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C1: species and communities
Sources: Chapter C Ecology notes, PDF Energy flow and succession and Pearson Book.
trophic levels
C2.1 Most species occupy different trophic levels in multiple food chain.
An organism’s trophic level is its feeding position in a food chain. Because feeding relationships within an ecosystem are often web-like, an organisms can occupy more than one trophic level. Ex: the diet of an owl involves animals which occupy different trophic levels.
When stating an organism’s trophic level, reference needs to be made to a particular food chain.
An organism’s trophic level is its feeding position in a food chain. Because feeding relationships within an ecosystem are often web-like, an organisms can occupy more than one trophic level. Ex: the diet of an owl involves animals which occupy different trophic levels.
When stating an organism’s trophic level, reference needs to be made to a particular food chain.
food webs
C2.2 A food web shows all possible food chains in a community.
Food web: is a model that summarizes all of the possible food chains in a community. Is also a diagram that shows how food chains are linked together in a complex feeding relationship
Trophic relationships within ecological communities tend to be complex and web-like. This is because many consumers feed on more than one species and are fed upon by more than one species.
When a food web is constructed, organisms at the same trophic level are shown at the same level in the web. This isn’t always possible as some organisms feed at more than one trophic level.
• The food web has a number of advantages over a food chains including:
– More than one producer supporting a community
– A single producer being a food source for a number of primary consumers
– A consumer may have a number of different food sources on the same or different trophic levels
– A consumer can be an omnivore, feeding as a primary consumer and as a consumer at higher trophic levels
Food web: is a model that summarizes all of the possible food chains in a community. Is also a diagram that shows how food chains are linked together in a complex feeding relationship
Trophic relationships within ecological communities tend to be complex and web-like. This is because many consumers feed on more than one species and are fed upon by more than one species.
When a food web is constructed, organisms at the same trophic level are shown at the same level in the web. This isn’t always possible as some organisms feed at more than one trophic level.
• The food web has a number of advantages over a food chains including:
– More than one producer supporting a community
– A single producer being a food source for a number of primary consumers
– A consumer may have a number of different food sources on the same or different trophic levels
– A consumer can be an omnivore, feeding as a primary consumer and as a consumer at higher trophic levels
matter is recycled
Decomposition: process by which organic matter is broken down into simpler forms.
– Allows for the formation of soil, the recycling of nutrients stored in the organic materials
• Saprotrophs: secrete digestive enzymes into dead organism, which hydrolyze biological molecules of which the dead organism is composed
• Saprotrophs are essential in the flow of nutrients through ecosystem, which would otherwise accumulate in debris
– Allows for the formation of soil, the recycling of nutrients stored in the organic materials
• Saprotrophs: secrete digestive enzymes into dead organism, which hydrolyze biological molecules of which the dead organism is composed
• Saprotrophs are essential in the flow of nutrients through ecosystem, which would otherwise accumulate in debris
the impact of climate on ecosystems type
C2.4 The type of stable ecosystem that will emerge in an area is predictable based on climate
-Climate is a property that emerges from the interaction of a number of variables including temperature and precipitation.
- Temperature influences the distribution of organisms. The temperature influences rates of cell respiration, photosynthesis, decomposition and transpiration and ultimately has an impact on productivity.
-Precipitation also impacts productivity by influencing rates of photosynthesis and rates of decomposition.
-Climate is a property that emerges from the interaction of a number of variables including temperature and precipitation.
- Temperature influences the distribution of organisms. The temperature influences rates of cell respiration, photosynthesis, decomposition and transpiration and ultimately has an impact on productivity.
-Precipitation also impacts productivity by influencing rates of photosynthesis and rates of decomposition.
respiration rates and biomass accumulation
C2.3 The percentage of ingested energy converted to biomass is dependent on respiration rate.
Production in plants happens when organic matter is synthesized by photosynthesis. In animals it occurs when food is absorbed after digestion. Energy units are usually used for measuring production. The amounts of energy are given per unit area and per year.
