Transcript iGCSE Additional Science Biology Part 2

iGCSE Double award
Biology Part 2
Key word challenge……
What happens when you have a
vaccination?
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Antigen
Immunity
Immunisation
Immune response
Vaccination
Pathogen
How many keywords
can you include in
your explanation?
What are antibiotics and how do they
work?
• Can you name any antibiotics?
• Do you know who discovered penicillin?
Antibiotics
• Antibiotics, including penicillin, are
medicines that help to cure BACTERIAL
diseases by killing the infective
BACTERIA inside the body.
Why don’t antibiotics work when you have a
virus e.g. a cold?
Antibiotics
There are 2 reasons why you can’t take
antibiotics for a viral infection e.g. a common
cold.
1. Most Antibiotics work by destroying the cell
wall of the pathogen- viruses don’t have a cell
wall.
2. Viruses live and reproduce inside your living
cells. It is very difficult to develop a drug that
kills viruses without damaging the body’s cells
What about painkillers?
What do they do?
Painkillers help to relieve the symptoms of
infectious disease but they DO NOT kill
the pathogens.
Have we always protected
ourselves against disease in the
same way as we do today
What happens when pathogens
mutate?
Pathogen
Infectious disease
Bacteria
Salmonella, cholera,
tuberculosis, tetanus,
MRSA
Virus
Flu, chicken pox, AIDS,
Hepatitis B, Measles
Fungus
Thrush, athletes foot
Protozoa
Malaria, dysentery
Finnish your medicine!!!
• What happens inside your
body when you take antibiotics?
• What happens if you don’t finish the course?
What is a mutation?
How and why do mutations happen?
Mutation
• The word mutation means a change in the
genetic composition of a cell. Mutations can
be divided into two main groups.
• The first group is gene mutations.
• The second is chromosome mutations.
What causes mutation?
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Spontaneous
Increases caused by environmental factors
UV light
X-rays
Mutagens – chemicals such as benzene,
formaldehyde, carbon tetrachloride
Antibiotic resistant bacteria
• Many strains of bacteria – INCLUDING
MRSA – have developed RESISTANCE to
antibiotics as a result of a mutation, leading
to natural selection.
• Why is this a problem?
• What must we do to prevent more strains
of bacteria becoming resistant?
– Not overuse antibiotics
– Don’t use to treat mild infections like sore
throat
– Ensure that people complete their whole course
of antibiotics.
MRSA
Methicillin Resistant Staphylococcus Aureus
Staphylococcus aureus is a bacterium often found in 20-30% of
the noses of normal healthy people and is also commonly found on
people's skin.
Staphylococcus aureus which are resistant to an antibiotic called
methicillin are referred to as methicillin-resistant Staphylococcus
aureus or MRSA. Many commonly prescribed antibiotics are not
effective against these bacteria
www.mrsa.uk.com
MRSA
MRSA may occasionally get into the body (eg
through breaks in the skin such as abrasions,
cuts, wounds, surgical incisions or indwelling
catheters) and cause infections.
These infections may be mild (eg pimples or
boils) or serious (eg infection of the
bloodstream, bones or joints).
Why is MRSA causing such a
problem in our hospitals?
How can we help reduce these
problems?
Pandemics, Epidemics
Pandemic: A disease prevalent throughout an
extensive region, country, or continent, or
throughout the world. E.g. SARS, Swine flu
http://www.cdc.gov/vhf/ebola/outbreaks/2014-westafrica/
Epidemic: The occurrence of disease within a
specific geographical area or population that is in
excess of what is normally expected. E.g. Foot and
Mouth, Plague
Why did Swine flu cause such a
scare across the world, even to
those people who have had the
flu vaccine?
Why is it so hard to stop the spread of a new,
mutated disease?
Whiteboards at the ready…….
How can we find out more about
pathogens which cause diseases?
Step by step method
• Hints
– How do you keep everything sterile?
– Why do you need to let the inoculating loop cool?
– Why should you not take the lid completely off the
agar plate?
– Why do you secure the lid with 3 pieces of
selotape?
