1. Free recall - Outline on the white boards
What happens during Photosynthesis
What happens during respiration
Diagrams, key words, enzymes

3. Main stages of the Light Independent Reaction (Calvin Cycle) - Stroma
Carbon dioxide fixation – Ribulose bisphosphate carboxylase is used to add a carbon atom to 5C RuBP.
An unstable 6C molecule is formed and splits to make Glycerate-3-phosphate.(GP)
The GP is then reduced using ATP and NADPH to make Glyceraldehyde phosphate (GALP).
2 molecules of GALP leave the Calvin Cycle and combine to make a 6C organic molecule  monosacharide and amino acids.
ATP is then used to regenerate RuBP. GP
GALP

4. Glycolysis is the first step in respiration
Glycolysis is the breakdown of one molecule of glucose (6C) into two molecules of pyruvate (2 x 3C) with a small net yield of ATP (2 molecules of ATP)
This process also results in the reduction of two hydrogen acceptors (NAD+) to form 2 molecules of NADH + H+
2ATP
2 ADP
Energy to get reactions started
pyruvate 3C
glucose 6C
pyruvate 3C
2ATP
2 ADP
2 ADP
2ATP

5. Happens in the matrix of the mitochondria
The Link Reaction
Pyruvate (3C)
Decarboxylation
NAD
CO2
By decarboxylase enzymes
Reduced NAD
Happens in the matrix of the mitochondria
Acetyl
(2C)
Coenzyme A

6. The Krebs Cycle Acetyl Coenzyme A (2C) Oxaloacetate (4C) Citrate (6C)
NAD
Reduced NAD
FAD
NAD
Reduced FAD
ReducedNAD
ADP
(4C)
ATP
(5C)
CO2
NAD
ReducedNAD
CO2

11. How ecosystems evolve
Explain how ecosystems can develop over time, including the use of the terms colonisation and succession and types of climax communities.

12. Succession refers to changes in an ecosystem over time

13. Primary succession: The gradual establishment, through stages, of a climax ecosystem, that has not been occupied before.

15. Primary succession will occur after a volcanic eruption

16. Primary succession occurs after a glacier retreats

17. Glacier Bay, Alaska

18. Secondary succession: The reestablishment, through stages, of a climax ecosystem, that has been cleared by natural or human means.

19. Secondary Succession: A bare patch of ground covered in grasses two years later

20. Changes during succession – put the statements in order
A. Bacteria, fungi, insects, small worms add organics to the soil
B. Mid successional plants: grass and low scrubs
C. Climax community: depends largely on climate and edaphic factors
D. Late successional plants: trees
E. Early succession plants: grasses, herbs
F. Pioneer species: lichens and mosses that extract nutrients from dust and bare rock.

21. Changes during succession
F. Pioneer species: lichens and mosses that extract nutrients from dust and bare rock. A. Bacteria, fungi, insects, small worms add organics to the soil E. Early succession plants: grasses, herbs B. Midsuccessional plants: grass and low shrubs D. Late successional plants: trees C. Climax community: depends largely on climate and edaphic factors

22. Secondary Succession
When natural vegetation has been disturbed, removed or destroyed.
Abandoned farms
Burned forests
Heavy pollution
Deforestation
A huge storm

23. Some Definitions:
Sere: Another name for succession. A set of stages of evolution of an ecosystem.
Pioneer stage: First stage in a sere which is dominated by opportunist species. (r-strategists)
Climax community: Populations of organisms living together in the climax stage. (K-strategists)
Climax stage: Final stage in a sere where all species are in balance. For example: A mature forest

24. Pioneer Species
Algae
Mosses
Fungi

25. Pioneer species tend to be r-strategists

26. Climax Species tend to be K-strategists

27. Sequoia (redwood) trees are K-strategists

28. K - strategists

29. Lithosere: Succession on land
The evolution of bare ground to forest.
Pioneer species……………………………………Climax forest

30. Hydrosere: Succession of ponds and lakes to forests.

31. Hydrosere:
The gradual conversion of ponds and lakes to forest ecosystems.
With time ponds and lakes are gradually filled with eroded sediments.
The sediments moves in the shorelines and eventually fills in the lake.
The plant sequence is as follows: lake plants, reeds, grasses, shrubs, & trees.

