Summary of the Ecology topic of the IB Biology subject in Standard level.

1. Ecology
Biology IB Standard Level

2. Activity
Using the Oxford
book, read pages
201-210 and look for
the following
definitions in your
notebook (give
examples for
each):
Biotic factors
Abiotic factors
Species
Population
Community
Ecosystem
Habitat
Nutrition
Autotroph
Heterotroph
Producers
Consumers
Scavengers
Detritivores
Saprotrophs
Nutrient cycles

3. Topic outline
Energy flow
Energy transfer
Trophic levels
Food chains
Energy loss
Energy eficiency
Pyramids of energy
Nutrient cycling

4. Organisms require chemical energy (organic
compounds) to fuel cellular processes.
• Autotrophs produce these organic molecules
using an external energy supply.
Light is the initial energy source for almost all
communities.
• Some producers may derive their energy from
chemical processes.
Energy
source

5. Energy conversion: Photosynthesis
Light energy is converted into chemical energy via the
process of photosynthesis
• The chemical energy is stored in carbon compounds
(organic molecules).
Where does
it happen?

6. Energy conversion: Photosynthesis
Light energy is converted into chemical energy via the
process of photosynthesis
• The chemical energy is stored in carbon compounds
(organic molecules).
Where does
it happen?
Chloroplasts

7. Energy conversion: Cell respiration
Energy stored in organic compounds is released via the
process of cell respiration.
• The energy is converted into a usable form (ATP), with
heat as a by-product.
Where does
it happen?

8. Energy conversion: Cell respiration
Energy stored in organic compounds is released via the
process of cell respiration.
• The energy is converted into a usable form (ATP), with
heat as a by-product.
Where does
it happen?
Mitochondria

9. Food chains
Heterotrophs (consumers) acquire organic compounds
through feeding. That's how they get their energy.
Food chains represent the linear feeding relationships
between species.
Arrows represent the transfer of energy and matter as
organisms are eaten.

10. Trophic levels
Trophic level 1 Producer Sunflower
Trophic level 2 Primary consumer Snail
Trophic level 3 Secondary consumer Frog
Trophic level 4 Tertiary consumer Fox
The position of an organism in a feeding sequence in known
as the trophic level.

11. Food webs show inter-related feeding relationships with
multiple food sources.
• One organism may occupy more than one trophic level in
a food web.
Food webs

12. Energy loss
When organisms produce chemical energy (cell
respiration), they also release heat.
• Living organisms cannot convert heat into other forms
of usable energy.
• Hence, thermal energy is lost from an ecosystem.
Chemical energy is
lost to:
- Cellular respiration
- Heat
- Stays unconsumed

13. Energy efficiency
Energy losses between trophic levels resctrict the length
of food chains and the biomass of higher trophic levels.

14. Chi-square test
Statistics test used to test association between 2 variables
(in our case, 2 species).
If there is an association after doing the test, we say that
there is a statistically significant association.
There are 5 simple steps to follow:
• Identify the hypotheses (null and alternative)
• Construct a table of frequencies
• Apply the chi-squared formula
• Determine the degrees of freedom (df)
• Identify the p value (should be <0.05)

15. Chi-square test
Example
The presence or absence of 2 species of plants was
recorded in 50 cuadrats (1m2) on a forest.
The following pattern was observed:
• 6 quadrats = both species
• 15 quadrats = roses only
• 20 quadrats = sunflowers only
• 9 quadrats = neither species

16. Chi-square test
Step 1 = Identify hypotheses
Null hypothesis (h0) = There is no significant difference
between the distribution of two species.
Alternate hypothesis (h1) = There is a significant difference
between the distribution of species

17. Chi-square test
Step 2 = Construct table of frequencies
(observed vs. expected frequencies)
Roses
Sunflowers
Observed frequencies

18. Chi-square test
Step 2 = Construct table of frequencies
(observed vs. expected frequencies)
Roses
Sunflowers
Expected frequencies
Formula to find the
expected frequencies:
(row total x column total)
/ grand total

19. Chi-square test
Step 3 = Apply the chi-squared formula
𝝌2 = Chi-squared value
∑ = Sum
O = Observed frequency
E = Expected frequency

20. Chi-square test
Step 3 = Apply the chi-squared formula
Calculations can be simplified for each part of the frequency table

