Evolution

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rebeccachelsea
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B1 Topic 1 - Evolution notes
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Evolution
1 Extreme Environments
1.1 Deep Sea
1.1.1 No light as sun cannot penetrate that deep so plants cannot photosynthesise and grow which means food is scarce for other organisms.
1.1.2 Angler fish have a rod-shaped spine sticking out its face which gives out light to attract prey to eat.
1.1.3 Rat-tail fish have huge mouths to scoop up particles of food along the seabed.
1.1.4 Deep-sea fish have huge eyes adapted to the dark and long feelers to help locate prey.
1.2 Volcanic Vents
1.2.1 Send out hot water and minerals into the cold ocean.
1.2.2 Chemicals from vents support bacteria that can make own food with chemical energy (chemosynthesis). Like photosynthesis but uses chemical energy instead of light as it is so dark.
1.2.3 Bottom of the food web (producers) as animals feed on bacteria.
1.2.4 Extremely hot and under high pressure so bacteria adapted to cope.
1.3 Polar Regions
1.3.1 Polar Bears
1.3.1.1 Round shape so small surface area compared to volume which reduces heat loss.
1.3.1.2 Thick layer of blubber for insulation and used as an energy store when food is scarce.
1.3.1.3 Fur coats trap warm air next to the skin and greasy fur sheds water to prevent cooling due to evaporation.
1.3.1.4 Big feet help to spread the weight to stop sinking into snow or breaking thin ice.
1.3.1.5 White fur for camoflage.
1.3.2 Penguins
1.3.2.1 Thick layer of insulating fat and oily feathers to shed water and reduce heat loss.
1.3.2.2 Huddle together in groups to conserve heat.
1.3.2.3 Streamlined body to reduce water resistance so they can swim fast and catch fish.
2 Natural Selection (Charles Darwin)
2.1 1) There is variation within populations as individuals have differences in their genes,
2.2 2) Most organisms give birth to more young than can survive to adulthood.
2.3 3) Most don't increase in size as individuals compete with each other for resources that are limited in supply (e.g. food, water, mates).
2.4 4) Individuals with characteristics that are better adapted have a better chance of survival so will breed more successfully.
2.5 5) Genes responsible for useful characteristics are more likely to be passed on to the next generation.
2.6 6) The ones less well adapted are less able to compete and less likely to survive and reproduce.
2.7 7) Overtime there will be a higher proportion of individuals with better characteristics compared to those with poorly adapted characteristics. Eventually they may even be lost.
3 Evolution is the slow and continuous change of organisms between generations.
4 Scientific Research
4.1 Evidence
4.1.1 Resistant Organisms
4.1.1.1 Warfarin was used to kill rats bit certain genes gave rats resistance to it making them more likely to survive and breed so now there are rat populations that are warfarin-resistant.
4.1.2 DNA Research
4.1.2.1 All organisms have evolved from shared common ancestors. Closely related species diverged more recently due to gradual DNA changes. Therefore, organisms that have diverged more recently have similar DNA, for example in humans and chimps.
4.2 Scientific Community
4.2.1 Accept the theory of evolution as they've shared and discussed evidence to make sure its valid and reliable.
4.2.1.1 Publish their work in scientific journals so other scientists can repeat experiments to see if the same results come up to be confident of its reliability.
4.2.1.2 Peer reviewed to check its valid and that the experiment has been carried out to the highest possible standard.
4.2.1.3 Conferences to meet, discuss and share the latest hypotheses and work.
5 Speciation
5.1 Occurs when populations of the same species become so different that they can no longer breed to produce fertile offspring.
5.2 1) They are isolated or separated by physical barriers (e.g. floods or earthquakes can geographically isolate some members from the main population.
5.3 2) Conditions on each side will differ slightly (e.g. different climate) so different characteristics will become more popular due to natural selection.
5.4 3) Eventually individuals will have changed so much that they wont be able to reproduce fertile offspring so they will now be 2 separate species.
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