Evidence for Evolution

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Evidence for Evolution

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Evidence for Evolution . Darwin's theory of evolution by natural selection . Supported by evidence gathered over a century Evidence must be gathered to support the theory of evolution- THE THEORY CANNOT BE PROVED EVIDENCE Planetology of fossils Biogeography Comparative anatomy - PowerPoint PPT Presentation

Transcript of Evidence for Evolution

Page 1: Evidence  for Evolution

Evidence for Evolution

Page 2: Evidence  for Evolution

Supported by evidence gathered over a century

Evidence must be gathered to support the theory of evolution- THE THEORY CANNOT BE PROVED

EVIDENCE Planetology of fossils Biogeography Comparative anatomy Comparative embryology DNA sequencing --> biochemistry

Darwin's theory of evolution by natural selection

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What is Paelontology : The study of fossils – direct evidence of existence of an organism How it supports evolution? sequence of fossils found in rock formations should reflect the order of changes observed in organisms that originated from a common ancestorLaw of superposition: sequence in which they are laid down indicates the order in which they were formed

PALEOTOLOGY

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Example :• Evolution of the modern horse from a small animal

which lived 55 million years ago. This animal browsed on trees and bushes, had smaller teeth and 4 toes on the front and 3 toes on the back. The modern horse is much larger and only has one toe on each foot. These changes were probably due to a change in environment – reduction in rainfall and swampy areas becoming dry grasslands.

Prediction by Darwin : Fossil record should yield intermediate forms – organisms that show transitions from one group to another ‘missing links’

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What is Biogeography?: study of the geographical distribution of organisms both living and extinct.

How it supports Evolution ?: Supports this feature of the theory of evolution…for a new species to arise, a group of individuals must become isolated from the rest

BIOGEOGRAPHY

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Example :Ancient group of flightless birds that are believed to have evolved from a common ancestor on Gondwana and different populations evolved on the isolated southern continents as they drifted apart.

Australia- emu New Zealand-kiwi South America- Rhea Africa- ostrich PNG and Australia – cassowary

Also, there are no similar flightless birds on the northern continents . Thus flightless birds arose as a result of the isolation of the continent .

Prediction by Darwin :The new species should resemble species with which they shared a habitat: those that lived close by or in area with similar environmental conditions OR those that lived in a common area before it split up eg. Gondwana

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What is Comparative embryology ?: the comparison of the developmental stages of different species . Suggests common ancestor because embryos of closely related organisms have homologous parts Prediction by Darwin : species that are related show similarities in their embryonic development

COMPARATIVE EMBRYOLOGY

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Evidence and Example : Vertebrate embryos show similarities in their early devleopmetn e.g. fish, amphibian, reptiles, birds and mammals in that they all show the presence of

developed into internal gills in fish onlydeveloped into external gills in tadpoles developed into part of the Eustachian tube ( airway connecting middle ear with throat) in mammals other vertebrates- no further gill formation forms

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What is Comparative anatomy?: studies of similarities and differences in structure between different organisms.

Prediction by Darwin : if organisms are more closely relation ( recently separated from common ancestor) they should be more similar in structure than organisms which separated earlier. Common structures- evidence of similar inherited

characteristics (genes) from common ancestors

COMPARATIVE ANATOMY

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Homologous structures – Forelimbs

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Evidence and Examples : involves homologous structures. Analogous structures DO NOT provide evidence for evolutionary relatedness but rather for evolution of structures to serve a common purpose in a common environment

Homologous structures – evidence of divergent evolution

Analogous structures- evidence of convergent evolution

Organs that have the same basic structure and same evolutionary origins but show modifications because they are used in different ways

 

e.g. flowering plants share similar arrangement of their leaves, structure of vascular tissue in stems and their flower structure

Organs that differ greatly in their basic plan yet have evolved independently to become similar because they were selected to be used for a similar purpose

e.g. Australian echidna and European Hedgehog- both developed protective spines to discourage predation

Vestigial structures provide evidence of common ancestry: evolutionary remnants of body parts that no longer serve a useful function e.g. reduced tail and an appendix in humans – have evolved because they no longer carry out a useful function in that animals lifestyle.

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What is DNA sequencing?:DNA sequencing- compares variation in the order of bases in gene DNA

Evidence for Evolution :Confirmed that humans are more closely related to other mammals than to reptiles

DNA SEQUENCING - BIOCHEMISTRY