GEN BIO 2 | Evidences of Evolution

Fossil Records

the remains/traces of organisms from long ago that tell us the history of life, mostly found in layers of sedimentary rock

Compression

Common for plant fossils, a plant part sinks and is covered by fine sediment. As it compresses to form sedimentary rock, that part is preserved.

Petrification

Common for animal fossils, an animal dies, decays, and is buried. Minerals seeps through and eventually replaces the organic matter.

Impression

When an animal dies on the mud, it leaves an impression. As it decays and the mud hardens to rock, there is an imprint of the animal’s anatomical details.

Cast

As an animal part sinks into soft sediment, it decays away and the imprint is filled in mud. This mud hardens into rock, imitating the original living material.

Intact Preservation

Insects are preserved through the oozing tree resin, which hardens into amber.

Transitional Fossils

bear a resemblance to two groups in the present that are classified separately, implying a common ancestor for these two groups

Incompleteness of Fossil Records

• no traces of fossil

• plates are constantly moving

• hard to discover

Biogeographical Evidence

the study of geographical distribution of fossils and living organisms

Wallace’s Line

As Alfred Russel Wallace, traveled around the Malay Archipelago, he noticed distinct patterns of animal life on either side of an imaginary boundary separating Australia and Southeast Asia.

• Asia has tigers, rhinos, elephants, orangutans, bears, leopards, thrushes, woodpeckers, pheasants.

• Australia has sugar gilders, tree kangaroos, deer, cockatoos, honey suckers, brush turkeys

Homologous Structures

structures with the same set of bones that presumably evolved from a common ancestor, but appear differently and vary in function.

Analogous Structures

They perform the same function but a very different embryological development or set of structure like bones

Vestigial Structures

anatomical features are fully developed in one group of organisms but reduced and nonfunctional in other similar groups.

Vestigial Structures in Humans

1. Tail bone/coccyx

2. Sinuses

3. Wisdom Teeth

4. Muscle in the external ear

5. Erector pili muscles

6. Tonsils

7. Male nipples

8. Palmar grasp reflex of infants

9. Pilca semilunaris in the eyelid

10. Appendix

Embryology

the study of the development of an organisms from an embryo to its adult form, common structures are shared in the embryo stage and disappear by the time the embryo reaches the juvenile or adult form

Molecular Biology Evidences

similar molecules in RNA, DNA, and proteins, suggest descent from a common ancestor with modifications.