– Why can you not incubate above 25oC in school
laboratories?
– Why do they incubate at a higher temperature in
industry?
Photosynthesis……? ☼
What do you already know?
Learning Objectives:
• To give the equation for photosynthesis
• To explain why plants are green
• To describe where the energy comes from
and how it is used
Plant cell
• To explain why plants are green
Why am I
green?
Think
Find out
Discuss
Photosynthesis
• Photosynthesis is summarised by the following
equation:
………………. + ……………..
…………....+ …….………..
Formula equation (2 minute challenge for 10 VIVOs)
Where do plants get their energy from
and how do they use it?
What factors limit the rate at which
photosynthesis takes place?
• The rate of photosynthesis may be limited by:
– Low temperature
– Shortage of carbon dioxide
– Shortage of light
• Annotate these
graphs to
describe what
is happening
• Working with your given
partner, you need to give
a clear EXPLAINATION of
each graph
Is the rate of photosynthesis in a normal
plant effected by just one of the factors?
• No
• Light, temperature and availability if carbon
dioxide interact and, in practice, any of them
may be the factor that limits photosynthesis.
If you were a crop farmer using a greenhouse,
what would you do to increase your yield?
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Artificial light
Artificial heat
Additional Carbon Dioxide
….Why would paraffin lamps be good to use?
• What are the pros and cons of your approach?
Used for respiration
Converted into fats,
oil or protein in
storage organs e.g.
nuts & seeds
Converted
into starch
& stored
in fruits
and roots
Converted into
cellulose & used in
cell walls
Become
nitrates which
are used to
make
proteins
Where do I store my starch?
• STARCH????? What is it? What is it made from
……
• How could we test for starch?
• Predict – where do you think you would find
the most starch in a plant?
If you were a crop farmer using a greenhouse,
what would you do to increase your yield?
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Artificial light
Artificial heat
Additional Carbon Dioxide
….Why would paraffin lamps be good to use?
• What are the pros and cons of your approach?
How are plants specially adapted to be good
at obtaining the substrates they need?
Guard Cells make a pore called a
stomata.
Carbon dioxide enters the leaf
through the stomata by
diffusion.
Inside the leaf= lower
concentration of carbon dioxide
Outside the leaf= higher
concentration of carbon dioxide
Can you label the cross section of
this leaf? What do the
different transport
tissues carry?
Ext - Which parts of the
leaf are important to
consider for transpiration?
Why is it important that plants have
guard cells?
Where would you find the most
stomata? WHY?
What happens to the water once it has
been absorbed via the roots?
• What has happened to your celery?
Plant hormones
• What are they?
• What effect do they have on plants?
Plant hormones
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What are plant growth hormones called?
What are plant growth hormones used for in
agriculture?
What are the pros and cons of using plant
hormones as a weed killer?
What are the pros and cons of using plant
hormones to help roots develop artificially?
Why are we like we are?
5 key words you must
include…..
• Gametes
• Fertilisation
• Chromosome
• Environment
• Genes
Chromosomes, genes and DNA
• Chromosome – rod shaped body found in the nucleus of cell
which contains genetic information (DNA). Humans have 46
chromosomes. All animals and plants have a different number
of chromosomes.
• Gene - A gene is a section of DNA that carries the code for a
particular protein. Different genes control the development
of different characteristics of an organism. Many genes are
needed to carry all the genetic information for a whole
organism. Chromosomes, which are found in the nucleus of
the cell, contain many genes.
• DNA – Deoxyribonucleic Acid.
What so these cells have to do with
inheritance?
Human Karyotype
• Look at the human karyotype.
• How many individual chromosomes are there?
• How many pairs of chromosomes are there?
– Note that one chromosome from each of the pairs
comes from the mother and one from the father.
What are the causes for the
differences between us?
• Genetics (i.e. our DNA coding)
• Environmental
• You need 3 examples of each of these causes.
What causes these hairstyles?
http://www.telegraph.co.uk/news/health/318
3666/Genetic-link-to-baldness-discovered.html
Could you apply this to plants?
