Questions I Got Wrong P3

Question 1

Difference between population & community

Answer 1

Population is members of one species in given area while community is all populations of all different species

Question 2

Describe how reduced NADP is produced in the light-dependent reactions of photosynthesis. (4)

Answer 2

1. Light absorbed by chlorophyll and electrons emitted/excited / raised
   to higher energy level;
2. Electrons passed along/down ETC and then accepted by NADP;
3. Water is split / photolysis of water;
4. Electrons from water replace electrons in chlorophyll;
5. Protons/H+ from water reduce NADP/produce NADPH;

Question 3

Anaerobic respiration in animals produces lactate.
Explain how the production of lactate allows glycolysis to continue.
Use Figure 7 and your own knowledge.

Answer 3

1. Pyruvate accepts hydrogen from NADH (forming lactate);
2. NAD allows glycolysis to continue (by accepting hydrogen);

Question 4

Nitrogen is an essential element in all living organisms.
Describe how nitrogen in the organic compounds of dead organisms is made available to plants.
Include the role of microorganisms in this process.

Answer 4

1. Dead organisms broken down by decomposers/saprophytes;
2. Reference to extracellular digestion;
3. Nitrogen containing compounds converted to/release ammonium
   ions/ammonia / ammonification;
4. Ammonium ions/ammonia converted to nitrite by nitrifying bacteria;
5. Nitrite converted to nitrate by nitrifying bacteria;
6. Nitrate absorbed by active transport in roots;

Question 5

Describe how plants can use the nitrogen found in the substances they absorb from the soil to make useful organic compounds.
Give specific examples of organic compounds that contain nitrogen.

Answer 5

1. (Reduction of) nitrate to ammonia/ammonium ions;
2. Nitrogen as essential element in nucleotides/DNA/ATP;
3. Used to make amino acids which are used to make proteins;
4. Example of proteins: enzymes/cell membrane components
   /cytochromes;

Question 6

Describe what happens to the reduced NAD produced during Step 3 in aerobic respiration.

Answer 6

1 Enters mitochondrion / ETC;
2 (NADH is) oxidised to NAD;
3 (NADH is) used to produce ATP;
4 Hydrogen atoms split into H+ and electrons;
5 Passed onto next carrier/ FAD/oxygen;

Question 7

Explain why sex-linked conditions are more common in males than in females.

Answer 7

1 Males only have one X chromosome / males have X and Y
chromosomes and females have two X chromosomes / females have
XX;
2 Recessive allele on (non-homologous portion of) X chromosome
has no (equivalent) allele on (homologous portion) Y chromosome;
3 Recessive allele on the X chromosome is expressed / male needs
to inherit one recessive allele whereas female needs to inherit two;

Question 8

Suggest one reason why the actual percentage of carriers of CF is different from the value you calculated in question 04.5.

Answer 8

(Hardy-Weinberg assumes) no selective advantage/disadvantage / no
movement into/out of population;

Question 9

Explain how changes in levels of carbon dioxide and methane in the atmosphere can cause climate change

Answer 9

1 Carbon dioxide and methane are greenhouse gases;
2 Greenhouse gases absorb heat;
3 Heat is radiated back to Earth;
4 Increased levels of carbon dioxide and methane increase the
amount of heat absorbed and re-radiated;

Question 10

Humans have been selectively breeding crop plants for thousands of years.
Explain how selective breeding has reduced the ability of crop plants to adapt to climate change.

Answer 10

1 Some of the alleles (for less desirable characteristics) removed;
2 Variety of alleles/genetic diversity (in population) is reduced;
3 Fewer alleles (means) population is less able to adapt to change;

Question 11

Define the term gene pool

Answer 11

Complete set of alleles for a gene in a population

Question 12

How can you keep temperature constant in a photosynthesis experiment on light intensity

Answer 12

Tank of water between bottle & lamp

Question 13

Explain why changes in temperature affect the rate of photosynthesis

Answer 13

Temperature is a limiting factor as the light independent reactions are enzyme controlled

Or

Increasing temperature increases kinetic energy so more successful collisions increasing rate of reaction

Question 14

Why are logarithmic scales used on a graph

Answer 14

Because theres a large range of values

Question 15

What is an ecosystem?

