Bio Paper 1
What does mitosis produce?
2 genetically identical diploid daughter cells
List the stages of mitosis in the order they occur
Interphase, prophase, metaphase, anaphase, telophase and cytokynesis
Give 3 reasons mitosis takes place
- To produce new individuals by asexual reproduction
- For repair
- For growth
What happens in prophase?
The nuclear membrane breaks down
What happens in metaphase?
Chromosomes line up in the middle of the cell
What happens in anaphase?
The chromotids are pulled to opposite ends of the cell by spindle fibres
What happens in telophase and cytokynesis?
The cell splits into two
State the type of cell division which occurs after an egg cell is fertilised.
Mitosis
State the name of the plant tissue where mitosis occurs rapidly
- Tips of roots and shoots
- Meristems
Describe how plant cells increase in size following mitosis
Young cells have small vacuoles which absorb water by osmosis and enlarge
Name 2 types of specialised cells found in a) plants and b) animals
Plants- Xylem and Phloem
Animals - Red blood cells and egg cells
Explain what is meant by the term 'differenciate'
Cells become specialised to perform a particular function
Give one reason why cell differenciation is important in animals
Many different kinds of specialised cells can carry out different processes more effectively
Equation for percentage mass increase
difference in mass divided by original mass multiplied by 100
What is a stem cell?
An undifferenciated cell
Give the name of the plant tissue where stem cells are found
Meristems
Describe a function of adult stem cells
To replace damaged cells
Describe one difference between embryonic stem cell and a differenciated cell
Differenciated cells cannot divide where as embryonic stem cells can
Describe how embryonic stem cell could be used to treat Parkinson's disease.
Embryonic stem cells can be stimulated to produce nerve cells which can be transplanted into the patients brain to replace the dead cells that cause the disease
Give one benefit of using stem cells produced by a patient rather than embryonic stem cells to treat disease
- The embryo would not be destroyed from being removed which eliminates ethical concerns
Suggest a risk of using a patients own stem cells
Stem cells may not stop dividing and therefore cause cancer
Name 2 parts of the central nervous system
Brain and spinal cord
What is the function of the medulla oblongata?
To regulate the heart beat and breathing
What is the function of the cerebellum?
coordinates and controls precise and smooth movements
Describe 3 functions of the cerebral hemispheres
- Control voluntary movement
- Responsible for memory and learning
- Interpret sensory information
What happens when a spinal cord is cut?
The individual would become paralysed permanently from the site of the cut down since neurones cannot divide to replace/repair damaged neurones. Nerve impulses would not be able to travel to the parts of the body below the damage.
What is the function of the motor neurone?
Carries impulses from the central nervous system to effectors
What is the function of the relay neurone?
Carries impulses from one part of the central nervous system to another
What is the function of the sensory neurone?
Carries impulses to the central nervous system
Explain how the structure of a motor neurone is related to its function
The axon is long so it can carry impulses over long distances. The axon has a myelin sheath which is an electrical insulator which prevents impulses passing to neighbouring neurones. The nerve ending transmits impulses to effectors
Explain why the speed of transmission is longer in myelinated neurones than unmyelinated neurones.
Myelin sheath speeds up transmission because the impulse in transferred from one gap to another
Explain what effect it would have on the movement of an individual if the myelin sheath surrounding neurones in the spinal cord was destoryed - like in MS patients
Their movement would be impaired because the nerve impulses travelling to muscles would be slower
Define reflex actions.
Reflex actions are inate, rapid and automatic
State the name given to the junction between two neurones
Synapse
Explain what happens at the synapse.
1. Electrical nerve impulse reaches end of axon
2. Electrical impulse causes chemical neurotransitters to be released from vesticles in the neurone into the gap between the neurones.
