Transcript Evidence for Evolution

Evidence for Evolution
Topic 5.1
Evolution
• Occurs when heritable characteristics of a species change over time
*Characteristics acquired over a lifetime (such as blisters) are not heritable
• Occurs through natural selection
Evidence: Selective Breeding
• Humans have been breeding plants
and animals purposefully for
thousands of years through artificial
selection
• The breeds of these animals
greatly vary from their wild
counterparts
• Shows that selection can
cause evolution
Evidence:
Fossil
Record
• The sequence of the fossil
record matches
evolutionary theory.
– Older, simpler fossils are
found in the bottom
strata of rock layers
– Newer, more complex
fossils are found in the
upper strata of rock
layers
Evidence: Fossil Record
• Sequence of the fossil
record matches theory:
– Plant fossils appear on
land before animal
(herbivores) fossils do
– Some sequences of
fossils are known
• Link together common
ancestors
• Predicts close living
relatives accurately
Evidence: Homologous
Structures
• Homologous structures are structures in
different species that may look different,
perform different functions but have a common
structure and common origin.
– Ex: forelimbs in humans, cats, whales and bats
Pentadactly limb: Forelimb
• Homologous structures are not to be confused with
analogous structures
– Analogous structures have similar functions and may have
similar shapes, but do not have a common origin.
– They have evolved independently of each other
Evidence: Patterns of Variation
• If populations gradually diverge over time, we should be able to see
examples of populations in different stages of divergence
– Variation within a species that is recognizable, but not enough to be
considered a different species.
• Peppered moths (Biston betularia) have natural variation in their wing
colors
– Melanic: dark colored wings (morpha: typica)
– Non-melanic: light colored wings (morpha: carbonaria)
• Peppered moth populations in pre and post industrial England
Explain the trends seen in the graph above
Evidence: Speciation
• Populations of a species can gradually diverge into
separate species by evolution
– Speciation occurs when a population becomes separated
into two or more groups and are cut off from breeding
with each other.
• Over time each group will evolve in different ways, creating
distinct characteristics.
• If the two different populations can no longer successfully breed
with each other, they have speciated into two distinct species.
*Speciation occurs often on islands where species are geographically
isolated.
• These populations are endemic: only found in a distinct geographic areas.
Evidence: Speciation
• Geographical distribution of species matches
the idea of gradual speciation
*Different species of mockingbirds are
distributed in the galapagos islands
suggesting the main island was
populated first and outlying islands
populated from the main island species
then speciated.