Download Darwin`s Theory of Evolution

Darwin’s Theory of
Evolution
Concept 14.1 pp. 292-298
Pre-Darwin Ideas• That species are fixed, permanentunchanging.
• The Earth was less than 10,000 yrs. old
and relatively unchanging.
• These ideas were challenged as people
became aware of diversity of plants,
animals and the geological processes of
Earth.
• Evolution- the biological history of life on
Earth. All of the changes that have
transformed life over an immense time.
• Fossil Study– Suggests Earth is much older.
– Specific fossils and certain living animals
were similar but not identical. SuggestingA common ancestor
– Lamark proposes life evolves or changes.
– Evolution as a process of adaptation.
• Inheritance of Aquired CharacteristicsLamark incorrectly thought that by
using or not using certain body parts the
organism developed characteristics that
could be passed on to the offspring.
For this to occur DNA or genes would
have to be modified.
• Adaptation- an inherited characteristic
that improves an organism’s ability to
survive and reproduce in a particular
environment.
• Examples of adaptations.
Darwin’s Voyage
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1831- HMS Beagle
Darwin made observations in South America.
Darwin questions his views.
He notices the plants and animals of South
America were distinct from species of Europe.
• Species living in South America were descended
from ancestral species on that continent.
Galapagos Islands.
• Chain of volcanic islands off the western coast of
South America.-Equador
• Darwin notices - species are similar but different
from the plants and animals of the nearby mainland.
Each island had different species from each other.
• Darwin infers - species changed and adapted to their
new environments on the islands after they colonized
the islands.
• Charles Lyell’s - gradual and observable geological
processes that explain physical features of Earth
today.
– Examples include erosion and earthquakes .
• Conclusion- Earth is much older than previously
thought.
Influences on Darwin
• Malthus essay- Human suffering
– human population’s growth rate is faster than
the rate at which food and other resources
can be supplied.
• Darwin realized this concept applies to all
species.
• Alfred Wallace- describes the same idea of
evolutionary change.
The Origin of Species
• Darwin publishes his book in 1859.
• 2 main points– Descent with Modification- Accounts for
diversity of life
• Species on organisms on Earth today
descended from ancestral species.
• This spread into various habitats occurred over
millions of years.
• In their habitats they accumulated different
modifications or adaptations.
• Example: fur color in rabbits.
– Natural Selection• A process, individuals with inherited
characteristics that are well-suited to the
environment leave more offspring than other
individuals.
• Over time this process can cause a change in
the characteristics of a population.
• Natural Selection as a cause of evolution
• Adaptation is the result of evolution.
• Figure 14-9- Example of snails.
• Different from selective breeding by farmersoccurs over a shorter time and the farmers do
the selection not the environment.
Evidence for Evolution
Concept 14.2 pp. 299-304
Fossil Record
• Fossils are preserved remains -past.
• Most fossils -sedimentary rocks; rivers,
lakes,swamps, sea .
• Fossil record-chronological collection.
• Each rock layer-a particular time period.
• Older fossils- bottom.
• Prokaryotes-oldest form of life; in rocks
~3.5 billion yrs. old
Terms
• extinct species- species that no longer
exists.
• Paleontologist- scientist that studies
fossils.
• Fossils of ancestral life link the past and
the present.
Geographical Distribution
• Patterns explain evolution.
• Geographic distribution of organismshow species possibly evolved.
• Explains why related species are found
today in a particular geographical area.
• Examples- Australia has many pouched
mammals (marsupials) and few
placental animals.
• Hypothesis_______________________
________________________________
____.
Homologous structures• Definition- similar structures in species
that share common ancestor.
• Example- forelimbs of mammals have
the same skeletal parts even though
the function of these limbs is completely
different.
– Human arm, cat foreleg, whale flipper, bat
wing.
– These structures have become adapted.
Vestigial Structures• Definition- remnant of a homologous
structure that no longer has a function in
modern related species.
• Often vestigial structures -reduced size.
• Example- whale vestigial hipbones.
