Edexcel A level Biology B Student Book 2 ActiveBook
I remember writing these notes in Y12, I know first hand the amount of time that has to be invested into this subject and how difficult it can be to identify the key information. These notes are time savers, giving you more time to practice questions and past papers. The notes used for all my A-lev...
Asexualreproduction
Asexual reproductionresults ingeneticallyidentical clones It does notrelyonfinding
mate and can reproducerapidly
A change inlivingconditions such as temperature or a newdeseasemaycause the
destruction of a groupof identicalorganisms it one can tcope the otherwill noteither
Producingspores
Sporationinvolves mitosis and the production of sexual spores that are capable of
growing into new individuals Theyusually survive adverse conditions and are
easilyspread
Most commonly found in fungi and plants such as mosses and ferns
Regeneration
When an organismreplacesparts of thebody that have been lost
Fragmentation The process of reproducing asexually fromfragmentsof their
originalbody
Certain starfish flatworms filamentous algae and sponges can regenerate
from pieces of their oldbody
Producingbuds
Buddinginvolves an outgrowth from the parentorganism that produces a smalle
but identical individual Producedpurelyby mi otic cell division
least cells and Hydrareproduce this way
New plant structures
vegetativepropagation Process of a plantforming a structure that develops
into a new plant that will eventually become independent
The new plant may be propagated from the stem leat bud or root of thepare
This processonly involves mitotic cell division It often involves perennating
organsThey contain stored food from photosynthesis and can remain
dormant in the soil to survive adverse conditions E g bulbs corms runners
EEspringwill have the same characteristics as parent can be good or bad
a In
complex animal organisms cells tend to become specialised and the rore
asexual reproductionis much less common
Farmersmay induce segmentationbytaking a small piece o a plant and
planting it somewhere else this allows mitosis to happen
Asexual
reproduction
byvegetative
µ
, Controlling viral infections
Thespreadof viraldeseases
a viruses can spread
through mucus dropletsof saliva faeces orsimple contact
International travel helpsviruses to spread from areas to countries and worldwide
Foot and mouth desease is a serious desease of cloven hoofed animals It is
spreadthroughbodysecretionssuch as milk and semen and through breath
and faeces of infected animals
In 2001 there was anepidemicin the uk and no treatment was available
so all infected animals were burnt to stop the spread of the desease
Ebola is an ilmescaused by the Ebola virus it is an animaldesease that spreads to
humans through the faeces urine blood and meat of infected animals It then
spreadsfrom person to personby direct contact oe skin or mucousmembrane
of a healthyperson with blood faeces or bodysecretions of an infected person
Averagemortality rate in humans is soy this mayvarydependingon
the strain of the virus the health of the person and the speed with
which theygetsupport
Treating vira deseases
Bacterialdeseases can be treated with antibiotics thesedrugsaffect bacterial
cell walls in one way or another
Antiviral treatments target virus replication
Theytarget the receptors by which viruses recognisetheir host cells
Target theenzymes that help to translate or replicatethe viral DNA or RN
i inhibit the
proteaseenzymes that enable new virus particles to bud
From the host membranes
scientist have
onlybeenyetable to reduce the time a person gets sick anddela
the developmentoe simptoms after infections
Vaccinations
After beingvaccinated against a virus you become inmune to it
Usually healthcare workers the veryyoungand the elderlyare vaccinated first
We have not yetdeveloped fully tested vaccinesagainst some of the worst
viral infections such as HIV AIDS and Ebola
Development of new medicines
New medicinetake up to loyears
Chemicals o medicines have to go
throughthoroughresearch safety
analyses and molecular modifications
followed by animal testing
This is then followed by three
phases of human testing to
ensure safety and that thedrug
works well
All these processesgoaccompanied
by complexregulationsand licensing
procedures
, Disease control
An epidemic is when the levels of people with a particular desease are much
higher than expected over a givenperiod of time When there is a vaccine availab
this is the time for mass vaccination of vulnerable peoplealongside measures
to prevent the spread of disease
When there is novaccine identifyingthe pathogenearly and putting control measur
are key
Stepsto control virusspread
1 Rapid identification of disease
2 Nursing in isolation isolation units are
rarely available indeveloping countries
Lack of infraestructura makes it difficult
to isolate infected people
3 Preventing transmission between people
through hand washing care inhandling
bodyEl vids and wastes careful disposal
of them and frequentdisinfecting of
surfaces and people
4 Sterilising or disposing ofequipment
and bedding after use
5 Protectiveclothing for health workers
wear face masks gowns gloves and
goggles to protecteyes Gloves and hands should be then
washed and disinfected after use
6 Identifying contacts People in contact with infected ones hav
to be isolated and monitored in case they show signsof disc
Speeding up medicinecreation
When an epidemicdevelops final stages of the testing of new medicines may
be speededup to try to save lifes
ZMapp an experimentaldrugproduced after long term studies of peopl
who had survived Ebola Scientists genetically modified tobacco
plants to produce three antibodies associated with surviving thedesea
Although it's trials on humans hadn't finished it was given to 7
people with Ebola to test it
Ethical implications
it is considered completely unethical to giveanyone a medicine or vaccine
that had not been through the entire process of testing and approval
Decisions may be made to use drugs that are only part waythrough the
Eviltesting process
There are factors to be evaluated to decide it a medicine should be
East tracked
Severity of the desease
Availabilityof other treatments
Transparency about the process
Informed consent of those giventhe treatment
Freedom of Choice over participation
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