All of AQA BIOLOGY Paper 2 in 25 minutes - GCSE Science Revision
Summary
TLDRThis video script offers a rapid overview of AQA Biology Paper 2, covering topics 5 to 7 including homeostasis, response, inheritance, variation, evolution, and ecology. It explains the body's regulatory mechanisms, nervous system functions, and hormone roles, while also delving into eye function, thermoregulation, and reproductive processes. The script touches on genetics, meiosis, and DNA's role in evolution and adaptation. It concludes with ecology, discussing ecosystems, biodiversity, and environmental impact, providing a comprehensive review for exam preparation.
Takeaways
- 🌡️ Homeostasis is the process by which organisms maintain internal balance despite external changes, crucial for optimal enzyme activity and chemical reactions.
- 🧠 The nervous system, including the CNS and PNS, plays a key role in detecting changes and initiating responses, with reflexes providing rapid, subconscious reactions.
- 🔬 Hormones, produced by the endocrine system, are chemicals that regulate various body functions through slower signals via the bloodstream compared to the nervous system.
- 👀 The eye's structure allows for accommodation, adjusting the lens to focus light on the retina, and different cells in the retina respond to light, enabling vision.
- 🌡️ Thermoregulation involves the body's mechanisms to control internal temperature, such as sweating and shivering, to maintain a stable environment for bodily functions.
- 🚰 Kidneys maintain water and nitrogen balance in the body, filtering blood and regulating water levels, with antidiuretic hormone (ADH) influencing water reabsorption.
- 🌱 Plant hormones, like gibberellins and ethylene, influence growth, germination, and fruit ripening, and can be utilized in agriculture for various purposes.
- 🔬 Inheritance involves the creation of gametes through meiosis, introducing variation in offspring, which can be beneficial for survival and adaptation.
- 🧬 The human genome project mapped out genes in the DNA, which is crucial for understanding genetic diseases and inherited disorders.
- 🧬 Epigenetics shows that DNA can respond to the environment, influencing gene expression without changing the DNA sequence itself.
- 🌿 Ecology examines the interactions among organisms within an ecosystem, considering both biotic and abiotic factors, and the importance of biodiversity for ecosystem stability.
Q & A
What is the main concept of homeostasis in biology?
-Homeostasis is the process by which an organism maintains a constant internal environment despite changes in external conditions, allowing optimal rates for crucial chemical reactions, such as those involving enzymes.
How does the nervous system contribute to homeostasis?
-The nervous system, consisting of the central nervous system (CNS) and the peripheral nervous system (PNS), helps regulate internal conditions by sending electrical signals in response to stimuli, which can trigger actions like moving away from a hot surface to maintain body temperature.
What is a reflex arc and how does it differ from a conscious decision?
-A reflex arc is a neural pathway that allows for a rapid, automatic response to a stimulus without the involvement of the brain. This is different from a conscious decision, which involves the brain processing the signal and making a deliberate choice before acting.
Can you explain the role of hormones in the endocrine system?
-Hormones are chemical messengers produced by glands in the endocrine system. They travel through the bloodstream to various effectors in the body, influencing functions such as growth, metabolism, and the body's response to stress.
How does the body regulate blood glucose levels?
-The body regulates blood glucose levels through the actions of insulin and glucagon, hormones produced by the pancreas. Insulin promotes the uptake of glucose into cells, while glucagon stimulates the conversion of glycogen into glucose when levels are too low.
What is the significance of the different parts of the brain in terms of function?
-The cerebral cortex is responsible for higher-level functions like memory and problem-solving. The cerebellum controls motor skills and coordination. The medulla oblongata manages unconscious actions such as heart rate and breathing, and it also controls the release of adrenaline.
How does the eye accommodate to different distances?
-The eye accommodates to different distances by changing the shape of the lens, controlled by the ciliary muscles and the suspensory ligaments. For distant objects, the muscles relax, making the lens thinner and less refractive, while for close objects, the muscles contract, making the lens thicker and more refractive.
What is the process of meiosis, and why is it important for sexual reproduction?
-Meiosis is a type of cell division that results in four haploid cells, each with half the number of chromosomes of the original cell. It is crucial for sexual reproduction because it produces genetic variation in offspring, which can lead to traits that are better suited to the environment.
