Topic 5- Ecosystems + Photosynthesis and Climate Change + Evolution

Question 1

Define an ecostystem

Answer 1

• all of the organisms living in an area and all of the abiotic factors

Question 2

Define a community

Answer 2

• all of the different species that live in the same habitat and interact w/ eachother

Question 3

What is interspecific competition?

Answer 3

• when organisms of diff. species compete for the same resources (food/habitat)
• e.g if competing for same food, species will be smaller as their food source is more limted and they have less energy for growth + reproduction

Question 4

What is intraspecific competition and its affect on abundance?

Answer 4

• when organisms of the same species compete for the same resources
• when resources are plentiful, population increases but this means more organisms to compete for the resources
• resoruces eventually are limited and populations decrease as not enough for all the organisms
• smaller pop means less competition which is better for growth and reproduction= pop grows again

Question 5

What is the carrying capacity?

Answer 5

• max population size of a species that an ecosystem can support

Question 6

What is predation and its affect on abundance?

Answer 6

• WHEN AN ORGANISM KILLS AND EATS ANOTHER ORGANISM
• when prey no. increase, more food for predators = predator pop grows
• predator no. increases= more prey eaten and prey no. fall
• less food for predators and their pop decreases

Question 7

What is the difference between random and non random sampling?

Answer 7

1. random avoids bias and uses random number generators to generate coordinates for the sample
2. non random is used when there is a lot of variet in abiotic features/ distribution of species in a habitat (to be representative)
3. systematic sampling is noon random and uses fixed intervals to take sample

Question 8

What are the 5 abiotic factors to measure?

Answer 8

1. climate- temperature (thermometer), rainfall (rain gauge), humidity (hygrometer)
2. Oxygen availability- only in aquatic habitats to measure oxygen dissolved in water (use Oxygen sensor)
3. Light intensity- use a light sensor
4. pH and moisture content of soil- indicator liquid in soil mixed w/ water or pH monito/ measure mass of soil before and after dehydration
5. Topography- the shape and features of the earth’s surface (relief and how height of land changes)

Question 9

Describe primary succession.

Answer 9

1. species colonise new land surface by seeds and spores being blown by the wind to grow = first species called pioneer
2. abiotic conditions are harsh due to no soil to retain water/ only pioneer species can grow due to being specially adapted
   -e.g marram grass having deep roots to get water and can tolerate salty environment
3. pioneer species die and microorganisms decompose the humus = forms basic soil
4. conditions become less hostile as the soil can retain water and new organisms can grow/ their roots keep soil in place
   - these die and decompose to add more organic material= soil is deeper and richer in minerals
5. larger plants can grow whihc require more water and stored deep in soil
   - final species to colonise land forms climax commmunity
   ** some new species change the environment which makes it less suitable for the previous species

Question 10

Describe secodnary succession

Answer 10

1. happens on land that’s been cleared of all plants but soil remains (e.g forest fire
2. occurs in same way but at later stage due to soild already present (pioneer species are larger plants)

Question 11

Describe chloroplasts

Answer 11

1. double membrane bound and keeps reactants for photosynthesis close to reaction sites
2. thylakoids (fluid filled sacs) = large SA to allow as much light energy to be absorbed as possible/ stacked in grana
3. thylakoid memebrane= contains photosynthetic pigments and lots of ATP synthase molecules/ pigments are attached to proteins (photosystems)
4. 2 photosystems - PSI absorbs wavelenth 700nm and PSII absorbs wavelength 680nm
5. stroma surrounds thylakoids= contains enzymes, sugars and organic acids for LD stage

Question 12

Describe the Light Dependent reaction (non cyclic photophosphorylation).

Answer 12

1. light energy absorbed by PSII and excited electrons in the chlorophyll
   - e- moves to highger energy level
2. the electrons are replaced in PSII by e- from photolysis of water (light energy splits water into protons, electrons and oxygen)
3. the excited e- lose energy down e- transport chain and this energy is used to transport protons into thylakoids
   - this makes conc. of H+ higher in thylakoids than stroma (conc. gradient)
4. H+ moves down conc. gradient back into stroma via ATP synthase enzyme (chemiosmosis)
   - this moevemt combines ADP + Pi to form ATP
5. light energy is absorbed by PSI and excites e- to higher energy level
   - they are transferred to NADP along w/ a proton to form reduced NADP
6. produced ATP, reduced NADP and O₂

Question 13

What is the difference between cyclic and non cyclic photophosphorylation?

