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Biology Unit 1
B1
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1
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If someone is
malnourished, their diet is not balanced and would cause them to either be
over/underweight
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The amount of exercise you do affects the amount of energy you use up
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The more you exercise you do, the more food you
need to take in
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When the
amount of energy being taken in by food is less than the amount of energy your body uses
(exercise) you’ll lose weight
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They make bigger muscles-and muscle tissue burns up much more energy than fat does
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People need different amounts of energy in their diet because of this as the rate
of energy for chemical reactions varies between different people
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Men generally have a higher proportion of
muscle to fat than women so they have a higher metabolic rate
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Exercise alone also can increase you metabolic rate
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Cholesterol- You make this in the liver and it gets carried around your body in your blood
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High levels of cholesterol in the blood can
be bad and increase the risk of heart attack as it can block your blood vessels
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Unfortunately the
amount of cholesterol in your blood for some people is uncontrollable as it’s inherited from
parents and it may be at a high amount what you’re born with and can’t change
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1
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There are 3 major types of
pathogens including; bacteria, virus and fungi
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They come in many shapes and sizes, but even
the largest are only 10 micrometres long - 10 millionths of a metre
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Once inside the
body, they release poisons or toxins that make us feel ill
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Viruses are many times smaller than bacteria
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Viruses can only reproduce inside host cells, and they damage the cell
when they do this
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Eventually the virus copies fill the whole
host cell and burst it open
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Diseases caused by viruses include: influenza – flu, colds
and measles

Bacteria and viruses cause disease because once they’re inside your body they rapidly
reproduce
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However they often produce toxins which basically
poison your body- sometimes they directly damage your cells
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They very rarely produce
toxins
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White blood cells often produce antibodies which locate a
pathogen and try to connect to it
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Many antibodies will have to be tested until one fits, which causes it to
connect onto the pathogen it pulls it apart, killing it
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This is like what happens with vaccinations… Either dead or inactive pathogens are injected
into your body, which is viewed as a threat to your body- despite not being able to cause
harm
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Then your white
blood cells spend time figuring out the right antibody to fit onto the pathogens antigen and
this correct antibody is remembered by your memory cell
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E
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MMR vaccine (mumps,
measles, rubella)
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They died from childbed fever but no one knew what caused it
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Then a doctor died after cutting himself whilst
working with a dead body and had the same symptoms as childbed fever
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Painkillers- Painkillers helps to relieve the symptoms of an infectious disease, but they do not
kill the pathogens involved
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Antibiotics- Antibiotics are substances that kill bacteria or stop their growth
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It is difficult to develop
drugs that kill viruses without also damaging the body’s tissues
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He noticed that
some bacteria he had left in a Petri dish had been killed by naturally occurring penicillium
mould
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Different antibiotics work in different ways
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When antibiotics are taken too much it’s possible for bacteria to turn resistant to the
antibiotics and survive it
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MRSA- Hospitals treat many patients with infectious diseases, included one called MRSA
(methicillin resistant staphylococcus aureus)
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This is what happened here and in hospitals where patients are moved aboutallowing it to spread easily
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Producing Microorganisms- Petri dishes must be sterilised to kill unwanted microorganisms in
it, inoculating loops used to transfer microorganisms to it must be sterilised by being passed
through a flame, the lid of a petri dish must be sealed with tape to prevent microorganisms
from escaping or entering
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However in industry with
better equipment (when you can control conditions more) you can go to higher temperatures
as it produces more rapid growth and is safer
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2 Nerves and Hormones
The nervous system allows the body to respond to changes in the environment in a process
usually coordinated by the brain
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Cells called receptors detect stimuli (changes in the environment):
Receptors are groups of specialised cells that can detect changes in the environment called
stimuli
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Each
organ has receptors sensitive to particular kinds of stimulus
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The human central nervous system (CNS) consists of the brain and spinal cord
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The brain then coordinates the response
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They
often involve sensory, relay and motor neurones and no brain
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There are three
different types of neurones, each with a slightly different function:





sensory neurones carry signals from receptors to the spinal cord and brain
relay neurones carry messages from one part of the CNS to another
motor neurones carry signals from the CNS to effectors
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Signals cross this gap using
chemicals, and in order to do this- the original electrical impulse through the nerve is
transferred into chemical energy
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The
chemical diffuses across the gap and makes the next neurone transmit an electrical signal
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In a simple reflex action:
stimulus → receptor → sensory neurone → relay neurone → motor neurone → effector
Reflex actions are rapid and happen without us thinking
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This is what happens:
1
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Sensory neurone sends impulses to relay neurone going to the central nervous system
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A chemical is then released at the synapse between a relay neurone and motor neurone
in the central nervous system and the motor neurone sends impulses to effector
4
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B1
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2 Control in the Human Body
Homeostasis is about controlling body conditions and amounts of hormones in the body
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We need water for all the body’s chemical reactions and we can gain it from food
and drink
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We gain this from some drinks and food
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Temperature
increases in a hot day, or if exercise is done
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■ Blood sugar levels – to provide the cells with a constant supply of energy
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We lose blood sugar by sweating and insulin
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Hormones are secreted by glands and are usually transported to their target organs by the
bloodstream
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For example, the
monthly release of an egg from a woman’s ovaries and the changes in the thickness of the
lining of her womb are controlled by hormones secreted by the pituitary gland and by the
ovaries
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If pregnancy does not happen, the lining is
shed at menstruation
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These hormones are
secreted by the ovaries and pituitary gland
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FSH makes two things happen:




it causes an egg to mature in an ovary
it stimulates the ovaries to release the hormone oestrogen
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Oestrogen makes two things happen:


