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Biology
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Life processes
All living things carry out seven life
processes in order to be classed as ʻaliveʼ.
The seven life processes are:
Typical animal & plant cells
Animal cell
Functions of the cell parts
Cell Part
Movement - moving to access resources
Nucleus
The control centre of the
cell. Contains genetic
information.
Cytoplasm
Watery, jelly-like liquid that
fills the cell.
It is where the chemical
reactions take place.
Cell
Membrane
Controls what enters and
leaves the cell.
Cell Wall
Provides support to the cell,
helping it to keep itʼs shape.
It is made from cellulose.
Chloroplasts
Absorb the sunlight energy
for use in photosynthesis.
They contain the green
pigment, chlorophyll.
Vacuole
Stores cell sap, a solution
of sugar and salts.
Respiration - using oxygen to produce energy
Sensitivity - being aware of the surroundings
Plant cell
Function
Nutrition - obtaining food
Excretion - getting rid of toxic waste substances
Reproduction - producing offspring
Growth - growing to full adult size
LIFE PROCESSES
& CELLS
Using a microscope & preparing slides
Here is a typical example of a microscope you may
find in a school laboratory:
To prepare a slide for viewing...
(1) Place specimen onto a clean slide.
(2) Add stain if necessary (iodine often used for plant cells, methylene blue for animal
cells).
(3) Slowly lower a cover slip onto the specimen (avoid trapping any air bubbles).
(4) Drain off any excess stain from around the sides of the cover slip.
(5) Place slide onto stage of microscope.
To view a slide using a microscope...
(1) Make sure that the objective lens is set to low power.
(2) Provide a stream of light up into the microscope via the light source.
(3) Place a slide onto the stage and secure it with the stage clips.
(4) Look down the eye piece and use the focussing knobs to obtain a clear image.
(5) If high power is required, rotate the objective lens disc to a higher setting.
Specialised cells
Specialised cells are adapted to carry out a
specific role in an organism, that no other types of
cell perform. Here are some examples:
Nerve cells: carry impulses
(signals) from the brain or spinal
cord to other parts of the body.
Cells, tissues and organs
A group of similar cells form a tissue e.g.
muscle cells form muscle tissue
A collection of organs
working together form
an organ system e.g.
the muscle system
A collection of organ
systems form an
organism e.g. a human
A collection of tissues forms an organ
e.g. the heart
Sperm cells: the male gametes
(or reproductive cells) of an
animal. Designed to fertilise the
egg.
Organs
Palisade cells: found on the top
side of a leaf and packed with
chloroplasts, these plant cells are
designed for photosynthesis.
Red blood cells: contain
haemoglobin to absorb and carry
oxygen around the body.
Muscle cells: made of fibres
which can contract or relax to
cause movement.
CELLS & CELL FUNCTIONS
Organs are made up of different tissues which when
put together in a structured way, carry out a specific
process in an organism.
An organ system is a group of organs working
together to perform a complex process in an
organism.
Some organisms have multiple organ systems to
carry out the major functions for survival, whilst other
organisms just need certain organs.
Root hair cells: found in the
roots of a plant and designed to
increase the surface area for
greater absorption of water and
minerals.
Fertilisation
Fertilisation is the fusion of male and female gametes (sex
cells).
When gametes fuse, the first cell of a new organism is
created (the zygote).
In living things that reproduce sexually, fertilisation is part of
the process of reproduction.
Examples of human organ systems include:
circulatory system (moving blood around the body),
respiratory (for taking in oxygen and removing CO2),
nervous (sending impulses to and from the brain),
excretory (removing toxic waste), reproductive
(producing offspring), digestive (for breaking down &
absorbing food), endocrine (hormone production)
Human life cycle
Between the stages of birth and death, humans go through significant physical and mental changes.
Requirements for growth
In order to achieve full, healthy growth,
particularly between birth and
adulthood, humans need the following:
•
•
•
•
Correct intake of main food groups
Regular exercise
A healthy living environment
Avoidance of unhealthy substances
Although people are capable of reproducing
once they go through puberty, most wait until
they are adults before having children. As
adults they can usually cope better with the
demands of being parents, both emotionally
and financially.
From birth to adulthood some of the changes
include:
• physical maturity - growing to full size
• sexual maturity - becoming capable of
producing children
• mental maturity - reaching peak intellect
• emotional maturity - becoming self
sufficient and independent.
HUMANS AS ORGANISMS
Growth
Death is the natural final stage in the
human life cycle, when the bodyʼs
systems can no longer sustain life.
Death can happen at any point in the
life cycle due to illness or accidents,
but it naturally follows old age.
Death
When the old age stage is reached, humans may notice even
further changes to their physical and mental abilities:
• they may shrink in height and muscular size
• they're bones may weaken and become more brittle
• further reduction in hormone levels may affect some body
functions
• some may suffer memory loss or a reduction in mental
capacity
• there may be a reduction in efficiency of major body
organs
• more prone to illness as immune system deteriorates
Old age
Humans remain at the adult stage for quite some time
but may notice changes to their bodies as they age,
including:
• charges to the skin (lines and wrinkles)
• changes to the hair (hair loss, greying, texture)
• changes to body composition (muscle loss, fat
gain)
• reduced physical ability (not as fast, less
endurance)
• onset of menopause in women.
Joints and Muscles
The Skeleton
The skeleton performs 3 major functions:
• Support - it is the frame that body organs hang off
• Protection - parts of the skeleton protect vital organs
e.g. skull protects the brain, ribs protect heart & lungs
• Movement - the skeleton is attached to muscles via
tendons which pull on the bones to make us move.
