Great British Scientists Learning Objective: To explore the work of Anning, Wallace and Darwin on evolution. www.planbee.com Next
Great British ScientistsLearning Objective:
To explore the work of Anning, Wallace and Darwin on evolution.
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How do we know that dinosaurs
existed?
What could we use as evidence to prove their
existence?
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The fossils we have found can be dated back to millions of years ago. They show us creatures that no longer
exist on our planet. Fossils can give so much information about how
dinosaurs lived, including diet and social habits!
Before her discoveries many people did not accept evolution or extinction as theories because it would have meant that God’s creations were not created perfectly and
the world has changed since it was created.
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Meet Mary Anning. Her work helped push scientists of the 19th century to begin thinking
about evolution, extinction and how life on Earth has developed and changed.
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Anning was a palaeontologist who would comb the shore were she lived to find what she called
‘curiosities’. We now call them fossils and Anning is named as one of the greatest fossil hunters ever!
By Niki Odolphie - Natural History Museum, CC BY 2.0, https://commons.wikimedia.org/w/index.php?
curid=4296301
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How do you think Anning’s discoveries like this Rhomaleosaurus fossil helped to prove the
theories of extinction and evolution i.e. species could die out or change over long periods of time?
Do you know of any species that
have become extinct?
www.planbee.comNextBack By hairymuseummatt - https://www.flickr.com/photos/hmnh/3033749380/, CC BY-SA 2.0, https://commons.wikimedia.org/w/index.php?curid=6833148
Fossils are physical proof that organisms existed in the past, that may
not exist today. This evidence can be used to to show thatthe organism has changed over time or became extinct.
What changes can
you spot between a human skull
and our Neanderthal ancestor?
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Anning’s work led to other scientists beginning to research animal and
plant species to observe similarities and differences between them.
These two scientists in particular were working on the same theory: Evolution and natural
selection. Have you heard of
them?
Alfred Russel Wallace Charles Darwin
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Both men had a similar theory about evolution: that species of
animals and plants had changed over long periods of time. Wallace even wrote to Darwin explaining his ideas. This pushed Darwin into finishing his book quickly so he could publish his ideas
first, meaning he got most of the credit and attention for the theory.
But living things can’t just decide to change when they feel like it. So how did these
changes happen?
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The theory of natural selection uses the fact that a living organism’s offspring
are different to their parents in small ways. These small variations or sometimes mutations within a species can lead to those organisms being more successful than their ancestors and
passing on their successful features to their own offspring.
These successful features are called advantageous features; they provide the organism with an advantage over others.
Let’s look at an example.
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A species of flower reproduces through insects pollinating them. They produce seeds which grow into new plants which are similar
to their parents with slight variations.
A small mutation develops in one of the offspring, meaning it grows
different coloured petals.
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This new colour is much more attractive to insects as they can
see the flower more clearly. They visit this flower more often,
making this feature advantageous.
More insects pollinate this flower and the mutation is spread among
the species as the offspring inherit it from their parents. These flowers receive more attention from the
pollinating insects.
Think, pair, share... What do you think would happen to the flowers without the mutation?
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The flowers without the mutation are not visited as
much by the pollinating insects and could slowly become less
common or even die out altogether.
Wallace and Darwin described natural selection as ‘survival of the fittest’ meaning any weak or
disadvantageous features would slowly be left out and not continued in the
species. Remember though: these changes happen by chance over thousands if not millions
of years!
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Not all mutations are advantageous. Some might lead to an organism being
susceptible to certain diseases or might mean they can’t move or behave in the same way as others from their species.
Some mutated traits may have been advantageous at one point in
history, but a change in environment may change the features into
disadvantageous ones. This is called mismatched evolution. Take the
dodo bird for example…
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Dodos lived in a habitat with few to no predators. They didn’t have to flee
quickly or be scared of other creatures around them. Flying and the stress of fleeing consumes a lot of energy so, over
time, the dodo slowly lost these abilities and traits.
When a new predator arrived (humans), the dodos weren’t
scared of them and couldn’t fly away, making them easy to hunt. They were hunted so much they
became extinct.
Look at the traits on the
next slide and decide if they’re advantageous or disadvantageous
for the polar bear.
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Plenary
This polar bear lives in the Arctic where temperatures can reach below -50°C. They
are carnivores whose prey live in and out of the water.
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Thick, hollow furLarge, flat feet
Powerful front limbs
Weigh around 410 kg
Have large amounts of fat
Carnivorous
Small ears
Live alone Apex predator
Good sense of smell