Great British Scientists

Learning Objective: To explore the work of Anning, Wallace and Darwin on evolution.

www.planbee.com Next How do we know that dinosaurs existed?

What could we use as evidence to prove their existence?

Back www.planbee.com Next 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!

Back www.planbee.com Next 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.

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.

Back www.planbee.com Next By Niki Odolphie - Natural History Museum, CC BY 2.0, https://commons.wikimedia.org/w/index.php? curid=4296301

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!

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?

Back www.planbee.com Next Fossils are physical proof that organisms existed in the past, that may not exist today. This evidence can be used to to show that the organism has changed over time or became extinct.

What Do you changes can know of any you spot species that between a have human skull become and our extinct? Neanderthal ancestor?

By hairymuseummatt - https://www.flickr.com/photos/hmnh/3033749380/, CC BY-SA 2.0, https://commons.wikimedia.org/w/index.php?curid=6833148

Back www.planbee.com Next 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

Back www.planbee.com Next 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?

Back www.planbee.com Next 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.

Back www.planbee.com Next A species of flower reproduces through insects pollinating them. A small mutation develops in one They produce seeds which grow of the offspring, meaning it grows into new plants which are similar different coloured petals. to their parents with slight variations.

Back www.planbee.com Next More insects pollinate this flower This new colour is much more and the mutation is spread among attractive to insects as they can the species as the offspring inherit it see the flower more clearly. They from their parents. These flowers visit this flower more often, receive more attention from the making this feature advantageous. pollinating insects.

Think, pair, share... What do you think would happen to the flowers without the mutation?

Back www.planbee.com Next Wallace and Darwin described natural selection as ‘survival of the fittest’ meaning any weak or disadvantageous features would slowly be left out The flowers without the and not continued in the mutation are not visited as species. Remember much by the pollinating insects though: these changes and could slowly become less happen by chance over common or even die out thousands if not millions altogether. of years!

Back www.planbee.com Next 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…

Back www.planbee.com Next 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.

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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.

Look at the traits on the next slide and decide if they’re advantageous or disadvantageous for the polar bear.

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Have large amounts of fat Carnivorous Powerful front limbs

Small ears Weigh around 410 kg

Live alone Apex predator

Good sense of smell Thick, hollow fur Large, flat feet

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