6.3.1 - Ecosystems

Question 1

Define ‘Ecosystem’ ?

Answer 1

Ecosystem : A self-contained community and the non-living components ( abiotic/ biotic factors ) of an environment

Question 2

What are the different types of ecosystems and name examples ?

Answer 2

• Simple ( eg. Dessert )
• Complex ( eg. Forest )

Question 3

What are the different types of factors in an ecosystem ?

Answer 3

• Abiotic
• Biotic

Question 4

Define ‘Biotic factors’ ?

Answer 4

A living factor in an ecosystem that influences the populations within a community

Question 5

Name examples of biotic factors ?

Answer 5

• Predation
• Competition
• Cooperation between organisms
• Parasitism
• Disease
• Camouflage
• Mankind

Question 6

Define ‘Abiotic factors’ ?

Answer 6

A non-living factor in an ecosystem which affects the populations within a community

Question 7

Name examples of abiotic factors ?

Answer 7

• Availability of water
• Light
• Radiation
• Temperature
• Humidity
• pH
• Salinity
• Soil composition

Question 8

What is biomass ?

Answer 8

• The mass of living material of the organism/ tissue
• The chemical energy that is stored within the organism/ tissue

Question 9

What is dry biomass ?

Answer 9

The mass of the organism/ tissue after all the water has been removed

Question 10

How is dry mass calculated ?

Answer 10

• Mass per area ( If the dry mass of the grass from 1 m² of a field is found to be 0.2 kg, we can say that the grass has a dry mass (i.e. biomass) of 0.2 kg m⁻² )
• Mass per area over time ( If the average biomass of 1 m² of a grass field over the course of a year is found to be 0.15 kg m⁻², the biomass may be given as 0.15 kg m⁻² yr⁻¹ )

Question 11

Explain the role of calorimetry ?

Answer 11

Calorimetry can be used to estimate the chemical energy stored in dry biomass

Question 12

Explain how to use a colorimeter ?

Answer 12

• Calorimetry involves burning the sample of dry biomass in a calorimeter
• The burning sample heats a known volume of water
• The change in temperature of the water provides an estimate of the chemical energy the sample contains

Question 13

What are the limitations of using a colorimeter ?

Answer 13

• It can take a long time to fully dehydrate a plant sample to find its dry mass
• Precise equipment is needed which may not be available
• The more simple and basic the calorimeter, the less accurate the estimate will be

Question 14

What is the equation for the efficiency of biomass transfer ?

Answer 14

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

Question 15

What are the different tropic levels ?

Answer 15

• Producers
• Primary consumers
• Secondary consumers
• Tertiary consumers
• Apex predators

Question 16

What does a large portion of sunlight not made available for photosynthesising plants ?

Answer 16

• Light falls away from plants
• Light passes through leaves or is reflected away
• Light is a mixture of wavelengths, and only certain wavelengths stimulate photosynthesis

Question 17

Explain why only a small portion of plant biomass is transferred to primary consumers ?

Answer 17

• Not all the plant’s biomass is eaten by the primary consumer
• Not all the consumer’s biomass intake is digested ( eg. Cellulose )

Question 18

Explain why only a small amount of biomass is transferred feed between consumers ?

Answer 18

• Not all the animal is eaten ( eg. Bones )
• Not all the animal is digested ( eg. Teeth, bones )
• Excretion of metabolic waste products via urine / faeces
• Biomass is lost via aerobic respiration to generate ATP
• Used for movement and generating heat

Question 19

What is the equation for the net productivity of producers ?

Answer 19

NPP = GPP - R

• GPP = gross primary productivity
• R = respiratory losses

Question 20

What is the equation for the net productivity of consumers ?

Answer 20

N = I - (F + R)

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

Question 21

How can farmers/ humans manipulate biomass transfer in plants ?

Answer 21

• Providing artificial light in greenhouses on overcast days
• Optimising planting distances between crops
• Irrigation to maximise growth in dry weather
• Use of fertilisers
• Selective breeding for fast growth
• Use of fungicides/pesticides
• Fencing to exclude grazers
• Ploughing and herbicides to kill weeds

Question 22

How can farmers/ humans manipulate biomass transfer in animals ?

Answer 22

• Restricting movement and therefore energy used fro aerobic respiration
• Providing animals with higher energy food/ higher energy input
• Keeping animals indoors to reduce the energy transferred as heat
• Removing competition and predators ( growing animals indoors and providing them with what they require )

Question 23

What are the different microorganisms involved in the nitrogen cycle ?