Variation
Variation can come about for two reasons:
1. Some features can be inherited. That means that you get
them from your parents and they are controlled by genes
2. Other features are affected by the environment.
3. Lots of features are a combination of both
Examples?
–To recall and explain the 2 factors which
influence who and what we are
Genetic or environment?
Inherited from parents
Big muscles
fashion sense
Eye colour
Caused by environmental
factors
Natural hair colour
Lung cancer
Sickle cell anaemia
23 chromosomes
Egg cell from
mother
containing
exact replica
of 50% of
mothers DNA
23 chromosomes
Sperm cell from
father containing
exact replica of 50%
of fathers DNA
23 chromosomes
1 from each homologous pair
23 chromosomes
NOTE - the parental
chromosomes carry
the genes which
determine the
characteristics of the
child.
1 from each homologous pair
46 chromosomes
23 chrom. from mother + 23 from
father giving 46 chromosomes
which carry the DNA for the new
person.
Reproduction!!!??!!
• Sexual reproduction vs. Asexual reproduction
Sexual Reproduction – Where a male and female gamete
fuse together.
The genetic information from the two parents are mixed
together leading to variety in the offspring.
Asexual Reproduction – Only one individual is needed as the
parent.
There is no fusion of gametes and therefore there is no
mixing of genetic information. As there is no mixing of
genetic information all the offspring are exactly the same,
these genetically identical individuals are known as CLONES
• What type of reproduction
does this picture show?
• What can we call the
offspring?
• What could we conclude
about the offspring?
What are the benefits of sexual and
asexual reproduction?
Sexual
Asexual
From Mendel to DNA
Starter
• What can you tell me about Mendel?
Keywords for the topic!
1.
2.
3.
4.
5.
6.
7.
8.
9.
Chromosome
Gene
Allele
Dominant
Recessive
Genotype
Phenotype
Homozygous
Heterozygous
Find an expert!
You have 2 mins to
familiarise yourself with
these words before we
begin!
Terms to know
A GENE is a section of DNA which codes for a specific
protein and therefore characteristic. There are different
versions of one gene and these are called ALLELES
When there is more than 1 version of a gene the cell will
have a preferred choice which is called the DOMINANT
gene (allele) and the unused allele is called the RECESSIVE
GENE.
•For the recessive gene to be expressed, the individual
must be homozygous for that gene (both alleles the same).
•If a person has two different alleles then they are
heterozygous for that gene.
•What you see (is expressed) is the PHENOTYPE e.g. Tall
•What the genes are is the GENOTYPE e.g. TT or Tt
Why does sexual reproduction give
rise to variation?
The Work of Gregor Mendel
 What does this show?
x
F1
F2
Crossed together a tall pea
plant and a dwarf pea plant
The resulting
offspring are
all tall
F2 generation
were present in
the ratio 3:1
tall to short
From this experiment Mendel made three important
conclusions:
1. That the inheritance of a trait is determined by units (now
called genes) that are passed to descendents.
2. An individual inherits one unit from each parent for each
trait.
3. That a trait may not show up in an individual but can still
be passed on to the next generation.
GENE- is a small section of DNA, an inheritable unit of
information coding for a particular trait e.g. height
This experiment also show us the tall gene is dominant (will
be expressed) over dwarf gene. Different forms of the
same gene are called alleles.
Inheritance in action!
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Write a sentence on your whiteboard which
contains AT LEAST one of the words below.
** 10 VIVOS if you can include them all!**
Chromosome
DNA
Gene
Allele
Dominant
Recessive
COPY
A Chromosome
 Each gene
codes for a
particular
Gene with different
alleles (Heterozygous) combination of
amino acids
which makes a
Attachment point (not a specific
gene): Centromere
protein.
 Therefore
genes are
responsible
Gene with identical
for your
alleles (Homozygous)
different
features
Dominant and
recessive
• An allele that controls the development of a
characteristic when it is present on only 1 of
the chromosomes is a DOMINANT ALLELE
• An allele that controls the development of
characteristics only if the dominant allele is
not present is a RECESSIVE ALLELE.
