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
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
SKILLS
- Analysis of a data set that illustrates the distinction between fundamental and realized niche.
- Use of transect to correlate the distribution of plant or animal species with an abiotic variable
LIMITING FACTORS
The distribution of species is affected by limiting factors
A limiting factor is the facts that is most scarce in relation to an organism's needs.
Plant distributions are affected by abiotic variables: temperature, water availability, light intensity, soil pH, soil salinity and availability of mineral nutrients. Every plant species has a range of tolerance for each of these facts, and is excluded from areas that are outside the range for one or more of the factors. For example, plant species from the tropics are not adapted to survive frosts so would not survive in northern regions.
Animal distributions are affected by temperature, water, breeding sites, food supply and territory. Extremes of temperature require special adaptations. For example, the large ears of elephants are adaptations for dissipating heat. This allows them to live in hot environments
THE NICHE CONCEPT
Each species plays a unique role within a community because of the unique combination of its spatial habitat and interactions with other species
Within an ecosystem, each species fulfills a unique role, called its ecological niche. This includes the spatial habitat, how the species obtains its food and the interactions with other species. For a species to be able to inhabit an area, there must be a suitable habitat where the abiotic variables which influence its survival are within the zone of tolerance.
COMPETITIVE EXCLUSION PRINCIPLE
Two species cannot survive indefinitely in the same habitat if their niches are identical
Two species cannot coexist in the same habitat if their niches completely overlap. This is known as the competitive exclusion principle. Either one species will lead to the decline and extirpation of the other, or one or both of the competitors will narrow their niches to avoid competition.
FUNDAMENTAL AND REALIZED NICHES
The fundamental niche of a species is the potential mode of existence, given the adaptations of the species. It refers to the broadest range of habitats it can occupy and roles it can fulfill. The realized niche is the actual mode of existence, which results form the combination of its adaptations and competition with other species.
- 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
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
SKILLS
- Analysis of a data set that illustrates the distinction between fundamental and realized niche.
- Use of transect to correlate the distribution of plant or animal species with an abiotic variable
LIMITING FACTORS
The distribution of species is affected by limiting factors
A limiting factor is the facts that is most scarce in relation to an organism's needs.
Plant distributions are affected by abiotic variables: temperature, water availability, light intensity, soil pH, soil salinity and availability of mineral nutrients. Every plant species has a range of tolerance for each of these facts, and is excluded from areas that are outside the range for one or more of the factors. For example, plant species from the tropics are not adapted to survive frosts so would not survive in northern regions.
Animal distributions are affected by temperature, water, breeding sites, food supply and territory. Extremes of temperature require special adaptations. For example, the large ears of elephants are adaptations for dissipating heat. This allows them to live in hot environments
THE NICHE CONCEPT
Each species plays a unique role within a community because of the unique combination of its spatial habitat and interactions with other species
Within an ecosystem, each species fulfills a unique role, called its ecological niche. This includes the spatial habitat, how the species obtains its food and the interactions with other species. For a species to be able to inhabit an area, there must be a suitable habitat where the abiotic variables which influence its survival are within the zone of tolerance.
COMPETITIVE EXCLUSION PRINCIPLE
Two species cannot survive indefinitely in the same habitat if their niches are identical
Two species cannot coexist in the same habitat if their niches completely overlap. This is known as the competitive exclusion principle. Either one species will lead to the decline and extirpation of the other, or one or both of the competitors will narrow their niches to avoid competition.
FUNDAMENTAL AND REALIZED NICHES
The fundamental niche of a species is the potential mode of existence, given the adaptations of the species. It refers to the broadest range of habitats it can occupy and roles it can fulfill. The realized niche is the actual mode of existence, which results form the combination of its adaptations and competition with other species.
INTERSPECIFIC INTERACTIONS
Interactions between species in a community can be classified according to their effect
Within ecosystems, the interactions between species are complex. Five common types of interaction are described here:
- Competition occurs when two spies require the same resource and the amount obtained by one species reduces the amount available to the other.
- Predation involves a consumer feeding on another consumer for example the bay-breasted warbler, which winters in Guatemala, feeds on insects including dragonflies and the dingo in New South Wales feeds on the red kangaroo.
- Parasitism is when one organism feeds off another but does not normally kill it. The predatory organisms in this case is termed a parasite and the prey a host.
- In mutualism, two species live in a close association where both organisms benefit from the association.
- In commensalism, one organism benefits and the other is neither harmed nor helped.
KEYSTONE SPECIES
Community structure can be strongly affected by keystone species.
A keystone species is one which has a disproportionate effect on the structure of an ecological community. For example, if the sea otter became extinct, then the sea urchin quantity would begin to increase and the kelp beds would begin to disappear.
Interactions between species in a community can be classified according to their effect
Within ecosystems, the interactions between species are complex. Five common types of interaction are described here:
- Competition occurs when two spies require the same resource and the amount obtained by one species reduces the amount available to the other.
- Predation involves a consumer feeding on another consumer for example the bay-breasted warbler, which winters in Guatemala, feeds on insects including dragonflies and the dingo in New South Wales feeds on the red kangaroo.
- Parasitism is when one organism feeds off another but does not normally kill it. The predatory organisms in this case is termed a parasite and the prey a host.
- In mutualism, two species live in a close association where both organisms benefit from the association.
- In commensalism, one organism benefits and the other is neither harmed nor helped.
KEYSTONE SPECIES
Community structure can be strongly affected by keystone species.
A keystone species is one which has a disproportionate effect on the structure of an ecological community. For example, if the sea otter became extinct, then the sea urchin quantity would begin to increase and the kelp beds would begin to disappear.
TOK
How do human values underlie pursuit of truth in science? How, if at all, do they influence methodology?
In statistical testing, two hypotheses are tested: the null and alternative hypotheses. However, many times, because of certain types of limitations, for example measuring incorrectly, there are two types of error that can occur in hypotheses testing. A type I error occurs when when a null hypotheses is rejected when it is true. A type II error occurs when a null hypotheses is accepted when it is false. It is not possible to minimize the likelihood of one type error without increasing the likelihood of the other type of error. This involves a judgment. For example, if a null hypotheses states that an alien species does not affect or damage the native species, then attempting to reduce a type I error will make it harder to reject the null hypotheses even when it is false.
How do human values underlie pursuit of truth in science? How, if at all, do they influence methodology?
In statistical testing, two hypotheses are tested: the null and alternative hypotheses. However, many times, because of certain types of limitations, for example measuring incorrectly, there are two types of error that can occur in hypotheses testing. A type I error occurs when when a null hypotheses is rejected when it is true. A type II error occurs when a null hypotheses is accepted when it is false. It is not possible to minimize the likelihood of one type error without increasing the likelihood of the other type of error. This involves a judgment. For example, if a null hypotheses states that an alien species does not affect or damage the native species, then attempting to reduce a type I error will make it harder to reject the null hypotheses even when it is false.