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Biology IGCSE > Things I Need To Know > Flashcards

Things I Need To Know Flashcards

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1
Q

State what is meant by the term codominant alleles? (2 marks)

A

Both alleles are equal and expressed

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2
Q

State what is meant by the term codominance? (1 mark)

A

Both characteristics are expressed

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3
Q

Describe how a protein is made in a cell (5 marks)

A
  • 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
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4
Q

State what is meant by the term habitat

A

A place where organisms live

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5
Q

State what is meant by the term population

A

All of the organisms of one species in a habitat

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6
Q

State what is meant by the term community

A

All of the different species in a habitat

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7
Q

State what is meant by the term ecosystem

A

All of the organisms living in a particular area and all the non-living conditions

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8
Q

How do fish farmers maximise their yields (6 marks)

A
  • 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
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9
Q

What is the role of FSH and what is its source? (3 marks)

A
  • Pituitary gland
  • Stimulates follicle growth
  • Stimulates oestrogen secretion
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10
Q

What is the role of LH and what is its source? (3 marks)

A
  • Pituitary gland
  • Stimulates ovulation
  • Stimulates release of progesterone / testosterone
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11
Q

What is the role of oestrogen and what is its source? (3 marks)

A
  • Ovaries
  • Repairs the lining of the uterus
  • Stimulates LH secretion
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12
Q

What is the role of Progesterone and what is its source? (3 marks)

A
  • Ovaries
  • Maintains the lining of the uterus
  • Inhibits LH
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13
Q

How could you determine the rate of water loss from a leafy shoot? (4 marks)

A
  • 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
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14
Q

What are stem cells?

A
  • 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
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15
Q

Where are stem cells found?

A
  • 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
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16
Q

Why are some people against stem cell research?

A
  • 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
17
Q

Suggest why the predicted ratio from a punnet square has not been obtained (4 marks)

A
  • Small sample size
  • There is a random chance of fertilization
  • Mutations may have occurred
18
Q

Describe the role of insulin in the body (3 marks)

A
  • Converts blood glucose…
  • Into glycogen….
  • Stored in muscles / liver
19
Q

Describe how bacteria are genetically modified to produce human insulin? (3 marks)

A
  • 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
20
Q

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)

A
  • 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
21
Q

How do vaccinations protect humans from pathogens? (3 marks)

A
  • 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
22
Q

Why may a change in DNA not affect the phenotype of an organism? (4 marks)

A
  • 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
23
Q

What are the pros and cons of cloning a pet

A

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

24
Q

How does a saprotrophic fungus obtain its food? (3 marks)

A

o Releases digestive enzymes
o Onto dead or decaying organisms
o Absorbs the digested food and nutrients

25
Q

Why could high blood pressure cause protein to be present in urine? (2 marks)

A

o Protein is a large molecule
o High pressure forces protein molecules
o Out of the glomerulus

26
Q

Describe the role of bacteria in the nitrogen cycle (5 marks)

A
  • 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
27
Q

Describe an experiment to measure the energy content of food (6 marks)

A
  • 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

Biology IGCSE (1 decks)

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