Paper 1 Collection Flashcards

Question 1

Q

SB1b CP - How do you use use a microscope?

Answer

A

Put a thin sample of tissue (e.g. onion epidermis) onto a microscope slide
Add a few drops of a suitable stain/dye (e.g. iodine), so that the sample can be seen
Place a coverslip on top of the tissue and place the slide onto the microscope stage.
Use the objective lens with the lowest magnification, and focus on the sample.
Increase the magnification and refocus to see different features of the cell.
If you record the image you see, note down the magnification it was taken at

Option 2: You microhope you’re doing it right

Question 2

Q

SB1a - What determines how good a microscope is at showing small details?

Answer

A

Magnification: How much it can zoom in
Resolution: The smallest distance between two distinctly different points

Question 3

Q

SB1a - What has the development of the electron microscope allowed us to do?

Answer

A

It has allowed us to see sub-cellular structures as they have a much more powerful resolution and magnifcation

Question 4

Q

SB1a - SI units - For Chris’s benefit

[i.e definitely not becuase I dont’ know it]

Answer

A

milli = x10^-3
micro= x10^-6
nano=x10^-9
pico=x10^-12

Question 5

Q

SB1b - How are animal cells different to plant cells?

Answer

A

Animal cells, do not have cell walls, chloroplasts or vacuoles like plants do.
They only have nuclei, ribosomes, mitochondria, cytoplasm and a cell surface membrane.

Question 6

Q

SB1b - What do the sub-cellular structures in eukaryotic cells do?

Answer

A

Cell membrane: controls what enters and leaves the cell
Nucleus: contains DNA that controls cell activities
Cytoplasm: fills the cell and where reactions occur
Mitochondria: Where respiration takes place
Ribosomes: Where protein synthesis takes place

Plant only:

Cell wall: Protects the cell
Chlorplasts: Contain chlorophyll used in photosynthesis
Vacoule: Stores cell sap

Question 7

Q

SB1c - What are the adaptations of the following cells:

Egg cell
Sperm cell
Cilliated epithelial cell
Cells lining the small intestine

Answer

A

Egg cell: Has a haploid nucleus, with a special cell membrane to allow only one sperm cell in and many nutrients in its cytoplasm
Sperm cell: Has an acrosome with enzymes to penetrate the egg cell with lots of mitochondria and a tail to swim
Ciliated epithelial cell: Lined with cilia and packed with mitochondria this allows the cell to have a ‘wavy’ movement to move an egg along
Microvilli: The cells lining the small intestine have small folds called microvilli which increase its surface area making absroption easier

Question 8

Q

SB1c - What is the function of a gamete?

Answer

A

Gametes are sex cells used in reproduction.
Examples are sperm and egg cells.

Question 9

Q

SB1d - What are the functions of structures in bacteria?

Answer

A

Single loop of DNA: Contains chromosomes and genes
Plasmids: Contain additional genes
Flagellum: Used to propel the bacteria
Flexible cell wall: for support
Cytoplasm: Containing prokaryotic ribosomes

Question 10

Q

SB1d - What are the differences between eukaryotic and prokaryotic cells?

Answer

A

Eukaryotic cells have a nucleus, prokaryotic cells do not

_{^{Jefferson has beliefs; burr has none}}

Question 11

Q

SB1e - What are enzymes and what are they made up of made up of?

Answer

A

Enzymes are biological catalysts that speed up reactions.
They break down protiens/substances called substrates.
Enzymes are made up of amino acids and they are proteins.
They are needed to speed up reactions we cannot live without

Question 12

Q

SB1g - How do enzymes work?

Answer

A

Each type of enzyme is in a shape that is specific to their substrate.
They can be re-used as long as they don’t become denatured
The idea that an enzyme bonds with a specific substrate is the lock-and-key mechanism

Question 13

Q

SB1e - What is a polymer?

Answer

A

A polymer is a chain of single substances called monomers.
The formation of a polymer is called synthesis.
Enzymes often break down polymers into monomers

Question 14

Q

SB1e - What are the three main nutrient based enzymes? Where are they found and what do they do?

Answer

A

Amylase: Found in saliva. breaks down starch into Sugar
Protease: Found in the stomach, breaks down proteins into amino acids
Lipase: Found in the stomach and pancreas, breaks down lipids into fatty acids and glycerol

Question 15

Q

SB1f CP - What tests are used to identify main components in food?

Answer

A

Starch: Iodine will go from yellow to blue-black
Proteins: Biruet’s solution will go from blue to purple
Lipids: Add ethanol and shake and a white emulsion-fatty layer - should form is it is present
Sugars: Benedict’s solution while heating which will turn anywhere from green to yellow to red, indicating how much sugar is present This is a semi-quantitative test. It mostly gives non-measurable values

Question 16

Q

SB1f- How can we use a calorimeter?

Answer

A

Burn a known mass of the food under a boiling tube filled with a known volume of water.
Calculate the change in temperature of the water.

