The  evolutionary development  or history of a species or of a taxonomic group of organisms (The phylogeny of a group of taxa (singular: taxon) (species, etc.) is its evolutionary history)

1. Aquatic Fauna Phylogeny

2. Terminology
• Phylogeny : is The evolutionary development or history of
a species or of a taxonomic group of organisms (The phylogeny of a
group of taxa (singular: taxon) (species, etc.) is its evolutionary history)
• A phylogenetic tree is a graphical summary of this history —
indicating the sequence in which lineages appeared and how the
lineages are related to one another, every phylogenetic tree is an
hypothesis about relationships (some hypotheses are well supported by
data, others are not)

3. Descent with modification = evolution
• Definition of evolution= descent with modification from a common
ancestor
• Charles Darwin first presented this idea in his book The Descent of
Man.
• Individual species ‘split’ into two or more daughter species
• Evolution only occurs when there is a change in gene frequency within a
population over time

4. Reading a tree

5. Reading a tree…cont
• Parts of a phylogenetic tree include:
1. The tips of the tree represent groups of descendent taxa (often species) in the study
which could be a live or extinct .
2. The branch is the lines within the tree (Adjacent branches are sister taxa )
3. The nodes is the points at which branches connect, or the tips of branches, Internal
nodes connect branches; external nodes are the tips that represent taxa.
• Nodes represent the common ancestors of those descendants. Two descendents that split
from the same node are called sister groups.
• Many phylogenies also include an outgroup a taxon outside the group of interest. All the
members of the group of interest are more closely related to each other than they are to
the outgroup Hence, the outgroup stems from the base of the tree.

6. Cont..
In the tree below, species A & B are sister groups , they are each other's closest
relatives.

7. Cont..
4. The root a basal node in some trees
• Evolutionary trees depict clades which is a group of organisms that
includes an ancestor and all descendants of that ancestor.
• The separation of tips has no meaning.
• The tree’s branches can rotate freely around the axes

9. • A. Elements of a tree: root, nodes, branches and tips
• B. Same tree as in A, but rotate 90 degrees, so that evolutionary time
progresses from leg to right.

10. Phylogenetic groups
• Monophyletic derived from the same common ancestor.
• Paraphyletic groups which have evolved from a single ancestral species but
which do not contain all the descendants of that ancestor.
• Polyphyletic a taxonomic group having origin in several different lines of
descent think of the prefix “poly-‐” suggesting many common ancestors

11. Cont..

12. Unequal rates of evolution
Similarity between organisms is not necessarily equal to evolutionary
relationship.
Which one evolved faster?
– ‘3’ evolved faster than ‘2’
Which is most similar to 2? Why?
– ‘2’ is more ‘similar’ to ‘1’ than to ‘3’
However, ‘2’ and ‘3’ share a common
ancestor ‘B’

13. Derived vs Ancestral Trait
• A derived trait is one that was not present in the common ancestor.
• Ancestral (or primitive traits) are characters that were present in a
common ancestor.
• These terms are relative because it depends which common ancestor
you are referring to; every node is the last common ancestor for all
descendants of that group.

14. Evolutionary Mechanism
Microevolution (evolution on a small-scale) refers to the changes in allele frequencies
within a single population. Allele frequencies in a population may change due to
four fundamental forces of evolution:
Natural Selection
Gene Flow Genetic Drift
Mutations

15. otherEvolution effectsDefinitionThe factor
•Mutations are the ultimate
source of new alleles in a gene
pool
•Mutations can be spontaneous
or induced by numerous
external or exogenous factors.
 Many mutations are neutral,(
neither harm nor benefit), but
can also be deleterious or
beneficial.
 Mutations affect the phenotype
and reduce or increase the
fitness
 Evolutionary change is based on
the accumulation of many
mutations
Change in the DNA
sequence within a gene or
chromosome of a living
organism.
1. Mutation
•Gene flow tends to increase the
similarity between remaining
populations of the same species
because it makes gene pools
more similar to one another
Increases variability within a
population and allows for new
combinations of traits.
Gene Flow (also known as
gene migration) refers to
the transfer of genes from
the gene pool of one
population to another
2.Gene Flow

16. otherEvolution effectsDifinitionThe factor
Genetic drift—along with
natural selection, mutation, and
migration—is one of the basic
mechanisms of evolution.
Genetic drift works on all
mutations and can eventually
contribute to the creation of a new
species by means of the
accumulation of non-adaptive
mutations that can facilitate
population subdivision
Random Drift consists of
random fluctuations in the
frequency of appearance of a
gene, usually, in a small
population.
3. Genetic
drift
If you have variation, differential
reproduction, and heredity, you
will have evolution by natural
selection as an outcome. It is as
simple as that.
Natural Selection leads to an
evolutionary change when some
individuals with certain traits in a
population have a higher survival
and reproductive rate than others
and pass on these inheritable
genetic features to their offspring.
a process in which individual
organisms or phenotypes
that possess favorable traits
are more likely to survive
and reproduce
4. Natural
selection

