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The History of Life on Earth
The History of Life on Earth
The history of life is divided up into eons, eras, periods, and epochs:
Formation of
the earth
4600 mya
Oldest known microfossils
found in 3500 million year old
chert in Western Australia
Oxygen produced by
plants accumulates in
the atmosphere
Precambrian Eon
Millions of years ago
Quaternary
Eras
Millions of years ago
Evolutionary History 1
Bacteria and algae
Based on fossil evidence and
Protists
Fungi
evolutionary history of
plants, fungi, bacteria,
Land plants
radio-isotope dating, the
protists, and non-chordate
to the Precambrian.
Some invertebrate groups extend
Cycads
Angiosperms
Flatworms
Molluscks
Invertebrates
evolutionary history extending back
Conifers
Cnidarians
animals can be compiled.
Bacteria, protists, and fungi have an
Sphenophytes (ferns etc)
Annelid worms
Insecta
Crustacea
Diplopoda
Arachnids
Echinoderms
back to the Cambrian Period, but
land plants only as far back as the
Devonian Period.
Millions of years ago
Evolutionary History 2
Tunicates
Agnatha (jawless fishes)
Similarly, the evolutionary
history of chordates can
be traced back to the
Cambrian, but most
Sharks and rays
Ray finned fishes
Fish
Lungfish
Amphibians
Amphibians
Chelonia (turtles a& tortoises)
animal groups are much
Reptiles
Crocodilia
Rhyncocephalia (tuatara)
more recent than this.
Squamata (lizards & snakes)
Birds
Birds
Monotremes
Mammals
Marsupials
Placentals
Millions of years ago
Precambrian Life
4600 mya: Origin of Earth.
Cnidarians
Bacteria
4600–3800 mya: Chemical
and molecular evolution
leading to origin of life:
protocells to anaerobic
bacteria.
3800–2500 mya: Origin of
photosynthetic bacteria.
Protozoans
Algae
2500–570 mya: Origin of
protists, fungi, algae, and
animals.
Early Paleozoic Life
550-500 mya: Origin of animals
with hard parts, which appear as
Anomalocaris
fossils in sedimentary rocks.
Aysheaia
Simple marine communities
become established.
The Burgess Shale deposits in
Hallucigenia
Canada contain a rich collection
Ottoia
of early Cambrian fossils.
The fauna (pictured) was
strange and, at first, wrongly
interpreted.
Wiwaxia
Pikaia
Late Paleozoic Life
Early
vascular
plants
500-435 mya: Major adaptive
radiations of marine
invertebrates and early fishes.
Early
insects
435-280 mya: Vast swamps
Dimetrodon
with the first vascular plants.
Origin and adaptive radiation of
reptiles, insects, and spore
bearing plants (including
Armored fish
gymnosperms).
Ammonite
240 mya: Mass extinction of
nearly all species on land and in
Trilobite
the sea (the Permian
extinction).
Early amphibians
Mesozoic Life
240-205 mya:
Recovery of surviving taxa and
adaptive radiation of marine
invertebrates, dinosaurs, and
fishes. Origin of mammals.
Gymnosperms become
dominant land plants.
181-135 mya:
Major radiations of dinosaurs.
135-65 mya:
Major radiations of dinosaurs,
fishes, and insects. Origin of
angiosperms.
65 mya:
Asteroid impact linked to the mass
extinction of many marine
species and all dinosaurs
(Cretaceous extinction).
Apatosaurus
Velociraptor
Styracosaurus
Icthyosaurus
Early mammals
Early
gymnosperms
Cenozoic Life
65-1.65 mya: Major shifts
in climate. Major adaptive
radiations of angiosperms
(flowering plants),
insects, birds and
mammals.
Indricotherium
3-5 mya: Early humans
arise from ape ancestors.
Glyptodon
Platybelodon
1.65 mya: Modern
humans evolve and their
hunting and other
activities accelerate.
Diatryma
Dryopithecus
Sabretooth Tiger
Mass Extinctions
• Present day — the Holocene extinction event
– predict that humanity's destruction of the biosphere could cause the
extinction of one-half of all species in the next 100 years.
• 65 MY ago — at the Cretaceous-Paleocene transition
•
about 50% of all genera became extinct (75% species). Largest
extinction
• 200 MY ago — at the Triassic-Jurassic transition
• about 20% of all marine families & the last of the large amphibians
were eliminated
• 251 MY ago — at the Permian-Triassic transition
• killed 53% of marine families
• 444 MY ago — at the Ordovician-Silurian transition
• second largest of the five major extinctions in Earth's history in terms
of percentage of genera that went extinct.
What is Evolution?
Microevolution describes the
small-scale changes within
gene pools over generations.