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it stops FSH being produced - so that only one egg matures in a cycle
it stimulates the pituitary gland to release luteinizing hormone (LH)
This diagram shows how the level of oestrogen changes during the menstrual cycle
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Hormones Controlling Fertility
There are 2 types of hormones in controlling pregnancy:



Stopping Pregnancy- e
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pill
Encouraging Pregnancy- e
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ivf

Stopping Pregnancy- The first oral contraceptives reducing chances of pregnancy had high
doses of oestrogen to inhibit FSH production- because this prevents a mature egg from
developing
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After development they used lower doses of oestrogen and instead more
progesterone as they have less side effects
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In IVF women are given are fertility drug at first, enabling them
to produce and release several mature eggs
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They are then fertilised by a man’s
sperm in which you wait for the egg to develop into an embryo (small ball of cells)
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B1
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3 Control in Plants
Plants produce hormones and respond to external stimuli, growing towards sources of water
and light, which they need to survive
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Plant hormones are used in
weed killers, rooting powder and to control fruit ripening
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Phototropism is a tropism where light is the stimulus
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The roots and shoots of a plant respond differently to the
same stimuli
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The tropisms of roots mean that the roots are likely to grow into the soil, where there is
moisture
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Auxins are mostly made in the tips of
the shoots and roots, and can diffuse to other parts of the shoots or roots
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Shoots and roots respond
differently to high concentrations of auxins:




cells in shoots grow more
cells in roots grow less
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This means that the shaded side grows
longer, causing the shoot to bend towards the light, this part with auxin grows fast
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No auxin is produced and the shoots do not grow
longer
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Auxin is in the same
concentration on both sides of the shoots, so they grow evenly and longer on
both sides
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Auxin is in a greater
concentration on the shaded side, causing the cells there to grow longer than the
cells on the lit side
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In a root, the shaded side contains more auxin,
but this time the shaded side grows less than the lit side
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Gravitropisms
Auxins are also involved in gravitropisms
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This makes the bottom side grow less than the top
side, causing the root to bend in the direction of the force of gravity
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This
makes the bottom side grow more than the top side, causing the shoot to bend and grow
against the force of gravity
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Weed Killers- In this process high dose of auxins are sprayed on plants like dandelions
and this causes accelerated growth
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B1
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Medical drugs relieve
disease and illness, and are extensively tested before being used
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Cannabis and heroin are illegal recreational drugs that are
very addictive
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3
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There are three main stages of testing:
1) The drugs are tested using computer models and human cells grown in the laboratory
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This
is to test the toxicity
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In the UK, new medicines have
to undergo these tests, but it is illegal to test cosmetics and tobacco products on
animals
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3) Drugs that have passed animal tests are used in clinical trials
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Very low doses of the drug are given to
begin with
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Then further clinical trials occur and people are offered two types of pills, one containing
medication and one blank- this is a placebo
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Double blind trials aim to minimise the placebo effect
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A placebo is designed to appear exactly the same as the drug
itself, but it does not actually contain any of the drug
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Then
approval may be gained if it’s successful
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Thalidomide
Thalidomide was developed as a sleeping pill, but it was also thought to be useful for easing
morning sickness in pregnant women
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The drug was then banned
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More recently, thalidomide has been used successfully in the treatment of leprosy and other
diseases
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As they get happy it creates as sense of euphoria
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They still have negative effects; they’re addictive, cause
withdrawal symptoms, and have a large effect on society as many people take them
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They’re highly addictive and have
severe withdrawal symptoms
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Cannabis- This drug is especially bad as it’s viewed as a ‘gateway’ drug, this is because
consumers take this before leading onto harder drugs like ecstasy
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People believe legal drugs have a worse effect as they’re more available and more people
consume them
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Heroin and cocaine
are very addictive
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Some drugs are capable of artificially
improving their performance; these include:


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stimulants – these boost heart rate and other body functions
anabolic steroids – these stimulate the growth of muscles
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Others are legally available on prescription or even
in some medicines available from the pharmacy
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They may also damage the athlete’s body
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B1
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Population size depends
on a variety of factors including competition, predation, disease and human influences
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B1
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1 Adaptions
Organisms live in different habitats need different adaptations
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To survive and reproduce, organisms
require a supply of materials from their surroundings and from the other living organisms
there
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Habitats have limited amounts of the resources needed by living
organisms and organisms can only survive if they can get enough of these resources, so they
must compete for resources with other organisms
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They may be tolerant
to; high salt levels, high temperatures and high pressures
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Animals may be adapted for survival in dry and arctic environments by means of:
■ changes to surface area
■ thickness of insulating coat
■ amount of body fat
■ camouflage

