Evidence and Pattern of Evolution Flashcards
are the useless remnants of structures or organs which were prominent and functional in ancestors.
These are often undersized, degenerated and nonfunctional. Man alone possesses nearly 100 vestigial structures.
Vestigial or rudimentay organs
in man is the remnant of caecum which is
large and functional in herbivorous mammals. It contains bacteria that produce the enzyme cellulase for the digestion of cellulose.
Vermiform appendix
are used in many mammals
for collecting sound waves from the surroundings. A complete set of muscles for their movements is present in the external ear of man but these muscles are nonfunctional.
Auricular muscles of external ear
What are the Vestigial Organs in Man
Vermiform appendix
Auricular muscles of external ear
Nictitating membrane or Plica semilunaris
Vestigial Tail Vertebrae
Lobe of the external ear
Wisdom teeth
Canines
Mammary glands in males
Body hair
is the third eyelid in the inner angle of each eye in man and many mammals. It corresponds to the nictitating membrane but it is completely unstretchable and nonfunctional.
Nictitating membrane or Plica semilunaris
Early embryo of man possesses an external tail but it is shed off much before the adulthood is attained. Rarely, a child may be born with a short visible tail. In adults the tail is represented by a string of caudal vertebrae, which constitute the coccyx (tail bone).
Vestigial Tail Vertebrae
is of no practical benefit to man ,
although serve d the purpose of sound gathering in the ancestors
of man.
Lobe of the External ear
are the third pair of molars. They are vestigial.
These are last to erupt or even fail to erupt.
Wisdom Teeth
in man are reduced due to taking soft food and noncarnivorous habit.
Canines
in humans are of no use and are vestigial remains.
Body hair
Vestigial Organs in Other Animals
Vestigial of Hindlimbs and Pelvic
Vestigial wings
Splint bones
Eyes in deep, dark habitats
is the reappearance of ancestral
characteristics in an organism or in the organisms of a group, which do not occur normally or which represent the reminiscent of normal structures possessed by the individuals of other groups
Atavism or reversion
the neck may possess an additional opening through which the throat or nasal cavity communicates with the exterior. This represents the opening of an additional pharyngeal pouch to the
exterior and is known as
Cervical Fistula in Man
It is devoid of vertebrae and is
removed by surgery with no trouble.
Tail
The same condition is noted in all the primates but in pigs, these occur in two rows one along either side of the chest and abdomen. Sometimes, extra-mammary glands or nipples appear in man.
Mammary glands
Man is characterized by scanty hair on the body and no hair on face but in the relatives of man (apes) hair are present profusely. A man was born in Russia with profuse development of hair on the face and body (Irish dogman).
Hair on the Body and Face in Irish Dogman
Types of Atavism
Family Atavism
Race Atavism
Atavism or Teratology
It includes sudden reappearance of a character or characters in the offspring after remaining latent in the family for several generations. This phenomenon is controlled at gene
level and can be explained by simple Mendelian laws of inheritance.
Family Atavism
It includes those cases of reversal where one or more characters of one race appear in the individuals of another race.
Race Atavism
This includes the appearance in a race of such abnormal characters which were normal in other supposedly ancestral races. The appearance of cervical fistula in man,
which actually corresponds to the gill-slit, or the appearance of external hindlimbs in a humpback
whale or the homodont dentition in piscivorous cetaceans are examples of teratology.
Atavism of Teratology
had noticed remarkable similarity
among vertebrate embryos, whose adults are markedly different
Von Baer
was impressed by the generalized pattern of
development and the general resemblances between the embryos of different groups of animals
Ernst Haeckel (1834-1919)
is the life history of an individual starting from ovum and phylogeny is the evolutionary history of the group
Ontogeny
which says “Ontogeny recapitulates phylogeny”.
Recapitulation Theory or Biogenetic Law
All start their life from a fertilized egg called
Zygote
It undergoes repeated cleavages and develops into
morula, blastula, and gastrula
Three germinal layers
ectoderm, mesoderm, and endoderm
refers to the degenerative changes wherein an active larva transforms into a sedentary adult. Adults of certain animals have degenerated features and do not show any resemblance with other animals of their group or any other group. But, their larval forms have helped in establishing their phylogenetic relationship
Retrogressive metamorphosis
It develops gonads, attains sexual maturity and starts reproduction. This is called
Neoteny or paedogenesis
The Recapitulation Theory was first proposed
by
Von Baer (1828)
every organism during its development recapitulates in an
abbreviated form the evolutionary history of its race. In
other terms, an organism repeats its ancestral history
during its development.
Recapitulation theory
is the study of fossil remains of plants and animals that
lived in the past.
Palaeontology
What is the Latin of “something to dug out”
Jossilum
are actual remains, traces or impressions left by the organisms that lived in the past and got preserved in sedimentary rocks. These include bones, teeth, shells and other hard parts of animals or impressions of plants pressed into shale or insects trapped in tree resin.
Fossils
called the ‘Father of Palaeontology’
Leonardo Da Vinci (1452-1519)
‘Founding Father of Modern Palaeontology’.
Cuvier (1800)
the process by which organic matter exposed to minerals over a long period is turned into a stony substance
Petrifaction
Types of Fossils
Unaltered remains of entire organisms
Petrified fossils (altered fossils)
Molds and Casts
Prints or Impressions
Coprolites
Under exceptionally
favourable conditions, the entire
animal body gets preserved in ice,
petroleum spring, asphalt, resin,
amber and oil-soaked ground.
Unaltered remains of entire organisms
are formed by the
replacement of organic parts of dead
and decaying organisms molecule by
molecule by minerals
Petrified fossils (Altered fossils)