– Hypothesis- whales descended from land
dwelling organisms with 4 limbs.
• Natural selection favors survival of
individuals with genes for reduced
versions of these structures.
Comparison of Embryonic
Development
• Closely related organisms have similar
stages of development.
• All vertebrates evolved from a common
ancestor.
– Example- pouches on side of throat.
• Fish
gills
• Birds and primates
bones of
skull.
Molecular Biology• DNA sequences
• Common genetic code shared by all species.
• Unrelated individuals-more differences in
DNA sequence.
• If 2 species have genes and protein
sequences that match closely- recent
common ancestor .
• If 2 species have more differences in DNA
and protein sequences- no close common
ancestor.
• Figure 14-16- Humans, chimps, and gorillas
based on Hemoglobin amino acid sequences
are closely related.
Natural Selection
Concept 14.3 pp 305-309
• A population- a group of individuals of
the same species living in the same
area at the same time.
• Finches on Galapagos Islands– Individual finches of each island make up a
separate population. Over time, due to
isolation they become isolated and
eventually become separate species.
– 13 species of finches• key characteristic- beak- food sources.
Variation• Definition- differences among members of the
same species.
• This variation is inherited and passes to
offspring.
• Siblings share more traits with each other and
their parents than they do with unrelated
individuals
• Individuals with inherited traits best suited to
their environment survive and reproduce
better than less fit individuals.
• Figure 14-19.
• Artificial Selection– Selective breeding by humans ( plants and
animals) to produce offspring with
desirable genetic traits. Examples– Great change in short time.
• Natural Selection- comparison- the
environment does the selecting
• Natural Selection- pesticides
– Figure 14-21
– The pesticide does not create resistance; it
selects for resistant insects already
present.
Pesticide Resistance
•
By spraying crops with poisons to kill insect pests, humans have favored the reproduction of
insects with inherited resistance to the poisons over those with no resistance.
Gene Pools
Concept 14.4 pp. 310-316
Gene Pool
• Definition- consists of all the alleles in all the
individuals that make up a population.
• A population is the smallest level at which
evolution can occur.
• The gene pool is the reservoir of genes and
supplies genetic variation.
• Sexual recombination- meiosis and
fertilization contributes to variety.
• Mutations & sexual recombination -random
Changes in Gene Pools
• Frequency of alleles- how often
certain alleles occur in the gene pool.
• Microevolution- generation to
generation change in the allele
frequency.
– Genetic drift and natural selection can
change a gene pool.
Genetic Drift
• Definition-a change in the gene pool
due to chance. Figure 14-25.
– The smaller the population the greater the
impact of genetic drift.
– Larger populations are more stable.
• Reducing the size of a population
reduces the size of its gene pool and
reduces genetic variation in a
population.
– May affect a population’s ability to adapt.
– Bottleneck Effect-disasters –cheetah pop.
– Founder Effect- new colonies
Gene Flow
• The exchange of genes with another
population.
• Migration of fertile individuals between
populations.
• Gene flow reduces genetic differences
between populations and could result in a
single population.
• Mutations- have a key role as the
original source of genetic variation for
natural selection.
– Especially important in asexually
reproducing organisms- bacteria.
• Biological Fitness- Contribution to the
gene pool of the next generation.
• Production of healthy, fertile offspring is
what counts in natural selection.
Darwin’s Finches
• Peter and Rosemary Grant’s Research
• 30 yr. Study in the Galapagos.
• 2 species of finches with different beak
sizes.
• Their data related beak size to changes
in environment- wet and dry seasons
and types of seeds available.
• Data provided evidence for natural
selection occuring in a shorter time
span.
• Figure 14-31.
Evolutionary Biology 14.5
• Natural Selection and sickle cell disease.
– Heterozygous- immunity to malaria.
– 30% of the population is heterozygous in
endemic malaria areas.
• Antibiotic Resistance- evolution in action
– Natural selection.
Origins of Biological
Diversity
Chapter 15: pp 322-351
Concept 15.1
The origin of new species.