Can you describe the role of the pituitary gland in the endocrine system?
-The pituitary gland is often referred to as the 'master gland' because it produces hormones that regulate other glands in the endocrine system. It responds to various stimuli and releases hormones that trigger other glands to produce specific chemicals, such as insulin from the pancreas or thyroxin from the thyroid.
What is the difference between type 1 and type 2 diabetes?
-Type 1 diabetes occurs when the pancreas cannot produce enough insulin, often requiring insulin injections for management. Type 2 diabetes is a condition where the body's cells become resistant to insulin, often requiring dietary changes and, in some cases, medication to help manage blood glucose levels.
How does the concept of negative feedback relate to homeostasis?
-Negative feedback is a biological process that helps maintain homeostasis by counteracting changes and bringing conditions back to normal. For example, if body temperature rises, the body responds by sweating and vasodilation to dissipate heat and restore the normal temperature.
Outlines
🔬 Homeostasis and Nervous System
The first paragraph introduces the concept of homeostasis, which is an organism's ability to maintain internal balance despite external changes. It discusses the role of the nervous system, including the central nervous system (CNS) and peripheral nervous system (PNS), in regulating conditions like blood glucose, temperature, and water levels. The paragraph explains the process of sensory input, signal transmission through synapses, and reflex actions. It also covers the impact of stimulants and depressants on reaction times and the structure and function of the human eye, including accommodation and the roles of different cells in vision. Additionally, it touches on thermoregulation, the importance of the brain's parts, and the use of MRI scans for brain imaging.
🌡 Endocrine System and Thermoregulation
This paragraph delves into the endocrine system, highlighting its role in hormone production and the influence of hormones on the body's functions. It explains how the pituitary gland acts as the 'master gland' and discusses the functions of other glands like the pancreas, thyroid, adrenal glands, and reproductive organs. The paragraph also covers the regulation of blood glucose levels through insulin and glucagon, the conditions of type 1 and type 2 diabetes, and the importance of water and nitrogen balance. It further explains the kidney's role in maintaining water balance through the production of urine and the function of antidiuretic hormone (ADH).
🌱 Hormones and Plant Growth
The third paragraph focuses on the hormonal responses in plants, including the effects of gibberellins, ethylene, and auxins on seed germination, fruit ripening, and plant growth direction. It describes how these hormones can be used in agriculture and as weed killers, and how they influence plant growth through processes like phototropism and geotropism. The paragraph also suggests a mini-investigation using a Petri dish to demonstrate geotropism and concludes with an introduction to the topic of inheritance, variation, and evolution.
🧬 Inheritance, DNA, and Genetic Variation
This section explores the principles of inheritance, starting with the process of meiosis in creating gametes and the role of genes in producing variation in offspring. It explains the concepts of genotype and phenotype, the structure of DNA, and the process of transcription and translation. The paragraph discusses the significance of nuclear bases and how they code for amino acids to form proteins. It also touches on harmful mutations, epigenetics, and how characteristics can be controlled by single or multiple genes, including the use of Punnett squares to predict genetic outcomes.
🐯 Evolution, Species, and Genetic Modification
The fifth paragraph examines Charles Darwin's theory of evolution and how random variation can lead to better adaptation and survival. It discusses Lamarck's theory and its relation to epigenetics, the concept of species and reproductive compatibility, and the use of selective breeding and genetic modification in producing desired traits in organisms. It also covers the process of genetic engineering, the importance of biodiversity for a stable ecosystem, and the impact of human activities on the environment and biodiversity.
🌿 Ecology, Biomass, and Environmental Impact
The final paragraph discusses the field of ecology, which studies the interactions among organisms within an ecosystem. It covers the concepts of competition, interdependence, and the roles of abiotic and biotic factors. The paragraph explains the use of quadrats and transects for population studies, the structure of food chains and trophic levels, and the importance of biomass and energy flow. It also addresses issues like deforestation, biodiversity loss, and the environmental impact of human activities, including waste management and greenhouse gas emissions. The paragraph concludes with a discussion on food security, sustainable fishing practices, and the challenges faced by modern agriculture.