Where bones meet a joint is formed. There are three main types of joint:
• Immovable joints - no movement in the joint e.g. between bones of the skull
• Slightly movable joints - some flexibility e.g. between vertebrae in the spine
• Freely movable joints - large range of motion e.g. elbow, knee, hip, shoulder
Three main types of freely movable joints exist - hinge (e.g. elbow), ball & socket (e.g. shoulder), sliding
(e.g. wrist).
Within many joints cartilage may be found between the bones to provide protection and act as a shockabsorber during movement. Synovial fluid may also be found within freely movable joints to act as a
lubricant.
Muscles - bands or bundles of fibrous tissue that have the ability to contract. In freely movable joints
such as the knee, muscles may work in pairs called antagonistic pairs, contracting on opposite sides of
the bones to produce movement in the joint - when one muscle contracts, the other relaxes.
Knee Joint
HUMANS AS ORGANISMS
Movement
Tendons - connective tissue that attaches muscle to
bone allowing the muscle tissue to pull on the bone
and so produce movement at a joint.
Ligaments - tough connective tissue that attaches
bone to bone providing strength and stability at a joint.
The roles of the heart and circulation
The more you move, for example during exercise, the greater the energy requirement of your muscles.
In order to release more energy from stored glucose, the muscles must have a greater amount of oxygen.
To achieve raised oxygen levels, your breathing rate increases, as does your heart rate.
Your lungs work harder to take in more Oxygen from the air (and get rid of extra CO2) and your heart works
harder to pump blood around the body faster, to supply the muscles with the Oxygen they require.
After exercise your heart rate remains high as does your breathing rate, in order to remove the toxins and
waste products of respiration. Your heart and breathing rates then steadily return to normal (more quickly the
fitter you are).
Lung Structure
The lungs are a pair of organs in the chest that are
responsible for breathing, allowing blood to pick up oxygen
from the air. Movements of the ribs, rib muscles and
diaphragm allow air into and out of the lungs. When you
breathe in, air passes from your nose or mouth, through the
windpipe (trachea) and into one of the two airways (bronchi)
which enter the lungs. These airways divide to form smaller
tubes (bronchioles), at the end of which are millions of tiny air
sacs (alveoli). It is here that oxygen is absorbed from the air,
and passes into the bloodstream to be circulated around the
body. At the same time carbon dioxide in the blood passes into
the alveoli to be breathed out. The lungs are surrounded by a
protective lining that consists of two membranes called the
pleura.
Inhaled and Exhaled Air
When compared, the proportions of the gases in inhaled air and exhaled air are different:
Gas
Inhaled air
Exhaled air
21%
17%
0.04%
4%
78%
78%
Oxygen
Carbon Dioxide
Nitrogen
The air we breathe out has less oxygen, more carbon dioxide, but the nitrogen remains the
same. There is also more water vapour in exhaled air. These changes are due to the process
of respiration in the cells of the body.
Aerobic Respiration
HUMANS AS ORGANISMS
Breathing & Respiration
GLUCOSE + OXYGEN
Alveoli
Respiration is a chemical reaction that
happens in all living cells. It is the way that
energy is released from glucose, for our cells
to use to keep us functioning.
Glucose and oxygen react together in the cells
to produce carbon dioxide and water. The
reaction is called aerobic respiration because
oxygen from the air is required for it to work.
Energy is released during the reaction.
CARBON DIOXIDE + WATER + (ENERGY)
Transportation of Reactants & Products
The reactants and products of aerobic respiration are transported around the body by the
circulatory system.
Alveoli - Oxygen and carbon dioxide are exchanged between the
air and blood in the air sacs (alveoli). The alveoli have a large
surface area, their walls are thin and moist and they have a good
blood supply, which makes them more efficient for gas exchange.
The gases move by diffusion into and out of the blood.
Small food molecules produced during digestion can be absorbed across the wall of the small
intestine into the bloodstream. Glucose is carried round the body dissolved in plasma, the pale
yellow liquid part of our blood. The dissolved glucose can diffuse into the cells of the body from the
capillaries.
Oxygen that has diffused into the blood through the alveoli is not carried in the plasma, but is
carried by the red blood cells. These contain a red substance called haemoglobin, which joins onto
oxygen and carries it around the body in the blood. Like glucose, oxygen can diffuse into cells from
the capillaries.
The carbon dioxide produced during respiration diffuses out of the cells and into the blood plasma.
The blood transports it to the lungs. It then diffuses across the walls of the alveoli and into the air,
ready to be breathed out.
Balanced Diet
Examples of Vitamins & Minerals
A balanced diet contains the different nutrients in
the correct amounts to keep us healthy. Certain
foods are not necessarily 'bad' for us, but eating too
much of them could be and, in general, too much of
any food can give rise to health problems. Eating a
balanced diet should prevent overeating and so less
food should be stored around the body, reducing
the risks associated with weight gain and obesity.
The main nutrients required in a balanced diet are
shown in the table below:
Nutrient
Function
Example
Sources
To provide
energy
Bread, pasta,
cereals
Protein
For growth and
repair
Meat, fish, dairy
products
Fat
For energy and
insulation
Butter, nuts, oil
Vitamins
To maintain
health
Fruit,
vegetables,
dairy products
Minerals
To maintain
health
Fruit,
vegetables,
dairy products,
salt, liver
Fibre
To keep food
moving
through the gut
Cereals,
vegetables
Water
For cells and
body fluids
Water, milk,
fruit juice
Carbohydrate
Not everybody needs the same diet. We need
different quantities of each nutrient in our diet
depending on our age, health and the lifestyle we
lead.