17. Animal Characterization
based on Morphology
A. Based on Body( Shape) Symmetry
Animals can be classified by three types of body plan symmetry: radial
symmetry, bilateral symmetry , biradial symmetry and asymmetry.
B. Based on Features of Embryological Development
1. The Evolution of Tissue (diploblast/triploblast)
2. Evolution of Body Cavity (hydrostatic
skeleton/pseudocoelom/coelom[/ acoelom)
3. Embryonic Development of the Mouth (the Protostome and
Deuterostome Patterns of Development ( Gastrulation/The Tube-
within-a-Tube Design)

18. A. Evolution of Body (Shape )
Symmetry
1. Radial symmetry have no right or left sides, only a top or bottom; these
species are usually marine organisms like jellyfish and corals.
2. Bilaterally symmetry with a line of symmetry dividing their body into
left and right sides along with a “head” and “tail” in addition to a top and
bottom. as the larval stage of Echinodermata
3.Biradial symmetry is a combination of radial and bilateral symmetry, as in
the Ctenophores. Here, the body components are arranged with similar
parts on either side of a central axis, and each of the four sides of the
body is identical to the opposite side but different from the adjacent side..

20. Choanoflagellates (Collared flagellates)
 Choanoflagellates are of particular interest to
evolutionary biologists studying the origins of
multicellularity in animals.
 Choanoflagellates serve as a useful model for
reconstructions of the last unicellular ancestor of animals.
 Choanoflagellates are free-living, single-cell & colony in
aquatic environments . have a distinctive cell morphology
characterized by an ovoid or spherical cell body with
flagellum for movement (free-swimming or sessile ).

22. Porifera (Sponges)
 The simplest of all the invertebrates are the Parazoans, which
include only the phylum Porifera ( sponges) 5,000 species.
 No symmetry
 No true tissues
 or organs
 No nerves, muscles, mouth or digestive system
 Sessile , free swimming larvea
 Reproduce sexually ragmentation and asexually :hermaphrodites
 Filter feeders

24. Cnidaria (Jellyfish, Corals, Anemones, Hydroids)
 Diploblastic (the ectoderm and the endoderm)
 Radial symmetry
 Stinging cells (called cnidocytes, is used for prey capture)
 2 stages in life cycle (sessile adult polyp form and a mobile
medusa form )
 Tissues and organs
 Asexually and sexual reproduction
 Mouth and digestive cavity , The gut has only one opening
(blind sac gut)
 Live in marine environments

26. Ctenophora
 Ctenophora are transparent, ciliated gelatinous
diploblasts that live in marine habitats.
 Diploblastic (the ectoderm and the endoderm)
 8 rows or combs of cilia
 Colloblasts- adhesive structures
 Hydrostatic skeleton
 Blind sack gut
 Predators
 Relatively advanced nervous system

28. Acoelomorpha
 Very simple organism with
 Small soft-bodied animals
 Bilaterally symmetry
 Lack a coelom.
 Live in marine or brackish waters between grains
of sediment
 Swimming or crawling on other organisms
 Reproduce asexually by fission or budding and
Sexual
 They feed on detritus and prey on small animals

30. Protostomes Lophotrochoza
Ecdysoza
Rotifera
Platyhelminthes
Annelida
Mollusca
Polyplacophora
Gastropoda
Cephalopoda
Arthopoda
Crustaceans
Nematoda
Chelicerata
Bivalvia

31. Evolution of Body Cavity
 Animals develop two or three germ layers during gastrulation :
 A germ layer is a layer of cells that gives rise to a specific structure in the organism, with the :
 1-diploblasts: ectoderm; becoming the covering and endoderm, becoming the gut lining.
 2-triploblasts: ectoderm, endoderm and mesoderm; that form in between and which gives rise to the
muscles, skeleton, blood, blood vessels, and other interior body linings.
 The type of body cavity places an organism into one of three basic groups according to body plan:
body cavity generally refers to the space located between an animal’s outer covering and the outer lining of
the gut cavity—a fluid-filled space where internal organs develop.
 Coelomate animals have a fluid-filled body cavity called a coelom with a complete lining called peritoneum
derived from mesoderm Most bilateral animals, including mollusks, annelids, arthropods, echinoderms, and all
the vertebrates, are coelomates.