Answer 15

Populations of different species and the non-living components / all
the (interacting) biotic and abiotic factors

Question 16

Explain the importance of ATP in photosynthesis and respiration.

Answer 16

1. (Reduces) GP to TP (in light-independent reaction);
2. So useful organic substances are produced;
3. Regenerates RuBP;
4. So (Calvin) cycle can continue;
5. Phosphorylates glucose (in glycolysis);
6. So glucose is more reactive OR to activate glucose OR because glucose is stable;

Question 17

Explain how techniques used in fish farming can increase the efficiency of energy
transfer to salmon.

Answer 17

1. Movement restricted so less energy used (in muscle contraction);
2. Feed controlled so salmon grow well OR Feed controlled so less
   food wasted;
3. Predators excluded so no loss to other organisms OR Predators
   excluded so energy not wasted escaping;
4. Pesticides used so no loss to other organisms OR antibiotics
   added to food so disease is prevented;

Question 18

Suggest why a genetic bottleneck could be a problem for the hen harrier.

Answer 18

(Genetic bottleneck involves) small population;
2. (Small population) reduces gene pool/variety of alleles/genetic
diversity;
3. Captive breeding programme will also produce population with low/reduced genetic diversity;
4. (In future) hen harrier population may not be able to adapt to changes in environment/ suitable example of a lack of adaptation,
eg not resistant to a particular disease / not resistant to changes in climate;

Question 19

Describe similarities and differences between secondary succession and primary
succession.

Answer 19

Similarities:
1. Changes to environment/becomes less hostile over time still occur;
2. Biodiversity increases;
3. Will still lead to climax community (although it might contain different species) (unless succession is prevented again);
Differences:
4. Area already has soil/seeds in soil (unlike in primary succession);
5. (So) pioneer/first species different;
6. Process is faster/plants or animals in nearby areas quicker to move in;

Question 20

Suggest two advantages of using a suspension of chloroplasts, rather than a green
plant in this investigation.

Answer 20

1. Easier to remove samples at specific times;
2. Easier/quicker to stop reactions;
3. More rapid absorption of (radioactive) carbon dioxide/light;
4. No need for complex extraction procedure to analyse products
   OR
   Products not used/produced in other cellular reactions;

Question 21

Predatory fish also live in the lake.
The fish:
* feed on zooplankton
* hunt by sight.
Some types of zooplankton show vertical migratory patterns (move to different depths) over a 24-hour period.
Suggest how the differences in behaviour of the zooplankton may have evolved.

Answer 21

1. Copepods + cladocerans show vertical migration or only rotifers do
   not;
2. Copepods + cladocerans find more food/algae near the surface;
3. Predatory fish hunt near surface during daylight as can see prey;
4. Mutation / genetic variation (produces new allele / characteristic);
5. Zooplankton at deeper depths (during daylight) more likely to survive / fewer eaten / have selective advantage;
6. (Survivors reproduce &) pass on (beneficial) alleles;
7. Increase in frequency of beneficial alleles over time / over many
   generations;

Question 22

Give one reason a plant can absorb a range of different wavelengths of light.

Answer 22

Contain a mixture of pigments which absorb different
wavelengths/colours;

Question 23

Explain what a sex-linked condition is.

Answer 23

1. A condition that occurs mainly in one sex / in males;
2. (Due to) gene/allele being on the X-chromosome
   or
   gene/allele on one of the sex chromosomes;

Question 24

All domesticated horses are the same species but there are different breeds.
Suggest how allopatric speciation in wild horses could result in a new species
of horse.

Answer 24

1. Geographical isolation;
2. (Variation due to) mutation;
3. Different selection pressures;
4. Organisms with favourable phenotypes more likely to survive and reproduce;
5. Change in allele frequency or pass on favourable allele(s);
6. Cannot (inter)breed to produce fertile offspring;

Question 25

Explain how the student could determine if 5 minutes in the water bath is a suitable time.

Answer 25

1. (Idea of) measure the temperature of contents of test tubes;
2. (Idea of) check if temperature inside tube equals temperature of water bath