edexcel gcse core science, biology one (B1)

CLASSIFICATION AND NAMING
SPECIES
King Philip Came Over For Good Spaghetti

 All living things belong to one of the five groups called kingdoms:
- Animalia are multicellular; cell do not have chlorophyll or a cell
wall; they feed heterotrophically (find food from their environment)
- Plantae are multicellular; cells have chlorophyll and a cellulose
cell wall; they obtain food autotrophically (make food by
photosynthesis)
- Fungi are multicellular; cells do not have chlorophyll; they feed
saprophytically (on dead organic matter)
- Proctoctista are unicellular (except seaweed), with a distinct
nucleus.
- Prokaryotes (a.k.a bacteria) are unicellular, but without a distinct
nucleus. simple cell structure with no nucleus. Examples are cholera,
dysentery, tuberculosis
- Viruses do not belong to a kingdom because scientist cannot decide
weather they are living organisms as they are considered not alive.
Reproduce inside a host cell. Examples are influenza, mumps, measles
and AIDS.
• Species
A group of organisms with similar characteristics, which can
successfully interbreed to produce fertile young.

B1.2 VERTEBRATES AND
INVERTEBRATES
The way they
absorb oxygen!
-gills like fish
and young
amphibians?
-lungs like
mammals reptiles
and birds?
-through their
skin like adult
amphibians?
How do they reproduce / give birth?
-external fertilisation
-Internal fertilisation (inside body)
-Lays eggs; oviparous
-Gives birth to live young; viviparous e.g. mammals
Are they homoeothermic or
poikilothermic?
-homeotherm; body temperature kept
constant
-poikilotherm; body temperature varies
with surroundings

◊ Hybrids are neither one species not another , and show characteristics of both
parents.
◊ Hybrids are usually infertile but not always
◊ Many plant hybrids are fertile
◊ Being infertile means they are unlikely to have offspring of their own and
pass on their mix of characteristics.
◊ Not all organisms reproduce sexually (some produce asexually)
B1.3 SPECIES
◊ All organisms have a two-part
binomial name.
◊ Homo sapiens, Homo is our genus
name, sapiens is our species name.
◊ The binomial naming system is used
because it prevents confusion
◊ Binomial classification is
important because it enables
scientists to:
» Communicate information about
thousands of different species
» Recognise areas of great
biodiversity that should be targets
for conservation efforts.

◊ A ring of populations
encircles an area of
unsuitable habitat.
◊ At one location in
the ring of
populations, two
distinct forms
coexist without
interbreeding, and
hence are different
species.
◊ Around the rest of
the ring, the traits
of one of these
species change
gradually, through
intermediate
populations, into the
traits of the second
species
RING SPECIES
◊ Famous examples of ring species are;
◊ the herring and lesser black-
backed gulls in northern Europe
◊ and the Ensatina salamanders of
California.

◊ Differences in characteristics are called variation.
◊ There is variation within a species but much more between different
species.
◊ This variation within a species can make classification difficult.
B1.4 VARIATION
Accurate classification using
the binomial system allows
biologists to:
◊ Easily identify existing and
new species
◊ See how organisms are
related
◊ Identify areas of greater
and lesser biodiversity.
◊ Biodiversity is important
because we obtain many
products from living things
e.g. Food, medicine

B1.5 VARIATION
Different genes cause genetic
variation
◊ All plants and animals have
characteristics that are in some
way similar to their parents
◊ This is because an organism’s
characteristics are determined by
the genes inherited from their
parents .
◊ Most animals get some genes from
the mother and some from the
father.
◊ The combining of genes from two
parents causes genetic variation.
(no two of the species are
identical other than identical
twins)
◊ Some characteristics are
determined only by genes (e.g. A
plant’s flower colour)
◊ In animals these include: eye
colour, blood group, and inherited
disorders (e.g. Haemophilia or
cystic fibrosis )
Characteristics are also influenced by
the environment.
» Environmental variation is any
differences caused by the conditions
someone lives in.
» Most characteristics are due to
genes and the environment.
Variation can be either continuous or
discontinuous
 In continuous variation,
characteristics are spread over a
range of values. Height in humans is
an example
 Tongue rolling is an characteristic
that shows discontinuous variation.
There are no intermediates.

