Understandings: The distribution of species is affected by limiting factors Community structure can be strongly affected by keystone species Each species plays a unique role within a community because of the unique combination of its spatial habitat and interactions with other species Interactions between species in a community can be classified according to their effect Two species cannot survive indefinitely in the same habitat if their niches are identical

1. TOPIC C.1
SPECIES AND
COMMUNITIES
IB DP – OPTION C
“Anania Shirakatsy” International Scientific-Educational Complex
By Mrs Mariam Ohanyan
Date: 05.11.2019

2. Understandings
•The distribution of species is affected by limiting
factors
•Community structure can be strongly affected by
keystone species
•Each species plays a unique role within a community
because of the unique combination of its spatial
habitat and interactions with other species
•Interactions between species in a community can be
classified according to their effect
•Two species cannot survive indefinitely in the same
habitat if their niches are identical

3. Activity 1
Define the following words:
Keystone species
Ecological niche
Community

4. Remember the following definitions:
Keystone species-is an organism that helps hold the system
together.There are three types of keystone species :
predators, ecosystem engineers, and mutualists (“Keystone
Species.”).
Ecological niche-is the role and position a species has in its
environment; how it meets its needs for food and shelter,
how it survives, and how it reproduces.A species' niche
includes all its interactions with the biotic and abiotic factors
of its environment(Study.com).
Community- is a group or association of populations of two
or more different species occupying the same geographical
area and, in a time, also known as a biocoenosis.

5. What is limiting factor in ecology?

6. What is limiting factor in ecology?
•In ecology, a limiting factor is a
component of an ecosystem which
limits the distribution or numbers of
a population
•A limiting factor defines optimal
survival conditions according to its
effect on a species when in deficiency
or excess

7. Limiting factors in ecology

8. Activity 2
Bring an example of a limiting factor
in ecology

9. Plant Example
•Plants require a balance of six critical factors in order to
optimize growth— temperature, humidity, salinity,
carbon dioxide, water and light.
•Plant growth varies greatly in response to
concentrations of salt within the soil (salinity levels)
•Plant species that are not particularly salt tolerant are
called glycophytes – these plants are easily damaged
by high salinity.
•Plant species that are salt tolerant are called
halophytes – these plants may become stressed in
freshwater environments.

10. Animal Example
•Limiting factors like the availability of food,
water, shelter and space can change animal
populations. Competition for resources,
predation and disease within the populations
can also impact populations.
• If any of the limiting factors change, animal and
plant populations change, too (“Limiting
Factors - NatureWorks.” ).

11. Animal Example
•Coral species form connected reefs that are greatly
impacted by changes in oceanic temperature
•Coral polyps receive nutrition from photosynthetic
zooxanthellae (an algae) that lives within the polyp’s
endodermis
•The zooxanthellae cannot survive in lower ocean
temperatures (i.e. < 18ºC)
•Increases in ocean temperature cause zooxanthellae to
leave the coral tissue, leading to coral bleaching (i.e. >
35ºC)

12. Coral Polyps and zooxanthellae
Source: “Zooxanthellae and Coral Bleaching.” Zooxanthellae and Coral Bleaching, 14 May 2018, ocean.si.edu/ocean-
life/invertebrates/zooxanthellae-and-coral-bleaching.

13. Dou you know how to do sampling
with quadrats and transects?
Source: https://www.youtube.com/watch?v=wkl6nwDUsZg

14. Transect Data
•Transects are used to assess species
distribution in correlation with any
abiotic factor that varies across a
measurable distance
•These factors could include
elevation, elemental exposure,
temperature, light levels, pH,
humidity and more.

15. Transect DataVideo
Source: https://www.youtube.com/watch?v=9BtFuHwvBpk

16. A kite graph
•A kite graph can be
used to represent
changes in species
distribution in a
clear and effective
fashion
Source: New GCSE Add'l Science OCR Gateway SB - Page 94,
connect.collins.co.uk/repo1/Content/Live/Infuze/COL/GCSE_Science_Add_SB_OCR_Gateway/content/Page94.html.