Do a genetic cross diagram for the following
situation.
 Black is the dominant allele
Parent One: Black mouse, Genes: BB
Parent Two: Brown mouse, genes bb
What are the ratios of the offspring coat
colour?
Do a genetic cross diagram for the following
situation.
Parent One: Black mouse, Genes: Bb
Parent Two: Brown mouse, genes bb
What are the ratios of the offspring coat
colour?
 Dimples are controlled by a dominant gene
The father has dimples but the
mother does not. The father is
heterozygous for dimples.
What is chance of their first child
having dimples?
What is the chance that their
second child will have dimples?
 Another couple, who both have dimples, have a
baby, which does not have dimples. What are
the genotype of the parents?
Why does sexual reproduction give
rise to variation?
How is the sex of a baby determined?
Human Chromosomes
Humans have 46
chromosomes (23 pairs) one
set of 23 inherited from
their mother another set of
23 from their father.
22 pairs are autosomal
chromosomes this mean
they contain genes to all
the body.
The 23rd pair are the sex
chromosomes for
determination of sex.
In females, the sex chromosomes are the same (XX),
in males the sex chromosomes are different (XY). Is
this person male or female?
Sex Determination
Parents Phenotype: Male x Female
Genotype:
XY
x
XX
 What are the chances of having a boy?
Father
gametes
X
Y
XX= female
XY= Male
Mother
X
XX
XY
X
XX
XY
50% Chance of having
either a boy or girl
The sex of a
baby is
determined
by the father
DNA Fingerprinting…?
Genetic Crosses
Mother is homozygous for blue eyes, Father is heterozygous
for green eyes, other allele is for blue eyes. Green is
dominant over blue. Calculate the ratios of their children’s
eye colour
Parents Phenotype:
Let
= green
= blue
Parents Genotype:
gametes
Mother
Father
Polydactyly disease
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Cause –
Which system in the body does it effect? Symptoms Outcome -
Having extra fingers and/ or toes, caused by an
dominant allele of a gene. It can therefore ONLY be
passed on by a parent who has the disorder
 If 1 parent is heterozygous for the disease, what is the
percentage chance the children will have it?
Cystic Fibrosis
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Cause –
Which part of the body does it effect? Symptoms Outcome -
 Disorder of cell membranes. Must be inherited from
both parents and is caused by a recessive allele of a
gene. It can therefore be passed on from parents,
neither of whom have the disease. Parents can be
CARRIERS of the disease.
Sickle-cell anaemia
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Cause –
Which part of the body does it effect? Symptoms Outcome -
 An inherited condition affecting red blood cells. Must
be inherited from both parents and is caused by a
recessive allele of a gene. It can therefore be passed
on from parents who are CARRIERS of the disease.
 Heterozygous people will have some protection
against malaria.
Down’s syndrome
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Cause –
Which part of the body does it effect? Symptoms Outcome -
 Extra copy of chromosome 21 so that the baby has
47 chromosomes.
 Can cause developmental problems in many different
areas including the brain, heart and muscles
If both parents are heterozygous for the Cystic
Fibrosis gene, what is the percentage chance of their
children having the disease?
Exam questions (3 marks)
• Mr and Mrs Smith both have a history of cystic
fibrosis in their families.
Neither of them has cystic fibrosis.
Mr and Mrs Smith are concerned that they
may have a child with cystic fibrosis.
• Use a genetic diagram to show how they could
have a child with cystic fibrosis.
• Use the symbol A for the dominant allele and
the symbol a for the recessive allele.
Inheritance of Colour (red-green) Blindness- Sex Linked
Sex linked
genes only
present on X
chromosome
Y
X
XX= Female
8% men affected
but only 0.5% women
Gene for colour
blindness is carried on
the X-chromosome, it is
a recessive gene.
XY= Male
X1 = X-chromosome with the
affected allele for colour blindness
 So… why is it more common for boys to be
colour blind?