32. Evolution of Body Cavity
 Pseduocoelomate animals have a "pseudocoel" which is a fully functional body cavity. Tissue
derived from mesoderm only partly lines the fluid filled body cavity of these animals.
 The pseudocoelm is a blastocoel (the space in the blastula) that is retained to adulthood.
 In addition to having a body cavity, organisms with pseudocoeloms also have a complete digestive
tract -- separate openings for food to enter and undigested material to leave.
 Examples of pseudocoelomates are roundworms and rotifers.
 Acoelomate animals have no body cavity at all. Organs have direct contact with the epithelium.
Semi-solid mesodermal tissues between the gut and body wall hold their organs in place. There
are two types of acoelomate body plans. The first is characterized by two germ layers—an
ectoderm and endoderm—that are not separated by a cavity, as seen in the sponges and cnidarians.
The second is characterized by three germ layers—ectoderm, mesoderm, and endoderm—that are
not separated by a cavity. An example of this body plan is a flatworm

34. Rotifera Annelida
Platyhelminthes Mollusca
Lophotrochozoa

35. Rotifera
The rotifers are microscopic, multicellular,pseudocoelomic, have
bilateral symmetry .
They characterized by the rotating, ciliated, wheel-like
structure, the corona, on their head. The mas tax or jawed
pharynx is another structure unique to this group of organisms.
Short-lived and fast-reproducing organisms(sexually or
parthenogenetically).
The body form of rotifers consists of :
Head (which contains the corona), Trunk (which contains the
organs), Foot.

36. Platyhelminthes
 Acoelomate, bilateral symmetry
 Habitat: aquatic and moist soil
 Most species are hermaphrodites, having both female and male
reproduction organs.
:Nutrition: heterotrophic, filter feeders, parasites, scavengers – Feed on
recently dead animals, blood, host’s body
 Feeding: Pharynx used to obtain food –Planarians extend pharynx from
mouth,Carnivorous species have two or more sharp jaws
 Examples:
 Turbellaria (Planarian)
 Trematoda (Fluke)
 Cestoda (tapeworm)

37. Annelida (Segmented worms)
Bilateral symmetry, round with visible segments, The
coelom is reduced in leeches.
 Body covered by an external cuticle that is never shed or
molted.
Nutrition: Predators, parasites, decomposers
Have tubular digestive systems with openings at both ends.
Some organs and more specialized tissues.
Parapodia use for locomotion, sensation, or respiration
Reproduction: sexually(gametes formation) and
asexually(by budding or fission).

38. Mollusca
 Mollusca all have bilateral symmetry. mollusca are
coelomates.
 The mollusca have three body layers: ectoderm,
mesoderm and endoderm
 Habitat: found in saltwater, freshwater and on land.
 Filter feeder use their gills to extract organic particles
from water
 Some species have radula which are part of the digestive
system. some have a muscular foot that they use for
movement Some species have a specialized mantle or shell,
for example the snail.
 Reproduction: sexually; Some species are dioecious
whereas others are hermaphroditic.

39. Mollusca Bivalvia (Clams, Mussels, Scallops, Oysters)
 Bivalvia is a class of marine and freshwater molluscs
with laterally compressed bodies enclosed by a shell in
two hinged parts.
 Bivalves include clams, oysters, mussels, scallops, and
numerous other families of shells.
 The majority are filter feeders and have no head or
radula.
 The gills have evolved into ctenidia, specialised organs
for feeding and breathing.
 Most bivalves bury themselves in sediment on the
seabed, while others lie on the sea floor or attach
themselves to rocks or other hard surfaces.

40. Mullosca. Gastropoda (Nudibrachs)
 Gastropoda (“stomach foot”) include mollusks like
snails, slugs, conchs, sea hares, and sea butterflies.
 Gastropoda includes shell-bearing species as well as
species with a reduced shell. These animals are
asymmetrical and usually present a coiled shell.
 Most gastropods bear a head with tentacles, eyes, and a
style.
 A complex radula is used by the digestive system and
aids in the ingestion of food, Eyes may be absent in
some gastropods species.

41. Mullosca. Polyplacophora (Chitons)
 Animals in the class Polyplacophora (“bearing many plates”) are
commonly known as “chitons” and bear an armor-like, eight-plated
dorsal shell.
 These animals have a broad, ventral foot that is adapted for suction to
rocks and other substrates, and a mantle that extends beyond the shell in
the form of a girdle.
 Calcareous spines may be present on the girdle to offer protection from
predators.
 Chitons live worldwide, in cold water, warm water, and the tropics.
 Most chiton species inhabit intertidal or subtidal zones, and do not
extend beyond the photic zone.
 Some species live quite high in the intertidal zone and are exposed to
the air and light for long periods.

42. Mullosca. Cephalopoda (Squid, Nautilus, Octopuses)
 Cephalopoda (“head foot” animals) includes octopi, squids and cuttlefish.
 All animals in this class are carnivorous predators and have beak-like jaws
at the anterior end.
 All cephalopods show the presence of a very well-developed nervous
system along with eyes, as well as a closed circulatory system.
 The foot is lobed and developed into tentacles and a funnel, which is used
as the mode of locomotion.
 The mantle has siphonophores that facilitate exchange of water.
 A pair of nephridia is present within the mantle cavity.
 Sexual dimorphism is seen in this class of animals. Members of a species
mate, then the female lays the eggs in a secluded and protected niche.

