Download Chapter 14 Principles of Evolution

Evolution
Chapter14
Observations Supporting Evolution
• Evolution – process of change through time
• Geological record – estimate that the earth is
~4.6 billion years old
• Fossil – direct or indirect remains of organisms
• Law of Superposition – in undisturbed strata,
upper layers contain younger, more complex
organisms.
• Lower strata contain older, simpler life forms.
Observations Supporting Evolution
• Comparative Cytology – looks at
similarities between cells and cell
structures
– Many organelles are structurally & functionally
similar in most organisms
• Comparative Biochemistry – similarities
between compounds in living organisms
• DNA, RNA, many proteins & enzymes
– Example cytochrome C
Observations Supporting Evolution
• Comparative Anatomy – comparison of
similarities between species
• Homologous structures – anatomical parts
w/ similar structure and origin, though they
may work differently
– Forelimbs of many different vertebrates
• Analogous structures – similar function w/
different structures
– Wings of birds & butterflies
Comparative Anatomy
• Analogous structures result from
convergent evolution rather than descent
from a common ancestor
• Convergent evolution occurs when
similar environmental pressures and
natural selection give rise to similar
(analogous) structures in distantly related
organisms
Observations Supporting Evolution
• Comparative Embryology – similarities between
early embryonic development
– Early vertebrate embryos resemble one another
– All vertebrate embryos possess genes that direct
development of gill slits and a tail
• Vestigial structures – non-functional in current
organisms, functional in ancestors
– Molar teeth in vampire bats, pelvic bones in whales
Early Evolution
• George Cuvier (1769-1832) – theory of
Catastrophism. Modern species are the ones
that survive
• James Hutton (1726-1797) and Charles Lyell
(1797-1875)– Uniformitarianism. Asserts that
Earth is very old
• Jean Baptiste Lamarck (1744-1829) – Use and
Disuse, Transmission of Acquired
Characteristics.
• August Weismann – disproved Lamarck’s theory
Darwin & Wallace
• Both proposed similar theories on
evolution at same time
• Incorporated the ideas of Lyell
• Darwin also incorporated the ideas of
Thomas Malthus (Overproduction)
• Proposed that species changed over time
by natural selection
Theory of Natural Selection
•
5 major points:
2. Overproduction – more offspring
produced than can survive
3. Competition – overproduction leads to
competition for resources
4. Survival of the fittest – some members
will have variations that make them
better fit to survive
Theory of Natural Selection
1. Reproduction – those that survive will
reproduce passing on those variations
2. Speciation – over time this will lead to a
new species
• Darwin didn’t explain how variations
arose (mutations)
• Believed that both heredity &
environmental variations were inherited
Modern Theory of Evolution
• Hugo De Vries – mutations a major source
of variation
• Modern theory supports Darwin’s concepts
of variation & natural selection with genetic
basis for variation
• Mutations & sexual reproduction basis of
genetic variation
• Mutations are spontaneous. Raw material
for evolution
Modern Evidence of Evolution
• Artificial selection is selective breeding to
produce plants and animals that possess
desirable traits
– Modern dogs descended from wolves
– In only a few thousand years, humans artificially
selected for all breeds of modern dogs
• Humans have created tremendous variation in
several species over relatively short periods of
time through artificial selection
Natural Selection Today
• Examples include:
– Coloration in Trinidadian guppies
– Pesticide resistance
Coloration
• Female guppies prefer to mate with brightly
colored males; however, brightly colored
males are more likely to be eaten by
predators
– Males found in areas lacking predators were
brightly colored
– Males found in areas with predators were duller
by comparison (predators eliminated brightly
colored males before they could reproduce)
Pesticide Resistance
• Numerous insect pests have evolved
resistance to pesticides
– Roaches developed resistance to Combat®, an
insecticide bait that acted as an agent of
natural selection
– Resistant roaches possessed a rare mutation
that caused them to dislike glucose, the main
attractant in Combat®
– At least one insect species is resistant to every
pesticide in existence
Natural Selection of Phenotypes
•
The variations on which natural selection works
are produced by mutations that arise
spontaneously
2. Natural selection selects for organisms that are
best adapted to a particular environment
–
If the environment changes, a previously
advantageous trait may become disadvantageous