21. Chi-square test
Step 3 = Apply the chi-squared formula
Based on the numbers obtained, we can calculate the statistical
chi-squared value, like this:
𝝌2 = (2.20 + 2.38 + 1.59 + 1.73) = 7.90

22. Chi-square test
Step 4 = Determine the degree of freedom (df)
In order to determine if the chi-squared value is statistically
significant a degree of freedom must first be identified
• The degree of freedom is a mathematical restriction that
designates what range of values fall within each significance level
The degree of freedom is calculated from the table of frequencies
according to the following formula:
df = (m – 1) (n – 1)
Where: m = number of rows ; n = number of columns
• When the distribution patterns for two species are being
compared, the degree of freedom should always be 1.

23. Chi-square test
Step 5 = Identify the p value
The final step is to apply or compare the
value generated (7.90) to a chi-squared
distribution table to determine if results
are statistically significant.

25. Chi-square test
Step 5 = Identify the p value
A value is considered significant if it is higher than the p value
chosen (p>0,05).
When df = 1, a value of greater than 3.841 is required for results to be considered statistically
significant (p < 0.05)
A value of 7.90 lies above a p value of 0.01, meaning there is less than a 1% probability results are
caused by chance. Hence, the difference between observed and expected frequencies are statistically
significant.

26. Chi-square test
Final step = Reject or accept hypotheses
As the results are statistically significant, the null hypothesis is
rejected and the alternate hypothesis accepted:
Alternate hypothesis (H1): There is a significant difference
between observed and expected frequencies.
Because the two species do not tend to be present in the same
area, we can infer there is no association between them.

27. Chi-square test
Exercise

28. Topic outline
Carbon
cycling
Carbon fixation
Carbon dioxide in solution
Absorption of carbon dioxide
Release of CO2 from cell
respiration
Methanogenesis
Oxidation of methane
Peat formation
Fossilized organic matter
Combustion
Limestone

29. They absorb carbon dioxide from
the atmosphere, which is
converted into carbohydrates,
lipids and the carbon compounds
they need
Carbon fixation
Autotrophs are able to convert carbon dioxide into different carbon
compounds

30. The mean of CO2 is approximetely 0.039%, however, it is lower
above some parts of the earth’s surface with high
photosynthesis rates
Carbon fixation
Effect
The amount of carbon dioxide in the atmosphere is
reduced

31. In aquatic habitats carbon dioxide is present as dissolve gas and hydrogen
carbonate ions .
Carbon Dioxide in solution
Carbonic acid

32. Carbon Dioxide in solution
Carbon Dioxide Can reduce the pH of water
Why?
Because an increase in
CO2 will cause a
decrease in pH

34. Aquatic plants
photosynthesis
Carbon dioxide dissolve
Carbonate Hydrogen ions are absorbed by aquatic plants
Carbohydrates and other carbon comounds are made
Carbon Dioxide in solution

35. Autotrophs: primary producer (plants, bacteria, algae)
Absorption of carbon
dioxide
carbon dioxide diffuses from the atmosphere or water into autotrophs
key
words
Diffusion : the movement of a substance from an area of
high concentration to an area of low concentration

36. Autotrophs use carbon dioxide to produce carbon compounds such
as glucose
Since they are turning the carbon dioxide into other substances, the
concentration inside the autotrophs of carbon dioxide is lower than what it is in
the environment
Absorption of carbon
dioxide
Therefore, the carbon dioxide diffuses from the environment to the autotrophs

37. Absorption of carbon
dioxide
Land plants: the difussion usually happens through the leaves
Aquatic plants: the entire surface of the plant can absorb

38. Release of CO2 from cell
respiration
Diffuses out of the
cells
- Produced by cells
that carry AR.
CO2 - waste product
of aerobic respiration.
Atmosphere
Water surrounding the
organism
Examples on different
trophic levels:
-Root cells(Producers)
- Animal cells (Consumers)
- Fungi (Saprotrophs)
https://www.pinterest.com/pin/344243965243222499/

39. Methane is produced from
organic matter in anaerobic
conditions by archaeans and
some diffuses into the
atmosphere
Methanogenesi
s
https://www.pinterest.com/pin/527624912594875169/