43. Ecdysoz
a
Arthopoda
Chelicerat
a
Crustaceans
Nematoda

44. Nematoda (Roundworms)
 Adapted to nearly every ecosystem from marine to
freshwater.
 The body of a nematode is long and narrow, with a
thick outer cuticle.
 Most nematode species are dioecious, with separate
male and female individuals, or hermaphrodites
 Many species are ‘free-living’ and they feed on
bacteria, fungi, protozoans and other nematodes,
and play a very important role in nutrient cycling,
and other are Parasitic specie.

45. Evolution of the Appendages :
 All animals in a wide array of phyla have structures that stick out from the main body
wall and function in locomotion.
 In addition to limbs such as crab legs and the legs and wings of vertebrates, consider
the parapodia of lophotrochozoans such as polychaetes and the tube feet of
echinoderms, such as sea urchins.
 The structure of animal appendages are so diverse that it was logical to maintain that
at least some appendages evolved independently of each other.
 However, biologist recently discovered that the gene Distal-less or Dll is involved in
limb formation in diverse species.
 Their results suggest that all animals appendages may be homologous.
 The idea is that a simple appendages evolved early in the history of the Bilateria and
that subsequently, evolution by natural selection produced the diversity of limbs,
antennae, and wings.

46. Evolution of the Segmentation :
 Segmentation, the repetition of identical anatomical units, seems to be the secret behind the
diversity and longevity of the largest and most common animal groups on earth.
 Centipedes, earthworms and humans all feature the repetition of anatomically identical units
along the axis running from the front to the rear of their bodies. This characteristic, which
researchers call segmentation.
 The arthropods segmentation is impossible to miss, humans, segmentation is found in the
vertebrae of the backbone.
 Annelid worms, whose body is almost entirely formed of identical segments,
 These three groups are not closely related to one another. It is possible that they all inherited
this feature from a very distant common ancestor that lived 600 million years ago.

47.  A tail is prolongation of the backbone beyond the trunk of the body. In many vertebrates, it is
composed of flesh and/or bone but contains no viscera.
 The tails of fish and the tails of tetrapods, or four-limbed animals, are in fact entirely different
structures, with different evolutionary histories.
 Ancient juvenile fish had both a scaly, fleshy tail and a flexible fin, one sitting atop the other. A
similar dual tail structure is seen in the embryos of modern teleosts, a group of ray-finned fish that
make up more than 95 percent of living fish species.
 Over evolutionary time, to adapt to their environments, adult teleosts and tetrapods each lost one of
these tails, one lost the fleshy one, the other lost the flexible fin.
Evolution of the Tail :

48. Chelicerata (horseshoe crabs, sea spiders):
 Members characterized by the absence of antennae and
mandibles (jaws) and the presence of chelicerae (a pincer-like
mouthpart) and include six pairs of appendages, four pairs of
walking legs and two pairs feeding appendages.
 Early chelicerates were predatory arthropods but modern
chelicerates are herbivores, detritivores, predators, parasites
and scavengers.
 Depending on the group, the chelicerae and pedipalps may be
modified for feeding, sensing, defense, reproduction or
locomotion.
 Fertilization tends to be external in marine species and internal
in terrestrial

49. Crustaceans (Crabs, lobsters, shrimps):
 Crustaceans are generally aquatic and having two pairs of appendages
(antennules and antennae) in front of the mouth and paired appendages near
the mouth that function as jaws.
 Variations in appendage sequence and morphology largely define different
crustacean groups.
 Crustaceans Characterized by a hard exoskeleton, jointed limbs, each often
with two branches, two pairs of antennae and gills
 Crustacean appendages have adapted to function in sensing their environment,
defending against predators, swimming, walking, grasping, transferring sperm,
generating water movement, and in gas exchange.
 crustaceans feeding can be by Predation and scavenging, Filter feeding and
Parasitism
 The majority of crustaceans have separate sexes, and reproduce sexually.

50. Echniodermata Urochordata
Cephalochordata Chordata
Deuterostomes

51. Evolution of Gills:
• The ancestor of all living vertebrates may have had gills, a finding that adds to a
long-standing debate about the evolutionary history of gills.
• In jawless animals such as lampreys, gills form from the embryo's innermost layer
of cells, whereas in jawed vertebrates, including many fish species, gills were
thought to develop from the outermost layer. This led scientists to think that gills
evolved separately in the two lineages.
• Studied of embryonic gill formation in the little skate (Leucoraja erinacea), a
jawed vertebrate related to sharks and rays. found that most of the gill tissue
developed from the endoderm — as it does in jawless vertebrates.
• The discovery that gills seem to grow from the same tissues in both jawless and
jawed vertebrates suggests that gills may have evolved only once — in the
vertebrates' common ancestor.

