The Descent with Modification

Evolution• Life first originated some 3.8 billion

years ago.

• Organisms come to exist by the Transfer of Genetic Material, within a surrounding cell, from one or more parents.

• Descent may occur through:– Simple clonal reproduction– Complex sexual reproduction

Lineage

• Results from “Descent through Time”

• A set of organisms interconnected through time and space by the transfer of genetic material from parents to offspring.

Modification• A component of Evolution

• Refers to a change in Genetic Material that is transferred from parent/s to offspring.

• Such Genetic Material of the offspring is different from the parent/s.

• Occurred through:– Mutation– Genetic Recombination

Population and Species• The General Units of Evolution• Species

– Groups of Populations that are related to one another by various criteria and have evolutionarily diverged from such other groups.

• Population– A group of individuals of the same

species that is usually geographically delimited.

Phylogeny

• The evolutionary History or pattern of descent of a group of organisms.

• Commonly represented in a “Cladogram”

Cladogram• A hypothesis about the lineages

and their evolutionary relationships.

Conditions of the Species

• Pleisomorphy– The ancestral condition

• Apomorphy– The evolutionary novelty

• Synapomorphy– An apomorphy that unites two or more

lineages

• Autopomorphy– An apomorphy that occurs within a

single lineage

History of Evolution

• Plato

• “The observable world is no more than a shadowy reflection of underlying “ideals” that are true and eternal for all time.”

The Great Chain of Being

“The Deity wishing to make this world like the fairest and most perfect of intelligible beings,

framed one visible living being containing within itself all other living beings of like

nature”

-Plato-

Scale of Nature

• Formed by Aristotle from Plato’s ideal.

• Represents a link in the progressions from the least, to the most perfect of creatures.

Charles Darwin

• Described as a man who defied

his own social and religious

background, not only by espousing a radical concept, but by becoming the instrument

that made it acceptable to many of his compatriots.

The Galapagos Islands

• Where Darwin had a great impact on his thinking about Evolution

• Particularly Struck by:– The absence of insect eating

warblers and woodpeckers, but finchers taking their place.

– The observation that each island contained its own constellation of species.

Jean-Baptiste de Lamrack

• Proposed the Continuity of Species – Variations among organisms

originate because of response to the needs of the environment

– The ability to respond in a particular direction accounts for the adaptation of new features.

Macroevolution

• The evolutionary changes at the species level and above.

Microevolution

• Evolution within the population of a species

Types of Evolution

• Divergent Evolution

• Convergent Evolution

• Parallel Evolution

Divergent Evolution

•  the evolutionary pattern in which two species gradually become increasingly different.

• often occurs when closely related species diversify to new habitats

• Large Scale: Responsible for the creation of the current diversity of life on earth from the first living cells.

•  Small Scale: Responsible for the evolution of two species from a common ancestor.

Convergent Evolution

•  Takes place when species of different ancestry begin to share analogous traits because of a shared environment or other selection pressure.

Parallel Evolution

• Occurs when two species evolve independently of each other, maintaining the same level of similarity. 

• Between unrelated species that do not occupy the same or similar niches in a given habitat.

Plant Evolution

The Green Plants

• Cellulosic Cell Wall

• Primary Apomorphy of the Viridiplantae:– Chlorophyll B– Thylakoids– Stacked Grana– Starch

Streptophyte

• Gave rise to the Land Plants• Apomorphy

– Oogamy

• Charophyte– A clade within the Streptophytes – Apomorphy: Plasmodesmata– Includes:

•Coleochaete•Charales•Land Plants

Embryophyta – Land Plants

• First colonization of Plants on Land during the Silurian Period (400 mya)

• Under Streptophytes/Charophytes

• Apomorphy– Embryo/Sporophyte– Cuticle– Parenchyma– Antheridium– Archegonium

NonVascular Land Plants

• Hepaticae (Liverworts)– One of the monophyletic groups– Descendents of some of the first

land plants• Mosses• Apomorphy:

– Stomates– Aerial Sporophyte Axis

• Anthocerotae (Hormworts)• Apomorphy:

– Long-lived Photosynthetic Sporophyte

TracheophytaVascular Land Plants

Apomorphies

• Independent, long-lived sporophyte

• Branched sporophyte

• Lignified secondary walls

• Sclerenchyma• Tracheary

Elements (xylem)

• Sieve Elements (phloem)

• Endodermis• Roots

LignophytesWoody Plants

Apomorphy

• Possesses the– Vascular

Cambium– Cork Cambium

Spermatophytes

• Seed Plants, a lineage within the lignophytes

• Apomorphy:– Seed

AngiospermsPretty Flower Plants

Origin of Angiosperms

• Earliest definitive fossils of Angiosperms:– Dispersed Pollen Grains– Earliest Cretaceous Period

(140mya)– Flower Fossil Record (130mya)

• Once Angiosperms arose, they rapidly radiated into several, distinct lineages, replacing gymnosperms as the dominant plant life form on earth.

Amborella trichopoda

• The Best hypothesis for the most basal angiosperm lineage– Lacks vessels– Possesses unisexual flowers with

a spiral perianth– Laminar stamens– Separate carpels

Thank You!

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