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20 Cards in this Set
- Front
- Back
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What is meant by a hierarchy? |
- A series of groups within groups, with no overlap between groups |
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Explain the role of independent segregation in meiosis. |
- To provide genetic variation - (Allow) different combinations of maternal and paternal chromosomes/alleles - To produce haploid cells - Allows homologous chromosomes to arrange randomly |
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The cells within a mountain zebra contain 32 chromosomes. The cells within a donkey contain 62 chromosomes. Use this information to suggest why zeedonks are usually infertile. |
- Zeedonk has an uneven number of chromosomes - Chromosomes are not homologous and cannot pair - The chromosome number therefore cannot be halved so meiosis cannot occur, so sex cells cannot be created |
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What is selective breeding? |
- The breeding of organisms which contain desirable alleles in order to increase their frequency. |
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Explain one problem with selective breeding. |
- Inbreeding of closely related organisms can increase the probability of mutations being passed on through recessive alleles. - This increases the chance of recessive diseases - This also decreases the genetic diversity/size of the gene pool - This means that organisms are more susceptible to the same disease/reduces adaptability |
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The oxygen dissociation curve of haemoglobin shifts to the right during vigorous exercise. Explain the advantage of this shift. |
- Lower affinity for oxygen/releases oxygen more readily - To respiring cells - Rapid diffusion |
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Explain how having a round body shape helps an organism living in a cold environment. |
- Small SA:VOL - Reduces heat loss |
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Describe how the countercurrent flow system leads to more efficient gas exchange in fish. |
- Water and blood flow in opposite directions - maintains concentration gradient - Along length of gill/lamellae |
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Amoebic gill disease (AGD) is caused by a parasite that lives on the gills of some species of fish. The disease causes the lamellae to become thicker and to fuse together. AGD reduces the efficiency of gas exchange in fish. Give two reasons why. |
- Thicker lamellae = longer diffusion pathway - Lamellae fuse = Smaller surface area |
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The volume of water passing over the gills increases if the temperature of the water increases. Explain why. |
- Increased metabolism of enzymes - Less oxygen dissolved in water |
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The antibiotic tetracycline binds to ribosomes in bacterial cells.
Explain how this causes the death of the bacterial cells. |
- Prevents protein synthesis - Enzymes not produced, respiration is inhibited |
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Tetracycline can enter a bacterium through protein A. This protein is found in theplasma membrane. Suggest how a change in the amino acid sequence of this protein could make abacterium resistant to tetracycline. |
- Different tertiary structure - Tetracycline cannot bind and cannot enter cell |
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Evolutionary relationships between different primates can be found by comparing their proteins and DNA. All primates produce a species-specific type of haemoglobin. An antibody against human haemoglobin could be used to compare the evolutionary relationships between different primates. Describe and explain how. |
- Antibody and haemoglobin are mixed - Precipitate band is formed - More precipitate = more similarity |
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Which two measurements are needed to calculate an index of diversity? |
- Number of individuals of each species - Total number of individuals |
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Explain how the structure of DNA is related to its functions |
- Sugar phosphate backbone provides strength - Large so can store lots of information - Helix is coiled so is compact - Double stranded so replication can be semiconservative - Weak hydrogen bonds so easy to unzip - Many hydrogen bonds so strong |
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Explain how double-blind trials make results more reliable. |
- Scientists can't show bias - Volunteers can't show placebo expectations |
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DNA Helicase is important in DNA replication. Explain why. |
- Separates/unzips DNA - So nucleotides can attach |
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Give one way which an antibiotic can prevent the growth of bacteria. |
- Prevent cell wall formation - Cause cell lysis |
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Explain the advantage of foetal haemoglobin. |
- higher affinity for Oxygen than mother haemoglobin. - Takes oxygen from it - To supply oxygen to foetus |
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Abdominal pumping increases the efficiency of gas exchange between the tracheolesand muscle tissue of the insect. Explain why.
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- More oxygen enters tracheae - Which maintains a greater diffusion gradient |
