Ecosystems

Question 1

What is a population?

Answer 1

A group of organisms of the same species that live together in the same area at the same time so can interbreed

Question 2

What is a species?

Answer 2

A group of organisms with similar features that can freely interbreed to produce fertile offspring

Question 3

What is a community?

Answer 3

All the populations of difference species that live and interact in the same area at the same time

Question 4

What is a habitat?

Answer 4

The physical environment than an organism is found in

Question 5

What is a niche?

Answer 5

The role each organism plays in an ecosystem. It includes its habitat, the resources it uses, and its interactions with other organisms

Question 6

What is a producer?

Answer 6

Autotrophic organisms that convert light energy to chemical energy via photosynthesis, which they then supply to consumers

Question 7

What is a decomposer?

Answer 7

Organisms that feed on dead organic matter that then become available to other living organisms in that ecosystem

Question 8

What is a trophic level?

Answer 8

The level at which an organism feeds in a food chain. E.g, producer or secondary consumer

Question 9

What is an autotroph?

Answer 9

An organism that synthesises complex organic molecules from inorganic molecules, e.g CO2 and H2O.
Photoautotrophs use sunlight as their energy, chemoautotrophs use energy from chemical reactions

Question 10

What is a heterotroph?

Answer 10

Cannot fix carbon and gains their carbon by eating other organisms and taking in organic carbon

Question 11

What is biomass?

Answer 11

Dry mass of all the living material of an organism
Proteins, carbohydrates, nucleic acids and fats
What organism has synthesised, using energy (water not included)
What is made in growth, available for next trophic level
Can be calculated for an individual organism or for T-L in a set of land/water

Question 12

What is a pyramid of numbers?

Answer 12

Shows number of species at each level

Question 13

What is the issue with a pyramid of numbers?

Answer 13

Not always representative of interactions of biomass availability in ecosystem

Question 14

What is a pyramid of energy?

Answer 14

Shows how much energy is in the biomass available to the next trophic level, recorded in a set area over set length of time, measured in KJm^-2y^-1

Question 15

What is the advantage of using a biomass pyramid?

Answer 15

More representative of biomass availability in ecosystem

Question 16

What are phytoplankton? What is their biomass compared to zooplankton?

Answer 16

Tiny, microscopic organisms
-Mass present at any one time is low BUT lifecycle is short and rapid, and over a long period of time their collective biomass is greater than zooplankton

Question 17

How much light is reflected off the surface of a leaf?

Answer 17

90%

Question 18

Why is not all light absorbed by the leaf?

Answer 18

Light may be transmitted through leaf as not hitting chloroplast
Light energy may be incorrect wavelength
Reflected

Question 19

What is NPP?

Answer 19

Net Primary Production - Biomass formed from remaining glucose after glucose used for respiration

Question 20

What is GPP?

Answer 20

Gross Primary Production - total solar energy used to make glucose
- Plants use some of glucose produced in respiration, so cannot be used to create biomass

Question 21

What is net secondary production?

Answer 21

Generation of biomass (growth) in a consumer

Question 22

List reasons as to why not all producer biomass is converted into consumer biomass

Answer 22

-Not all of plant is eaten
-Not all is digested
-Some lost a faeces
-Energy lost as urine
-Energy in form of heat lost via respiration
-Respiration vital to release energy for life processes (active transport, muscle contraction, heat generation in endotherms)

Question 23

Explain why transfer of biomass from producer to primary consumer is less than that transferred from primary to secondary

Answer 23

Primary consumers eat plants, a lot of biomass in form of indigestible cellulose as lack cellulase. Secondary consumers eat animals, the biomass is in form of fats, carbs, proteins, which secondary consumers have enzymes for, digest it, less biomass lost

Question 24

What is the equation for ecological efficiency?

Answer 24

(Energy or biomass available after the transfer/energy or biomass available before the transfer) x 100

Question 25

What is productivity?

Answer 25

Rate of new biomass production Measured in set area over set time g m^-2 yr^-1

Question 26

How can humans manipulate light levels for productivity?

Answer 26

Lamps at night/during winter Cover up to reduce light intensity

Question 27

How can humans manipulate availability of water for productivity?

Answer 27

Rain cannot enter as roof closed off to outside (greenhouse) Watering system to control water to each plant, ensure they survive

Question 28

How can humans manipulate temperature for productivity?

Answer 28

Open doors, windows Lamps, fans

Question 29

How can humans manipulate availability of nutrients for productivity?