17. Source: “Brent Cornell.” BioNinja, ib.bioninja.com.au/standard-level/topic-4-
ecology/41-species-communities-and/niches.html.
What does this picture illustrate?

18. Fundamental vs Realised Niche
Activity 3
Make aT-Chart :
Fundamental vs Realised Niche
Fundamental
Niche
Realized Niche

19. Fundamental vs Realised Niche
Activity 3
Fundamental Niche Realised Niche
A fundamental niche is the
entire set of conditions
under which an organism
can survive and reproduce
(where it could live)
It is the theoretical habitat
and may not be fully
occupied due to the
presence of competing
species
A realized niche is the set of
conditions used by an
organism after including
interactions with other
species (where it does live)
It is the actual habitat that is
completely occupied by an
organism in the presence of
competing species

20. FUNDAMENTAL AND REALIZED
NICHE

21. All organisms interact with both the abiotic
environment and other organisms
Vocabulary
•herbivory
•competition,
•predation,
• commensalism,
• mutualism
• parasitism.

22. Activity 4:
Bring examples of competition, predation,
commensalism, mutualism and parasitism.

23. Keystone species
•A keystone species is a species that has a
disproportionately large impact on the environment
relative to its abundance

24. Activity 5
Bring examples of keystone species.

25. •There are numerous examples of keystone species within
different communities:
•Sea stars (predator) prey on urchins and mussels,
preventing mussel overpopulation and coral reef destruction
by urchins
•Honeybees (mutualist) pollinate a wide variety of plant
species, ensuring the continuation of the plant life cycle
•Beavers (engineer) build dams that transform the
environment in a manner that allows certain other species
to survive
•Keystone species are not the dominant species (most
numerous) within a community, nor do they have to be apex
predators

26. Shark Bay, Australia

27. Animals of Shark Bay
Tiger sharks eat almost
anything alive or dead.
Bottlenose dolphins will
leave the waters where
they like to eat if there
are too many tiger
sharks around.
Dugongs and green sea
turtles are among the
tiger shark’s favorite
foods.
Dolphins eat fish.
Dugongs and green sea
turtles eat sea grass.

28. Keystone species
Activity 6
Draw one box at the top of the page.This box is for
the biggest predator in the food web.
• Draw three boxes across the middle of the page.
• Draw two boxes across the bottom of the page.
These boxes are for the lowest plants or animals in
the food web.
Which animal in Shark Bay ecosystem is a keystone
species?

29. Questions:
• Who eats whom?
• What is the top predator in Shark Bay?
• What might happen if this predator were
not there anymore, or if its numbers
declined?
• Which animal is the keystone species in
the Shark Bay ecosystem?

30. Answers
• Who eats whom?
(Tiger sharks eat dolphins, dugongs, and green sea
turtles.)
• What is the top predator in Shark Bay?
(Tiger sharks)
• What might happen if this predator were not there
anymore, or if its numbers declined?
(Dugongs and green sea turtles might eat too much sea
grass.There might be too many dolphins that eat too
many fish.)
• Which animal is the keystone species in the Shark Bay
ecosystem?
(Tiger sharks)

31. Works Cited
• “Brent Cornell.” BioNinja, ib.bioninja.com.au/standard-level/topic-4-
ecology/41-species-communities-and/niches.html.
• “Limiting Factors - NatureWorks.” New Hampshire PBS,
nhpbs.org/natureworks/nwep12a.htm.
• National Geographic Society. “Keystone Species.” National Geographic
Society, 29 Aug. 2019,
www.nationalgeographic.org/encyclopedia/keystone-species/.
• NewGCSE Add'l Science OCR Gateway SB - Page 94,
connect.collins.co.uk/repo1/Content/Live/Infuze/COL/GCSE_Science_
Add_SB_OCR_Gateway/content/Page94.html.
• Study.com, Study.com, study.com/academy/lesson/ecological-niche-
definition-lesson-quiz.html.
• “Zooxanthellae and Coral Bleaching.” Zooxanthellae and Coral
Bleaching, 14 May 2018, ocean.si.edu/ocean-
life/invertebrates/zooxanthellae-and-coral-bleaching.