Transcript 25.2 Evidences for evolution

25 Evolution (Extension)
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25.1 What is evolution?
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25.2 Evidences for evolution – fossil records
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25.3 Natural selection
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Mind Map
25.1 What is evolution?
25.1 What is evolution?
Plantae
Animalia
Fungi
Prokaryota
Protoctista
25.1 What is evolution?
Evolution
is the gradual
development of
living things
Plantae
Fungi
Prokaryota
from simple to
Animalia
complex
life forms as
time passes
Protoctista
25.2 Evidences for evolution – fossil records
25.2 Evidences for evolution – fossil records
Formation of fossil
Volcanic eruption caused the death
of dinosaurs
25.2 Evidences for evolution – fossil records
Formation of fossil
The skeleton was then covered by
sand or mud
25.2 Evidences for evolution – fossil records
Formation of fossil
As time went by, the mud and sand
turned into sedimentary rock
25.2 Evidences for evolution – fossil records
Formation of fossil
A paleontologist discovered the
fossil and dug it out
25.2 Evidences for evolution – fossil records
What can fossils show?
Fossils can provide information about
organisms which lived millions of years ago
Geological time scale
Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec
25.2 Evidences for evolution – fossil records
Examining
fossil
record
60 million
years ago
25 million
years ago
Now
Forelimb
of horses
Body size
Horses became bigger & their legs became longer
25.2 Evidences for evolution – fossil records
Fossil of Archaeopterynx
Characteristics
of reptiles
full set of teeth
long tail
Characteristics
of birds
wings and
feathers
It shows that
reptiles and
birds may have
evolved from a
common
ancestor
25.3 Natural selection
25.3 Natural selection
My book
‘The Origin of Species ’
proposed the theory of
natural selection
to explain evolution
Charles Darwin
(1809-1882)
25.3 Natural selection
1. Variation occurs
between individuals of the
same species.
Light moth
Dark moth
For example, two types of moths
exist, light and dark
The Origin
of Species
Charles Darwin
25.3 Natural selection
2. More individuals are born in
each generation.
However, there is a
struggle for existence.
Only the individuals that are
more adapted than the others
to the environment can survive.
This idea is known as survival
of the fittest.
The Origin
of Species
Charles Darwin
25.3 Natural selection
3. Individuals that survive can
reproduce and pass their
characteristics to the next
generation before they die.
4. After a very long period
of time, a group of
individuals that once
belonged to the same
species may separate into
different kinds of species –
evolution has taken
place.
The Origin
of Species
Charles Darwin
25.3 Natural selection
Examples of natural selection
1. Peppered moths in Britain
Light moth
In the 1840s
Dark moth
The tree trunks were covered by light-coloured lichens & mosses
The moths were well camouflaged from predators
Thus light moths are more adapted to the environment
Struggle for existence
25.3 Natural selection
Examples of natural selection
1. Peppered moths in Britain
Light moth
In the 1840s
Dark moth
Thus most moths are light in colour
Survival of the fittest
25.3 Natural selection
Examples of natural selection
1. Peppered moths in Britain
Light moth
In the early
nineteenth century
Dark moth
The pollutants killed the lichens and mosses on the tree trunks
The dark moths were more adapted to their
surroundings & can pass on their genes
Soon there were more dark moths than light ones
25.3 Natural selection
polluted habitat
dark
form
light
form
unpolluted habitat
light
form
dark
form
25.3 Natural selection
Examples of natural selection
2. Darwin’s finches
feeds on seeds
The seed-eating finches had reached the
Galapagos Island from the mainland Africa
but there was not enough food for all the birds
25.3 Natural selection
Examples of natural selection
2. Darwin’s finches
feeds on seeds
Finches with slightly different beaks
were able to eat other types of food
These finches survived to breed and passed on
their adaptive characteristics to their offspring
25.3 Natural selection
Examples of natural selection
2. Darwin’s finches
feeds on seeds
feeds on
leaves
feeds on seeds
feeds on insects
feeds on buds
and fruit
feeds on grubs
tool using finch
Birds with different beaks live on the island now
25.3 Natural selection
Significance of variation on evolution
Provides chances to make an organism
better adapted to their environment & help
it win in the struggle for existence
Thus, the advantageous variation can be
passed on and a new improved kind of
organism arises
Mind Map
Evolution
gradual
development of
living things
from
one evidence
fossil records
one of the
evolutionary theory
natural selection
proposed
by
examples
simple
to
complex life
forms
Charles Darwin
1. peppered
moths
2. Darwin’s
finches