Summer 2016 selection (a)

Explanation/disclaimer: click to expand/contract

Conclusion from scatter diagram

Many results lie a long way off the line of best fish

Explanation of increase in number of water beetles due to presence of fish in lake

There is a greater selective pressure, so beetles are forced to adapt. Therefore there are more species.

Fish produce an acidic environment as they release CO2 during respiration

Presence of predators increases the birth rate of the population as more offspring are needed to survive to reproduce

Suggestion of function of hydrogen sulfide in bacterial alternative form of photosynthesis

Hydrogen sulfide .. breaks down to form glucose

..can be split into glucose, sulfur and water

Bacteria use the hydrogen sulfide to create ammonium-containing compounds

Explanations of evolution in giraffes

Different habitats are different colours

The advantageous alleles survive and reproduce

As more survived and reproduced the allele for mutation was passed on

Different skin colours and markings would then prevent reunited populations from interbreeding

Humans may have built a road separating these giraffes into different groups

Giraffes had different markings showing who they could mate with

Use of mitochondrial DNA (mDNA) to demonstate different species

Mitochondrial DNA is inherited only by the mother

mDNA of 6 subspecies was so different that the different subspecies DNA would not survive with the other's mitochondrial DNA

mDNA of same species would be the same length ..have same number of chromosomes

They may have had different numbers of chromosomes in different species


- contained different amino acids

- contains info used to make gametes

- contains aerobic enzymes

- was taken from the egg of female

- could be incorporated into surrogate giraffe

ATP made in the mitochondria might have been different in the 6 subspecies

They separated the DNA into its separate amino acids

This would have resulted in respiratory problems for offspring

Only the strongest alleles of genes would be passed on

This would allow comparison of rates of respiration

Better camouflaged giraffes have less mitochondria - others would need to run from predators

They compared how much ATP each subspecies produced

Because DNA codes for organisms ,,,

The different amino acid sequence in the DNA of the six determine that these species are more different from each other

How micro-organisms processing household waste contribute to the increase in temperature

When decomposing waste, microbes will have been respiring and hence generating heat from muscles used in respiration

Advantages of showing data using standard deviation rather than ranges

Ranges uses extreme values which does not include the majority of the data

SD is not affected by extreme values

Evidence for succession

Gram positive rods started low and increased as time went on

Explanation of respiratory quotient results

Seeds who are respiring need more oxygen to be able to respire

This suggests respiration was higher than intake of oxygen

Why aerobic respiration produces more ATP than anaerobic respiration

Oxygen is used to move large amounts of H+ ions through ATP synthase

Aerobic respiration involves a longer process e.g. the Calvin cycle and so it needs more ATP to keep the process continuing

Anaerobic respiration is used over a shorter time so uses glucose less well e.g. exploits it less

In anaerobic respiration the Kelvyn cycle can't occur

Aerobic respiration uses the CO2 to form more energy

In anaerobic respiration the organism has to have the energy in the first place to form the ATP

Krebs cycle happens twice - glycolysis only happens once

In aerobic respiration, phosphorylated oxidation takes place

Avoiding bias?

Place a transect square at the co-ordinates

Generate co-ordinates from random computer generator

Explanation of differences in algal species at 2 points on seashore

More light may cause algae to lose water via their stomata

If it is humid there is less oxygen in the air

Site may differ in pH concentration

Algae needed a lower temperature so less energy was wasted in maintaining it

The closer to the sea the more salt in the soil

More light means it is more likely to photosynthesise

Algae on the upper shore may photosynthesise more easily due to lack of water to refract light

How scientists determined the loss of mass of algae due to respiration

In the lab everything is equal

They mave have kept a measure of the oxygen released into the tank

Measure the mass of alga before and after evaporating it. This would show the loss of water due to respiration as water is produced by respiration.

If the liquid in the tube moved to the right that would show that carbon dioxide is being produced

- By testing the acidity in the tank before and after the experiment

- Using gas syringe

- Respirometer

- Counting bubbles

- By measuring temp change

- Place in tank of KOH solution

- Measure amount of ethanol produced

The difference would be the amount of algae that was eaten and therefore not respiring

Conclusions to data about amounts of algal species being consumed by sea slug and shore crab - using prbability values

Each alga ate both the sea slug and the shore crab

The significant value was less than 0.01 suggesting they were 99% confident

The final alga had p < 0.05 so it was significantly eaten

One alga had a critical value that left 1% to chance

Two algae are in the acceptable range for probability of error

There is a greater than 5% chance that these resuls are down to probability

0.05 is a very small number so the results are accurate

Light-dependent reaction explained

Photons of light strike the chlorophyll in the chloroplasts and this causes the excitement of the electron

Electrons are excepted by an electron carrier

Water is hydrated to produce oxygen

Light energy also causes the phosphorylation of water

As the H+ ions try to create balance they move through ATP synthase

ATP synthase adds an independent phosphate to ADP

Light difffuses into the cell via the stomata and into the thylakoids

Light has electrons present that contribute to making OH- and H+

These e- are transported in electron carriers to higher levels so e- has more energy

Light enters the chloroplast via the stomata

Energy released from falling elecrons is used to reduce NADP

Advantages and disadvantages of chemical pesticides

Nitrate pesticides cannot be used in organic farming

Pesticides are not as specific so they kill other pests

Its not specific so it kills both good pests that help the growth of plants as well as the bad pests

They will kill the whole pestilential population

If rainfall occurs then the chemical agents can lead to bioaccumulation

Pesticides are insoluble in water so they can leach into water sources

How soil microorganisms produce nitrates from remains of crop plants

Saprobionts produce nitrates from the remains of the soil

Proteins contain nitrogen as they have nitrogenous bases adenine thymine guanine and cytosine

Ploughing adds oxygenated nitrogen gas to the soil

The microbes use the ammonia and breathe out the nitrogen

These nitrate ions are broken down by saprobionts

Saprobiotic organisms break down the crop plant remains to their original compounds

Nitrogen fixation is when nitrogen gas in the atmosphere is broken down to ammonia

Urea, amino acids and proteins are ammonia containing compounds

Nitrofine organisms convert ammonia into nitrates    Home     Contents     Contact via form     Contact via email     Howlers     Books     WWWlinks     Terms of use     Privacy