Transcript 7.4 Extinction - science

Key words: change, disease, predator,
competitor,
climate
change
GCSE
CORE
Biology
1b Evolution
and Environment
Objective
Why do species become extinct?
Success Criteria
By the end of the lesson I:
• can explain that many organisms have evolved and then
become extinct over the lifetime of the earth
• can explain that ‘extinction’ means that every organism of a
particular species has died.
•There are a number of changes that can cause a species to
become extinct
GCSE
Biology 1b Evolution and Environment
CORE
Dead as a dodo
Why did the dodo become extinct?
GCSE
Biology 1b Evolution and Environment
CORE
Why did the dodo become extinct?
The dodo was a large flightless bird
that lived on the island of Mauritius.
It nested on the ground in forests,
producing one egg at a time.
When human settlers arrived on the
island in the mid-1600s, they brought
animals such as rats and dogs to the
island, which ate the dodos’ eggs.
The settlers chopped down the forests in which the dodos
lived, and may have even hunted the dodo for food.
The dodo became extinct sometime in the late 1600s.
What traits might have helped the dodo to survive longer?
GCSE
Biology 1b Evolution and Environment
CORE
Dead as a dodo
Why did the dodo become extinct?
•New predator
•Disease
•Destruction of habitat
•Nests/eggs being predated
GCSE
Biology 1b Evolution and Environment
CORE
Extinction means that a species that had once existed has now been wiped out
Extinction can be caused a number of factors but
always involves a change in circumstance.
• A new disease may kill all members of a species
• Climate change may make it too cold or hot, wet or
dry, for a species and reduce it food supply
• A new predator may evolve or be introduced to an
area that effectively kills and eats all of the species
• A new competitor may evolve or be introduced into
an area. The original species may be left with too
little to eat
• The habitat may be destroyed
GCSE
Biology 1b Evolution and Environment
CORE
Extinction of dinosaurs
The dinosaurs ruled the earth for millions of years but when the whole
environment changed, they could not adapt & died out. By the time things
began to warm up again, mammals, which could control their own body
GCSE
CORE
1bdominant.
EvolutionThe
andage
Environment
temperature, wereBiology
becoming
of the reptile was over!
EXAM TIP
When answering a question on extinction use
the word
‘change’
If there is no change then species
do not become extinct!
GCSE
Biology 1b Evolution and Environment
CORE
Multiple-choice quiz
GCSE
Biology 1b Evolution and Environment
CORE
EXAM PRACTICE
The Galapagos Islands are a group of islands in
the Pacific Ocean. The nearest country on the
mainland is Ecuador, 1000 km away. By some
means, a few seed-eating finches were the first
birds to reach the islands. This single ancestral
species has since evolved into many different
species. Charles Darwin visited the islands and
noted that each species had a beak adapted to
the type of food it ate.
Using the theory of natural selection, explain how
the ancestral species might have evolved into
birds with different-shaped beaks……6 marks
GCSE
Biology 1b Evolution and Environment
CORE
EXAM PRACTICE
• When the ancestral species arrived on the islands there would be no
competition from other birds.
• There would be a variety of different types of food available, e.g.
vegetation, seeds, insects.
• The ancestral species would have bred rapidly and built up a large
population and so created competition between its members for
food.
• Sexual reproduction and/or mutations over many generations would
have created variety amongst the individuals in the population.
• Some of this variety would have been in the types of beak, with
different ones being suited to different food sources, e.g. a
longer, thinner beak would allow its owner to capture insects in small
holes or crevices that were inaccessible to birds with shorter and
wider beaks.
• These birds with thinner beaks had an advantage over the other
birds of an additional food supply and were therefore more likely
to survive long enough to mate and raise offspring.
• These offspring would most probably possess the same genes for
a long, thin beak that their parents had and so they too were more
likely to survive.
GCSE
Biology 1b Evolution and Environment
CORE
Evolution or design?
Some people reject evolution and natural selection in favour
of alternative explanations such as intelligent design (ID).
According to ID, organisms are too complex to have arisen
by evolution alone, and their development must have been
guided by a higher intelligence at some point.
Supporters of ID claim it is a valid theory based on scientific
evidence, but critics say it is simply a disguised version of
creationism.
What do you think about teaching intelligent design in a
science class?
GCSE
Biology 1b Evolution and Environment
CORE
Science vs religion
Read page 116 and answer
Why is it important for students to know
about evolution?
Include
GCSE
– evidence of evolution
- the current scientific theories
- final comment stating your opinion
Biology 1b Evolution and Environment
CORE
Objective
Why do species become extinct?
Success Criteria
By the end of the lesson I:
• can explain that many organisms have evolved and then
become extinct over the lifetime of the earth
• can explain that ‘extinction’ means that every organism of a
particular species has died.
•There are a number of changes that can cause a species to
become extinct
GCSE
Biology 1b Evolution and Environment
CORE