53. A Phylogeny of the Deuterostomes

54. Deuterostomes Urochordata
Chordata
Vertebrates
Chodrichthyes
Petromyzontoida
Actinopterygii
Dipnoi
Actinistia
Myxinoidea
Echniodermata
Cephalochordata
Tetrapods
Amphibians
Mammals
Reptiles

55. Water vascular system evolution
 The water vascular system is a hydraulic system used by echinoderms,
for locomotion, food and waste transportation, and respiration.
 The system is composed of canals connecting numerous tube feet.
 All Recent echinoderms possess extensile tube-feet, and probably all
extinct groups had them too.
 Genetic studies suggest that echinoderm evolution occurred by means
of extensive mutation in regulatory genes inherited from bilateral
ancestors.
 Some studies suggest that Tube feet were believed to originally been
used entirely for respiration as well as feeding structures.

56. Asteroidea (Sea stars and starfishes):
 Asteroids have a characteristic star-shaped body plan consisting of a
central disc and multiple (typically 5) radiating arms and they can
regenerate arm
 Asteroids locomotion is accomplished by tubefeet from the water
vascular system.
 Common intertidal and subtidal predators preying on sponges, shellfish,
crabs, corals, worms, and even on other echinoderms.
 They reproduce by papulae with separate sex organs with radially
arranged gonads. And the larvae are bilaterally symmetrical and adults
are radially symmetrical.
 Primitive sea stars feed by sweeping organic particles into the mouth on
the underside of the disk. Advanced forms either evert (turn outward) the
stomach upon the prey for external digestion or swallow the prey whole.

57. Echinoidea (sea urchins, sand dollars, heart urchins):
 Echinoidea are exclusively marine and feeding by aristotle’s lantern
(powerful chewing apparatus)
 Echinoids have a hard calcareous shell made up of a skeleton of tightly
packed or fused plates
 Spines are primarily used for locomotion and defense against predators
some species cover them with shell fragments, algae, or encrusting
organisms to camouflage themselves from visual predators or, to provide
shade from direct sunlight.
 Echinoids are pentaradially symmetrical and, have a water vascular system.
 External fertilization by releasing eggs and sperm cells in the water

58. Evolution of the Nervous System
 The vast majority of existing animals are bilaterians, meaning animals with left and right
sides that are approximate mirror images of each other.
 The fundamental bilaterian body form is a tube with a hollow gut cavity running from mouth
to anus, and a nerve cord with an especially large ganglion at the front, called the "brain".
 Protostomes possess a nerve cord on the ventral (usually bottom) side of the body, whereas in
deuterostomes the nerve cord is on the dorsal (usually top) side.
 Worms are the simplest bilaterian animals, and reveal the basic structure of the bilaterian
nervous system in the most straightforward way.
 Annelida have dual nerve cords running along the length of the body and merging at the tail
and the mouth. These nerve cords are connected by transverse nerves like the rungs of a
ladder. These transverse nerves help coordinate the two sides of the animal. Two ganglia at
the head end function similar to a simple brain. Photoreceptors on the animal's eyespots
provide sensory information on light and dark.

59. Evolution of the Nervous System
 Nematoda have nervous system that is sexually dimorphic; the nervous systems of the two sexes,
males and hermaphrodites, have different numbers of neurons and groups of neurons that
perform sex-specific functions.
 Arthropods, such as insects and crustaceans, have a nervous system made up of a series of
ganglia, connected by a ventral nerve cord made up of two parallel connectives running along the
length of the belly.
 In amphibians the spectacular apoptosis (programmed cell death) of the cells of the larval gills,
tail and fins, and also stimulate the evolution of the nervous system transforming the aquatic,
vegetarian tadpole into the terrestrial, carnivorous frog with better neurological, visuospatial,
olfactory and cognitive abilities for hunting.
 mammals, including humans, show the segmented bilaterian body plan at the level of the nervous
system. The spinal cord contains a series of segmental ganglia, each giving rise to motor and
sensory nerves that innervate a portion of the body surface and underlying musculature.

