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Summary Grade 12 IEB Life science/biology strand 4 (Evolution): 4.1 (Origin of an idea about origins) £3.52
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Summary Grade 12 IEB Life science/biology strand 4 (Evolution): 4.1 (Origin of an idea about origins)

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  • Module
  • Life Sciences
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  • 12th Grade

This aesthetic, in-depth, neatly typed document summarises 4.1 of strand 4 (Evolution) of the IEB grade 12 mind action series textbook: Origin of an idea about origins. It includes the full 4.1 Origin of an idea about origins syllabus as well as additional class notes, own research notes and all re...

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Document information

  • January 14, 2023
  • 6
  • 2022/2023
  • Summary

Subjects

  • ieb
  • matric
  • grade 12
  • life science
  • biology
  • mind action series
  • typed
  • aesthetic
  • diagrams
  • strand 4
  • evolution
  • summary
  • notes
  • 41
  • origin of an idea about origins

Written for

  • 12th Grade
  • Life Sciences
  • 200
All documents for this subject (1211)

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Content preview

Evolution:
Grade 10 recap:

• Earth is 4,6 billion years old

• Earth's crust is built up in layers over time

• Dating of fossils - relative & radiometric dating determine age of rock

• At least 5 mass extinctions have occurred

• SA is rich in fossils:

- Stromatolites (cyanobacteria) - Mpumalanga

- Primitive land plants (fern) - KwaZulu Natal

- Coelacanth (extant species) (transitional species)

- Mammal-like reptiles - Karoo

- Australopithecus Africanus & Homo Ergaster - Sterkfontein caves & Cradle of Mankind



Origin of an idea about origins:
Evolution: Gradual change in gene pool of population due to mutation, natural selection and genetic

drift (descent with modi cation)

• Micro-evolution: evolution within a species

• Macro-evolution: Descent of di erent species from common ancestor



Mechanisms of evolution: Human-driven evolution:

• Natural selection - Arti cial selection

• Polyploidy - In and out breeding eg. dogs, crops

• Gene ow

• Genetic drift

• Mutations

, Erasmus Darwin: (1731 - 1802)

• Proposed that all life descended from common ancestor and that species have changed over time



Jean-Baptiste Lamarck: (1774 - 1829)

• Concluded that:

- Living species are di erent to fossils, therefore life forms changed

- Domestication and selective breeding resulted in animals & plants changing

- Cross-breeding of plants led to new characteristics

• Suggested that organisms changed in order to survive in new environments and that these

acquired changes were passed to o spring. How change took place:

- Use and disuse of body parts

- Inheritance of acquired characteristics (through use & disuse)

- eg. long neck of gira e (he believed it grew longer as trait was passed onto o spring over

generations)

- Hypothesis was incorrect (phenotypic changes don't altar genotype of egg or sperm cells)



Charles Darwin: (1809 - 1882)

• Realised that:

- Earth is very old = time for species to evolve

- Has been great geological change over time

- Isolation leads to species changing

• Published book: 'The Origin of Species'. Explained 2 hypotheses:

- Descent with modi cation (evolutionary change)

- Natural Selection (Individuals best adapted to environment will survive)

• Darwin's explanation of descent with modi cation:

- All related organisms come from common ancestor

- Ancestral species spread into new habitats & adapted to new conditions = new species

- Diversi cation was by branching

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