Paper 4 Higher Flashcards
How is carbon transferred between organisms in an ecosystem?
- carbon passed up the chain when animals eat plants and other animals
- and when microorganisms break down dead organisms
Describe the role of respiration in the carbon cycle
When organisms respire, carbon is returned to the atmosphere as carbon dioxide
Explain how microorganisms are involved in cycling materials through an ecosystem
- microorganisms (bacteria and fungi) break down dead organisms and the waste products of living organisms…
- which returns elements to the soil or air
- microorganisms also respire, which returns CO2 to the atmosphere
Why is it important that carbon is being constantly recycled in an ecosystem?
- Limited carbon in the world
- So it must be constantly recycled so there is enough for all the organisms in an ecosystem
- It’s an important element in the materials living things are made from
What is nitrogen fixation?
The process of turning nitrogen gas from the air into nitrogen compounds in the soil which plants can use
What type of bacteria turn ammonium ions into nitrates?
Nitrifying bacteria
Why can clouds form as warm air rises?
Water vapour in the air is carried upwards. When it gets higher up, it cools and condenses to form clouds.
Why do crops grow poorly on the same soil after years?
- crops remove nitrogen from soil as they grow
- they’re harvested before they die
- so decomposers and nitrifying bacteria can’t break down the nitrogen containing compounds
- so the nitrogen content of the soil falls
Apart from bacteria, name one other type of organism involved in decomposition
Fungi
How does drying food help to preserve it for longer?
Drying food removes the water that microorganisms need to survive, so it slows down decomposition
What is an ecosystem?
A community of organisms along with all the non-living (abiotic) conditions
What do plants need from their environment?
Light, space, water and minerals
What is the difference between a population and a community?
A population includes all the organisms of one species in a habitat, whereas a community includes all the organisms of different species in a habitat.
Why would trees being planted closely together mean very few plants grow below these trees?
The light intensity at the forest floor is likely to be very low because the sunlight is being blocked out by the densely packed pine trees. Without enough light, plants can’t photosynthesise, so they are unlikely to grow on the forest floor.
There will be a high competition with trees for nutrients and water from the soil, so there might not be enough to allow the growth of other plants.
What does it mean if two populations are interdependent?
They depend on each other to survive
Trophic level
Stage in a food chain
What kind of variation is plant height?
Continuous- it varies within a range and there are no distinct categories
Mutation
A rare, random change in an organisms DNA that can be inherited
How do mutations introduce genetic variants into populations?
They change the sequence of bases in DNA, which produces a generic variant
Outline what happens during meiosis
- cell duplicates genetic information
- cell divides twice, halving the genetic material at each division
- this produces four genetically different haploid gametes
How are offspring produced using asexual reproduction?
A cell divides by mitosis, resulting in two diploid daughter cells.
Which chromosomes does each sperm cell contain?
Either X or Y
Classification
The organisation of living organisms into groups
Artificial classification system
Sorts organisms into groups depending on observable features
Natural classification system
Uses information about organisms common ancestors and common structural features to sort organisms into groups
Molecular phylogenetics
Looking at an organisms molecules e.g. DNA to help determine the evolutionary history between groups of organisms
Killing People Could OF Got Somewhere
Kingdom, Phylum, Class, Order, Family, Genus, Species
Evolution
The change in inherited characteristics of a population over time, through the process of natural selection
Explain the process of natural selection
Some genetic variants give rise to phenotypes that are better suited to a particular environment, so organisms with these characteristics have an advantageous phenotype.
These individuals have a better chance of surviving and reproducing successfully, so the genetic variants responsible for the useful characteristics are more likely to be passed on to the next generation. Over many generations, the useful characteristics become more common in the population.
Explain how Darwin and Wallace’s ideas about evolution have influenced how living organisms are classified by biologists today
- led to the understanding that all life changes through the process of evolution
- and all living organisms have descended from a common ancestor
- biologists now classify organisms based on evolutionary relationships
What is a pitfall trap? What type of organisms is it used to collect?
A steep-sided container that is sunk in a hole in the ground with a partly open top. It is used to collect ground insects.
What is a Quadrat?
A square frame enclosing a known area
Give one assumption made when estimating population sizes using capture-recapture
There has not been a change in the population size between the samples
The marking hasn’t affected the individuals chance of survival
How are humans reducing the amount of land and resources that are available to plants and animals?