◊ All organisms are adapted to their surroundings – they have
variations in their characteristics that enables them to survive in
their habitats
B1.6 REASONS FOR VARIETY
◊ Polar bear adaptations
◊ If a characteristic shows continuous
variation and a large enough number
of individuals are measured, when
plotted we get a graph with a
particular shape.
◊ This shape is called a normal
distribution curve (a.k.a bell
curve.)
◊ It shows that most individuals within
the middle part of the range in
variation, and there are fewer
individuals with measurements at the
extremes of the range.

◊ Charles Darwin was the first person to propose how
evolution takes place through natural selection.
◊ He described his ideas in a book titles On the
Origin of Species, published in 1859.
B1.7 EVOLUTIONIdeas central to Darwin’s theory.
∞ There is variation in
characteristics between individuals
of the same species
∞ Overproduction means that organisms
produce more offspring than will
survive till adulthood.
∞ There is a struggles for existence,
or competition, between individuals
and resources.
∞ Individuals better adapted will
survive to pass on their
advantageous traits survival of the
fittest.
∞ Individuals less suited for
competition may become extinct
The result of individuals becoming more
suited to a particular way of life
means that over time new species
emerge –speciation-.
You can see this in the many different
species of birds that developed
from a common ancestor. The change
is called evolution
◊ Speciation (the formation of new species)
provides evidence for the natural selection of
organisms.
◊ Geographical isolation is one way speciation
occurs, e.g. One side of a newly formed mountain
range might be wetter and colder than the other
side.
◊ over many generations, the part of the population
on the colder side change through natural
selection (so they can survive the harsher
climate).
◊ Eventually the difference in characteristics is
so great that the population living in the
harsher climate becomes a new species

◊ Inherited characteristics are
controlled by genes, which are
sections of chromosomes,
chromosomes are long molecules of
DNA tightly wound around
proteins.
◊ Genes enables cells to make
proteins, which result in
characteristics such as eye
colour and leg length.
◊ Each sperm and egg contain only
half set of chromosomes- in the
case of humans this means 23
(human cells have 46 chromosomes)
◊ When the gametes fuse during
fertilisation, the half-set of
chromosomes from the male pairs
up the half set of female
chromosomes to form a full set
B1.8 GENES
◊ Each chromosome in a pair
carries the same genes in
exactly the same place (locus)
◊ An allele is one form of a gene.
◊ If the alleles of a pair are the
same, the individual is
homozygous for the
characteristic
◊ If the alleles are different,
the individual is heterozygous.
◊ An allele may be dominant or
recessive. Dominant alleles mask
the effects of a recessive
allele.

◊ Pedigree charts show the
way characteristics of
related individuals pass
from one generation to
the next.
◊ They provide helpful
information about the
lineage of lineage of
plants and animals,
which is important to
farmers.
B1.9 EXPLAINING INHERITANCE
◊ The alleles in an organism are its genotype.
◊ What characteristics are expressed is its phenotype.
◊ The possible genotypes produced when two organisms breed can
also be shown in a punnett square.

Sickle cell disease
◊ A co-dominant disease
◊ Symptoms: tiredness, painful joints and muscles, fever, anaemia, jaundice,
sudden pain known as sickle cell crisis caused by sickled red blood cells
forming clumps in the bloodstream, blocking blood flow to organs and
causing organ damage.
◊ Cause:a mutation that alters haemoglobin molecules and causes them to
absorb less oxygen. This also results in the red blood cells becoming
sickled shaped.
◊ treatments: medication, lots of fluids and blood transfusions.
B1.10 GENETIC DISORDERS
Cystic fibrosis
◊ Recessive disease
◊ Symptoms: breathing difficulties, lung infections, malnutrition,
infertility, lung infections because of bacteria becoming trapped in
the mucus, bone disease.
◊ Cause: overproduction of thick sticky mucus which blocks the air
passages, gut and pancreas.
◊ Treatments: physiotherapy and massage, medication, and a nourishing
diet.

