Growth & Differentiation

• What are plant meristems?

  area where rapid cell division occurs in the tips of roots and shoots
• Give two advantages of using plant meristems to clone plants

  • rare species can be cloned to protect them from extinction

  • plants with special features (e.g. disease resistance) can be cloned to produce many copies
• Give one disadvantage of using plant meristems to clone plants.

  no genetic variation, so, for example, an entire cloned crop could be destroyed by a disease
• How many cells does an adult human contain?

  Approximately 37.2 trillion.
• Why are cells of a multi-cellular organism not all the same?

  as the cells grow, divide and develop, they differentiate
• What are unspecialised cells called?

  stem cells
• When do most animal cells differentiate?

  early in development
• What happens if some differentiated cells can't divide?

  They are replaced by adult stem cells, like those found in the bone marrow
• When do plant cells differentiate?

  throughout their life
• What do plant cells actively divide?

  tissues called meristems
• What do the cells produced by mitosis in the meristem do?

  elongate and differentiate
• Why are plants easy to clone?

  the cells can become unspecialised, divide by mitosis and then differentiate into the various types of plant cell.
• Why is it difficult to clone animal cells?

  once the cells are differentiated they can't become unspecialised again