Answer 29

Composition of soil, control what is in it Fertiliser

Question 30

How can humans manipulate pests for productivity?

Answer 30

Greenhouse closed off, prevents pests from entering Can use pesticides, prevention methods to prevent pests eating crops

Question 31

How can humans manipulate fungal diseases for productivity?

Answer 31

Closed off, prevent spores from entering the greenhouse Prevent soil contamination

Question 32

How can humans manipulate competition for productivity?

Answer 32

Can remove weeds, weed killer, by hand Control plants, where they are, space they have, able to maximise growth

Question 33

How can biomass and energy content of organisms be measured?

Answer 33

Select food chain Measure population size of each species, involve sampling and estimation calculation of population size in area Calculate mean dry mass of single organism: kill, dry in oven at 80C to evaporate water, heating and reweigh until constant mass occurs Assume organism is average, multiply dry mass for one specimen by number in pop, giving biomass of pop at target location Energy content per gram of BM caculated for each, calc by burning sample, in colourimter, measure heat, assume heat energy equated energy content Multiply energy content/g by total biomass, obtain total energy conent locked in BM of pop of target loc.

Question 34

What is decomposition?

Answer 34

Process by which dead organic matter is broken down into simpler substances by decomposers

Question 35

What are decomposers?

Answer 35

Organisms, primarily bacteria and fungi, that break down dead organisms and organic waste, releasing nutrients back into the ecosystem.

Question 36

Decomposers are saprotrophs. What are saprotrophs?

Answer 36

Gain energy from dead or waste matter Extracellular digestion Secrete enzymes which hydrolyse complex organic molecules into smaller, soluble ones, which are absorbed Molecules then stored or respired to release energy.

Question 37

Draw the nitrogen cycle

Question 38

Outline nitrogen fixation and the bacteria involved

Answer 38

Combining atmospheric nitrogen gas with hydrogen to form ammonia Nitrogen fixing bacteria, azobacta and rhizobium

Question 39

Outline denitrification and the bacteria involved

Answer 39

Lack of oxygen (could be due to water logged soil, for example), causes nitrates in the soil to be converted back to nitrogen gas Denitrifying bacteria, no specific example required

Question 40

Outline ammonification and the bacteria involved

Answer 40

Conversion of nitrogen containing molecules in dead organisms, faeces and urine into ammonium compounds Putrefying bacteria, no specific example reuqired

Question 41

Outline nitrification and the bacteria involved

Answer 41

Ammonium compounds converted to nitrogen containing compounds, which plants are able to absorb Nitrifying bacteria, nitrosomonas, nitrobacter

Question 42

What is succession?

Answer 42

A progressive change in a community obver time in an area It is a directional change, irreversible, ONE DIRECTION Species living there at one time with alter abiotic conditions of habitat New species able to colonise due to the change Better adapted to new conditions, outcompete original species Original species dies out Populations have changed

Question 43

What is primary succession?

Answer 43

Occurs in area without soil, growth for first time Eg: cooled lava flows, sand dunes, silt/mud deposits at river esturies

Question 44

What is secondary succession?

Answer 44

Developed ecosystem disturbed, soil already existed but no plant/animal species Eg: after forest fire

Question 45

What is soil

Answer 45

Fine stones/sand Humus - dead organic matter - contains mineral ions (eg nitrates) - holds water - stabilises soil

Question 46

What are the features of a pioneer community?

Answer 46

Ability to produce a large number of seeds or spores that can be blown in the wind and deposited on new ground Rapidly germinating seeds, rapid life cycles Photosynthetic, their only resouces are light, rain and carbon dioxide Tolerant to extreme environments May have ability to fix nitrogen, thus putting nitrates into soil when decay Highly specialised plants Low biomass per unit area, few small plants Biomass can fluctuate greatly

Question 47

What are the features of an intermediate community?

Answer 47

Secondary colonisers, followed by tertiary colonisers On death and decay, alter ground Each species creates, alters and improves the soil, this altering abiotic conditions Species richness increases Environment less extreme, more plant species can colonise Biomass /^2m imcrease

Question 48

What are the features of a climax community?

Answer 48

Very stable community Change very little Complex food webs Nutrient recycling High biomass per unit area as ground densely populated, and plants larger

Question 49

What is deflected succession?

Answer 49

When human activities alter normal flow of succession, and prevent ecosystem reaching climax community Plagioclimax is final stage is human activity has stopped succession Eg. grazing, mowing, crop planting