Transcript Evolution - Jessamine County Schools

CHAPTER 4
Evolution and Biodiversity
History of Evolution
•
The evolution of life is linked
to the physical and chemical
evolution of the earth.
•
Life on earth evolved in two
phases over the past 4.7 -4.8
billion years
1) Chemical evolution (1
billion years) of the
organic molecules and
systems of chemical
reactions needed to form
the first proto-cells.
2) Biological evolution (3.7
billion years) of singlecelled organisms and
then multicellular
organisms.
Evolution
• Evolution
– theory that concerns how organisms change over
time.
– The change in a population’s genetic makeup through
successive generations.
• Evidence of Evolution
1.
2.
3.
4.
Fossil record (most common form of evidence)
Chemical analysis
DNA analysis
Ice core drillings
Fossil Record
• This stratigraphic
column shows the order
in which organisms
appeared. Each layer
represents a particular
time frame and shows
an organism which was
found during that time.
•
The oldest fossils
appear in lower layers,
and the most recent
fossils at the top. This
allows for placement of
fossils to be used as an
aid in dating the
organism found.
How Has the Earth Changed?
• Earth is constantly changing and throughout
history has had changes in
1.
2.
3.
4.
5.
The atmosphere
Climate
Positions of continents
Geography
Types and number of organisms
Atmosphere and Climate
• Atmosphere
– Changes in the atmosphere were the result of
collisions between earth and large asteroids
(catastrophic events)
• Climate change
– Alternate periods of heating and cooling
– Advance and retreats of ice sheets over northern
hemisphere
Geologic Processes
• Tectonic plates have
drifted atop Earth’s
mantle
• Locations of
continents and ocean
basins influence
Earth’s climate
• Species move, adapt
to new environments
Patterns of Evolution
1. Divergent evolution – the process by which related
species become less alike; evolve into a variety of
species
–
Leads to speciation –the formation of a new species.
•
•
–
Also results in adaptive radiation – the process by which
members of a species adapt to a variety of habitats.
•
–
Ex. Polar bears diverged from brown bears
Camels and llamas
Ex. Darwin’s (Galapagos) finches – 13 different variations
Biodiversity is believed to be the result of speciation and
extinction.
Geographic Isolation
• The movement of tectonic plates influences evolution
by changing the locations of continents, causing some
species to be geographically isolated from others.
• Geographic isolation – when a physical barrier
separates a population into groups.
– can result from
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Mountain ranges
Volcanic eruptions – lava flows
Rivers
Earthquakes
Deforestation
Continents
Islands
Patterns of Evolution (cont.)
2. Convergent evolution – the process by which distantly related
organisms develop similar characteristics.
• occurs when different species share the same environmental
surroundings
– Ex. Whales and dolphins (mammals) now resemble fish
• Can often lead to cases of mimicry – the evolution of one organism
so it comes to resemble or look like another.
– Ex. Queen Anne’s butterfly closely resembles the toxic Monarch
butterfly.
• Over the course of time, the change of the gene pool of one species
may lead to the change of the gene pool of another species –
coevolution.
– Ex. Bats and moths
How Many?
•
Earth has an
estimated 4 – 20
million species.
•
1.8 million have
been identified.
•
Species – a group of
similar organisms
that share a
common ancestor
and do not
reproduce outside
the group.
Ways of Classifying Organisms
1. Anatomical structure
– The more closely related a species, the more similar their
structures will be.
• Homologous structures – body parts with structures that are very
similar, even though they have entirely different functions.
Ex. Bones in a whale’s flipper, a human’s arm or bat’s wing
• Vestigial structures – body parts that have degenerated and seem
to serve no function.
Ex. Tail-bone, wisdom teeth, appendix
Boas and whales – small hip and leg bones
• Analogous structures – body parts that have the same function
but are NOT similar in structure.
Ex. Wing of a bird and wing of a butterfly
Homologous Structures
Vestigial Structures
Vestigial organs associated with eye structures
Vestigial remains of a pelvic girdle in a whale
Figure 5
Figure 6
Analogous Structures
• Analogous
structures are a
contrast to
homologous
structures.
