Evidence for Evolution.

Fossils and Evolution

Fossil: Any non-living object obtained from the ground indicating the former presence of a living thing in a broad sense is a FOSSIL

Rock strata can be aged, the succession of fossils in the layers shows the most primitive forms are in the oldest strata

The progression of fossils follows he evolution of life as we know if from other sources

For example: Fish in the oldest strata, then amphibians, then reptiles etc.

Fossils and Evolution (a bat, duck-like birds, plants, and an icthyosaur)

Comparative Anatomy Homologous structures

Similar characteristics resulting from common ancestry

Different functions but same basic anatomy due to same ancestor

Analogous structures Same function but different ancestry

Vestigial Organs Organs that have become reduced or lost their

function

Comparative Anatomy. Examples of homologous organs.

Comparative Anatomy. Examples of homologous organs

Examples of homologous organs.

Analogous Structures

Have the same function but a different ancestry The wing of a bird and wing of insect

give the ability to fly but have no structural relationship

Vestigial Organs. a comparison of the appendix in a rabbit (left), fetal human (middle) and adult human (right).

Vestigial Organs

Vestigial structures are evidence for evolution: a species with a vestigial form of an organ is related to other species where the homologous organ is fully functional.

Vestigial remains of a pelvic girdle in a whale.

Vestigial Organs

On the surface, these animals look very different, but the relationship between them is easy to demonstrate.

Except for those bones that have been lost over time, nearly every bone in each corresponds to an equivalent bone in the other.

Comparative Embryology The early embryonic stages of all

vertebrates are very similar, even though the adults are very different

Gives the appearance of a relationship

Related organisms show similarities in their development.

Molecular Biology

Species which are close in evolutionary terms have only small differences in their DNA and proteins

Example: haemoglobin- Sequence of 300 amino acids in haemoglobin is identical to that in chimpanzees- Gorilla: 2 are different

Aligned DNA fragment and first chromosome banding patterns for man (Homo sapiens), chimpanzee (Pan troglodytes), gorilla (Gorilla gorilla), and orangutan (Pongo pygmaeus).

http://evolution.berkeley.edu/evolibrary/search/topicbrowse2.php?topic_id=46

http://sci.waikato.ac.nz/evolution/Homology.shtml#Homology

http://www.buzzle.com/articles/divergent-evolution.html

Convergent Evolution The evolution of species from different

taxonomic groups toward a similar form; the development of similar characteristics by taxonomically different organisms.

When organisms that aren't closely related evolve similar traits as they both adapt to similar environments. There are a finite number of effective solutions to some challenges, and some of them emerge independently again and again

Handout

Convergent

Bird and bat wings are analogous—that is, they have separate evolutionary origins, but are superficially similar because they evolved to serve the same function. Analogies are the result of convergent evolution.

Example of Divergent Compare how a human foot evolved to be very different

from a monkey's foot, despite their common primate ancestry.

It is speculated that a new species (humans) developed because there was no longer was a need for swinging from trees.

Upright walking on the ground required alterations in the foot for better speed and balance. These differing traits soon became characteristics that evolved to permit movement on the ground.

Although humans and monkeys are genetically similar, their natural habitat required different physical traits to evolve for survival.

Divergent Evolution

Divergent evolution occurs when a group from a specific population develops into a new species. In order to adapt to various environmental conditions, the two groups develop into distinct species due to differences in the demands driven by the environmental circumstances.

 

Divergent Evolution Divergent evolution is the process by which

related lineages develop different biological, genetic, and behavioral traits over time.

Natural selection, sexual selection, genetic drift, gene flow, and mutation are the processes that drive these changes.

Divergent Evolution Example Observe the development of the limbs in

vertebrates The vertebrate arm in a human, the side fin

of a whale (a mammal), the wing of a bat and the paws of a cat - all these evolved from one primal stock of ancestors!

One can see how it has undergone change in form and function over millions of years, adapting according to the need.