Download Evidence of evolution

EVIDENCE OF EVOLUTION

Evolution is the process of change over
time.

Biogeography is the study of where
organisms live now and where their
ancestors lived in the past.
 Patterns
in the distribution of living and fossil
species tell us how modern organisms
evolved from their ancestors.
EVIDENCE OF EVOLUTION

To Darwin, the biogeography of the Galapagos species
suggested that populations on the island had evolved from
mainland species.
 Overtime,
natural selection on the islands produced variations
among population that resulted in different, but closely
related, species.
CLOSELY RELATED BUT DIFFERENT

Darwin also noted that similar ground dwelling birds
inhabit similar grasslands in Europe, Australia, and Africa.
 Differences
in body structures provide evidence that
they evolved from different ancestors.
 Similarities
provide evidence that similar selection
pressures had caused distantly related species to
develop similar adaptations.
DISTANTLY RELATED BUT SIMILAR
 Geologists
have used radioactivity to establish the age of
fossils and rocks. Using this technology, we know that the
earth is ~ 4.5 billion years old.
 This
supports Hutton and Lyell’s notion that the earth was
very old. It also supports Darwin’s theory of evolution
because if the earth were only a few thousand years old,
natural selection wouldn’t have enough time to take
place.
EVIDENCE OF EVOLUTION

Darwin struggled with the “imperfection of
the fossil record”.

Many recently discovered fossils form series
that trace the evolution of modern species
from extinct ancestors.
EVIDENCE FOR EVOLUTION
Researchers have found more than 20
related fossils that document the evolution
of modern whales from ancestors that
walked on land.
Modern whales still retain reduced
pelvic bones and, in some cases,
upper and lower limb bones.
 Other
recent fossil finds
connect the dots between
dinosaurs and birds.
 Homologous
structures are structures that are shared by
related species and that have been inherited from a
common ancestor.
 Evolutionary
theory explains the existence of homologous
structures adapted to different purposes as the result of
descent with modification from a common ancestor.
EVIDENCE FOR EVOLUTION
HOMOLOGOUS STRUCTURES

Body parts that share a common function,
but not structure, are called analogous
structures.
ANALOGOUS STRUCTURES

Vestigial structures are inherited from
ancestors but have lost much or all of their
original function due to selection pressures
acting on the descendent.
VESTIGIAL STRUCTURES
VESTIGIAL STRUCTURES

Similar patterns of embryological
development provide further evidence that
organisms have descended from a
common ancestor.
EMBRYOLOGY
EMBRYOLOGY
 At
the molecular level, the universal genetic
code and homologous molecules provide
evidence of common descent.

All living cells use information coded in DNA
and RNA to carry information from one
generation to the next. This is identical in all
living organisms.
GENETICS AND MOLECULAR BIOLOGY
 Cytochrome
C, which functions in cellular
respiration, is a homologous protein that is found in
almost all living cells, including plants, animals, and
bacteria.
GENETICS AND MOLECULAR BIOLOGY

Hox genes help determine the “head to tail axis” in
embryonic development. Some form of these genes are
found in almost all multicellular animals.

A small change in this gene can produce a dramatic
change in the structures they control.
GENETICS AND MOLECULAR BIOLOGY
GENETICS AND MOLECULAR BIOLOGY

During his time on the Galapagos Islands, Darwin observed
several different types of finches.

Despite how different they looked from one another, Darwin
hypothesized that they all came from a common ancestor.
NATURAL SELECTION IN ACTION

Darwin noted that several finch species had beaks of
different sizes and shapes.

He proposed that natural selection had shaped the beaks
of different bird populations as they became adapted to
eat different foods. He couldn’t test this hypothesis.
NATURAL SELECTION IN ACTION

35 years later, Peter and Rosemary Grant came along with a way
to test Darwin’s hypothesis. There were two assumptions:
 For
beak size and shape to evolve, there must be enough heritable
variation in those traits to provide raw material for natural selection

Differences in beak size and shape must produce differences in fitness.
NATURAL SELECTION IN ACTION

The Grants studied a species of finch on an island big
enough to support good sized populations, but small enough
to allow the catching and tagging of every bird of the
species.

They recorded individual characteristics (beak length, beak
depth, wing length, color, etc.) and which individuals lived
and died.
NATURAL SELECTION IN ACTION

The Grants found that individual finches
with different sized beaks have better or
worse chances of surviving both season
draughts and longer dry spells.
NATURAL SELECTION IN ACTION

This work shows that variation within a species increases
the likelihood of the species’ adapting to and surviving
environmental change.
NATURAL SELECTION IN ACTION