• These structures are
of no use in classifying
organisms or in
working out their
evolutionary
relationships with
each other.
Ways of Classifying Organisms (cont.)
2. Chemical analysis
- includes proteins, antibodies, enzymes
3. DNA analysis
How Did We Get So Many?
At the Molecular Level
• Biological evolution
– By natural selection – explains how life changes
over time
– Adaptation or adaptive traits enables an organism
to survive through natural selection to reproduce
under prevailing environmental conditions.
– Biological evolution is based on changes in a
population’s genetic makeup over time.
– Populations evolve due to variations within, but
individuals can’t develop new structures.
Darwin’s Theory
1. Variation exists within species.
2. All organisms compete for limited natural
resources – some get more, others get less.
3. Organisms produce more offspring than can
survive.
4. Natural selection: The environment selects
organisms with beneficial traits. Individuals with
adaptive traits have a greater chance than
others to survive and pass on their traits to their
offspring.
Processes in Which Evolution Occurs at
the Molecular Level
• Natural selection
• Genetic drift – when genotypes are lost by
chance; usually in small populations
• Artificial selection – “controlled breeding”
– Process controlled most directly by humans
– Ex. Breeding horses for speed
How Does the Genetic Makeup
Change?
• Mutation – a change in DNA
– Mutations are a source of new genetic material.
– They add genetic material to a population’s gene pool
thereby increasing variation within the population.
– Mutations are sometimes beneficial.
• Causes of mutations:
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Ultraviolet light
X-rays
Radioactivity
Certain chemicals (mutagens)
Random errors in DNA coding
What Limits Adaptation?
• A change in environment conditions can lead to
adaptation only for traits already present in the gene
pool of a population.
• Because each organism must do many things, its
adaptations are usually compromises
• Even if a beneficial heritable trait is present in a
population, that population’s ability to adapt can be
limited by its reproductive capacity.
• Even if a favorable genetic trait is present in a
population, most of its members would have to die so
that individuals with the trait could predominate and
pass the trait on.
Microevolution
•
Microevolution works through a combination of four processes
that change the genetic composition of a population:
1.
2.
3.
4.
Mutation – involving random changes in the structure or number of
DNA molecules in a cell and is the ultimate source of genetic
variability in a population.
Natural selection – occurs when some individuals of a population
have genetically based traits that cause them to survive and
produce more offspring than other individuals
Gene flow – involves movement of genes between populations and
can lead to changes in the genetic composition of local populations.
Genetic drift – involves changes in the genetic composition of a
population by chance and is especially important for small
populations.
Macroevolution
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Macroevolution is concerned
with how evolution takes place
above the level of species and
over much longer periods than
microevolution, and macro
evolutionary patterns include
genetic persistence, genetic
divergence, and genetic loss.
Bottleneck effect – When a
population suddenly reduces in
size either from habitat loss,
natural disaster or other
changes in the environment and
its genetic variation is affected.
Speciation – under certain
circumstances natural selection
can lead to an entirely new
species.
Extinction – when all of one
species is no longer existent.
Adaptation and the Ecological Niche
Ecological niche is the species’ way of life
or functional role in an ecosystem. A
specie’s niche involves everything that
affects its survival and reproduction. This
includes..
1. The range of tolerance for various
physical and chemical conditions
2. The types of resources it uses, such as
food or nutrient requirements
3. How it interacts with other living and
nonliving components of the
ecosystems in which it is found
4. The role it plays in the flow of energy
and cycling of matter in an ecosystem.
How Does the Ecological Niche Relate to
Adaptation?
• Evolution by natural selection
leads to a remarkable fit between
organisms and their environment.
• In terms of the ecological niche of
a particular species, this fit
involves having a set of traits that
enables individuals to survive and
reproduce in a particular
environment.
• Species that have similar niches
tend to evolve similar sets of
traits, even if they are unrelated
species growing in different parts
of the world.
• Generalists and specialists
Genetic Engineering
• Manipulation of DNA
– Involves
• Gene-splicing
• Recombinant DNA
Thing of miracles or Pandora’s box?