Evolution: The Unfolding Tapestry of Life Evolution is the unifying and foundational concept in biology that explains the diversity of life on Earth and how living organisms have changed over time. At its core, evolution asserts that all species of life share a common ancestry and have gradually transformed through a process of descent with modification. This transformative journey, guided by the forces of natural selection, genetic drift, and other mechanisms, has shaped the astonishing array of life forms that populate our planet today. Foundational Aspects: Founder: Charles Darwin The father of the theory of evolution is Charles Darwin, an English naturalist who, in 1859, revolutionized scientific thought with his seminal work, "On the Origin of Species." Darwin's groundbreaking insights were the result of extensive observations during his voyage on the HMS Beagle, coupled with years of meticulous study and experimentation. In his work, Darwin introduced the concept of natural selection, proposing that species with traits advantageous for survival and reproduction are more likely to pass those traits to the next generation, gradually leading to the adaptation of populations over time. Key Concepts: Natural Selection: The cornerstone of Darwin's theory, natural selection, is the process by which organisms with traits better suited to their environment have a higher chance of surviving and reproducing. Over successive generations, these advantageous traits become more prevalent in a population, leading to adaptation. Descent with Modification: Evolutionary change occurs through the passing of traits from parent to offspring with modifications. As organisms reproduce, slight variations in traits may accumulate, eventually resulting in significant changes over long periods. Common Ancestry: Darwin proposed that all living organisms share a common ancestry. This idea is supported by the existence of homologous structures (similarities in anatomy) among different species and the presence of vestigial organs—structures with reduced or no function but with clear functions in other species. Fossil Record: The fossil record provides crucial evidence for evolution by revealing the existence of extinct species with characteristics that bridge the gap between past and present forms of life. Fossils document the changes in organisms over geological time, supporting the concept of gradual transformation.

1. EVOLUTION

2. A process by which different kinds of living
organisms have developed and diversified
over time.
life is thought to have started from
something small from a common ancestor to
all species.
According to Charles Darwin: "Descent with
modifications"
(Book name: Descent of man)
EVOLUTION

3. ALL
LIVING THINGS
ARE RELATED

4. EVIDENCE OF EVOLUTION:
Evolution leaves observable signs
Darwin's theory of evolution is mainly based on geographical distribution and fossils
record.
Bio geography
fossils record
Comparative Anatomy
Evidence from classification
Evidence from vestigial organ
Molecular evidence of evolution
Biochemical evidence of evolution
Embryological evidence of evolution
Evidence comes from many different areas of biology
let's discuss now some of the evidence
1.
2.
3.
4.
5.
6.
7.
8.

5. BIOGEOGRAPHICAL EVIDENCE:
The first idea of evolution.
Bio=Life - Geo=Earth - Graphy = distribution
"THE GLOBAL DISTRIBUTION OF ORGANISMS AND THE UNIQUE
FEATURES OF ISLAND SPECIES REFLECT EVOLUTION AND
GEOLOGICAL CHANGE."
ARMADILLOS: ARMORED MAMMALS THAT LIVE ONLY IN AMERICA DEVELOPED FROM
GLYPTODONTS ABOUT 35 BILLION YEARS AGO

6. POLAR BEAR
INDUS DOLPHIN
BENGAL TIGERS
TORTOISE ETC

7. PALEONTOLOGY:
Study of Fossils
Paleo botany (plant fossils) Paleozoology (study of animal fossils)
FOSSILS: ARE EITHER ACTUAL REMAINS OR TRACES OF ORGANISMS THAT LIVE IN
ANCIENT GEOLOGICAL TIMES. THEY MAY BE EMBEDDED IN THE SAND, RESIN, OR
ICE, AND UNDECOMPOSABLE PARTS LIKE BONES, TEETH, ETC
FOSSIL RECORD: A SUCCESSION OF FOSSILS IS STRONG EVIDENCE IN FAVOR OF
EVOLUTION.
EVIDENCE: ARCHAEOPTERYX
(Archeo old, pteryx wings) in Bravalia Germany about 150 years ago
Unlike modern birds they had teeth, a long tail having 20 vertebrae, and wings
with movable fingers with claws all these characteristics show link with reptiles
(great evidence from reptiles to birds)

