Transcript Evolution

Evolution
WJEC Biology Module 1
Learning outcomes
• know that heritable variation is the
basis of evolution.
Adaptation and Evolution
• Organisms are well adapted to their
particular environment
• Variation occurs due to the
inheritance of different alleles
• These two ideas are closely related
and help explain evolution
Pupil Activity
• BBC video – the life of mammals
– Watch episode one – a winning design
 What features make mammals better adapted to
survive?
 What evidence for evolution is discussed in this film?
 Account for the differences between the types of
mammals found
– Monotremes – Australia
– Marsupials – Australia and South America
– Placentals – the rest of the world
Learning Outcomes
• Consider how individuals with
characteristics adapted to their
environment are more likely to survive
and breed successfully.
• Discuss the use and limitations of a
model to illustrate the effect of
camouflage colouring in predator and
prey relationships.
Camouflage Colouring
• Polar environments are covered with
snow
– It is a selective advantage for the
organisms to be white
• Prey
– Are camouflaged and will avoid being eaten
• Predator
– Can approach prey without being noticed
Adapting to Polar Environments
• Variation within a population will give
different shades
• Paler shades have a survival advantage
• Paler individuals survive to breed
• Pass on “pale” genes to their offspring
• More pale individuals in the next
generation
• Over time the population changes
making them better adapted to the
environment.
Pupil Activity
• Think of an animal which is
camouflaged in it’s habitat.
• Explain in terms of evolution how that
colouration came about.
Pupil Activity
• Modelling Natural Selection using predation
and camouflage
• In the natural environment you must consider
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Size of population
Immigration or emigration
Random mutation
Do variations influence survival in other ways
• In the lab we can design experiments to
demonstrate this!!
Learning Outcomes
• know that the genes which have
enabled these better adapted
individuals to survive are then passed on
to the next generation.
– This is natural selection as proposed by
Charles Darwin and accepted by scientists.
Work continues to fully understand the
process as further evidence from genetics
and molecular biology is collected. The
process of natural selection is sometimes too
slow for organisms to adapt to new
environmental conditions and so organisms
may become extinct.
Evolution
• Charles Darwin developed the theory of natural
selection as a driving force of evolution
• Two facts
– Organisms have a tendency to overproduce,
meaning offspring are more numerous than their
parents
– Populations remain relatively stable
• Deductions
– “struggle for existence” – competition
– Better adapted survive to reproduce
– favourable adaptations inherited
The theory of natural selection
• Variation
• Overproduction
• Competition for resources - Struggle for
existence
• Best adapted organisms survive – “Survival of
the fittest”
• Advantageous features inherited
• Gradual change in the population
Darwin’s Finches
• Darwin noticed that there were species of finch
were only found on certain islands in the
Galapagos Archipelago
• Each species had their own specific characteristics
– Beak shape and size seemed to reflect the food they ate
Darwin’s Ponderings
• Why should the
species which are
supposed to have
been created in the
Galapagos
Archipelago, and
nowhere else, bear so
plain a stamp of
affinity to those
created in America?
Darwin’s Finches
• There were two hypotheses
• Hypothesis 1
– God created all finches separately
• Science can not prove or disprove the actions
of a god, as the laws of science are not
obeyed
• Any hypothesis involving the actions of a god
can not be a “scientific hypothesis”
• Hypothesis 2
– The characteristics has been acquired
and then inherited
So which Hypothesis
• Darwin’s observations did not support
these hypotheses.
• Darwin developed his Theory of Natural
Selection to explain the evidence
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Overproduction
Variation
Better adapted survive
Breed and pass on genes
Characteristic inherited and the species
gradually change
Theory or Hypothesis or Law
• Theory
– An idea that seeks to explain a scientific
phenomena
– Generally accepted
– Supported by evidence
• Hypothesis
– A suggested explanation for an event or
observation
– A statement which can be tested by
experimentation
• Law
– Describes how something works and can be
used to predict things
Extinction
• Species may become extinct due to a
variety of reasons
– It has failed to adapt successfully to its
environment
– Another species is better adapted and it is
out competed
– Sudden change in environment and the
species can not survive in the new
conditions
Peppered Moth
• Peppered moths rest on silver birch
tree trunks with their wings
outstretched, this behaviour can make
them easy prey for birds. Originally the
peppered moth was only recorded in
the paler speckled form, but during
the industrial revolution in the UK
(about 200 years ago) dark coloured
peppered moths started to be
recorded.
