Growth and development

Question 1

What are the differences between plant, animal and bacterial cells?

Answer 1

• Bacterial cells differ from plant and animal cells in that they like a ‘true’ nucleus, mitochondria, and chloroplasts.
• As bacterial cells do not have a true nucleus, DNA is found in the cytoplasm as a single circular strand or chromosome.

Question 2

What does a diagram of a typical growth curve show?

Answer 2

• The main phases of growth.
• Two of these phases involve rapid growth; one is just after birth and the other in adolescence.

Question 3

What is the best measure of growth?

Answer 3

Dry mass

Question 4

What is an easy measurement to do?

Answer 4

Measuring growth by length is an easy measurement but only measures growth in one direction.

Question 5

Using wet mass for measuring growth.

Answer 5

Measuring wet mass is hard to do for some organisms, e.g. trees but is easy for animals. However, the water content of organisms can vary with time.

Question 6

What is the problem with measuring dry mass?

Answer 6

Dry mass can only be measured by killing the organism and driving off the water but it does measure the truth growth of the whole organism.

Question 7

Why do different parts of an organism grow at different rates

Answer 7

Different parts of an organism may grow a different rates compared to the whole organism. This is because different parts of the organism may be needed at different times during the life of the organism.

Question 8

What are stem cells?

Answer 8

Cells called stem cells stay undifferentiated. They can develop into different types of cells.

Question 9

Where can stem cells be obtained?

Answer 9

• Stem cells can be obtained from embryos and could potentially be used to treat some medical conditions.
• Stem cells can also be found in the adult as well as in the embryo. Embryonic stem cells can form a greater range of cell types and are easier to find.

Question 10

What are the issues arising from stem cell research in animals?

Answer 10

• Some people think that it is wrong because the embryos are destroyed
• Others think that it is acceptable as it can treat life-threatening diseases

Question 11

What are the differences between plant and animal growth?

Answer 11

• Animals tend to only grow to a certain size but many plants can carry on growing.
• Plant cell division only happens in areas called meristems, found at the tips of roots and shoots.
• The main way that plants gain height is by cells enlarging rather then dividing.
• Many plant cells keep the ability to differentiate, but most animal cells lose it at an early stage