Download Biology Unit-1 AQA Core revision-Summary

B1.1 Keeping Healthy
What are the 7 components of a balanced diet?
1. Carbohydrates
5. Minerals
2. Proteins
6. Water
3. Fats
7. Fibre
4. Vitamins
What are the uses of the three major food groups; carbohydrates, fats and protein?
Carbohydrates – slow release of energy
Fats – Energy store, insulation, cell membranes
Protein – growth and repair
What is metabolic rate?
The rate at which all the chemical reactions in the cells of the body are carried out.
How do the two pathogens listed above make us feel ill?
Bacteria – rapidly reproduce and release toxins
Viruses – replicating inside cells and damaging them
What did Semmelweiss recognise the importance of?
Hand-washing to reduce the spread of infectious diseases
How do microbes spread?
1. Droplets
2. Contaminated food/water
3. Skin contact
4. Insect bites
What factors affect metabolic rate?
1. Amount of physical activity you do – exercise
2. The proportion of muscle to fat in your body
3. Inherited factors
4. Gender
How does the body prevent pathogens from entering?
1. Skin barrier
2. Stomach acid
3. Mucus in the nose and trachea
4. Cilia in the nose and trachea
What else is influenced by inherited factors?
1. Cholesterol levels
2. Muscle to fat ratio
Which cells in the body defend against pathogens if they enter?
White blood cells
Name a deficiency disease caused by malnutrition? What can the body not control?
Type 2 diabetes – blood sugar levels
What are the three defence mechanisms they use?
1. Ingesting pathogens
3. Producing antitoxins
2. Producing specific antibodies
What is the fatty substance that is an essential component of cell membranes but
harmful levels of it can also lead to heart disease?
Cholesterol
What do painkillers do for an infectious disease?
Relieve the symptoms but do not kill the pathogen
What conditions can obesity lead to? (name 5)
Arthritis, type II diabetes, high blood pressure, heart attack, thrombosis
What can be used to treat bacterial infections?
Antibiotics
How can a person lose weight?
1. Eat less food, particularly fats
2. Exercise more
What can prevent viral infections?
Vaccination
What are pathogens? Name two
Microorganisms that can cause infectious diseases e.g. viruses and bacteria
Why can viral infections not be treated with the same drugs used for bacteria?
1. Virsuses live inside the cells/hidden from immune system
2. Drug would damage body cells
How does antibiotic resistance arise?
Overuse of antibiotics
Bacteria mutate
Antibiotics kill non-resistant strains/reduced competition
Resistant strains reproduce rapidly
What does MMR stand for?
Measles, Mumps, Rubella
How does immunisation stop reinfection?
White blood cells produce antibodies that are produced faster upon reinfection
What part of a vaccine stimulates an immune response?
Dead/weakened/inactive pathogen
How do you prepare a bacterial culture in a Petri dish?
Sterilise Petri dish and agar before use to kill unwanted bacteria
Pass inoculating loop through a flame to sterilie
Keep the lid of the Petri dish close as much as possible to prevent microbes from
the air entering
Use the loop to streak bacterium onto agar
Seal the lid onto the dish with tape
Incubate to allow growth of bacteria
How can the spread of a viral infection be reduced?
By vaccinating a large proportion of the population
B1.2 Nerves and Hormones
What are the 5 sense organs? What stimuli do they detect?
1. Eye - light
2. Ear – sound, change in position
3. Nose - smell
4. Tongue - taste
5. Skin – touch, pressure, pain, temperature
What does the nervous system do?
Carries electrical impulses along neurons, allowing you to react to your surroundings
and coordinate your behaviour
What route does an impulse take through the nervous system?
Stimulus receptor  sensory  relay neuron  motor neuron effector
neuron
in CNS
What is the effector? How does it respond to the impulse?
1. Muscle – contracts
2. Gland – secretes hormones
What is a reflex action?
A survival instinct – a very quick response to a stimulus
How are impulses passed on between neurons?
A chemical called a neurotransmitter, is released at the synapse between two neurons
What four conditions need to be controlled in the body?
1. Temperature
2. Blood sugar
3. Water content
4. Ion content
What is a hormone?
A chemical messenger to help control and coordinate processes in your body
How is a hormone transported to its target organs?
In the bloodstream
Name two organs that release hormones
1. Pituitary gland
2. Ovaries
What four hormones are involved in the menstrual cycle?
1. FSH
2. Oestrogen
3. Progesterone
4. LH
Describe how hormones control the menstrual cycle
FSH stimulates egg maturation and oestrogen production
Oestrogen inhibits FSH causes the lining of the uterus to develop
LH stimulates the release of an egg from the ovary
How do oral contraceptives work?
They contain hormones to inhibit FSH production so no eggs mature
Why are oestrogen only pills not used?
Too many side effects compared with progesterone only pills
What is IVF?
When FSH and LH are given to stimulate maturation of several eggs. Eggs and sperm
are fertilised outside of the body and embryos are implanted into the womb
IVF can cause multiple births, why should this be avoided?