60.  The Urochordata, sometimes known as the Tunicata, are
commonly known as "sea squirts."
 The body of an adult tunicate is quite simple, being essentially a
sack with two siphons through which water enters and exits.
 Water is filtered inside the sack-shaped body. However, many
tunicates have a larva that is free-swimming and exhibits all
chordate characteristics, yet it eventually attaches to a hard
substrate, it loses its tail and ability to move, and its nervous
system largely disintegrates. Some tunicates are entirely pelagic;
known as salps, they typically have barrel-shaped bodies and
may be extremely abundant in the open ocean.
Urochordata (Tunicates, Sea Squirts, Sea Tulips)

61.  the Cephalochordata are a very small branch of the animal kingdom. Known as
lancelets.
 Cephalochordates are small, eel-like, unprepossessing animals that spend much of
their time buried in sand.
 that cephalochordates have all the typical chordate features. The dorsal nerve cord is
supported by a muscularized rod, or notochord.
 The musculature of the body is divided up into V-shaped blocks, or myomeres, and
there is a post-anal tail. cephalochordates lack features found in most or all true
vertebrates: a brain.
 The sexes are separate, and both males and females have multiple paired gonads.
Eggs are fertilized externally, and develop into free-swimming, fishlike larvae.
Cephalochordata (Lancelets)

62. Evolution of the skin (Integument) :
 There is nothing more conspicuous about an organism than its skin. Its what defines the
boundary of its body. Skin is also the primary means through which an organism interacts
with its environment.
 The skin is designed to perform many functions. These functions include:
o Support and protect soft tissues against abrasion, microbes
o Reception and transduction of external stimuli.
o Transport of materials involved in excretion, secretion, resorption, dehydration,
rehydration
o Heat regulation
o Respiration
o Coloration - cryptic or display

63. Chordata- Vertebrate- Myxinoidea (Hagfish)
 Hagfish, also called slime eel, any of about 70 species of marine
vertebrates placed with the lampreys in the superclass Agnatha.
 Eel-like in shape, hagfishes are scaleless, soft-skinned creatures with
paired thick barbels on the end of the snout.
 Primitive vertebrates, hagfishes have a tail fin (but no paired fins) and no
jaws or bones.
 Their skeletons are cartilaginous, and their mouths are round or slit like
openings provided with horny teeth.

64. Chordata- Vertebrate- Petromyxontoida (Lampreys)
 Lamprey, any of about 43 species of primitive fishlike jawless
vertebrates placed with hagfishes in the class Agnatha.
 Lampreys belong to the family Petromyzonidae. they lack
bones, jaws, and paired fins. The skeleton of a lamprey
consists of cartilage; the mouth is a round sucking aperture
provided with horny teeth.
 Not all lampreys spend time in the sea. Some are landlocked
and remain in fresh water. They are nonparasitic, however,
and do not feed after becoming adults; instead, they reproduce
and die.

65. Evolution of jaws:
 Generally believed that the jaw arose through the simple transformation of an
ancestral rostral gill arch.
 Jawed vertebrates evolved from jawless ancestors over 400 million years ago, and
the evolution of a biting lower jaw was a critical step in vertebrate evolution.
 Early fish from the fossil record are represented by a group of small, jawless,
armoured fish known as ostracoderms. Jawless fish lineages are mostly extinct. An
extant clade, the lampreys may approximate ancient pre-jawed fish.
 The first jaws are found in placoderm fossils. The diversity of jawed vertebrates
may indicate the evolutionary advantage of a jawed mouth.
 Jaws first appear in the developing embryo as a cartilage bar similar to a gill arch.
In a shark, this develops directly into the adult jaws, but in an embryo of a bony fish
or a human being new bones appear on the outside of the cartilage.

66. Evolution of Skull :
 According to fossile forms of coelacanths and lungfishes that lived between about 390 and 360
million years ago during the Devonian Period.During this period, this lineage of fleshy-finned
organisms moved from the water to the land, thus many parts of the skeleton changed.
 The ancestors lived fully in the water and had skulls that were tall and narrow, with eyes facing
sideways and forwards. This allowed them to look around in their watery environments for
predators and prey.
 The ancestors of the first tetrapods began to live in shallower waters, their skulls evolved to be
flatter, with eyes on the tops of their heads. This probably allowed them to look up to spot
food.
 Then, the tetrapods finally moved fully onto land and away from the water, many lineages
once again evolved skulls that were tall and narrow, with eyes facing sideways and forwards,
allowing them to look around their terrestrial environments for predators and prey.

67. Chordata- Vertebrate- Chondrichthyes (Sharks, Rays, Skates)
 Sharks, skates, rays, and even stranger fish make up the
Chondrichthyes, or "cartilaginous fish."
 First appearing on Earth almost 450 million years ago,
cartilaginous fish today include both fearsome predators and
harmless mollusc-eaters.
 Members of the Chondrichthyes all lack true bone and have
a skeleton made of cartilage.
 Only their teeth, and sometimes their vertebrae, are
calcified; this calcified cartilage has a different structure
from that of true bone.

