Download Discuss - mrclay10scx

Discuss- Science 1.3
2007
2(b) Discuss how hyphae and sporangia aid the spread of a fungus. You should
consider their function and role in the spread.
2(b)
Function and role in spreading
described for either hyphae or
sporangia.
OR
Function or role in spreading
described for both hyphae and
sporangia
 Sporangia function eg spore
production, reproduction
 Sporangia role in spreading, eg
spore dispersal above ground,
bursting to release spores into the
air
 Hyphae function eg gaining
nutrients, feeding by
extracellular digestion
 Hyphae role in spreading, eg
growth of hyphae, hyphae
branchout, hyphae form
mycelium to cover a large area.
Explanation which links function
to role of spreading for either
sporangia or hyphae. Eg:
 Sporangia are above ground to
release spores into the air so they
are easily spread
 Sporangia disperse spores so new
fungi can grow further away
 Hyphae absorb nutrients which
allows further growth of the
hyphae into new food supply
 As the hyphae grow, new
sporangia are produced.
AND
 Role or function for other
structure.
Discussion considers how the
function of BOTH hyphae and
sporangia play a role in spreading
fungi. Eg:
 Sporangia produce spores
(Function) which are dispersed in
the air and grow into new fungi
(role of spread).
AND
 Hyphae absorb nutrients (function)
and grow to cover more area (role
of spread).
4(c) Discuss why sex cells have 23 chromosomes, whereas body cells have 46. Refer
to the cell division processes involved.
4(c)
Description of either type of cell
division in humans, eg:
 Mitosis produces cells with 46
chromosomes.
 Meiosis produces cells with 23
chromosomes.
 Body cells formed by mitosis
 Gametes formed by meiosis.
or
 Sex cells have 23 chromosomes
so that when a sperm fertilises an
egg the number is restored to 46.
A description of both types of cell
division (see achieved) plus an
explanation of why either type of
cell division occurs, eg:
Meiosis forms sex cells with half
chromosome number so that:
 Fertilisation does not cause
chromosome number to increase
each generation.
 When sperm meets egg the
chromosome number is restored
 So that offspring get a mix of
genes from two parents.
OR
Mitosis forms body cells with the
full chromosome number:
 so that all new cells can carry out
the same functions
 so that all cells have the full set
of instructions.
OR
 In meiosis the cell divides twice
but in mitosis it only divides
once.
Discussion includes a reason for each
type of division occurring, eg:
 Meiosis forms sex cells with half
chromosome number so that when
sperm meets egg the chromosome
number is restored to 46. Body cells
divide by mitosis so that each new
cell gets a full set of instructions.
 Meiosis produces sex cells with a
single set of chromosomes so that
the zygote will inherit alleles from
two parents to provide genetic
variation. Then the zygote grows by
mitosis which produces identical
cells that can carry out the same
functions.
5(f).In some breeds of rabbit, a plain coat colour is called solid; a blotchy coat colour
is called broken. Broken coat (B) is dominant to solid coat (b).
A solid-coated rabbit is crossed with a heterozygous broken-coated rabbit.
A breeder buys a rabbit with the broken coat trait.
Discuss the process that could be used to identify whether this rabbit is homozygous
or heterozygous for broken coat.
5(f)
Describes a test cross. Eg:
 Cross rabbit with a broken coat
trait with a solid coat rabbit.
 Cross broken coat rabbit with a
homozygous recessive rabbit
(bb).
Uses the results of one cross to
support the parent being either
homozygous or heterozygous. Eg:
 If some offspring have solid coat
colour, the parent is
heterozygous (Bb).
 If all of the offspring have
blotchy coat colour the parent is
(probably) homozygous (BB).
Labelled Punnett square may be
used to support answer.
Uses the results of both crosses to
identify the heterozygous parent with
certainty and the homozygous parent
as probable. Eg:
 If some offspring have solid coat
colour, the parent is heterozygous
(Bb).
 If all of the offspring have blotchy
coat colour after many matings
between the pair of rabbits, the
parent is almost certainly
homozygous (BB).
Labelled Punnett square may be
used to support answer.
2006
1(f) In terms of temperature and water content, discuss why milk powder can be
stored for a longer time than liquid milk.
1(f)
Description of any two aspects
of temperature, water content
or storage time for milk or
powder, eg:
 Powdered milk has no water
content and can be stored
along time.
 Powdered milk can be stored
in the pantry (room temp)
because it is dry.
 Milk has to be kept in the
fridge to stop it going off.
 Milk contains lots of water
so it will go off quickly.
Explanation of how
temperature OR water
content impacts on micro
organism activity, eg:
 Powder has no water
content and as such
bacteria can not
reproduce/grow in powder.
