b5.1

Question 1

1. What can cells in multicellular organisms be?

Answer 1

-cells in multicellular organisms can be specialised to do particular jobs

Question 2

2. What are groups of specialised cells called?

Answer 2

-tissues

Question 3

2. What an organ?

Answer 3

-a group of tissues

Question 4

3. What is another word for a fertilised egg cell?

Answer 4

-zygote

Question 5

3. How does a fertilised egg cell (zygote) form an embryo?

Answer 5

-it divides by mitosis

Question 6

4. What are the cells that in a human embryo up to (and including) the eight cell stage?

Answer 6

• all the cells are identical (embryonic stem cells)

- they are undifferentiated

Question 7

4. What does human embryo cells being undifferentiated in the early stages mean they can do?

Answer 7

-they could produce any type of cell required by the organism

Question 8

5. What happens to embryo cells after the eight cell stage?

Answer 8

• most of the embryo cells become specialised and form different types of tissue
• this is called differentiation

Question 9

6. What are adult stem cells?

Answer 9

-cells that remain unspecialised after the eight cell stage

Question 10

6. What can adult stem cells be specialised into at a later stage?

Answer 10

-to become many, but not all, types of cell required by the organism

Question 11

7. In plants where are mitotically active cells found?

Answer 11

-within special regions called meristems

Question 12

7. What does mitotically active mean?

Answer 12

-divide by mitosis

Question 13

8. What are the new cells produced from plant meristems?

Answer 13

• unspecialised

- can develop into any kind of plant cell

Question 14

9. What can unspecialised plant cells become specialised to form? What are examples of this?

Answer 14

-different types of tissue (including xylem and phloem) within organs (including flowers, leaves, stems and roots)

Question 15

10. What does the presence of meristems (as sources of unspecialised cells) allow?

Answer 15

• the production of clones of a plant from cuttings
• (as cuttings from areas of a plant that is growing will contain unspecialised meristem cells that can differentiate to make any type of cell, even a whole new plant)

Question 16

10. Why may cloning pants using cuttings be done?

Answer 16

-to reproduce a plant with desirable features

Question 17

11. What can a cut stem from a plant do?

Answer 17

-it can develop roots and then grow into a complete plant which is a clone of the parent

Question 18

11. How can rooting be promoted?

Answer 18

-that rooting can be promoted by the presence of plant hormones (auxins) in rooting powders

Question 19

12. What is another factor that affects the growth and development of plants?

Answer 19

-the environment

Question 20

12. What is an example of environment affecting the growth and development of plants?

Answer 20

-phototropism

Question 21

13. What is phototropism?

Answer 21

-when parts of a plant respond to light by growing in a certain direction

Question 22

13. How do different types of phototropism increase the plant’s chance of survival?

Answer 22

• Positive Phototropism: plant needs sunlight for photosynthesis to produce food for energy and growth- helps as shoots grow towards light so leaves can get more light for photosynthesis
• Negative phototropism: plants need soil for nutrients and water to grow- helps as roots grow away from light so they can absorb water and nutrients to grow

Question 23

14. What are auxins?

Answer 23

-chemicals that control the growth near tips of shoots and in roots

Question 24

14. How do auxins make stem tips grow?

Answer 24

-they diffuse backwards behind tips to elongate the cells

Question 25

14. What happens if a tip of a shoot is removed?

Answer 25

-if all auxins are removed it might not be able to grow

Question 26

14. How do auxins make shoots grow towards light?

Answer 26

-shoot tip exposed to light= auxins accumulate on side in shade =cells elongate faster on shaded side= shoot grows towards light