Edexcel IAL biology Unit 2
(make sure to see how many marks the graph q is worth and the command word.
generally, 2/3 m q that are worded exactly like this one MUST be answered like this. you
must clearly mention the increase or decrease of the variable when describing the graph
and also giving the data manipulation!) (take 1-2 mins only for these q and make sure to
look at the graph as revise the correction)
using the information in the graph, describe the changes in the growth of this pollen
tube. (3) - ANS - 1. the rate of growth of the pollen tube is variable or inconsistent or
fluctuating.
2. as the time passes after germination, the pollen tube length increases.
3. the length of the pollen tube increases by 42 um from 5 minutes to 45 minutes.
\acrosome reaction - ANS - 1. when the sperm touches the ovum, acrosome releases
acrosin.
2. the acrosome fuses with cell surface membrane of sperm.
3. the acrosin will be released by exocytosis and will digest the zona pellucida and allow
the sperm to penetrate through the barrier.
\adaptations of xylem to carry its function - ANS - 1. xylem starts of as living tissue and
the first xylem produced is protoxylem which can be stretched and grown with the
growth of plants. thus, it provides flexibility.
\adaptive speciation - ANS - it occurs when one species develops rapidly to form several
different species which occupy different ecological niches. it occurs after allopatric
speciation
\after fertilisation, the egg cell divides by mitosis to form a blastocyst.
during this process, totipotent cells become pluripotent. describe how a totipotent stem
cell becomes a pluripotent cell. (3)
take a moment to read, understand and construct a nice structure for your answer. make
a little note on the blank page given if required. but ofcourse make sure to finish 3 mark
qs within 2-3 minutes. try finish the long qs at the end of the paper first then do the
beginning. see if it speeds up your progress. - ANS - 1. differential gene expression.
2. some genes have been permanently switched off or inactivated.
3. by epigenetic modification.
4. proteins or enzymes made from active genes which permanently modify the cell.
\allopatric speciation - ANS - geographical isolation followed by mutations can result in
the formation of a new species. this can be illustrated with the finches of the Gala pagos
islands. there are many different species in the Gala Pagos islands ultimately from a
common ancestral species.
\amyloplast - ANS - it is also double membrane bounded organelle. produced by
leucoplast and present in some plant cells such as potato. it stores amylopectin a form of
starch
,\anaphase - ANS - 1. the overlapping microtubules (spindle fibres) contract - this uses
energy, pulling chromatids from each pair to opposite poles.
2. pairs of chromatids have been separated to opposite ends.
\Behavioural isolation - ANS - populations don't respond to each others reproductive
displays.
\captive breeding and genetic diversity - ANS - 1. '18 individuals is a small
population/small gene pool/low genetic diversity/may have been closely related.
2. captive breeding will increase population.
3. the animals can be taken care of in zoos.
4. they can also be exchanged from different zoos and may mate with other animals of
different zoos.
5. this will lead to an increase in their population size as more offspring will be produces.
6. there will also be more genetic diversity.
7. stud books can be kept to select mates.
8. inbreeding must be prevented to avoid genetic drift.
9. IVF (pg 144) can be done to make sure fertilization is successful. the zygote can be
implanted into a surrogate mother.
10. genetic diversity can be measured using DNA profiling.
\cellulose microfibrils - ANS - many beta-glucose units are held together by
1,4-glycosidic bonds to form cellulose in a condensation reaction. every alternative
monomer unit has to be turned round/inverted so the bonding can take place. the
cellulose molecules formed are unbranched chains and these chains are held together by
hydrogen bonds. this is called cross-linking (holding neighbouring bonds together)
\chloroplast - ANS - it is a double membrane bounded organelle. some inner membrane
stack to grana in which fluid is filled. thylakoid is present. in thylakoid chlorophyll is
present which traps light energy and converts into chemical energy for photosynthesis.
stroma contains enzymes which catalyzes chemical reactions to reduce CO2 into
glucose. stroma also contains loop of DNA controls the synthesis of protein needed for
chemical reactions in photosynthesis
\clinical trials/contemporary drug testing protocols - ANS - phase 1 : tested on small
group of healthy volunteers.
phase 2 : larger group of patients with the disease. must be split into two groups. one
group will be given the placebo. (neither the doctor or patient will know who got the new
drug) - mine
phase 3 : compared to existing treatments on thousands of patients (double blind trials)
\composition and function of cell membrane - ANS - - it is made up of lipid and protein.
- 1. it acts as a selectively permeable membrane.
2. osmosis, diffusion, facilitated diffusion and active transport occurs through cell
membrane.
3. exocytosis, endocytosis and pinocytosis occurs through the cell membrane.
4. it acts as a sac like structure holding cytoplasm and organelle inside it.
\composition and function of cell wall - ANS - - it is made up of peptidoglycan.
- It provides bacterium a particular shape and prevents bacteria from injury.
