Ecosystems Flashcards
(35 cards)
Define ecology.
The study of relationships between organisms, or groups of organisms, and their environments.
Define habitat.
The place where an organism lives (the natural environment of an organism).
Define population.
A group of organisms of the same species, in the same place (at the same time) that can interbreed.
Define community.
All of the organisms of different species (living within the same area) that interact together.
Define competition.
The result of a demand, by two or more organisms, on a limited supply of resources (e.g. food, mates, light etc). Can be intraspecific (within the same species) or interspecific (between different species).
Define ecological niche.
The role that an animal or plant species plays in the environment and the status of an organism within its environment (which affects its survival). Often defined in animals by feeding habits & size.
Define competitive exclusion principle.
No two ecological niches can be exactly the same (i.e. niches are exclusive and mutual coexistence of two species will require their niches to be sufficiently different). In competitive exclusion one species is eliminated by another in an area via interspecific competition.
What is an ecosystem?
‐ A community of organisms ; ‐ Interacting with one another, plus the environment in which they live and with which they interact ; (i.e. interaction of biotic and abiotic components )
‐ These biotic and abiotic components are linked together through nutrient cycles and energy flows ; ‐ Ecosystems are described as dynamic, meaning that the interactions within them can change due to interference / disturbance ;
-The tendency of a system to remain close to its equilibrium state, despite disturbance, is termed its resistance. On the other hand, the speed with which it returns to its initial state after disturbance is called its resilience.
What is a biotic factor?
A factor created by a living organism which affects the life of another organism.
For example:
‐ A predator consuming its prey ‐ Parasitism
‐ Mutualism ‐ two organisms of different species live in close association and benefit from relationship
‐ Interspecific competition (between species)
‐ Intraspecific competition (within species)
What is an abiotic factor?
A non‐living, chemical or physical component in the environment. For example: ‐ Light intensity ‐ Water supply ‐ Humidity ‐ Wind speed ‐ Temperature ‐ Oxygen and carbon dioxide concentration ‐ pH of water and soil ‐ Availability of inorganic ions ‐ Forest fire
Define food web.
Interacting chains of organisms, existing in any natural community, through which energy and matter are transferred. Each stage in a chain feeds on, and thus gains energy from, the one preceding it (and is in turn eaten by the one succeeding it). All food chains start with autotrophic organisms.
Define trophic level.
The position of an organism in a food web (n.b. organisms may occupy more than one feeding level). The number of trophic levels in a community is limited by the inefficiency of energy flow from one level to the next.
Define producer / autotroph.
An organism that synthesises complex organic molecules (such as carbohydrates, fats, and proteins) from simple inorganic molecules using energy from light (photosynthesis / photoautotroph) or inorganic chemical reactions (chemosynthesis / chemoautotroph).
Define consumer / heterotroph.
An organism that obtains food by feeding on other organisms or organic matter (due to lack of the ability to manufacture own food from inorganic sources). They produce complex organic molecules from organic sources of carbon e.g. plant or animal matter. All animals, protozoans, fungi, and most bacteria are heterotrophs.
Define detritivores.
Organisms feeding on dead organic material, especially plant detritus. (e.g. earthworms & woodlice).
Define decomposers.
Organisms (bacteria and fungi) which break down detritus (i.e. dead organisms and waste materials e.g. dead leaves, urine & faeces). Play a crucial role in recycling molecules and ions in an ecosystem.
How can biomass transfers between trophic levels be measured?
Primary productivity:
• The rate at which plants convert light energy into chemical potential energy.
• Measured in kJ m‐2 year‐1 Gross primary productivity (GPP):
• Total quantity of energy transferred by plants from sunlight to plant tissue.
Net primary productivity (NPP):
• The quantity of energy left after plants have supplied their own needs by respiration.
Climate: tropical vs temperate
Tropical has a greater NPP because:
• Higher temperature ;
• Higher light intensity ;
‐ Faster rates of photosynthesis ;
‐ More organic molecules/biomass formed ;
‐ More organic molecules/biomass stored ;
‐ Less seasonal variation ;
Vegetation: woodland / rainforest vs grasslands
Woodland or rainforest has a greater NPP because:
• Woodland or forest has greater complexity & greater biodiversity, therefore more niches ;
• Competition for space less limiting ;
How to measure energy transfers between trophic levels?
- Place known dry mass of organic material in burning chamber of calorimeter ;
- Switch on oxygen supply and filter pump ;
- Note initial temperature of water ;
- Burn food to ash ;
- Keep stirring the known volume of water ;
- Measure the final temperature ;
- Energy content = number of organisms x mean dry mass of one organism x energy content of 1g of dry mass ;
How energy is transferred though ecosystems?
1o Producers (Plants):
• The sun is the energy source for the system ;
• Producers trap sun’s energy ‐ during photosynthesis ;
• Not all energy trapped and reason ;
Some is:
‐ Reflected off plant (only certain wavelengths of light can be absorbed) ; ‐ Hits non‐photosynthetic parts e.g. bark ;
‐ Passes through leaf, missing chloroplasts ;
‐ Some is heat that is used in evaporation ;
• Energy is used for plant metabolism (respiration) ‐ so this energy is not passed on to consumer ;
• Some energy used to make biomass & storage ‐ so this energy is passed on to consumer ;
1o Producers to 1o Consumers (Herbivores):
• 1o consumer eats producer ;
• Some parts of the producer are not edible or accessible e.g. cellulose, roots ;
• Some parts are not digested, therefore lost as faeces ;
• Some energy used to make biomass & for storage ‐ so this energy is passed on to consumer ;
1o Consumers to 2o Consumers (Carnivores/Omnivores)
• 2o consumer eats 1o consumer ;
• Some parts of animal not edible e.g. bones, feathers ‐ so this energy is not passed on to consumer ;
• Energy used by animal in moving ‐ so this energy is not passed on to consumer ;
• Energy is lost in excretion e.g. in urine ‐ so this energy is not passed on to consumer ;
• Energy lost as heat from respiration ‐ so this energy is not passed on to consumer ;
• Some energy used for growth & storage ‐ so this energy is passed on to consumer ;
General points to make:
• Some energy is transferred to decomposers (e.g. death, excretion, egestion, moulting) ;
• Efficiency of energy transfer between trophic levels is rarely greater than 10% ;
• Quote comparative figures from diagram ;
• Process data/manipulate figures to illustrate a point ;
What factors influence the efficiency of energy transfer in ecosystems?
Energy reaching producers is not converted to growth because:
• Reflected off plant (only certain wavelengths of light can be absorbed) ;
• Hits non‐photosynthetic parts e.g. bark ;
• Passes through leaf, missing chloroplasts ;
• Some is heat that is used in evaporation / lost via respiration ;
Why do herbivores lose more energy in faeces than carnivores?
- Meat is mainly protein and fat so is more digestible ;
* Meat contains no cellulose. Cellulose is indigestible ;
Why does the mammal carnivore pass on less energy to the next level than the invertebrate carnivore?
• Mammals are homeotherms
• Have higher rates of respiration to maintain a constant core blood temperature
• Lose a greater proportion of energy as heat
‐ A smaller proportion of energy in food consumed can be used to produce biomass
‐ Fewer organic molecules formed/stored
