1. COMMUNITIES and ECOSYSTEMS
Topic 5.1
IB Biology
Miss Werba

2. TOPIC 5 – ECOLOGY and EVOLUTION
5.1 COMMUNITIES and ECOSYSTEMS
5.2
THE GREENHOUSE EFFECT
5.3
POPULATIONS
5.4
EVOLUTION
5.5 CLASSIFICATION
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3. THINGS TO COVER Ecological definitions Autotrophs & heterotrophs
Consumers, detritivores & saprotrophs
Food chains & webs
Trophic levels
Initial energy source for most communities
Energy flow & energy transformations
Energy pyramids
Nutrient recycling
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4. ECOLOGICAL DEFINITIONS
5.1.1
ECOLOGICAL DEFINITIONS
Ecology:
The study of the relationships between living organisms and between organisms and the environment
Species:
A group of organisms that can interbreed and produce fertile offspring
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5. ECOLOGICAL DEFINITIONS
5.1.1
ECOLOGICAL DEFINITIONS
Habitat:
The environment in which a species normally lives or the location of a living organism
Population:
A group of organisms of the same species who live in the same area at the same time
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6. ECOLOGICAL DEFINITIONS
5.1.1
ECOLOGICAL DEFINITIONS
Community:
A group of populations living and interacting with each other in a particular area
Ecosystem:
A community (biotic) and its abiotic environment
Tempe-rature
Light
Water
Humidity pH
Nutrients
Wind
Tides
Turbidity
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7. CLASSIFYING ORGANISMS: Source of Energy
5.1.2
CLASSIFYING ORGANISMS: Source of Energy
Autotroph:
An organism that synthesises its organic molecules from inorganic substances
Photosynthesis
Heterotroph:
An organism that obtains its organic molecules from other organisms
Digestion
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8. CLASSIFYING ORGANISMS: Manner of Consumption
5.1.3
CLASSIFYING ORGANISMS: Manner of Consumption
Producer:
Do not consume!
An autotroph
Produces its own organic matter
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9. CLASSIFYING ORGANISMS: Manner of Consumption
5.1.3
CLASSIFYING ORGANISMS: Manner of Consumption
Consumers:
An organism that ingests other organic matter that is living or recently killed
Classified by what they eat:
can be herbivores, omnivores or carnivores
Also classified according to their level in the food chain:
can be primary, secondary or tertiary consumers
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10. 5.5.2
DIET
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11. 5.5.2
DIET
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12. 5.5.2
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13. CLASSIFYING ORGANISMS: Manner of Consumption
5.1.3
CLASSIFYING ORGANISMS: Manner of Consumption
Decomposers: organisms that decompose organic material eg. bacteria and fungi
Detritivores
An organism that ingests non-living organic matter
Saprotroph
An organism that lives on or in non-living organic matter, secreting digestive enzymes into it and absorbing the products of digestion
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14.
FOOD CHAINS & WEBS
The feeding relationship between species in an ecosystem is represented as a food chain.
The transfer of energy and matter are represented by arrows:
they point in the direction of energy flow
ie. to the eater!
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15.
FOOD CHAINS & WEBS
Trophic level: the position that an organism occupies in a food chain or web
In general:
1st TL = producer or autotroph
2nd TL = primary (1°) consumer, first-order consumer or herbivore
3rd TL = secondary (2°) consumer, second-order consumer or carnivore
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16.
FOOD CHAINS & WEBS
Food chains represent a linear relationship between organisms.
Food webs represent interconnected relationships between organisms.
Food webs are more realistic as there is rarely one predator to any one prey.
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17. FOOD CHAINS & WEBS Example: Food Webs Example: Food Chains
FOOD CHAINS & WEBS
Example: Food Webs
Example: Food Chains
Water weed  Pond Flies  Frog  Kingfisher
Carrot plant  Carrot fly  Flycatcher  Sparrow hawk
Bushgrass  Impala  Cheetah  Lion
Buckwheat  Gopher  Gopher snake  Red tailed kite
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18. ENERGY FLOW Command term: STATE
ENERGY FLOW Command term: STATE
Sunlight is the initial energy source for most communities.