, \composition and function of chromosome or nucleoid - ANS - - chromosomes in bacteria
are not bounded by nuclear membrane. it means that bacteria are prokaryotic organisms.
in addition to this bacteria don't have other membrane bounded organelles like
mitochondria, Golgi apparatus, Endoplasmic reticulum. chromosomes is made up of
DNA and histone.
- 1. it controls the synthesis of protein.
2. it also contains genes - hereditary material.
\composition and function of cytoplasm - ANS - - it is made up of water and other organic
substance such as enzymes, stored glycogen etc and inorganic substance such as
mineral ions eg - Na+, K+, Cl- etc
- 1. it provides a basis for chemical reaction to occur.
2. it regulates osmotic potential in a cell.
3. organelles such as ribosome chromosome, plasmid etc are suspended in cytoplasm.
\composition and function of flagellum - ANS - - it is made up of chemical called flagellin.
- it is used by bacterium to propel or move through aquatic environment.
\composition and function of mesosome - ANS - - it is infolding of cell membrane. it is
made of lipid and protein.
- aerobic respiration occurs in mesosoma.
\composition and function of mitochondria - ANS -
\composition and function of plasmid - ANS - - it is made up of extra nuclear substance
and it is used as a vector to carry desired gene used in biotechnology. plasmid also
contains mutated gene.
\composition and function of ribosome - ANS - - it is made up of protein and RNA.
- it is here protein synthesis occurs.
\composition and function of slime layer - ANS - - it is made up of mucopolysaccharide.
- 1) it prevents bacterium from being digested by many organisms.
2) it prevents bacterium from being desiccated.
\cons for seedbank - ANS - 1. are not of interest to public.
2. cannot spread awareness/raise funds easily.
\continuous variation - ANS - 1. it deals with a range of phenotypic expressions.
2. it is controlled by many genes.
3. it shows additive effect.
4. it is affected by the environmental changes.
5. examples - height, skin colour, synthesis of haemoglobin
\cortical reaction - ANS - when the sperm cell fuses with the egg cell membrane, cortical
granules in the cytoplasm of the ovum release enzymes into the zona pellucida. these
enzymes destroy the sperm-binding sites and also thicken and harden the jelly of the
zona pellucida to form a tough fertilisation membrane. the ion channels in the cell
membrane of the ovum open and close inside the cell, instead of being electrically
negative with respect to the outside, becomes positive. these all prevent polyspermy.
\critical evaluation of scientific ideas - ANS - 1. scientific findings can be published in a
journal or newspaper.
2. they can also be presented in a scientific conference.
(make sure to see how many marks the graph q is worth and the command word.
generally, 2/3 m q that are worded exactly like this one MUST be answered like this. you
must clearly mention the increase or decrease of the variable when describing the graph
and also giving the data manipulation!) (take 1-2 mins only for these q and make sure to
look at the graph as revise the correction)
using the information in the graph, describe the changes in the growth of this pollen
tube. (3) - ANS - 1. the rate of growth of the pollen tube is variable or inconsistent or
fluctuating.
2. as the time passes after germination, the pollen tube length increases.
3. the length of the pollen tube increases by 42 um from 5 minutes to 45 minutes.
\acrosome reaction - ANS - 1. when the sperm touches the ovum, acrosome releases
acrosin.
2. the acrosome fuses with cell surface membrane of sperm.
3. the acrosin will be released by exocytosis and will digest the zona pellucida and allow
the sperm to penetrate through the barrier.
\adaptations of xylem to carry its function - ANS - 1. xylem starts of as living tissue and
the first xylem produced is protoxylem which can be stretched and grown with the
growth of plants. thus, it provides flexibility.
\adaptive speciation - ANS - it occurs when one species develops rapidly to form several
different species which occupy different ecological niches. it occurs after allopatric
speciation
\after fertilisation, the egg cell divides by mitosis to form a blastocyst.
during this process, totipotent cells become pluripotent. describe how a totipotent stem
cell becomes a pluripotent cell. (3)
take a moment to read, understand and construct a nice structure for your answer. make
a little note on the blank page given if required. but ofcourse make sure to finish 3 mark
qs within 2-3 minutes. try finish the long qs at the end of the paper first then do the
beginning. see if it speeds up your progress. - ANS - 1. differential gene expression.
2. some genes have been permanently switched off or inactivated.
3. by epigenetic modification.
4. proteins or enzymes made from active genes which permanently modify the cell.
\allopatric speciation - ANS - geographical isolation followed by mutations can result in
the formation of a new species. this can be illustrated with the finches of the Gala pagos
islands. there are many different species in the Gala Pagos islands ultimately from a
common ancestral species.
\amyloplast - ANS - it is also double membrane bounded organelle. produced by
leucoplast and present in some plant cells such as potato. it stores amylopectin a form of
starch
,\anaphase - ANS - 1. the overlapping microtubules (spindle fibres) contract - this uses
energy, pulling chromatids from each pair to opposite poles.
2. pairs of chromatids have been separated to opposite ends.