Inheritance of Colour (red-green) Blindness- Sex Linked
X 1Y
Colour blind
XY
Normal Vision
XX
Normal Vision
X 1X
Carrier
Father
M
o
t
h
e
r
X1
Y
X
X1
XY
X
X1
XY
Daughters are
carriers, sons are
unaffected
Now carry out a cross if this daughter were to have
children with a normal man.
Cloning!!!
• 5 minute find out….
Success Criteria:
• To give a step by step method for each different cloning
technique
• To explain why it may be advantageous to clone certain
certain individual plants or animals.
• To evaluate the economic, social and ethical concerns
surrounding cloning
Tissue Culture
Method
Embryo Transplants Adult Cell
Method
Why and when
would you use it?
Why and when
would you use it?
Evaluation
Evaluation
Method
Why and when
would you use it?
Evaluation
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Adult cell cloning
https://www.youtube.com/watch?v=Vvz0tfFe9CI
Tissue culture
https://www.youtube.com/watch?v=6y13hYGPi8
Q
• Embryo transplants
• https://www.youtube.com/watch?v=bJ_zFG_NWi
M
Success Criteria:
• To give a step by step method for each different cloning technique
• To explain why it may be advantageous to clone certain certain
individual plants or animals.
• To evaluate the economic, social and ethical concerns surrounding
cloning
Cloning
• The good……………………. The bad…………………….
• The conclusion!
Learning Intention – to learn about the different types of genetic manipulation
Genetic Engineering
• What is it?
• How do we do it?
Success criteria:
• To give a step by step method for how to genetically
engineer something
• To explain the different ways in which GM can be
used
• To evaluate the use of GM
Process of
genetic
engineering
Genetic Modification
• Give 5 ways in which GM is / has been used
• When, in the development of an organism, does
GM have to happen?
• http://www.bionetonline.org/english/content/ff_
cont3.htm
• http://listverse.com/2013/07/26/top-10-gmanimals-you-can-buy-or-eat/
Evaluate the use of genetic
engineering
Spec link
DNA to protein
• Gene is copied
• Copy leaves the
nucleus
• Ribosome readys
copy of DNA.
• Bases are read in 3s
• 3 bases = amino
acid
• A string of amino
acids is produced =
protein
You are a dormouse!
• What are the 4
essential things
that you need to
survive and
reproduce
3 minute find out
How would these things change if you were a plant?
How are animals adapted to ensure
that they can get these things?
Adaptation
Define - 5 minute find out
Success Criteria:
• To be able to define the term Adaptation.
• To be able to give an example of an animal and explain how it is
adapted to suit its environment.
• Explain why certain animals have certain adaptations and features
using ideas such as volume to surface area ratio.
Animal adaptation
• Animals have physical adaptations
which enable them to survive in the
conditions in which they normally
live.
• Write down 3 examples of physical
adaptation.
• Animals may also have special
features e.g. spines, which help
them to deal with specific aspects
of their environment.
• Can you think what these aspects
may be and give 3 examples of
specialised features of named
animals.
Why are polar bears and walruses so big?
In the arctic is it
better to be large or
small???
Is it only size which matters?
• What other factors
are important when
surviving in freezing
conditions?
Oh dear….. elephants are huge – why don’t they
die in the sweltering heat?
Plant adaptations
Success Criteria
* To give an example of a plant and explain
how it is adapted to survive in its
environment.
* To give 3 ways in which desert plants are
adapted to survive in extreme conditions
* To explain what an extremeophile is and give
an example
Plant adaptations
• Plants may be adapted for survival in the
conditions they normally live e.g. desert and
arctic
• Plants may be adapted to cope with specific
features of their environments e.g. thorns,
poisons and warning colours.
What is the biggest threat faced by plants
in the desert?
What adaptations do desert plants have to
survive such hot weather?
* Draw a typical desert plant and annotate it to show how it is
adapted to survive!
* To give 3 ways in which desert plants are adapted to survive
in extreme conditions
What adaptations do desert plants have to
survive such hot weather?
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Few/no leaves
Deep roots
Thick, waxy cuticle
Spines
Deep and few stomata
Specialised Plant Cells: Guard Cells
•Kidney bean shaped cells.