Answer 23

• Saprobionts ( Aerobic/ anaerobic bacteria and fungi )
• Nitrogen-fixing bacteria
• Nitrifying bacteria
• Denitrifying bacteria
• Mycorrhizal bacteria

Question 24

Why is the nitrogen cycle so significant ?

Answer 24

• This prevents the accumulation of waste
• This ensures nutrients stored within dead/ decaying matter are recycled and made available to producers/ plants ( for growth/ synthesis of amino acids )

Question 25

Define ‘decomposition’ ?

Answer 25

Decomposition : The process in which nutrients in dead material and waste products are digested, producing carbon dioxide, water and inorganic ions

Question 26

What is the role of saprobionts ?

Answer 26

- Decompose waste and dead matter via extracellular digestion, making inorganic ions available to other organisms ( eg. NHv4+ and POv4^-3 ions for plants ) - Carry out ammonification

Question 27

Define ‘ammonification’ ?

Answer 27

The conversion of nitrogen compounds in waste and dead matter into ammonia/ ammonium ions

Question 28

What is the role of nitrogen-fixing bacteria in?

Answer 28

- IN ANAEROBIC CONDITIONS Rhizobium in roots and azotobacter bacteria in soil carry out nitrogen-fixation - They convert atmospheric nitrogen gas into NHv4+

Question 29

Name example of nitrogen-fixing bacteria ?

Answer 29

- Azotobacter bacteria - Rhizobium bacteria

Question 30

What is the role of nitrifying bacteria ?

Answer 30

- Nitrifying bacteria convert NHv4+ into NOv2- and then nitrates (NOv3- )/ that can be used by plants - Nitrosomas bacteria convert NHv4+ into nitrites (NOv2- ) - Nitrobacter bacteria then convert nitrites into nitrates

Question 31

Name examples of nitrifying bacteria ?

Answer 31

- Nitrosomas bacteria - Nitrobacter bacteria

Question 32

What is the role of denitrifying bacteria ?

Answer 32

- During ANAEROBIC CONDITIONS they carry out denitrification - They use nitrates during respiration and convert it into Nv2 gas

Question 33

Why do farmers keep soil aerated ?

Answer 33

- This prevents soil become water-logged and maintains aerobic conditions - Denitrifying bacteria work optimally in anaerobic conditions - This prevents denitrifying bacteria from respiring NOv3- ions ad converting them into Nv2 gas and releasing it back into the atmosphere - This makes NOv3- available for plants which can use the to produce ATP, nucleic acids and proteins fro grow

Question 34

What is the role of mycorrhizal fungi ?

Answer 34

- Increase surface area of root systems - This helps plants to absorb water and scarce mineral ions from soil

Question 35

Draw a diagram that shows the different stages of the nitrogen cycle ?

Answer 35

Question 36

Name the different forms in which carbon is stored ?

Answer 36

- In the atmosphere (as CO2) - In sedimentary rocks - In fossil fuels ( coal, oil, and gas ) - In vegetation (e.g. as cellulose) - Dissolved in the oceans (as CO2)

Question 37

Name the different processes involved in the carbon cycle ?

Answer 37

- Photosynthesis - Respiration - Feeding - Decay and decomposition - Burning Fossil Fuels - Sedimentation

Question 38

Explain the role of photosynthesis in the carbon cycle ?

Answer 38

- Autotrophs use energy from sunlight to fix ‘carbon dioxide’ during photosynthesis ( Calvin Cycle, COv2 is fixed by RuBisCO ) - This removes COv2 from the atmosphere

Question 39

Explain the role of respiration in the carbon cycle ?

Answer 39

- COv2 is released during aerobic respiration in the Link Reaction and the Krebs Cycle - COv2 is released during anaerobic respiration via fermentation by yeast and bacteria

Question 40

Explain the role of feeding in the carbon cycle ?

Answer 40

- Carbon forms nucleic acids/ proteins in animals and plants - Carbon/ biomass is transferred from autotroph to heterotroph during feeding

Question 41

Explain the role of decay and decomposition in the carbon cycle ?

Answer 41

- Saprobionts carry out decomposition/ break down organic macro molecules in living material - This releases carbon dioxide into the surroundings

Question 42

What is the role burning fossil fuels in the carbon cycle ?

Answer 42

- Burning of fossil fuels, releases COv2 back into the atmosphere - It is released at a faster rate than it can be absorbed by plants and aquatic producers

Question 43

What is the role of sedimentation in the carbon cycle ?

Answer 43

- Plants that die are not fully decomposed by saprobionts and their bodies form layers of sediment, locking carbon - This sediment is can form fossil fuels - Aquatic organisms that die also form sediments on the sea bed; form other fossil fuels like oil and gas

Question 44

What is succession ?