Question 17

Q

SB1g - What is the function of the active site of an enzyme?

Answer

A

The active site is unique to an enzyme so each enzyme can only work on specific substrates and is where the substrate must be for anything to take place

Question 18

Q

SB1g- How are enzymes denatured?

Answer

A

Changes in pH and temperature can affect the shape of an enzymes active site.
When temperatures are too high/ pH is too far from optimum, enzymes can no longer accept substrates
When the active site can no longer accept any substrates, it is said to have become denatured.

Question 19

Q

SB1h - How is enzyme activity affected by temperature, pH and substrate concentration?

Answer

A

Temperature: As temperature increases, molecules move faster and so more successful collisions occur between enzymes and substrates so the rate of reaction increases. Until the temperature causes the enzyme to change shape causing it to denature
pH: An enzyme has an optimum pH where it works best. The furhter away from this, it will get slower till it becomes denatured
Substrate concentration: Increasing this will increase the rate of reaction as there are more collisions occurring. This is until a point when all enzymes are full up and rate of reaction will no longer increase

Question 20

Q

SB1i - What is the difference between diffusion and osmosis?

Answer

A

Diffusion is when particles move from a high concentration to a low concentration.
In osmosis this is the same principal except across a semi permeable membrane where a solvent moves from and area of high concentration to an area of low concentration

Question 21

Q

SB1i - How do cells transport substances against a concentration gradient?

Answer

A

Using active transport which is carried out by transporter proteins on membranes which require energy to run.
They take in the molecule and then change shape to move it through the membrane.
This works against the concentration gradient.

Question 22

Q

SB1i CP - Describe the method you would use to investigate osmosis through potatoes

Answer

A

Cut discs of raw potato, blot them dry, and measure their mass.
Put each disc in a sugar (or salt) solution of different concentrations
After 30 minutes, measure the mass of each disc again.
Subtract the initial mass from the final mass of each disc.
Divide this number by the initial mass and then multiply by 100 to give a percentage change in mass.
The highest change in mass means there was a greatest difference between water concentration as osmosis works with the concentration gradient This can work with any semi-permeable membrane

Question 23

Q

SB2a - When a regular human body cell divides, what is this process called, and how does it occur?

Answer

A

Mitosis - (Imaginary pickpockets meet around the city)

Interphase
- Copies of the chromosomes are formed in the nucleus
Prophase
- The nucleus starts to break up and spindle fibres appear.
Metaphase
- The chromosomes are lined up on the spindle fibre across the middle of the cell
Anaphase
- The chromosome copies are separated and moved to either side of the cell
Telophase
- A membrane forms around each set of chromosomes to from a nuclei
Cytokeniesis
- Cell surface membrane forms separating the two cells (In plants, a cell wall is also formed)
The cycle repeats

Question 24

Q

SB2a - What are the products of mitosis called?

Answer

A

Daughter Cells

Question 25

Q

SB2a - What type of organisms do not require mitosis to occur?

Answer

A

Unicellular organisms

Question 26

Q

SB2a - How many types of chromosones are in a human cell and what is it called when these are alone or paired up?

Answer

A

23 types of chromosomes.
When they are paired up to have 46 chromosomes this is a diploid cell and a haploid cell only has 23 chromosomes.
Gametes are haploid cells while all other cells in a human are diploid.

Question 27

Q

SB2a - How are tumors formed?

Answer

A

When cells mutate, they can become cancer cells.
This means that they will divide even when they don’t require to divide.

Question 28

Q

SB2a - Why does asexual reproduction require mitosis?

Answer

A

As asexual reproduction only needs one parent, the offspring will have the same DNA as the parent.
As the offspring are clones and their chromosomes are identical, their cells are formed by mitosis.

Question 29

Q

SB2b - Define growth.

Answer

A

The increase in size as a result of an increase in size of or numbers (due to cell division) of cells.

Question 30

Q

SB2b - How is the growth of a baby monitored and how does this work?

Answer

A

Using a percentile growth curve:

This graph has many lines showing you how a babies conditions compare to the average.
The healthiest position would be at 50% as half of the population is above or below you.
Being above 98% or below 2% is reason for concern as only 2% of the population is above or below you.

Question 31

Q

SB2b - What is cell differentiaiton?

Answer

A

When a less specialised cell is changed to become a specialised one.

Question 32

Q

SB2b - How are red blood cells specialised for their purpose?

Answer

A

Biconcave shape means more surface area for oxygen diffusion.
No nucleus means more space for red haemoglobin molecules and carry more oxygen

Question 33

Q

SB2c - What are the meristems?

Answer

A

A group of cells near the end of each shoot that allow plants to continue growing throughout their lives.
They divide rapidly and the cells are elongated and differentiated.

Question 34

Q

SB2c - How are root hair cells specialised for their function?

