AS Level Biology A H020/02 Depth in biology
Cell B in Fig. 1.1 was observed using an electron microscope. Give one piece of
evidence from Fig. 1.1 that supports this -correct answer*organelles can be seen in
more detail Give one way that an image produced by a laser scanning confocal
microscope differs from that produced by an electron microscope -correct
answer*laser scanning confocal microscope has lower resolution Meiosis is a type of
nuclear division. Fig. 1.2 shows a photomicrograph of plant cells undergoing meiosis
identify the stage of meiosis 1 shown in the cell labelled A -correct answer*prophase
(1) Based only on your observations of Fig.1.2, state two reasons for your answer in
(b)(i) -correct answer*chromosomes condense chromosomes still not aligned at the
equator Another stage of meiosis is metaphase 1. Explain how the organization of
homologous chromosomes during metaphase 1 increases genetic variation -correct
answer*independent assortment chromosomes line up at the Centre of the equator
each chromosome of the homologous pair is genetically different Xylem and phloem
are two vascular tissues found in plants. State one similarity and two differences
between the structure of xylem and phloem -correct answer*Similarity- both made
up of cells joined end to end Difference- xylem pits- phloem- no pits Difference- xylem
lignified- phloem-not lignified Difference- xylem no sieve tube elements- phloem
sieve tube elements 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. -correct answer*cut open the
exoskeleton trachea, muscle, spiracle, muscle What is the structure labelled A
-correct answer*Tracheole Describe how the trachea of a mammal is different from
the trachea shown in Fig 3 -correct answer*Mammals have just one trachea Insects
have multiple Mammal trachea is longer Insects trachae shorter Mammal trachea
larger diameter insects smaller diameter Alveoli are located in the lungs of mammals.
Explain how alveoli are adapted for efficient gas exchange. -correct answer*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 State two ways in which the
molecular structure of cholesterol is similar to the molecular structure of glucose
-correct answer*Both contain C and O 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 -correct answer*glucose is
soluble he students were provided with three different fruit juices labelled A, B and C.
The Benedict's test was carried out on each fruit juice and samples were prepared for
the colorimeter. Explain how the students would use the calibration curve to estimate
the glucose concentration of the fruit juices -correct answer*-find the absorption
-using the graph find the concentration which corresponds to the absorption -find the
absorption value The students wrote the following hypothesis 'the higher the
concentration of glucose in the fruit juice, the sweeter it will be' Describe how you
would carry out a controlled experiment to test this hypothesis without using a
colorimeter -correct answer*-Taste the fruit juices to see how sweet they are -place
each sample of the fruit juices in a biosensor and take the reading -rank order in
sweetness -compare rank orders for sweetness Suggest one reason why the results
Cell B in Fig. 1.1 was observed using an electron microscope. Give one piece of
evidence from Fig. 1.1 that supports this -correct answer*organelles can be seen in
more detail Give one way that an image produced by a laser scanning confocal
microscope differs from that produced by an electron microscope -correct
answer*laser scanning confocal microscope has lower resolution Meiosis is a type of
nuclear division. Fig. 1.2 shows a photomicrograph of plant cells undergoing meiosis
identify the stage of meiosis 1 shown in the cell labelled A -correct answer*prophase
(1) Based only on your observations of Fig.1.2, state two reasons for your answer in
(b)(i) -correct answer*chromosomes condense chromosomes still not aligned at the
equator Another stage of meiosis is metaphase 1. Explain how the organization of
homologous chromosomes during metaphase 1 increases genetic variation -correct
answer*independent assortment chromosomes line up at the Centre of the equator
each chromosome of the homologous pair is genetically different Xylem and phloem
are two vascular tissues found in plants. State one similarity and two differences
between the structure of xylem and phloem -correct answer*Similarity- both made
up of cells joined end to end Difference- xylem pits- phloem- no pits Difference- xylem
lignified- phloem-not lignified Difference- xylem no sieve tube elements- phloem
sieve tube elements 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. -correct answer*cut open the
exoskeleton trachea, muscle, spiracle, muscle What is the structure labelled A
-correct answer*Tracheole Describe how the trachea of a mammal is different from
the trachea shown in Fig 3 -correct answer*Mammals have just one trachea Insects
have multiple Mammal trachea is longer Insects trachae shorter Mammal trachea
larger diameter insects smaller diameter Alveoli are located in the lungs of mammals.
Explain how alveoli are adapted for efficient gas exchange. -correct answer*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 State two ways in which the
molecular structure of cholesterol is similar to the molecular structure of glucose
-correct answer*Both contain C and O 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 -correct answer*glucose is
soluble he students were provided with three different fruit juices labelled A, B and C.
The Benedict's test was carried out on each fruit juice and samples were prepared for
the colorimeter. Explain how the students would use the calibration curve to estimate
the glucose concentration of the fruit juices -correct answer*-find the absorption
-using the graph find the concentration which corresponds to the absorption -find the
absorption value The students wrote the following hypothesis 'the higher the
concentration of glucose in the fruit juice, the sweeter it will be' Describe how you
would carry out a controlled experiment to test this hypothesis without using a
colorimeter -correct answer*-Taste the fruit juices to see how sweet they are -place
each sample of the fruit juices in a biosensor and take the reading -rank order in
sweetness -compare rank orders for sweetness Suggest one reason why the results