Mindmap
Keywords
💡Homeostasis
💡Nervous System
💡Receptor
💡Neurotransmitter
💡Hormones
💡Thermoregulation
💡Meiosis
💡Genotype and Phenotype
💡Dominant and Recessive Alleles
💡Evolution
💡Genetic Modification
💡Ecology
💡Food Chain and Trophic Levels
💡Biodiversity
💡Genetic Engineering
💡Cloning
Highlights
Homeostasis is an organism's ability to regulate internal conditions despite external changes, essential for optimal enzyme activity.
The nervous system, including the CNS and PNS, plays a crucial role in detecting changes and responding to maintain homeostasis.
Reflexes are faster responses that bypass the brain and are mediated by the spinal cord.
Glands can act as effectors, producing chemicals needed by the body in various situations, such as saliva production.
Reaction times can be investigated by measuring the distance a ruler falls before being caught, potentially affected by stimulants or depressants.
The brain has three main parts: the cerebral cortex for higher functions, cerebellum for motor skills, and medulla oblongata for unconscious actions.
MRI scans provide a safe way to observe brain activity, but treating brain issues can be challenging.
The eye's accommodation allows it to focus light from objects at varying distances by changing the lens shape.
Thermoregulation involves the body controlling its temperature through various mechanisms, such as sweating and shivering.
The endocrine system uses hormones to regulate various body functions, with the pituitary gland being considered the 'master gland'.
Type 1 and type 2 diabetes are conditions related to insulin production and glucose absorption, respectively.
Water and nitrogen balance are critical for the body, with kidneys playing a key role in maintaining these balances.
Reproduction involves a complex hormonal cycle in females, with menstruation marking the maturation of eggs.
Inheritance, variation, and evolution are central to understanding how traits are passed down and how species adapt over time.
Genetic modification and selective breeding are methods used to introduce desired traits in organisms, with applications in medicine and agriculture.
Ecology examines the interactions between organisms in an ecosystem, considering both biotic and abiotic factors.
Food chains and webs illustrate the flow of energy and biomass through an ecosystem, with producers, consumers, and decomposers.
Biodiversity is crucial for ecosystem stability, and human activities can have significant impacts on it.
Food security and sustainable fishing practices are important for maintaining healthy ecosystems and ensuring long-term food availability.
Transcripts
let's see how quickly we can cover
everything you need to know for AQA
biology paper 2 this video is good for
higher and Foundation Tier double
combined Trilogy and triple or separate
biology that is topics 5 to 7 that's
homeostasis and response inheritance
variation in evolution and ecology I'll
tell you when something is just for
triple but not when something's just for
higher tier because there's not much
difference to be honest we're going to
be moving hecking fast so pause the
video if you need a bit more time to get
your head around something you see let's
go homeo stasis is the term given to an
organism's ability to regulate internal
conditions even when external conditions
change this is important so that crucial
chemical reactions involving enzymes can
happen at an Optimum rate amongst other
things our bodies work hard to regulate
blood glucose concentration temperature
and water levels for example one way
that our body achieves this is with our
nervous system it consists of the CNS
that's central nervous system that's the
brain and spinal cord and the pns
peripheral nervous system the nerves
that go through the rest of the body a
receptor for example skin detects a
change due to a stimulus like a hot hob
an electrical signal travels to the
spine through sensory and relay neurons
nerve cells the signal travels across
the gap between these neurons called the
sinapse by a neurotransmitter chemical
once at the spine the signal can go to
the brain where you can make the
conscious decision to act the signal
then goes back to an affector like the
muscle in your arm via relay and motor
neurons so that you move your arm a
reflex is when the signal bypasses the
brain and goes straight through the
spine to the affector this is a reflex
arc this of course is much faster than a
conscious decision glands can also be
effectors which produce specific
chemicals your body needs depending on
the situation for example your salivary
glands in your mouth making saliva when
you eat food you can investigate into
reaction Times by holding the bottom of
a ruler between a person's finger and
thumb and drop it without warning then
you measure the distance it falls before
they catch it do this multiple times and
take mean average not too many times
though as their nervous systems will
start to get a bit better at reacting to
this you can introduce an independent
variable like a stimulant for example
coffee or a sugary drink or a depressant
which will have the opposite effect
although I can't think of any ones that
are legal for you at the minute to see