 Thermoregulation ;the regulation of body temperature (37°C)
 Glucoregulation; the regulation of blood-glucose levels.
 Osmoregulation; the regulation of water in the body.
 Negative feedback; the process by which homeostasis works: stimulus -
receptor - control centre - effector – response.
 Hypothalamus; the part of the brain which controls body temperature and
other things
B1.11 HOMEOSTASIS
 Vasodilation; blood vessels close to the
surface of the skin widen (in order to
lower body temperature, by heat being
radiated out into environment).
 Vasoconstriction; blood vessels close to
the surface of the skin contract (in order
to reduce heat loss, to warm up)

When the body get’s too hot
 Vasodilation; heat is radiated out into surroundings from blood flow
closer to the skin.
 Sweat glands secrete sweat, which evaporates and transfers heat energy
from the skin to the surroundings, it also absorbs heat energy from the
skin and so cools it.
 Hairs lay flat to prevent heat from being trapped
B1.11 HOMEOSTASIS
When it’s too cold.
 Hypothalamus detects drop in temperature.
 Initiates negative feedback mechanism.
 Erector muscles raise hair so an insulating
layer of air is trapped, which warms the
body up.
 Blood flow to the surface of the skin is
restricted by narrowing blood vessels to
reserve heat.
 Muscles vibrate to generate heat energy from
movement.

B1.12 SENSITIVITY
 Sensory neurones; carry nerve impulses
from the receptors to the CNS. They have
long dendrons and short axons
 Motor neurones; carry nerve impulses
from the CNS to the effectors. Many short
dendrons and one long axon
 Relay neurones; carry nerve impulses
inside the CNS from sensory neurones to
motor neurones. Short dendrons and axons.
 the order of stages in a reflex arc:
Neurone ➳ relay neurone ➳ motor neurone
➳ effector
Synapses are gaps that exist between
neurones

B1.13 SKIN SENSITIVITY
 stimuli and responses are linked by the nervous system in the
following pathway
stimulus➜receptor ➜ sensory neurone ➜ CNS ➜motor neurone ➜
effector ➜ response
 the involuntary behaviour of a
person pulling their foot away after
stepping on a pin is known as a
reflex response.
Reflex responses are automatic and
usually fast, they help to protect
the body from damage.
A reflex response is brought about
by a chain of nerves called a reflex
arc

B1.14 RESPONDING TO STIMULI
 Myelin sheath; insulating envelope that surrounds an axon, helps with
speeding up of electrical impulse travel.
Synapse; a small gap where one neurone connects to another.
Dendrites; the tiny branches of dendrons which are connected to cells
Axons; branches which convey the electrical impulses away from the cell
body
Neurotransmitters; chemicals that transmit impulses across synapses

B1.15 HORMONES
Pancreas; an endocrine gland: controls blood sugar levels using
insulin and glucagon
Adrenal glands; an endocrine gland: Produce adrenaline to speed up
the heart rate and speed up responses to stimuli.
Pituitary gland; an endocrine gland: release anti-diuretic hormone
(ADH) which conserves water in the body by making the kidneys
produce more concentrated urine
Endocrine glands; parts of the body which produce hormones
Target organ; an organ that responds to a certain hormone

B1.16 DIABETES
 Insulin; a hormone released by the pancreas which reduces the blood sugar
level by causing the liver to turn glucose into glycogen.
Glycogen; a store of glucose in the liver.
Glucagon; a hormone released by the pancreas which increases the blood
sugar level by causing the liver to turn glycogen into glucose.
BMI; a measurement that uses a person's weight and height to determine if
they are of a healthy weight.
The pancreas monitors the level of blood glucose and triggers a response to
return the levels to normal if they change.
Type 1 diabetes
◊ Between 5 and 10% of
diabetics have Type 1
diabetes.
◊ When the pancreas does not
produce insulin.
◊ Is controlled by injecting
manufacture insulin to reduce
the blood sugar level, and
avoiding foods that contain
lots of glucose
Type 2 diabetes
◊ Either cells/target organs
don't respond to insulin, or
the person becomes immune to
the effects of the hormone.
◊ Is controlled by eating a
healthy diet, having regular
exercise and losing weight.
◊ Obesity increases risk of
type 2 diabetes as well as age
and lack of exercise.

