Ecosystems

Question 1

Habitat?

Answer 1

Place where an organism lives

Question 2

Population?

Answer 2

All the organisms of one species in one habitat

Question 3

Producer?

Answer 3

An organism that produces organic molecules using sunlight energy e.g plants

Question 4

Consumer ?

Answer 4

An organism that eats other organisms e.g animals/birds

Question 5

Decomposer?

Answer 5

An organism that breaks down dead or undigested organic material e.g bacteria/fungi

Question 6

Trophic level?

Answer 6

A stage in a food chain occupied by a particular group of organisms e.g producers are the 1st trophic level of the food chain

Question 7

Ecosystem?

Answer 7

An ecosystem is a community of living organisms (biotic factors) interacting with eachother and with their non living (abiotic) environment
- dynamic system - changes over time

Question 8

Abiotic/biotic factors on rock pools?

Answer 8

BIOTIC : seaweed is food source for consumers like limpets
- intense comp for food can limit no. Organism present in ecosystem

ABIOTIC : tides - can be completely submerged by ocean at high tides so experience similar abiotic factors : pH , Salinity , Temperature etc.
at low tide, more extreme abiotic factors ( higher salinity /temps) - only some organisms tolerate

Question 9

Playing field biotic/abiotic factors?

Answer 9

BIOTIC : large amounts of plants (producers) attract large number of organisms as FOOD SOURCE

ABIOTIC: rainfall/sunlight affect growth of producers —> heavy rain can cause soil to be waterlogged so hard for growth
- reduces no. Consumers the ecosystem can support

Question 10

Large tree biotic and abiotic factors?

Answer 10

BIOTIC: insects can use leaves of trees as FOOD SOURCE
- however overconsumption of leaves can slow tree growth /lead to death of tree

ABIOTIC : drought can lead to death of tree/negatively impact growth of tree

Question 11

What are biotic and abiotic factors and examples?

Answer 11

Biotic : living features of the ecosystem - predation/competition for food, water,light or space / disease / camouflage and mimicry /no. And types of animals/plants

Abiotic : non-living features of ecosystem - temperature /rainfall /soil nutrient availability /humidity /salinity/pH /turbidity (cloudiness) of water/light intensity

Question 12

What is biomass?

Answer 12

Total Mass of living material present at a particular time in a specific place or within certain organisms
Chemical energy that is stored within organism/tissue

Measured in g m-2 on land and g m-3 in aquatic environments

Question 13

What can biomass be measured in terms of?

Answer 13

Dry mass of organism /tissue
Mass of carbon that organism /tissue contains - generally taken as 50 % of dry mass
Chemical energy content of organism when burned in pure oxygen

Question 14

What is calorimetry used for? Process?

Answer 14

Used to estimate the chemical energy stored in dry biomass
1. Involves burning sample of dry biomass in calorimeter
2. Burning sample heats known volume of water
3. Change in temp of water provides an estimate of chemical energy the sample contains

Question 15

Why is a large proportion of sun’s energy not available for photosynthetic plants?

Answer 15

Light falls away from plants - misses chloroplasts
Light reflected by leaves- not all the light absorbed by chlorophyll
Light is a mixture of wavelengths - Only certain wavelengths stimulate photosynthesis

Question 16

Why is only a small percentage of biomass transferred to next trophic level?

Answer 16

• not all of plant’s biomass is eaten by primary consumer (may not be edible)
• not all consumer’s biomass intake is DIGESTED
• chemical energy is lost as heat during MOVEMENT or RESPIRATION- only small % of the energy is stored as new biomass
• energy is lost in excretory material (urine/faeces)
• Not all solar energy captured by leaves/is the correct wavelength for photosynthesis
• Energy lost during photosynthetic reactions
• water availability can limit photosynthesis (so less biomass produced (glucose)

Note:

ENERGY LOSSES mean there is less energy available to contribute to biomass of next trophic level so less biomass in next trophic level (as chemical energy is stored in biomass)

Question 17

Efficiency of biomass transfers between trophic levels EQUATION?

