Biology- B1

Diet and Exercise

The different types of nutrients are:

  • Carbohydrates (potatoes, pastas, bread)- source of energy 
  • Fats (butter, oils, butter)- makes cell membranes, insulate our body 
  • Protiens (meat, fish, eggs)- growth, repair and building cells.
  • Water- chemical reactions take place 
  • Fibre (grains and nuts)- prevent constipation
  • Vitamins & Minerals (fruit and veg)- essential nutrients

Imbalanced diet- you can become malnourished:

  • overweight- diabetes, high cholestreal 
  • underweight- ricketts, scurvy

Metabolism- the rate at which chemical ractions take place.
Metabolism is affect by the amount of excercise you do and your muscle:fat ratio

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Defending the Body

Pathogens- harmful microorganisms which cause diseases:

  • Bacteria (cholera, typhoid)- multiply rapidly and produce harmful toxins
  • Viruses (measles, rubella)- reproduce inside host cells and damage them

White Blood Cells- Lymphocytes and Phagocytes

  • Phagocytes- ingest the pathogen and destroy them
  • Lymphocytes- produce antibodies to latch onto the pathogen's antigen and destroy them
  • Produce antitoxins which counteract the pathogen's toxins

Vaccines inject dead or weakened versions of the pathogen into our body which then get destroyed by White Blood Cells which produce antibodies for the pathogen. If our body then gets actually infected by the fully-strengthed pathogen, our body has the correct antibody ready.

Hygeine- Ignaz Semmelweiss discovered that to reduce infection you simply stay clean and wash- his idea was ignored because pathogens had not been discovered.

Antibiotics- Alexander Fleming discovered Penicillin (1928) by seeing that bacteria had been damaged by naturally occuring Penicillin mould. Since then, antibiotics have been produced. However, some bacterium have become resistent to antibiotics (MRSA)

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The Nervous System

Receptors- specialised cells that detect stimuli (changes in environment)-

  • Eyes- detect light
  • Ears- detect sound and position of the head
  • Tongue- detects chemicals in food
  • Nose- detects chemical in air
  • Skin- detects pressure, pain and temperature

 Central Nervous System (CNS)-spinal cord and brain
When a receptor is stimulated it sends a signal (neurone) to the brain and then coordinates a response. 

Neurones- cells that carry information as electrical signals

  • Sensory- carry respones from receptor to CNS
  • Relay- carry responses from a part of the CNS to another
  • Motor- carry response from CNS to effector

Synapse- gap between two neurones which change the electrical impulse into a chemical and back again.

Reflex- a very quick response that does not involve the brain.
Sequence: stimulus → receptor → sensory neurone → relay neurone → motor neurone → effector (carries out response)


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Control in the Human Body

Homeostasis- the maintenance of a constant internal environment-

  • Ions (salts)- controlled by passing urine (orange- not enough ions, clear-enough)
  • Temperature- controlled by enzymes (hot-sweat, cold-shiver)
  • Blood Sugar- controlled by the pancreas (production of insulin)

Hormones- chemicals secreted by glands in the body-

  • Thyroid gland-  controls metabolic rate
  • Pancreas- produces insulin
  • Ovary- produces oestrogen
  • Adrenal glands- produces adrenalin

Hormones in the menstrual cycle-
1) Follicle Stimulating Hormone (FSH)- causes egg to mature and stimulates the ovaries to produce oestrogen
2) Oestrogen-  Stops FSH being produced so only 1 egg matures, stimulates the pituitary gland to release LH.
3) Luteinizing Hormone (LH)-  releases mature egg from ovary (ovulation)

Oral Contraceptives- The Pill (inhibits the production of FSH so an egg can't mature)
Fertility Treatments- IVF (uses FSH to mature multiple eggs- increase the chance of fertilisation)


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Control in Plants

Plant Responses (tropisms)-

  • Positive tropism- plant grows towards the stimuls
  • Negative tropism- plant grows away from the stimulus

Phototropism- light is the stimulus
Gravitropism- gravity is the stimuls

Auxins- hormones found in plants, they change the rate of enlongation-

  • cells in shoots grow more
  • cells in roots grown less

Phototropism- more auxins on the shaded side so the shoot bends towards the light.
Gravitropism-  in a root placed horizontally, there are more auxins on the bottom so it grows less and bends down.
                        In a shoot placed horizontally, there are more auxins on the bottom so it grows more and bends upwards.

