Grade 12 Term 3 Evolution slides to help students understand the content better, look at it from a different viewpoint and excel further in their studies. This can be used as guide however it all depends on learners study methods and whatever works best for them. We hope this is useful to our students and goodluck!

2. Evidence
OF
evolution
Evidence from fossils: A study of fossils (thousands of fossil fragments) has
shown traits that distinguish us from and from African apes.
Genetic evidence: According to scientists, if two species have the same DNA
structure, they are likely to be related and have a common ancestor.
Similarity in gene sequence, similarity in functional DNA regions, and similarity
in mutations (mitochondrial DNA)
Compared to distant species, closely related species are more similar to one
another.
Cultural evidence: Language and tool studies are frequently utilised to
demonstrate cultural similarities and differences between humans and African
apes.

3. Sources
of
variation
The same species' genotypes and
consequently phenotypes (appearances)
vary from one another because:
• A genetic material exchange occurs
during Prophase I of meiosis, resulting
in different combinations of maternal
and paternal genetic material in each
new cell produced as a result of
meiosis.
• Each each cell produced by meiosis
contains a unique combination of
chromosomes/chromatids due to the
random arrangement of maternal and
paternal chromosomes at the equator
during metaphase.
• Offspring produced by random
meiotic fertilisation between various
egg cells and various sperm cells differ
from one another.
• Each mating pair produces a unique
set of offspring when organisms of the
same species randomly mate.
• A mutation modifies the chromosome
or gene's structure.

6. -Humans represent the selective force
-Selection is in response to satisfying human needs
-It may involve 1 or more species (Cross-breeding)

7. Punctuated equilibrium is a hypothesis that explains the progression of evolution by natural selection:
- Evolution is not always slow, as proposed by Lamarckism and Darwinism, according to punctuated equilibrium.
- Evolution entails vast periods of time during which species do not change or change just slightly (this is known as
homeostasis).
- This alternates with (is interrupted by) brief moments of fast change.
- As a result, new species emerge in a relatively short period of time, compared to
periods of no/little change.
- This is confirmed by the lack of transitional fossils (often referred to as'missing links') indicating an era of rapid transformation.

8. A geographical barrier, such as a river, might cause a population of one species to split.
Because of this, the two populations are unable to hybridise. Between the two
populations, there is no gene flow.
In every population, natural selection operates independently. This is a result of the
various environmental factors. As a result, throughout time, the two groups diverge in
terms of genotype and phenotype. They won't be able to cross again, even if the two
populations eventually mixed. Speciation is the process by which a population splits into
one or both new species.

10. •
•
•
•

12. Large brain
Eyes in
front
Freely rotating arms
Long upper
arms
Bare finger tips or nails instead of claws
Upright
posture

13. Differencesbetween
humans(HomoSapiens)
andAfricanApes

16. According to the 'Out of Africa' theory, modern humans first appeared in Africa before
migrating to other continents.
The following arguments have been made in favour of this claim:
The earliest bipedal organisms, including australopithecines and Homo habilis, were
discovered in Africa.
Africa is where Homo erectus' earliest fossil remains were discovered.
The oldest known female ancestors of humans came from Africa, according to an
analysis of modifications in mitochondrial DNA.

17. Credits
Lamarck and Darwin
Speciation
Mind the Gap Life Science Grade 12 Study Guide