The nutritional requirements of a young child will be
vastly different from an olympic athlete or a
pregnant woman.
Name
Function
Sources
Signs of Deficiency
Eyesight, growth, appetite
Liver, carrots, leafy green
vegetables, cod-liver oil
Night blindness
Making red blood and nerves
Fish, meat, milk
Poor nerve function
Vitamin C
Immune system & healing
Fruits and vegetables
Scurvy, poor healing
Vitamin D
Strong bones and teeth
Sunlight, fish, milk
Unhealthy teeth, rickets
Strong bones & teeth
Dairy products,
vegetables
Weak bones & teeth
Iron
Red & white blood cells
Red meat, veg, grains
Tiredness, anaemia
Zinc
Immune system
Meat, grains, shellfish
Lesions on skin, poor healing
Vitamin A
Vitamin B12
Calcium
HUMANS AS ORGANISMS
Nutrition - Diet & Food
Food Tests
Test for Starch
Test for Simple Sugars
Deficiency of Nutrients
Food provides us with the energy to keep our bodies
working and the raw materials to grow and to repair
our bodies.
A diet lacking in certain nutrients can give rise to
various health problems due to deficiency.
For example, fibre is needed to keep food moving
through the intestines easily, and people who have a
fibre deficiency in their diet may get constipation.
If your diet lacks carbohydrates you may feel tired or
lack energy whilst lack of protein intake may lead to
muscle breakdown as the body acquires the protein
it needs from its own supplies.
As shown in the table above, people with iron
deficiency may get anaemia and have too few red
blood cells, whilst iodine deficiency may cause a
swelling in the neck called a goitre.
Vitamin A deficiency can cause blindness. Vitamin C
deficiency causes scurvy, which makes the gums
bleed, and vitamin D deficiency causes rickets, which
can lead to brittle bones and abnormal bone growth
in children.
Digestion
How Enzymes work in Digestion
Enzymes are special proteins that can break large molecules into small molecules. Different types of enzymes can
break down different nutrients:
* carbohydrase or amylase enzymes break down starch into sugar
* protease enzymes break down proteins into amino acids
* lipase enzymes break down fats into fatty acids and glycerol.
For example:
Digestion starts in the mouth where the food
is chopped up by the teeth and mixed with
saliva, which contains enzymes to break
down carbohydrate.
The ball of food is swallowed and muscles
push it down the gullet to the stomach.
Food is stored in the stomach whilst
enzymes break down the protein. Stomach
acid keeps the pH low for the enzymes to
work and to kill bacteria.
On the way into the small intestine more
enzymes are added from the pancreas and
the liver.
In the small intestine more enzymes are
added to digest proteins, carbohydrates and
fats. Food is absorbed through millions of villi
which cover the gut wall, into the blood
stream.
Undigested food material moves on into the
large intestine where water is absorbed. The
remaining material is stored in the rectum
ready for egestion from the anus.
HUMANS AS ORGANISMS
Nutrition - Digestion
Assimilation
Absorption
Digested food molecules are absorbed in the
small intestine. They pass through the wall of
the small intestine and into the bloodstream.
Once in the bloodstream, the digested food
molecules are carried around the body to
where they are needed.
Only small, soluble substances can pass
across the wall of the small intestine. The
inside wall of the small intestine is lined with
tiny villi which protrude and give a large
surface area. The walls of the villi are very
thin so that absorption happens quickly. The
villi also contain blood capillaries to carry
away the absorbed food molecules.
Soluble food molecules are carried
by the bloodstream to all parts of the
body, where they are used for
growth, energy and maintenance.
Egestion
Solid waste is stored as faeces in
the rectum and is egested from the
body (removed from the body) via
the anus.
Changes during Adolescence (Puberty)
Puberty usually occurs between the ages of about 10 and 16 but
it can start earlier or later for some people. Puberty is controlled
by chemicals (sex hormones) from the brain and the sex organs.
During puberty, girls and boys go through a series of physical,
behavioural and emotional changes which make them sexually
mature and capable of having their own children.
Physical Changes
Both sexes experience an increase in height, growth of hair
under the arms and pubic hair growth. Girls and boys also
experience physical changes specific to their own sex.
Behavioural Changes
Girls and boys become attracted to the opposite sex. Girls
become more maternal and boys become more aggressive.
Emotional Changes
Both sexes become more independent and want more freedom
from their parents. They also take on more responsibility for their
behaviour.
Physical changes in girls
Breasts develop
Hips widen
Periods start (Menstruation)
HUMANS AS ORGANISMS
Reproduction - Puberty
The Menstrual Cycle
When a girl goes through puberty her reproductive system includes a cycle of events
called the menstrual cycle (period). It lasts about 28 days, but it can be slightly less or
more than this. The cycle stops while a woman is pregnant. These are the main features
of the menstrual cycle:
➡ The start of the cycle, day 1, is when bleeding from the vagina begins. This is
caused by the loss of the lining of the uterus, with a little blood. This is called
menstruation or having a period.
➡ By the end of about day 5, the loss of blood stops. The lining of the uterus begins to
re-grow and an egg cell starts to mature in one of the ovaries.
➡ At about day 14, the mature egg cell is released from the ovary. This is called
ovulation. The egg cell travels through the egg tube towards the uterus.
➡ If the egg cell does not meet with a sperm cell, the lining of the uterus begins to
break down and the cycle repeats.
If the egg cell meets and joins with a sperm cell, it is fertilised. It attaches to the lining of
the uterus and the woman becomes pregnant.