•Mostly found in the lower
epidermis.
•Can open and close.
•Allow gases e.g. carbon dioxide
in and oxygen and water vapour
out.
•Flaccid= Closed
•Turgid (Swollen)= Open
Guard Cells make a pore called a
stomata.
Carbon dioxide enters the
leaf through the stomata by
diffusion.
Inside the leaf= lower
concentration of carbon dioxide
Outside the leaf= higher
concentration of carbon dioxide
Competition in Animals
• Success Criteria:
To be able to answer the following questions:
– What do animals compete for?
– How do different animals compete and display?
Review and build
• Thinking of both plants and animals…
• Around the room are 3 boards, please go to
each in turn and write examples of organisms
which have specific:
– Structural adaptations
– Behavioural adaptations
– Functional adaptations
• Please explain what the adaptation is and why
they have it.
What do animals compete for?
Being fit!
• For animals the distinction of
being ‘fit’ is how many
offspring they have.
• I.e. how many set of their
genes they pass onto the
next generation.
• Finding the ‘fittest’ mate is
therefore extremely
important.
• Thus animals compete in
various ways to mate with
the fittest. E.g. display or
fight.
Something to think about….
• What is the difference between intra-specific
competition and inter- specific competition?
• What makes a successful competitor?
• What is it most important to compete for food, territory or mate? WHY?
Competition in plants
• Success Criteria:
– To review why plants
compete with each
other.
– To state what plants
compete for
– To apply your
knowledge to explain
how plants compete.
How do all of these plants survive?
Competition in plants
• What do plants
compete for?
• How do they
compete?
Seed dispersal
• How do plants disperse their seeds?
•
https://www.youtube.com/watch?v=buZV0h4vfmQ
• Why is it important for plants to be good at
seed dispersal?
Distribution of organisms
Success Criteria:
• List the physical factors which affect the distribution of
living organisms
• Explain the different ways in which you could sample an
area
• Apply your knowledge of sampling techniques to
correctly select the appropriate method to use in
different situations
What readings could we take to give us
information about this environment?
What readings could we take to give us
information about this environment?
Biotic
Abiotic
What would happen if we greatly reduced or
increased one of these factors?
Suggest an explanation for why
How
could
you
gather
quantitative
data
How
couldare
you
sampleat
this
the trees
growing
thearea
about
the
distribution
of
organisms?
to
collect
some
back
of this
areadata?
and not in the
middle?
Collecting data on the distribution of
organisms
• Random sampling
• Sampling along a transect
*When would you use this method of sampling?
*How EXACTLY do you carry out this method?
*What sort of data would you collect?
What do these words mean???
Valid
Dependant variable
Accurate
Can you come up with:
1) A valid method for gathering information
about how the distribution of daisies alters
as you move away from a tree.
2) A non-valid method for gathering
information about how the distribution of
daisies alters as you move away from a tree.
Think…..
• Give at least 4 different possibilities:
– Why does the population of rabbits in
Sandringham woods vary from 800 in year 1 of
sampling to 1000 in year 2 to 300 in year 3?
How can environmental change be
measured?
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•
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•
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Rainfall
Oxygen levels
Temperature
pH levels
Living factors…….
– Living organisms can be indicators of pollution –
give 3 examples of this
– 5 minute find out
5 minute find out….
• What is the ‘biotic index of water cleanliness’?
The impact of change
Environmental changes have an affect on the
distribution of organisms.
• You have 15 minutes to research and report back to the rest of
the class on this question with reference to:
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–
–
–
–
–
–
–
Bluebells
European birds
Dartford warbler
Honey Bees
Polar bears
Killer Whales
Snowshoe Hares
Coral
Exam Question
• How repeatable, reproducible and valid do
you think the data on change in an
environment provided by living indicators
might be?
Evolution
Survival of
the fittest
What can you
already tell me
about these
words?
Natural Selection
Darwin
Theories of evolution
• Lemark and Darwin both constructed theories of evolution.
