Chapter 4. Ecology Flashcards
Species
Groups of organisms that can potentially interbreed to produce fertile offspring.
Cross-breeding
Members of different species breed together.
Reproductive separation…
Prevents the genes of two species from mixing together.
Population
A group of organisms of the same species living in the same area at the same time.
Autotrophic
Self-feeding: makes their own carbon compounds from carbon dioxide and other simple inorganic substances.
Example: Arabidopsis thaliana (a model plant most commonly used)
Hetertrophic
Feeding on others (includes consumers, saprotroohs and detritus ores): organisms obtain their carbon compounds from other organisms.
Example: humming bird.
Mixotrophic
Organisms use both methods of nutrition (autotrophic + heterotrophic).
Example: Euglena gracilis (an unicellular organism) using chloroplasts to photosynthesize when there is sufficient light, while being able to feed on detritus and smaller organisms by endocytosis.
Consumers
Consumers are heterotrophs that feed on organisms that are either still alive or have only been dead for a relatively short period of time.
Examples: paramecium (unicellular); Milvus Milvus (multicellular).
Parasitic plants and algae
Parasitic plants and algae are those which do not contain chloroplasts and do not carry out photosynthesis. These species grow on other plants and obtain carbon compounds from them and cause them harm. They have evolved repeatedly from photosynthetic species by losing the chloroplasts (which can be easily lost out but cannot be easily developed)
Carrion
Dead animal remains.
Detritivores
Heterotrophs that obtain organic nutrients from detritus by internal digestion (ingestion –> digestion).
Example: earthworms.
Dichotomous key
二叉式检索表
Saprotrophs
Heterotrophs that obtain organic nutrients from dead organic matters by extracellular digestion (secreting diegstive enzymes to the dead organic matter –> obsorb the products of digestion). Also known as decomposers.
Examples: many bacteria and fungi.
Quadrats
Quadrats are square sample areas marked out by a quadrat frame.
Community
Populations of different species living in the same area at the same time and interacting with each other.
Example: a coral reef.
Nutrient
An element which an organism needs.
Ecosystem
A single highly complex INTERACTING system which consists of communities of organisms in an area and the abiotic environment which they live in.
Sustainability
The ability to continue a defined behaviour indefinitely.
Mesocosms
Small experimental areas that are set up as ecological experiments.
Food chain
A food chain is a sequence of organisms, each of which feeds on the previous one. It shows the feeding relationships and energy flow between trophic levels in an ecosystem.
The laws of thermodynamics state that…
1) Energy transformations are never 100% efficient.
2) Hear passes from hotter to cooler bodies.
Pyramids of energy
Pyramids of energy are quantitative representations of the amount of energy converted to a new biomass by each trophic level in an ecological community.
The unit is kJ/m2/yr.
Biomass
A measure of the dry mass of biological material of an organism (in grams), which includes the cells, tissues and carbon compounds of the organism.
Examples of sources of nutrition for detritivores and saprotrophs
- Dead leaves and other dead organic matter discarded by plants;
- Feathers, hairs, dead skin cells etc.
- Faeces;
Why are saprotrophs also known as decomposers?
They break down carbon compounds in dead organic matter and release them back into the food chains and the ecosystem, so that the nutritions are recycled and available for other organisms again.
Describe the steps of quadrating
- Divide the investigated field into grided areas using two perpendicular lines marked by measuring tapes
- Use a random number generator/table to generate random coordinates, which determine the positions at where quadrats will be placed
- Place the quadrat frame and count the percentage coverage /number of species using the grids
- Record results in a tabulated format for futher analysis
- Samples must be randomly chosen
- Only applicable for organisms with low mobility
- Replicates for reliable and accurate estimates
Example of abiotic environment influencing living organisms
Salty sea water creates a very specialized habitat and only mangroves (trees adapted to high-salinty soil) are able to survive
Example of organisms influencing abiotic environment
Formation of sand dunes:
The roots of specialized plants growing on the loose, wind-blown sand stabilize the sand. Their leaves also break the wind and capture the sand carried by the wind. Therefore, more sand is being deposited to form a sand dune in offshore areas.
Sustainability and example
Sustainability is the ability to continue a defined behaviour indefinitely. Example: nutrition cycles, where nutritions are being transferred endlessly between organisms and abiotic reserves by producers and saprotrophs
3 requirements for sustainability in ecosystems
- Nutrition sustainability
- Energy availability
- Detoxification of waste products: ammoniun ions released by decomposers (which can be potentially toxic when accumulated in large quantities) are being absorbed and used as an energy source by Nitrosomonas (nitro – nitrogen – ammonium) bactera in the soil.