Physical changes in boys
Penis and scrotum grow larger
Muscles develop in chest and shoulders
Voice deepens
Hair grows on face
A girl starts having periods
when she reaches puberty
and she will have a period
every month until the
menopause (usually in her
40s or 50s) when periods
stop altogether. If she gets
pregnant, her periods
temporarily stop until she has
had the baby and then start
again some time afterwards,
when her system has
returned to normal. Girls may
experience some physical
discomfort and raised
emotions just before each
period.
Female Reproductive System
Front view
Hostile environment
The vagina is a hostile environment for
sperm, producing acids which can harm
them and prevent them from swimming
up through the cervix. In order to
combat this, semen contains an alkali to
neutralise the acid produced by the
vagina and allow sperm to survive.
Front view
Uterus
Also known as the womb, this is where the
embryo develops into a baby.
Ovaries
These contain the eggs (ova) and alternately
release one each month into the oviducts. They
also produce key female hormones
Oviducts (Fallopian Tubes)
These tubes connect the ovaries to the uterus.
Fertilisation of the egg takes place here if sperm
are present.
Vagina
This receives the penis during intercourse and
acts as the birth canal when the baby is ready to
be born.
HUMANS AS ORGANISMS
Reproduction - Systems
Male Reproductive System
Penis
This is designed for passing urine from the
bladder and semen, containing sperm, from the
testes. It is capable of becoming erect in order
for intercourse to take place.
Testes
These are held in a sac called the scrotum and
produce sperm and the hormone testosterone.
Vas Deferens
These sperms ducts carry sperm from the testes
to the urethra.
Urethra
This tube runs through the centre of the penis to
carry semen and urine out of the body.
Seminal Vesicle, Prostate & Cowperʼs Glands
These add nutrients and fluid to sperm to make
semen.
Side view
Sex Hormones
The changes at puberty are under the
control of the sex hormones,
progesterone and oestrogen in girls and
testosterone in boys. These hormones
continue to play major roles in the
menstrual cycle and pregnancy and in
the production of sperm, after puberty.
Side view
Making Babies
Fertilisation
In order to create a new person, fertilisation of the
ova (egg) must occur. Fertilisation happens when
a male gamete (sperm cell) meets with the female
gamete (egg) and joins with it. This happens after
sexual intercourse (copulation) in which a man
puts his penis into the woman's vagina. Stimulation
of the erect penis causes semen to be released
(ejaculation). Sperm cells travel in semen from the
penis and into the top of the vagina. They enter the
uterus through the cervix and travel to the oviducts
(Fallopian tubes). If a sperm cell meets with an
egg cell there, fertilisation can happen. This is the
start of the creation of a new person.
Copulation or sexual intercourse delivers the male
gametes (sperm) to the female reproductive
system, where fertilisation may occur.
HUMANS AS ORGANISMS
Reproduction - Making a new
Person
The Zygote, Genes & Characteristics
Male and female gametes (sperm
& egg) each carry one half of the
genetic information needed to
create an individual. The sperm cell
has 23 chromosomes in its nucleus
from the father and the egg has 23
chromosomes in its nucleus, from
the mother.
When the gametes join and their
nuclei fuse (fertilisation), a zygote is
formed. The zygote has one
complete set of genetic information,
46 chromosomes,
The zygote keeps dividing to
produce a large number of cells and
eventually a foetus, which continues
to develop into a new person.
Eventually a new baby is born,
which displays characteristics
inherited from its parents. Examples
of inherited characteristics are
gender, eye colour, hair colour, skin
colour, lobed or lobeless ears,
inherited diseases and blood group.
Development of the Foetus
What happens at Birth?
Foetal development from 8 to 40 weeks
Foetus
The foetus relies upon its mother as it
develops. It requires protection, oxygen and
nutrients (food and water). It also needs its
waste substances to be removed.
The foetus is protected by the uterus and the
amniotic fluid, a liquid contained in a bag called
the amniotic sac or amnion.
The Role of the Placenta
The placenta provides the foetus with oxygen
and nutrients, and removes waste substances.
It grows into the wall of the uterus and is joined
to the foetus by the umbilical cord. The mother's
blood does not mix with the foetus's blood, but
the placenta lets substances pass between the
two blood supplies.
Oxygen and nutrients diffuse across the
placenta from the mother to the foetus whilst
waste substances, such as carbon dioxide,
diffuse across the placenta from the foetus to
the mother.
HUMANS AS ORGANISMS
Reproduction
- The Foetus & Birth
Late in the 9th month of pregnancy, the
unborn baby will start to move to get ready
for birth. Usually, this is head first.
A mother's "water breaking" may be one of
the first signs of labor. This happens when
the amniotic sac, which holds and protects
the unborn baby, breaks open. Then, some
of the fluid drains through the cervix and out
the vagina.
As the muscle contractions of the uterus get
stronger, the cervix opens (dilates) and the
unborn baby's head can push down into the
vagina. (The vagina is also called the "birth
canal.") The contractions become stronger
and more often, and the cervix opens 10
centimeters (4 inches) wide. During a normal
birth the baby's head appears first. Then the
shoulders turn and more contractions push
the baby out.
Sometimes a birth through the vagina may
not be possible or recommended. This can
be because the doctor has some worries
about the health of the mother or the baby. In
this case, a Cesarean section (C-section) is
usually done. This is a type of surgery in
which a cut is made in the mother's
abdomen and uterus. Then the baby is
removed.
Delivery is finished when the baby is outside
the mother's body. The placenta and other
fetal tissue (called afterbirth) are delivered
just a little while later. The baby's mouth and
nose are cleared of mucus. The baby
breathes and cries. Then, the baby is usually
given to the new mother.
