Transcript UNIT 5 PART 1 EVIDENCE OF EVOLUTION

UNIT 5 PART 1: EVIDENCE OF
EVOLUTION
• Evolution is a gradual change over time.
• There are two kinds:
– Geological – a change in the earth over time
– Organic – a change in species over time
1
Evidence from the Past - Fossils
• A fossil is any trace or remains of an
organism that has been preserved by a
natural process.
• Scientists can compare these to living
organisms to see if evolution has occurred.
• Special circumstances are needed for fossils
to form and then usually only the hard parts
are left.
2
Relative Dating of Fossils
• Most fossils are in sedimentary rock which
forms layers.
• If the layers are undisturbed the oldest is on
the bottom and the youngest on top.
Therefore, the oldest fossils are found in the
bottom layer.
• This tells you which fossils are older.
• Determining the order of the fossils results in
the fossil record.
3
Absolute Dating of Fossils
• This will tell the actual age of the fossil.
• Radioactive Dating is the most accurate.
• Matching layers in the same region are the
same age.
This is called
correlation.
4
• These are
fossils that
appeared
around the
same time all
around the
world.
• They can be
used to match
ages of rock
layers in
different parts of
the world.
Index Fossils
5
• Earliest organisms
were simple, later
ones more complex.
• Unicellular organisms
appeared before
multicellular.
• Aquatic organisms
appeared before land
animals.
Patterns of
Evolution
6
There are sequences in the fossil record that
indicate that later species developed from
earlier ones through a series of gradual
changes passed on from generation to
generation.
These occurred over millions of years in the
species. The fossil record is considered the
strongest evidence of evolution.
7
Extinction
• Of all the species that ever lived
less than one percent exist
today.
• When the last of a species dies
that species is said to be
extinct.
• Extinction is forever.
Quagga 1883
Golden Toad 1989
Tasmanian Tiger or
Tasmanian Wolf 1936, 1986
Passenger
Pigeon
1914
8
Evidence from Living Organisms
• The classification system
that we use is based on
similarities and
differences in anatomy,
embryological
development, and
biochemistry.
• Similarities indicate a
common ancestor. The
more similarities between
organisms the more
closely related they are.
9
Anatomical Similarities
• Vestigial structures – parts that are reduced in
size and have little or no function.
– Human appendix, tail bone, wisdom teeth and muscles
that move the ears and nose
– Whale hip and leg bones
10
Homologous Structures
• Parts that have similar structures and
development (are built the same way) but
have different functions:
– Human arm
– Cat leg
– Whale flipper
– Bat wing
• Indicates a common ancestor
11
Analogous Structures
• Parts that have the same function but a
different structure and development (they
are made differently):
– Bird wing
– Insect wing
• Indicates evolution along different lines
12
Embryological Similarities
• The embryos of closely related species
show similar patterns of development.
• As development
continues the
embryo
resembles
the adult.
• The longer the
embryos
resemble each
other, the closer
related they are.
13
Molecular Similarities
• The ability to read the amino acid sequence of
proteins and the DNA of an organism letter by
letter has enabled biologists to confirm
evolutionary relationships.
• The more closely related
organisms are, the
greater the biochemical
similarities will be in the
sequences of DNA,
proteins, and enzymes.
14
The Origins of Life –
Modern Hypothesis
• Biogenesis – living things come only from
other living things.
• So where did the first living things come
from?
• The most widely accepted view is the
heterotroph hypothesis.
15
Heterotroph Hypothesis
• Early conditions on Earth were different:
– Higher temperature
– Different atmospheric composition
• The oceans were a hot, thin soup where
chemical reactions were
likely to occur.
• An experiment by Miller
showed that organic
compounds could be
formed under these
conditions.
16
Heterotroph Hypothesis cont’d.
• These organic compounds then formed structures
that had some of the characteristics of life and
began to grow and divide. They were called
heterotrophs.
• Eventually organisms developed that could use
light for energy and produce oxygen - autotrophs.
• This changed the makeup of the atmosphere
which led to the development of organisms that
could use oxygen for respiration.
• Because aerobic respiration is more efficient than
anaerobic, organisms using aerobic respiration
became dominant.
17