Cell Division, Diversity and Organisation - Levels of Organisation Flashcards
define cells
the smallest structural and functional unit of an organism
may be specialised to perform a specific function
define tissues
collection of different types of specialised cells working together to perform a particular function
define organs
collection of tissues working together to perform a particular function
define organ systems
organs working together to perform a life function
describe squamous epithelia
- lining tissue
- flattened smooth cells
- basement membrane
where are squamous epithelia found
- lining of blood vessels
- alveoli
how are squamous epithelia adapted for their function
low friction, short diffusion pathway
describe the basement membrane
made of collagen and glycoproteins. attaches cells to connective tissue
describe ciliated epithelia
- column shaped cells
- basement membrane
where are ciliated epithelia found
- trachea
- bronchi
- bronchioles
- oviduct
what is the function of ciliated epithelia
waft mucus or ovum in a synchronised movement
describe cartilage and where it is found
- connective tissue
- chondrocyte cells (found in cartilage) secrete an extracellular matrix
- elastin and collagen fibres
- ends of bones
- ear and nose
describe muscle and its function
- skeletal muscle contracts to move bones
- muscles contain multinucleate fibres
- striated appearance due to bands of actin and myosin filaments
describe xylem tissue and its adaptations
- 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
describe phloem tissue and its adaptations
- 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
give an example of an organ in a plant
leaf
why are companion cells needed
sugar transport in sieve tubes requires energy from the plant. companion cells are involved in this process
describe the structure of a leaf
- waxy cuticle
- upper and lower epidermis
- palisade mesophyll
- spongy mesophyll
- stoma
- guard cells
- vascular bundle (contains xylem and phloem)
which is on top in the vascular bundle
xylem
describe the waxy cuticle and its function
a waxy layer that covers the leaf and reduces water loss (not a tissue)
describe the upper epidermis and its function
- usually a single layer of cells
containing no chloroplasts. - the cells are quite transparent and let light through to the underlying cells
- protection
describe the palisade mesophyll layer and its function
long thin tightly packed cells containing many chloroplasts for maximum rate of photosynthesis
describe the spongy mesophyll layer and its function
- irregular loosely packed cells with some chloroplasts.
- air spaces allow for diffusion of gases.
- some photosynthesis
describe the stoma and their function
pores mainly in the lower epidermis to allow for gas exchange
describe guard cells and their function
- two cells surround each stoma.
- when turgid they open the pore (for gas exchange) and when flaccid they close it to reduce water loss
describe the vascular bundle and its function
- supports the leaf as well as transporting substances
- xylem = transport or water and mineral ions
- phloem = transport of the products of photosynthesis
