Great British Scientists Learning Objective: T o explor e the w ork of Anning, W allace and Darwin on evolution. Next www.planbee.com
How do we know that dinosaurs existed? W hat could we use as evidence to prove their existence? Back Next www.planbee.com
The fossils we have found can be dated back to millions of 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! Back Next www.planbee.com
Meet Mary Anning . Her w ork helped pus h scientists of the 19th century to beg in thinking about evolution, extinction and how life on Earth has developed and changed. Befor e her discoveries many people did not accept evolution or extinction as theories because it w ould have meant that God’s cr eations wer e not cr eated perfectly and the w orld has changed since it was cr eated. Back Next www.planbee.com
By Niki Odolphie - Natural History Museum, CC BY 2.0, https://commons.wikimedia.org/w/index.php? curid=4296301 Anning was a palaeontolog ist who w ould 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 of the gr eatest 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 Next www.planbee.com
Fossils ar e physical proof that organisms 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 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 Next www.planbee.com
Anning’s w ork led to other scientists beg inning to r esearch animal and plant species to observe similarities and differ ences between them. These tw o scientists in particular wer e w orking on the same theory: Evolution and natur al selection. Have you hear d of them? Alfr ed Russel W allace Charles Darwin Back Next www.planbee.com
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? Back Next www.planbee.com
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 organism with an advantage over others. Let’s look at an example. Back Next www.planbee.com
A species of flower r eproduces through insects pollinating them. A small mutation develops in one The y produce seeds which grow of the offspring, meaning it grows into ne w plants which ar e similar differ ent colour ed petals. to their par ents with slight variations. Back Next www.planbee.com
Mor e insects pollinate this flower This ne w colour is much mor e and the mutation is spr ead among attr active to insects as the y can the species as the offspring inherit it see the flower mor e clearly . The y from their par ents. These flowers visit this flower mor e often, r eceive mor e attention from the making this featur e advantageous. pollinating insects. Think, pair , s har e... W hat do you think w ould happen to the flowers without the mutation? Back Next www.planbee.com
W allace and Darwin described natur al selection as ‘survival of the fittest’ meaning any weak or disadvantageous featur es w ould slowly be left out The flowers without the and not continued in the mutation ar e not visited as species. Remember much by the pollinating insects though: these changes and could slowly become less happen by chance over com mon or even die out thousands if not millions altogether . of years! Back Next www.planbee.com
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… Back Next www.planbee.com
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. Back Next www.planbee.com
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 . Look at the tr aits on the next slide and decide if the y’r e advantageous or disadvantageous for the polar bear . Back Next www.planbee.com
Plenary Have large amounts of fat Powerful front limbs Carnivorous Small ears W eigh around 410 kg Apex pr edator Live alone Good sense of smell Thick, hollow fur Large, flat feet Back www.planbee.com
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