After the delivery, the umbilical cord is
clamped and cut. This separates the baby
from the placenta. The umbilical cord will dry
and heal to form the belly button (navel).
The Effects of Smoking
Smoking damages your health. It causes
diseases ranging from lung cancer,
bronchitis and emphysema to heart disease,
which are all major killers in the UK.
Tobacco smoke contains many harmful
substances including tar, nicotine and carbon
monoxide.
Tar causes cancer of the lungs, mouth and
throat. It coats the surface of the bronchioles
and the alveoli which causes coughing and
damages the alveoli, making it more difficult
for gas exchange to take place. Tar also
damages the cilia cells lining the bronchioles
which prevents the mucus from being
removed. This leaves the individual more
prone to infection and causes coughing.
Nicotine is addictive causing a smoker to
want more cigarettes. Nicotine also
increases the heart rate and blood pressure,
and narrows blood vessels which can lead to
heart disease.
Carbon monoxide reduces the amount of
oxygen that the blood can carry. The
circulatory system has to work harder, which
can lead to heart disease.
The Effects of Drugs
Drugs are substances that affect the body. Medicines are drugs that help people when suffering from pain or
disease. Other drugs, known as recreational drugs, are taken by some people for pleasure.
Some recreational drugs are legal, such as tobacco, alcohol and caffeine. Most other recreational drugs are
illegal, such as cannabis and heroin. Any drug that is misused can cause damage to the body and may cause
other problems.
All drugs can damage the liver, because it is the liver that breaks drugs down in the body. Injecting drugs
using shared needles may lead to diseases such as HIV and hepatitis, due to infected blood.
Recreational drugs are addictive, and they may be depressants or stimulants.
Depressants slow down messages in the brain and nerves e.g. alcohol, solvents, cannabis, heroin.
Effects of depressants include feelings of well-being, lowered inhibition, slowed thinking & muscular activity,
hallucinations. Depressants can cause long-term damage to the liver, brain and heart.
Stimulants speed up messages in the brain and nerves e.g. caffeine, amphetamines, cocaine and ecstasy.
Effects of stimulants include making 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 a greater risk of mental illness.
HUMANS AS ORGANISMS
Health - Substances Affecting
Health
Positive Influences on Health
Staying healthy is clearly influenced by what you do with your
body and what you put into it. Harmful substances can
damage your body and so misuse of any kind of drug is going
to have detrimental effects.
The food you consume also plays a vital role in your health.
The right amount of nutrients from the right types of foods can
promote good health and correct functioning of your bodyʼs
organs. Conversely, over indulgence in the wrong types of
foods can lead to weight gain, heart disease and other
associated illnesses.
Exercise also affects your health, promoting muscle tone and
efficient cardiorespiratory function (heart and lungs). Regular
exercise also reduces excess fat storage and delays the onset
of aging. A fitter person is generally a healthier person.
Microbes
Microbes are micro-organisms that can only
be viewed using a microscope. There are
three main types of microbe: fungi, bacteria
and viruses.
Fungi
Not all fungi are microbes as some are multicellular organisms. Yeasts are single-celled
fungi, so they are microbes. Fungi are
usually the biggest type of microbe.
Bacteria
Bacteria are usually smaller than fungi.
Bacteria have many different shapes. Some
have flagella (tails) that allow them to swim.
Viruses
Viruses are the smallest type of microbe. A
virus can only reproduce inside a cell.
How are Microbes Spread?
Microbes can be spread through the air, through touch, through contaminated food, in
water and through contact with animals.
Air
People sneezing or coughing can transfer droplets containing microbes into the air and
these can be breathed in by other people, infecting them. Colds, flu, chicken pox and TB
are examples of infections spread by air.
Touch
Microbes can be spread by physical contact with an infected person or by touching
surfaces touched by an infected person. Athleteʼs foot is spread in this way.
Food
Poor handling or under-cooking of food can leave harmful microbes on them when eaten e.g. salmonella
Water
Dirty, untreated water can contain microbes which get into the body when the water is
swallowed e.g. cholera
Animals
Microbes carried by animals can infect a person who is bitten or scratched e.g. malaria
Harmful Microbes
Some microbes cause diseases which can
make humans very ill or even kill them.
Other microbe infections can cause effects
such as skin rashes or a general feeling of
being unwell, which are uncomfortable but
not life threatening.
Type of Microbe
Examples of Diseases
Fungi
Athleteʼs foot, Thrush
Bacteria
Salmonella, Tuberculosis,
Typhoid, Tetanus, Plague,
Dysentery, Cholera
Viruses
Common cold, Flu,
Chicken pox, Mumps,
Measles, AIDS, Hepatitis,
Rabies
A person is infected when microbes enter the
body and are able to reproduce in the body.
They produce harmful toxins and damage
tissues and organs.
HUMANS AS ORGANISMS
Health - Microbes & Disease
Not all Microbes are Harmful
Although microbes are associated with
disease, some are very useful and
indeed some are vital to our health.
Bacteria living in our digestive system are
very important in the correct functioning
of our intestines in the digestive process.
Bacteria are involved in the
decomposition of waste materials on
earth.
Certain bacteria cause changes in milk
which make yogurt and cheese.
Yeast cells are also used to make bread
and alcoholic drinks, as they turn sugar
into CO2 (which makes the bread rise)
and alcohol.
Defence against Microbes
Natural Barriers
The body has some natural barriers to prevent microbes
entering. These include the skin, scabs (to block up
cuts), acid in the stomach and mucus in the lungs.
Human Immune System
Your immune system kills microbes that get past the natural barriers.
