Things I Need To Know Flashcards
State what is meant by the term codominant alleles? (2 marks)
Both alleles are equal and expressed
State what is meant by the term codominance? (1 mark)
Both characteristics are expressed
Describe how a protein is made in a cell (5 marks)
- Transcription occurs
- The mRNA leaves the nucleus
- The mRNA enters the cytoplasm
- Translation occurs in the ribosomes
- tRNA brings the specific amino acid
- Related to the codon / anticodon
- An amino acid chain is built which is specific to a protein
State what is meant by the term habitat
A place where organisms live
State what is meant by the term population
All of the organisms of one species in a habitat
State what is meant by the term community
All of the different species in a habitat
State what is meant by the term ecosystem
All of the organisms living in a particular area and all the non-living conditions
How do fish farmers maximise their yields (6 marks)
- Use selective breeding to produce faster growing fish
- Separate sizes, ages, sexes to stop intraspecific predation
- Use cages / nets / covers to prevent interspecific predation
- Feed small amounts of food regularly which is rich in protein to enable growth
- Remove uneaten food and faeces through changing water regularly and filtering
- Use antibiotics / vaccinations to prevent disease
- Oxygenate the water
- Monitor pH, oxygen levels and temperature for optimum setting
What is the role of FSH and what is its source? (3 marks)
- Pituitary gland
- Stimulates follicle growth
- Stimulates oestrogen secretion
What is the role of LH and what is its source? (3 marks)
- Pituitary gland
- Stimulates ovulation
- Stimulates release of progesterone / testosterone
What is the role of oestrogen and what is its source? (3 marks)
- Ovaries
- Repairs the lining of the uterus
- Stimulates LH secretion
What is the role of Progesterone and what is its source? (3 marks)
- Ovaries
- Maintains the lining of the uterus
- Inhibits LH
How could you determine the rate of water loss from a leafy shoot? (4 marks)
- Use a potometer
- Cut the shoot underwater at a slant to maximise surface area and prevent air from entering the xylem
- Check the apparatus is airtight and watertight
- Introduce an air bubble
- Measure the distance moved by the bubble multiply by cross sectional area to calculate volume
- In a stated period of time
- Repeat to calculate the mean rate
- Control light, temperature and air humidity
What are stem cells?
- Stem cells are undifferentiated cells which can divide and produce lots more undifferentiated cells
- These cells can then be turned into specific types of cells depending on the instructions given to them
Where are stem cells found?
- Stem cells are found in early human embryos and can make all of the different cells found in the human body
- They are also found in adults in the bone marrow. However adult stem cells cannot be turned into any type of cell
Why are some people against stem cell research?
- Some people believe human embryos shouldn’t be used for experiments as each one is a human life
- Other people believe curing a person who is suffering is more important than the rights of an embryo
- Embryos used in research are often unwanted ones from fertility clinics which would have been destroyed
- Campaigners against embryo research believe scientists should concentrate on finding alternative sources of stem cells
Suggest why the predicted ratio from a punnet square has not been obtained (4 marks)
- Small sample size
- There is a random chance of fertilization
- Mutations may have occurred
Describe the role of insulin in the body (3 marks)
- Converts blood glucose…
- Into glycogen….
- Stored in muscles / liver
Describe how bacteria are genetically modified to produce human insulin? (3 marks)
- Take DNA from gene in the pancreas
- Cut with the restriction enzyme
- The DNA from the vector e.g. a plasmid is then cut with the restriction enzyme
- The DNA from the pancreas gene is then joined with the plasmid DNA with ligase
Humans are at risk from infectious diseases, describe the different pathogens. Refer to a disease that each pathogen can cause in your answer (6 marks)
- Virus, a non living organism – AIDS
- Bacteria, microscopic single celled – Pneumonia
- Fungus, not able to carry out photosynthesis – Atheletes foot
- Protoctist, microscopic single celled – Malaria
How do vaccinations protect humans from pathogens? (3 marks)
- Dead or weakened pathogen injected into human
- This causes the lymphocytes to produce antigens and memory cells
- In the event that this pathogen comes back the secondary immune response is much faster to produce antibodies
Why may a change in DNA not affect the phenotype of an organism? (4 marks)
- As some triplets code for the same amino acid
- No change in the protein produced
- Active site hasn’t changed
- The mutation may be recessive so not expressed
- Mutation may occur in a non-coding sequence of DNA
What are the pros and cons of cloning a pet
o Can produce genetically identical offspring
o May have similar appearance
o Can be cloned before death
* Cons of cloning
o Expensive
o Many trials result in clone dying
o Shorter life span
o Reduces variation within a breed
How does a saprotrophic fungus obtain its food? (3 marks)
o Releases digestive enzymes
o Onto dead or decaying organisms
o Absorbs the digested food and nutrients
Why could high blood pressure cause protein to be present in urine? (2 marks)
o Protein is a large molecule
o High pressure forces protein molecules
o Out of the glomerulus
Describe the role of bacteria in the nitrogen cycle (5 marks)
- Decomposers break down protein and urea and turn it into Ammonia, a compound containing nitrogen
- Nitrogen fixing bacteria turn nitrogen gas into ammonia
- Nitrifying bacteria turn ammonia to nitrites
- Denitrifying bacteria turn nitrates into Nitrogen gas
Describe an experiment to measure the energy content of food (6 marks)
- Weigh a small amount of food using a mass balance
- Put a known mass of water in a boiling tube
- Measure the temperature of the water
- Set the food alight and put it under the boiling tube to heat the water
- Keep relighting the food until it wont catch fire anymore and the food has completely burned
- Record the final temperature of the water after being heated
- Repeat three times to get a reliable result and a mean
- Energy Content = 4.2 x Mass of Water x Temperature Rise / Mass of food
- Control – Same distance burning food from the boiling tube,
- Improvements – Insulation for boiling tube