Answer 13

• cyclic only uses PI because e- from chlorophyll aren’t passed onto NADP but go back to PSI via electron carriers
• doesn’t produced reduce NADP or Oxygen, just a small amount of ATP

Question 14

Describe the Light Independent Reaction (Calvin Cycle).

Answer 14

1. CO2 enters the leave and diffuses into the stroma where it combines with 5C ribulose biphosphate (RuBP)
   - this is catalysed by RUBISCO enzyme
   - forms unstable 6C whihc splits into 2x 3C GP
2. ATP from light dependent reaction is hydrolysed to provide energy to form 2x 3C GALP from GP
   
   • requires protons from reduced NADP to reduce GP
   • GALP is used to make organic compounds like glucose and some continues in Calvin Cycle to regenerate RuBP
3. 5 out of 6 GALP molecules are used to regenerate RuBP and only 1 of 6 GALP used to make hexose sugars (glucose)
   
   • to regenerate RuBP you need remaining ATP
     
     • as 6C in glucose you need 6 turns of the Calvin cycle to produce one glucose molecule

Question 15

What can the Calvin cycle products be used to make?

Answer 15

• Carbohydrates= 2 GALP molecules can make simple sugars like glucose and then polysaccharides can be made by joining these sugars together
• Lipids= made using glycerol synthesised from GALP and fatty acids synthesised by GP
• Amino Acids= some made from GP
• Nucleic acids= ribose sugar in RNA made using GALP

Question 16

Describe the Hill Reaction Practical

Answer 16

• when NADP accepts an electon and a proton from hydrolysis of water, it is reduced and O2 is released = Hill Reaction
• the rate can be investigated by adding DCPIP to isolated chloroplasts (acts as an electon acceptor and gets reduced/ changing from blue to colourless)
  1. Cut spinach leaves and remove stalks/ grind using a mortar and pestle with chilled isolation solution
  2. filter using a funnel lines with muslin and transfer liquid into test tubes

Question 17

What does the isolation solution for the Hill Reaction contain?

Answer 17

• sucrose
• KCl
• phosphate buffer at pH7

Question 18

What is Net primary productivity? How is it calculated?

Answer 18

• the amount of energy available at the enxt trophic level
• Gross Primary Productivity (energy received- energy not taken in) - energy used in respiration

Question 19

How do you calculate how efficient energy transfer is?

Answer 19

(net productivity/ energy recieved) x 100

Question 20

How do you measure energy transfer? What is wrong with this method?

Answer 20

1. calculate amount of energy in each trophic level by measuring dry mass of organism (biomass) in a sample
2. multiply biomass from sample by size of total population (the whole area) to find total amount of energy in the organisms at that trophic level
3. find difference in energy to show energy transferred

** the consumers may have taken in energy from sources other than the producers measured (not accurate
- need to include all organisms at each trophic level

Question 21

What are the three types of evidence for climate change?

Answer 21

1. temperature records
   - records since 1850’s so gives reliable but short term record of global temperature change
2. dendrochronology
   - analysing tree rings to see how old tree is (one ring=1 year)
   - thickness of ring depends on climate (warmer= thicker as better conditions for growth)
   - they can take cores of tree trunks to see what climate was like at the time of the ring
3. Pollen in peat bogs
   - pollen is preserved in peat bogs due to acidity and the bogs accumulate in later
   - age of preserved pollen increases w/ depth
   - can identify what plant the pollen came from
   - scientists know what climates diff. plants grow in so if increase in pollen from plants that grow in warmer climates means climate was warm at the time

Question 22

What are the limitations of extrapolated greenhouse gas conc data? (4)

Answer 22

• don’t know how greenhouse gas emissions will change and which scenario is accurate
• don’t know exactly the affect of emissions on temperature
• change in atmospheric greenhous gas cdue to natural causes is not known
• don’t know what attempts will be made to manage atmospheric conc and how successful

Question 23

How does global warming affect plants and animals?

Answer 23

• increase in temperature increases rate of enzyme controlled reactions
• however if temperatures are too high, enzymes vibrate more and bonds break= denature and reaction stops
  Examples:
  1. higher temperature increase rate of photosynthesis due to increased enzyme activity= plants grow faster
  -blue-green algae will grow faster due to warmer water/ more algal blooms and they produce harmful toxins which are harmful to human health
  2. may be too high for organisms and metabolic reactions slow down = life cycle will be slower
  3. affect distribution of organisms as conditions aren’t ideal so migrate as to not die out
  - mosquitoes may migrate as too hot to places where they wouldn’t have been found before/ bring diseases

Question 24

What are other affects of climate change?