3. Neurotransmitters diffuse across the gap and fits into receptors, causing a new electrical impulse in the next neurone
Describe the pathway taken by the nerve impulse in reflex arcs
1. Stimulus is detected by receptors
2. A nerve impulse travels along a sensory neurone
3. Then travels through a relay neurone in the central nervous system
4. Finally, it travels along a motor neurone to an effector
Explain the process of light entering the eye
1. Light enters the eye through the pupil
2. The cornea and the lens focus the light to form a sharp image on the retina.
3. The retina contains receptor cells called rods and cones that detect the light and form an image
4. The nerves in the retina convert the image into electrical signals that are sent to the brain along the optic nerve
Explain how the iris is adapted to its function
The iris changes its size by muscle contraction and relaxation. It does this to control how much light enters
Explain how the structures of the cornea and the lens are related to their function
- Both are transparent to let light in
- Both are curved to refract light
- The shape of the lens can become more or less curved
Describe what happens in the eye to allow it to focus on an object that is close
The ciliary muscles contract making the lens fatter so increasing the refraction causing the light to converge more
Describe what happens in the eye to allow it to focus on an object that is far away
The ciliary muscles relax making the lens thinner so decreasing the refraction causing the light to converge less
Define short-sightedness
Short-sighted people can focus on close objects but not distant ones
How can short-sightedness be resolved and why does this work?
Can be corrected using diverging lenses.
A diverging lens makes the light rays come together further away, so light is focused on the retina
Define long-sightedness
Long-sighted people can focus on distant objects but not near ones
How can long-sightedness be resolved and why does this work?
Can be corrected using converging lenses.
A converging lens brings the rays together so light is focused on the retina
Describe the effects of cataracts and how it can be corrected
They occur when the lens becomes cloudy, so light cannot pass through it properly. The person recieves a blurred image on the retina.
It can be corrected by replacing the cloudy lens with a clear artificial lens
State the type of cell in the retina that detects colour
cones
Describe the causes of red-green colour blindness
Either red or green cones are missing, and the person cannot distinguished between the colours red and green
Describe sexual reproduction
- Requires two parent cells (egg and sperm)
- Mixes genetic information from each parent
- Off-spring have a variety of characteristics from their different combinations of genes
Describe asexual reproduction
- No fusion of gametes - only one parent
- No mixing of genetic information
- All off-spring have the same characteristics as parent and each other
What does meiosis produce?
4 genetically different haploid daughter cells
What does haploid mean?
Half the number of chromosomes
Explain why the daughter cells produced by meiosis are not genetically identical
Because the daughter cells only contain half of the chromosomes from each parent so the daughter cells have different combinations of DNA
Describe the importance of the two types of cell division, mitosis and meiosis
Mitosis maintains the diploid number and produces cells that are identical to the parent cell. It is used for growth. Meiosis creates gametes that have half the number of chromosomes. Fertilisation restores the diploid number.
State the name used to describe all the DNA of an organism
Genome
Describe the difference between chromosomes, genes and DNA
- A chromosome is a long molecule of DNA packed with proteins.
- A gene is a section of DNA that codes for a specific protein.
- DNA is the molecule containing genetic information that forms part of the chromosomes
What is the name given to the shape of DNA?
A double helix
State the number of different bases present in DNA
4
Describe how the two strands of the DNA molecule are linked together
Weak hydrogen bonds between complementary bases
DNA is a polymer. Give one piece of evidence that DNA is a polymer
The structure consists of repeated nucleotides
What are the complementary bases to each base: A T G C
A complements T
T complements A
G complements C
C complements G
Describe how characteristics such as red hair could not be explained by 'blending' of the parents' characteristics
Red hair is either present or absent and a parent with red hair may not have red-haired children
What characteristics of pea plants did Gregor Mendel choose to work with? Why?
- Pea shape
- Pea colour
- Plant height
Because these could not be caused by blending because the characteristics were either present or absent
Explain why it was important for Mendel to use pure-bred seeds
So that he would know what factors they had because they always produce identical offspring when crossed with a pea of the same type
What conclusions did Mendel draw from his experiments?
- The gene for yellow seeds was dominant to the gene for green seeds because the first generation all produced yellow seeds
- The gene for round seeds was dominant over the gene for wrinkled seeds because the first generation all produced round seeds
State what is meant by alleles.
Different forms of the same gene that produce different variations of the characteristics
Explain the difference between the term 'genotype' and 'phenotype'
Genotype shows the alleles that are present in the individual whereas phenotype means the characteristics that are produced
Define heterozygous
different alleles of the same gene
Define homozygous
Genes have the same type of allele on both chromosomes
What genotype produces the female phenotype?