Gross and net production values can be calculated using this equation:
Net production= gross production - respiration
Gross production: the total amount of organic matter produced per unit are and per unit time by a trophic level
Net production: is the amount of gross production remaining after subtraction of the amount used for respiration by the trophic level.
In the early stages of primary production the high availability of sunlight means that gross production is high and there is little total biomass in the community. As succession proceeds the standing biomass increases and the total amount of respiration increases. Further the amount of gross production begins to decline. An equilibrium is reached where the total community production to total community respiration (P/R) ratio equals 1.
Production in plants happens when organic matter is synthesized by photosynthesis. In animals it occurs when food is absorbed after digestion. Energy units are usually used for measuring production. The amounts of energy are given per unit area and per year.
Gross and net production values can be calculated using this equation:
Net production= gross production - respiration
Gross production: the total amount of organic matter produced per unit are and per unit time by a trophic level
Net production: is the amount of gross production remaining after subtraction of the amount used for respiration by the trophic level.
In the early stages of primary production the high availability of sunlight means that gross production is high and there is little total biomass in the community. As succession proceeds the standing biomass increases and the total amount of respiration increases. Further the amount of gross production begins to decline. An equilibrium is reached where the total community production to total community respiration (P/R) ratio equals 1.
secondary succession
C2.6 Disturbance influences the structure and rate of change within ecosystems.
Secondary succession takes places in areas where there is already or recently has been an ecosystem. The succession is initiated by a change in conditions. Construction sites or roads might become disused and eventually plants grow in the remains.
In the following figure a sequence of communities following the abandonment of an arable field. It indicates that the pace of change slows as succession proceeds. Close to the time of disturbance the rates of system respiration and productivity increases rapidly and there is an accumulation of biomass. Species diversity increases close to the time to the disturbance. At the climax stage changes are still occurring but slower.
Secondary succession takes places in areas where there is already or recently has been an ecosystem. The succession is initiated by a change in conditions. Construction sites or roads might become disused and eventually plants grow in the remains.
In the following figure a sequence of communities following the abandonment of an arable field. It indicates that the pace of change slows as succession proceeds. Close to the time of disturbance the rates of system respiration and productivity increases rapidly and there is an accumulation of biomass. Species diversity increases close to the time to the disturbance. At the climax stage changes are still occurring but slower.
closed ecosystems
C2.5 In closed ecosystems energy but not matter is exchanged with the surroundings
Open systems exchange matter and energy with their surroundings. Closed systems, such as the mesocosm exchange energy but not matter with the surroundings. Isolated systems, exchange neither matter nor energy with their surroundings. Ecological systems exits along the continuum. Natural system exchange both matter and energy with their surroundings and so are categorized as open systems. In undisturbed systems, the rate of exchange of matter with the surroundings occurs most notably due to the water cycle and nutrient cycles that have a gaseous phase.
Open systems exchange matter and energy with their surroundings. Closed systems, such as the mesocosm exchange energy but not matter with the surroundings. Isolated systems, exchange neither matter nor energy with their surroundings. Ecological systems exits along the continuum. Natural system exchange both matter and energy with their surroundings and so are categorized as open systems. In undisturbed systems, the rate of exchange of matter with the surroundings occurs most notably due to the water cycle and nutrient cycles that have a gaseous phase.
Theory of Knowledge: Do the entities in scientist's models for example trophic levels or Germehl diagrams actually exits or are they primarily useful inventions for predicting and explaining the natural?
I think that the models actually exits and that that is the way how the tropic levels in the food chain actually are but also I think that they can be a really good tool and be used for predictions because it will be really good to know what will happen in the future. I believe that they are true and that scientists create them to show how the world how it actually is but they also do it to predict the food chain of an ecosystem to know if it will work, or what will happen if one specie disappear, they could have an answer. For example if the owl eats mouses and suddenly all the owls disappear then mouses population will increase and they will have to put another animal to replace the owls function in the ecosystem, like cats, and then they will eat the mouses so their size of population can decrease again.