Post on 15-Jul-2015
Macroevolution And Megaevolution
Submitted to: Dr.Fakhar Un NisaClass: BS-IV
Roll no: 329Semester: 7th
Department of Zoology
WWW.PLANETAYURVEDA.COM
Macroevolution And Megaevolution
Microevolution
Definition:
Micro evolution is the change in alleles frequency that occur within time through evolution.thischange is due to four different processes:•Mutation•Selection(artificial or natural)•Gene flow •Genetic drift
Macroevolution And Megaevolution
Macroevolution
Definition:Macroevolutionary studies focus on change that occurs at or above the level of specie.•An example of macroevolution is the appearance of feathers during the evolution of birds from theropod dinosaurs.
An Example of Macroevolution
Macroevolution And Megaevolution
•genus of Equidae, Equus
Pattern of Macroevolution
Macroevolution And Megaevolution
we can think of patterns as "what happened when" All of the changes,diversifications, and extinctions that happened over the course of
life's history are the patterns of macroevolution.General patterns that recur across the tree of life:
•Stasis•Character change•Lineage-splitting•extinction
Macroevolution And Megaevolution
Biological Species Concept
Species are groups of actually or potentially interbreeding natural populations which are reproductively isolated from other such groups.
•Breeding behavior can be real or potential, if two species come together and breed then there was only one species.
•Breeding behavior in nature can be different than in captivity.
Macroevolution And Megaevolution
How do new species arise?How do new species arise?
Speciation is the development of a new species through evolution.Evolution within a species means a change in that population’s allele frequency.When two populations are separated their allele frequency changes. Since they no longer have migration between the populations, two separate species develop.There are many ways to separate two populations besides geographically.
Macroevolution And Megaevolution
Allopatric Speciation
•Allopatric means ‘of other countries’
When geographical barriers divide a population,followed by the development of mechanisms in the separated populations that prevent interbreeding.
•Geographical isolation is the most important factor in starting speciation.•Physical or behavioral changes develop that will keep the two species isolated from interbreeding.
Macroevolution And Megaevolution
Reproductive Isolation
Any factor in nature that prevents interbreeding between individuals of the same or closely related species.
Extrinsic isolating mechanism – outside of the organisms in question
Geographic isolation is extrinsicIntrinsic isolating mechanism – internal characteristics that prevent interbreeding
Differences in anatomy, physiology and behavior
Macroevolution And Megaevolution
Intrinsic Reproductive Isolating Mechanisms
•Ecological •Temporal •Behavioral •Mechanical •Gametic
Macroevolution And Megaevolution
Ecological Isolation
When two species have different habitats they will rarely have contact.
•Lions prefer open grassland, tigers prefer forest
Temporal Isolation
Two species that share the same habitat but do not mate within the same time frame.
•Two populations of the same species of plant release their pollen at different times of the year.
Macroevolution And Megaevolution
Behavioral Isolation
Even if populations are in contact and breeding can occur, they must choose to mate.Such a choice is based on specific courtship and mating displays.
Behavioral Isolation
These albatrosses are behaviorally isolated from other bird species by their elaborate, species-
specific courtship behavior.
Macroevolution And Megaevolution
Mechanical Isolation
Reproductive organs differ in size or shape or other feature.
•Different species of Alpine Butterfly look similar but have different reproductive organs.
Macroevolution And Megaevolution
Gametic Isolation
Even if mating occurs, offspring may not result if there are incompatibilities between sperm and egg, or between sperm and the female reproductive tract.
Macroevolution And Megaevolution
Any speciation that does not involvegeographic separation.e.g.Sympatric Speciation in fruit flies•Only 6% of flies interbreed•Conduct courting, mating, laying eggs in their specific type of tree•In transition to being two separate species•Mutation or combination of rare alleles •allowed flies to smell the apple trees
Sympatric speciation
Macroevolution And Megaevolution
Parapatric Speciation
•Populations in contact along a common border giant velvet
worm
blind velvet worm
early reptile
pterosaur
chicken
bat
porpoise
penguin
•Change from body form of a common ancestor
•Produces homologous structures
Macroevolution And Megaevolution
Morphological Divergence
human
Macroevolution And Megaevolution
Morphological Divergence
body wall (exoskeleton)
strong membrane (extension of wall)
wing veins
Macroevolution And Megaevolution
Megaevolution
Definition:The term "megaevolution" is used for great changes.A list was prepared by John Maynard Smith and which he calledThe Major Transitions in Evolution.On the 1999 edition of the list they included:•Replicating molecules: change to populations of molecules in protocells.•Independent replicators leading to chromosomes.•RNA as gene and enzyme change to DNA genes and protein enzymes.
Megaevolution
•Bacterial cells (prokaryotes) leading to cells (eukaryotes) with nuclei and organelles•Asexual clones leading to sexual populations•Single-celled organisms leading to fungi, plants and animals•Solitary individuals leading to colonies with non-reproducing castes (termites, ants & bees)•Primate societies leading to human societies with language
Megaevolution
The Cambrian radiation example
When it was first described, the Cambrian fossil Opabinia was thought tobe unrelated to any known phylum.Later discoveries have shown it to beclosely related to the ancestors of
arthropods.
The Cambrian organism Marrella,was clearly an arthropod, but
with features not seen inmodern organisms
Dickinsonia, an organism of theEdiacaran Period that precedesthe Cambrian, whose affinity is
still unknown.