Answer 17

Efficiency of transfer = (biomass transferred / biomass intake ) x 100

Or
efficiency = net productivity of primary consumers/ net productivity of producers

Question 18

Net productivity of producers /net primary productivity (NPP) EQUATION? What is it?

Answer 18

Amount of energy available to next trophic level (Kj m-2 yr-1)
NPP = GPP - R
GPP = gross primary productivity (total amount of light energy that plants convert into organic matter storing it as chemical energy within their biomass)
R = respiratory losses

Question 19

Net productivity of consumers equation?

Answer 19

N = I - (F + R)

I = chemical energy store in ingested food
F = chemical energy lost to environment in faeces/urine
R = respiratory losses to environment

Question 20

How does human activity manipulate the efficiency of biomass transfer?

Answer 20

Farmers can increase agricultural productivity by increasing biomass transfers by:
For producers :
- Irrigation to maximise growth in dry weather
- Use of fertilisers - growth of plants
- Selective breeding for fast growth
- Use of fungicides/pesticides

For primary consumers :
- Use of good quality feeds / food supplements
- Use antibiotics and vaccines to reduce disease
- Control predation with fencing etc
- Intensive control of conditions to reduce energy loss from movement or from getting cold outside

Question 21

What are decomposers known as and how do they break down organic/waste matter?

Answer 21

Saprobionts - from fungi/bacteria kingdom

• They secrete enzymes onto dead organisms/waste material which digest the material externally - EXTRACELLULAR DIGESTION
  Products of extracellular digestion is then absorbed by SAPROBIONTS
  This method is known as SAPROBIOTIC NUTRITION
• not all products of extracellular digestion are absorbed by Saprobionts/many remain in surrounding for other organisms

Question 22

Why are Saprobionts essential ?

Answer 22

Nutrients would be locked up in dead/waste matter and wouldn’t be made available again for producers to use
- also some Saprobionts can excrete important nutrient mineral ions as waste products from their own metabolism

Question 23

What is mycorrhizae ?

Answer 23

The symbiotic (mutually beneficial) relationship between fungi and plants

Fungi’s hyphae interact with plant roots / increase SA of root system of plants —> INCREASE WATER AND MINERAL IONS ABSORBTION
- in return fungi receive organic compounds (e/g glucose) from plant

Question 24

Role/reactants and location of nitrogen fixing bacteria? (Azotobacter and Rhizobium species)

Answer 24

Convert gaseous nitrogen into AMMONIA (NH3) -ANAEROBIC process
Reactants: N2 + H+—> NH3 (reduction)
Location: leguminous root nodules
NH3 can be converted into amino acids

Rhizobium form mutualistic relationship with plants- provide plant with nitrogenous compounds /plant provides carbs to them
When Azotobacter die and are decomposed by Saprobionts , nitrogen rich compounds released + converted into a form that can be assimilated by plants - fix N2 into NH3 ,then into amino acids

Abiotic process: lightning, artificial fertilisers, haber process also fix N2

Question 25

Nitrifying bacteria role,reactants , location? (Nitrosomanas and Nitrobacter species)

Answer 25

Nitrify **ammonium ions into NITRITE (NO2 -) and nitrate (NO3 - )** - highly soluble and can be absorbed by roots BACTERIA FOUND IN **SOIL**: Nitrosomonas : **NH4+** —> NO2- (NITRITES) Nitrobacter : **NO2-** —> NO3- (NITRATES) - both oxidation

Question 26

Denitrifying bacteria role, reactants and location?

Answer 26

Use **nitrates for respiration** and **return gaseous nitrogen** back into atmosphere FOUND IN **SOIL** Reactants: **NO3-**—> N2 (reduction)

Question 27

What is the carbon cycle?