White blood cells are the key; some engulf and kill microbes whilst
others produce antibodies which kill microbes or cause them to stick
together, making them easier to kill.
Fighting Microbes with Medicines
Antibiotics
If you have a serious infection caused by bacteria, you may be given
antibiotics to help fight the infection. Some antibiotics stop the bacteria
reproducing and others kill the bacteria.
Immunisation against Infections e.g. Tetanus, Mumps, TB
Immunisation involves injecting a person with a vaccine. Vaccines
contain a weak form of the disease-causing microbe, or some of its
antigens. The immune system then responds by producing white blood
cells with the correct antibody to kill the microbe, so you become
immune without getting ill. If you then get infected with the disease,
your body already has the white blood cells to fight it.
Requirements for Plant Growth
Photosynthesis
In order to survive and grow properly, a plant needs to
obtain several things:
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Plants produce their own food by capturing and using Sunlight energy. This is achieved using the process
of photosynthesis:
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SUNLIGHT
CARBON DIOXIDE + WATER
GLUCOSE + OXYGEN
Carbon Dioxide
Water
Light
Minerals
CHLOROPHYLL
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Plants obtain these components in different ways.
Carbon Dioxide
This is absorbed from the air through tiny holes on the
underside of leaves. These tiny holes are called
stomata (singular: stoma). The CO2 diffuses through
the stomata into air spaces between the cells. CO2 is
then used as a reactant in the process of
photosynthesis.
Light
Sunlight is absorbed by the chloroplasts in the cells of
a leaf. Chloroplasts contain the green pigment
chlorophyll which captures the light energy and uses it
to power the process of photosynthesis. The cells in
the top layer of leaves (palisade layer) are packed with
chloroplasts to make the process more efficient.
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Light is captured by the chlorophyll in the chloroplasts of leaf cells.
Chlorophyll is the green pigment in the Chloroplasts of a plant cell, so only cells containing
chloroplasts will photosynthesize.
The glucose produced during photosynthesis is then used in respiration to produce energy.
During photosynthesis, oxygen is produced as a waste product and released into the air by the
plant.
Photosynthesis can only happen during the daytime - a plant doesnʼt photosynthesise at night.
GREEN PLANTS AS ORGANISMS
Nutrition and Growth
Water
Water is needed as a reactant in photosynthesis and to
keep the plant turgid. A plant without enough water will wilt.
Water is absorbed through the root hair cells in the roots.
The Role of Root Hair Cells
Minerals
Plants also need elements such as nitrogen,
phosphorus and potassium. These are needed to allow
the plant to make other substances e.g. nitrogen for
proteins. Soil contains minerals made up of these
elements, dissolved in water, e.g. nitrates, phosphates
etc. Plants absorb the minerals from the soil water,
through their root hair cells. Fertilisers are sometimes
used to ensure the soil has minerals for plant growth.
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Root hair cells are used by a plant to obtain water and
minerals from the soil.
They are specialised cells designed for that particular
function.
Root hair cells have a large surface area and very thin
walls and so are more efficient for absorbing water and
minerals.
They have no chloroplasts because they are found in the
roots under the ground.
Plant Respiration
Respiration-Photosynthesis Balance
Plants need to respire in order to produce energy
to:
• Grow
• Take in minerals
• Move
• Make specialised cells
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The food (glucose) a plant produces during
photosynthesis is used in the process of
respiration, which releases the energy from the
glucose:
GLUCOSE + OXYGEN
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Plants, being living things, respire all the time, day and
night.
They only photosynthesise during the day, when there
is light available.
Therefore, at night, they are not producing oxygen.
During the day, the amount of oxygen produced by
photosynthesis is massive compared to the amount
the plant uses for respiration.
Plants that lose their leaves in winter store food
produced during the summer by photosynthesis. They
store enough food to last them over winter, and to
provide energy reserves for new growth in the spring.
CARBON DIOXIDE + WATER + (ENERGY)
The energy produced in respiration is used by the
plant to grow and to provide its other
requirements.
Respiration happens all the time, whether it is
dark or light (unlike photosynthesis, which only
happens in the day).
As with all living things, Carbon Dioxide is
produced as a waste product.
Water is released (evaporates) from the stomata
as part of the process of transpiration, shown
below:
GREEN PLANTS AS ORGANISMS
Respiration
The Carbon Cycle
All living organisms are made up of molecules
that contain carbon: carbohydrates, proteins and
lipids.
The carbon cycle includes all the reactions that
allow living organisms to use carbon to
manufacture their tissues and release energy.
Plants are the starting point of the carbon cycle.
Through the process of photosynthesis, plants
absorb carbon from the air (CO2) and
incorporate it into their biomass (leaves, wood,
roots, flowers, fruits). This organic matter
provides food for other organisms (consumers).
By releasing energy when they respire, living
things return carbon to the atmosphere in the
form of CO2.
Conditions
Respiration Photosynthesis Balance
Dark
Respiration but no
photosynthesis
Dim Light
Rates of photosynthesis &
respiration are equal
Bright Light
Rate of photosynthesis much
greater than respiration rate
Parts of a Flower
Stages of Reproduction
2. Fertilisation
The reproductive organs of a flowering plant
are in the flower.
The stages of reproduction in a flowering plant are as follows:
Once pollen has been transferred to the
stigma, a pollen tube grows down through
the style, into the ovary and into an ovule.
The male nucleus travels down the pollen
tube and fuses with the female nucleus to
form a zygote. This is fertilisation.
1.
2.
3.
4.