• What did they believe happened?
• 5 minute find out!
• https://www.youtube.com/watch?v=gIoqci8xcNU
• http://www.cornell.edu/video/darwinian-revolutions-3lamarcks-theory
Lamarck
Darwin
• How did they come up with their theories?
• What were their theories of evolution?
Lemarck vs. Darwin
Explain that theory!
Darwins theory of evolution
• https://www.youtube.com/watch?v=iKz01UB8QrY
• https://www.youtube.com/watch?v=vnktXHBvE8s
• The theory of evolution states that all species of
living things which exist today have evolved from
simple life forms which first developed more than
three billion years ago.
Why was Darwin’s theory not accepted
by all at the time of publishing?
Natural Selection
• What are you examples??
• Working as a group, put together a flow
diagram to explain how natural selection
works
• Can you create a model to demonstrate this to
another group?
• http://peppermoths.weebly.com/
Natural Selection
• Favourable genes are passed
on to the next generation
• Variation in a population
• Mutation of a gene
• Most ‘well adapted’/
fittest breed
• Certain genes give
advantages to survival
* Some individuals have genes which
mean that they are better suited to their
environment
Why is mutation important in natural
selection?
•
•
•
•
What is a mutation?
Increases variation
Could be good or bad
If helps organisms to be better adapted to its
environment then the frequency of it will
increase
Timescales of evolution
• Does evolution take place over the same
length of time for every species?
– Discuss and explain your answer (4 marks)
– The timescale for evolution depends upon the life
cycle and complexity of an organism
• Simple life forms eg bacteria can evolve much faster
than more complex organisms such as mammals
Classification and evolution
• What is classification?
• What do we look for when we are classifying
organisms?
• What is the ‘natural classification system’?
• What are evolutionary trees and how to they
help us to work out evolutionary and
ecological relationships? (4 marks)
Formation of fossils
• Why are we not certain about the origins of
life on Earth?
• What is a fossil?
• What are the 4 ways in fossils can be formed?
• Why are fossils useful to us?
• Why is the fossil record incomplete?
Y11 – Period 1
Extinction!
• 5 minute find out….
Causes of extinction!
Living organisms causing Environmental changes
Extinction
Extinction
*New Predators
* New Diseases
* More successful
Competitors
* Changing climate and
environment over
geological time
* Catastrophic event
Please give an example for each one!
How are we doing with this?
• Please answer these questions in the back of
your book
– Give 4 causes of extinction in species of living
organisms
– Give 2 possible causes of mass extinction events
– Why is extinction and important part of evolution?
What are the ways in which
populations can become isolated?
Specification link
New species arise as a result of:
isolation: two populations of a species become
separated, eg geographically
genetic variation: each population has a wide range
of alleles that control their characteristics
natural selection: in each population, the alleles that
control the characteristics which help the
organism to survive are selected
speciation: the populations become so different that
successful interbreeding is no longer possible.
Can you make a mnemonic to help
you remember this?
Pyramids of Biomass!
• Success Criteria
– To define the key terms for this topic and use
them within your work
– To construct a pyramid of biomass
– To peer assess a pyramid of biomass with
reference to marking criteria
– To extend… you will use your knowledge to
consider WHY the biomass decreases at each
tropic level.
Key terms
• What are they for this topic?
–
–
–
–
–
–
Biomass
Consumer
Producer
Herbivore
Carnivore
Trophic level
• Lets define… 5 mins 
– To define the key terms for this topic and use them within your
work
If I told you that the
biomass of the oak
tree is 10kg, what
would the biomass of
the caterpillars be?
Why is the biomass at
each level of the
pyramid not the
same?
Where does the energy
come from initially?
–To extend… you will use your knowledge to consider WHY the
biomass decreases at each tropic level.
Pyramids of Biomass
• The mass of living material (biomass) at each
stage in a food chain is less than it was at the
previous stage.
• Radiation from the Sun is the source of energy for
the most communities of living organisms. Green
plants capture a small part of the solar energy
which reaches them. This energy is stored in the
substances which make up the cells of the plants.