Answer 24

1. Changing Rainfall Patterns= some areas will get more rain and others will get less
   - affects development and life cycles of organisms
   - distribution of some species may change e.g deserts increase in size due to decrease in rainfall and species that aren’t adapted to live in deserts will die out/ migrate
2. Seasonal Cycles= change timings of seasons
   - again affects development and life cycles of organisms
   - some animals breed at the start of seasons

Question 25

How to calculate Q10 and what does it tell you about. the reaction?

Answer 25

• rate at higher temp/ rate at lower temp
• the factor at which rate increases for every 10ºc

Question 26

Whya are biofuels good?

Answer 26

• alternative fuels produced from biomass which is material that is or was living
• burnt to release energy which release CO2 but no net increase/ stops increase of atmospheric CO2
  - amount of CO2 released=CO2 taken in when it was growing
• often made from crops which can then be replanted after harvesting= sustainable

Question 27

What is reforestation and its benefits?

Answer 27

• the planting of new trees in existing forests that have been depleted
• more trees= more CO2 removed from atmosphere via photosynthesis
• carbon stored as plant tissues in trees so less CO2 contributing to global warming

Question 28

Who would agree/ disagree with biofuels

Answer 28

:)
- farmers would support this as some governments fund the farming of crops for biofuels
- drivers may support this as the price of biofuels is lower than oil-based fossil fuels
:(
- conservationists may oppose as forests have been cleared to grow crops for biofuels
- consumers may oppose as farmland used to grow crops for biofuels may cause food shortages
- oil companies would oppose

Question 29

Who would agree/disagree w/ wind turbines?

Answer 29

:)
- companies that make wind turbines was sales would increase
- environmentalists would agree as electricity generated without increase atmospheric CO2
:(
- local communities may think they ruin landscape
- bird conservationist oppose as birds are killed by flying into wind turbines

Question 30

Describe allopatric speciation

Answer 30

• geographically isolated populations experience different conditions and selection pressures
• different alleles are more advantageous in the different populations
• changes in allele frequency will cause differences in gene pools of the separated populations = diff. phenotypes
• will become genetically distinct and are reproductively isolated so diff. species= cannot produce fertile offspring

Question 31

What are the different ways reproductive isolation can occur?

Answer 31

• mechanical changes= changes in genetalia to prevent successful mating
• seasonal changes= individuals from same population develop different flowering/ mating seasons
• behavioural changes= group of individuals in a population develop courtship rituals that aren’t attractive to the main pop.

Question 32

What is sympatric isolation?

Answer 32

• when a population isn’t geographically isolated but becomes reproductively isolated
• due to random mutations w/in a pop. to cause behavioural, mechanical and seasonal changes
• can’t reproduce to form fertile offspring

Question 33

What is genomics?

Answer 33

• evidence for evolution that uses DNA tech to determine the base sequence of an organisms genome
• allows scientists to compare DNA between organisms
• evolution is caused by gradual changes to base sequence
• organisms that diverged away from each other more recently will have more similar DNA = less time has passed for changes in base sequence to occur

Question 34

What is proteomics?

Answer 34

• evidence for evolution that studies proteins (size/shape/primary structure)
• sequence of amino acids are coded by sequence of DNA bases in gene
• related organisms will have similar DNA sequence= similar primary stuctures of proteins
• organisms that have diverged more recently will have more similar proteins as less time has passed for changes to occur

Question 35

How do scientists validate evidence?

Answer 35

1. scientific journals= scientists publish articles to share ideas/theories/evidence etc.
   
   • allows other scientists to repeat experiments to see if same results w/ same method
   • if same= evidence collected is reliable
2. peer review= must occur before work is published
   
   • other scientists who work in that area review work to check valid + supports conclusion
   • make sure experiments are carried out to highest possible standard
3. conferences= meetings to discuss eachother’s work
   
   • scientists w/ important results are invited to present work + other scientists can ask questions
   • easy way for latest theories to be shared and discussed

Question 36

How many GALP moleceules are needed to make starch?

Answer 36

2

Question 37

Why is the GPP value lower than the light energy available to the ecosystem?

Answer 37

• not all of the light falls on the leaves
• some light is reflected from surface of leaf
• some of the light may be the wrong wavelength

Question 38

How do peat bog conditions prevent decomposition?

Answer 38

• waterlogged conditions means there’s reduced O2 so less aerobic respiration can take place for decomposers
• acidic conditions denature and inhibit enzymes so they can’t break down organic matter