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Inheritance & Health Key Notes
Inherited Features
Offspring get half of their inherited features from each parent.
During fertilisation, the nucleus from the sperm cell joins with the
nucleus in the egg cell, and a new nucleus is formed with all the genetic
information needed
The sperm cell is extremely streamlined, with a powerful tail for
swimming. It also has special chemicals in its head to help it penetrate
the egg cell.
The egg cell is full of cytoplasm, used as an energy store for when
fertilisation occurs. It also has a special barrier, which only allows one
sperm to penetrate and fertilise it.
Both contain a nucleus, containing genes…
Some variations are inherited, whilst other variations are due to
environmental factors
Inherited variation is a characteristic you have got from your parents what can you inherit?
Gender
 Eye colour
 Hair colour
 Skin colour
 Lobed or lobeless ears
During fertilisation half the genes are transferred from the male
(sperm), and half from the female (egg)
This is why you inherit characteristics from both your mum and your dad
(half from each)
Likewise, your siblings (brothers and sisters) also have half the genes of
your mum, and half of your dad (but your are not identical to them
because the genes can mix slightly)
Environmental Variation
Characteristics of animals and plants can be affected by factors such as
climate, diet, accidents, culture and lifestyle
If you eat too much you will become heavier, and if you eat too little you
will become lighter
A plant in the shade of a big tree will not be able to photosynthesise as
quickly as one in the sunshine, so it will be smaller
Variation in a feature as a result of the surroundings, is called
environmental variation
Variation can occur within a species (i.e. some people have blue eyes,
others have brown eyes)
A great amount of variation also occurs between species (i.e. guerrillas
are generally hairier than fish)!
Selective Breeding; cloning; & genetic engineering
Species gradually evolve by a process of natural selection - individuals in a
species show a wide variation (due to gene differences)
Individuals with inherited features best suited to their environment are
most likely to survive and reproduce: passing on their genetic information
to their offspring
Over time, a species can change its appearance, and may even become a
new species, unable to reproduce successfully with individuals of the
original species. Individuals with the most favourable genes for the
environment they live in are selected over time: this is natural selection
Selective breeding is a process used to produce different breeds of
animals or varieties of plants that have useful characteristics
Using selective breeding you can produce a specific offspring with useful
characteristics of both parents
Exact copies of organisms are called clones - they have identical genetic
information as the organism they were cloned from. Cloning is the
production of genetically identical copies
Clones frequently occur naturally, but they can also be produced
artificially. Cloning is an example of asexual reproduction (where genetic
information comes from just one parent)
Clones can also be produced artificially - you can take a small number of
cells from a 'parent' plant and ‘grow’ them in a medium rich in nutrients
and plant growth hormones
Genetic engineering takes genes from one organism, and places them into
the chromosomes of another organism. It alters an organism's genetic
code, and works because there is only one code for life
Genetic modification can be used to help many people - e.g. people
suffering from diabetes can get their insulin from genetically modified
bacteria, rather than having to extract it from other humans / animals
Some people believe growing and eating genetically modified plants could
be dangerous because they contain genes, which are not natural
Fitness & organ systems
Being fit means your body is able to do the activities your lifestyle
demands - e.g. being able to run; get upstairs without getting out of
breathe; being strong enough to lift things etc…
Fitness is different for each person, but is made up of:  Strength
 Speed
 Stamina
 Suppleness
When you exercise your muscles work harder - using up more oxygen
To compensate, your heart beats quicker pumping more blood around your
body. Your breathing rate also increases, allowing you to get more oxygen
into your body (and expel more carbon dioxide)
Fit people (who exercise a lot) have stronger heart muscles, so their
heart pumps more blood with each beat. This means it can beat less than
an unfit person’s and still pump the same amount of blood
Fit people usually have slower resting heart beat rates. After exercise a
fit person’s heart rate usually returns to its resting rate quicker than an
unfit persons. This is also true of their breathing rate
Respiration takes place in the cells (it is not “breathing in and out”)
Respiration is the release of energy (from glucose) in our cells
Animals and plants respire. In the light plants respire, but produce the
oxygen for this to occur by photosynthesis - the carbon dioxide they
produce via respiration is used for photosynthesis. In the dark plants
respire, producing carbon dioxide
glucose + oxygen  carbon dioxide + water + (energy)
C6H12O6 + 6O2  6CO2 + 6H2O + (energy)
Respiratory (breathing) system (lungs; trachea; alveoli) - helps with
absorbing oxygen from the air, and removing the waste carbon dioxide
Circulatory system (heart; veins; arteries; capillaries) - helps transport
materials necessary for respiration
Digestive system (stomach; small intestine; oesophagus) - helps digest
and absorb food for respiration
Skeletal system - helps support parts of the body
Breathing:  Breathing in (inhale) - ribs move up and out, diaphragm contracts
(pulled down)
 Breathing out (exhale) - ribs move down and in, diaphragm relaxes
(moves upward)
For respiration to occur, we need to get oxygen from the air to the blood,
and remove waste carbon dioxide from the blood
Alveoli in the lungs are adapted to make gas exchange happen easily and
efficiently: they cause the lungs to have a very large surface area; are
moist with thin walls; and have many capillaries
Smoking is extremely bad for your health, containing:  Carbon monoxide – a poisonous gas that reduces the amount of
oxygen that red blood cells carry around the body
 Tar – a brown, sticky substance that consists of tiny particles and
is formed when tobacco smoke condenses. Deposited in the lungs, it
coats the surface of the alveoli
 Nicotine – an addictive drug that affects the central nervous
system, increasing the heart rate and narrowing the blood vessels,
causing high blood pressure
Circulation & diet
The circulatory system is the body's main transport system, carrying
food and oxygen to the cells and taking waste products (carbon dioxide)
away. It consists of the heart; arteries; veins; and capillaries
The heart pumps blood around the body – in humans this is a four
chambered pump. The right side of the heart pumps deoxygenated blood
to the lungs to pick up oxygen. The left side of the heart pumps the
oxygenated blood from the lungs around the rest of the body (which is
why it is more muscular)

