Biology- Topic 3

Question 1

What are TEMs?

Answer 1

Transmission electron microscopes

• Only used on thin specimens
• high resolution
• beam of electrons

Question 2

What are SEMs?

Answer 2

Scanning electron microscopes

• 3D images
• used in thick specimens
• lower resolution
• electrons knocked off gathered in cathode ray tube

Question 3

What are the layers of the leaf?

Answer 3

Lower epidermis 
Spongy mesophyll 
Palisade mesophyll
Xylem
Phloem
Upper epidermis

Question 4

2 ways for genetic differentiation and describe

Answer 4

Crossing over chromatids- when condensing can cross over and be pulled apart in meiosis
Independent assortment of chromosomes- different combinations from maternal and paternal chromosomes go into each cell

Question 5

2 ways genes are linked and describe

Answer 5

Loci- location close, unlikely to be split up when crossing over
Sex-Linked- carried on larger X chromosome

Question 6

How use of stem cells is controlled?

Answer 6

Laws
Regulatory bodies
Codes of practice
Monitoring 
Taken in account ethical issues

Question 7

Describe the appearance of chromosomes undergoing mitosis

Answer 7

Visible
Joined to spindle fibres
Pair of chromosomes held together

Question 8

What are tissues?

Answer 8

Group of similar cells. That are specially adapted to work with each other to carry out a specific function.

Question 9

What are organs?

Answer 9

Groups of different tissues working together