40. 2. Bacteria use the organic
acids and alcohol to produce:
- Acetate
- Carbon dioxide
- Hydrogen
Methanogenesi
s
• Bacteria convert
organic matter into:
- Oganic acids
-Alcohol
-Hydrogen
-Carbon dioxide
3. Archeans produce methane
from carbon dioxide,
hydorgen and acetate

41. Methanogenesi
s
Anaerobic
environments
Mud along the
shores and
lakes Swamps, mangroves
and other wetlands
where the soil is
waterlogged
Guts of
termites and
mammals like
cattle
Sites where
there is
organic waste
https://www.worldatlas.com/articles/what-is-the-importance-of-
swamps.html
https://www.quberenewables.co.uk/new-blog/it-all-ads-up-food-waste-and-landfill-sites
http://www.seetheworldinmyeyes.com/discover-unesco/wadden-sea-a-world-heritage-made-of-
mud/

42. Methane (CH4) is a colorless and odorless gas. It is
abundant in nature and is produced as a product of
certain human activities. It is also one of the most
potent greenhouse gasses.
Oxidation of Methane
Landfills, oil and natural gas
systems, agricultural activities,
coal mining, stationary and
mobile combustion,
wastewater treatment, and
certain industrial processes.

43. "Methane is oxidized to carbon dioxide and water in
the atmosphere"
Methane Oxidation is a microbial metabolic energy producing reaction.
Process:
• Methane molecules (CH4) are released into the atmosphere.
(They stay on the atmosphere for an average of 12 years)
2. The methane molecules react with Oxygen (O2) and turn into Carbon
Dioxide (C02)
Methane is naturally oxidized in the satrosphere
Methane Oxidation Formula

44. This process is important because ...
The process of Methane Oxidation explains why although Methane is a
very abundant gas, its concentration on the atmosphere is relatively
low
This is very important because when Methane is released into the
atmosphere before being burned, it traps heat increasing climate change, so
the less concentration there is, the better.
• https://www.google.com/url?sa=t&rct=j&q=&esrc=s&source=web&cd=&cad=rja&uact=8&ved=2ahUKEwjT46X3-
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environment&usg=AOvVaw2-iKCShFYe9x_f12aSxZTu
• https://www.sciencedirect.com/science/article/abs/pii/S1566736715300108
• https://hips.hearstapps.com/hmg-prod.s3.amazonaws.com/images/gases-by-ch4-2019-caption-1567110765.jpg?resize=480:*
• https://www.google.com/search?client=safari&rls=en&q=what+hman+activities+generate+methane&ie=UTF-8&oe=UTF-8
• https://www.google.com/url?sa=i&url=https%3A%2F%2Fes.m.wikipedia.org%2Fwiki%2FArchivo%3AMethane-2D-
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45. Peat is a dark brown acidic material that
covers about 3% of the earth
It is made up of partially
decomposed organic dead
matter

46. When the saprotrophs
can't digest dead
organic matter
This matter is not
fully decomposed
Acidic conditions
develop, which inhibits
the possibility of
breaking down the
organic matter
They don´t have enough
oxygen in some
environments Saprotrophs:
organisms that feed
on dead organic
matter

47. Fossilized organic matter
Partially decomposed organic matter from past geological eras
was converted into oil and gas in porous rocks or into coal.
Carbon-> stable element (maintain unchanged in
rocks for millions of years)
Carbon deposits from geological eras-> result of
incomplete decomposition of organic matter
Deposits-> porous rocks that can hold them
Coal deposit in Nigeria
https://www.howwemadeitinafrica.com/nigerian-coal-deposits-identified/653/

48. Fossilized organic matter
• Oil and natural gas are formed in the mud at
the bottom of the seas and lakes
anaerobically (without oxygen), which is why
decomposition is incomplete
• As more mud is deposited, the decomposed
matter tends to compress and heat.
• Chemical changes occur, producing mixtures
of liquid carbon compounds and gases
(Mixtures= crude oil/ natural gas)

49. Fossilized organic matter
Coal
• Formed when deposits of peat are buried under other sediments.
• Peat is compressed and heated resulting in coal.
Cycle
• Sea level rises and falls so coastal swamps are formed as the level fell and were destroyed
and buried when the level rose and the spread inland
• Each cycle leaves a seam of coal
https://socratic.org/questions/how-do-fossil-fuels-form

