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