Macroevolution is the term
used to describe large scale
changes in form, as viewed in
the fossil record, involving
whole groups of species and
genera.
Kingdom
Phylum
Class
Order
Family
Genus
Species
Macroevolution includes:
Adaptive radiation of groups of species from a common
ancestor into different environments and different
niches. Eg. Birds – beaks, feet, diets, etc
The origin of evolutionary novelties such as the wings and
feathers of birds, and the upright posture of humans.
The evolutionary history of a species or taxonomic group is
called its phylogeny. Classification of species aims to
accurately reflect their phylogeny.
Evolution refers to the permanent genetic
change (change in gene frequencies) in
population of individuals. It does not refer to
changes occurring to individuals within their
own lifetimes. Populations evolve, not
individuals.
Microevolution describes the small-scale
changes within gene pools over generations.
Macroevolution is the term used to describe
large scale changes in form, as viewed in the
fossil record, involving whole groups of species
and genera.
Evidence For Evolution - Fossil
 Fossils are preserved
remains, impressions
or traces of organisms
found in rocks.
 They provide direct
evidence of past life on
Earth
Types of Fossils
Fossil fish
The term fossil refers to any parts or
impressions of an organism that may
survive after its death.
Fossils form best when organisms are buried
quickly in conditions that slow the process
of decay.
Fossils are most commonly found in
sedimentary rock.
Trilobites
preserved in
sedimentary
rock
Mineral-rich hard parts (bones, teeth, shells) may
remain as fossils, or minerals dissolved in
water, may seep into tissues and replace
the organic matter of the organism.
On rare occasions, fossils retain organic material,
as when plant material is compressed
between layers of shale or sandstone.
Bird bones
preserved in a tar
pit
A layer of shell
still covers the
stone interior
of this
ammonite
Evidence of evolution through
fossils
• Fossil is the preserved evidence of life
from the past.
• Direct evidence or Indirect evidence
• Direct Evidence
• Fossilised bones (which are actually
rock), mould and cast.
Cast
Evidence of evolution through
fossils
• Indirect Evidence
• Anything from life from the past, but not
direct. Eg paintings, footprints,
droppings, tools.
How Fossils Form
• Fossils form in sedimentary rock (rock
made from sand or silt or mud).
• These form layers at the bottom of a lake
or ocean or river. These layers get
compressed and as this happens the
sediments get hot, the sand then fuses to
form new rock.
• It’s in those sedimentary rocks that fossil
form. Almost always under water.
Fossilised Bones
Fossils Forming
• For a fossil to happen, there are three main
conditions necessary.
• 1. Once the specimen dies, it needs to be
covered very quickly by sediment (usually under
water).
• 2. The decay of that organism needs to be
prohibited by the exclusion of oxygen by the
sediments. Best when conditions are dry, cold or
acidic. When sediments are packed around that
organism, it stops bacteria from getting to it.
• 3. Must be left undisturbed for millions of years.
What Fossil Records Show Us
• 1. Species disappear over time. Eg
dinosaurs.
• 2. That some species weren’t around, but
now are. Eg. humans, previous to 2.5 million
years ago there have been no fossilised
evidence of humans.
• 3. Trend towards complexity as we go from
older rocks to younger rocks. Eg. Bacteriaeukaryotes, Fern-flowering plants, reptilesbirds.
What Fossil Records Show Us
• 4. Fossils, which are those that are half
way between reptiles and birds. Most
classic example is a reptile/bird called
archaeopteryx.
Reptile/Bird Archaeopteryx
Problems With Fossils
• Fossil records are not quite complete.
Some species are not well represented
and most fossils are incomplete.
• COMMON EXAM QUESTION!
• Most animals that die do not get fossilised,
they just decay.
• Forming fossils is very rare.
• Lots of environments aren’t conducive to
making fossils. Eg Mountain Goats
Problems With Fossils
• Fossils get destroyed easy, by movement
of sediment.
• Some species have behaviours that aren’t
conducive to forming fossils. Eg apes
• Soft bodies. Eg worms
• On the planet for a short period of time.
• Evolved and then become extinct.
• Not very wide spread. Eg cheetahs
Fossils
 Fossilisation of organisms occurs when
they are entombed in sediments, hardened
into rocks, or sometimes trapped in amber.
 Types of Fossils include:



Mineralisation
Imprint or mould
Encased in amber or ice
Fossil Record
 The fossil record is not a complete record of
all past life because the chances of fossils
forming is small. Often only hard parts of
organisms are preserved and only under
certain environmental conditions.
 The fossil record is biased in favour of
organisms that live in shallow-water
sediments.
How old?
