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...
- 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
The benefits of buying summaries with Stuvia:
Guaranteed quality through customer reviews
Stuvia customers have reviewed more than 700,000 summaries. This how you know that you are buying the best documents.
Quick and easy check-out
You can quickly pay through credit card or Stuvia-credit for the summaries. There is no membership needed.
Focus on what matters
Your fellow students write the study notes themselves, which is why the documents are always reliable and up-to-date. This ensures you quickly get to the core!
Frequently asked questions
What do I get when I buy this document?
You get a PDF, available immediately after your purchase. The purchased document is accessible anytime, anywhere and indefinitely through your profile.
Satisfaction guarantee: how does it work?
Our satisfaction guarantee ensures that you always find a study document that suits you well. You fill out a form, and our customer service team takes care of the rest.
Who am I buying these notes from?
Stuvia is a marketplace, so you are not buying this document from us, but from seller Lindyprinsloo. Stuvia facilitates payment to the seller.
Will I be stuck with a subscription?
No, you only buy these notes for $4.44. You're not tied to anything after your purchase.