68. Evolution of Bone:
 One-celled animals don’t have any support system that holds them in a certain shape.
Plants do have a support system, but it’s the cellulose in the cell wall of each cell, rather
than bones.
 Early multi-celled animals like jellyfish and sponges and worms also didn’t have
skeletons, but beginning with arthropods, about 550 million years ago, animals began to
make specialized structures to support their bodies and give them a definite shape.
 The earliest skeletons were exoskeletons – they were on the outside of the animal.
Modern lobsters, crabs, and snails have exoskeletons.
 By about 480 million years ago, some fish were beginning to have teeth, so they could
eat other fish. To protect their heads, some fish evolved their teeth into skulls.
 By about 510 million years ago, eels began to have their skeletons on the inside as well
as on the outside (their scales). They evolved first notochords and then vertebrae to
protect their delicate spinal cords. These early inside skeletons (endoskeletons) were
made out of cartilage rather than bone. Sharks still have skeletons made out of cartilage.

69. Evolution of Scales:
 The Cyclostomes (Hagfishes and Lampreys) have no scales at all. However the fossil
evidence suggests that their distant ancestors did have some.
 Scales evolved separately in the cartilaginous fish and in bony fish. The scales of sharks
and rays are made of bone and resemble teeth in that they have a soft central area called
the pulp, a middle layer of dentine and a hard outer layer of enamel. These scales are
called denticles and are described as 'Placoid', they protrude through the epidermis and
are not wholly covered by it.
 The scales of bony fishes evolved a long time ago and in their ancient form they had
four layers, one of dense bone, one of spongy bone, one of dentine and one of enamel.
Such scales are called 'Cosmoid' and they only exist in the modern world on the
Ceolocanth (Latimeria chalumnae) or as fossils.

70. Chordata- Vertebrate- Actinopterygii (Ray-finned fishes)
 The name means "ray-finned," for unlike the
Chondrichthyes, the fins of the Actinopterygii are webs of
skin supported by bony or horny spines.
 Most actinopterygians have complex skeletons of true bone
(sturgeons and paddlefishes are exceptions).
 Ray-finned fishes are the dominant aquatic vertebrates
today, making up about half of all vertebrate species known.
 They are found in every aquatic habitat from the abyssal
depths of the ocean to freshwater streams and ponds.

71. Chordata- Vertebrate- Actinistia (Coelancanths)
 There are only two species of coelacanth and both are threatened, it is
the most endangered order of animals in the world.
 The coelacanth was long considered a "living fossil" because scientists
thought it was the sole remaining member of a taxon otherwise known
only from fossils, with no close relations alive, it evolved into roughly
its current form approximately 400 million years ago.
 Coelacanths are large, plump, lobe-finned fish that can live for 60
years or more.
 They are nocturnal opportunistic feeders, hunting fishes found in their
deep reef and volcanic slope habitats.

72. Evolution of lungs:
 Evidence suggests that gills were present in the very earliest fishes, the common
ancestor of hagfish and ray-finned fishes. However, lungs, gas-filled organs that serve
the function of respiration, also evolved very early on.
 The common ancestor of the lobe- and ray-finned fishes had lungs as well as gills. In
the lobefins, lungs stuck around, and tetrapods, coelacanths, and lungfish, all
inherited them and use them to obtain oxygen.
 The ray-finned fishes retained gills, and some of them also retained lungs for the long
haul. But in the lineage that wound up spawning most ray-fins, lungs evolved into the
swimbladder, a gas-filled organ that helps the fish control its buoyancy.
 The first lungs evolved from swim bladders in fish that gulped air and so were
already using the gas bladder as a primitive lung. Lungs eventually developed many
tiny pockets called alveoli and were covered in blood vessels to prmote gas exchange,
but fundamentally they are still inflatable bags.

73. Chordata- Vertebrate- Dipnoi (Lungfish)
 The Dipnoi are a group of sarcopterygiian fish, are commonly known as
the lungfish. Their "lung" is a modified swim bladder, which in most fish is
used for buoyancy in swimming,
 Lungfish also absorbs oxygen and removes wastes. Modern lungfish in
Africa and South America are able to survive when their pools dry up by
burrowing into the mud and sealing themselves within a mucous-lined
burrow.
 Lungfish are believed to be the closest living relatives of the tetrapods, and
share a number of important characteristics with them. Among these
characters are tooth enamel, separation of pulmonary blood flow from
body blood flow, arrangement of the skull bones, and the presence of four
similarly sized limbs with the same position and structure as the four
tetrapod legs.

74. Evolution of limbs:
 The first four-legged, land-living creatures -- known as early tetrapods -- evolved
from fish, following the transformation of fins into limbs. This fin-to-limb evolution
is a crucial, example of how morphological changes can dramatically alter life on
Earth.
 Genetic alterations governing the patterning of skeletal structures in fins may have
led to the evolution of limbs and the rise of early tetrapods.
 The forelimbs of tetrapod evolved from the pectoral fins of the ancestral fish. These
fins contain three or more basal bones connected to the pectoral (shoulder) girdle.
 However, the most of basal bones located in the anterior side (i.e. the thumb side in
the human limb) were lost in early tetrapods, and only the most posterior bone
remained as the "humerus (i.e. the upper arm of humans)."
 A key regulator protein controlling the balance of anterior and posterior fields of limb
buds of tetrapods is Gli3.