XX
What genotype produces the male phenotype?
XY
Describe what is meant by codominance
When a heterozygous individual shows the effect of both alleles
State the genotype of each blood group
A : IA IA or IA IO
B: IB IB or IB IO
AB: IA IB
O: IO IO
Decribe what is meant by a mutation
A change in the organism's DNA such as a change in a gene or sequence of bases
State the possible effects of a mutation on the phenotype of an organism
- No effect
- Small effect
- Significant effect
State what is meant by the human genome
The sequence of bases on all human chromosomes
State 2 disadvantages of decoding the human genome
- People at risk of some diseases may have to pay more for life insurance
- It may not be helpful to tell someone they are at risk from an incurable disease
State 2 advantages of decoding the human genome
- A person at risk from a genetic condition will be alerted
- Allows scientists to distinguish between different forms of disease
Describe the work of Darwin and Wallace in the development of the theory of evolution
Their theories involved natural selection and was based on their own work and work of other scientists
What impacts did the ideas of Darwin and Wallace have on modern biology?
- Helps us understand the relationships between different species
- Explains how new species evolve
- Explains how different species adapt to changes in their environment
Explain why, when an environment changes, some organisms within a species survive whereas others die.
There is variation within the species meaning members of the species that are most adapted will survive whereas those that are less adapted will die
Explain how stopping a course of antibiotics early can cause antibiotic resistance in bacteria
There is variation in the amount of antibiotic resistance in a ppopulation of bacteria meaning the most resistant will take the longest to die, so stopping early meants the most resistant will survive and reproduce so that the new population of bacteria will be resistant
Give 3 pieces of evidence towards human evolution
- length of arms
- brain size
- skull shape
Explain how scientists work out the ages of stone tools
- The ages of the rock layer where the tool was found can be dated by measuring the amount of radiation in the layers
Describe how the similarities between a human arm and a bat's wing suggest that humans and bats share a common ancestor
- Both have limbs with 5 fingers that have evolved and become adapted to different uses
Give two reasons why animals and plants are placed in separate kingdoms
-Plants are autotrophic feeder but animals are heterotrophic feeders.
-Plant cells have cell walls but animal cells do not.
Describe what is meant by selective breeding
Plants or animals with certain desirable characteristics are chosen to breed together so that their offspring will inherit these characteristics
Explain how pig breeders could use selective breeding to produce lean pigs with less body fat
Pigs with lower body fat are cross-bred and the offspring with lower body fat are also cross-bred. This is then repeated for many generations until a lean breed is produced consistently.
State 3 different characteristics that could be selected for in a crop suitable for use in any country
- A high yield so can feed more people
- Low fertiliser requirement so reduced cost
- Pest resistance so no need to apply pesticide which harms other organisms
Give a useful new characteristic that can be given to genetically modified crop plants
Resistance to herbicides
Describe how a genetically modified organism is produced
The desired gene from one species is cut out using enzymes. This gene is transferred to the new species' embryo cell and inserted into a chromosome. The embryo is then allowed to develop as normal.
What is tissue culture used for?
To produce clones of a plant
Give 2 reasons why plants may be cloned
- To make useful plant products such as anticancer drugs
- To produce disease-free plants
Give 2 advantages of using cell culture to test a new drug instead of testing it on labatory animals
- Cell culture is quicker
- Fewer ethical concerns
State 2 agricutural solutions that attempt to meet the need for food of a growing human population
- Use of artificial fertilisers
- Use of biological control
Give 1 advantage and 1 disadvantage of using artificial fertilisers
Advantage - Increases crop yields
Disadvantage - Can pollute waterways
What is meant by physical well-being?
Eating and sleeping well and being free from disease
What is meant by mental well-being?
Your physcological health such as how you feel about yourself
What is meant by social well-being?
Interaction with other people such as how well you get on with others
Give 2 qualities of a communicable disease and 3 examples
- Rapid variation in number of cases over time
- Cases are often localised
e.g. malaria, typhoid, chlorea
Give 2 qualities of a non-communicable disease and 3 examples
- Number of cases only changes gradually
- Cases may be more widely spread
e.g. cancer, heart disease, diabetes
How does HIV make it easier for other pathogens to infect the human body?