Fossils in a Rock Profile
Layers of sedimentary rock are
arranged in the order in which they
Most recent
sediments
were deposited, with the most recent
Recent fossils are
found in recent
sediments
Numerous
extinct species
layers nearer the surface.
Fossil types
differ in each
sedimentary
rock layer
Sedimentary layers can be
disturbed by subsequent tectonic
activity.
The interpretation of rock layers
New fossil types
mark changes in
environment
containing fossils allows us to arrange
the fossils in chronological order
(order of occurrence), but does not
give their absolute date.
Oldest
sediments
Only primitive
fossils are found in
older sediments
The Fossil Record
The fossil record is a substantial, but incomplete, record of
evolutionary history:
Modern species can be traced through fossil
relatives to distant origins.
Fossil species are often similar to, but usually differ
from, today's species.
Fossil types often differ between
sedimentary rock layers.
Numerous extinct species are found as fossils.
Fossils can be dated to establish their approximate
absolute age.
New fossil types mark changes in the past
environmental conditions on the Earth.
Rates of evolution can vary, with bursts of species
formation followed by stable periods.
These fossil teeth, from Mastodon,
an extinct elephant, are similar to the
deciduous teeth of modern
elephants.
Dating methods
 Stratigraphy –relative age of stratum
Dating the fossil record
Various dating techniques are
available to estimate the
relative and absolute age
of the rock and the fossils.
Most recent
sediments
Recent fossils are
found in recent
sediments
Numerous
extinct species
1. Stratigraphy – comparison
of rock strata, older layers
are laid down first so
relative ages can be
established. Similar fossils
in similar rocks will be the
same age.
Fossil types
differ in each
sedimentary
rock layer
New fossil types
mark changes in
environment
Oldest
sediments
Only primitive fossils
are found in older
sediments
2. Indicator fossils – these are usually widespread, common at
a particular time and can be used to date the rock strata of an
new fossil discovery.
Graptolites are
indicator fossils
of the Ordovician
period.
3. Absolute dating - is used to determine with accuracy the
actual age of the rock or fossil. These techniques measure the
decay rate (half-life) of radioactive isotopes. The half-life of
an isotope is the time taken for half of the atoms in the
radioactive sample to decay (undergo chemical change).
Radiocarbon dating measures the ration of C14 to C12. It is limited
to dating fossils less than 50000 years old. (Half life is 5730
years)
Potassium-argon dating K40:Ar40 will date to 4600 million years
(Half life is 1250 million years)
Uranium –lead dating U238:Pb207 will date to 4600 million years
(Half life is 4.47 billion years)
And there are many more
methods as well – tree rings,
varve, paleomagnetism, etc.
Macroevolution includes:
Adaptive radiation of groups
of species into different
environments and different
niches.
The origin of evolutionary
novelties such as the wings
and feathers of birds, and the
upright posture of humans.
The evolutionary history of
a species or taxonomic group
is called its phylogeny.
Evolutionary theory is now supported by a
wealth of observations and experiments. Although biologists do not
always agree on the mechanisms by which populations evolve, the
fact that evolution has taken place is well documented.
Evidence for evolution comes from many sources:
Paleontology
Paleontology: The identification,
interpretation and dating of fossils
gives us some of the most direct
evidence of evolution.
Embryology and evolutionary developmental
biology: The study of embryonic development
in different organisms and its genetic control.
Comparative anatomy:
The study of the morphology of different species.
Comparative anatomy
Biogeography: The study of geographic
distributions can indicate where species may
have originally arisen.
Artificial selection: Selective breeding of
plants and animals has shown that the
phenotypic characteristics of species can
change over generations as particular traits
are selected in offspring.
Biochemistry: Similarities and differences in
the biochemical make-up of organisms can
closely parallel similarities and differences in
appearance.
Molecular genetics: Sequencing of DNA and
proteins indicates the degree
of relatedness between organisms.
From gray wolf to
Yorkshire terrier:
selective breeding can
result in phenotypic
change
Embryonic Development
• By examining the
embryonic development of
a species and comparing
them with other species
you can see remarkable
similarity. This gives rise
to another example of
evidence for evolution
Vestigial Structures
• In evolution some animals that have evolved
from a common ancestor will share similar
organs but in one, the function of that organ
may become not needed.
• Humans have muscles in their ears that are the
same that a dog uses to wiggles an ear. We no
longer need it, it becomes obsolete
Vestigial Structures
• A structure found in a species, which is not
being used as it is in other species.
• A structure that is left over from the past,
which was once useful, but no longer is.
Vestigial Structures
• Eg pelvis of whales.
• The use of a pelvis is to support our spine
on top of our legs so we can walk.
Vestigial Structures
Biogeography
• This is the study of the
distribution of
organisms. Distribution
patterns give clues to
the evolutionary
history of organism
and of the Earth itself.
