Bio Flashcards
Give reasons why the total biomass is less. (3)
- not all the animals are
eaten - not all parts of eaten
- due to respiration
Suggest reasons why the scientists could not find the exact number of organisms. (3)
- too many to count
- animals hiding
- count more than once
Plant cell:
* after one hour in distilled water
* after one hour in strong sugar solution
Explain what has happened to the plant cell after an hour in each liquid and why. (6)
- hypotonic
- water has entered the cell by osmosis
- from dilute to more
concentrated solution - via partially permeable
membrane the cell is turgid. - hypertonic
- water left the cells by osmosis
- from dilute to more
concentrated solution - via partially permeable
membrane - so cell membrane shrank
away from cell wall the cell is plasmolysed.
Explain how the human body reduces the volume of urine produced when less water is consumed. (4)
- too little water in the blood
- hypothalamus detects this
- release of ADH by pituitary
- increased reabsorption of
water
On a dry day, an athlete can run a marathon in 2 hours 15 minutes, while in humid conditions, if the temperature exceeds 18°C, the body overheats. Suggest an explanation for the athlete overheating in humid conditions. (3)
- sweat released
- cannot evaporate because of high humidity
- so less heat lost
Shivering helps to stop the core body temperature falling too quickly. Explain how. (2)
- muscles contract
- respiration releases more heat
Explain how Jean-Baptiste Lamarck (1744–1829) accounted for the evolution of the long neck in giraffes. (3)
- stretching led to more use of neck
- characteristic acquired during lifetime
- this characteristic was passed to offspring
Explain how Charles Darwin (1809–1882) accounted for the evolution of the long
neck in giraffes. (4)
- mutation occurred
- there is survival of fittest
- advantaged individuals breed more
- the genes passed on
Suggest why nearly every organism on earth has an even number of chromosomes in its body cells. (1)
- chromosomes in pairs
Many people think that the stem cells for treating human conditions should be obtained from umbilical cords rather than human embryos. Suggest one reason why. (1)
- damage to embryo
Explain how the carbon contained in dead organisms can be made available to plants. (3)
- decomposition by bacteria
- releasing carbon dioxide
- taken up by the plant during photosynthesis
Suggest why it is advisable for people to be vaccinated against influenza every year. (3)
- virus mutates
- with different antigens
- memory cells no longer recognise virus
The protein coat of the influenza virus, a protective layer, is a key component in the production of the influenza vaccine. Explain how the influenza vaccine produces immunity in the body. (3)
- protein coat carries antigens
- stimulates white blood cells or production of antibodies
- production of memory cells
