organism.
Pyramids of Biomass or Numbers:
At times, consumers are smaller in size than the organisms they feed upon.
Ex: many insects graze on 1 tree: lots of biomass, 1 organism.
pyramid of numbers may be upside down

52. Intro to Nutrient Cycles

53. Nutrient Cycles
nutrients- chemical substances organism needs to sustain life
limiting nutrient -nutrient whose supply limits productivity because it is scarce or cycles slow

54. Unlike the 1-way flow of energy, matter (nutrients) are recycled within & between ecosystems.
biogeochemical cycles- pass elements from 1 organism to another & through the biosphere due to energy
matter involved in biological processes, geological processes, & chemical processes.
**Matter is never created or destroyed, only changed!

55. The Carbon Cycle:
Plants take in CO2, build carbohydrates, & pass it through food webs
animals release CO2 by respiration
organisms die, decomposers break them down, & release C in environment
Geologic forces turn C into fossil fuels/rock
The Ocean absorbs a lot of the C in the atmosphere

56. The Carbon Cycle:
C enters atmosphere by volcano & human- activity- burning of fossil fuels, forests