Building, farming, dumping waste and quarrying for metal ores
Local and global biodiversity
Local- the number of a species in the local area
Global- the number of a species on the entire planet
Suggest how rivers and lakes can become polluted and how this would reduce biodiversity
- waste products e.g. toxic chemicals/fertilisers can get into rivers/lakes
- this pollution kills plants and animals
- therefore it reduces biodiversity
Pesticide
A form of chemical pest control which kills the pests that damage crops and other plants
How can the use of fertilisers improve crop yield?
They replace missing elements from the soil which are important for growth and life processes, or to provide more of them.
Disadvantage of using pesticide as a method of pest control
- Often poisonous to humans, so must be carefully used to keep pesticide in food below a safe level
- Can harm other wildlife that aren’t pests, like bees and ladybirds
- Can be passed up the food chain
Advantages of using biological control instead of chemical pesticides
- Doesn’t use chemicals so there is less pollution and chemicals don’t get passed along food chains
- Can have longer-lasting effects on pest population than chemical pesticides
- Less harmful to wildlife
What is hydroponics?
Where plants are grown in nutrient solutions rather than soil
Advantages of hydroponics
- Can control pests and diseases more effectively
- Be able to precisely control the nutrient levels to ensure maximum growth
Disadvantages of hydroponics
- high cost as you need lots of fertiliser
Genetic engineering
- changing an organisms genome…
- by moving genes for desirable characteristics…
- from one organism it another
How to insert a useful human gene into bacteria
- use the same restriction enzyme to cut out the useful human DNA and the plasmid
- they will therefore have complementary sticky ends
- use ligase enzymes to join the two pieces of DNA together
- these plasmid vectors containing the new DNA are inserted into the host bacteria
How to test if genetic engineering is successful?
- insert a gene which codes for antibiotic resistance into the plasmid…
- at the same time as the gene for the desired characteristic
- grow the host bacteria on a special plate containing antibiotics
- only bacteria containing the marker gene will survive and reproduce….
- antibiotics will kill the rest
How would having HIV affect the likelihood of a person contracting tuberculosis and developing symptoms?
Tuberculosis bacteria are normally destroyed by the immune system before symptoms of the disease can develop. If they infect someone with HIV, the bacteria aren’t destroyed by the immune system so the disease progresses very rapidly.
Explain how HPV affects the likelihood of someone developing cervical cancer.
HPV infections can sometimes cause cell changes which result in the development of certain types of cancer. It’s thought that nearly all cervical cancer cases result from HPV infections.
Which plants are affected by crown gall disease?
Those growing in soil contaminated with the BACTERIA Agrobacterium tumefaciens
How can tobacco mosaic virus stunt plant growth?
The leaves of the plant may become mottled and discoloured. This means the plants can’t photosynthesise as well.
How to help control the spread of any crop diseases
- make sure infected crops don’t contact healthy crops
- chemical or biological control to kill pathogens
- destroy infected plants
Physical barriers that protect plants from pests and pathogens
Waxy cuticle and cell walls
Describe how some plants use chemicals as a defence against pathogens
Some plants use anti microbial chemicals to kill pathogens or inhibit their growth
Which unique molecules on the surface of pathogens trigger an immune response?
Antigens
How does phagocytosis help defend against pathogens?
Some white blood cells use phagocytosis to engulf and digest pathogens
What type of cells produce antitoxins? What do antitoxins do?
White blood cells- antitoxins counteract toxins produced by invading bacteria
What features of the respiratory tract help to protect it from pathogens? Are they set of a specific or non specific defence?
- respiratory tract is lined with mucus…
- which traps particles that could contain pathogens
- cilia which line the tract waft the mucus up to the back of the throat…
- where it can be swallowed
- non specific defence as its not produced in response to a particular pathogen
What are memory cells? How do they help to fight pathogens?
- a type of white blood cell which stay round in the blood after a pathogen has been fought off
- if person infected with the same pathogen again…
- white blood cells will rapidly produce the antibodies to help destroy it
Describe the role of antibodies when somebody is first infected with a pathogen
- specific antibodies are produced by white blood cells…
- to lock onto specific antigens on a pathogen
- so the pathogen can be found and destroyed
- the antibodies are rapidly multiplied and transported around the body to find all similar pathogens
What do antibiotics kill?