34. Succession along a beach:
The gradual conversion of sandy beaches and desert margins to forest.
Wind moves sand into dunes
Organic material, seeds, and moisture are blown in behind the dune.
Hardy salt tolerant grasses and vines establish themselves trapping more soil.
Plant succession follows the lithosere.

35. Succession along a beach:

36. Be able to describe and explain the changes during succession.

37. Describe how this graph shows what happens during succession.
Biodiversity
Species richness
Pioneer species

38. The first 23 years there is an increase in pioneer species, low shrubs and herbs. Biodiversity is at its minimum. The pioneer species such as mosses, algae and lichens have a short life-span, they are small in size and they have a high density independent mortality. We call this early succession. As time passes we move into mid-succession, tall shrubs are introduced and there is an increase in the biodiversity of the ecosystem. As organisms die, a number of nutrient cycles take place such as the nitrogen cycle. This helps to add nitrates and organic matter to the soil. As the soil becomes more fertile K strategists can take hold. K strategists have a long life span, high dependent density mortality and they tend to have a large adult size. This might occur between 108 – 15,00 years. As species richness and bioviersity increases we have arrived at a climax community.

40. Climatic factors Precipitation Temperature
Insolation (Incoming Solar Radiation)

41. Edaphic Factors
Factors having limiting affects on plant growth that are not climatic. Soil Factors Examples: Alkalinity of soil Extreme acidity Iron toxicity Zinc deficiency Low nutrients in soil

42. Rate of Primary Succession
Primary succession is fastest in humid tropics.
It is slowest in the dry polar areas.
Why?

43. Succession after a forest fire

44. Secondary Succession after a fire
Nutrient release to soil
Regrowth by remnant roots and seeds
Invasions from neighboring ecosystems
Rapid restoration of energy flow and nutrient cycling

47. Secondary succession after farming

49. Changes during succession
Biomass increases
Resource allocation; nutrients initially stored in soils become stored in vegetation.
Mineral cycling slows

50. Changes in Energy Flow
Trophic levels increase from 2 levels to 4 -5 levels.
More trophic levels transfer more energy.
Food webs become more complex.
The total productivity of an ecosystem increases.
Biomass and biodiveristy is maximized in a climax ecosystem.

51. Essay Questions
Describe what happens during primary succession [5 marks]
Describe what happens during secondary succession [5 marks]
Explain how succession can be interrupted and how this can eventually lead to a climax community. Include examples [5 marks]
Outline the key differences between r and K stragestists in stabilising an ecosystem after succession. [5 marks]
Use the textbooks to help you with these:
Pages 269 – 273 of Hodder Biology 2
Pages 248 – 249 of Edexcel Questions

52. Changes in Productivity

53. Abiotic Changes pH: 8  5.5 N: increases C: increases
Exchangeable ions decrease

54. Know the factors affecting the nature of climax communities.

55. The Nature of climax communities.
The system is in a stable equilibrium
Remember the system is open
Matter and energy may cross system boundary.
Inputs are in proportion to outputs.
The system changes less thus keeping habitats intact over time.

56. The Climax Community:
Specialization is encouraged as all niches are occupied.
Each species must enhance competitive abilities and take care of young.
High nutrients available (but used) due to large amounts of biomass.
High moisture available as forests capture their own transpiration and encourage rain.

57. Climax Community: Mineralized nutrients (Nitrogen) increases.
Organic matter in the soil increases
Mineral cycling decreases as plants are adapted to maintaining themselves and not growing or establishing themselves.
These nutrients become less available to plants as they adhere to soil particles or are stored as dead matter in ground.