HIV causes damage to the immune system resulting in reduced immune response and overall immunity to pathogens
Explain how viruses cause disease
- The virus effects the body cell and takes over the body cell's DNA causing the cell to make toxins or damages the cell when new viruses are released
Describe 2 ways in which bacteria make us feel ill
Bacteria can release toxins and can invade and destroy body cells
What kind of pathogen causes Chalara ash dieback?
A fungus
Describe the effects of the pathogen on trees
- Leaf loss
- Bark damage
What type of pathogen causes Chlorea? Give a sign of infection too
Bacterium and watery faeces
What is the name of the disease which is caused by a bacterium and causes a persistent cough - sometimes coughing up blood?
Tuberculosis
What type of pathogen causes malaria? Give 2 signs of infection too
Protist
Fever & chills
What type of pathogen causes HIV? Give a sign of infection too
Virus
Mild flu-like symptoms at first
Give 2 ways in which we can reduce or prevent the spread of ebola
- Keep infected people isolated
- Wear full protective clothing while in close contact with infected people or dead bodies
How can we reduce the spread of pathogens in water?
In developed countries, water is treated to kill pathogens since good hygiene prevents their spread
Describe the role of the skin in protecting the body from infection
Acts as a physical barrier which stops microorganisms enetring the body
Describe one chemical defence against infection from what we eat or drink
Hydrochloric acid in the stomach kills pathogens
How do ciliated epthilial cells protect the lungs from infection?
The cilia on the surface of these cells move in a wave-like moton and this moves mucus and trapped pathogens out of the lungs towards the back of the throat where it is swallowed
Name the type of blood cell which produces antibodies
Lymphocytes
Describe how lymphocytes help protect the body by attacking pathogens
Pathogens have antigens on their surface. Lymphocytes are activated if they have antibodies that fit these substances. These cells then divide many times to produce clones and large amounts of antibodies which stick to the antigens and destroy the pathogen
State what is meant by a vaccine
A vaccine contains antigens from a pathogen that are inactive and unable to cause a disease
How do vaccines work?
The vaccine causes memory lymphocytes to be produced, so if the person is exposed to the disease these lymphocytes produce a secondary response which prevents an increase in the pathogen to a level that causes illness
Give 2 disadvantages of vaccination
Mild swelling
A mild form of the disease
What are antibiotics?
Medicines that kill or slow down growth of bacteria in the body
Why can antibiotics be used to treat bacterial infections?
Because they kill bacteria but do not affect human cells
Why must the workbench be wiped with disinfectant when handling cultures of microorganisms?
So that microorganisms on the bench do not contaminate the culture
Why is the petri dish not all the way sealed when handling cultures of miroorganisms?
To discourage growth of anaerobic bacteria which is likely to be pathogens
When investigating microbial cultures, why are there clear areas around each disc of the antibiotic?
Bacteria do not grow in these areas because the antibiotic kills them
Describe 2 stages of preclinical testing in the development of a new medicine
Testing in cells or tissues to see if the medicine can enter the cells and have the desired effect
Testing on animals to see if it has any harmful side effects
Describe the function of a large clinical trial in developing a new drug
Medicine is tested on people with the disease it will be used to treat so that the correct dose can be determined and to check for side effects in patients
Explain how alcohol causes liver disease
Ethanol is a drug that is toxic to cells. It is broken down by the liver and harms liver cells. Too much alcohol over a long period of time causes liver disease.
Babies who's mothers have smoked while pregnant have low birth weights. Why?
Because carbon monoxide in cigarette smoke reduces how much oxygen the blood can carry to the baby leading to low birth weight in babies
What is meant by a deficiency disease? Give an example
Too little of one or more nutrients in the diet e.g. anaemia
State two ways in which cardiovascular disease may be treated
- Lifestyle changes
- Surgery
State 2 pieces of advices a doctor might give to a patient with high blood pressure to help them make lifestyle changes
- Give up smoking
- More exercise
State 2 ways in which plants protect themselves from pests and pathogens using physical defences
Thick waxy cuticles
Spikes and thornes