Content

Question 1

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What is an open system?

Answer 1

Energy and matter are exchanged across bounderies.

Question 2

What is a closed system?

Answer 2

Energy but not matter is exchanged across bounderies.

Question 3

What is an ecosysem?

Answer 3

An ecosystem is a group of organisms which interact with each other and the surrounding enviroment so that matter is exchanged between the biotic and abiotic parts of the system.

Question 4

In the systems approach ecosystems can be views as systems with inputs, processes and outputs, describe a cycle to explain this.

Answer 4

Inputs (CO₂, O₂, sunlght, soil, vegitation and precipitation) ⇒ Processes and stores (photosynthesis, respiration, trees, soil, animals and litter ⇒ Outputs (CO₂, organic matter, nutrients, runoff, leaching, heat, water vapour) ⇒ positive and negative feedback ⇒ inputs

Question 5

How do plants use the carbonates prodcued in photosynthesis?

Answer 5

• 20% → respiration
• starch and cellulose (growth)

Glucose is being reffered to as carbonates

Question 6

What are the different tropic levels in a food chain?

Answer 6

autotrophs/primary producers → herbivores/primary consumers → carnivores/secondary consumers → tertiary consumers → saprophytes and detrivtivores

Question 7

Why is energy lost at each tropic level?

Answer 7

• not all food is digested (bones/lignin)
• some plants and animals are not consumed
• energy-consuming activities (chewing, movement, sexy-times (mating), catching prey
• plant and animal respiration and excretion → heat
• body mass radiates heat

Question 8

Which nutirents are involved in nutrient cycles?

Answer 8

Phophorus, nitrogen, iron along with trace elements are essential nutrients.

Question 9

How are nutrients recycled in nutrient cycles?

Answer 9

Nutrients recycled between the biomass, litter and soil stores. Losses such as surface run-off and leaching are balanced by inputs such as rock weathering, decomposition, cation exchange (soil) through roots and precipitation.

Question 10

Define a food chain.

Answer 10

A chain of organisms through which energy flows.

Question 11

Define a food web.

Answer 11

A group of interacting food chains within a community of organisms.

Question 12

What is a drawback of a food web?

Answer 12

They attempt to show more complex feeding patterns but have drawbacks in that energy losses and the relative importance of individuals are not taken into account.

Question 13

What is a drawback of a grazing food chain?

Answer 13

Simplistic model → Ignore that many animals feed on whats availible.

Question 14

How do humans alter nutrient cycles?

Answer 14

• harvesting crops removes nutrients
• adding manure. nitrate, phospahte and postash mineral fertilisers
• buring vegetation releases ash rich in phosphorus and potassium
• Grazing livestock producs waste products - humous - but when lifestock are removed biomass decreases
• logging → reduced interception, run-off and infiltration removes nutrients (leaching)

Question 15

What is a cation exchange?

Answer 15

Cation exchange; the process by which nutrients such as calcuim which are attached to the clay humus particles, are exchanged for hydrogen ions on the plant root and nutrients are taken up into the plant.

Question 16

What is are clay-hummous complexes?

Answer 16

Clay humus complexes - tiny fragments of humus and clay which have negative surfaces onto which positively charged nutrients become attached.

Question 17

Define mycorrhiza.

Answer 17

an association between plant roots and fungi which is beneficial to both partners.

Question 18

What can cause change in ecosystems and enviroments?

Answer 18

• Natural disaster → dramatic change e.g. erruption
• Fire → wipes out systems / helps germination
• Climate → inputs (rain and light) + outputs (evapouration), flows - warm Vs cold
• Drainage → lowers water table dries soil, floods - waterlogs
• Short term → seasonal fluctuations - loose leaves (shedding leaves to offset drought
• Long term → primary and secondary sucsessions.

Question 19

Describe primary sucession.

Answer 19

• Plant sucsession that dvelops on ground which has not been habituated before.
• Bare rock is known as lithosphere, sucession that develops on sand dunes is known as psammosere.
• By the process known as facilitation a new community becomes established.
• Reaches a situation in equilibrium with its surrounding (climax commuity)

Question 20

What is physiological drought?