Applications of mesocosms
Ecological experiments, where one abiotic/biotic variable can be changed and the results (sustainability) on the ecosystem can be tested, without causing harm to our natural world.
- Replicates
- Can be done in the lab
- Aquatic (tanks)/terresterial (fenced-off enclosers in grassland/forest)
Key questions to ask when setting up a mesocosm
- Energy availability: will there be enough energy created by producers for the rest of the community?
- Oxygen availability: will there be enough oxygen created by producers for the rest of the community?
- Nutrition sustainability: how can nutritions be recycled?
- Detoxification of wastes: will the wastes be potentially toxic? Which organisms are able to detoxify the wastes?
- Ethics: how to avoid causing harm/pain to the organisms
Examples of producers
Plants
Eukaryotic algae
Cyanobacteria
They are all capable of converting light energy/chemical energy into chemical energy.
Define chemostroph and give examples
Organisms which obtain their energy from oxidizing electrons from chemical molecules in the environment. They convert inogranic compounds into organic compounds, which are available to be consumed by organisms at higher trophic levels.
Examples: iron-oxidizing bacteria living in deep sea, where light cannot penetrate the water and underwater volcanoes on the sea floor provide them chemical energy as a substitute for light
Why energy transfers can never be 100% efficient between trophic levels?
The second law of thermodynamics
- Lost during metabolism (e.g. cellular respiration: the process of transferring energy in glucsoe and lipids to ATP)
- Lost as heat to the abiotic environment in cellular activities: muscles warming up during exercise
- Uningested
- Undigested
Carbon fixation
The convertion of inorganic carbon compounds to organic carbon compounds by living organisms e.g. photosynthesis.
Application: atmosphere above regions with high vegetation coverage and high light intensity has lower CO2 concentration
Why the length of food chains are restricted? Why does the biomass pyramids have wider base and narrower tops?
Energy and organic compounds are lost to the abiotic environment –> not sustainable
Less and less energy and organic compounds are available at higher trophic levels to be converted into biomass.
Oragnisms cannot convert heat energy into other forms –> can only be lost to the environment only produced.
Describe the process of methanogenesis
Production of methane from organic matter in anaerobic conditions by 3 different groups of methanogenic archaeans.
Steps:
1. Convertion of organic matter into a mixture of organic acids, alcohol, H2 and CO2
2. Convertion of organic acids and alcohol into acetate, CO2 and H2.
3. Production of methane by either 1) breaking down of acetate; or 2) Anabolizing CO2 and H2
What happens to carbon dioxide when it dissolves in water?
- Remain as a dissolved gas (CO2)
- Forming carbonic acid, which can dissociate to form H+ ions and HYDROGEN CARBONATE ions
Both forms of CO2 can be absorbed by plants for photosynthesis. *In terresterial plants, the absorption process is relatively less efficient, since CO2 can only be absorbed through stomata on the underside of leaves, whereas in aquatic plants, the entire surface of leaves and stems are permeable (–> diffusion can take place at any part of aquatic plants).
Why methanogensis is not an example of chemotroph?
Methane is produced from organic matter, not inorganic.
Chemotroph is the convertion of inorganic matters into organic matters.
Prerequisites of methanogenesis
O2-difficient environments: water-logged soil (e.g. wetlands, swamps), landfill sites, guts of some mammales (e.g. cattle and sheep), in the bed of lakes (still water)
Methanogenesis is carried out by anaerobic reactions in archaeans.
Some methane produced are trapped and buried as a fuel.
Oxidation of methane
Methane can be oxidized by monatomic oxygen (O) and highly reactive hydroxyl radicals (OH)
Methane + hydroxyl radical –> CO2 +H2O
Peat formation
Accumulation and compression of partially decomposed organic materials.
Partial decomposition due to anaerobic environment + acid conditions.
Anaerobic –> lack of O2 supply for decomposers to thrive
Acid –> inhibiting activities of saprotrophs
Formation of coal
Formed when deposits of peat are buried, compressed and heated, during the Carboniferous period, when there was a cycle of sea level rises and falls.
Formations and destructions of coastal swamps allows peat to be buried.
Combustion
An oxidation reaction
when a matter is heated to its ignition temperature
in the presence of O2
Products of complete combustion: CO2 and H2O
Formation of oil and natural gas
Formed in the mud at seafloors/lake beds, where there is deficient oxygen supply –> incomplete decomposition.
Partially decomposed materials are compressed and heated by mud and other sediments deposited at the bottom of the water.
Crude oil and natural gas are captured by POROUS rocks (e.g. limestones) and also be impermeable rocks above and below the porous ones to prevent escapes of the deposits
Examples of combustion taking place due to natural/human influences
Natural: areas experiencing periodic forest/grassland fires. Plants are well adapted and can regengerate rapidly afterwards.