OR
 Milk must be kept in the
fridge to slow down micro
organism growth
Discussion of how
temperature AND moisture
impact on micro organism
activity in powder compared
with milk, eg:
 Micro organisms need
water to reproduce, milk
contains water and needs
to be stored in the fridge
to limit bacterial
reproduction.
AND
 Milk powder treated at a
high temp has no bacteria
so there are none to
reproduce.
OR
 Powder does not need to
be stored in the fridge as
bacterial growth is already
limited by a lack of water.
3. In a Shar-Pei dog, the length of its coat is controlled by a gene. Normal coat (short)
(N) is dominant to long coat (n). A male dog is heterozygous for normal coat.
(f)
3(f)
Discuss how you could determine whether a normal-coat dog was homozygous
or heterozygous. You may use Punnett squares to help answer the question.
States a test cross is carried
out.
OR
Describes cross with a
homozygous recessive.
Uses the results of one cross
to support the parent being
either homozygous or
heterozygous, eg:
 If some offspring are long
coated, the parent is
heterozygous (Nn).
 If all of the offspring are
short haired, the parent is
homozygous (NN).
Uses the results of both
crosses to identify the
heterozygous parent with
certainty and the
homozygous parent as
probable, eg:
 If some offspring are long
coated, parent must be
heterozygous.
 If all of the offspring are
short haired, it is probable
that the parent is
homozygous (NN).
4.
Discuss why a dog produced by cloning looks identical to the biological parent,
whereas a dog produced by sexual reproduction looks different from the parent.
4
Describes why either the cloned
offspring looks identical to
biological parent OR why it
looks different to the parent in
sexual reproduction, eg:
 cloned offspring is
genetically identical to the
biological parent
 cloned offspring gets all of
its’ DNA from only one
parent
 mitosis is used to produce
cloned offspring
 cloned offspring has the same
DNA as the parent
 offspring from sexual
reproduction are genetically
different from either parent
 offspring from sexual
reproduction get a set of
genetic material from each
parent
 sexual reproduction requires
meiosis to produce gametes.
Explanation of how both
processes provide OR
restrict genetic variation, eg:
 The cloned offspring is
identical to the biological
parent because it gets all
of its DNA from it.
AND
 Sexually reproduced
offspring are different
from the parents because
they get DNA/genes from
two different sources.
OR
If an excellence level
statement is given for either
cloning or sexual
reproduction AND an
achieved statement is given
for the other process.
Discussion of how both
processes result in the given
appearance with reference to
meiosis, eg:
 The cloned offspring is
genetically identical to the
biological parent because
it does not involve
meiosis/only involves
mitosis.
 One cell undergoes
mitosis so all cells are
genetically identical.
AND
 Sexual Reproduction
involves gametes
produced by meiosis. The
resulting offspring will
have a unique set of genes.
2005
1. The ancestral domestic cat (Felis domesticus) looked different from the many
modern breeds we see today.
(e) Discuss how, with the help of humans, these modern breeds have arisen from
a single ancestral type cat.
1(e)
Desired characteristic
selected / cats
bred together / selective
breeding.
Desired characteristic
selected :
these cats bred
together.
Desired characteristic
selected :
these cats bred together
:
offspring with desired
characteristic chosen to
breed :
generations / till
population is
purebreeding.
4. Campylobacter is a bacterium that causes food poisoning. It is often caught from
eating chicken.
(b) Discuss how the storage temperature and cooking temperature of chicken
affect the life processes of the campylobacter bacterium.
4(b)
Any one of
cooling / refrigeration
/ freezing
slows
reproduction/growth
cooling slows the rate
of cell
reactions
cooking is done at
high
temperatures.
ONE explained plus
ONE other
mentioned
freezing: bacteria
dormant /
not reproducing
Refrigeration : slows
reproduction
high temperatures kill
bacteria
if chicken not
thoroughly
cooked in middle : not
hot
enough to kill bacteria.
heating / room temp
increases
the reproduction rates
of
bacteria
Effect of both storage
temperature and
cooking
temperature on life
process.
Freezing : bacteria
dormant /
not reproducing or
Refrigeration : slows
reproduction / bench :
faster
reproduction.
High temperatures
kill
bacteria / if chicken not
thoroughly cooked in
middle
: not hot enough to kill
bacteria.
5. All living things have several common characteristics.
(b)
5(b)
Discuss whether a virus is alive or not. You should compare the virus’s
characteristics to those common to all living things.
Any one of:
Viruses only reproduce
/ Viruses are
not cells / Viruses do
not grow /
excrete / sense their
environment /
need nutrition / respire /
Viruses have
genetic material like
living things.
Uses THREE aspects
of
MRSGREN that
qualifies the life
choice.
OR
Virus alive (or not) :
replicate /
reproduce : living host.
Life choice qualified
and
contrasted.
Virus alive (or not) :
replicate /
reproduce : living host
AND
Virus alive (or not) :
THREE
reasons (from
MRSGREN).