Transcript Part 5

What is some evidence in support
of evolution? (5 examples)
• 1. The Fossil Record
• Fossils - preserved remnants or
impressions left by organisms that lived
in the past
• Most found in sedimentary rocks
• Younger strata are on top of older ones;
positions of fossils in the strata reveal
their relative age
• Fossil record - chronology of fossil
appearances in rock layers, marking
passing of geologic time
• Oldest fossils date from 3.5 billion years
ago, are prokaryotes.
• Fishlike fossils are oldest vertebrates,
then amphibians, reptiles, then mammals
and birds.
• Paleontologists - scientists who study
fossils - found fossilized whales that
connect them to their land-dwelling
ancestors
• 2. Biogeography- the geographic distribution of species
• Ex: Tropical animals in South America are more closely related to
species in South American deserts than to species in African tropics.
• Ex: Australia has a diversity of pouched mammals (marsupials) but few
placental mammals. They are hospitable to placental mammals.
Unique Australian wildlife evolved on island continent in isolation
from regions where early placental mammals diversified.
• Biogeography makes little sense if species were individually placed in
suitable environments. Instead, species are where they are because they
evolved from ancestors that inhabited those regions.
• Top photo shows the
isolated Australian
continent.
• Bottom photo shows
pouched (marsupial)
mammal; many
marsupials are
common to Australia.
• 3. Comparative Anatomy - the
same skeletal elements make up
the forelimbs of humans, cats,
whales, and bats - all are
mammals.
• The functions differ, but
structural similarity indicate they
descended from a common
ancestor -homology.
• Ex: forelimbs of diverse
mammals, all have same bones
(photo on left)
• Ex: human spine and knee joints
derived from 4-legged mammals
- are subject to sprains, spasms,
common injuries because of our
bipedal posture.