Answer 27

1.**photosynthesis** - autotrophs (makes their own food using light,water, CO2 and other chemicals) uses energy from sun to ‘fix’ carbon dioxide , turning CARBON —> SUGARS /ORGANIC MOLECULES Removes carbon from atmosphere 2. **Sedimentation** - body of dead plants not fully decomposed by Saprobionts - bodies form layer of sediment and accumulates over millions of years- locking carbon into ground - sediment is store of energy /form fossil fuels (e.g peat /coal) 3. **Respiration** - respiration puts CO2 back into atmosphere / released in LINK REACTION /KREBS CYCLE of aerobic respiration Anaerobic releases CO2 via fermentation by yeast, mould and bacteria 4. **Feeding**- Carbon passed from autotroph to heterotroph during feeding (primary to secondary consumer) 5. **Decay/decomposition** - dead plants/animals are fed upon by detritivores/decayed by saprophytes - release carbon to surroundings /supply detritivores and saprophytes with carbon

Question 28

How has burning fossil fuels caused climate change ?

Answer 28

CO2 is being **returned faster** than it can be **absorbed** by plants and aquatic producers Also warmer temps means **less co2 can dissolve** in oceans so released into air CLIMATE CHANGE as a result as CO2 is a greenhouse gas so traps heat from sun /affect habitats

Question 29

What is succession?

Answer 29

Progressive change in a community of organisms over time - biotic and abiotic conditions change over time

Question 30

What is primary succession?

Answer 30

Process that occurs **when newly formed/newly exposed land is gradually colonised** by an increasing no. Species Uninhabited land created by: Magma from volcanoes **cools/forms new rock surfaces** or even new islands in sea Sea level **dropping**/lake dry up —> leave areas of bare rock

Question 31

eg of barren terrain undergoing primary succession? What is a pioneer species?

Answer 31

Sand dunes in coastal areas - marram grass are the **pioneer species** in these environs as they have **deep roots to access water that otherwise plants can’t reach/can tolerate salty environment** **Pioneer species**: species that can **colonise bare rock or ground** (usually first living things there) /begins process of succession

Question 32

Stages of primary succession? What is a climax community?

Answer 32

1. **Seeds/spores** carried by wind ,land on exposed/bare rock and begin to grow - **pioneer species** (have adaptations e.g nitrogen fixation) These species die/decompose , dead organic matter (humus) **forms basic soil** 2. Seeds of **small plants/grasses** , carried by wind or other ways (by sea/bird faeces) **land on basic soil and begin to grow** - adapted to **survive shallow /nutrient poor soils** As these small plants die/decompose , **new soil becomes deeper and more nutrient rich / roots of these plants also form network that hold soil in place /prevent it being washed away** 3. **Larger plants /shrubs and small trees** that need deeper , more nutrient rich soil and water , can begin to grow 4. Soil is now **sufficiently deep**, contain enough **nutrients/water/nitrates** for growth of large trees —> DOMINANT SPECIES** (final species to colonise new land) —> now a complex ecosystem - **community changes** **Climax community** is formed : stable final community that exists in a balanced equilibrium after the process of succession has occurred

Question 33

Example of changing environ during succession?

Answer 33

1. Pioneer species grow on bare rock (lichens) help **break apart top surface of rock** Fragmented rock as well as humus left behind when lichens die, are broken down —> BASIC SOIL Lichen have changed local environment so it’s more suitable for other species (e.g mosses) 2. Mosses grow /soil builds up until **small plants and grass colonise** new land—> result in formation of **thin soil layer** that covers newly formed rock completely Lichen ***cannot grow on soil —> DISAPPEAR** from ecosystem - less suitable for lichens 3. Soil **deepens further** /trees grow that out compete shrubs and smaller plants due to **lack of light**

Question 34

What is deflected succession? Examples?

Answer 34

When succession is **stopped or interfered** with causing stable community to be different to climax community - PLAGIOCLIMAX COMMUNITY **Lawn mowing** —> if left alone, field would develop into shrubs/tres due to succession , but mowing prevents this (only grasses survive by regular mowing) **Grazing**- succession halted by grazing of livestock , as they eat new plant shoots trying to grow **Heather moorland** - climax community prevents from developing —> PLAGIOCLIMAX - heather is a shrub

Question 35

Why is preventing an area from reaching its climax community /managing succession sometimes a good thing?

Answer 35

- ecosystems at immediate stages of succession (small plants, grasses and shrubs present) have **DISTINCT DIVERSITY**, which wouldn’t exist if climax community is reached —> these plants can be of CONSERVATION IMPORTANCE - diverse plant species **provide food/habitat** for a **high diversity of animal species** —> some animals may be of CONSERVATION IMPORTANCE ( bc endangered/rare or have functions in ecosystem)

Question 36

Ways succession can be prevented for conservation purposes?

