AS Level Biology A H020/02 Depth in
biology Tuesday 6 June 2027 -
Afternoon
Alveoli are located in the lungs of mammals. Explain how alveoli are adapted for efficient gas
exchange. - ANS-Thin walls: Squamous epithelium- flat for a short diffusion pathway
good blood supply- creates steep concentration gradient
Elastic fibers- stretch and recoil- maintain concentration gradient
Large surface- large numbers of alveoli
\Another stage of meiosis is metaphase 1.
Explain how the organization of homologous chromosomes during metaphase 1 increases
genetic variation - ANS-independent assortment
chromosomes line up at the Centre of the equator
each chromosome of the homologous pair is genetically different
\Based only on your observations of Fig.1.2, state two reasons for your answer in (b)(i) -
ANS-chromosomes condense
chromosomes still not aligned at the equator
\Bony fish and insects have different gas exchange systems. Both can be observed by
dissection.
(a) Describe how you would carry out the dissection to display maximum detail of either gas
exchange system. - ANS-cut open the exoskeleton
\Cell B in Fig. 1.1 was observed using an electron microscope. Give one piece of evidence from
Fig. 1.1 that supports this - ANS-organelles can be seen in more detail
\Describe how the trachea of a mammal is different from the trachea shown in Fig 3 -
ANS-Mammals have just one trachea
Insects have multiple
Mammal trachea is longer
Insects trachea shorter
Mammal trachea larger diameter
insects smaller diameter
\Give one way that an image produced by a laser scanning confocal microscope differs from
that produced by an electron microscope - ANS-laser scanning confocal microscope has lower
resolution
\glucose is an important biological molecule required by cells for cellular respiration. State the
physical property of glucose that allows it to be easily transported in the bloodstream -
ANS-glucose is soluble
biology Tuesday 6 June 2027 -
Afternoon
Alveoli are located in the lungs of mammals. Explain how alveoli are adapted for efficient gas
exchange. - ANS-Thin walls: Squamous epithelium- flat for a short diffusion pathway
good blood supply- creates steep concentration gradient
Elastic fibers- stretch and recoil- maintain concentration gradient
Large surface- large numbers of alveoli
\Another stage of meiosis is metaphase 1.
Explain how the organization of homologous chromosomes during metaphase 1 increases
genetic variation - ANS-independent assortment
chromosomes line up at the Centre of the equator
each chromosome of the homologous pair is genetically different
\Based only on your observations of Fig.1.2, state two reasons for your answer in (b)(i) -
ANS-chromosomes condense
chromosomes still not aligned at the equator
\Bony fish and insects have different gas exchange systems. Both can be observed by
dissection.
(a) Describe how you would carry out the dissection to display maximum detail of either gas
exchange system. - ANS-cut open the exoskeleton
\Cell B in Fig. 1.1 was observed using an electron microscope. Give one piece of evidence from
Fig. 1.1 that supports this - ANS-organelles can be seen in more detail
\Describe how the trachea of a mammal is different from the trachea shown in Fig 3 -
ANS-Mammals have just one trachea
Insects have multiple
Mammal trachea is longer
Insects trachea shorter
Mammal trachea larger diameter
insects smaller diameter
\Give one way that an image produced by a laser scanning confocal microscope differs from
that produced by an electron microscope - ANS-laser scanning confocal microscope has lower
resolution
\glucose is an important biological molecule required by cells for cellular respiration. State the
physical property of glucose that allows it to be easily transported in the bloodstream -
ANS-glucose is soluble