how they decrease or increase Reaction
Time respectively you could calculate
the reaction time from the distance
using suat S equal half 80 squ but
you'll never be expected to do that in
this paper but it's something you could
mention if you were asked a six mark on
this quite a bit that's just for triple
biology now that's the brain eye and
Thermo regulation skip to hormones if
you're doing combined Trilogy that is
double science there are three parts of
the brain you need to know the cerebral
cortex is responsible for higher level
functions like memory speech and problem
solving the cerebellum is responsible
for your motor skills movement balance
and coordination the medulla onata
controls unconscious actions your body
takes you don't think about them like
your heart and breathing rates it's also
what controls the release of adrenaline
MRI scans magnetic resonance imaging are
a way of seeing the activity in your
brain safely if something goes wrong
with your brain though it can be very
difficult or impossible to treat without
damaging important parts of it your eyes
are the most mind-bogglingly designed
cameras ever conceived of accommodation
is the ey's ability to change the shape
of the lens in order to focus light that
comes from objects that are different
distances away on the retina to focus
light that comes from objects that are
far away the ciliary muscles relax and
the suspensory ligaments Titan they're
both connected to the lens this results
in the lens becoming thin and that means
that light is only refracted a little
bit and that focuses the light on the
retina to focus on near objects the
opposite is true the sary muscles
contract the suspensory ligaments
slacken and the lens becomes fatter or
thicker and so that means that it
becomes more powerful actually so light
is refracted more which means that the
light coming from the object still
converges meets focuses on the retina so
you can see a clear image the pupil hole
in the iris can change size depending on
the light intensity hitting the eye the
cornea is the transparent outer layer
where light enters the eye it has a
slight lensing effect itself while the
White surface that covers the rest is
called the Scara the light is focused
then on the retina at the back of the
eye which consists of Rod and Cone
Styles which respond to light rods can
only detect light intensity so no color
while there are three different types of
cones which detect green blue or red
wavelengths of light a mix of which will
produce the colors we then perceive when
the signal reaches our brain via the
optic nerve myopia is the medical term
for shortsightedness you can't focus on
Far object hyperopia is long-sightedness
glasses or contact lenses are usually
used to mitigate this by slightly
converging or diverging the light before
it enters the eye laser eye surgery aims
to change the shape of the cornea to
achieve the same effect Thermo
regulation is your body controlling its
internal temperature by the brain
sensing blood temperature then sending
nervous and hormonal signals to various
effectors around your body in order that
your body loses heat to its surroundings
more slowly or quickly for example if
you're too hot sweat glands in your skin
cause water to cover the surface this
evaporates taking heat away from your
body quickly blood vessels also dilate
widen we call this vasod dilation to
increase blood flow to the skin to
increase the rate of heat loss too cold
we have Vaso constriction instead hence
why you go pale you also shiver which
causes your muscles to produce more heat
okay back to science goodness which is
for everyone the endocrine system is a
system of glands that produce or secrete
hormones that travel to effectors Via
the blood this is of course slower than
any signal carried by the nervous system
the pituitary gland in your brain can be
considered the main or Master gland as
it produces hormones in response to
stimuli that travel to other glands in
your body in order that they start then
producing certain chemicals examples are
the pancreas which produces insulin
we'll talk more about that in a bit the
thyroid controls all sorts of things
like growth heart muscle and digestive
function and more the adrenal glands
produce adrenaline and the ovaries in
testes release eggs or produce sperm
depending on which you have speaking of
the pancreas then it's involved in
making sure that your blood glucose
levels aren't too high or too low too
high and the pancreas secretes insulin
which causes glucose to move from the
blood into your cells to be used for
respiration any excess glucose can be
converted into glycogen to store energy
and that's done by the liver too low on
the other hand and the pancreas produces
another hormone called glucagon which
causes the liver and muscles to turn
glycogen back into glucose ready to be
used type one diabetes is what you have
when your pancreas can't produce enough
insulin and you have to take insulin
injections to do the job instead type
two is when your cells no longer absorb
the glucose as they should so you have
to be careful with your diet and if
you're overweight or obese you have a
much higher risk of developing this
