Post on 30-Dec-2015
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BiogeographyBiogeography
• This is the study of the geographical distribution of species, both present-day and extinct.
• Geologically separate areas tend to be inhabited by organisms that are ecologically similar: on islands, the organisms tend to be unique.– E.g. the development of marsupials in
Australia but not elsewhere.
The Fossil RecordThe Fossil Record
• Any non-living object obtained from the ground that indicates the former presence of a living thing is a fossil.
• Fossils are the remains of living things – bones, shells, or other parts resistant to decay – or their traces such as footprints or burrows that have been preserved in the rock.
The Fossil RecordThe Fossil Record
• Where rock strata can be aged, the succession of fossils in the layers show that the most primitive forms of life are the oldest strata.
• The progression of the fossils follows the evolution of life as we know it from other sources.
Formation of FossilsFormation of Fossils
• Most fossils occur in sedimentary rock.
• Sediments in the sea gradually cover the dead body on the sea floor and petrify it.
The ProcessThe Process
• A dead animal falls to the sea floor.• Sediment covers the skeleton; other
bodies fall to the new sea floor.• Time passes; layers of different rocks
form.• Movement of the Earth’s crust folds
the rock layers.• Erosion of the rock means that fossils
can be seen.
Comparative AnatomyComparative Anatomy
• Homologous Structures – these show similar characteristics resulting from common ancestry.– E.g. pentadactyl limbs
Comparative AnatomyComparative Anatomy
• Analogous Structures - these have the same function but different ancestry.– E.g. birds and insects have wings.
Comparative AnatomyComparative Anatomy
• Vestigial Organs – these are organs that have become reduced or have lost their function.– E.g. the tail bones in humans and the
wing bones in a kiwi.
Comparative Comparative EmbryologyEmbryology
• The early embryonic stages of all vertebrates are very similar, even though the adults are all very different.
Molecular BiologyMolecular Biology
• Species which are close in evolutionary terms have only small differences in their DNA and proteins.
• Even organisms from different taxonomic groups have some common proteins.– All living things have DNA so they must
have had a common ancestor.