unit 5 practicals questions Flashcards
outline the procedure to investigate the digestion of starch agar using germination seeds
- cut seeds in half
- place seeds on starch agar on a petri dish, and leave for 12-48 hours at 25°ac
- set up the control
- pour iodine onto the plates and measure the area of the clear zone
what does the zone of inhibition indicate?
- the clear zone indicates that starch has been hydrolysed by amylase (hence stained by iodine)
- the larger the zone of inhibition, the higher the amylase concentration / greater the amylase activity
state 3 factors that may affect the rate of amylase activity
- age of seed
- gibberellin content
- temperature / pH
how is the control set up in this practical?
- heat half of the seeds in a water bath above 80°C to denature the enzymes present
- then cooled
why is the control set up?
to show that the difference in the size of the clear zone is due to the presence of enzymes in the seed
what are some controlled variables of this practical?
- time left on starch agar plate
- source/age of seeds
- type/species of seed
- volume/concentration of agar used
- germination time
- temperature
- pH
- water availability
introduction to practical:
- the endosperm of a seed is the food source which surrounds the embryo
- it consists primarily of starch as well as proteins and oils
- during germination, starch in the endosperm is hydrolysed to maltose by amylase
the digestion of starch by germinating seeds can be investigated using starch agar plates
hazards, risks, precautions for practical?
- iodine - irritation to eyes and skin - wear safety goggles and gloves
- broken glass - cuts - keep glassware away from edge of desk
- scalpel - cuts - direction of cut away from the body
- boiling water - scalding - handle boiling water with care; use tongs to transfer boiling tubes; wear safety goggles
- water bath - electric shock - ensure hands are dry before plugging in/unplugging water bath
- seeds are maintained at 20°C to reduce the risk of growing potentially harmful contaminants
list some abiotic factors
- light intensity
- temperature
- humidity
- wind speed
- water supply
- day length
- nutrient supply
- rainfall
list some biotic factors
- competition for resources
- predation
- disease
how is % cover calculated?
- use a quadrat with squares
- count how many squares the required species is present in
- only count a square is more than half of the square is covered
outline the procedure of random sampling:
- choose an area to take samples. use a random number generator to generate 10 sets of random coordinates
- use two tape measures to create a set of axes off which coordinates can be read
- place the quadrat at each of the coordinates, placing the bottom left corner on the coordinate every time
- record the percentage cover for the chosen species
- at each coordinate, a measure of the independent variable should be taken
how can the results be used to determine the relationship between the chosen factor and the percentage cover?
- use a statistical test
- e.g Pearson’s linear correlation, Spearman’s rank
state simpson’s index of biodiversity
D = 1- [(n/N)2]
what is species diversity?
the number of difference species in a community and the relative abundance of each population
what is the advantage of random sampling?
- prevents selective sampling from causing bias
outline the procedure of using a transect for systematic sampling:
- use a measurement tape to make a transect over the area you wish to sample
- place quadrats at given intervals along the tape measure (e.g. every 5 metres). the bottom left hand corner of each quadrat should be touching the relevant meter mark, and the left hand edge runs along the tape measure
- identify the different species in each quadrat using a key and count the number of each present
- calculate the percentage cover
which type of graph is used to represent the distribution of a species along a transect?
- a kite diagram
state a hazard and safety precaution involved in the practical of dissection of flowers
- flowers may cause an allergic reaction
- avoid using species of plants that can cause allergic reactions
what is the epidermis of an anther?
- the thin outermost layer of tissue surrounding the anther
what is the pollen sac of an anther?
- a circular structure containing developing pollen grains
where is the vascular tissue found in an anther?
in a bundle at the centre of the anther
what is the stomium of an anther?
the area between 2 pollen sacs