Pollination - transfer of pollen
Fertilisation - fusion of male and female sex cells
Seed dispersal - spreading of seeds away from the plant
Germination - growth of a seed into a new plant
1. Pollination
This is the process in which pollen is
transferred from the anther of a flower to the
stigma of the same (self pollination) or
another (cross pollination) flower. This
transfer of pollen can be made by the wind
or by visiting insects.
GREEN PLANTS AS ORGANISMS
Reproduction in
Flowering Plants
3. Seed Dispersal
After fertilisation, the fertilised ovule
develops into the seed and is housed in the
ovary which develops into the fruit. Seeds
can be dispersed in a number of different
ways. They may be carried by wind, water or
animals. Some plants even shoot the seeds
out explosively.
Spreading the seeds as far as possible away
is important because if the seeds are not
dispersed, many germinating seedlings will
grow very close to the parent plant. This
results in competition for resources (light,
water, nutrients) between every one of the
seedlings as well as with the parent plant.
4. Germination
Carpel
The female reproductive organ made up of
the stigma (sticky for pollen to stick to), the
style (connecting the stigma to the ovary)
and the ovary (contains the female sex cells
inside ovules).
Stamen
The male reproductive organ made up of the
anther (contains the pollen - male sex cells)
and the filament (supports the anther).
Petals
Flowers usually have colourful petals to help
attract insects for pollination.
This is the first stage in the growth of a seed.
When the conditions are right (enough
warmth, enough moisture), a root will
emerge from the seed coat, followed
eventually by the first shoot.
What is Variation?
Variation is the difference between organisms.
Different species have completely different
genes and so are completely different to other
species of organism e.g. a cow is totally
different to a rose bush.
But you also get variation within a species.
For example, humans have differences in skin
colour or blood group.
Continuous Variation
This is the type of variation where a feature
can vary over a wide range of values.
Examples of features showing continuous
variation are weight, intelligence, leaf size,
height etc. which can vary continuously over
time.
Discontinuous Variation
This is the type of variation where a feature
can only take particular values. Examples of
features displaying discontinuous variation are
blood group, natural hair colour, eye colour
etc. which can only take distinct values and
donʼt change over time.
Environmental & Inherited Variation
Some variation within a species is inherited, and some variation is due to the environment.
Environmental Variation
Characteristics of animals and plants can be affected by environmental factors and ʻupbringingʼ e.g. climate,
dangerous areas, diet, soil conditions, lifestyle.
Variation in characteristics as a result of the surroundings is called environmental variation. Examples of this are
weight, plant size, religion, flower colour, language etc.
Inherited Variation
People have similar physical features to their parents, but they will not be identical to either of them. This is
because they get half of their inherited features from each parent; half of their genetic information came from the
motherʼs egg and half from the fatherʼs sperm.
Variation in characteristics, as a result of inheritance from the parents, is called inherited variation. Examples of
this are eye colour, skin colour, gender, blood group, shape of ears etc.
Some features display variation due to a mixture of inherited and environmental factors e.g. identical twins have
identical genes (inherited) and so look the same, but different diets may produce a fat twin and a skinny twin
(environmental).
VARIATION, CLASSIFICATION
& INHERITANCE
Variation & Inheritance
Selective Breeding
Natural Selection
Natural selection is the process whereby a species
evolves over time, inheriting the features best suited
to the environment in which the species lives. Over
time the best genetic features most useful for survival
and reproduction are passed on to their offspring.
Less useful features may be less evident eventually
and may even disappear altogether. Natural selection
may result in a species changing appearance or even
evolving into a new species, given enough time.
Artificial Selection
Artificial selection is where humans try to develop
particular varieties of animals or plants that display
useful characteristics. The animals or plants from
existing stock that show the best required
characteristics, are selected for breeding purposes. The
resulting offspring producing the best characteristics
are then used for breeding again - the process is
repeated until the exaggerated characteristics required
are obtained.
Examples of artificial selection:
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High yield milk or beef cattle
Disease or frost resistant crops
Pedigree dogs
Taxonomic Groups
Although species can be very different from each other, many of them have similar features that allow us to put them into groups. Putting different species into different
groups according to their features is called classification.
All living things can firstly be grouped into five kingdoms:
Each kingdom is then divided into further groups, e.g. breakdown of animal kingdom:
Protista
Animals
Monera
Living Things
Fungi
Vertebrates
Plants
Invertebrates
Fish -- Amphibians -- Reptiles -- Birds -- Mammals
Animals
Protista are single celled organisms
Monera are bacteria and blue-green algae
Annelids -- Arthropods -- Coelenterates -- Echinoderms -- Flatworms -- Molluscs
VARIATION, CLASSIFICATION
& INHERITANCE
Classification
Using Keys for Identification
A key is a list of clues and answers for identifying
which species an organism is. Take one organism at
a time and work through the questions for that
organism only until you end up with the name of the
species.
Here is a simple example:
Features of Vertebrates
Vertebrate group
Q1. Does it have a backbone?
Yes...Go to Q.3
No....Go to Q.2
Q2. Does it have legs?
Yes...Itʼs an ANT
No....Itʼs a WORM
Q3. Does it have fins?
Yes...Itʼs a FISH
No....Go to Q.4
Q4. Does it have feathers?
Yes...Itʼs a BIRD
No....Itʼs an ELEPHANT
Features
Fish
Scales, gills, fins, cold
blooded
Amphibians
Smooth, damp skin, lay
eggs in water, live on land
and in water, cold blooded
Reptiles
Dry scales, lay soft-shelled
eggs on land, cold blooded
Birds
Feathers on body, wings,
lay hard-shelled eggs on
land, warm blooded
Mammals
Hair or fur on body, produce
milk, give birth to live
young, warm blooded
Protecting the Environment
Habitats
It is important to protect the environment so that it continues to support all
the organisms that live in it. There are many ways that the environment can
be protected.
