JAN 10 Flashcards
This system of classification consists of a hierarchy. Explain what is meant by a hierarchy (2 marks)
- Groups with groups
2. No overlaps
Explain how a change in a sequence of DNA bases could result in a non-functional enzyme (3 marks)
- Change in sequence of Amino acids/ primary structure
- Change in hydrogen bonds
- Changes the tertiary structure/ shape of active site
- Substrate cannot bind to the active site/ no enzyme-substrate complexes formed
In 2002, very few gladiators were available for identification. Scientists around the world used photographs to establish the relationship of gladiators to other insects. Explain how. (1 mark)
- Compare similar physical features
An increase in respiration in tissues of a mammal affects the oxygen dissociation curve of haemoglobin. Describe and explain how. (2 marks)
- Increase in carbon dioxide as respiration increases
2. Curve moves to the right
There is less oxygen at high altitudes than at sea level.
People living at high altitudes have more red blood cells than people living at sea level. Explain the advantage of this to people living at high altitudes. (2 marks)
- More haemoglobin
2. So will load more oxygen
Explain the advantage to people living at high altitudes of having the oxygen dissociation curve shown in the graph - to the right - (2 marks)
- Lower affinity for oxygen
2. More oxygen released to respiring tissues
Explain why it was important that the piece of the epidermis the student removed was thin (2 marks)
- Only a single layer of cells
2. Light can pass through
Suggest how the student could have used his slide to find the number of stomata per cm^2 (3 marks)
- Method of determining area of field of view
- Count number of stomata in field of view
- Repeats and calculation of mean
The stomata on the leaves of the pine trees are found in pits below the leaf surface. Explain how this helps to reduce water loss. (2 marks)
- Water vapour accumulates
2. Water potential gradient reduces
The blood pressure is high at the start of the capillary. Explain how the left ventricle causes blood to be at high pressure. (1 mark)
- Has a thick muscular wall so when it contracts ir produces high pressure
The blood pressure decreases along the length of the capillary. What causes this decrease in pressure. (1 mark)
- Loss of fluid volume
or - Restriction/ Friction of the capillary wall
In children, some diets may result in low concentration of protein in fluid F. This can cause the accumulation of tissue fluid. Explain the link between a low concentration of protein in fluid F and the accumulation of tissue fluid. (3 marks)
- Water potential gradient in capillary not as low
- More tissue fluid at arteriole end of the capillary
- No water absorbed into the blood capillary
- By osmosis
Explain why it may be more useful to calculate the index of diversity than to record only the number of species present (2 marks)
- Index of diversity measures the number of species and the number of individuals of each species.
- Some species may be present in low numbers
The demand for increased food production had led to areas of heath being used to grow wheat. Explain this effect on:
i) the species diversity of plants (2 marks)
ii) the species diversity of animals (2 marks)
i) 1. Reduced as only one species is being grown
2. Use of herbicides
3. Wheat is a better competitor for light
ii) 1. Fewer variety of food sources
2. Fewer habitats for the animals
3. Reduced by pesticides used
Gas exchange in fish takes place in gills. Explain how two features of fills allow efficient gas exchange. (2 marks)
- Thin epithelium so short diffusion pathway
- Countercurrent flow maintains a diffusion gradient
- Lamellae provide large surface area