Weed Killer- hormones makes weed grow too quickly so they die
Rooting Powder- growth hormones that make stem cuttings quickly devlop from roots. 

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Drugs- substances that change chemical processors in the body

Drugs need to be safe, stable and effective which means that new drugs have to be tested.

Developing New Drugs-
1) Tested on cells and organs to see if they are safe and effective.
2) If they pass this they are then tested on animlas to see if they are safe, effective and what the correct dosage is.
3) They are then tested on healthy volunteers to check for side effects.
4)Then, there is a double-blind trial (one group is given the new drug, the other a placebo, but neither doctor nor patient knows who has what) on the people suffering from the illness.
%) If the drug passes all these trials it is released and put under moderation.

Thalidomide (developed in 1950's)-  
It was intended as a sleeping pill, but was later found to be more effective curing morning sickness. However, it caused abnormal limb development of the fetuses and about 10000 babies had been affected by Thalidomide, and only around half survived.
It was banned, and more rigorous testing was introduced. 

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Drugs in the Body

Stimulants- Drugs that speed up processors in the body
Depressants- Drugs that slow down processors in the body 

Some drugs are addictive and if the drug isn't taken, the addict can suffer from withdrawal symptons because the brain has become used to the chemical changes and starts to crave them.

Perfoming Enhancing Drugs-

  • Anabolic Steroids- Increase muscle size, but can cause high blood pressure
  • Stimulants- Increase heart rate
  • Some of the drugs and banned by law, all are banned by sporting-bodies
  • There are many ethical problems facing these drugs

Claims about Drugs (Positive and Negative)-

  • Statins- prescibed drugs used to lower the risk of heart and circulatory disease. They are proven to lower cholesterol and lower the risk of heat disease. The results were competely reproducible.
  •  Cannabis- an illegal, gateway drug which has been investigated whether it can cause mental heath problems. The results vary and is open to interpretation so no-one is sure.
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Every organism has specific characteristics that allow it to sucessfully live in their habitat.

Competition (Habitats have limited resources so the organisms need to compete to survive)-

  • Animals- they compete for food, water, mates and space
  • Plants- they compete for water, space, sunlight and minerals

Cold Climate (Polar Bear adaptation)-

  • White fur as camoflauge
  • Thick layers of fat and fur for insulation
  • Small surface area:volume ratio to minimise heat loss
  • Greasy coat that sheds water after swimming
  • Large feet to distribute their weight and grip on ice

Hot Climate (Cacti adaptation)

  • Stems that can store water
  • Widespread root system so they can collect water over a large radius
  • Spines that protect the plant and have have a small surface area to minimise water loss

Extremophiles- organisms which can live in extreme conditions that would kill other animals.

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Environmental Change

Living factors- change in predator, food source or competitor
Non- living factors- temperature or rainfall 

Predators and Prey
If the prey poulation increases, so does the predator as they have more food. However as the predator population increases, the prey decreases as more are being eaten. Consequently, more predators die because they do not have enough food. 

Water Pollution Indicators-

  • Clean- Mayfly Larvae
  • Low pollution- Freshwater Shrimp
  • High pollution- Water Louse
  • Very High pollution- Rat-Tailed maggot, Sludgeworm

Air Pollution Indicators-

  • Clean- Bushy Lichens
  • Low pollution- Leafy Lichens
  • High Pollution- Crusty Lichen

You can measure environmental changes by measuring rainfall, population or temperature. 

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Energy in Biomass

Biomass- The mass of living material at each stage of the food chain.

