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ADAPT OR DIE
Topic 5.7
CHANGING HABITATS

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A species lives there because it is specially
adapted to survive and reproduce there- in the
conditions in that habitat determined by the
biotic and abiotic factors. It has a
competitive/selective advantage
Increased temperature (abiotic factor) may
decrease size of habitat, organisms in the Arctic
and surrounding sea may
Emigrate
 Face local or worldwide extinction
 Adapt over many generations

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Climate change is a selection pressure for natural
selection
EVOLUTION AND NATURAL
SELECTION
 Evolution:
The change in an anatomical,
physiological or behavioural feature
over generations. Also the change in
allele frequency in a population over
time.
 Natural selection:
 The mechanism by which organisms
change over time as they adapt to their
changing environment.

POPULATION GROWTH CURVES.
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Limiting factors are any factor that would limit the population
growth. e.g. competition for/limited supply of food or space,
predation, disease, light intensity- biotic and abiotic factors
The carrying capacity is the maximum population size the
habitat can support.
ACTIVITY 5.22B POPULATION GROWTHTEACHER’S SHEET
Slow increase due to
individuals widely
dispersed- low birth
rate
 Exponential increase
as there are very few
limiting factors- high
birth rate, low death
rate.

• Slower increase in population- There are more
limiting factors increasing the death rate and
decreasing the birth rate.
• Population size remains more or less constant with
fluctuations- birth rate and death rate are equal.
ACTIVITY 5.22B POPULATION GROWTHTEACHER’S SHEET

What might cause an INCREASE in the carrying capacity in a
natural population of a herbivorous mammal?
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A predator becomes extinct
Increase in average annual temperatures- faster
rate of growth- increased food supply- less
competition for food
Increase in annual rainfall-increased growth rate of
plants- increased food supply- less competition for
food
ACTIVITY 5.22B POPULATION GROWTHTEACHER’S SHEET

What might cause a DECREASE in the same population?
 Spread of a new disease across the population
 Decreased food supply- less competition (see above)
 Reduction in the size of the habitat due to climate
change- greater competition for space- faster spread of
disease
ACTIVITY 5.22C THEORY OF NATURAL
SELECTION- BY CHARLES DARWIN

Over-production of offspring- more
offpring were produced than necessary to
replace the adult population.
 There is variation within a speciesHow does it arise?
Crossing over during prophase 1 of
meiosis
Independent assortment during
metaphase/anaphase 1 of meiosis
Random fertilisation
Mutations- source of new alleles
• Struggle for existence: not all offspring will
survive. Predation, competition, disease,
extreme environmental conditions…etc limit the
population growth. Factors limiting population
growth result in selection pressure.
• A change in the environment result in a change in
the selection pressure.
• Survival of the fittest- some characteristics
which were selectively neutral are now selected
for (have a selective /competitive advantage)
due to the change in the selection pressure.
Organisms with these characteristics are more
likely to survive and more likely to reproduce
passing on the advantageous allele to the next
generation. Fitness- ability to survive and
reproduce
• Some characteristics are now selected
against (have a selective disadvantage)
due to the change in the selection
pressure. Organisms with these
characteristics are less likely to survive
and less likely to reproduce
• From one generation to the next the
frequency of the advantageous allele
will increase.
NATURAL SELECTION IN A NUTSHELL
Suggest the source of the
variation in colour.
 What is the selection
pressure?
 Which organisms are
selected for? What is the
advantageous allele?
 Predict what the population
will look like after a few
generations. Why?

DARWIN’S OBSERVATIONS- 1
Organisms produce more offspring than survive and
reproduce
 Numbers in natural population stay approx. the same
over time
 Can you explain these two observations in terms of
limiting factors?

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As the populations increase limiting factors increase
(predation, competition for food and territory, rapid
spread of disease due to overcrowding).
What term is given in natural selection to the
limiting factors ( or environmental factors) which
limit population growth
Selection pressures. Remember- climate change can be
a selection pressure.
DARWIN’S OBSERVATIONS- 2
There is a huge amount of variation within a
species
 What are Darwin’s Conclusions ?