Answer

A

Root hair cells have hair to increase their surface area to allow them to absorb water more effectively.
They also don’t contain chloroplasts (as they are underground and can’t photosynthesise)

Question 35

Q

SB2c - How are xylem cells specialised for their function?

Answer

A

They have thick walls containing lignin.
This causes the cells to die
As the cells die, the end walls connecting them break away, meaning the cells form a long tube
Along with the fact that they have no internal structure at all (nucleus, chloroplasts etc.) this makes it easier to transport water and minerals.

Question 36

Q

SB2c - What are the zones of differentiation elongation and cell division?

Answer

A

D: Where cells are specialised
E: Where cells are elongated (vertically extended)
CD: Where rapid mitosis occurs (Meristems)

Question 37

Q

SB2d - What is an embryonic stem cell?

Answer

A

A cell in an early stage embryo that is not specialised and can differentiate to form any type of specialised cell.

Question 38

Q

SB2d - Where can adult stem cells be found and how are they different to embryonic stem cells?

Answer

A

Adult stem cells can be found in most tissues including bone marrow but can only differentiate to cells in the tissue around them .

Question 39

Q

SB2d - How can stem cells be used to treat lukemia?

Answer

A

A patient’s bone marrow is destroyed using radiation
Adult stem cells are inserted into the patient
The stem cells will differentiate specialise and divide to form new blood cells and bone marrow

Question 40

Q

SB2d - What are the problems with using stem cells in medicine?

Answer

A

If stem cells continue to divide, it can cause a cancerous tumour to form
Stem cells of one person can be rejected by the immune system of another

Question 41

Q

SB2d - Why don’t plants have adult stem cells?

Answer

A

Their cells remain able to differentiate freely throughout their lives.

Question 42

Q

SB2e - What type of cells is the brain mostly made up of?

Question 43

Q

SB2e - What are the three major structures of the brain, and what are each of their functions?

Answer

A

Cerebral cortex: Main functions and control such as memories language etc.
Cerebellum: Controls balance and movement
Medulla oblongata: Controls heart and breathing rate

Question 44

Q

SB2e - How did Phineas Gage’s accident prove what the cerebral coretex is used for?

Answer

A

Phineas gage had a metal rod stuck inside his brain
It was through his cerebral cortex
He was still able to walk, but his personality changed
This shows that this part of the cerebral cortex controls emotions and personality but not movement or breathing/heart rate

Question 45

Q

SB2e - Why may musicians have larger/more developed cerebellums?

Answer

A

So can develop and have more control over their fine movements and timing coordination

Question 46

Q

SB2e - The medulla oblongata controls reflexes. What does this mean about its connections?

Answer

A

It connects the brain to the rest of the CNS

Question 47

Q

SB2f - During brain surgery, what may be don to investigate roles of the brain?

Answer

A

Probing with electricity (electrodes) means that doctors can control the activity of different parts of the brain

Question 48

Q

SB2f - How does a CT scan work?

Answer

A

A CT scan involves an x-ray beam moving in a circle around the head.
It produces images that are slices of the brain.
Computers can layer and build these up to produce an image

Question 49

Q

SB2f - How does a PET scan work?

Answer

A

Radioactive glucose is injected into the body.
More active cells take in more glucose.
The PET scan scans for where the most radioactivity is coming from showing the levels of activity in the brain.

Question 50

Q

SB2f - Why is spinal cord damage so dangerous?

Answer

A

Damage to the spinal cord can sever the connection between your brain and the rest of your body.
This can loose to the loss of control of limbs such as quadripalegia.

Question 51

Q

SB2f - Why does chemotherapy not always work for brain tumors?

Answer

A

Chemotherapy involves sending chemical substances through blood to actively kill tumours
The brain has a natural filter called the blood-brain barrier which blocks out foreign substances in the brain
Additionally, chemotherapy can harm healthy cells

Question 52

Q

SB2g - What makes up the nervous system?

Answer

A

The CNS (Central nervous system):
- The brain
- The spinal cord
Nerves

Question 53

Q

SB2g - How does your body communicate?

Answer

A

Using electrical signals called impulses

Question 54

Q

SB2g - What are sense organs?

Answer

A

Organs that contain receptor cells which will cause the body to have a response to a stimulus. e.g. eyes, ears etc.

Question 55

Q

SB2g - Describe the sturcture of a sensory neuron.

Answer

A

Dendrites receive the electrical impulses from the receptor
This is passed on through the dendron and the axon
Axon terminals at the other end allow the electrical impulse to be passed on
The cell body containing the nucleus is between the dendron and axon
The cell is covered in fatty layer called the myelin sheath
This insulates the cell meaning there are no electrical jumps to other cells speeding up neurotransmission

Question 56

Q

SB2h - Describe the structure of the eye.