50. Carbon dioxide is produced by the
combustion of biomass and fossilized
organic matter.
• If organic matter is heated
to a high temperature in
the presence of oxygen
= light and burn
Products: Water
and Carbon dioxide
• Released from the
combustion for the
biomass in the forest or
grassland
• Coal, oil & natural gas = fossilized organic matter.
Burned as fuels
• The carbon atoms in the carbon dioxide
released are removed from the
atmosphere by photosynthesizing plants

51. • Carbon dioxide is released by
combustion of the leaves of sugar
cane
• Crops of sugar cane are burned
shortly before harvested
The dry leaves = burn
off
Leaving the harvestable
stems

52. Definition: Is a sedimentary rock composed of calcium carbonate
(CaCO3)
• Formed in the sea
• Used as building material (cement)
• 10% of all sedimentary rocks are limestones
• They have huge amounts of carbon locked inside the center of the
rock
Limestone
Some animals with hard body parts contain
calcium carbonate and when they die the
component can´t dissolve in the sea water
(alkaline) so it goes to the bottom of the sea
and builds the limestone
Example: Coral reefs , mollusk shells
=
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sedimentaria%2Fdp%2FB083TC9Q6L&psig=AOvVaw1-u-
aDXpbTtgonJTnf3koQ&ust=1637771389966000&source=images&cd=vfe&ved=0CAgQjRxqFwoTCLis95v0rvQCFQAAAAAdAAAAABAE

53. Topic outline
Climate
change
Greenhouse gases
Assessing the impact of greenhouse gases
Long-wavelength emissions from Earth
Global temperatures and carbon
dioxide concentrations
Greenhouse gases and climate patterns
Industrialization and climate change
Burning fossil fuels

54. Greenhouse gases
Carbon dioxide and water vapour are the most significant
greenhouse gases
Greenhouse Earth's atmosphere

55. Greenhouse gases
These gases retain heat and maintain the Earth much
warmer than it would normally be.
CO
2
Water vapour
Released to the atmosphere by cell
respiration and combustion of
biomass and fossil fuels.
Removed from the atmosphere by
photosynthesis and dissolving in the
oceans.
Formed by evaporation from the
oceans and transpiration in plants.
Removed from the atmosphere by
rainfall and snow.

56. Other greenhouse gases
Other gases including methane and nitrogen oxides have
less impact.
Methane (CH4) Nitrous oxide (N2O)
Third most significant
greenhouse gas.
Released from:
- Marshes or waterlogged
habitats.
- Landfills
- Extraction of fossil fuels
- Melting ice in polar regions
Significant greenhouse
gas
Released by:
- Bacteria in some habitats
- Agriculture
- Car exhausts

58. Other greenhouse gases
The 2 most abundant gases in the atmosphere, oxygen
and nitrogen, are not greenhouse gases -> They don't
absorb long-wave radiation.
What percentage
of the
atmosphere is
made up by
greenhouse
gases?

59. Assessing the impact
The impact of a gas depends on its ability to absorb long-
wave radiation as well as its concentration in the atmosphere
Methane causes a lot of
warming per molecule,
but its concentration is
very low
Therefore, less impact

60. Assessing the impact
Methane remains in the atmosphere for 12 years and
CO2 for even longer
Human activity is increasing the amount of greenhouse gases
(except water vapour) and hence increasing their impact

61. How the greenhouse effect works

62. How the greenhouse effect works
The greenhouse effect is a natural process, so that Earth can
maintain moderate temperatures.
Short-waved
radiation
Long-waved
radiation
Long-waved
radiation

63. Carbon dioxide concentrations
Long-waved
radiation

64. Scientists predict that increases in greenhouse gas
concentrations will lead to an enhanced greenhouse effect
Greenhouse gases and climate patterns
Greenhouse gases play a vital role in determining global
temperatures and climate patterns
Extreme weather
conditions
Changes to
circulating ocean
currents
Some areas with
droughts and some
with floodings

65. Industrialization and climate change
There is a correlation between rising atmospheric concentrations of
carbon dioxide since the start of the industrial revolution 200 years ago
and average global temperatures.

66. Burning fossil fuels
Recent increases in atmospheric
carbon dioxide are largely due
to increases in the combustion
of coal, oil and natural gas.

67. Usa estos íconos e ilustraciones
en tu presentación de Canva.
¡Que lo pases bien diseñando!
Maestra
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