Ecology and Conservation Flashcards
Plant and Animal Distributions
+ limitations of symmetrical distribution graphs
+ example of plant distribution
The distribution of a species is the range of places that it inhabits.
Limiting factors set limits to their distribution, shown in graphs as limits of tolerance and zones of stress. It is the factor that is most scarce in relation to an organism’s needs.
For example, plant species from the tropics are not adapted to survive frosts in the northern regions. Plants from these norther regions have chemicals in their cells that act like anti-freeze and prevent frost damage from ice crystal formation. However, these northern plants species are not adapted to grow in the trophic. They would transpire excessively and their method of photosynthesis would be very inefficient at high temperatures.
One limitation of the graph is its symmetrical nature, when a shortage may have a more acute affect than an abundance or vice versa. For instance, there is an upper limit of a toxin that can be tolerated, but often not a lower limit.
What are ecological niches?
The role of a species is its ecological enviroment:
- spatial habitat - where the species lives
- interactions - how the species affects and is affected by other species in the community, including nutrition
Two species will compete if they inhabit overlapping niches, for example breeding sites or food. Because they do not compete in other ways, they will usually be able to coexist.
However, if two species have an identical niche they compete in all aspects of their life. One will inevitably prove to be the superior competitor and cause dominance even extinction of the opponent. The principle that only one species can occupy a niche in an ecosystem is called the competitive exclusion principle.
Fundamental and realized niches
- The fundamental niche is what a species could potentially occupy based on its limits of tolerance.
- The realised niche what it actually occupies, smaller than the fundemental niche due to competition.
Keystone species
A keystone species has a disproportionate effect on the structure of an ecological community.
Some keystone species are the direct or indirect food source for most other species int he community. Others are predators that have major effects on population sizes by limiting the numbers of their prey. The conservation of keystone species is essential for the overall conservation of an ecosystem.
Transects
A method of sampling at regular positions across an ecosystem, to investigate wether the distribution of an organism correlates with an abiotic variable.
A sample is random if every member of a population has an equal chance of being selected in the sample.
Interactions between species (…mutualism, etc.)
may be classified according to their effects:
Herbivory - primary consumers feed on plants or other producers; this harms producers but reduces competition between producers
Omnivore
Carnivore
Predation - predators benefit as they feed on prey; predation affects numbers and behavior of prey.
Parasitism - a parasite that lives on or in a host, obtaining food from the host and harming it.
Competition - a species using a resource reduces the amount available to other species using it.
Mutualism - different species living together in a close relationship, from which they both benefit.
Extra:
Commensalism - one organism benefits from the other without affecting it
Amensalism - one organism is harmed while the other is unaffected
Mutualism in reef-building corals
Most corals that build reefs contain mutualistic photosynthetic algae called zooxanthellae (they’re symbiotic because they live together).
The coral provides the algae with a protected environment and holds it in position close to the water surface where it is enough light for photosynthesis to occur.
The zooxanthellae provide the coral with products of photosynthesis such as glucose, amino acids and also oxygen. The coral also feeds on organic particles and plantain suspended in the sea water, using its stinging tentacles. The coral’s waste products are all used by the zooxanthellae: carbon dioxide, ammonia and phosphates.
Zooxanthellae make coral reefs one of the most biological productive ecosystems. They improve the neutron of corals enough for the building of coral reefs by the deposition of their hard exoskeletons, which the corals use to eliminate locomotion and stay attached to the reef, as they want to always be in the optimum depth of the water for sunlight to reach them.
Energy conversion rates
gross production - the total amount of energy in food assimilated by an animal or in food made by photosynthesis in producers.
net production - the amount of energy converted to biomass in an organism. It is always less than gross production because some food is used in cell respiration and the energy released from it is lost from the organisms and the ecosystem.
The efficiency with which a species uses food is assessed by calculating a feed conversion ratio (FCR):
conversion ratio = (intake of food [g]) / (net production of biomass [g])
the higher the ratio, the higher the respiration rate of the species and the lower the percentage of ingested energy that is converted to biomass. This can show the sustainability of food production.
Birds and mammals usually have high respiration rates because they maintain constant body temperatures so their FCRs are relatively high.
Nutrients in ecosystems (+ terestrial storage compartments, opened vs. closed systems)
In contrast to energy, nutrients can be retained in an ecosystem for an unlimited time.
- A closed ecosystem does not exchange nutrients with its surroundings.
- An open ecosystem is the opposite.
• Terrestrial ecosystems have three main storage compartments: biomass, litter, and soil.
Nutrients flow between these compartments. - A nutrient storage and flow model (Gershmehl diagram) of terrestrial ecosystems indicates the amount of nutrients in each compartment by the size of the circle and flow rates by the size of the arrows.
Humans and nutrient cycles
The nitrogen cycle is affected greatly by human activity.
Fertilizers containing nitrates and ammonium are produced by the Haber process from gaseous nitrogen. Runoff from fields results in raised nitrogen concentrations in water bodies. Nitrogen oxides from vehicle exhausts dissolve in water in the atmosphere to form nitrates, which are deposited in rainwater.
These extract inputs in the nitrogen cycle cause eutrophication and algal blooms.
Ecological succession (+ commonalities during primary successions)
An ecological succession is a series of changes to an ecosystem, caused by complex interactions between the community of biotic and biotic factors.
Primary succession starts in an area where living organisms have not previously existed, for example a new island, created by volcanic activity.
Secondary succession the replacement of one ecosystem by another following environmental change (from grass to woodland)
Some commonalities can be seen during primary succession:
- species diversity increases overall with some species dying out but more joining the community
- plant density increases as measured with the leaf area index (leaf per unit of ground surface area)
- organic matter in the soil increases as more dead leaves, roots and other matter are released by plants
- soil depth increases as organic matter helps to bin mineral matter together
- water-holding capacity of soil increases due to the increased organic matter
- water movement speeds up due to soil structure changes that allow excess water to drain through
- soil erosion is reduced by the binding action of the roots of larger plants
- nutrient recycling increases due to increased storage in the soil and the biomass of organisms
Climax communities
Ecological succession usually stops when a stable ecosystem developed with a group of organisms called the climax community.
Endemic species and alien species
An endemic species naturally occurs in an area.
An alien species are artificially introduced by humans and do not naturally occur.
Alien species often become invasive (produce rapidly, out-competing local species) because they have no predators. Unless an alien species is adapted to an logical niche not exploited in a community, it will compete with endemic species for resources and may cause them to become extinct by competitive exclusion.
Biological control and alien species
Biological control is the use of a predator, parasite or pathogen to reduce or eliminate a pest.
Biomagnification
Some pollutants are absorbed into living organisms and accumulate because they are not efficiently excreted.
When a predator consumes prey containing the pollutant, the level in the body of the predator rises and can reach levels much higher that those in the bodies of its prey, as the predator eats more of them. Concentration of pollutants in the tissues of organisms is called biomagnification and happens at each stage in food chains, with higher trophic levels reaching toxic doses.