Answer 44

Succession : The change in an ecologic community over time

Question 45

What is primary succession ?

Answer 45

The process when newly formed/ exposed land is gradually colonised by an increasing number of pioneer species

Question 46

Explain the process by which primary succession occurs ?

Answer 46

- Seeds and spores that are carried by the wind land on the exposed rock and begin to grow (eg. lichens ) ; pioneer community - Pioneer species have special adaptations allow them to survive in extreme conditions ( eg. nitrogen-fixation ) - Pioneer species die and decompose forming basic soil/ hummus - Seeds of herb species ( grasses, shrubs and mosses ) land on this basic soil and begin to grow ; intermediate community - Die and decompose, increasing mineral ion, nitrate, depth and water content of soil - When soil is sufficiently deep, contains enough nutrients/ nitrates and can hold enough water it can support the growth of large trees ; dominant species - This results in the formation of a signal, stable complex community that EXPERIENCES LITTLE CHANGE OVER TIME ( is not prone to further succession )

Question 47

Define ‘pioneer species’ ?

Answer 47

Pioneer species : A species that can colonise bare rock or ground

Question 48

Features of plant species that make up pioneer community ?

Answer 48

- small species ( eg. Lichens, mosses, algae ) - shorter life-cycle / fast growing - Produce seeds or spores in large quantities - Can be dispersed long distances / germinate rapidly - Self-pollinating / asexual reproduction - Able to tolerate extreme conditions / environment

Question 49

Features of animal species that make up pioneer community ?

Answer 49

- Few species if any - Small species ( eg. Ants, beetles, snails )

Question 50

Features of plant species that make up climax community ?

Answer 50

- More species than pioneer community - Larger species ( eg. Conifers, maple, oak trees ) - Unable to tolerate extreme environments - Require soil with ample water and minerals - Dominant species - Slow growing

Question 51

Features of animal species that make up climax community ?

Answer 51

- Larger species ( eg. Squirrels, owls, deer ) - More herbivore species - Carnivore species present - Longer food chains

Question 52

Define ‘climax community’ ?

Answer 52

Climax community : The stable, final community that exists in a balanced equilibrium where the species composition / abiotic factors remains relatively constant over time AND IS NOT SUBJECT TO FURTHER SUCCESION

Question 53

Explain how the environment changes during succession ?

Answer 53

- Each new species changes the environments in a way that it becomes less it bale for the previous species - Therefore, each existing species is outcompeted by a new colonising species - This increases biodiversity

Question 54

Define ‘deflected succession’ ?

Answer 54

Deflected succession : The human activity by which the resulting stable community is different to the climax community that would not have occurred through natural succession

Question 55

Explain why succession may be managed for conservation ?

Answer 55

- This maintains earlier stages of succession and prevents final climax community being reached - This allows a greater variety of habitats to be considered and therefore a greater range of species to survive

Question 56

What methods are used to prevent succession ?

Answer 56

- Controlled grazing - Managed burning

Question 57

Explain how grazing animals prevent succession ?

Answer 57

- They eat the growing shoots of shrubs and trees - This stops these plants from establishing themselves and prevents succession

Question 58

Explain how managed burning helps prevent succession ?

Answer 58

- Controlled fires burn away/ destroy the shrubs and trees - Shrubs such as heather grow back - This prevents succession and final climax community from being reached

Question 59

Look at sampling flash cards in biodiversity module ( random, non-random, systematic , etc …. )

Answer 59

Yes

Question 60

What is the equation for mark-release-recapture method ?

Answer 60

Estimated population = ( size of first sample x size of second sample ) / number of recaptured marked individuals

Question 61

Explain how the mark-release-recapture method is carried out ?

Answer 61

- The first large sample is taken - Individuals are caught, counted and marked in a way that won’t affect their survival - The marked individuals are returned to their habitat and allowed to randomly mix with the rest of the population - When a sufficient amount of time has passed another large sample is captured - The number of marked and unmarked individuals within the sample are counted - The proportion of marked to unmarked individuals is used to calculate an estimate of the population size

Question 62

What are some assumptions made during the mark-release-recapture method ?

Answer 62

- The marked individuals are given sufficient time to disperse and mix back in fully with the main population - The marking doesn't affect the survival rates of the marked individuals - The marking remains visible throughout the sampling and doesn't rub off - The population stays the same size during the study period

Question 63

What is the ACFOR scale ?

Answer 63

ACFOR = Abundant, Common, Frequent, Occasional, Rare