B1.17 TROPIC RESPONSES
Plant growth hormones
◊ Positive tropism; growth towards a stimulus
◊ Negative tropism; growth away from a stimulus
◊ Phototropism; a growth towards light.
◊ Gravitropism; a growth downwards (positive) or upwards (negative) in response to
gravity.
◊ Auxins; plant growth hormones which control growth at the tips of shoots and
roots.
◊ Gibberellins; plant growth hormones which stimulate seed germination, stem growth
and flowering.
◊ Uses of gibberellins; weedkillers, rooting powder for cuttings, controlled
ripening of fruits while in transportation or in shops, applying them to
unpollinated flowers so the fruit grows but not the seeds

B1.18 PLANT HORMONES
Phototropism
◊ plants roots are negatively phototrophic (move away
from light)
◊ plants shoots are positively phototrophic,(move
towards light) to get enough light for photosynthesis.
◊ positive phototropism is caused by plant hormones
called auxins.
◊ auxins are produced in the tip of a shoot, where
they cause elongation of the cells.
◊ concentration of auxin is higher on shaded side of
shoot so that shoot bends towards light.
◊ root tropism works in similar but reversed ways,
concentration of auxins would be higher in underside
of root so roots can seek out minerals to grow.
◊ roots show positive gravitropism
◊ gibberellins, initiate germination (the first
emergence of a shoot) by causing starch stored in seed
to be turned into sugars that the seed uses for energy
to grow.
◊ gibberellins also stimulate flower and fruit
production in some plant species.

B1.19 USES OF PLANT HORMONES
Selective weed killers
◊ artificial auxin is used as a selective
weed killer because it only makes plants
with broad leaves over grow without
effecting produce.
Rooting powder
◊ synthetic auxins are also used in
rooting powders.
◊ plants cuttings are dipped in rooting
powder, which makes them develop roots
more rapidly.
◊ large numbers of the same plant can be
produced quickly using cuttings compared
to growing from seeds
Seedless fruits
◊ some seedless fruits are produced using
plant hormones.
◊The flowers are sprayed with plant
hormones that cause fruit to develop but
not seeds.
◊ fruits like seedless grapes are sprayed
with gibberellins to increase size.
Fruit ripening
◊ plant hormones naturally control the
ripening of fruits.
◊ farmers can make use of this and control
when ripening occurs.
plant hormones are sprayed onto
• fruit trees to stop fruit from falling and
getting damaged
• fruit trees to speed up ripening, all the
fruit ripens quicker and can be picked in
one go
•Unripe fruit to make them ripe
• a plant hormone called ethene gas is
released onto fruit so they ripen just in
time to be delivered to shops

B1.20 EFFECTS OF DRUGS
&
B1. 21 REACTION TIME AND DRUGS
◊ Addictive; your body is physically
dependent on it
◊ reaction time is how long it takes for a
person to respond to a stimulus.
◊ this depends on how quickly and how much
neurotransmitter is released.
◊ Inhibition; restraint of a behavioral
process, a desire, or an impulse
◊ painkillers; such as morphine
deaden pain, block nerve impulses so
we feel less pain.
◊ hallucinogens; like cannabis, magic
mushroom, LSD and solvents, produce
sensations of false reality called
hallucinations, changes the way the
brain works. This distorts our senses
of colour, time and space.
◊ stimulants; including caffeine,
increase the speed of reaction times,
increases speed of neurotransmission
across synapse.
◊ depressants; such as alcohol slow
down activity of the brain and
reaction times.
◊ Narcotic; drug that makes you feel
sleepy

B1.22 THE DAMAGE CAUSED BY
SMOKING
Tobacco contains many chemical substances that
damage living tissue.
◊ Tar; coats the lining of the lungs making them
less able to take in oxygen, and also contains
carcinogens (causes cancer)
◊ Carbon monoxide; a poisonous gas which reduces
the capacity for red blood cells to carry oxygen by
permanently attaching to haemoglobin.
◊ nicotine is the addictive part of tobacco and
makes it hard to give up.

