Download 15-3 Evolution in Process Evidence of evolution: Living organisms

15-3 Evolution in Process
Evidence of evolution:
Living organisms display many clues to their evolutionary history
1.Homologous and analogous structures:
-Homologous features: are similar features that originated in
a shared common ancestor and derived from the same structures
in the embryo.
Ex. Beaks of finches are modifications of a feature found in an
ancestor common to all birds
Ex. Limbs of humans, bats, alligators and penguins are very similar
in skeletal structures
-Presence of homologous features indicates the sharing of a recent
common ancestor
-Analogous features: serve similar functions but differ in
structure and derived from different structures in the embryo
Ex. Humming bird and humming moth, both can hover to
feed on flowers nectar using their wings that evolved
independently in each animal.
2.Vestigial structures:
Are useless features for modern organisms, but were useful for an ancestor
Ex. Human tailbone
Ex. Human appendix
Ex. Sperm whales vestigial pelvic bones and leg bones
An organism with a vestigial structure probably shares a
common ancestor with another that has a functional
version of the same feature.
3.Similarities in embryology:
-The early stages of different vertebrate embryos
are similar (but they fade as development proceeds)
-Such similarities can be taken as an indication of
sharing a common ancestor
4.Similarities in macromolecules:
-The amino acid sequences in human hemoglobin and gorilla differ by one amino acid,
while between humans and frogs differ by 67 amino acids
The more similar homologous proteins are in different species, the more closely they are
related.
Patterns of evolution
Coevolution: is the change of 2 species in close association with each other
Ex. Some species of bats feed on flowers’ nectar
Bats: have slender long tongue with a brush tip to
feed and have fur on their faces and necks to pick up pollen
Flowers: have a fruity nectar and bright at night to attract
bats and to be easily located by them.
Convergent evolution
Divergent evolution
Occurs when the environment selects similar When 2 species become more dissimilar
phenotypes even when the ancestors are
resulting in new species
different from each other
1. Adaptive radiation: where many related
species evolve from a single ancestor
Ex. Sharks look similar to porpoises
Ex. Galapagos islands finches
(dolphins) while sharks are fishes and
2. Artificial selection: where the process of
porpoises are mammals
divergence is sped up artificially
They have been selected by the
Ex. Breeding dogs for certain phenotypic
environment they share by their large
characteristics resulting in different breeds
streamlined bodies and fins
with different traits.