Biogeographical Evidence for
Evolution
•
•
•
•
Biogeography is the study
of the distribution of
animals and plants
across the earth.
Progression
• 250 million years ago, all the continents of
the earth were joined in one land mass called
Pangaea.
• 11 o’clock pm, Pangaea broke up to form
Gondwana in the south and Laurasia in the
north.
• At about 11.12pm, Africa separated from the
rest of Gondwana and then the rest of
Gondwana continued to break up until
11.39pm.
Examples of the Effects
• Large, flightless birds (Ratites), only seen
in the south.
• Waratahs only seen in Western Australia,
closely related to the Proteas of South
Africa.
• Mistletoe only native in the north (northern
America and across Europe.
• Wattles only seen in Australia and Africa.
DNA evidence
Chimpanzee
• The similarity of genetic
linkage groups between species
provides evidence that the
species have common ancestry.
• Molecular hybridization is
when a single strand of DNA is
brought together with a
complementary strand. IF done
with two different species the
level of compatibility shows
the closeness of the relationship
Percentage
differences – 2.4
GIBBON
percentage
difference
from
human5.3
Green
Monkey
percentage
difference is
9.5
DNA-DNA hybridisation
• Can be used to compare the DNA sequences of 2
species.
• Denature DNA from 2 species then hybridise them
together.
• They will join where they have similar sequences
and where they are different they won’t join up.
• Level of similarity is measure by reheating the
hybrid molecule.
• The more similarities the more you need to heat it.
• A drop in 2 degrees Celsius from the control
indicates a 2% difference in DNA, a 3 degree a
3% etc.
Human and Primate DNA-DNA
Comparison
• Chimpanzee: 2.4%
difference
• Gibbon: 5.3%
difference
• Green monkey: 9.5%
difference
• Capuchin monkey:
15.8% difference
Sources of DNA
•
•
•
•
Nuclear DNA
Mitochondrial DNA
Chloroplast DNA
Ribosomal RNA
Phylogenetic tree
• A phylogenetic tree is a
diagram which is based
on homologous
features and shows
how organisms are
related and diverged in
evolution
Phylogeny and Taxonomy
Similarity of form due to a shared ancestry is called homology.
EXAMPLE: Classification and phylogeny of Order Carnivora.
Dog
Genus
Family
Wolf
Coyote
Canis
Fox
Vuples
Cat
Puma
Felis
Canidae
Tiger
Panthera
Cheetah
Acinonyx
Felidae
(The dog family)
Order
Lion
(The cat family)
Carnivora
NOTE: This is a simplified diagram: there are additional families, genera, and species not represented
here.
Evidence for Evolution –
Comparative anatomy
 Features of organisms that
have a fundamental
similarity of structure are
called homologous
features.
 They are evidence for
evolutionary relationships.
Humans, Birds, bat and
Seal have very similar
forearm structures
therefore they have a
common evolutionary
ancestor.
Anatomical Evidence of
Evolution
 Two main kinds of evidence of evolution
from anatomy: homologous structures and
analogous structures.
 But there is also vestigial structures.
Homologous Structures
 When species share a common ancestor, so have
similar structures, even though they may be used for
completely different things.
 Example: pentadactyl limb of vertebrates.
 In our arm we have one upper arm bone, then two
lower arm bones, then we have our wrist bones or
carpals, then five fingers (phalanges).
 When you look at other mammals, you find this same
basic design, even though some may use them for
different means.
Homologous Structures
 A dog has the same basic design, but they
use them for walking on.
 A bat uses their fingers to hold out a
membrane that they use to fly with.
 Whales have the same basic structure in their
flippers to swim.
Pentadactyl Limb
Homologous Structures
 Different functions but same basic structure.
 All evolved from the same common ancestor.
 Kind of evolution that leads to homology is
called divergent evolution (process where
by organisms with a recent common ancestor
develop different adaptations in different
habitats).
Homologous
features
 Homologous Features are
evidence of divergent evolution –
splitting off a common ancestral
species into two new different
species.
 Finches of Galapagos Islands are
examples of the outcome of
divergent evolution. Natural
Selection has resulted in different
beak characteristics between
species as each one became
adapted to a particular food.
Analogous Features
 Analogous features in different organisms
have the same function but have evolved
independently. They are evidence of
convergent and parallel evolution
Analogous Structures
 Features of different species, which have the
same basic function, but completely different
structure.
 Have not been derived from a common
ancestor.
 Have evolved in response to a similar
environment.
Analogous Structures
 Eg sharks dorsal fin and dolphins dorsal fin.
They are not closely related, but both have
dorsal fin.
Analogous Structures
 Eg the wings of a pterosaurs, bat and bird