58. Features of Climax Communities
Greater biomass
Higher levels of species diversity
More favourable soil conditions
Better soil structure
Lower pH
Taller and longer living plant species
More K-strategists / fewer r-strategists
More complex
Greater habitat diversity
Steady-state equilibrium

59. Compare early to late succession [6 MARKS] 1 MARK FOR EACHCOMPARISON – DO THIS IN THE BACK OF YOUR EXERCISE BOOKS
Biomass
Productivity
Food chains
Species diversity
Niche specialization
Feeding relationships
Size of individuals
Life cycles
Population control mechanisms
Fluctuation
Mineral cycles
Stability

60. Food chains Short Long, complex Species diversity Low High
Early succession Late succession
Biomass small High
Productivity high Low
Food chains Short Long, complex
Species diversity Low High
Niche specialization Broad Narrow
Feeding relationships General Specialized
Size of individuals Smaller Larger?
Life cycles Short Long
Population control density density
independent dependent
Fluctuation More Less pronounced
Mineral cycles Open Tend to be closed
Stability Low High

61. Food chains Short Long, complex Species diversity Low High
Early succession Late succession
Biomass small High
Productivity high Low
Food chains Short Long, complex
Species diversity Low High
Niche specialization Broad Narrow
Feeding relationships General Specialized
Size of individuals Smaller Larger?
Life cycles Short Long
Population control density density
independent dependent
Fluctuation More Less pronounced
Mineral cycles Open Tend to be closed
Stability Low High

62. Key Features of early and late succession
Organic matter
Nutrients
Nutrient cycle
Niches
Size of organisms
Life cycles
Growth form
Diversity
Stability
Early
Late
Small External Closed Large Internal Narrow
Wide Complex Small r-species k-species low
High poor good

63. Changes in succession Feature Early Late Organic matter Small Large
Nutrients
External
Internal
Nutrient cycle
Open
Closed
Niches
Wide
Narrow
Size of organisms
Life cycles
Simple
Complex
Growth form
R-species
K-species
Diversity
Low
High
Stability
Poor
Good

64. Plagioclimax
Interrupted succession is known as a plagioclimax.

65. Getting our folders organised
Core practical's (in order)
End of units tests
Practice exam questions
Full past papers
Now you should look through Paper 2 and use the mark scheme to fully annotate your papers.
I will be calling a few of you up to go through your homework questions.

66. Topic 2 - Essay question practice
1. (a) Explain what is meant by the terms ecological succession, pioneer community and climax community. (6) (b) For a named ecosystem, describe how the abundance of the different species of organisms present changes during the various stages of succession. (5) (c) Describe and explain how gross primary productivity changes during the stages of succession. Expression of ideas (3) (Total 20 marks)

67. 1. (a) ecological succession [2 max] the (orderly) process of change over time in a community/ ecosystem/OWTTE; changes in organisms may be associated with changes in abiotic environment (e.g. soil, microclimate); successive communities displace each other through competition; e.g. volcanic island developing into tropical rainforest;
pioneer community [2 max] the first organisms to colonize a new environment; usually dominated by producers/plants; usually dominated by r-strategists; pioneer communities often very simple in structure/low diversity; tolerate harsh conditions e.g. strong light/low nutrient levels; e.g. community of lichens covering bare rock (lithosere);
climax community [2 max] the end-point of ecological succession; in equilibrium/relatively stable; may have a high level of complexity; usually dominated by K-strategists; characteristics of climax community determined by climate and soil; e.g. mature woodland/rainforest ecosystem; Any other reasonable points. 6 max

68. (b) name of ecosystem; e. g
(b) name of ecosystem; e.g. sand dune succession on coast of Western Australia Name must be reasonably detailed, e.g. “freshwater” is not insufficient. pioneer species very low in number initially; but numbers increase rapidly with lack of competition; then decrease later as other species displace them; rarely reaching their full carrying capacity; changing abundance follows a J-curve; eventually climax species become established; their numbers increase slowly to maximum/carrying capacity; changing abundance follows an S-curve; examples of named species showing these changes; 5 max Award [1] for each of the above [4 max]. Any other reasonable points, but they must refer to relative abundance of species, not to diversity for award of credit.