In Cold Conditions- e
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Polar Bear





White fur to be camouflage
Thick layers of fat and fur for insulation against the cold
Small surface area to volume ratio to reduce heat loss
Small ears to reduce skin exposed to air, to reduce heat loss by radiation

In Hot Conditions- e
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Camel





Large surface area to volume ratio to increase heat loss
Thick fur on top for shade, but thin elsewhere to cool down
Large flat feet so they stay on top of the sand
Large, thin ears to lose lots of heat by radiation

Plants
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g
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In addition, cacti have spines instead of leaves
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The spines also protect the cacti from animals
that might eat them
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B1
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2 Environmental Change
Non-living and living factors can affect the distribution of organisms in an area and cause
environmental change:
Living- Competition, predators, disease
Non-Living- Temperature, nutrients, rainfall, pollution
Living organisms can be indicators of pollution:



Lichens can be used as air pollution indicators, particularly of the concentration of
sulphur dioxide in the atmosphere- and they don’t grow where there’s lots
invertebrate animals can be used as water pollution indicators and are used as
indicators of the concentration of dissolved oxygen in water

Environmental changes can be measured using non-living indicators such as oxygen levels,
temperature and rainfall
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The depth of rain is usually
measured daily, for example at the same time every morning
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Oxygen levels in water can be measured using oxygen probes
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B1
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5
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Green plants and algae absorb a small amount of the light that reaches them
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This energy is stored in
the substances that make up the cells of the plants
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When predators consume these
plants, some of this energy is transferred
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Pyramids of biomass reveal the
mass of living material at each stage in a chain
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The arrows between each item in a food chain always
point in the direction of energy flow - in other words, from the food to the feeder
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B1
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6
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Materials from living things decay because they are digested (broken down) by
microorganisms
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Bacteria and fungi are the main groups of decomposer
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Microorganisms are more active and digest materials faster when they are in moist, warm
and aerobic conditions
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In a stable community of living things, processes that return substances to the
environment (such as decay) are balanced by the processes that remove and use substances
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B1
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2 The Carbon Cycle

The carbon from the carbon dioxide gained from photosynthesis in plants is used to make
carbohydrates, fats and proteins, which make up the body of plants and algae
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B1
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7
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Sexual reproduction produces offspring that resemble their
parents, but are not identical to them, due to passing on characteristics in the genes from
gametes
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A gene is a section of DNA,
which carries coding for a particular protein
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Many genes are needed to carry all the genetic
information for a whole organism
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Differences in characteristics may be due to genetic factors, environmental factors of both
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7
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The mixture of the genetic information from two
parents leads to variety in the offspring
Asexual- This involves 1 parent and there is no fusion of gametes
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These genetically
identical individuals are known as clones
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A branch from the
parent plant is cut off, its lower leaves removed and the stem planted in damp compost
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The cutting is usually covered in
a clear plastic bag at this stage to keep it moist and warm
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The method is easy
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Tissue Culture: Another way of cloning plants is by tissue culture,
which works not with cuttings but with tiny pieces from the parent
plant
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This makes tissue culture more expensive and difficult
to do than taking cuttings
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Embryo Transplants: This involves allowing an egg cell to become fertilised in a Mother until
it becomes an embryo
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The cells are
separated from one another
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When the offspring are born, they are identical to each other and genetically related to the
original pregnant animal
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Adult Cell Cloning:
1)
2)
3)
4)
5)

the nucleus is removed from an unfertilised egg cell and discarded
the nucleus is removed from an adult body cell and injected into the egg cell
an electric shock is applied to make the egg cell begin to divide to form an embryo
while it is still a ball of cells, the embryo is inserted into the womb of an adult female
the embryo continues to grow and develop

The new individual is genetically identical to the animal that donated the nucleus from one of
its body cells
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This means that the new organism
with the inserted genes has the genetic information for one or more new characteristics
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Genetic modification can be used in insulin production- firstly a human cell is taken, and with
a particular enzyme the insulin production gene is removed
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Then the bacteria can be placed
in a vat to reproduce asexually, and the insulin can be removed from them and given to
people with diabetes
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For example, new genes
can be transferred to crop plants to make GM crops so the grow with desired characteristics
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Once these crops have been genetically modified, generally they have higher
yields as they’re protected by new genes inserted
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However
some people believe the process is unethical and should be banned
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B1
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Over time
simple organisms had evolved into more complex creatures, more adapted to survival
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He knew that with-in species there was genetic variation- and he
noticed that some of these variations provided this creature with an advantage
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This process is natural selection, and the stongest creatures within a species survive the competition
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Darwin’s theory wasn’t immediately accepted
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Jean-Baptiste Lamarack
He had his own belief on evolution and it contrasted that of Darwins, his turned out to be
false
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A characteristic which is used more and more by an organism becomes bigger and
stronger, and one that is not used eventually disappears- e
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in the lifetime of a
giraffe as it stretches more to reach higher food, it’s neck increases in length
2
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E
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these new giraffe offspring apparently also would have longer necks

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