Food chains show what eats what in a particular habitat-

  • Producers- Greens plants and algae
  • Primary Consumers- Eats plant material
  • Secondary Consumers- Eats animal material
  • Predators- Kill for food
  • Prey- Animals predators fed on

Energy in Biomass is transferred along food chains, but not all of it is transferred-

  • Some is lost by heat being released
  • Some is lot by waste materials, faeces 
  • Some of the material is not eaten, bones.

Pyramids of Biomass are charts, drawn to scale, which show the amount of biomass at each stage of the food chain.

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The Carbon Cycle

Decay- Materials from living things decay because they are digested by microorganisms (bacteria and funghi are the main decomposers).
It needs to be mo]ist, warm and oxygen available for decay to occur. 

The Carbon Cycle
The carbon cycle shows how carbon moves from the atmosphere, through various animals and plants, then back into the atmosphere again-

  • Removing Carbon Dioxide from the atmosphere- Photosynthesis
  • Returning Carbon Dioxide into the atmosphere- Respiration
  • Releasing Carbon Dioxide into the atmosphere- Burning fossil fuels
  • Passing Carbon from one organism to the next- When an animal eats a plant, carbon from the plant becomes part of the fats and proteins in the animal. Microorganisms and some animals feed on waste material from animals, and the remains of dead animals and plants. The carbon then becomes part of these microorganisms and detritus feeders.
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Why Organisms are Different

Offspring resemble their parents because they contain genetic information passed on to them by their parents.

Chromosomes and genes-
Chromosomes, found in the nucleus of a cell, contain genes. A gene is a section of DNA which determines our charcteristics.

Individuals of the same species look slightly different due to variation- affected by your inheritence, environment or both.

Inherited Variation-

  • Eye colour
  • Skin colour
  • Hair colour 

Environmental Variation-

  • Weight
  • Accent
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Genetic Variation and Control

  • Sexual Reproduction- Requires 2 sex cells (gametes) to fuse (fertilise), in humans- sperm and ova. This results in variation because the gentic information is split in half.
  • Asexual Reproduction- Only one parent is needed and the the offspring is genetically identical to the parent (clone).

Artificial Cloning-

  • Cuttings (Plants)- A cutting is taken from a plant and is given plant hormones (auxins) which encourage it to grow
  • Adult Cell Cloning (Animals)- 
    1) The nucleus is removed from an unfertilised egg cell and discarded
    2) The nucleus is removed from an adult body cell and injected into the egg cell
    3) An electric shock is applied to make the egg cell begin to divide to form an embryo
    4) The embryo is inserted into the womb of an adult female
    5) The embryo continues to grow and develop, and then a clone is born.

Genetic Modification-
Genetic Engineering changes genes. For example, the genes in bacteria are being changed so they can produce insulin-
1) Enzymes cut out the human gene for producing insulin.
2) Enzymes cut out an un-needed section from a bacteria plasmid (DNA)
3) Insert insulin gene into the empty space on the plasmid
4) Bacteria reproduce and their off-spring too have the insulin producing gene. 

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Evolution- The idea that complex life forms evolved from simple life forms over billions of years.

Charles Darwin's Theory (Natural Selection)-

  • Individuals in a species show a wide range of variation
  • This variation is because of differences in their genes
  • Individuals with characteristics most suited to the environment are more likely to survive and reproduce (Survival of the Fittest)
  • The genes that allow these individuals to be successful are passed to their offspring.
  • Controversial idea as genes were a complex idea and it was anti-creationist.

Jean-Baptiste Lamarck's Theory-

  • A characteristic which is used more and more by an organism becomes bigger/stronger, and one that is not used eventually disappears.
  • Any feature of an organism that is improved through use is passed to its offspring.

Classification- Grouping species according to their similarities and differences.
(Kingdom, Phylum, Class, Order, Family, Genus, Species)
It is used to identify new species, group species and view similarities.

Mutations- Change in genes

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