69. (c) gross primary productivity (GPP) – the total amount of organic matter produced/solar energy fixed by photosynthesizing plants per unit area per unit time/OWTTE; gross productivity initially absent/very low; due to initial absence of photosynthesizing organisms; increases through pioneer stage as colonization by photosynthesizing plants increases; and structural complexity/number of layers increases; as green plant biomass increases, gross primary productivity increases; GPP usually at its maximum at climax; GPP is limited at climax by abiotic factors e.g. nutrients/ sunlight/temperature/water; in some cases GPP declines slightly as older/more woody plants dominate; productivity varies seasonally; productivity may be affected by human interference; 6 max Any other reasonable points. Some of the points above may be scored by means of suitably labelled graphs/diagrams. Do not accept references to secondary productivity or net primary productivity.

70. Predation
When one animal (or, occasionally, a plant) hunts and eats another animal.
Often controlled by negative feedback mechanisms.
Simulation of Predator-Prey cycle:

71. Predator-prey cycles Snowshoe hare and Canadian Lynx
Sketch the graph and explain what is happening.

72. Parasitism
One organism benefits (the parasite) at the expense of another (the host) from which it derives food.
Ectoparasites live on the surface of their host (e.g. tapeworms)

73. Mutualism
Symbiosis is a relationship in which two organisms live together (parasitism is a form of symbiosis where one of the organisms is harmed)
Mutualism is a symbiotic relationship in which both species benefit – for example Coral reefs and lichens.

74. Exam Qs
1. Which interaction would benefit both organisms in a relationship? A. Predation B. Commensalism C. Mutualism D. Competition (Total 1 mark)

75. Exam Qs
1. Which interaction would benefit both organisms in a relationship? A. Predation B. Commensalism C. Mutualism D. Competition (Total 1 mark)

76. 2. Most food chains seldom have more than four trophic levels because
A. in most ecosystems, competition for food is very great.
B. the total biodiversity in any ecosystem is limited.
C. energy is lost as it moves along a food chain and little remains at the level of the top carnivore.
D. in many parts of the world, many species have become extinct and complex ecosystems are rare.
(Total 1 mark)

77. 2. Most food chains seldom have more than four trophic levels because
A. in most ecosystems, competition for food is very great.
B. the total biodiversity in any ecosystem is limited.
C. energy is lost as it moves along a food chain and little remains at the level of the top carnivore.
D. in many parts of the world, many species have become extinct and complex ecosystems are rare.
(Total 1 mark)

79. A

80. 4. An ecological niche is A. where a species lives. B
4. An ecological niche is A. where a species lives. B. all the populations of an ecosystem. C. what a species eats. D. the role a species has in an ecosystem. (Total 1 mark)

81. 4. An ecological niche is A. where a species lives. B
4. An ecological niche is A. where a species lives. B. all the populations of an ecosystem. C. what a species eats. D. the role a species has in an ecosystem. (Total 1 mark)

82. 5. An ecological niche is
A. where a species lives and what it does in its environment.
B. the specific location of a species.
C. the general type of ecosystem where a species is found.
D. the type of burrow where a species lives.
(Total 1 mark)

83. 5. An ecological niche is
A. where a species lives and what it does in its environment.
B. the specific location of a species.
C. the general type of ecosystem where a species is found.
D. the type of burrow where a species lives.
(Total 1 mark)

85. C

87. D

88. 8. Which of the following statements about food chains is true. A
8. Which of the following statements about food chains is true? A. Herbivores are usually found at the third trophic level. B. Carnivores are never at the second trophic level. C. Primary producers can be found at any trophic level. D. Secondary consumers are at the second trophic level. (Total 1 mark)

89. 8. Which of the following statements about food chains is true. A
8. Which of the following statements about food chains is true? A. Herbivores are usually found at the third trophic level. B. Carnivores are never at the second trophic level. C. Primary producers can be found at any trophic level. D. Secondary consumers are at the second trophic level. (Total 1 mark)