Download The Theory of Evolution

The Theory of
Evolution
U NI T 5 - B IO LOG Y
Evolution is:
1. Change with
time
2. Descent with
modification
Evolution is:
3. Plants and animals of today are
modified forms of plants and animals
of the past
4. Organisms vary and new forms
appear, while old forms decline or
become extinct
**Evolution is theologically neutral – it
interprets a natural process
• It describes how – not why
• It is based on recognition of order – not purpose
EVOLUTION is NOT:
1. Man came from monkey
EVIDENCE OF EVOLUTION
• Genetic Comparison
• Fossils
• Anatomical Studies
• Functionless Structures
• Embryological Development
2 Theories of Evolution
1. Lamarck (1801):
•
Observed a relationship between the organism
and its environment.
•
Recognized change in living things over long
periods of time.
Lamarck:
• But he was INCORRECT in concluding that the environment acted
directly on organisms to produce hereditary change in relation to
need, use or disuse, or passing on of acquired traits.
2 Theories of Evolution:
2. Charles Darwin:
•
In 1831 was recommended as a naturalist on
HMS Beagle, a ship chartered for a five-year
collecting and mapping expedition to South
America and the South Pacific.
Darwin:
•
Job: collect, study, and store specimens
•
Developed a hypothesis based on observations, specifically in The
Galapagos Islands
–
Studied and compared the anatomy of many species of reptiles, insects, birds,
and flowering plants.
• Noticed that these species were unique to the islands, yet similar to
species seen in other parts of the world.
Darwin’s Finches
• Darwin’s observations – all the finches
on the Galapagos island looked about
the same except for the shape of their
beak.
• Conclusion – all the finches were
descendants of the same original
population.
• The shape of the beaks were
adaptations for eating a particular type
of food (Ex. Long beaks were used for
eating insects, short for seeds)
Darwin observed finches with different
beaks on the different islands
Darwin:
• Evolution = change in the gene pool of a
population in response to various stimuli
exhibited by a species OVER TIME.
What is Darwin’s Explanation for Evolution?
• Natural Selection = a mechanism for change in populations that
occurs when organisms with favorable variations for a particular
environment survive, reproduce, and pass these variations on to the
next generations.
Darwin:
• Wrote “Origin of Species”
Natural Selection:
• Adaptation = any trait that aids the chances of survival and
reproduction of an organism.
• Two types: Structural and Physiological
• STRUCTURAL ADAPTATIONS arise over many generations
Structural Adapations
• Mimicry = provides protection for an organism by enabling it to copy
the appearance of another species.
Mimicry:
Mimicry:
Structural Adaptations
• Camouflage = enables an organism
to blend in with its surroundings
– More likely to escape predators and
survive to reproduce
Camouflage – snowshoe hair
Example of Natural Selection:
• Lighter colored pepper moths less noticeable on lichen covered trees.
• Pollution kills lichens and uncovers darker tree trunks
• Frequency of color moths has changed over time in response to
pollution.
Natural Selection:
• Physiological Adaptations can develop rapidly
– Changes in an organism’s metabolic processes
• Ex: Penicillin – was considered 50 years ago as a wonder drug b/c it
could kill many types of disease causing bacteria
• Now penicillin is not as effective as it used to be because many
species of bacteria have evolved physiological adaptations that make
them resistant to penicillin
• Ex: insects/weeds have been selected for physiological resistance to
chemicals used in pesticides
Evidence for Evolution
1. Genetic Comparisons
• Nucleotide sequencing studies are used to indicate levels of relationships among species
within major taxonomic groups
Evidence for Evolution
2. Fossils:
•
Fossil records show how organisms have changed over time (millions of years)
Evidence for Evolution
3. Anatomical Studies:
–
Homologous Structures =
similarities in structure and
arrangement – likeness indicates a
genetic relationship through a
common ancestor.
• Ex: homology among the bones of the forelimb. Although these
structures show considerable differences in form and function, the
same basic bones are present in the forelimbs of humans, cats, bats,
porpoises, and horses.
Evidence for Evolution
4. Functionless Structures:
–
Vestigial Structure = any body structure that is reduced in function in a living
organism but may have been used in an ancestor.
–
Examples:
–
–
–
Pelvis in snakes
External ears and pelvis in whales
Humans: appendix, ear muscles, nictating membrane, wisdom teeth
Evidence for
Evolution
5. Embryological
Development
–
Development of the
phylum – in the
embryonic stage it is
difficult to distinguish
fish, amphibians,
reptiles, birds, and
mammals.
Microevolution
• Microevolution = evolutionary change below the level of species, and
refers to changes in the frequency within a population or a species of
its alleles (alternative genes) and their effects on the form, or
phenotype, of organisms that make up that population or species.
• Relatively short period of time
• Population – members of single species living & reproducing in a
specific area.
Causes of Microevolution
• Genetic Drift = change in allele frequencies in a gene pool due to
chance.
– Increase/decrease based on which members survive & reproduce
– Greater impact in smaller populations
– Types: bottleneck effect, founder effect
Bottleneck Effect
• Bottleneck Effect = process in which a
large population declines in number,
then rebounds
– Catastrophic event leaves few survivors,
limiting the gene pool for the next
generation.
– Caused by natural disaster, habitat loss,
overharvesting
Founder Effect
• Founder Effect = random effect that can occur when a small
population settles in an area separated from the rest of the
population and interbreeds, producing unique allelic variations
– Rare alleles occur at a higher frequency in isolated populations
– Initial “founders” of the population received their alleles by chance.
– Due to small population, rare gene continually passed on.
Macroevolution
• Macroevolution = any evolutionary
change at or above the level of species
• Requires speciation = splitting of 1
species into 2 or more
– Species = do not have to look the same but
can successfully interbreed
• Prevents genotypes from entering a
population’s gene pool through
geographic, ecological, behavioral, or
other differences.
Causes of Macroevolution
1. Geographic Isolation
•
Species separated by
major physical
boundaries
•
Ex: Oceans, rivers,
mountains
Causes of Macroevolution
2. Habitat Isolation
•
Live in close proximity, but rarely interact
due to different habitats
•
Ex: Jungle – canopy dwellers vs those living
on the forest floor
Causes of Macroevolution
3. Temporal Isolation
•
Live together but reproduce at different times of the year.
Causes of Macroevolution
4. Behavioral Isolation
•
Courtship patterns are used to
recognize mates.
•
Chemical, vocal or physical indicators
•
Ex: meadowlarks – have overlapping
ranges & similar in appearance, but their
songs separate them behaviorally
Causes of Macroevolution
5. Mechanical Isolation
•
Floral structures or animal genitalia are incompatible making reproduction
impossible.
Causes of Macroevolution
6. Gamete Isolation
•
Gametes from incompatible
species will not fuse together
to form a zygote
•
Fertilization has occurred but a
hybrid offspring cannot
develop or reproduce
•
Ex: liger