Arteries are thick-walled muscular tubes which carry blood away
from the heart - fast flowing!

Veins are thin walled tubes which carry blood back to the heart –
they have a large diameter and valves as the blood flows slower

Capillaries are extremely narrow tubes which carry blood through
our tissues: their walls are just one cell thick - so thin that oxygen,
food and waste products can easily pass through them
Heart disease occurs when some of the heart muscle cells die. It is often
caused by a build up of fatty substances inside the arteries
(arteriosclerosis).
This fatty material reduces the amount of blood which can get to the
heart muscle tissue
Smoking, drinking, lack of exercise and poor diet can all increase the
likelihood of heart disease: a complete blockage leads to a heart attack
(smoking constricts the blood vessels)
Exercise can help - it strengthens the heart muscle tissue and improves
circulation and blood flow.
If a person is unfit their heart is not as muscular as a fit persons - this
means it needs to work harder to pump blood around the body
After exercise the heart will be working very hard, but if the arteries
are clogged with excess cholesterol then not enough blood (containing
oxygen) can get around the body
This means the person’s cells will not be getting enough oxygen to
function - which can be life threatening (hence if you are unfit you
breathe harder and faster than a fit person after some exercise)
If you have too little of a particular nutrient, we say that you have a
deficiency in that nutrient, e.g. fibre deficiency can lead to constipation
Alcohol & drugs
Alcohol is a recreational drug that has short term and long term effects
on the body
Alcohol is a depressant that works by slowing down the nervous system
and relaxing the brain - it can reach the brain in <1 minute
The liver breaks down alcohol to remove this toxic drug from the body too much alcohol can damage the liver and brain
Alcohol can result in some serious behavioural changes in people - it’s a
depressant (slows the nerve impulses) which can make people feel relaxed
and happy, but also severely slows their reaction times
But it is different for different people - some people can become
aggressive, confused and loud! These include brain damage - from brain
cells being destroyed
The liver is also extremely vulnerable - the liver breaks the toxic alcohol
down, but too much of it slowly kills of the liver cells leading to cirrhosis
and possibly cancer
Alcohol also stops some vitamins being absorbed into the body - heavy
drinkers will suffer vitamin deficiencies. And if you’re pregnant, all the
poisonous alcohol in your blood will pass to the foetus - severely affecting
its development
A drug is any substance that changes the way the body or mind works.
Drugs are substances that have effects on the body
Medicines are drugs that help people suffering from pain or disease, such
as aspirin or penicillin
Other drugs, often called recreational drugs, are taken for pleasure.
Some recreational drugs are legal, such as tobacco, alcohol and caffeine.
Most other recreational drugs are illegal, such as cannabis, ecstasy and
heroin. Recreational drugs are addictive, and they may be depressants or
stimulants.
Stimulants - increase the speed at which nerves carry messages (they
make you feel more alert)
 Caffeine (legal)
 Cocaine
 Ecstasy
 Amphetamines
They make you feel more energetic and confident, but they can damage
the liver and heart.
They can also cause loss of memory and concentration, and bring an
increased risk of mental illness.
Depressants - slow down messages in the brain and along the nerves (they
make you feel more relaxed, happy, distorted view of surroundings)
 Alcohol (legal)
 Cannabis
 Solvents
 Heroin
Some of the long-term effects of depressants on the body include
damage to the liver, brain and heart
Alcohol can cause weight gain; solvent abuse causes a rash around the
nose and mouth; cannabis causes loss of memory and concentration, as
well as an increased risk of mental illness.
Antagonistic Muscles
The skeleton has three main functions:  Supporting the body
 Protecting some of the vital organs
 Helping the body move
Muscles can only pull, and they work by getting shorter (contract)
As muscles can only pull, each joint is moved by a pair of muscles - an
antagonistic pair
Muscles are attached to bones by strong tendons - when a muscle
contracts, it pulls on the bone, and the bone can move if it is part of a
joint
The elbow joint lets our forearm move up or down, controlled by two
muscles, the biceps on the front of the upper arm, and the triceps on the
back of the upper arm: 

When the biceps muscle contracts, the forearm moves up
When the triceps muscle contracts, the forearm moves down
Pulled muscles - muscle fibres (linking muscle cells together) are
stretched or torn
Sprains - ligaments in a joint are torn (ligaments are cords which attach
the bones together)
Cartilage injuries - cartilage at the end of the bone gets torn
Dislocations - bones in a joint move apart or out of line