Chapter 4. Ecology

Question 0

Species

Answer 0

Groups of organisms that can potentially interbreed to produce fertile offspring.

Question 1

Cross-breeding

Answer 1

Members of different species breed together.

Question 2

Reproductive separation…

Answer 2

Prevents the genes of two species from mixing together.

Question 3

Population

Answer 3

A group of organisms of the same species living in the same area at the same time.

Question 4

Autotrophic

Answer 4

Self-feeding: makes their own carbon compounds from carbon dioxide and other simple inorganic substances.

Example: Arabidopsis thaliana (a model plant most commonly used)

Question 5

Hetertrophic

Answer 5

Feeding on others (includes consumers, saprotroohs and detritus ores): organisms obtain their carbon compounds from other organisms.

Example: humming bird.

Question 7

Mixotrophic

Answer 7

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.

Question 7

Consumers

Answer 7

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).

Question 8

Parasitic plants and algae

Answer 8

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)

Question 9

Carrion

Answer 9

Dead animal remains.

Question 10

Detritivores

Answer 10

Heterotrophs that obtain organic nutrients from detritus by internal digestion (ingestion –> digestion).

Example: earthworms.

Question 11

Dichotomous key

Answer 11

二叉式检索表

Question 12

Saprotrophs

Answer 12

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.

Question 13

Quadrats

Answer 13

Quadrats are square sample areas marked out by a quadrat frame.

Question 14

Community

Answer 14

Populations of different species living in the same area at the same time and interacting with each other.

Example: a coral reef.

Question 15

Nutrient

Answer 15

An element which an organism needs.

Question 16

Ecosystem

Answer 16

A single highly complex INTERACTING system which consists of communities of organisms in an area and the abiotic environment which they live in.

Question 17

Sustainability

Answer 17

The ability to continue a defined behaviour indefinitely.

Question 18

Mesocosms

Answer 18

Small experimental areas that are set up as ecological experiments.

Question 19

Food chain

Answer 19

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.

Question 20

The laws of thermodynamics state that…

Answer 20

1) Energy transformations are never 100% efficient.

2) Hear passes from hotter to cooler bodies.

Question 21

Pyramids of energy

Answer 21

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.

Question 22

Biomass

Answer 22

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.

Question 23

Examples of sources of nutrition for detritivores and saprotrophs

Answer 23

1. Dead leaves and other dead organic matter discarded by plants;
2. Feathers, hairs, dead skin cells etc.
3. Faeces;

Question 24

Why are saprotrophs also known as decomposers?

Answer 24

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.

Question 25

Describe the steps of quadrating

Answer 25

1. Divide the investigated field into grided areas using two perpendicular lines marked by measuring tapes
2. Use a random number generator/table to generate random coordinates, which determine the positions at where quadrats will be placed
3. Place the quadrat frame and count the percentage coverage /number of species using the grids
4. 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

Question 26

Example of abiotic environment influencing living organisms

Answer 26

Salty sea water creates a very specialized habitat and only mangroves (trees adapted to high-salinty soil) are able to survive

Question 27

Example of organisms influencing abiotic environment

Answer 27

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.

Question 28

Sustainability and example

Answer 28

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

Question 29

3 requirements for sustainability in ecosystems

Answer 29

1. Nutrition sustainability
2. Energy availability
3. 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.

Question 30

Applications of mesocosms

Answer 30

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)

Question 31

Key questions to ask when setting up a mesocosm

Answer 31

1. Energy availability: will there be enough energy created by producers for the rest of the community?
2. Oxygen availability: will there be enough oxygen created by producers for the rest of the community?
3. Nutrition sustainability: how can nutritions be recycled?
4. Detoxification of wastes: will the wastes be potentially toxic? Which organisms are able to detoxify the wastes?
5. Ethics: how to avoid causing harm/pain to the organisms

Question 32

Examples of producers

Answer 32

Plants
Eukaryotic algae
Cyanobacteria

They are all capable of converting light energy/chemical energy into chemical energy.