Answer

A

There is a clear covering called the cornea covering the eye which refracts most of the light
Below this are the iris and the pupil
CIllary muscles alter the shape of the eye (constricting or dialating it)
A lens to fine tune the light refraction
At the back is the retina containing rods (detect light levels) and cones (detect colour. Don’t function well in dim light)
This is passed onto optic nerves which pass electrical impulses to the brain
Refracted light should meet at the retina

Question 57

Q

SB2h - What is myopia and hyperopia?

Answer

A

Myopia is short sightedness (Can see close):

This is when light focuses too early (before the retina)
The eyeball is too long.
This can be fixed with a diverging lens.

Hyperopia is long sightedness (Can see far):

This is when light hasn’t focused by the time it reaches the retina.
The eyeball is too short.
This can be fixed with a converging lens

Question 58

Q

SB2h - What is a cataract?

Answer

A

Protein build up in the lens can cause it to become cloudy, clouding your vision.
This can be corrected by replacing the lens with a plastic one

Question 59

Q

SB2h - What is colour-blindness?

Answer

A

When the cone cells in your eye don’t properly detect colour
The most common form of this is red-green colour blindness
This cannot be corrected

Question 60

Q

SB2i - Describe the reaction process (not reflex arc).

Answer

A

The receptor cells in your sensory organs respond to a stimulus
They send a neurotransmission which using neurones, travels to your brain
Your brain decides what action to take and sends a neurotransmission using neurones to send a message to an effector e.g. muscle contracting

Question 61

Q

SB2i - Describe the roles synapses play in the reflex arc. (include the three types of neurones)

Answer

A

The receptor passes on an impulse to the sensory neurone
The sensory neurone reaches a ‘junction’ called a synapse. It contains a tiny gap
Once it reaches here, a chemical (neurotransmitter) is released passing on the impulse to the relay neurone in the spinal cord
The relay neurone reaches another synapse where it releases more neurotransmitters to pass it on to a motor neurone
The motor neurone reaches the effector where it causes a response to take place (e.g. muscle contracting)

Question 62

Q

SB3a - What is the difference asexual and sexual reproduciton?

Answer

A

Sexual reproduction involves fertilisation of a female gamete by a male gamete (two organisms)
Asexual reproduction only requires one parent anf the offspring is genetically identical to their parent

Question 63

Q

SB3a - How may a plant such as a strawberry reproduce asexually?

Answer

A

By using specail stems called runners which grow out from the root of the plant.
These can also provide water and nutrients to the duaghter plant until it is well develpoed.

Question 64

Q

SB3a - What are the advantages and disadvantages of sexual reproduction?

Answer

A

Pros:

Creates variation meaning that a species is more likely to survive a disaster.
It also allows them to move to different envirnoments

Cons:

Time consuming from fertilisation to birth

Answer 64

A

Pros:

Very quick and takes up very little energy
No need to find a mate

Cons:

No variation meaning that if they are vulnerable to a disease there is a high risk of extinciton

Answer 65

A

Before: A zygote
After: An embryo

Answer 66

A

They are haploid rather than diploid meaning that they contain 1 set of 23 chromosones.

Answer 67

A

DNA is a molecule containing instructions for an organism. The DNA of an organism is its genome.
The human genome is made of many molecules each containing a chromosone.
DNA is used to code for and create protiens which are polymers.

Answer 68

A

Meiosis:

The gamete ‘making’ cell is diploid.
Once it has divided in the smae way as it would in mitosis, it divides once more without replicating the DNA producing haploid daughter cells.

Answer 69

A

A double helix structure with neucloetides.
Each nucleuotide contains a phosphate group and a sugar.
This forms a sugar phosphate backbone.
They also have bases which are complimentary and joined together by hydrogen bonds.
The bases are adenine guanine thymine and cytonsine with A being complimentary to T and C being complimentary to G.
The DNA forms a polymer because it is many nuceuotides joined together.

Answer 70

A

A/T form two hydrogen bonds while C/G form three hydrogen bonds.
This explains why each of them have pairs and A can’t bond with C for .

Answer 71

A

The order of bases form a gene.
Everyone has a slightly different order of bases (except identical twins) meaning that they all have different genesd.
Since DNA and genes are passed down along family, this information can be used to find out if people are related.

Answer 72

A

P: Polymer of amino acids
S: Polymer of glucose
C: Polymer of glucose

Answer 73

A

Thoroughly mash up some peas
Make a solution of salt water and detergent without making it soapy
The detergent will break down the cell surface membranes and membranes around the nucleus
Mix the mash into the solution
Place the beaker containing this mixture in a water bath at 60 degrees for 15 minutes
Pour some of the filtrate into a boiling tube and add two drops of the protease enzyme (to break down proteins)
Tilt the tube slightly and let some ice cold ethanol run down the side of the tube slowly
Leave for a few minutes. The ethanol will cause the DNA to precipitate

