Great British Scientists Learning Objective: T o explor e the w - - PowerPoint PPT Presentation

Great British Scientists

Learning Objective: T

• explor

e the w

• rk of Anning, W

allace and Darwin on evolution.

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How do we know that dinosaurs existed? W hat could we use as evidence to prove their existence?

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The fossils we have found can be dated back to millions

• f years ago. The

y s how us cr eatur es that no longer exist on our planet. Fossils can g ive so much information about how dinosaurs lived, including diet and social habits!

Befor e her discoveries many people did not accept evolution or extinction as theories because it w

• uld have meant that God’s

cr eations wer e not cr eated perfectly and the w

• rld has changed since it was cr

eated.

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Meet Mary Anning . Her w

• rk helped pus

h scientists of the 19th century to beg in thinking about evolution, extinction and how life on Earth has developed and changed.

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Anning was a palaeontolog ist who w

• uld comb the s

hor e wer e s he lived to find what s he called ‘curiosities’. W e now call them fossils and Anning is named as one

• f the gr

eatest 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?

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

Fossils ar e physical proof that

• rganisms existed in the past, that may

not exist today . This evidence can be used to to s how that the organism has changed over time or became extinct. W hat changes can you spot between a human skull and our Neanderthal ancestor?

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Next Back Anning’s w

• rk led to other

scientists beg inning to r esearch animal and plant species to observe similarities and differ ences between them. These tw

• scientists in

particular wer e w

• rking
• n the same theory:

Evolution and natur al selection. Have you hear d of them?

Alfr ed Russel W allace 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. W allace even wrote to Darwin explaining his ideas. This pus hed Darwin into finis hing his book quickly so he could publis h his ideas first, meaning he got most of the cr edit and attention for the theory . But living things can’t just decide to change when the y feel like it. So how did these changes happen?

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The theory of natur al selection uses the fact that a living organism’s offspring ar e differ ent to their par ents in small ways. These small variations or sometimes mutations within a species can lead to those organisms being mor e successful than their ancestors and passing on their successful featur es to their own offspring . These successful featur es ar e called advantageous featur es; the y provide the

• rganism with an advantage over others.

Let’s look at an example.

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A species of flower r eproduces through insects pollinating them. The y produce seeds which grow into ne w plants which ar e similar to their par ents with slight variations. A small mutation develops in one

• f the offspring, meaning it grows

differ ent colour ed petals.

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This ne w colour is much mor e attr active to insects as the y can see the flower mor e clearly . The y visit this flower mor e often, making this featur e advantageous. Mor e insects pollinate this flower and the mutation is spr ead among the species as the offspring inherit it from their par

• ents. These flowers

r eceive mor e attention from the pollinating insects. Think, pair , s har e... W hat do you think w

• uld happen to the flowers without the mutation?

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The flowers without the mutation ar e not visited as much by the pollinating insects and could slowly become less com mon or even die out altogether . W allace and Darwin described natur al selection as ‘survival of the fittest’ meaning any weak or disadvantageous featur es w

• uld slowly be left out

and not continued in the

• species. Remember

though: these changes happen by chance over thousands if not millions

• f years!

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Not all mutations ar e advantageous. Some might lead to an organism being susceptible to certain diseases or might mean the y can’t move or behave in the same way as others from their species. Some mutated tr aits may have been advantageous at one point in history , but a change in environment may change the featur es into disadvantageous ones. This is called mismatched evolution. T ake the dodo bir d for example…

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Dodos lived in a habitat with fe w to no pr

• edators. The

y didn’t have to flee quickly or be scar ed of other cr eatur es around them. Flying and the str ess of fleeing consumes a lot of energy so, over time, the dodo slowly lost these abilities and tr aits. W hen a ne w pr edator arrived (humans), the dodos wer en’t scar ed of them and couldn’t fly away , making them easy to hunt. The y wer e hunted so much the y became extinct.

Look at the tr aits on the next slide and decide if the y’r e advantageous or disadvantageous for the polar bear .

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Plenary This polar bear lives in the Arctic wher e temper atur es can r each below -50°C. The y ar e carnivor es whose pr e y live in and out of the water .

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Plenary

Thick, hollow fur Large, flat feet Powerful front limbs W eigh around 410 kg Have large amounts of fat Carnivorous Small ears Live alone Apex pr edator Good sense of smell