water and nitrogen balance are triple
only so skip to the next topic reprodu
if youj just double your body loses
water when you exhale sweat or urinate
if your body has too much water let's
say for example you drink too much your
kidneys remove it from your blood at a
faster rate where it's mixed with Ura to
become urine Ura is made from ammonia
which is produced from excess proteins
broken down into amino acids by the
liver if that wasn't the case too much
water builds up in your body and too
much water would go into your cells by
osmosis and then they' become turgid and
burst too little water however and they
become flaccid didn't stop working
kidneys do a good job of keeping the
water balance just right kidneys also
filter your blood to absorb useful
substances like glucose and some ions
bit more detail about how the kidneys
work then antidiuretic hormone or ADH is
produced in the pituitary gland which
travels to the kidneys and it causes the
tubules in the kidney to reabsorb more
water into the bloodstream so less then
go to the bladder the water level is too
high less ADH is produced so the kidneys
cause more water to be lost in urine in
both cases the water level returns to
normal we call this negative feedback
the term negative feedback might sound
like it's bad but all it means is that
the body responds in such a way as to
return things to normal if your kidneys
aren't working properly dialysis is
required essentially your blood is sent
through a machine that does the same job
as your kidneys if this doesn't happen
the buildup of Ura will poison you okay
reproduction is for everybody well you
know what I mean menstruation occurs in
females after puberty eggs start to
mature first FSH that's follicle
stimulating hormone made by the
pituitary gland causes an egg to mature
in the ovary this also causes the
ovaries to produce estrogen which causes
the uterous lining to thicken it also
inhibits or stops the production of FSH
so that no more eggs mature in that
cycle very clever it also causes the
pituitary gland to produce LH lutenizing
hormone which causes the egg to be
released and it starts to travel towards
the uterus via the UCT over several days
finally progesterone is also produced by
the the ovaries which maintains the
uterus lining this is great news if
you're looking to get pregnant if not
you need to find some way of stopping a
sperm cell meeting an egg cell
contraception options include pills that
inhibit FSH production so no eggs mature
progesterone injections that stop any
eggs being released you can also have an
implant that slowly releases this over
months or years if needed condoms for
men and diaphragms for women are simple
barriers to stop sperm from reaching an
egg an IUD or intrauterine device like a
copper coil prevents a fertilized egg
from implanting in the lining you could
quite simply just avoid sex for some
time after the egg has been released as
that's when it travels slowly down the
UCT where a sperm can meet it clamping
the UCT sometimes refer to having your
tubes tide or cutting the sperm ducts
either of these will obviously stop the
cells meeting some couples however would
love to have children but can't due to
infertility sometimes it's something
fairly simple like not enough FSH or LH
produced which injects can fix the most
expensive solution to bigger issues is
IVF in vitro fertilization eggs are
harvested from the woman after inducing
their release and will then fertilize in
the lab with the prospective father's
sperm any embryos that develop are
inserted back into the uterus where they
will hopefully embed in the lining and
grow normally the success rate however
is very low but there is also the risk
that there could be more than one baby
born which might not be desirable we've
already mentioned it adrenaline is the
hormone that increases heart and
breathing rate in stressful situations
to prepare the body for fight or flight
thyroxin is another hormone that's
secreted by the thyroid and it controls
metabolic rate if thyroxin levels are
too low the hypothalamus in your brain
releases a hormone called TR you don't
need to know the full name and that
causes the pituitary gland to produce
another hormone called TSH so the
thyroid releases more thyroxin this
again is an example of negative feedback
the last triple content in B5 plants
also have their own hormones which we
can utilize when growing plants
gibberellins cause seed germination to
occur which we can add to seeds to give
them a wakeup call it also promotes
flowering and increases the size of
fruits ethine induces ripening of fruits
orins control chot and root growth it's
destroyed by sunlight so it gathers on
the Shaded side of a chute causing more
growth and elongation of cells on the
Shaded side so the Chute bends toward
the Sun or light source this is what we
called phototropism in however orins
inhibit growth the hormone gathers on
the bottom of a root and so that means
the top side grows more quickly causing
the root to grow downwards this is
called geotropism we can also use orins
as weed killers rooting powders and for
promoting growth in tissue cultures we
can do a mini investigation we can put
some seeds on damp cotton wool in a