• Essential question:
– How do biologists identify species?
– How do species arise?
• Objectives:
– Explain biological species concept.
– Compare microevolution and
macroevolution.
– Describe types of reproductive barriers.
– Analyze how adaptive radiation contributes
to species diversity.
What is a species?
• A distinct form of life.
• Biologists use the biological species
concept to define a species as a
population whose members breed with
one another to produce fertile
offspring.
• Members of one species do not breed
with members of another species.
• This definition- for sexually reproducing
organisms.
How does macroevolution differ from
microevolution?
• Microevolution is evolution on the smallest
scale; generation to generation change in the
allele frequencies in a population.
• Macroevolution is dramatic changes that are
seen in the fossil record. To explain how we
evolved from simpler life forms. Includes:
– Origin of different species- speciation.
– Extinction of species.
– Evolution of major features
• Key concept- new species leads to
biodiversity
Reproductive Barriers:
• Reproductive isolation- keeps 2 similar
species from breeding. Due to:
– Timing- different breeding seasons. Skunk
example.
– Behavior- different courtship/mating. Ex.
Songs of birds
– Habitat- adapted to different habitats- Fish
ex.
• Incompatible reproductive structures.
• Infertile hybrids- Horse x Donkey
mule.
Geographic Isolation separates
populations leading to new species.
• Examples include:
– mountain ranges- range of ecological zones.
– Glaciers and isolated islands
• Depends on the organisms’ ability to move
about. Examples:deep canyons,wide rivers.
Birds, pollen, coyotes vs. antelope squirrels.
• Splinter populations-separation of a small
portion of the population from the main
population.
– Crucial event in origin of a new species.
– Genetic drift- chance and Natural selection can
make the splinter population less and less like the
main population.
Do all isolated populations
survive and become new
species?
• No , not all isolated populations survive
and become new species.
• Speciation only occurs if the two
populations can no longer interbreed
Not all isolated populations survive and
become new species. with each other.
• Figure 15.6 model- pg 328.
Adaptive Radiation
• Evolution from a common ancestor that
results in diverse species adapted to
different environments.
• Transparency- Figure 15-7 pg. 328.
• Islands serve as showcase- ex.
Hawaiian islands.
– Physically diverse with differences in
altitude and rainfall .
– New lava flow supports adaptive radiation.
– Most native species are found nowhere
else.
Tempo of Speciation
• Punctuated equilibrium- a model used to
address the observation that species often
diverge in spurts of rapid change, then exist for
long periods of time with little change.
• The refining of a scientific theory of gradual
change.
• Natural selection and adaptation happen, but
when the species is “young” .
• Major changes are less common once the
species is established.
• Speciation is rapid in terms of the fossil record.
• Most successful species last 1-5 million years.
•
• Figure 15-9
In contrast to a more gradual model of evolution,
punctuated equilibrium suggests that a new species
changes most as it buds from a parent species. There is
little change for the rest of the time the species exists.
Evolution is a Remodeling
Process
Concept 15.2
Refining Existing Adaptations
• Examples- eyes, fins, flippers, wing
structures.
• What are some functions of eyes in
animals?
• How are these useful in owls, moths,fish,
rabbits, worms-planaria, humans?
• Key- Natural selection/adaptations needed
in different environments.
Eye types founds in different
mollusks
• What are mollusks?
– A diverse group of soft-bodied animals that include
snails, clams, mussels, oysters, octopus, squid.
– Invertebrates- lack a backbone.
– Characteristics- shell, muscular foot.
– 50,000-130,000 species- found in trees, gardens,
freshwater ponds,streams, estuaries,beaches,
ocean.
• Occurred over several stages of
development.
• View OnLine Activity 15.2
• Complex structures evolved from simpler
structures.
Figure 15-11
These diagrams show the range of complexity in the structure of eyes
among various species of mollusks living today.
Adapting Existing Structures
• Evolved structures fulfill different functions
later on.
