Ecosystems

Question 1

What is an ecosystem

Answer 1

All the interacting living organisms & non-living factors in a particular in a particular area - this is a dynamic system, & varies in size too e.g. a rock field, a playing pool, a large tree

Question 2

What’s a community

Answer 2

All populations of all species in a particular habitat

Question 3

What is a population

Answer 3

All the individuals of one slices in a particular habitat

Question 4

What is a ‘species’

Answer 4

Can reproduce to produce fertile offspring

Question 5

Biotic vs Abiotic factors

Answer 5

Biotic = living factors that affect it e.g. competition, predation, disease
Abiotic = non-living factors that affect it e.g. light, pH on soil, temp, water & O2 availability

Question 6

What is a niche

Answer 6

The role of a species in an ecosystem

Question 7

Types of changes in ecosystems

Answer 7

Cyclical (repeat in rhythm e.g. tides)
Directional (e.g. go in 1 direction, lasting life, like erosion)
Erratic/ Unpredictable = no rhythm / direction (natural disasters)

Question 8

What is a tropic level

Answer 8

The stage in food chain
Order = producers -> primary consumers -> secondary consumers -> tertiary consumers -> apex predator

Question 9

What is biomass

Answer 9

The dry mass (without water) of living material in an area / organism
-> we consider this: > mass as water levels can fluctuate within the organism, depending on time of day / year / area

Question 10

How is biomass measured

Answer 10

Using calorimeters:
- collect the sample, kill the organism, put it in the over @ 80° to remove the water by evaporation & stop once a constant mass has been reached

Question 11

What are the limitations of calorimeters

Answer 11

• can take a long time to fully dehydrate sample
• precise equipment needed
• heat energy lost by calorimeter & not efficiently transferred

Question 12

Land animals vs marine animals unit

Answer 12

G/m^2 vs G/m^3

Question 13

Ecological efficiency formula
(The efficiency with which biomass is transferred between consecutive tropic levels)

Answer 13

Question 14

How can energy be lost in a food chain

Answer 14

• sunlight reflected so not all used in photosynthesis
• other factors affect photosynthesis rate
• hear energy from respiration
• process of excretion & production of waste materials
• some parts of food not eaten / digested

Question 15

What is ‘useful energy’

Answer 15

Used to build biomass / body growth

Question 16

How can we make biomass transfer efficiency of consumers

Answer 16

1. Vaccinate animals / provide antibiotic (less energy loss to pathogens)
2. Restrict animal movement - less e loss via respiration
3. Harvest @ peak times (animals can’t grow anymore as adults so don’t waste e on them)
4. Plants planted earlier (longer growing seasons, more light etc)
5. Maintain nutrient rich soil (crop rotation)

Question 17

Decomposers vs detrivores

Answer 17

Decomposers feed on dead organic matter (secrete enzymes, digest externally, absorb matter)
Detrivores different as they digest internally & increase the SA of the matter to inc rate of decomposition

Question 18

Steps in nitrogen cycl

Answer 18

1. Nitrification
2. Ammonification
3. Denitrification
4. Nitrogen fixation

Question 19

What happens in stage 1 (Nitrification)

Answer 19

ammonium ions -> nitrite ions -> nitrate ions
(Oxidation, therefore requires oxygen (well aerated soils))

Question 20

Nitrifying bacteria in Nitrification

Answer 20

Nitrosomonas
Nitrobacter

Question 21

Nitrosomonas action

Answer 21

Ammonium -> nitrite

Question 22

Nitrobacter action

Answer 22

Nitrite -> nitrate

Question 23

What happens in Ammonification (stage 2)

Answer 23

Carried out by decomposers

Nitrite / nitrate -> ammonium ions -> ammonia

Question 24

Denitrification (stage 3) - what happens

Answer 24

Nitrate ions -> nitrogen gas
Anaerobic conditions (as there are water logged soils, so low O2 levels)
Denitrifying bacteria = Pseudomonas

Question 25

What happens in stage 4 nitrogen fixation

Answer 25

Atmospheric nitrogen gas + 3H2 (g) -> 2Ammonia - nitrogen fixing bacteria (Azotobacter & Rhizobium) Nitrogen needed to make amino acids & nucleic acids

Question 26

Where are azotobacters found

Answer 26

Free living

Question 27

Where are rhizobiums found

Answer 27

in root nodules

Question 28

Nitrogen cycle diagram

Answer 28

Question 29

What is primary succession

Answer 29

A newly formed / exposed land with no species present is gradually colonised by an increasing number of species This causes the biotic components of the eco system to change over time

Question 30

What is a pioneer species

Answer 30

The 1st species to colonise the land -> autotrophic + able to survive harsh environmental conditions

Question 31

What is a climax community

Answer 31

When the final species colonises land -> becomes a dominant species in an ecosystem - most complex & diverse community the ecosystem can sustain

Question 32

Succession process

Answer 32

1) pioneer species begins to grow 2) this species changes abiotic conditions, therefore less hostile 3) pioneer species die and decompose 4) dead organic matter forms deeper & more nutrient rich soil 5) new species able to grow in less harsh conditions 6) new species outcompetes the pioneer species & previous species 7) changes the abiotic conditions so less hostile to next new colonising species, & less suitable for older ones 8) previous species die, soil deeper & more nutrient rich as a result 9) cycle repeats 10) eventually, climax community reached

Question 33

What is deflected succession

Answer 33

When human activities prevents /interrupt the process, resulting in a different climax community than what would be from natural succession

Question 34

How can human activities prevent succession & why is this good

Answer 34

E.g. - managed burning, mowing lawns, introducing grazing animals This can be good as it maintains high plant & animal diversity, which won’t exist if the climax community is reached

Question 35

What is a sere

Answer 35

Each level of succession

Question 36

Details about the Masai marai

Answer 36

- savannah in Africa - people raise livestock - ecotourism projects, where people employ locals to monitor lions, as conservation trusts help locals make money

Question 37

Details about the terai region in Nepal

Answer 37

Grassland, & forest, & variety of plants & animals -> densely populated region therefore highly dependent on natural resources E.g. fuel, animal feed, human food, medicines -> conservation chattiest have worked to conserve the forest e.g. protecting against poaches teaching locals forestry skills

Question 38

Peat bogs details

Answer 38

Areas of water logged land (incomplete decomposition) Anaerobic & acidic conditions = decomposed plant matter accumulates and becomes compacted & = PEAT, which builds up to form carbon store -> this carbon store is exploited & burns as fossil fuels, even tho the peat supports lots of plant species & those in turn support intervertebrae