C1: species and communities
C1.1 The distribution of species is affected by limiting factors.
C1.2 Community structure can be strongly affected by keystone species.
C1.3 Each species plays a unique role within a community because of the unique combination of its spatial habitat and interactions with other species.
C1.4 Interactions between species in a community can be classified according to their effect.
C1.5 Two species cannot survive indefinitely in the same habitat if their niches are identical.
Source: Chapter C and Chapter 4 ecology notes. pdf, power point " species, communities and ecosystems" and Biology: Oxford IB Diploma Programme book.
C1.2 Community structure can be strongly affected by keystone species.
C1.3 Each species plays a unique role within a community because of the unique combination of its spatial habitat and interactions with other species.
C1.4 Interactions between species in a community can be classified according to their effect.
C1.5 Two species cannot survive indefinitely in the same habitat if their niches are identical.
Source: Chapter C and Chapter 4 ecology notes. pdf, power point " species, communities and ecosystems" and Biology: Oxford IB Diploma Programme book.
Limiting factors
A limiting factor is the factor that is most scarce in relation to an organism's needs.
Plants distributions are affected by temperature, water, light, soil H, soil salinity and availability of mineral nutrients. Every plant had a different range of tolerance for each of these factors.
Animal distributions are affected by temperature, water, breeding sites, food supply and territory.
Plants distributions are affected by temperature, water, light, soil H, soil salinity and availability of mineral nutrients. Every plant had a different range of tolerance for each of these factors.
Animal distributions are affected by temperature, water, breeding sites, food supply and territory.
the niche concept
Each specie plays a unique role within a community because of the unique combination of its spatial habitat and interactions with other species. In ecosystems each specie fulfills a unique role.
Definition:Mode of existence of species in an ecosystem
•Includes
–Habitat: where species lies in the ecosystem
–Nutrition: how species obtains its food
-Relationships: the interactions with other species in the ecosystem
Definition:Mode of existence of species in an ecosystem
•Includes
–Habitat: where species lies in the ecosystem
–Nutrition: how species obtains its food
-Relationships: the interactions with other species in the ecosystem
fundamental and realized niche
•Fundamental niche: potential mode of existence, given the adaptations of the species
–niche that an organism functionally could live in in the absence of competitors or other interacting species
•Realized niche: actual mode of existence, which results from its adaptations and competition from other species
–Niche that organism is actually found, following all interactions with other species
–niche that an organism functionally could live in in the absence of competitors or other interacting species
•Realized niche: actual mode of existence, which results from its adaptations and competition from other species
–Niche that organism is actually found, following all interactions with other species
Ex: The Barnacle competition:
–Field experiments on barnacles were carried out by Connell in 1961 on rocky shores on Scotland –two species of barnacle; Chthamalus stellatus and Balanus balanoide –C. Stellatus can occupy middle intertidal; but in presence of B. balanoides it prefers to live further up shore |
competitive exclusion principle
Two species cannot survive indefinitely in the same habitat if their niches are identical.
•No two species in a community can occupy the same niche a “Complete competitors cannot coexist”
For example: the bay-breasted and the yellow-rumped are birds that appear to occupy the same niche, as they feed on the similar prey items and can be found foraging in the same tree. This two species cannot habit in the same area, either one will lead to the decline and extirpation of the other or one or both of the competitors will narrow their niches.
Experiment:
•Gause set up experiments involving three species of Paramecium in a medium of oatmeal with bacteria or yeast.
–P. aurelia with P. caudatum: competitive exclusion
–P. caudatum with P. bursaria: P.caudatum was feeding on bacteria whereas P. bursaria was feeding on yeast à niches not identical
•No two species in a community can occupy the same niche a “Complete competitors cannot coexist”
For example: the bay-breasted and the yellow-rumped are birds that appear to occupy the same niche, as they feed on the similar prey items and can be found foraging in the same tree. This two species cannot habit in the same area, either one will lead to the decline and extirpation of the other or one or both of the competitors will narrow their niches.
Experiment:
•Gause set up experiments involving three species of Paramecium in a medium of oatmeal with bacteria or yeast.
–P. aurelia with P. caudatum: competitive exclusion
–P. caudatum with P. bursaria: P.caudatum was feeding on bacteria whereas P. bursaria was feeding on yeast à niches not identical
interspecific interactions
Interactions between species in a community can be classified according to their effect. In ecosystems the interactions between species are complex, Five common types of interaction can be described:
-Herbivory is primary consumers feeding on producers.
-Predation involves a consumer feeding on another consumer.
-Parasitism is when one organism feed off another but does not normally kills it.
-In mutualism, two species live in a close association where both organisms benefit form the association.
-In commensalism, one organism benefits and the other is neither harmed nor helped.
-Herbivory is primary consumers feeding on producers.
-Predation involves a consumer feeding on another consumer.
-Parasitism is when one organism feed off another but does not normally kills it.
-In mutualism, two species live in a close association where both organisms benefit form the association.
-In commensalism, one organism benefits and the other is neither harmed nor helped.
Key stone species
Community structure can be strongly affected by a key stone specie.
A key stone specie is one which has a disproportionate effect on the structure of an ecologycal community.
Ex: elephants, mountain lion, the prairie dog and the sea otter.
A key stone specie is one which has a disproportionate effect on the structure of an ecologycal community.
Ex: elephants, mountain lion, the prairie dog and the sea otter.
Theory of Knowledge
Random samples are taken in studies involving large geographical areas or if limited time is available. Is random sampling a useful tool for scientists despite the potential for sampling bias?
Yes, because I believe that it is not practical or pragmatic to sample a whole population, and therefore even if random sampling does leave space for error is the only method that will help them to get the closer estimate to the actual information that they want. In order to eliminate the bias the sample have to be the more random possible and having a lot of trials of sample can be helpful too. For example: If they want to sample the number of bees in the park, they will go to one tree and sample how many there are, and if the next 4 random selected trees give them a similar result , why sample all the 300 or more trees that a park can have. That is what random sampling is use so much around the world, given that it is the more pragmatic way to get the closest result to the actual one and in an easier way.
UNDERSTANDING
- The distribution of species if 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 interaction 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
Notes: the understanding give us better knowledge on things like the limiting factors, key stones species, niches and interactions between the species. This is important at the moment of studying for the exams.
APPLICATIONS
- Distribution of one animal and one plant species to illustrate limits of tolerance and zones of stress
- Local examples to illustrate the range of ways in which species can interact within a community
- The symbiotic relationship between zooxanthellae and reef-building coral reef species
Random samples are taken in studies involving large geographical areas or if limited time is available. Is random sampling a useful tool for scientists despite the potential for sampling bias?
Yes, because I believe that it is not practical or pragmatic to sample a whole population, and therefore even if random sampling does leave space for error is the only method that will help them to get the closer estimate to the actual information that they want. In order to eliminate the bias the sample have to be the more random possible and having a lot of trials of sample can be helpful too. For example: If they want to sample the number of bees in the park, they will go to one tree and sample how many there are, and if the next 4 random selected trees give them a similar result , why sample all the 300 or more trees that a park can have. That is what random sampling is use so much around the world, given that it is the more pragmatic way to get the closest result to the actual one and in an easier way.
UNDERSTANDING
- The distribution of species if 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 interaction 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
Notes: the understanding give us better knowledge on things like the limiting factors, key stones species, niches and interactions between the species. This is important at the moment of studying for the exams.
APPLICATIONS
- Distribution of one animal and one plant species to illustrate limits of tolerance and zones of stress
- Local examples to illustrate the range of ways in which species can interact within a community
- The symbiotic relationship between zooxanthellae and reef-building coral reef species