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Survival of the fittest- some characteristics are
selected for (have a selective advantage) due to
the selection pressure (environmental factor
which causes this selection) Organisms with these
characteristics are more likely to survive and
reproduce passing on the advantageous allele
to the next generation. Fitness- ability to survive
and reproduce. Therefore the advantageous
allele frequency will increase with every
generation .
Checkpoint 5.6
Q5.6 Write a summary explaining how natural selection can lead to
evolution.
A population has some naturally occurring genetic variation
with new alleles created through mutations. Organisms
produce more offspring than can survive and reproduce. There
is competition for survival between members of a species.
Organisms that are best adapted to conditions in their
environment are more likely to survive and reproduce. Natural
selection occurs; organisms with adaptive features that give a
selective advantage survive and produce offspring. The
offspring are more likely to have any alleles that contribute to
the adaptive features, so these alleles become more common
in the population. Those organisms that are not well adapted
are more likely to die before maturity and so do not produce
many offspring. Over a period of time, the composition of the
species will change to the more adapted form.
WHAT EVIDENCE DID DARWIN HAVE?
Biogeography
 Comparative embryology
 Paleontology
 Comparative anatomy

EVIDENCE FOR EVOLUTION
Darwin’s evidence.
 Observations of similarities and differences
between organisms and their geographical
location and fossil record
 BUT Darwin did not understand how the
variation could be inherited.


Mendel’s pea plant experiments were the first to
show characteristics could be inherited in a
predictable manner.
PEER REVIEW PAGE 57
Q 5.42- Define the word gene. Include following terms in
definition- nucleotides, polypeptide, allele,
phenotype, genotype, dominant, recessive,
expressed, polygenic, mutations
 Q 5.43-5.45
 5.43- Authors can’t influence reviewers- e.g. bribery
 5.44- Advantages-faster exchange of ideas.
Disadvantage- poorly conducted studies can be
publisized online, misleading people
 5.45- Audience can question scientist presenting(immediate peer review)
- Scientist receive immediate feedback and open
discussions
- Funding bodies can assess outcomes of project

ACTIVITY 5.22, DEBUNKING THE MYTH OF
POLAR BEAR HAIR
What makes something black……or white?
 Reflection or absorption of the different wavelengths
of light
 What is UV light?
 Shorter wavelength, higher energy than visible light
and infrared.
 Discuss cards in small groups
 Read the article over the page and then answer
Questions 1-3.

MOLECULAR EVIDENCE

What further evidence of evolution came AFTER
Darwin’s time?
 Genomics: the study of DNA (the number and
order of bases)
 Proteomics: the study of proteins (the number
and order of amino acids)
Techniques used to study and analyse DNA.

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DNA hybridisation,
DNA profiling,
DNA and protein sequencing,
DNA molecular clocks.
MOLECULAR EVIDENCE
What information could we find out by studying
DNA and proteins from different species?
 How closely related organisms are to one
another. If there are FEWER differences
between the DNA/Protein then the two
species have evolved from a common
ancestor MORE RECENTLY.


http://acinonyxscepticus.wordpress.com/2009/02/03/awesome-animation-speciation-and-the-tree-of-life
/
Activity 5.23a DNA Hybridisation

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http://highered.mcgraw-hill.com/sites/0072556781/student_view0/chapter14/animation_quiz_4.html
How do high temperatures cause DNA to
separate into single strands?


Increaed kinetic energy breaks the H- bonds
between the complementary base pairs
What is meant by the following terms in the
context of this animation?
 Anneal- Combine, in this case H-bonds to
reform between complementary base pairs

DNA hybridisation- DNA strands from different
sources anneal

Homologous DNA strands- Double stranded
DNA strands which have identical base
sequences or at least are very similar
Pure chimp DNA will separate at a higher temperature
than a hybrid of chimp and human DNA because the
two strands are completely complementary
• Heat up DNA from Humans, Chimps and gorillas so
that the DNA strands separate
• Cool and mix DNA single strands from human and
chimps, then human and gorilla. This allows
hybridisation to happen.
• To find out which hybrids are more similar heat them
up to find out at which temperature the strands
separate.
• The denaturation temperature is measured of the
hybrid and compared with that of non-hybrid human
DNA. The higher the difference in denaturation
temperature the bigger the difference in DNA.
• Q 5.46
DNA PROFILING
Use restriction enzymes to cut the DNA strand at
specific points to produce different sized
segments.
 Example: ECOR1 recognises the following
sequence GAATC and makes a staggered cut
between G and A
 If there are genetic differences the restriction
enzymes will not cut at the same sections and
will produce different sized segments.
 Write your own DNA sequence with 50 base
pairs. They must include the above sequence
(the one recognised by ECOR1) at least once (as
many times as you want and where you want)