• Whilst the numbers of the dark form of
the peppered moth increased
dramatically, the paler speckled form
became scarce in some areas.
However, in more recent times the
numbers of the dark form have
declined relative to the pale form.
Peppered moth
“A modern example of evolution”
Pale coloured, speckled peppered moth
Peppered moth
“A modern example of evolution”
Dark coloured peppered moth
Peppered moth
“A modern example of evolution”
Peppered moths on tree trunk
Peppered Moth
Jan 08 (H) Question 8
Selection in action - banded snails
• The purpose of this activity is:
– to interpret data about changing
populations using ideas about natural
selection
– to make predictions about how
populations might change in the future
Banded Snails - Answers
1. This could be because the yellow
snails are better camouflaged in June
– Give a suggested reason why
2. The woodland results show that the
snails are more commonly not yellow,
and, usually have one or no bands.
3. In hedgerows and grassland, around 65
% of the snails (±35%) are yellow, and
35% (±30 %) have one or no band – so
most have more than one band.
4. Yellow snails are more common in
hedgerows and grassland. If the amount
of woodland decreased, it is possible
that the numbers of yellow snails would
increase.
Natural Selection In Guppies
WJEC Exam Question June 08 (Higher)
• (a)
– 1. Variation in colour/pattern
– 2. results from mutation/change in genes/DNA
– 3. Natural selection by predation/survival of the
fittest
– 4. and sexual selection/females select most
colourful males to breed
– 5. Most colourful males survive/are at an
advantage
– 6. to pass on genes
• (b)
– (i) Evolution
– (ii) (Charles) Darwin
Natural Selection – Guppies
A perfect Answer
• Variation in colour
• results from mutation
• Natural selection by predation and females
select most colourful males to breed
• Most colourful males survive
• to pass on genes
Learning outcomes
• understand that evolution is ongoing
as shown by the development of
resistance to antimicrobial chemicals
by bacteria or Warfarin resistance in
rats
Natural Selection in Action
Antibiotic resistance in bacteria
Super-rats in Wales
Antibiotic resistance in Bacteria
• Antibiotics are chemicals designed to kill
bacteria
• Mutations in genes have led to the
development of anti-biotic resistance in some
strains of bacteria
– Mutated bacteria has a selective advantage
– reproduces
– Mutated gene passed on to next generation
– Population of bacteria becomes resistant to
anti- biotics
• Penicillin resistance – bacteria produce an
enzyme that can break down penicillin
• New problems
– Resistant strains of tuberculosis bacteria
– MRSA (methicillin resistant staphylococcus
aureus)
Super-rats in Wales
• Warfarin is a popular rat poison
– Prevents blood clotting
– Capillaries burst
– Rat bleeds to death
• Some rats have developed Warfarin resistance
– Blood clotting is not affected by warfarin
WJEC Exam Question 7 - Jan 07
• (a) Rats / rodents / mice
• (b)
– (i) mutation
– (ii)
genes / DNA / Alleles
• (c)
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Adaptation / mutation
Helped survival / an advantage
Passed on
Through genes
Natural selection / survival of the fittest (to breed)
Lead to evolution of a new type
• (d)
– Shows a change in a species
– Taking place in/over very short time
– Illustrates natural selection / survival of the fittest
Fossil evidence
• Fossils are “remains” of plants and animals from
many years ago which are found in rocks.
Fossils can be formed from:
– Hard parts of animals which do not decay easily
– Preservation – where one of the factors necessary
for decay is absent e.g. mummification
– Petrification - minerals replace parts of plants and
animals as they decay.
– Casts – the decaying matter leaves an imprint
behind in the rock
Practice Questions
Bird Skeleton Jan 09
• (a)
– Fossils [1]
• (b)
– Makes (skeleton) light weight (for flying)
[1]
– (not: helps them to fly/ref. insulation)
• (c)
– Shows features of birds and
reptiles/description e.g. has teeth and
wings [1]
– Reptile remains pre-date bird remains /
Reptile remains found in rocks older than
rocks in which birds remains are found / or
ref to actual numbers of years [1]
• (d)
– Air spaces an advantage [1]
– Genes passed on (to future generations)
[1]
– reference to mutation occurring [1]
Practice Questions
Moa and Ostrich
Practice Questions
Humans – milk digestion