Multiple births lead to low birth weight and cause possible harm to mother/fetus
What three environmental conditions are plants sensitive to?
1. Light
2. Moisture
3. Gravity
Sensitivity to light is called?
Phototropism
Sensitivity to gravity is called?
Geotropism
Which hormone controls plant growth and where is it produced?
Auxin – made in the tips of the shoots and roots
Why does a plant bend towards the light?
More auxin is produced on the dark side of the plant. The unequal distribution cause
more growth on the dark side
B1.3 The Use and Abuse of Drugs
Why do painkillers not cure infectious disease?
Because they don’t kill pathogens, they only treat the symptoms of the disease.
What is a drug?
A substance that affects the chemical processes in the body so that a person may
become dependent or addicted to it.
Why must a drug be trialled before it can be used on patients?
To test for
1. Toxicity/adverse side effect
2. Efficacy – see if drug works
3. Dosage – how much is needed
4. Interaction with other drugs
What can drugs be tested on in laboratory trials?
1. Cells
2. Tissues
3. Live animals
How can drugs be tested in clinical trials?
Healthy volunteers and/or patients.
What is a double-blind trial?
A trial where neither the patients nor the doctors know whether a placebo or the drug
has been administered until the trial is complete. Avoids bias
What is a placebo and why is it used?
A substance that doesn’t contain the drug, which is used as a control in a trial.
What are statins prescribed for?
Lowering cholesterol levels in the blood to reduce the risk of heart and circulatory
diseases
Name two legal recreational drugs?
1. Alcohol
2. Nicotine
What affect does cannabis have on the body?
Cannabis smoke contains chemicals which make cause mental illness e.g. depression
Name an illegal recreational drug
Cocaine, ecstasy, heroin
Compare the health impact of illegal vs legal drugs
Legal drugs have an overall greater impact on health than illegal drugs because far
more people use them
Athletes can enhance their performance by using stimulants or anabolic steroids.
What do each of these types of drug do?
Stimulant - boosts bodily functions such as heart rate
Anabolic steroids – stimulate muscle growth
What was thalidomide unsuccessfully used to treat? What is it used to treat now?
Morning sickness in pregnant women. Now used to treat leprosy and some cancers.
What is the placebo effect?
People feeling better simply because they expect to feel better if they take medicine
Other problems associated with drug abuse
Addiction
Withdrawal symptoms
Infected blood diseases from needle/syringe use e.g. HIV and hepatitis
Poverty
Crime
What is drug addiction?
When your body becomes dependent on a drug due to frequent use. The drug alters
your body chemistry in such a way that you cannot function normally without it.
What is involved in phase two of drugs testing?
Drug tested on healthy volunteers, beginning with a very low dose and gradually
increased until effective dose is found.
B1.4 Interdependence and Adaptation
What are adaptations?
Features that enable an organism to survive in the conditions they normally live in
How do animals adapt for survival in dry and artic environments?
1. Changes to surface area
2. Thickness of insulating coat
3. Amount of body fat
4. Camouflage
How do plants adapt to survive in dry environments?
1. Changes to surface area
2. Water-storage tissues
3. Extensive root systems
What are extremophiles?
Organisms that have adapted to live in extreme environments.
What three conditions are considered extreme?
1. High temperatures
2. High pressures
3. High concentrations of salt in water
How have animals and plants adapted to deter predators?
1. Camouflage
2. Thorns/prickles/horns
3. Long limbs/streamlining for speed
4. Poison/bad taste
5. Large ears/position of eyes
How is a polar bear adapted to its environment?
1. White camouflage
2. Thick layers of fat and fur for insulation
3. Small surface area to volume ratio to minimise heat loss
4. Large furry feet for grip and to spread weight across snow and ice
How does the hoverfly avoid predation?
Yellow and black to appear like a wasp – mimicry
Other than light, what do plants compete with each other for?
1. Space
2. Water
3. Nutrients
What do animals compete with each other for?
1. Territory
2. Mates
3. Food
List some living factors that result in environmental change
1. A new predator
2. Change in food source
3. Change in competitor
What non-living factors cause environmental change?
1. Temperature
2. Rainfall
Name an organism that acts as an indicator of air pollution and explain how
Lichens – air pollutants like sulphur dioxide can damage lichens and prevent them
from growing.
How are aquatic invertebrates an indicator of pollution?
Many cannot survive in polluted water so their presence or absence can indicate the
extent of water pollution.
How can environmental changes be measured?
1. Oxygen levels – oxygen probes in water
2. Temperature – digital thermometer
3. Rainfall – rain gauge (funnel in bottle, measuring cylinder)
How does deforestation affect living organisms?
1. Loss of habitat
2. Food reduction
3. More extreme temperatures
B1.5 Energy & Biomass in Food Chains/B1.6 Waste materials from plants and animals
What is biomass?