Human caused: burning off of dry leaves before harvests of sugar canes
Formation of limestones
Formed by deposits of calcium carbonate shells from animals with hard body parts (e.g. mollusc). These shells usually remain in the environment, as long as the conditions are neutral (if the environment is acidic, calcium carbonate can easily dissolve away).
Direct and indirect effects of high atmospheric green-house gases
Photosynthesis rates of plants;
The pH of seawater; –> bleaching of corals
Global temperature;
The extent of ice sheets at the poles;
Sea levels and the position of coast lines;
Ocean currents –> western coasts of UK may become colder due to lack of warm North Atlantic Currents
Inequal distribution of rainfall: some areas draught v.s. some areas flooding;
Increased frequency and severity of extreme weather events (e.g. tropical storms with higher wind speed)
More frequent and protracted periods of rainfall;
Increased in the Q of rain delivered during thunderstorms and other intense bursts;
Why Mauna Loa Observatory’s data is trustworthy?
Isolated island of Hawaii with minimal human activities/influences on CO2 data (e.g. no big factories/power plants).
Provides data for CO2 level in the NORTH HEMISPHERE
Identify the four greenhouse gases
- Methane (+ methanogenesis, extraction of FF, melting ice in polar regions, - oxidation by monatomic oxygen/hydrogen radical)
- Carbon dioxide (+ respiration, combustion, - photosynthesis, dissolving into oceans)
- Water vapour (+ evaporation, transpiration, - rainfal)
- Nitrogen oxides (+ bacteria, vehicle and agricultural exhausts)
All together accounts for 1% of the total atmospheric gases –> significant impacts
The other term with the same meaning of “human-caused”
Athropogenic
The impacts of green-house gases depend on…
- Amount present: rate at which gas is released; how long it stays in the atmosphere;
- How readily the gas absorbs long-wave infrared radiation from earth
Explain the mechanisms of the greenhouse effect
- 75% of UV radiation (short WL) penetrates the atmosphere and reaches the ground; (the other 25% is being absorbed by gases in the atmosphere)
- The earth absorbs the SWL solar energy and re-emit it in LWL IR radiaion
- 85% of the re-emited radiation is captured by GH gases, which are particularly effective in absorbing LWL radiation;
- Re-emit of IR radiation from GH gases towards the Earth –> heating up
Important for lives: without GH effect, the temp on Earth would be ~-18℃
Analysis of global temp and CO2 concentration
Data of 400,000 years
Shows repeating patterns of rapid periods of warming followed by longer periods of gradual cooling
Strong correlation, but not causation
Most, but not all rises and falls in CO2 are correlated with fluctutations in temp –> there are too many determinants of temp (e.g. earth orbits, sun-spot activities)
Extraction of columns of ice in the South Pole
Temp: analysis of ratios of O and H isotopes in H2O
CO2: air bubbles trapped in ice
Coral reefs and CO2
30% acidification of seawater –> bleaching of corals
* By 2100, seawater will be 150% more acidic than it was in the 18th century
Acidification –> unfavourable environment –> zone of tolerance –> expel of zooxanthellae –> bleaching
Harder for marine calcifying animals to deposit calcium carbonate in their skeletons:
- When carbonic acid dissociates, H+ ions are formed, which react with dissolved carbonate ions (which are necessary for building reefs), and reduce their concentration [carbonate is very insoluble in water –> present in low concentration –> H+ reduce its concentration to even lower]
- Calcium carbonate tends to dissolve in acidic conditions/conditions where there isn’t saturated level of carbonate ions in water –> existing skeletons are threatened
- Shelled animals are often key-stone species –> entire communities can be affected
- On the other hand, zooxanthellae and other marine plants may be benefited –> higher photosynthesis, as CO2 was a limiting factor
Unit of fluxes in carbon cycles
Gigatonnes
Claims for climate change
Strong correlation over 400,000 years
Ice column evidence
Generally accepted by the professional scientific community
Increase in CO2 and temp accelerates since the industrial revolution
Precautionary principle: always prepare for the worst
Claims against climate change
Correlation, not causation
Natural fluctuations in CO2 and temp
We are at the end of a natural ice-age
Mini ice age in Europe during the 1500s –> discrepancy
The increase in average global temperature began thousands of years before the increase in the average global CO2 concentration
One example of terrestrial FC
chaparral plants –> kangaroo rats –> gopher snake –> roadrunner –> bobcat
One example of marine FC
phytoplankton –> salt-water shrimps –> herrings –> Northern Rightwhale dolphines –> killer whales