B1.23 THE EFFECTS OF ALCOHOL
Short-term effects of alcohol
Slower reflexes, blurred vision, lower inhibitions.
Long term effects of alcohol
• Liver cirrhosis; Over-consumption of alcohol causes the death of liver cells,
forming scar tissue that blocks blood flow. This leads to toxic substances
building up in the body.
• reduced fertility
• brain damage

B1.24 ETHICS AND TRANSPLANTS
• Donor; the person donating the healthy
organ for the transplant
• Ethical Decision; a decision made to reach
an answer that is fair based on what you
think is right and wrong.
• there are many moral and ethical issues.
-Weather it is right to use animals
- weather money should be an incentive in a
decision to donate organs.
- wider human right (transplant tourism)
In a transplant, a healthy organ such as a heart or liver is taken from one
body (the donor) and put into a patient to replace an organ that no longer
functions properly

B1.25 - .27
• Antiseptic; chemical substances that kill pathogens outside the body. Usually
found in sprays or gels.
• Antibacterial; chemical substances that kill bacteria outside the body. Found in
hand washes.
• Antibiotic; a substance used to treat a bacterial infection inside the body.
• Antifungal; a substance used to treat a fungal infection inside the body
• Resistant; bacteria that is no longer effected by an antibiotic.
• MRSA; an antibiotic resistant bacteria
• infectious disease are those caused by pathogens
that spread from person to person.
•Cholera bacteria are found in water contaminated
with sewage.
• viruses that cause colds and flu are airborne.
• salmonella is a type of food poisoning that comes
from chicken. Cooking food thoroughly and good
hygiene decreases the risk of getting salmonella.
• HIV is a virus that causes AIDs, it destroys
white blood cells that contribute to the immune
system.
•Athlete's foot is a fungal infection that can be
spread through contact.
•The bacteria that cause diarrhoea produce
endotoxins (poisons).

B1.25 - .27
• Physical Barrier; A barrier that stops pathogens getting into the body. Examples
are skin and blood clotting
• Chemical Barrier; a barrier that kills pathogens before they can harm us. Examples
are lysozymes in tears and stomach acid.
• The skin, or epithelial surface, serves as the primary barrier to microbial entry
into the body; skin peeling, drying out, and the skin's acidity all serve to
dislodge or kill foreign pathogens.
•Orifices such as the eyes and mouth, which are not covered by skin, have other
mechanisms by which they prevent entry; tears wash away microbes, while cilia in
the nasal passages and respiratory tract push mucus (which traps pathogens) out of
the body.
•Many chemical barriers also exist once pathogens make it past the outer physical
barriers; the acidity of the stomach ensures that few organisms arriving with food
survive the digestive system.

B1.28 INTERDEPENDENCE AND
FOOD WEBS• Biomass; The total mass of organic matter comprising a group of organisms in
a particular habitat
• Predator; an animal which kills and eats an animal
• Prey; the animal hunted and killed by its predator
• Population; the numbers of a particular species in a particular ecosystem
• Interdependent; animals that depend on each other for food
• Trophic Level; each step in a food chain or web
•Food Chain; a series of steps in which organisms transfer energy by eating and
being eaten
• Secondary Consumer; a carnivore; an organism which feeds on the primary
consumer.
• Primary Consumer; a herbivore; an organism that eats plants or other
autotrophs.
• Producers; plants which make their own food in photosynthesis.
•Pyramid of number; pyramid which shows the number of organisms at each trophic
level.
• Pyramid of Biomass; pyramid which shows the total dry mass of organisms at
each trophic level
• Parasitism examples; dog & fleas, head lice & human, tapeworm & human,
mistletoe & tree.
• Mutualism examples; oxpecker & buffalo, cleaner fish & large fish,
nitrogen-fixing bacteria & legume, chemosynthetic bacteria & giant
tubeworms