Pyramids of biomass
• We can draw a pyramid of biomass where the
length of each box shows the total mass of
organisms at each trophic level.
• Task:
• Can you draw a pyramid of biomass to show 100Kg
of grass, eaten by 40kg of grasshoppers, eaten by a
15kg snake which dies and is decayed by 1.5kg of
bacteria.
• Extension – Explain why each box is smaller!
– To construct a pyramid of biomass
– To extend… you will use your knowledge to consider WHY
the biomass decreases at each tropic level.
Rules of drawing a pyramid of Biomass!
•
•
Lets mark out of 5:
A pyramid of biomass must
1.
2.
3.
4.
Be drawn with a pencil and ruler
Be drawn to scale (with the scale indicated)
Each box must be the same height
Each box must be a different length and correctly drawn
according to the scale given
5. Each box must be labelled with organism and mass
• WWW and EBI
• Student response and improvement
* To peer assess a pyramid of biomass with reference to
marking criteria
Review:
• What is a pyramid of biomass and what does
it show?
• Where does the energy come from initially
and why do we not end up with the same
amount of energy?
Pyramid of biomass
• Please draw a pyramid of biomass for the
following data:
• 1000kg of Oak tree is eaten by
• 200kg of aphid, which is eaten by
• 30kg of Great tits, which is eaten by
• 3kg of Sparrow hawk
Why is the biomass of
organisms less at each
successive level?
If the sun gives 1000Joules
of light, why does the plant
only have 400 Joules?
Success Criteria:
• To state and explain 3 ways in which energy is lost from an organism.
• To apply your ideas to help you explain why different organisms lose
different amounts of energy
• To explain where all the nutrients go at successive levels in the food
chain
How much of the energy was lost at
each stage?
• How was the energy lost?
•To state and explain 3 ways in which energy is lost from an
organism.
Sun
Corn
Cattle
Burger
Energy Losses
• The amount of material and energy contained in
the biomass of organisms is reduced at each
successive stage in a food chain because:
– Some materials and energy are excreted as waste
materials
– Respiration releases a lot of energy which is eventually
lost as heat
– Endotherms loose a lot of energy as they have to
maintain their constant body temperature, which is
often higher than their surroundings.
Where did last years leaves go?
Learning Objectives:
• To review our experiment/ look at progress to explore what
factors cause decay
• To explain what happens to the products of decay
• To give at least 3 stages in the carbon cycle
Decaying food
• Why does food decay?
• What causes it?
• What conditions are best
for decay to occur?
• What has happened to
your bread?
•To review our experiment/
look at progress to explore what
factors cause decay
Decaying Food
• Materials decay because they
are digested (broken down) by
microorganisms.
• Microbes digest food faster
when it is:
– Moist
– Warm
– ..and usually when there is
plenty of oxygen (why?.......)
In nature, what happens to the
products of decay?
• They are released into the soil and used by plants to
grow.
•To explain what happens to the products of decay
What does this antelope give to and take from the
environment during its life time?
Recycling in nature?........ How does it
work?
• Living things remove materials from the
environment for growth and other processes.
These materials are returned to the environment
either in waste materials or when living things die
and decay.
• In nature, the processes which remove materials,
are balanced by processes which return materials
– the materials are constantly recycled
• CAN YOU THINK OF ANY EXAMPLES?
• 5 minute find out……
Where could I find carbon
containing compounds?
Success Criteria
• To state at least 5 Carbon containing compounds
• To explain how carbon is transferred from one
organism to another nature
• To construct a cycle to show this transfer between
living and non-living parts of the world
THE CARBON CYCLE
 What is it, what happens?
5 mins – find out as much as you can
•To explain how carbon is transferred from one organism to another
The carbon cycle
• .. Is the constant cycling of carbon!
Use the pictures to help you construct you own cycle
* Use arrows to show the direction of the
carbon flow
* Label the arrows to name the processes
* Explain exactly what is happening to the
carbon in each transfer (what is it being turned into?)
•To explain how carbon is transferred from one organism to another