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Looking into the Invisible World
Answers
Worksheet 1 Wonders of the microscopic world
Time to Think (p. 8)
1.
Technology for making high-quality glass and grinding glass to make lenses
was essential to the invention of the telescopes and microscopes.
2.
The telescope allowed scientists to make accurate observations of the motion
and appearances of celestial bodies in the sky. The invention of the microscope
enabled scientists to examine objects that were too small to be seen by the
unaided eye.
3.
A compound microscope is made up of two or more sets of lenses. It has a
much higher magnifying power than a hand lens thus it is more useful.
4.
The pictures in Micrographia were beautifully drawn. They were scientifically
accurate and showed the great details of microscopic structures that had never
been seen before.
5.
The “cells” observed by Hooke were the cell wall of cork cells which are devoid
of any cell contents.
6.
Hooke suggested that there had been major changes in the crust of the Earth,
and parts which had been sea became land, and mountains had been turned into
plains, and plains into mountains.
7.
It is essential to make accurate and objective observations to test proposed
ideas.
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Looking into the Invisible World
Answers
Worksheet 2 Developing a theory for the role of cells
Time to Think (p. 17)
1.
Hooke saw many small pores under the microscope. So he called these
structures “cells”, meaning small pores.
2.
Grew meant that there were numerous little cells present.
3.
Without staining, animal cells could only be faintly observed under the
microscope and most internal structures could not be distinguished.
4.
He added dyes to the plant cells so that the nuclei became darkly stained.
5.
Schleiden showed that all plant tissues are made up of cells, and each cell
possesses a nucleus. Schwann found that all animal tissues were made up of
cells with nuclei. Virchow proposed that all cells come from other cells.
6.
Virchow noted that cells of an embryo duplicated themselves by means of cell
division.
7.
He referred to the example that tumours are derived from pre-existing cells in
the body.
Infectious diseases caused by pathogens cannot be explained by his hypothesis.
8.
We can study the function of individual cells to understand the life processes of
the whole organism. This approach allows scientists to study life processes in
isolation in a more easily controlled manner.
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© Times Publishing (Hong Kong) Limited
Looking into the Invisible World
Answers
Worksheet 3 Understanding the relationship between genes and chromosomes
Time to Think (p. 23)
1.
Mendel’s ideas were too far ahead of his time and scientists were not yet ready
to appreciate the significance of his findings.
2.
“Chromosomes” mean bodies that take up coloured dyes. Development of
staining techniques for tissues was essential for the discovery of chromosomes
in the nucleus.
3.
A cell has different kinds of chromosomes with distinctive shape and length.
They carry different genes.
4.
Each cell receives one member of the homologous chromosome from each
parent.
5.
23 chromosomes
6.
They found that the patterns of inheritance of genes proposed by Mendel
paralleled the behaviour of chromosomes observed during gamete formation
and fertilisation.
7.
Sutton’s theory states that a characteristic is controlled by a pair of genes which
are located on each member of a chromosome pair.
8.
Suggested answer: to show that DNA is located on the chromosomes; to find out
whether the amount of DNA in a body cell is double that in a gamete.
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