B1.29 PARASITES AND
MUTUALISTS
• Host; the larger participant in a host-parasite relationship, serving as home and
food source for the smaller parasite
• Parasite; an organism that feeds on the cell contents, tissues, or body fluids of
another species (the host) while in or on the host organism. Parasites harm but
usually do not kill their host
• Mutualism; an relationship in which both organisms benefit
• bacteria that can turn
gaseous nitrogen into nitrogen
compounds are called nitrogen-
fixing bacteria. Some live in
the root nodels of leguminous
plants
•The bacteria are protected
from the environment and
obtain chemical substances
from the plant which they use
as food.
•The plant gets nitrogen
compounds which it uses for
growth.
• chemosynthetic bacteria are
producers that get their energy
from chemical substances rather
than from light.
•Some live inside giant tubeworms
•The tubeworms gather the chemical
substances that the bacteria
need for chemosynthesis and
tubeworms feed on substances made
by the bacteria.
• chemosynthetic bacteria is given
protection in return

B1.30 POLLUTION &
B1.31 POLLUTANTS AND PLANT GROWTH
• Chemicals that are harmful to our health and wildlife are called pollutants. These
can be released into the environment causing pollution.
• nitrates and phosphates are pollutants in fertilisers, which are used to increases
crop yield, which can lead to eutrophication.
•Which is when the nitrates and phosphates leach out into water causing an algal
bloom hence blocking sunlight from reaching the bottom , and preventing the aquatic
plants at the bottom form photosynthesizing and reducing oxygen availability for
other aquatic life, eventually the plants die from not being able to
photosynthesise and symbiotic bacteria feed on them whilst further reducing oxygen
availability as they respire, hence leading to other aquatic life e.g. Fish to die
• the more polluted a river is with sewage, the less oxygen these is in solution
because of eutrophication. Fewer species survive in the polluted parts.
• scientists use these indicator species to assess pollution levels.
• Freshwater Shrimp; show that that water is clean and free of pollutants
•Stonefly Larvae; show that the water is clean and free of pollutants
• blood worms; show water is polluted
•Sludge worms; show water is polluted (as they survive in areas of low oxygen)

B1.32 INDICATOR SPECIES
•Green Lichens; show that the air is free of Sulfur Dioxide.
•Yellow Lichens; show that the air is heavily polluted with Sulphur Dioxide.
•Black spot fungus is an infection on roses that show less pollution, as they die in
high levels of sulphur dioxide
• sulfur + oxygen = sulfur dioxide
• pollution with sulfur dioxide reduces air quality and dissolves in water vapour to
form acid rain, which passes into lakes and rivers.
• acidic water kills fish
• lowers soil pH

B1.33 THE CARBON CYCLE
•Carbon is recycled as carbon dioxide (CO2) through
respiration and photosynthesis in the carbon cycle.
• plants absorb CO2 from the environment which
enables them to produce sugars through
photosynthesise.
•The sugars can be used to form other carbohydrates
and proteins that build up plant bodies.
• when plants are eaten by animals the carbon in
plant tissues become a part of animal bodies,
transfer of carbon continues through food chain.
• during respiration organisms release carbon
dioxide into the air as well as combustion of fossil
fuels
• chalk is formed from the fossilised remains of
dead sea creatures exposed to rain, the chalk
dissolves and more carbon dioxide is released.
• carbon dioxide is returned to the atmosphere
through combustion of fossil fuels and animals, and
decomposers respiring.

B1.33 THE NITROGEN CYCLE
• Nitrogen Cycle; natural process by which
nitrogen, either from the atmosphere or from
decomposed organic material, is converted by
soil bacteria to compounds that can be
assimilated by plants.
• Urea; a soluble nitrogenous waste produced
in the liver by a metabolic cycle that
combines ammonia with carbon dioxide.
• Nitrogen Fixing Bacteria; bacteria that fix
nitrogen gas into ammonia.
• Nitrifying Bacteria; bacteria that convert
ammonia to nitrates
• Denitrifying Bacteria; bacteria that
convert nitrates to ammonia
•Nitrogen fixation ➮decomposition ➮nitrification ➮ denitrification

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