Answer 74

A

Transcription is the first stage of protien synthesis in which RNA is created inside the nucleus
RNA polymerase attaches to the non-coding binding site of the DNA
This causes the strands of DNA to unzip. One strand acts as a template.
Complemantary neucleotides attach to the template strand EXCEPT Instead of T attaching to A, Uracil attaches to A
The nucleotides join up to form a polymer of mRNA (RNA Polymerase)
The mRNA leaves the nucleus through nuclear pores

Answer 75

A

Translation is the second stage of protien synthesis and follows transcription
The mRNA attaches to ribocomes in the cytoplasm
The ribosome moves along the mRNA three bases at a time (a triplet of bases is called a codon)
At each codon, a complemantary tRNA molecule (that codes for a specific amino acid joins opposite to it.
Eventually, all the amino acids join up to from a polypeptide chain
This chain will then fold up to form a protein

Answer 76

A

A triplet of bases forms a codon.
Each codon codes for a different amino acid.
Different orders and collections of amino acids will form different protiens

Answer 77

A

A mutation is a change in the sequence of bases in a gene.
This can be caused by DNA not being copied properly or by enviromental factors (such as radiation)

Answer 78

A

In the non-coding site.
This is becuase this site decides when protiens and processes should/should not take place.
A mutation in this could lead to repeated rapid mitosis leading to a cancerous tumor, or a lack of a required protien.

Answer 79

A

After breeding tall and short plants together, he noticed that:

In the first generation of offspring, all the plants were tall
Despite having both tall parent plants, the second generation of offspring contained some plants that were short
This meant that characteristics inherited by offspring are not just a blend of parent’s characteristics
Also that there were ‘factors’ (now know as alleles) which affect this outcome and that one was dominant over the other

Answer 80

A

Homozygous: Both the allelles are the same
Heterozygous: Both the alleles are different

Answer 81

A

There aredominant alleles (represented by capital letters) and recessive alleles.
In any heterozygous case, the dominant allele will be visible in the phenotype.
The only way a recessive allele can be visibel is if both alleles present are recessive.

Answer 82

A

Punnet squares.

Answer 83

A

Females have XX chromosones;
Males have XY chromosones.
The mother has XX and the father has XY.
The means that if you draw a punnet square:

X Y

X XX XY

Thus the chances are 50/50

Answer 84

A

A pair of alleles inherited that are both dominant alleles.
For example, your blood group can be A, B, o or AB. in this case, o is recessive while A and B are both dominant and so if the AB alleles are inherited, they will both be present in the phenotype giving you AB blood type.

Answer 85

A

A Y chromosone is missing regions that are present on an X chromosone.

Answer 86

A

Since males have a Y chromosone which is missing regions, if a recessive allele is present in the X chromosone, but that area isn’t present in the Y chromosone, then the male will get the disease without having to have two recessive alleles.

Answer 87

A

If it is sex-linked, that area isn’t present on the Y chromosone (which he’d inherit from his father) and so only the mother’s genes matter.
Thus if it is a recessive disorder, the mother must have two of this and is guarenteed to pass this on to her son
Meaning her son will inherit the recessive allele and won’t be able to inherit a dominant allele to counter it.

Answer 88

A

The human genome project was a project that was carried out to try to map and identify all of the genes in a human.
Surprisingly, it revealed that despte all the visible variations, human all share around 99% of the same genes.
This was incredibly useful as it could be sued to identify genes that increase risk of cancer and other diseases/disorders.
It also shows which medication a person woul not be able to take making treatment more efficient and effective.

Answer 89

A

The differences in the characteristics of a population.

Answer 90

A

Environmental factors: Effects from your surroundings. e.g. water and light content will affect plant growth
Genetic factors: Effects from your alleles and mutations. e.g, natural hair colour is based off the alleles you inherit form your parents

Answer 91

A

Your capacity to grow is based off the alleles you inherit form your parents and increase the chance of you being tall/short.
However your diet will alaos affect your growth and so it is affected by genetic and environmental factors.

Answer 92

A

Discontinuous variation is variation in something that has a limited amount of possible values (e.g. number of leaves)
Continuous variation is variation in something that has possible values that could be measured to an infinite degree of accuracy (e.g leaf length)

Answer 93

A

It will be a normal distribution (bell-shaped) curve.
The most common value is in the middle of the whole range and the further away from this, the fewer individuals have this value.

Answer 94

A

Fossil remains
Stone tools

Answer 95

A

Fossil remains of humans can show us the bone structure of previous species
It also shows how the size of (volume) the skulls, increased over time, suggesting that the size of the brain increased aswell
The fossils are dated by the layers under the surface that they are

Answer 96

A

Stone tools show us what previous species of humans did and what they required tools for
We can see that over time, they become more sophisticated, going from skining animals/cutting up meat to decorations
Stone tools are dated by the rock that they are found in.