8. Fish > amphibians > reptiles > mammals > birds
Example: Evolution of the horse
Evolution of prokaryotes: Ancestors of all lives
Evolution of vertebrae: Fossils of fishes were the earliest vertebrae

9. ANATOMY:
Anatomy: deals with the study of body structure
Comparative anatomy is the study of similarities and differences in the anatomy of
different species.
HOMOLOGOUS ORGANS: SAME STRUCTURE WITH DIFFERENT FUNCTIONS
EXAMPLE: FORE LIMB OF CAT,DOG, MAN, WHALE FLIPPERS, ETC
ANALOGOUS ORGAN: DIFFERENT STRUCTURE WITH SAME FUNCTIONS YE
HOMOLOGUS K SATH DAL DO

10. EVIDENCE FROM VESTIGIAL ORGANS :
Appendix
Tail bone
pelvis and leg bones in whales, dolphins, and snakes from walking ancestors.
Ear muscles in humans
VESTIGIAL ORGANS ARE HISTORICAL REMNANTS OF CHARACTERS THAT
HAD IMPORTANT FUNCTIONS IN ANCESTORS BUT ARE NO LONGER
ESSENTIAL PRESENTALY.

11. BIOCHEMICAL EVIDENCE OF EVOLUTION
COMMON FEATURES:
THE GENETIC CODE
THE ENZYME ( EX: RNA POLYMERASE)
THE UNIVERSAL USE OF ATP AS AN ENERGY CURRENCY

12. BLOOD SERUM
3; herbivores ( goat, cow and deer etc)
Blood serum contains certain specific proteins which determine the
antigen-antibodies reactions.
EXAMPLE
test of blood sera have shown the protein relationship between;
1; man & apes
2; Carnivores ( cars, dogs and bears, etc)

13. MOLECULAR BIOLOGY:
EVIDENCE: BACTERIA
EVOLUTIONARY RELATIONSHIP AMONG SPECIES IS REFLECTED IN THEIR
GENE AND GENE PRODUCT BY MATCHING THEIR SEQUENCE OF
MONOMERS WE CAN EASILY COLLECT THE EVIDENCE OF EVOLUTION.
HUMANS AND BACTERIA HAVE COMMON PROTEINS E.G. INSULIN, AND
ERYTHROPOIETIN.

14. All three molecules consist of 104 amino acids.
the sequence of mouse and rat cytochrome C are identical
In Humans, 9 amino acid sequences were found different.
most of these substitutions in human cytochrome C are of
amino acids
with the same type of R group
In different species, the sequence of amino acids was found similar
comparison of amino acids of rats, mice, and humans.
It was found that:
CYTOCHROME C
THE COMPARISON SUGGESTS THAT MICE AND RATS ARE CLOSELY RELATED SPECIES, SHARING RESCENT COMMON ANCESTOR.
HUMANS ARE MORE DISTANTLY RELATED , SHARING A COMMON ANCESTOR.

15. EMBRYOLOGICAL EVIDENCE:
COMPARISON AMONG FISH, SALAMANDERS, TORTOISES, BIRDS, AND
MAMMALS

16. SPECIATION:
Species: a group of living organisms consisting of
similar individuals capable of exchanging genes or
interbreeding.
Speciation is the evolution of new species from a
pre-existing one by gradual modifications.
Speciation is how a new kind of plant or animal
species is created.

17. MECHANISM OF SPECIATION
ISOLATION OF
POPULATION
DIVERGENCE IN
TRAITS OF A
SEPARATED
POPULATION
REPRODUCTIVE
ISOLATION
Mating system or Habitat use

18. ALLOPETRIC SPECIATION:
This occurs when a
geographical barrier divides a
population into two smaller
populations.

19. SYMPATRIC:
Sympatric speciation refers to a speciation process when two
groups of identical species lived in identical geographical areas,
they evolve in such a way that they could no longer interbreed.
At that point, they are considered to be different species.

20. THANK YOU