Petri dish for example stand the petri
dish on its side leave for a few days
then turn 90° and you should see that
the roots have bent in that time proving
that geotropism is true for roots next
big topic B6 that's inheritance
variation and evolution in order to
reproduce sexually gametes sex cells
must be made this happens by meiosis for
example in the testes to make sperm the
chromosomes in a diploid cell that is 23
pairs for us are copied similar
chromosomes then pair up and the genes
are swapped between them the cell then
divides to make two diploid cells which
then divide again along with the
chromosomes themselves to make four haid
cells ready to fuse with another gamt
which in this case would be an egg this
is one way that variation occurs in
Offspring the resulting diploid cell
then starts to divide via mitosis which
is covered in paper one plants do this
with pollen and egg cells but they can
also reproduce asexually but as it
doesn't evolve gametes the daughter
cells will be genetically identical so a
clone of the parent is made by mitosis
an advantage of sexual reproduction is
that variation occurs which can result
in organisms becoming better suited to
their environment more in this in a bit
so more likely to survive an advantage
for asexual is that only one parent is
needed so for example a plant on its
Lonesome can still reproduce in order
for the species to survive another thing
that can do both is the parasite that
causes malaria as can some fungi genome
is the term given to all the genetic
material in an organism this code is
stored in DNA of course which is a two
stranded polymer in a double helix shape
a gene is a section of DNA that codes
for a specific protein the human Genome
Project completed its initial goal in
2003 when scientists mapped out what
every Gene is responsible for coding
this is powerful because it can help us
identify what genes cause diseases or
inherited disorders genotype is the term
given to what code is stored in your DNA
specifically while phenotype is how that
code is expressed in your
characteristics what proteins are made
it affects your physiology for triple
you need to know that the monomers
between the two strands are called
nuclear es and they're made from a sugar
and phosphate group of which there are
four types A T C and G you don't need to
know what the names are but a and t
always match to each other in the
sequence as do C and G every three of
these bases we can call them are a code
for an amino acid the sequence is copied
by mRNA this copy is then taken out of
the nucleus to a ribosome in the cell
where amino acids are connected in the
order needed which makes a protein the
shape of which affects His function they
need to be folded as well first harmful
mutations can change a gene so much that
it results in a protein being
synthesized that doesn't do the job it's
supposed to we now know that some DNA
however doesn't directly code for
proteins but it influences how other
genes are expressed this is the realm of
epigenetics and it's changing the way
that we view DNA quite drastically back
to double some characteristics are
controlled by just one gene like color
blindness these different types of the
same gene are called alal
usually characteristics are dependent on
two or more genes though and them
interacting dominant alals are those
that result in a characteristic being
expressed even if there is another alil
present a recessive alil for example if
you have the Al's Big B little B for I
color Big B be brown little B be blue
you will have brown eyes it's only when
there's no dominant alil in this case
that the recessive alil is expressed so
me having blue eyes I must have the gene
little be little B Big B Big B or little
B little be are called homozygous as
they only have one type of alil whereas
Big B little B is what we call
heterozygous we can use a punet square
to predict the probability of a certain
phenotype my parents have brown eyes but
they both have heterozygous Al for eye
color there are three different outcomes
of these combining with a 25% chance of
making me that's little be little be so
I'm not so much one in a million more
one in four my sister has brown eyes but
her son has blue eyes so she must be Big
B little B eye color is by the by but
some alals can result in disorders being
inherited for example polya extra
fingers or toes which is caused by a
dominant alil or cystic vibrosis which
is caused by a recessive alal even if
two parents don't have cystic fibrosis
they could still be carrying the
recessive alal so their child could have
the disorder human DNA is containing 23
pairs of chromosomes but only one pair
determines sex if you have XX
chromosomes you are female XY you're
male the expression of these genes
affects every cell in your body every
aspect of your physiology we can also
make a punet square for these as you can
see there's a 50/50 chance of a child
being male or female variation is a
result of the genes inherited from an
organism's parents and also
environmental factors Charles Darwin's
theory of evolution states that random
variation in Offspring will result in
some being better suited to their