Answer 97

A

Not all organisms are fossilised.
Any organisms made of soft tissue and any soft tissue in organisms are unlikely to fossilise meaning that there are gaps in the records

Answer 98

A

Adripithecus (Ardi)
Australopithecus (Lucy)
Homo habilis
Homo erectus
Homo sapiens

Increasing skull volume over time

Answer 99

A

The characteristics of different individuals ina species differ due to genetic variation
A change in an environmental factor leads to increase in competition between organisms
The individuals with varitions that make them adapted to the change, means that they are better at coping and are more likely to survive (survival of the fittest)
The survivors will carry this gene that allowed them to cope and once they reproduce, are more likely to pass this onto the next generation
Over further generations, this gene will become more prominent in the population

Answer 100

A

The population of bacteria have variation in their resistance to antibiotics.
The course of antibiotics kill most of the bacteria
Before the course is finished, the only remaining bacteria are the most resistant
If the course isn’t completed, the remaining (more resistant) bacteria will reproduce,
This will produce another generation of highly resistant bacteria which the antibiotic will be less effective against

Answer 101

A

After visiting the galapagos islands and seeing differences in the mockingirds of different islands he wondered if spcies changed how they look based on their surroundings
After reading an essay by Thomas Malthus, he came to the conclusion organisms produce more offspring than could survive and so only the best suited survive
Wallace wrote a letter to him saying he came to the same conclusion
They both worked together and Darwin summarised their ideas in a book claled ‘on the origin of species’

Answer 102

A

The pentadactly limb is a limb that has 5 main bone structures and this is visible in many organisms from humans to bats to dolphins.
As we all have the same 5 bone base structure, this suggests that we all have a common ancestor.
However the layout of these 5 bones changed depending on the surroundings and conditions of a species.

Answer 103

A

(Domain)
Kingdom
Phylum
Class
Order
Family
Genus
Species

Answer 104

A

Name of genus then the name of the species

Answer 105

A

Animalae: Multicellular. Nuclei are present but no cell walls
Plantae: Multicellular. Nuclei, chloroplasts and (cellulose) cell walls are present
Fungi: Multicellular (apart form yeast). live on dead matter. Nuclei and (chitin) cell walls are present.
Protists: Mostly unicellular. Nuclei and cell walls present
Prokaryotes: Unicellular. No nucleus, flexible cell walls

Answer 106

A

They will have increasingly similar characteristics and genes.

Answer 107

A

Bacteria: (Cells with no nucleus; containing unused sections of DNA)
Archaea: (Cells with no nucleus or unused sections of genes)
Eukarya: (Cells with a nucleus and no unused sections of genes)

Answer 108

A

Disease resistance
Increased yield
Coping with certain conditions
Fast growth
Flavour

Answer 109

A

Firstly, out of the population, you pick the two organisms that most strongly present your desired characteristic
Breed these two together
From the offspring choose the two that most strongly show this and repeat
After a couple of generations, almost all of the offspring will display the characteristic
This is selective breeding/artificial selection

Answer 110

A

The process of altering the genes of an organism in order to aquire certian desired characteristics.

Answer 111

A

The growing of cells or tissue in a liquid containing nutrients or a solid medium (e.g nutrient agar).
This forms a callus (bunch of unspecialised cells) which can be differentiated and inserted into the body

Answer 112

A

Differentiating cells
Producing clones of GMOs
Growing plants of very rare species to stop their extinction
Testing new medical treatment without any affects on life forms
Studying viruses as they require host cells to be alive

Answer 113

A

They both start out by taking a piece of a plant and sterelising it
If only a few cells are taken, they are placed on sterile nutrient medium to form a callus
They callus is treated with gormones so that the plantlets develop roots and shoots
The plantlets are sperated and continue to grow until they can be placed in soil/compost to grow OR
If a piece of the plant is taken, its placed in sterile nutrient medium to grow
Once it grows bigger, it will be treated with hormones and so on in the same way…

Answer 114

A

Animals may loose an allele thought this process.
This may be needed later on to help them survive/cope
All the animals become very similar and so any disease that affects one of them, affects all of them
Unethical as some animals liv ein conditions that aren’t comfortable (e.g chickens with a lot of meat can’t stand up)

Answer 115

A

Genes may ‘hop’ onto wild plants, making them resistant
Loose out on genes that may be required in the future
Very expensive
Some people think its bad for your health

Answer 116

A

The insulin gene is to be inserted into the bacteria
Once you’ve extracted the DNA containing coding for insulin, use restriction enzymes to cut out the required section of DNA
Extract your bacteria’s plasmid, (which will act as a vector) and cut out a section using the same restriction enzymes
As you’ve used the same restriction enzymes, it will leave sticky ends (that are complementary to that of the insulin section of DNA)
As they are complementary, they will fit together, use ligase enzymes to join the insulin DNA to the plasmid forming hydrogen bonds
Re-insert the plasmid (which now has recombinant DNA) into the bacteria and let it reproduce.
As bacteris reproduce fast, you will soon have enoguh bacteria to efficiently extract insulin

Answer 117

A

It only affects insects that chew it meaning it targets pests specifically
Higher yield
Less money spent on insecticides

Answer 118

A

Insects such as aphids which suck up sap aren’t affected
Insects can develop resistance to the toxin
GM crops that produce the Bt toxin are expensive

Answer 119

A

When organisms are used to control pests.

