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Grade 12 IEB Evolution Notes

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Comprehensive notes on evolution, theory and speciation, as well as human and hominid evolution. Written according to 2026 SAGS, please check for accuracy.

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, Evolution

Definitions

·


fact :
something that we know to exist or be true. In science
,
It must be testable
through experiment be +



Repeatable
hypothesis
: an educated guess about
on observation that is under investigation expressed a s a
,




statement which includes the variables + is testable


theory :
When something can't be tested / repeated but there is logical evidence to it
being true

·


model : a simplified description of a
system to help explain It through calculations +
predictions
·



Law : statement of fact to explain (in concrete terms)on action/set of actions ; accepted as true +
absolute

Biological purpose of life : to procreate ,
reproduce+ keep species going
·




diversity :
a range/variety of different characteristics/species
·




Biodiversity :
a wide variety of different organisms (plant ,
micro animals in their natural habitat
,



condition
:


·


extinction on irreversible where a species or group
·



evolution :
gradual process by which present day diversity of life arose from the earliest (primitive) ags ·

Biological evolution :
process of change over time as a result of passing on altered genes/mutations


·




History of Life on Earth

I . Big Bang
:
14 5 .

by a
-

universe created arche


formed 4 6
Earth bya
:
2 .
wa s .


-




3 .
First life appears :
3 7 .
by a palaeozoic
3 8 Proterozoic
↳
prokaryotes :
.
by a

↳
photosynthesis begins
:
3 .
A byasadvanced life can form

↳
eukaryotes
:
2 bya




I
↳ multicellular life I :




by a -




↳
simple animals Goomya "combrian explosion
:




combrian
↳
arthropods : STomya

↳ complex animals Ssomya
:
&




↳ fish+ proto-amphibians :

Soomya -
pordovician mesozoic

silurian
↳
land plants :
475 my a -




↳ i n s e c ts seeds 400
my a
+ :

devonian

↳
amphibians 360 my a -
:




↳
Reptiles
:
300
permion
mya -


③
triassic
↳ mammals
my a
:
zo o
-



①
↳ birds : 1So
mya -
jurassic
mya : Flowers Cenozoic
↳
130
Cretaceous
↳ dinosaurs died :
GS my a
S


↳ genus homo : 2 5 mya
tertiary
.




↳ anatomically modern humans : 200 K .

ya ⑥?

,Development of Theory of Evolution


·



Before 1 70 0 :




↑
species we re created unrelated+ remain unchanged

↳
earth is young (6K ·

y0)


·


1700 -

1800


↳
species are related +
change over time


↳ earth is myo




·



Erasmus Darwin (1731-1802)

4 first person to theorise that life descends from a common ancestor


↳ &K . now




Jean Baptiste Lamarck

↳ First scientific
theory
↳
change wa s a natural phenomenon I divine
,




↳ to environment
orgs · Adapted


4 use + disuse of body parts

used structures able to enlarge
·




disused structures shrink
·




- Law of Inheritance of acquired traits


what acquire life may be passed down (eg giraffe neck)
·

:
you in



has been debunked determined lifetime
n ow
Phenotype genotype ; how you look is
by genes not change over 1




·



Charles Darwin
* black peppered moth
↳ travelled around world for HMS beagle
5 yrs on



↳
Discovered


is modification with Descent

·




diversity of all species is a result of evolution over time


2) Natural Selection

·




mechanism of how evolution occurs


·




individuals best adapted to environment will leave m o re offspring with that adaptation


↳ Origin of Species (1899)

i) all organisms descended from a common ancestor


2) species spread out over time adapted to environmut


3) modifications led to diversification by branching (ancestors give rise to new species in new habitats)

4) some species died out
-

extinction




·



Alfred Russel Wallace

↳
that were separated water
suggested ancestors by

Document information

Schooljaar
200
Uploaded on
October 29, 2026
Number of pages
20
Written in
2026/2027
Type
Class notes
Professor(s)
Ieb
Contains
All classes
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