Thorough run through of every component of evolution. SAGS based and unpacks each topic needed to be learned. There are many diagrams, tables, linked videos and explanations which will make learning this topic super easy. Everything that is needed to be learned are in these notes.
➔ Scientific theory of evolution emerges from different lines of evidence
➔ Types of evidence: fossil record, modification by descent, evidence from biography,
genetics (such as DNA/ mtDNA)+ other forms of evidence
➔ Role of Erasmus Darwin, Lamarck, Charles Darwin and Alfred Wallace in the
development of theory of evolution
What is evolution:
(Understanding)
● Evolution: The gradual change or development of something
● Can be used in various senses (economic structures and general use)
● Evolution is fastest in bacteria
● They grow and evolve quickly and are therefore a good example to use when testing
theories of evolution
● Or just doing testing of chemicals/DNA type of genetic stuff.
What is biological evolution:
(SAGS)
● Biological evolution: The change in the gene pool of a population during the
course of time by such a process as mutation, natural selection and genetic drift.
● Descent with modification (meaning an organism only evolves if the future
generations/offspring are modified)
● Helps us understand history of life
,Lines of evidence for evolution:
(SAGS)
1. Fossil records
2. Modification by descent
3. Biogeography
4. Genetics
5. Embryology
6. Vestigial organs
7. Biodiversity
8. Physiology
1. The Fossil Record:
● Fossil: The remains or traces of a living organism that has escaped decay and
has been preserved in sedimentary rock
● Palaeontology= study of prehistoric life through fossils
● Rock record: 3.5 billion years old
● Radiometric dating can work out age of rocks
● Fossil records are controversial to some religions as it interferes with their time record
● How do fossils get made?
1. The organism (animal or plant) needs to die
2. Burial needs to be quick- the organism needs to be covered up quickly. Covered up in
either volcanic ash, tar pits, dassie poop or flood sediments. This will preserve the state of
the organism's shape and form a mold/cast around it
3. There needs to be no oxygen preferably as oxygen decays materials quickly. AKA
ANAEROBIC conditions (meaning without oxygen)
4. Then we require lots of years to go by and SEDIMENTARY ROCK layers to form (this
refers to relative dating as well). This type of rock is formed by layers and layers of alluvium
or silt
5. These layers harden. (the rock layers don’t tell us the day, it only gives us an estimate
relative to other organisms found in different layers) e.g. organisms found in the top layers
of sedimentary rock is younger/newer than organisms found in the bottom layers*
6. The trapped parts of the organism eventually fully decompose and decay away
7. If the organism is not decayed away/dissolved away, minerals fill up the spaces and this
type of fossil is called MINERALIZATION/PETRIFICATION
*unless there was geological trauma/ natural disasters such as a volcanic eruption or flooding,
we can assume these layers are aligned the right way.
,How does fossil evidence show evolution has occurred:
● Provides information and evidence of d escent with modification (the insect in the top
layers don't look the same as the insects at the bottom layers)
● Different rock layers with oldest fossils in oldest layers
What can be seen in the fossil record? (CDETS)
A. Increase in complexity; simplest organism appeared first
B. Increased diversity
C. More extinct species
D. Existence of intermediate forms between groups (transitional fossils)
E. Increase in size
a) Increase in complexity:
- If fossils arranged in order of age, succession of change is seen
- Changes accumulated over generations
- Earliest organisms found in the oldest rocks
- More complex organisms (youngest) found in newer rocks
Organisms in order of age (oldest to
youngest)
Earth began…
Prokaryotes (bacteria)
eukaryotes
invertebrates
fish
Land plants
amphibians
reptiles
mammals
humans
, Cambrian Explosion:
● 545 MYA
● Rapid diversification over relatively short period of 5-10 million years.
● led to appearance of huge diversersity of complex, multi-celled organisms
● Before this, organisms simple: composed of individual cells
● This period is the time when most modern marine groups of animals first appeared
in the fossil record
● The Cambrian explosion is the name of the event that took place 540-490 mya.
● This random event gave birth to many new species that cannot be found before this
time.
● The species differ massively to organisms that existed pre-Cambrian times
b) increase in biodiversity:
● New organisms descended from common ancestors
● Ancestors adapted to variety of environments
● After accumulating adaptations ancestors formed by branching a variety of modified
descendants
● Type of descent known as cladogenesis
● Pattern repeated itself: biodiversity increased
● Cladogram = family tree that shows evolutionary relationships
● cladogram / phylogenetic tree
➔ Gorilla most distant relative from concestor
➔ Baboons closest relative from concestor
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