• Chitin- exoskeleton (shell) of arthropodssegmented invertebrates with jointed legs
(includes insects, spiders, lobsters, etc.)
– Earlier the chitin protected them from predators in
the ocean.
– Now, on land the exoskeleton protects them from
dehydration.
• Flippers of penguins (birds)- modified wings
used now for swimming. Since penguins
occupy islands where predators are rare,
flight is not as important, but getting food in
the water is.
Embryology
• Explains genetic basis for
remodeling.
• Definition• Master gene controls development.
• Mutations can cause some bizarre
effects.
Examples• Rate/timing of some developmental
events
Example- Feet type in salamanders.
Questions:
• Does evolution always
progress towards more
complex organisms or
adaptations?
• Why or why not?
• Examples?
Concept 15.3- Fossil Record
• How Fossils Form:
– Types of fossils• Geological Time Scale:
–Earth’s history
–4 distinct eras (ages)
–Further subdivisions
–Boundaries-
• Fossil Dating:
– Relative dating– Actual age- radiometric dating
• Uranium-238
• Carbon dating
• Continental Drift/ Plate movements:
– Affects climates
– Geographical isolation
– Similar species in different locations
– Major events• Formation of Pangaea
• Breakup of Pangaea
• Mass Extinctions:
– Great species loss
– Examples• 65mya. Extinction of dinosaurs–Theories• 245mya.-90% loss of marine
animals.
– Affects• Negative
• Positive
Taxonomy
Concept 15.4 pp. 341-349
Taxonomy
• Definition• Continuous process• Goals:
– A universal scientific name for
each species
• Why is this necessary?
– Organize species into larger
groups.
• Two main systems– Older Linnaean system
– Modern cladistics
Classification
• Carolus Linnaeus
• Binomial Latin name
– First part- genus name
– Second part- species name
– Example- leopard
• An ordering of species into broader
and broader groups.
– species-genus-family-order-classphylum-kingdom
– Figure 15-24 in textbook.
– Leopard example
Figure 15-24
The leopard shares many characteristics with the lion—which belongs to the same genus—but far fewer characteristics with snails, sponges, or
earthworms, though they are all members of the animal kingdom.
Evolutionary relationships among
species
• Phylogenetic tree– “evolutionary history”
– branching pattern
• Shows common ancestors
• Figure 15-25
Phylogenetic Tree
In a phylogenetic tree, each branch point represents a
common ancestor of the species above that point.
Classification based on
homologous
structures:
• Homologous
structure definition• Example• Evolved from single structure in a
common ancestor
• The more homologous structures;
the more closely related the species.
• Homologous- structural parts match
up.
Convergent evolution
• Definition-.
– Unrelated species from similar
environments have similar
adaptations.
– Analogous structures-.
• example- wings of birds and
insects.
• similar adaptations.
• entirely different structures.
• evolved independently.
• no shared common ancestor.
Molecular data to classify
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•
•
•
Comparing DNA/ protein sequences
Research- genome
Computer technology
Used to backup fossil data
Branching pattern
Figure 15-28
Wolves and cats diverges early on
Cats and leopards diverged later.
Identifying Clades
• What is a clade?
– An evolutionary branch in a phylogenetic
tree.
– Each clade consists of the ancestral
species and all of its descendants.
– Figure 15-29. Identify the clades and
associated species.
– All organisms in a clade share homologous
structures.- derived characters.
• What is a cladogram?
– Figure 15-30.
Figure 15-29
Each shaded area in the
phylogenetic tree
highlights one clade,
such as the yellow area
including species B
through H.
Figure 15-30
This cladogram shows how derived characters can be used to identify clades among certain vertebrates (animals with
backbones). All the species shown here share a common ancestor that had a backbone. (Each clade is actually defined by
several derived characters, not just one.)
5 Kingdom scheme vs 3 Domain
System
• 5 kingdoms- Monerans-bacteria
Protists
Plants
Fungi
Animals
• 3 Domains
– Bacteria
– Archaea
– Eukaryotes