This document discusses macroevolution, megaevolution, and speciation. It defines macroevolution as changes that occur at or above the species level, such as the evolution of feathers in birds. Megaevolution refers to major evolutionary transitions, such as the change from single-celled to multicellular organisms. Speciation is the formation of new species, which can occur through mechanisms of allopatric, parapatric, or sympatric speciation as populations become reproductively isolated. Intrinsic reproductive isolating mechanisms that can lead to speciation include ecological, temporal, behavioral, mechanical and gametic isolation.

1. Macroevolution And Megaevolution
Submitted to: Dr.Fakhar Un Nisa
Class: BS-IV
Roll no: 329
Semester: 7th
Department of Zoology

2. WWW.PLANETAYURVEDA.COM
Macroevolution And Megaevolution
Microevolution
Definition:
Micro evolution is the change in alleles frequency
that occur within time through evolution.this
change is due to four different processes:
•Mutation
•Selection(artificial or natural)
•Gene flow
•Genetic drift

3. 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.

4. An Example of
Macroevolution
Macroevolution And Megaevolution
•genus of Equidae, Equus

5. 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

6. 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.

7. 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.

8. 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.

9. 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 extrinsic
Intrinsic isolating mechanism – internal
characteristics that prevent interbreeding
Differences in anatomy, physiology and
behavior

10. Macroevolution And Megaevolution
Intrinsic Reproductive Isolating Mechanisms
•Ecological
•Temporal
•Behavioral
•Mechanical
•Gametic

11. 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.

12. 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.

13. Behavioral Isolation
These albatrosses are behaviorally isolated from
other bird species by their elaborate, species-
specific courtship behavior.

14. 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.

15. 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.

16. Macroevolution And Megaevolution
Any speciation that does not involve
geographic 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

17. Macroevolution And Megaevolution
Parapatric Speciation
•Populations in contact along a
common border giant velvet
worm
blind velvet worm

18. early
reptile
pterosaur
chicken
bat
porpoise
penguin
•Change from body
form of a common
ancestor
•Produces homologous
structures
Macroevolution And Megaevolution
Morphological
Divergence
human

19. Macroevolution And Megaevolution
Morphological Divergence

20. Macroevolution And Megaevolution
Morphological Divergence
body wall (exoskeleton)
strong membrane
(extension of wall)
wing veins

21. Macroevolution And Megaevolution
Adaptive Radiations of Mammals

22. Macroevolution And Megaevolution
Megaevolution
Definition:
The term "megaevolution" is used for great changes.
A list was prepared by John Maynard Smith and which he called
The 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.

23. 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

24. Megaevolution
The Cambrian radiation example
When it was first described, the
Cambrian fossil Opabinia was thought to
be unrelated to any known phylum.
Later discoveries have shown it to be
closely related to the ancestors of
arthropods.
The Cambrian organism Marrella,
was clearly an arthropod, but
with features not seen in
modern organisms
Dickinsonia, an organism of the
Ediacaran Period that precedes
the Cambrian, whose affinity is
still unknown.