environment than others and so are more
likely to survive and reproduce but like
see we know that our DNA is able to
respond to the environment in order to
turn genes on and off depending on
whether they're needed or not for
example there were some blind
translucent skin mackerel that were
found in a dark cave when they were bred
with normal mackerel in sunlight they
regained fully working eyes and opaque
skin within a few Generations John
Baptist Lamar's Theory asserted that
adaptation of variation is Guided by DNA
in response to a changing environment
this was scoffed at but we now know that
there is some truth to this thanks to
the discoveries made in epigenetics
bacterial resistance is largely
considered to be evidence of darwinian
evolution bacteria divides mutations
occur and inevitably a bacterium with an
increased resistance to antibiotics will
be produced that's why we only want to
use them when absolutely necessary it
also means you have to complete the
whole course of antibiotics if you don't
weaker bacteria will have been killed
off but more resistant ones will still
be there and then they'll reproduce and
make you even more ill if organisms are
able to produce fertile offspring we say
they're of the same species tigers and
lions have been known to make lier
Offspring but as they're infertile we
don't consider tigers and lions to be
the same species we can selectively
breed living things with desired
characteristics to enhance these for
example breeding dogs to produce breeds
like labador colleagues and if you're
into undesirable characteristics pugs
too advancements in biology over the
last few decades mean that we can also
genetically modify organisms if we don't
want to wait for selective breeding to
do the job or when it can't actually
achieve what we want it to for good or
ill for example scientists have
genetically modified bacteria to produce
insulin which can be harvested and used
to treat people with diabetes
genetically modifying crops is one way
of boosting their yields or nutritional
value for example golden rice has a gene
inserted into it that produces vitamin A
it was developed to combat diets in
certain areas that were lacking in this
other GM crops have been modified to be
more resistant to diseases for example
the process of genetic engineering goes
as follows a gene is chemically cut from
the organism that has the desired
characteristic this is done using
enzymes for example the gene from a
jellyfish that causes it to glow in the
dark this is then inserted into a vector
like a bacteria plasmid or virus that in
turn inserts the gene into another
organism say a bunny rabbit but it must
be done in the early stage of its
development say just after the YK has
been fertilized as this is the only way
you can be sure that the gene will be
present in every cell of the bunny as it
grows by the way I didn't make up this
example this has actually been done
fossils are the remains of organisms
that died a very long time ago the
classic fossils we think about are the
bones that we dig up but they're not
strictly speaking bones anymore in fact
minerals have replaced the organic
material to effectively leave Rock in
exactly the same shape as the bone
sometimes there can still be organic
tissue Left Behind if the conditions for
Decay are not present Footprints left in
mud that have hardened over time for
example are also considered fossils as
well as any other trace of an organism
it doesn't have to be the organism
itself cloning is triple only making
exact copies of plants is easy just take
cuttings off a plant put them in the
ground and that does the job you can
also go the slightly harder route by
cloning from a tissue culture that is
cloning from a small group of cells this
can be helpful for preserving some
species from going extinct cloning
animals is more difficult you can split
embryo cells up just after fertilization
than put them into surrogate mothers
essentially you're forcing identical
twins but you won't know exactly what
you're getting until they've developed
so if you have a fully grown animal that
you want to clone you take the nucleus
from one of its cells say in its skin
then insert that into another's egg cell
it's essentially now a fertilized egg
shocking the egg jump starts the
development process and it starts to
divide it's then inserted into another
female womb where it continues to
develop classification caraus classified
organisms into King om phm class order
family genus and species a good
pneumonic for this is King Philip came
over for good soup the binomial a Latin
name for an organism is just the genus
and species combined as time went on it
turned out that another level above
kingdom was needed domain the three
domains are ARA that's primitive
bacteria normal or true bacteria and
ukaria that's everything else of course
with DNA and nucleus of the cells you
should know about UK carotic cells from
paper one ARA by the way are often found
in extreme Environ on the earth they can
therefore be called
extremophiles final big topic ecology is
a study of how lots of organisms
interact in an ecosystem organisms
generally compete for food water space
and other things like CO2 and light for
