Download 15.2 Evidence of Evolution I. Support for Evolution

15.2 Evidence of Evolution
I.
Support for Evolution - theory of evolution states that all organisms on Earth have descended from a
common ancestor
a. The fossil record
i. Fossils provide evidence of evolution
ii. Ancient species share similarities with current species
iii. Fossil record important for determining ancestry of organisms and patterns of evolution
iv. Archaeopteryx fossils provide evidence of characteristics that classify it as a bird, but
shows retention of dinosaur features
v. Derived traits – newly evolved features (feathers) that do not appear in fossils of
common ancestors
vi. Ancestral traits – primitive features (teeth, nails) that do appear in ancestral forms
b. Comparative anatomy – vertebrate forelimbs have different functions but appear to be
constructed of similar bones in similar ways (shared ancestry)
i. Homologous structures – anatomically similar structures inherited from a common
ancestor
1. Not evidence of evolution, they are an example for which evolution is the best
available explanation
ii. Vestigial structures – structures that are reduced forms of functional structures in other
organisms
1. Evolutionary theory predicts that features of ancestors that no longer have a
function for that species will become smaller over time until they are lost
iii. Analogous structures – can be used for the same purpose and can be superficially
similar in construction, but are not inherited from a common ancestor
c. Comparative embryology
i. Embryo – an early, pre-birth stage of an organism’s development
ii. Vertebrate embryos exhibit homologous structures during certain phases of
development but become totally different structures in adult form
iii. The embryos shown below have a tail, pharyngeal pouches (fish=gills, reptiles, birds,
mammals=parts of ears, jaws, throats)
iv. The shared features suggest that vertebrates evolved from a shared ancestor
d. Comparative biochemistry – common ancestry can be seen in complex metabolic molecules
that different organisms share
i. Cytochrome c – enzyme essential for respiration and highly conserved in animals (it has
changed very little over time)
ii. The more closely related a species is, the greater number of amino acid sequences
shared
e. Geographic distribution
i. Darwin observed animals in South America were more similar to other animals in South
American than those in similar environments in Europe
ii. South American mara occupied a niche similar to the rabbit in Europe
South American Mara
English Rabbit
II.
iii. Biogeography – the study of distribution of plants and animals around the world
iv. Evolution is linked with climate and geological forces, especially plate tectonics, which
helps explain many ancestral relationships and geographic distributions seen in fossils
and living organisms today
Adaptation
a. Types of adaptation – a trait shaped by natural selection that increases an organism’s
reproductive success
i. Fitness – measure of the relative contribution an individual trait makes to the next
generation. Often measured as the number of reproductively viable offspring that an
organism produces
ii. Camouflage – morphological adaptations that allow them to blend in with their
environments, allows organisms to become almost invisible to predators
Leafy Sea Dragon
Malaysian Orchid Mantis
iii. Mimicry – one species evolves to resemble another species, increases an organism’s
fitness, mimics are protected because predators can’t always tell them apart
Monarch Butterfly
Viceroy Butterfly
Western Coral Snake
California Kingsnake
iv. Antimicrobial resistance – species of bacteria that have developed a drug resistance,
some diseases that were thought to be contained, re-emerge in a more harmful form
b. Consequences of adaptation
i. Spandrel example
1. Some features in organisms are like spandrels, because even though they are
prominent, they do not increase reproductive success
ii. Human example
1. Human baby helplessness is not an adaptive purpose, merely a consequence of
big brains and upright posture due to human pelvic structure