Answer 36

**Grazing animals** can be introduced temporarily - at growing shoots of shrubs and trees **Managed burning** - controlled fires lit/burn away shrubs and trees

Question 37

What is random and systematic sampling?

Answer 37

**Random**: positions of sample points completely random/due to chance **Systematic**: positions of sample points chose by the person carrying out the sampling —> SAMPLE BIAS MAY BE INTRODUCED

Question 38

Method to find **dry mass** and **energy value** of plant biomass?

Answer 38

Dry mass : **Weigh crucible** (heat proof container) without sample Place sample in **crucible/put in oven at low temp** - dont let it burn otherwise lose biomass **Remove/weigh crucible** at regular intervals during drying process Once mass of crucible **stops decreasing /becomes constant** —> sample is fully dehydrated **Subtract original mass of the crucible from the constant mass** to find dry mass of sample Find energy released by sample of plant biomass: Use calorimeter - **burn dried sample** and used energy released to heat known vol of water - measure change in temp of water - use to estimate the chemical energy stored within sample (JOULES or KILOJOULES )

Question 39

Nitrogen cycle? And which bacteria involved at each stage?

Answer 39

1. Nitrogen fixation - RHIZOBIUM/AZOTOBACTER 2. Ammonification - nitrogenous compounds from dead organisms (plants,animals,faeces) converted into AMMONIA by decomposers —> AMMONIUM IONS (NH4+) 3. Nitrification - NITROSOMONAS /NITROBACTER 4. Dentrification - dentifyung bacteria

Question 40

What are point quadrant?

Answer 40

Horizontal bar on 2 legs with series of holes along its length - placed at random points in sample area - pines dropped through holes in frame/every plant pin touches is recorded No. Individuals of each species recorded in each quadrat / % cover calculated by no. Times pin has touches a species as percentage of total no. Pin has dropped (GOOD FOR USE IN DENSE VEGETATION)

Question 41

What is ammonification?

Answer 41

Process converts organic nitrogen containing compounds in dead organisms/waste into **NH3 or NH4+ ions** This process make NH3 and NH4+ available to plants by: Dead/excretion by living organisms **release nitrogen rich** organic substances Saprobionts **decompose these into NH4+** NH4+ **absorbed/assimilated** by plants

Question 42

What is secondary succession?

Answer 42

This occurs in areas where an **existing community has been removed**, leaving the soil intact but with **no plant or animal species**

Question 43

How can the increase in biomass over time in a plant, such as heather, be determined experimentally?

Answer 43

Measure change in dry mass over time

Question 44

Similarities between nitrogen and carbon cycle?

Answer 44

- decomposing microorganisms - microorganisms return CO2/N2 back into atmosphere - carbon/nitrogen transferred from producer —> consumer - release inorganic molecules - CO2/NH4+ - animals obtain elements by feeding - elements fixed to organic compounds - inorganic gases (CO2/N2)

Question 45

What **other factors** can release carbon back into atmosphere in **carbon cycle**?

Answer 45

**Weathering** - carbon in sedimentary rock released back into atmosphere by weathering **Volcanic activity:** tectonic plate movement lead to release of CO2 by volcanic eruption **Fossil fuels** - burning fuels release CO2

Question 46

Cases of CO2 fluctuations annually, seasonally, day to day?

Answer 46

Day to day : repiration - day and night - release CO2 Photosynthesis - only in day - removes CO2 Seasonal: winter, reduced daylight hours, and lower temps - REDUCE PHOTOSYNTHESIS RATES - high co2 level Annually: increase in greenhouse gases Deforestations removes photosynthetic organisms (plants) —-> higher level of co2 Global warming - reduces solubility of CO2 in oceans

Question 47

Examples of adaptations pioneer communities may have?

Answer 47

Allows them to modify abiotic factors/endure harsh environments - asexual reproduction - nitrogen fixation to enrich soil - Extreme condition tolerance - rapid germination