plants shelter and mates for Animals
interdependence is the term given to the
fact that organisms can rely on each
other for these things and they can form
a community abiotic factors in an
ecosystem are the non-living aspects for
example light temperature moisture soil
pH CO2 and O2 levels in the air biotic
factors are due to organisms and things
like food that's available Predators
prey around other organisms pathogens
breeding behavior and more we can use
quadrats to estimate the size of a
population of an organism in a certain
area by sampling around say 10% of the
area taking a mean and then multiplying
up for the whole area using a quadrat
with a transect allows us to observe how
population distribution changes over a
distance the food chain shows the
direction that biomass and therefore
energy Flows In an ecosystem from one
organism to another producers are any
organism that uses sunlight to produce
biomass that's usually plants or algae
primary consumers eat the producers
herbivores that eat only plants or
omnivores that eat both meat and plants
then Predators known as secondary
consumers that could be Carnival or
omnivores they prey on them and then we
can have tery consumers as well apex
predators are those at the top of the
food chain they have no natural predator
above them these levels are called
trophic levels by the way the population
numbers of all of these will fluctuate
in an ecosystem over time by the way
this food chain is possible I looked it
up bears do eat foxes all life is carbon
based which means that when an organisms
die the carbon is recycled which
ultimately can be used to make more
organisms one way of course is when CO2
is produced which plants then used to
grow bacteria also release CO2 when an
organism undergoes decomposition water
follows a cycle rain falls then runs
into rivers into the sea then it's
evaporated and the cycle continues for
triple you need to know that farmers
utilize decomposition to produce natural
fertilizers that can then be used on
crops it can also be used to produce
methane gas to be used as fuel back to
double biodiversity is one of those Buzz
words that's very much in Vogue at the
minute basically it means how many
different types of organisms you have in
an ecosystem High biodiversity generally
makes for a stable ecosystem as
organisms don't have to depend on on one
species for a resource for example sadly
human development usually results in
lower biodiversity this development also
poses problems when it comes to waste
we're having to find more ways of
disposing of sewage fertilizers toxic
chemicals atmospheric pollution and more
to reduce our impact on the environment
one factor is the land that we need for
building quarrying farming and disposing
of waste an example of this is the
destruction of Peete bogs to make
compost which affects the habitat of
many organisms and microorganisms
burning pce also releases CO2 now going
off piece for a second for your exams
you need to say that carbon dioxide and
methane contribute to global warming
personally I'm not so sure especially
seeing that carbon dioxide only accounts
for 0.04% of the atmosphere while
methane is
0.18% you decide who's telling porkys
incidentally water vapor is responsible
for 95% of the greenhouse effect but you
never hear about that do you anyway
deforestation bad on a big scale
flattening forests reduces biodiversity
and it's often done to create Farmland
the Pyramid of biomass is a food chain
that shows us how much mass enters the
next trophic level relatively you need
to be able to draw one on graph paper
using numbers supplied in the question
and also calculate the percentage
absorbed by the next level as per usual
percentage is equal to the bit divided
by the lot time 100 of course this shows
that biomass is lost at each level
because it's not just a rectangle as not
all biomass is absorbed or consumed into
the next organ organism some is lost due
to the organisms living for some time
before being eaten by a predator for
example it's also lost as water Ura and
CO2 food security is a big thing
especially in these uncertain days food
is becoming more scarce due to
increasing world population changing
diets food being transported around the
world which requires huge amounts of
energy changing growing environments the
cost of farming that's a big one of the
minute and conflicts for example around
40% of the world's wheat comes from
Ukraine or at least it used to farmers
are constantly trying to find more
efficient ways of farming largely by
maximizing biomass input to crops and
animals while also reducing biomass lost
by them fishing sustainably is also
important if a species is fished at a
greater rate than its breeding then its
population can disappear in those areas
one way of sustainably fishing is by
having Nets with holes in that catch
adult fish but are big enough to let the
little ons out if young fish aren't
caught then they go on to breed so there
we go you find it helpful leave a like
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papers once you've done the exam come
back here and tell us all how you did
we'd love to know good luck
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