Answer 120

A

Too much fertiliser usage means that its possible not all will be absorbed by the crops
Some could flow into water sources
This leads to eutrophication
And can poison animals/humans that drink from here

Answer 121

A

Physical well-being: Being free from disease, getting regular excersize, limiting harmful substance etc.
Mental well-being: How you feel about yourself
Social well-being: How well you get along with others
M̶i̶n̶e̶c̶r̶a̶f̶t̶ ̶h̶e̶a̶l̶t̶h̶:̶ ̶R̶e̶g̶e̶n̶e̶r̶a̶t̶e̶s̶ ̶o̶v̶e̶r̶ ̶t̶i̶m̶e̶

Answer 122

A

Communicable:

Caused by pathogens (microorganisms athat cause disease)
Can be spread between people

Non-communicable:

Caused by problems in the body and by lifestyle choices
Cannot be spread between people

Answer 123

A

One disease damages the immune system, making it easier for other pathogens to cause disease
A disease can damage the body’s natural physical and chemical defences making it easier for pathogens to get in
A disease can stop an organ from functioning correctly, meaning other diseases are mroe likely to occur

Answer 124

A

A lack or excess of a specific nutrient in the body

Answer 125

A

Kwashiorkor: enlarged belly, small muscles, failure to grow properly
Scurvy: Swelling/bleeding gums, muscle/ joint pains and tiredness
Rickets/Osteomalacia: Soft bones/cruved leg bones
Anaemia: Less and smaller red blood cells, tiredness

Answer 126

A

It’s considered a drug because it changes the way in which the body works
It can lead to liver cirrhosis which is a disease where the liver doesn’t function properly

Answer 127

A

Obese people are more likely to have more body fat. More body fat increases risk of CVD

Answer 128

A

Cardiovascular disease is a result of the circulatory system functioning poorly and can lead to many side effects including high blood pressure, heart pains and even heart attacks

Answer 129

A

A measure of weight relative to height calculated by mass ÷ height².
Its good at being a a measurement and comparison between people helping identify if they’re over/underweight or obese etc.
However it doesn’t take into account varying muscle and bone mass and so isn’t always an accurate way of assesing risk.

Answer 130

A

Tabacco from smoking will damage artery linings.
Fat (or plaque) can build up in the artery wall making the artery narrow.
This will increase blood pressure
Eventually, the fat will block the whole artery
White blood cells will form a wall around this causing a clot leading to a heart attack or stroke

Answer 131

A

A stent is a small mesh inserted into the artery on a delfated balloon.
Once in place, the balloon is inflated and the stent expands widening the artery
The balloon is taken out but the stent stays in keeping the artery wide

Answer 132

A

Caused by vibrio cholera (bacteria). It’s hosts are animals/humans and it can lead to severe diarrhea and dehydration
Caused by mytobacterium tubercolosis (bacteria). It’s hosts are humans/animals. It damages lung tissue leading to coughing fever and tiredness
Caused by the fungus chalara and affects trees/plants. Lesions on trunks and leaves die earlier than usual

Answer 133

A

Caused by the plasmodium protist, it infects humans using moquitoes as a vector. Leads to fever weakness, sickness and lack of red blood/liver cells
Caused by the salmonella typhi bacteria and infecting animals/humans causing severe diarrhea and dehydration
Caused by the heliobacter pylori bacteria and infecting humans causing stomach ulcers

Answer 134

A

They don’t have a cellular structure and require hosts to survive

Answer 135

A

HIV attacks the white blood cells in your immune system making it weak.
Thus the immune system is inable to defend the body from secondary infections effectively

Answer 136

A

Attachment: The viral particle attache sitself to the host receptor cell
Entry: Nucelic acid of the viruc moves across the membrane into the cell
Replication: The virus uses the host’s DNA to replicate and synthesise new viral components
Assembly: The new viral components are assembled into new viruses
Release: Lysis of infected cell leads to release of fully assembled viral particles

Answer 137

A

Attachment: The viral particle attache sitself to the host receptor cell
The Viral nuclei acids are incorporated into the DNA
The cell continues to divide
Replication: The virus uses the host’s DNA to replicate and synthesise new viral components
Assembly: The new viral components are assembled into new viruses
Release: Lysis of infected cell leads to release of fully assembled viral particles

Answer 138

A

Waxy layer called the cuticle
Cell walls

Answer 139

A

Poisons (in foxgloves)
Natural insect repellents/alarm substances (Wild potatoes)

Answer 140

A

Barriers to prevent pathogens from infecting the body.
Physical barriers stop them getting in and chemical barriers stop them from being effective.