Question 33

Define chemostroph and give examples

Answer 33

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

Question 34

Why energy transfers can never be 100% efficient between trophic levels?

Answer 34

The second law of thermodynamics

1. Lost during metabolism (e.g. cellular respiration: the process of transferring energy in glucsoe and lipids to ATP)
2. Lost as heat to the abiotic environment in cellular activities: muscles warming up during exercise
3. Uningested
4. Undigested

Question 35

Carbon fixation

Answer 35

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

Question 36

Why the length of food chains are restricted? Why does the biomass pyramids have wider base and narrower tops?

Answer 36

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.

Question 37

Describe the process of methanogenesis

Answer 37

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

Question 38

What happens to carbon dioxide when it dissolves in water?

Answer 38

1. Remain as a dissolved gas (CO2)
2. 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).

Question 39

Why methanogensis is not an example of chemotroph?

Answer 39

Methane is produced from organic matter, not inorganic.

Chemotroph is the convertion of inorganic matters into organic matters.

Question 40

Prerequisites of methanogenesis

Answer 40

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.

Question 41

Oxidation of methane

Answer 41

Methane can be oxidized by monatomic oxygen (O) and highly reactive hydroxyl radicals (OH)
Methane + hydroxyl radical –> CO2 +H2O

Question 42

Peat formation

Answer 42

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

Question 43

Formation of coal

Answer 43

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.

Question 44

Combustion

Answer 44

An oxidation reaction
when a matter is heated to its ignition temperature
in the presence of O2
Products of complete combustion: CO2 and H2O

Question 45

Formation of oil and natural gas

Answer 45

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

Question 46

Examples of combustion taking place due to natural/human influences

Answer 46

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

Question 47

Formation of limestones

Answer 47

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).

Question 48

Direct and indirect effects of high atmospheric green-house gases

Answer 48

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;

Question 49

Why Mauna Loa Observatory’s data is trustworthy?

Answer 49

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

Question 50

Identify the four greenhouse gases

Answer 50

1. Methane (+ methanogenesis, extraction of FF, melting ice in polar regions, - oxidation by monatomic oxygen/hydrogen radical)
2. Carbon dioxide (+ respiration, combustion, - photosynthesis, dissolving into oceans)
3. Water vapour (+ evaporation, transpiration, - rainfal)
4. Nitrogen oxides (+ bacteria, vehicle and agricultural exhausts)

All together accounts for 1% of the total atmospheric gases –> significant impacts

Question 51

The other term with the same meaning of “human-caused”

Answer 51

Athropogenic

Question 52

The impacts of green-house gases depend on…

Answer 52

1. Amount present: rate at which gas is released; how long it stays in the atmosphere;
2. How readily the gas absorbs long-wave infrared radiation from earth

Question 53

Explain the mechanisms of the greenhouse effect

Answer 53

1. 75% of UV radiation (short WL) penetrates the atmosphere and reaches the ground; (the other 25% is being absorbed by gases in the atmosphere)
2. The earth absorbs the SWL solar energy and re-emit it in LWL IR radiaion
3. 85% of the re-emited radiation is captured by GH gases, which are particularly effective in absorbing LWL radiation;
4. 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℃

Question 54

Analysis of global temp and CO2 concentration

Answer 54

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

Question 55

Coral reefs and CO2

Answer 55

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:

1. 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]
2. 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

Question 56

Unit of fluxes in carbon cycles

Answer 56

Gigatonnes

Question 57

Claims for climate change

Answer 57

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

Question 58

Claims against climate change

Answer 58

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

Question 59

One example of terrestrial FC

Answer 59

chaparral plants –> kangaroo rats –> gopher snake –> roadrunner –> bobcat

Question 60

One example of marine FC

Answer 60

phytoplankton –> salt-water shrimps –> herrings –> Northern Rightwhale dolphines –> killer whales