Evidences of EvolutionFOSSIL RECORD, MORPHOLOGY,

EMBRYOLOGY, AND BIOCHEMISTRY

Fossil RecordFossil – preserved remains of animal or plant.We have to take note that the fossil record will never

be complete.Why? Because geologic events obliterated much of it.1. The rest of the record is slanted toward species that has hard parts,2. has dense populations with wide distribution,3. And had persisted for a long time. Although the fossil record is substantial enough to

help us reconstruct patterns and trends in the history of life.

Fossil RecordTypes of Fossil1. Compression fossilIt is an original part of an organism that was buried

under sediments and the water squeezed out of it.E.g.Thin film of plant cuticle that remained from a leaf.2. Fossil fuelsCarbon-containing fuel derived from the

decomposed remains of prehistoric plants and animals.

a. Coal b. Oil c. Natural Gas

Fossil Record3. Impression FossilAn outline that is formed when hard parts of

a dead organism pressed against soft sediment, which then hardened after the organism decayed.

E.g.A. Foot prints B. Worm borings4. CastsFossil formed when minerals slowly replace

tissue.E.g. Long horn coral

Fossil Record5. MoldImpression that is left in rocks.A. Internal MoldB. External MoldE.g. Shell6. Mineralized Fossils Minerals replaced cells and intracellular

materials.E.g. Bones and teeth

Fossil Record7. Petrified FossilsCrystallization of minerals inside cells.E.g.Petrified wood

MORPHOLOGICAL EVIDENCE OF EVOLUTIONMorphology – the form and structure of an

organism or of a part of an organism.Do similar parts indicate an evolutionary

relationship?In Morphological Divergence, a body part

inherited from a common ancestor becomes modified differently in different lines of descent. Such parts are called homologous structures.

Morphological Divergence Among Vertebrate Forelimbs.

MORPHOLOGICAL EVIDENCE OF EVOLUTION Homologous structuresSimilar body parts that reflect shared

ancestry.Structures may be used for different

purposes in different groups, but the same genes direct their

development.

MORPHOLOGICAL EVIDENCE OF EVOLUTIONMorphological Divergence Refers to a change from the body form of a

common ancestor in a macroevolutionary pattern .

MacroevolutionEvolutionary patterns on a larger scale.Comprises large-scale patterns of

evolutionary change such as adaptive radiations, the origins of major groups and loss through extinction.

MORPHOLOGICAL EVIDENCEEven though vertebrate forelimbs are not the

same in size, shape or function from one group to the next,

They are alike in the structure and positioning of bony elements.

MORPHOLOGICAL CONVERGENCEIn morphological convergence, body parts

that appear alike evolve independently in different lineages, not in a common ancestor.

Such parts are called analogous structures.

Morphological Convergence

ANALOGOUS STRUCTURESStructures that look alike in different

lineages but did not evolve in a shared ancestor.

E.g. Bird wing – flight – feathersBat wing – flight – skin membraneInsect wing – flight - sac

EMBRYOLOGICAL EVIDENCE OF EVOLUTIONEmbryologyBranch of biology dealing with the

development of the animal embryo.Development of the fertilized egg and embryo

and the growth of fetus.

EMBRYOLOGICAL EVIDENCE OF EVOLUTIONDevelopmental Comparisons in AnimalsEmbryos of many vertebrate species develop in

similar ways.Their tissues form the same way as embryonic cells

divide, differentiate and interact.All vertebrates go through a stage in which they have

four limb buds and a tail.Adult forms of these lineages are different.Why do they differ?Answer lies with the heritable changes or the onset,

rate or completion of early steps in development.An altered body plan is advantageous.

EMBRYOLOGICAL EVIDENCE OF EVOLUTIONBody appendagesBuds form whenever homeotic gene Dlx is

expressed. Dlx gene Encodes a transcription factor that signals

clusters of embryonic cells to “srtick out from the body” and give rise to an appendage.

Hox geneHelp sculpt details of the bodies form.It suppresses Dlx expression in all parts of an

embryo that will not have appendages.

Dlx/Hox gene control system operates across many phyla.

A strong evidence that it evolved a very long time ago.

Dlx came first in some Cambrian fossils.Hox appeared later.

Comparative Embryology

Amino Acid Sequence Similarities

Amino Acid Sequence Similarities Are a Measure of Evolutionary Relatedness

The Rate of DNA hybridization reflects the degree of evolutionary relatedness.