Answer 141

A

Skin
Mucus
Earwax
Cilliated cells
Lysozyme (in saliva and tears)
Hydrochloric acid in the stomach

Answer 142

A

Lysozyme is an enzyme screted by skin and in tears and saliva.
It is chemical defence that breaks down the cell walls of types of bacteria.

Answer 143

A

Phagocytes
Lymphocytes

Answer 144

A

They detect the pathogen and recognise it as a foriegn body.
They then ingest the pathogen and use enzymes to destroy it.

Answer 145

A

Lymphocytes have antibodies on their surface that are specific to the antigens present on certain pathogens
The lymphocyte with matching antibodies is activated and will attach to the pathogen and then divide making identical copies of itself
The lymphocytes secrete antibodies which attach to the antigens of the pathogen and destroy it
Some lymphocytes remain (Memory lymphocytes)

Answer 146

A

The primary response takes a long time between infection and rise in antibody numbers
The numbers of antibodies produced isn’t that high
The number of antibodies doesn’t return back to its original value but slightly higher instead
After the second infection, the secondary response is a lot quicker.
It also produces a lot more antibodies
This is because of the already active memory lymphocytes

Answer 147

A

The memory lymphocytes created after one infection have antibodies specific to the antigens of that particular pathogen and won’t work on any othe pathogens.

Answer 148

A

A vaccination injects inactive/weak pathogens of a disease.
Lymphocytes with antibodies to tackle these are activated and memory lymphocytes are created
This means that if that pathogen infects the person after, there will be memory lymphocytes to tackle it quiclkly
This increases the person’s immunity to this disease as it reduces the severity of the symptoms and the time taken till the infection is dealt with

Answer 149

A

If around 95% of the people around them are vaccinated there is a very low chance of them getting the disease.
This is because all the others either won’t get it or will get rid of it before coming in contact with them.
This is called herd immunity.

Answer 150

A

Keys
Distribution analysis
Diagnostic testing

Answer 151

A

A ‘map’ displaying the first infected plant and the location of all the other infected plants.
By using othe information such as wind direction, you can deduce how the disease has spread and figure out what the disease is.

Answer 152

A

Farmers comare visible symptoms on infected plants to pictures to try and deduce which disease the plant has

Answer 153

A

Farmers will send off a sample of the infected plant to a lab where they will run tests to work out what the pathogen is.
They may also send soil samples to test for nutrients and toxins.
This can be very expensive.

Answer 154

A

Substances that either kill or bacteria or inhibit their cell processes stopping them from growing/reproducing.

Answer 155

A

Because bacteria are constantly evolving and developing resistance to existing antibiotics.

Answer 156

A

Pre-clinical development:

Testing on animals and human tissue to look for side effects

Clinical development:

Phase 1:
- Small clinical trial to check for human side effects
Phase 2:
- Slightly larger sample size looking for the optimum dosage
Phase 3:
- Large clinical trial to test effectiveness. Placebo (decoy) also used to verify this.

Answer 157

A

Sterilising equipment before use
Lighting a flame nearby
Only opening the petir dish slightly
Using an autoclave
Cleaning down surfaces before use
Wearing gloves

Answer 158

A

Using aseptic technique, pour an agar plate, making sure that the bases is covered with a smooth layer of agar
Open a bottle of bacterial culture without putting it down and pass the neck through the flame of a bunsen burner
Take out a sterile pipette and without putting it down, draw some bacterial culture
Slightly open the lid of the petri dish and add some culture. Then place the pipette in disinfectant
Unwrap a steirle spreader, and open the lid of the petri dish slightly, and spread the culture around in a side to side motion.
Using a permanent marker, section out the bottom of the petri dish into four sections
Label one, the control
Using sterilised forceps dip three paper discs each into a different concentration of antibiotic solution, sterilising between
Place each disc ina section of the dish (not near the edge)
Leave for incubation
Measure clear spaces in each section

Answer 159

A

The length from the centre of the area where there hasn’t been bacterial growth to the edge of this section, is the radius of the clear space. The area is πr²

Answer 160

A

First, an antigen is injected into a mouse.
The mouse produces lymphocytes with antibodies to target this antigen
However, once a lymphocyte starts producing antibodies, it can no longer divide, and so a cancer cell is grown in culture medium
The cancer cell is fused with the lymphocyte creating a hybridoma cell whic can both continue to divide and produce lymphocytes

Answer 161

A

Monoclonal antibodies can be made to specifically target cancer cells.
This means that unlike in many other forms of cancer treatment, healthy cells won’t be harmed.

Answer 162

A

Pregnancy tests have two types of monclonal antibodies.
One detects hormones that are always found in urine to confirm that its working.
The other detects a hormone only only produced after pregnancy

Answer 163

A

The monoclonal antibodies are made to target cancer cells.
They are also made radioactive.
Once inserted in the body, they will go to where the tumor is.
The radiation given off from the antibodies which help show a PET scanner where the tumors are located.

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