Answer 20

Condition created when soils are too cold for roots to extract water, hence the plant sufferes from drought.

Question 21

What human effects cause change in ecosystems and enviroments?

Answer 21

• Trampling → crushed plants reduces soil porosity (compact)
• Settlement → clears vegetation and creates impermeable surfaces
• Transport → pollution causes soil acidity, and kills vegetation such as lichen.
• Power production → fossil fuels causes acid rain and global warming.
• Draingage → lowers water table and causes dry soil and drought.
• Mining and quarying → removal of vegetation and soil.
• Agriculture → addds chemicals, introduces and removes species, compacts soil, grazing, drainage and irrigation.

Question 22

What is a secondary succession?

Answer 22

Secondary successions occur on formerly vegetated surfaces. A naturally occuring event such as a forest fire can be responsible for the clearance.

Question 23

What is a plant community permenantly halted by human activity?

Answer 23

A phagioclimax.

Question 24

What are the causes of human impacts and threats on woodlands?

Answer 24

• Agriculture
• Settlement / industry
• Recreation
• Pollution
• Invasive species/disease

Question 25

Describe agriculture as a human threat to a woodland ecosystem.

Answer 25

• Intensification of agriculture, the intensification of agriculture since 1945 destroyed a lot of ancient and ancient semi-natural woodland.
• Remaining fragements too small to support vible populations of plants and animals.
• Field drainage, nutrient enrichment from nitrate fertiliser and agricultral sprays have all changed species compositions along woodland edges.

Question 26

Describe settlement/industry/infastructure/spraying as a human threat to a woodland ecosystem.

Answer 26

• New roads and the widening of exisiting ones.
• Airport quarry expansion.
• Construction of industrial estates, housing, superstore, telecommunication towers and leisure → direct loss of woodland habitats.
• Where trees have been spared, the new developments have altered local hydrology and sometimes caused air pollution which has affected neaby woodland.

Question 27

Describe recreation as a human threat to a woodland ecosystem.

Answer 27

New forest → horse riding, off-road parking and footpath trampling draingage soils and vegetation.

High traffic volumes on roads which cross the forest cause noise and air pollution and disturb wildlife, especially ponies.

Dogs chase wild animals and disturb ground-nesting birds, while picnicking increases fire risk.

Question 28

Describe pollution as a human threat to a woodland ecosystem.

Answer 28

• Prior to Clean Air acts (1950’s), smog reduced light levels in urban areas such as London, which encouraged deciduous trees to shed their leaves prematurely.
• Coniferous trees, which grow in acid soils, are particulay prone to the damaging effects of rain becuase a decline in pH makes the soil toxic.
• Plant nutrients such as calcium, magnesium and potassium are leached from the soil by acidic water.
• Micro-organisms, which normally decompose organic matter, are also less active in acidic conditions.
• Tolerance varies (birch susceptable, London plane resistant)
• Desciduoud trees growing near roads → damaged by emissions of N₂O, particulates (un-burnt fine carbon) and CO.
• Heavy metals emitted from smelters turn leaves yellow and slows down micro-biological activity.

Question 29

Describe an exmaple of an invasive species forming a human threat to a woodland ecosystem.

Answer 29

Sycamore, an invasive species first introduced from central Europe may centuries aga, has spread throughout woodlands displacing native trees.

Question 30

Describe disease an an human threat to a woodland ecosystem.

Answer 30

• Dutch elm → introduced accidnetly from North Amercia in imported logs in the 1970’s, altered the structure and composition of woodland and continues to affect them.) trees died - alder repopulated)
• Ash Dieback
• Sudden Oak death, a fungal disease first identified in California in 1995, spread to English oak woodlands.

Question 31

Describe conifer plantations as a human threat to a woodland ecosystem.

Answer 31

Up to 1980’s, conifers were often planted within deciduous woodlands. The trees aciified the soil, altere species compostitions, and their dense spreading branches prevented light reaching the woodland floor, eliminating shruba nd herb layers.