Autotrophs convert light energy into organic matter via photosynthesis
Heterotrophs consume this organic matter
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19. ENERGY FLOW Command term: STATE
ENERGY FLOW Command term: STATE
Only ~10% of the energy is passed from one trophic level to the next
The rest is lost!
How is it lost?
heat
used in cellular respiration
trapped in bones/faeces, etc
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20.
ENERGY FLOW
Because 90% of the energy is lost, it has a limiting effect on the number of organisms that can exist in a food chain.
Results in competition for resources
Therefore, fewer organisms can be supported in each successive trophic level.
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21. 5.1.12
ENERGY PYRAMIDS
Used to represent the amount of energy at each level of a food chain
Appear as a pyramid because higher trophic levels always have ~90% less energy than preceding levels.
The units are kJ/m2/yr
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22. NUTRIENT RECYCLING Command term: STATE–
NUTRIENT RECYCLING Command term: STATE
Energy can enter and leave an ecosystem – energy is not recycled!
Conversely, nutrients have to be recycled through ecosystems.
Decomposers (saprotrophic bacteria and fungi) recycle nutrients by returning them to the soil for plants to use.
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23. –
NUTRIENT RECYCLING C
H2O N
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24. THE CARBON CYCLE Linked closely to Topic 5.2 - The Greenhouse Effect
5.1.13
THE CARBON CYCLE
Linked closely to Topic The Greenhouse Effect
Carbon is removed from the environment by:
Photosynthesis, absorption in seawater, formation of carbonate rocks, use of carbonates in the shells of shellfish
Carbon is introduced to the environment by:
Respiration, volcanic eruptions, burning fossil fuels, breakdown of carbonates, deforestation
Currently, the human race cannot remove carbon as readily as we are introducing it…increasing CO2 levels in the atmosphere and causing the Greenhouse effect
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25. ?

26. V = 500 kg, W = 600 kg, X = 5000 kg, Y = 50 kg, Z = 5 kg
Sample questions Q1
In an area of an ecosystem, a biologist estimated the following biomasses (V to Z represent populations of particular species):
V = 500 kg, W = 600 kg, X = 5000 kg, Y = 50 kg, Z = 5 kg
Which of the following represents a possible food chain in this ecosystem?
V ➝ W ➝ X ➝ Y
Z ➝ Y ➝ V ➝ X
Z ➝ Y ➝ X ➝ W
X ➝ V ➝ Y ➝ Z
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27. seagrass (pop1) ➝ fish (pop2) ➝ pelicans (pop3)
Sample questions Q2
seagrass (pop1) ➝ fish (pop2) ➝ pelicans (pop3)
The diagram shows three populations that make up a food chain. If a new predator moves in that also feeds on fish, what might happen to the numbers in the three populations?
Numbers in all three populations decline.
Numbers in population 2 decline but 1 and 3 increase.
Numbers in population 1 increase but 2 and 3 decline.
Numbers in population 2 decline but 1 and 3 stay the same.
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28. Sample questions
A1. D A2. C
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29. Sample questions Q3
Identify the producers, primary consumers, and top-order consumer.
Draw a food chain for this food web that shows the seal in the position of: i. secondary consumer ii. tertiary consumer
Use an example from this food web to explain why food webs are more stable than food chains.
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30. Sample questions A3
Producers: algae (phytoplankton) Primary consumers: zooplankton Top-order consumer: humans
i. secondary consumer algae  zooplankton  seal  human, or algae  zooplankton  seal  husky ii. tertiary consumer algae  zooplankton  fish  seal  human, or algae  zooplankton  fish  seal  husky
Multiple interactions are shown; alternative energy sources would be available if a food chain was interrupted.
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