Edexcel Biology Unit 4 A Level
2024 Exam Questions and
Answers 100% Pass
Define Succession - Answer>>A sequence of changes in a
community
Over a period of time
Define Climax community - Answer>>Final stage
Stable
Describe the structures in a chloroplast involved in the light-
dependent reactions - Answer>>Thylakoids made of
membranes
Arranged as grana
Contain chlorophyll
Arranged as photosystems
Membranes contain ATPase
Electron carriers associated with thylakoid membranes
Advantages of growing crops in glasshouses with artificial light
instead of open fields - Answer>>Crops grown all year round
Plants photosynthesise 24 hours a day
Less physical damage due to weather and animals
Pest control easier
Control of temperature/water supply
Effects of carbon dioxide and methane on Earth's temperature -
Answer>>Greenhouse gases
Trap heat and infra red
Reflected from Earth's surface
Mean temperature of earth's surface increases
,Suggest how other animals are affected by a fall in another
population - Answer>>Fewer prey eaten by the population
Therefore prey increase in number
Less competition for food from the population
Predator of the population might decrease, eat other prey or
migrate
Define biotic factors - Answer>>Factors involving organisms
and living things
Define abiotic factors - Answer>>Factors that are physical,
chemical or non living
Species density quadrat experiment - Answer>>Several
readings
Use of random quadrat positions
Random number calculator
Known area of quadrat
Number of individuals in each quadrat counted
For mean density: total number of each species divided by total
area sampled
Examples of abiotic factors - Answer>>Light intensity,
temperature, pH
Examples of biotic factors - Answer>>Predators, food
availability, disease, competition
Explain gene mutation - Answer>>Change in DNA
A deletion/addition/duplication/substitution of bases
Enzyme used to amplify DNA - Answer>>Polymerase
, Process used to separate DNA fragments - Answer>>Gel
electrophoresis
DNA profiling - which is the suspect? - Answer>>1. All of the
bands in the sample must match
2. DNA profiling assumes every individual's DNA is unique
3. Apart from identical twins
4. DNA profiling analyses the introns/Short tandem repeats
5. Non-coding DNA is very variable
6. Large number of introns
7. Many combinations at each locus
Explain why DNA profiles are not absolutely conclusive -
Answer>>1. DNA profiling has several stages
2. Contamination can arise at any stage
3. Only a few sequences of DNA analysed
4. Possibility of two identical profiles from unrelated individuals
5. Identical twins may show same profile
Suggest how DNA profiling is useful when examining fossils -
Answer>>1. Comparison made between DNA from fossils and
other organs
2. Find genetic relationships/how closely related
3. Used in taxonomy/classification
4. Understand evolutionary lines
Describe the genetic material in HIV - Answer>>RNA
Linear nucleic acid
No plasmids
Describe the genetical material in TB - Answer>>DNA
Circular nucleic acid
Plasmids
2024 Exam Questions and
Answers 100% Pass
Define Succession - Answer>>A sequence of changes in a
community
Over a period of time
Define Climax community - Answer>>Final stage
Stable
Describe the structures in a chloroplast involved in the light-
dependent reactions - Answer>>Thylakoids made of
membranes
Arranged as grana
Contain chlorophyll
Arranged as photosystems
Membranes contain ATPase
Electron carriers associated with thylakoid membranes
Advantages of growing crops in glasshouses with artificial light
instead of open fields - Answer>>Crops grown all year round
Plants photosynthesise 24 hours a day
Less physical damage due to weather and animals
Pest control easier
Control of temperature/water supply
Effects of carbon dioxide and methane on Earth's temperature -
Answer>>Greenhouse gases
Trap heat and infra red
Reflected from Earth's surface
Mean temperature of earth's surface increases
,Suggest how other animals are affected by a fall in another
population - Answer>>Fewer prey eaten by the population
Therefore prey increase in number
Less competition for food from the population
Predator of the population might decrease, eat other prey or
migrate
Define biotic factors - Answer>>Factors involving organisms
and living things
Define abiotic factors - Answer>>Factors that are physical,
chemical or non living
Species density quadrat experiment - Answer>>Several
readings
Use of random quadrat positions
Random number calculator
Known area of quadrat
Number of individuals in each quadrat counted
For mean density: total number of each species divided by total
area sampled
Examples of abiotic factors - Answer>>Light intensity,
temperature, pH
Examples of biotic factors - Answer>>Predators, food
availability, disease, competition
Explain gene mutation - Answer>>Change in DNA
A deletion/addition/duplication/substitution of bases
Enzyme used to amplify DNA - Answer>>Polymerase
, Process used to separate DNA fragments - Answer>>Gel
electrophoresis
DNA profiling - which is the suspect? - Answer>>1. All of the
bands in the sample must match
2. DNA profiling assumes every individual's DNA is unique
3. Apart from identical twins
4. DNA profiling analyses the introns/Short tandem repeats
5. Non-coding DNA is very variable
6. Large number of introns
7. Many combinations at each locus
Explain why DNA profiles are not absolutely conclusive -
Answer>>1. DNA profiling has several stages
2. Contamination can arise at any stage
3. Only a few sequences of DNA analysed
4. Possibility of two identical profiles from unrelated individuals
5. Identical twins may show same profile
Suggest how DNA profiling is useful when examining fossils -
Answer>>1. Comparison made between DNA from fossils and
other organs
2. Find genetic relationships/how closely related
3. Used in taxonomy/classification
4. Understand evolutionary lines
Describe the genetic material in HIV - Answer>>RNA
Linear nucleic acid
No plasmids
Describe the genetical material in TB - Answer>>DNA
Circular nucleic acid
Plasmids
