Cell Division, Diversity and Organisation - Levels of Organisation

Question 1

define cells

Answer 1

the smallest structural and functional unit of an organism
may be specialised to perform a specific function

Question 2

define tissues

Answer 2

collection of specialised cells working together to perform a particular function (cells often of the same type and may be attached to each other)

Question 3

define organs

Answer 3

collection of tissues working together to perform a particular function

Question 4

define organ systems

Answer 4

organs working together to perform a life function

Question 5

describe squamous epithelia

Answer 5

• lining tissue
• flattened smooth cells
• basement membrane

Question 6

where are squamous epithelia found

Answer 6

• lining of blood vessels
• alveoli

Question 7

how are squamous epithelia adapted for their function

Answer 7

low friction, short diffusion pathway

Question 8

describe the basement membrane

Answer 8

made of collagen and glycoproteins. attaches cells to connective tissue

Question 9

describe ciliated epithelia

Answer 9

• column shaped cells
• basement membrane

Question 10

where are ciliated epithelia found

Answer 10

• trachea
• bronchi
• bronchioles
• oviduct

Question 11

what is the function of ciliated epithelia

Answer 11

waft mucus or ovum in a synchronised movement

Question 12

describe cartilage and where it is found

Answer 12

• connective tissue
• chondrocyte cells (found in cartilage) secrete an extracellular matrix
• elastin and collagen fibres
• ends of bones
• ear and nose

Question 13

describe muscle and its function

Answer 13

• skeletal muscle contracts to move bones
• muscles contain multinucleate fibres
• striated appearance due to bands of actin and myosin filaments

Question 14

describe xylem tissue and its adaptations

Answer 14

• thick, strong cell walls containing cellulose and lignin to support a plant
• pits allow some lateral water movement
• xylem vessels are dead and have no cytoplasm so all the space inside can be used to transport water and minerals
• xylem vessels join end to end to form long, continuous tubes to transport water and minerals from water to leaves

Question 15

describe phloem tissue and its adaptations

Answer 15

• sieve tube cells are connected to each other through sieve plates that have many pores allowing sugars to be transported
• sieve tubes have a modified cytoplasm with few organelles, so the tube can transport sugars
• companion cells

Question 16

give an example of an organ in a plant

Answer 16

leaf

Question 16

why are companion cells needed

Answer 16

sugar transport in sieve tubes requires energy from the plant. companion cells are involved in this process

Question 17

describe the structure of a leaf

Answer 17

• waxy cuticle
• upper and lower epidermis
• palisade mesophyll
• spongy mesophyll
• stoma
• guard cells
• vascular bundle (contains xylem and phloem)

Question 18

which is on top in the vascular bundle

Answer 18

xylem

Question 19

describe the waxy cuticle and its function

Answer 19

a waxy layer that covers the leaf and reduces water loss (not a tissue)

Question 20

describe the upper epidermis and its function

Answer 20

• usually a single layer of cells
  containing no chloroplasts.
• the cells are quite transparent and let light through to the underlying cells
• protection

Question 21

describe the palisade mesophyll layer and its function

Answer 21

long thin tightly packed cells containing many chloroplasts for maximum rate of photosynthesis

Question 22

describe the spongy mesophyll layer and its function

Answer 22

• irregular loosely packed cells with some chloroplasts.
• air spaces allow for diffusion of gases.
• some photosynthesis

Question 23

describe the stoma and their function

Answer 23

pores mainly in the lower epidermis to allow for gas exchange

Question 24

describe guard cells and their function

Answer 24

• two cells surround each stoma.
• when turgid they open the pore (for gas exchange) and when flaccid they close it to reduce water loss

Question 25

describe the vascular bundle and its function

Answer 25

• supports the leaf as well as transporting substances
• xylem = transport or water and mineral ions
• phloem = transport of the products of photosynthesis