Changes caused by humans and their activities can be limited by
sustainable development. This involves making sure that any change in the
environment for the benefit of humans causes minimal damage to other
species and leaves sufficient natural resources to provide for the future.
The following are examples of sustainable development:
The place where an organism lives is called its habitat e.g. woodland, pond.
The conditions in a habitat are called the environment e.g. the temperature,
amount of rainfall etc.
Plants and animals develop certain features or characteristics over millions
of years, which allow them to live successfully in their habitats. These
features are called adaptations and we say that the living thing is adapted to
its habitat.
Depending on the habitats involved, living things have to adapt in different
ways.
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creation of nature reserves, where animals and plants are protected
from hunting and other human activities
reduction of pollution by using less fossil fuel and being ʻgreenerʼ in
everyday life (reducing carbon footprint)
protection of fish populations by setting fishing quotas, so limiting the
number of fish that can be caught
Factors Affecting Population Size
A population is the number of a particular species
in a habitat. All the different species of animals and
plants living in a habitat form a its community.
The organisms in a community compete for the
resources available i.e. animals compete for food,
water and space whilst plants compete for light,
water, space and minerals.
Animals that get more resources are more likely to
survive and their population to grow than animals
who get fewer resources.
Plants growing in a location that limits their
resources e.g. a small plant growing under a tree,
are less likely to survive than those growing in a
location with plentiful resources e.g. the same plant
out in the open. This is why you are less likely to
find a large population of small flowers such as
dandelions growing in a shaded, woodland area.
LIVING THINGS
IN THEIR ENVIRONMENT
Adaptation & Competition
Daily and Seasonal Changes
Some habitats do not stay the same all the time.
Examples of daily changes to the environment include:
• changes in light and temperature from day to night
• changes in water level, in accordance with tides
Examples of seasonal changes to the environment
include:
• changes in temperature and weather
• changes in hours of daylight
• changes in quantities of vegetation
Examples of organisms adapting to seasonal changes
include birds migrating, trees losing their leaves, animals
storing food, hibernation, animals growing thick coats
etc.
Examples of Adaptation
Here are some examples of organisms
adapting to their environments:
Camel
Camels live in deserts,
so they have to cope
with conditions that are
hot and dry during the
day and cold at night.
To c o p e w i t h t h e
environment camels
can store lots of water,
they lose very little water, they can cope with
large differences in temperature, they have
wide, flat feet to help them walk on the sand
and they have slit-like nostrils and two rows
of eyelashes to help keep the sand out.
Cactus
Cacti also live in deserts and so cope with
the environment by having no leaves and a
small surface area to reduce water loss, they
store water in their stems, they have shallow
but long roots to absorb water quickly and
they have spines to protect themselves from
being eaten by herbivores.
Polar Bear
Polar bears live in the arctic and are adapted
to arctic conditions by having black skin to
absorb heat well, they have a white
appearance for camouflage, they have thick
layers of fat and fur for insulation and they
have big feet to spread the weight on snow
or ice.
Food Chains
Food Webs
A food chain shows the different organisms that live in a habitat, and what eats what. Food chains
always start with a producer, which is an organism that makes its own food, and end with a consumer,
which is an animal that eats a plant or another animal.
A food web is made up of all of the food
chains in a habitat linked together.
Periwinkle
Moth
Frog
Snake
Hawk
In the above example of a food chain, the periwinkle is the producer, because it makes its own food
(through photosynthesis), the moth is the primary consumer (and is a herbivore), the frog is the
secondary consumer, the snake is the tertiary consumer and the hawk is the top carnivore or top
predator (at the top of the food chain). The arrows mean ʻis eaten byʼ.
A predator is an animal that eats other animals,
and the prey is the animal that gets eaten by the
predator.
LIVING THINGS
IN THEIR ENVIRONMENT
Feeding Relationships
Accumulation of Toxins in Food Chains
Toxins are poisonous materials, some of which break down quickly into harmless substances in the environment.
Other types of toxins do not break down and instead accumulate in the food chain and damage the organisms in it,
and in particular the top carnivores.
A toxin entering the food chain at the lowest level may seem to have a very low concentration, but as the larger
organisms higher up the food chain eat more and more of the contaminated organisms lower down, so the
concentration of toxins builds. Over time, the concentration of toxins in the top carnivore is high, as this organism
has eaten many of the consumers below it in the food chain. Examples of this accumulation of toxins can be seen in
food chains affected by substances such as mercury (in some paints) and the insecticide DDT.
Plant plankton contaminated by mercury pass on their contamination up the food chain - plant plankton are eaten by
animal plankton, which are eaten by small fish. Larger fish e.g. tuna eat the small fish. These top carnivores contain
a high level of mercury from all of the organisms eaten below them in the food chain. Mercury damages the nervous
and reproductive systems of organisms.
A similar thing happens when insects containing DDT are eaten by small birds which are eaten by larger birds. The
DDT weakens the eggs of the top carnivore which could lead to them dying out. DDT is now illegal to use.
Problems in one part of the food web can
give rise to strange ʻknock-onʼ effects in the
rest of the web. For example, in the above
food web, if a chemical was used to kill off
the insects feeding on the plants, frogs may
die out in the habitat as they have no food.
Snakes would have less frogs to eat so they
would eat more rabbits which would leave
less food for foxes. There would be fewer
hawks as their food supply would be less,
and so on. The ʻknock-onʼ effects of killing off
the insects in this food web are huge.