\Behavioural isolation - ANS - populations don't respond to each others reproductive
displays.
\captive breeding and genetic diversity - ANS - 1. '18 individuals is a small
population/small gene pool/low genetic diversity/may have been closely related.
2. captive breeding will increase population.
3. the animals can be taken care of in zoos.
4. they can also be exchanged from different zoos and may mate with other animals of
different zoos.
5. this will lead to an increase in their population size as more offspring will be produces.
6. there will also be more genetic diversity.
7. stud books can be kept to select mates.
8. inbreeding must be prevented to avoid genetic drift.
9. IVF (pg 144) can be done to make sure fertilization is successful. the zygote can be
implanted into a surrogate mother.
10. genetic diversity can be measured using DNA profiling.
\cellulose microfibrils - ANS - many beta-glucose units are held together by
1,4-glycosidic bonds to form cellulose in a condensation reaction. every alternative
monomer unit has to be turned round/inverted so the bonding can take place. the
cellulose molecules formed are unbranched chains and these chains are held together by
hydrogen bonds. this is called cross-linking (holding neighbouring bonds together)
\chloroplast - ANS - it is a double membrane bounded organelle. some inner membrane
stack to grana in which fluid is filled. thylakoid is present. in thylakoid chlorophyll is
present which traps light energy and converts into chemical energy for photosynthesis.
stroma contains enzymes which catalyzes chemical reactions to reduce CO2 into
glucose. stroma also contains loop of DNA controls the synthesis of protein needed for
chemical reactions in photosynthesis
\clinical trials/contemporary drug testing protocols - ANS - phase 1 : tested on small
group of healthy volunteers.
phase 2 : larger group of patients with the disease. must be split into two groups. one
group will be given the placebo. (neither the doctor or patient will know who got the new
drug) - mine
phase 3 : compared to existing treatments on thousands of patients (double blind trials)
\composition and function of cell membrane - ANS - - it is made up of lipid and protein.
- 1. it acts as a selectively permeable membrane.
2. osmosis, diffusion, facilitated diffusion and active transport occurs through cell
membrane.
3. exocytosis, endocytosis and pinocytosis occurs through the cell membrane.
4. it acts as a sac like structure holding cytoplasm and organelle inside it.
\composition and function of cell wall - ANS - - it is made up of peptidoglycan.
- It provides bacterium a particular shape and prevents bacteria from injury.
, \composition and function of chromosome or nucleoid - ANS - - chromosomes in bacteria
are not bounded by nuclear membrane. it means that bacteria are prokaryotic organisms.
in addition to this bacteria don't have other membrane bounded organelles like
mitochondria, Golgi apparatus, Endoplasmic reticulum. chromosomes is made up of
DNA and histone.
- 1. it controls the synthesis of protein.
2. it also contains genes - hereditary material.
\composition and function of cytoplasm - ANS - - it is made up of water and other organic
substance such as enzymes, stored glycogen etc and inorganic substance such as
mineral ions eg - Na+, K+, Cl- etc
- 1. it provides a basis for chemical reaction to occur.
2. it regulates osmotic potential in a cell.
3. organelles such as ribosome chromosome, plasmid etc are suspended in cytoplasm.
\composition and function of flagellum - ANS - - it is made up of chemical called flagellin.
- it is used by bacterium to propel or move through aquatic environment.
\composition and function of mesosome - ANS - - it is infolding of cell membrane. it is
made of lipid and protein.
- aerobic respiration occurs in mesosoma.
\composition and function of mitochondria - ANS -
\composition and function of plasmid - ANS - - it is made up of extra nuclear substance
and it is used as a vector to carry desired gene used in biotechnology. plasmid also
contains mutated gene.
\composition and function of ribosome - ANS - - it is made up of protein and RNA.
- it is here protein synthesis occurs.
\composition and function of slime layer - ANS - - it is made up of mucopolysaccharide.
- 1) it prevents bacterium from being digested by many organisms.
2) it prevents bacterium from being desiccated.
\cons for seedbank - ANS - 1. are not of interest to public.
2. cannot spread awareness/raise funds easily.
\continuous variation - ANS - 1. it deals with a range of phenotypic expressions.
2. it is controlled by many genes.
3. it shows additive effect.
4. it is affected by the environmental changes.
5. examples - height, skin colour, synthesis of haemoglobin
\cortical reaction - ANS - when the sperm cell fuses with the egg cell membrane, cortical
granules in the cytoplasm of the ovum release enzymes into the zona pellucida. these
enzymes destroy the sperm-binding sites and also thicken and harden the jelly of the
zona pellucida to form a tough fertilisation membrane. the ion channels in the cell
membrane of the ovum open and close inside the cell, instead of being electrically
negative with respect to the outside, becomes positive. these all prevent polyspermy.
\critical evaluation of scientific ideas - ANS - 1. scientific findings can be published in a
journal or newspaper.
2. they can also be presented in a scientific conference.