Bacteria
How would you sterilise an inoculating loop?
Pass it through a hot flame
Why is a drug tested on healthy volunteers during clinical testing?
To make sure the drug doesn’t have any harmful side effects
Why are tumour cells used to produce hybridomas?
They can be grown easily, because they divide a lot
What type of cell is fused with a tumour cell to produce a hybridoma?
Lymphocyte from a mouse (the type of white blood cell that produces antibodies)
What is attached to the test strip of a pregnancy testing stick before it is used?
Monoclonal antibodies to the hormone found in the urine of pregnant women
How are hybridomas used to produce monoclonal antibodies?
They are cloned to get lots of identical cells. These divide quickly to produce large amounts of the same antibodies, which are collected and purified.
What do antibodies bind to on the surface of cancer cells?
Tumour markers
Explain why radioactive elements used in cancer diagnosis bind to both healthy cells and cancer cells
- antibodies labelled with the element bind to the tumour markers on cancer cells
- picture of patients body is taken using a special camera that detects radioactivity
- anywhere there are cancer cells will show up as a bright spot
How can a diet high in saturated fat increase the chance of developing cardiovascular disease?
- saturated fat can increase the LDL cholesterol level in the blood
- this can cause fatty deposits to form in the arteries
- which can lead to coronary heart disease
By which process do cancer cells divide?
Mitosis
One risk factor that can lead to cirrohosis
Drinking too much alcohol
Risk factor that can lead to chronic bronchitis
Smoking
What is a stent and how does it reduce the risk of a heart attack?
A tube that is inserted inside an artery to keep the arteries open, making sure blood can pass through to the cardiac muscle, lowering the risk of a heart attack
What do statins do?
Reduce cholesterol in bloodstream
How can an understanding of the human genome help to develop new medicines?
- if scientists know which genes cause disease
- new medicines can be made to specifically target these diseases
- at a molecular level
An adaptation of white blood cells
They can change their shape to pass out of capillaries
How do painkillers affect phenotype and genotype?
Changes the phenotype only
What does it mean if there is more microorganisms in compost?
There will be more rapid decomposition
Factors affecting rate of germination
Temperature, light, pH, soil moisture
What is an antibody?
A protein molecule made by the immune system which binds to antigens
Describe how large amounts of antibodies can be made using monoclonal antibody techniques
- expose mice to antigen
- their body produces an immune response, producing antibodies to the specific antigen
- antibody producing lymphocyte cells are collected…
- and fused with myeloma cells from the bone marrow as they cannot survive alone
- fused cell is called a hybridoma cell
- hybridomas reproduce and form clones, called monoclonal antibodies
An example of ecotourism
Encouraging people to view animals in their natural environment
A feature of an artificial classification system
It uses a single difference or similarity between organisms
A statement that describes a preclinical trial
The drug is tested on healthy humans
Why would the minerals in soil run out?
If there are no microorganisms in the soil then no decay will take place.
How can plants and organisms in soil supply each other with the required gases?
- Plants release oxygen by photosynthesis
- Organisms in the soil release carbon dioxide by respiration
Describe how fungal infections can spread and how they enter plant leaves
They can spring by the wind through fungal spores. They enter leaves through the stomata.
Example of a fungal disease
Barley powdery mildew
Explain how growing barley on the fields one year, then wheat the next year can protect the crops.
- the spores left by the fungus growing on the barley cannot infect the wheat
- after two years, there will be less spores
They each grow barley in one of their fields. Each farmer sprays a different fungicide on their field. They then compare the crop yield in the two different fields. How could you improve the farmers’ experiment?
Use the same field and divide it in two because different fields may have different soil quality with different levels of minerals.
Describe how antigens are usually made by the human body
They’re made by white blood cells/lymphocytes when antigens are detected.
Explain why a placebo group is used in drugs testing
It’s a control which can act as a comparison to check the drug works. It eliminates any psychological effects.
Explain what is meant by dominant allele
A version of a gene which is always expressed when present
How can a mutation in non coding DNA change the activity of a cell?
The transcription of mRNA may be stopped
Why is there a range in the number of white blood cells?
People may be ill with an infection and therefore have produced more white blood cells to destroy the pathogen/produce antibodies.