DNA AND PROTEIN SEQUENCING
http://www.mwit.ac.th/~deardean/link/All%20Co
urse/pic/secuencia.swf
 Complete The Sanger Method

DNA MOLECULAR CLOCKS
PCR produces millions of copies of a DNA
molecule.
 Automated DNA sequencing machines work out
base sequences-by the Sanger Method
 As species evolve they accumulate random
mutations at a regular rate- (this is an
assumption) e.g. one every 10,000 years
 The more genetically different two species are the
more mutations there were, so the longer in the
past they shared a common ancestor. E.g. 10
mutations means they shared a common ancestor
100,000 years ago.

Activity 5.23 Evolution Revealed
horse
horse
zebra
rabbit
chicken
duck
snake
moth
zebra
rabbit
chicken
duck
snake
moth
rice
1
6
11
10
21
29
47
5
10
9
19
28
46
8
6
16
24
46
3
18
29
48
17
27
47
29
46
45
rice
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Q1-5. NOTE: Q4 is not just about sequencing but
also about using DNA as a molecular clock
EVOLUTION OBSERVED AND NATURAL
SELECTION AND CLIMATE CHANGE

The niche of polar bears:
They cannot hunt for seals because the sea is
unfrozen during late summer and early fall.
 Polar bears fast living off fat reserves then
 Polar bears also eat a wide variety of other wild
foods, including muskox, reindeer, birds, eggs,
rodents, shellfish, crabs, and other polar bears,
plants, including berries, roots, and kelp,
however none of these are a significant part of their
diet.
 The polar bear's biology is specialized to require large
amounts of fat from marine mammals, and it
cannot derive sufficient caloric intake from terrestrial
food.

EVOLUTION OBSERVED
Why is the population of polar bears decreasing?
 http://dsc.discovery.com/videos/global-warmingwhat-you-need-to-know-polar-bear-signs.html
 http://www.youtube.com/watch?v=axRX9_UyUOc
 http://www.youtube.com/watch?v=Kv9v9ALV3yk
&feature=related

Q 5.47-5.48
Natural Selection and Climate changeWhat are the major effects of climate change?
Give specific examples
 Milder winter temps, earlier springs, later
autumns, effect is greatest nearer poles where
the length and severity of the winter is shorterlength of growing season is longer
 What is the major selection pressure resulting
from climate change?
 Increased length of growing season
 In great and blue tits which characteristics were
selected for? Selected against?
 Which allele frequency changed? How?
 Q 5.49

SPECIATION
Define speciation:
 Formation of a new species
 Which occurs first- completed speciation or
isolation of populations?
 Isolation
 What might cause geographical isolation?
 A lake drying out, mountain range forming
 Give examples of the different types of isolation geographical
 ecological
 temporal
 sterility
 hybrid sterility
 behavioural

ACTIVITY 5.24 SPECIATIONDefine Species:
 Organisms which have similar
morphology, behaviour and physiology and
which are able to produce fertile offspring
when they reproduce
 Reproductively isolated:
 Unable to interbreed and produce fertile
offspring
Write a detailed explanation of how isolation
can lead to speciation. Use the interactive
tutorial and textbook
Brainstorm key words needed to answer questionIsolation,
geographical isolation,
gene pool,
different random mutation,
different selection pressure,
natural selection,
different alleles,
selected for,
survive,
reproduce,
pass on alleles,
reproductive isolation,
interbreed,
sterile offspring,
species
EXTENSION 5.7
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What are the four basic viewpoints? (note that this is
oversimplistic)
Where do you see yourself? Do you fit perfectly to one
viewpoint? A mixture/ between two or more
viewpoints? Another viewpoint?
Underline the key words which describe each each
viewpoint.
What might make a creation scientist not able to
accept the theory of evolution by natural selection?
 Not enough evidence for evolution leading to the
formation of new species. Do NOT beleive in macroevolution
 Read the Bible as one might read a
historical/scientific document written in the present
day- literal interpretation.
 Believe that the earth is about 10,000 years old and
most species or at least families were created as
they were today. A flood destroyed many species.
This is called Creationism.