The mass of living material in an organism
What does a pyramid of biomass show?
How much energy is available at levels in a food chain
What is the main source of energy for most communities of living organisms?
Radiation from the Sun
How is energy lost?
1. Respiration - muscles contracting for movement
2. Heat
3. Waste – excretion
What are the conditions needed for decay?
1. Warm
2. Moist
3. Aerobic - oxygen
Why is temperature important in the decay process?
Enzyme activity slows down and stops if it’s too cold and enzymes denature if the
temperature is too high
In the carbon cycle, how is carbon dioxide released into the atmosphere?
1. When green plants and algae respire
2. When animals respire
3. When microorganisms respire
4. Through combustion of wood and fossil fuels
Describe the events in the carbon cycle
CO2 removed from atmosphere by green plants and algae
-
Carbon in CO2 is used to make carbohydrates, fats and proteins
-
Carbon transferred when plants are eaten by animals (etc. along the food chain)
-
When plants and animals respire, carbon is released as CO 2 into the atmosphere
-
Microorganisms decompose dead plants, algae and animals and break down
their waste products
o materials cycled as plant nutrients
-
Microorganisms respire, which releases CO2 into the atmosphere
-
Combustion of wood and fossil fuels releases carbon as CO 2 into the atmosphere
How do you calculate the % of energy transferred into green plants from sunlight?
How does the decay process recycle nutrients?
1. Living things remove material from the environment for processes such as growth.
2. Materials are returned to the environment either in waste materials or through
death and decay.
3. Microorganisms cause decay by releasing enzymes that break down the
compounds in the materials to be absorbed by their own cells
4. The decay process releases substances that plants need to grow
What are the main groups of decomposers?
Bacteria and fungi
What is the primary way in which carbon dioxide is absorbed from the atmosphere?
By green plants and algae for photosynthesis
2.4 x 104 x 100
4 x 106
B1.7 Genetic variation and its control
Where in a cell is the genetic material contained?
Nucleus – contains chromosomes which carry genes
What is sexual reproduction?
Fusion of male and female gametes (egg and sperm cells)
Why does sexual reproduction increase variation?
Mixture of genetic information/DNA from two parents
Why do different individuals have different characteristics?
Different genes control the development of different characteristics of an organism
What influences the different characteristics of different individuals?
1. Genetic - inherited genes
2. Environmental – conditions in which they have developed
Which type of reproduction produces identical offspring - clones?
Asexual reproduction
What environmental factors could influence plant characteristics?
Light
Rainfall
Temperature
Nutrients
Space
Describe the stages in adult cell cloning
1. Nucleus is removed from an unfertilised egg cell
2. Nucleus from an adult body cell is then inserted into the egg cell
3. Electric shock is given to cause the egg cell to divide to form embryo cells
4. Embryo is inserted into the womb of an adult female
Other than adult cell cloning, what other modern cloning techniques exist?
1. Embryo transplants
2. Tissue culture
How can humans grow plant clones?
By taking cuttings from older plants – quick and cheap method
How can scientists produce genetically modified organisms with desired characteristics?
1. Desired gene ‘cut out’ from DNA using enzymes from organism with desired
characteristics
2. Gene transferred to DNA of another organism at early stage of development
What are the advantages of genetically modifying crops?
1. Resistance to herbicides or insect attack – less effort for farmer
2. Increase yield
3. More economical/increased profits
What are the concerns associated with genetic modification?
1. Transfer of genes to other species
2. Damage to food chains
3. Harmful effect on human health
4. May out-compete non-GM organism
5. Resistance to insects could interfere with pollination
What human uses are there for genetic engineering?
Medication – bacteria used in insulin production
Possible cures for genetic disease
Name an organism that reproduces asexually
Bacteria
How is embryonic cloning carried out?
1. A developing embryo is removed from a pregnant animal
2. Unspecialised cells from the embryo are taken, separated and grown in the lab
3. The cells are then transplanted into host mothers
What are the advantages of sexual reproduction?
1. Increases variation
2. Increases chance of species survival in a changing environment
What are the advantages of asexual reproduction?
1. Large number of identical offspring
2. Guaranteed desired features
3. Quick
4. Economic
B1.8 Evolution
What scientific term describes a change in a gene?
Mutation
What does Darwin’s theory of evolution state?
That all species of living things have evolved from simple life forms that first developed
more than 3 billion years ago
Explain how natural selection occurs
There is a wide range of variation between organisms within species
The fittest (characteristic most suited to environment) are more likely to survive
And pass on their genes to the next generation
What was Lamarck’s theory of evolution?
Change is caused by the inheritance of acquired characteristics during a lifetime e.g. long
neck of the giraffe
Why was Darwin’s theory of evolution initially not accepted?
1. Challenged the theory of creationism i.e. that God made all living things
2. Not enough evidence at the time
3. Mechanism of inheritance and variation not known until after 50 years
What do evolutionary trees show us?
The relationships between organisms e.g. identifying a common ancestor