75. Chrodata- Vertebrate - Terapods- Amphibian- Anura
(Frogs,Toads)
 Include the frogs and toads.
 Shortened vertebral column (nine or fewer presacral vertebrae)
 Presence of a urostyle formed from developing tail vertebrae
 Absence of tail in adults.
 Hindlimb longer than forelimb.
 Large eyes and glandular moist skin. Smooth skins are commonly
referred to as frogs, while those with warty skins are known as toads
 Several skull bones are lacking in frogs, although their heads remain
highly ossified.
 They have external fertilization.

76. Chrodata- Vertebrate - Terapods- Amphibian- Urodela
(salamanders, Newt)
 Includes the salamanders and newts.
 Having the tail well developed and often long slander body.
 They have limbs set at right angles to the body with forelimbs and
hindlimbs of approximately equal size.
 Presence of ribs and true teeth on both jaws
 Gill slits and external gills in aquatic larvae.
 Glands in the skin discharge mucus which keeps the skin moist
 Having internal fertilization

77. Evolution of Aminotic Egg Vs Evolution of placenta
Aminotic Egg
 In Oviparous.
 The amniotic egg was an evolutionary invention that
allowed the first reptiles to colonize dry land more
than 300 million years ago. Fishes and amphibians
must lay their eggs in water and therefore cannot live
far from water.
 The amniotic egg of reptiles and birds is surrounded
by a tough outer shell that protects the egg
 Inside the shell are four sacs: chorion, amnion,
allantois and yolk sac.
Placenta
 In Viviparity.
 Placenta namely apposition or fusion
of the fetal membranes to the uterine
mucosa for physiological exchange,
 These included the first fully aquatic
mammals (whales) and flying
mammals (bats), as well as rodents
and primates.

78. Evolution of hair/fur
 Carnivora includes three independent evolutionary transitions to the marine
environment: pinnipeds (seals, sea lions, and walruses), sea otters, and polar bears.
All three lineages must contend with the thermal challenges of submersion in the
marine environment.
 The hair coat can have a variety of function, but in most marine mammals it serves in
buoyancy regulation and thermal insulation.
 Dense fur layer with high metabolic rate (to generate heat) keeps them warm.

79. Evolution of lactation
 The mammary gland has been a pivotal feature in the evolution and taxonomic
classification of animal species.
 The presence and secretory capacity of the mammary gland provided the basis for the
taxonomic grouping of species into the class Mammalia more than two centuries ago.
 Darwin hypothesized that mammary glands evolved from cutaneous glands that were
contained within the brood pouches in which some fish and other marine species keep
their eggs, and provided nourishment and thus a survival advantage to eggs of
ancestral species.

80. Chrodata- Vertebrate – Terapods-Mammalia- Monotremata
(Platypuses)
 There are only five living monotreme species: platypus.
 Platypus: feed on insects and their larvae, bivalves,
gastropods, and freshwater crustaceans.
 Platypus has Flat tail and webbed feet that help it swim on
water.
 On land, it uses its nails and feet to construct dirt burrows at
the water's echidnas are good swimmers.
 They only mammals that lay eggs; they produce milk to
nourish the young.

81. Chrodata- Vertebrate – Terapods - Reptiles- Testudinia
(Turtles)
 There are about 7 species of sea turtles; other may found on fresh water.
 Depending on the species, they may move closer to shore to the beach to
feed (Herbivores and carnivores) .
 Most aquatic turtles have flat, streamlined shells, which aid in swimming
and diving. Others have small, plastrons that give them more efficient leg
movement for walking along the bottom of ponds and streams.
 Internal fertilization with copulatory organ
External development, incubation in nests
Sea turtles start their lives inside eggs buried in the sand. After a two-
month incubation period, the young turtles hatch and run to the sea.

82. Chrodata- Vertebrate – Terapods – Reptiles - Crocodilia
(Crocodiles, Alligators):
 Crocodiles are the closest living relatives to birds and are semi-aquatic predators
that have changed little since the time of the dinosaurs.
 All species of crocodilians have similar body structures—elongated snout,
powerful jaws, muscular tail, large protective scales, streamlined body, and eyes
and nostrils that are positioned on top of the head.
 They have very powerful tails allows for fast and fluid movements in and out of
the water.
 They have a tough spiky skin on their back to protects their internal organs and
protects them from predators.
 They are oviparous and adults provide extensive parental care to young

83. Chrodata- Vertebrate – Terapods – Aves (Marine Birds)
 Birds are the most recently evolved of the vertebrate
classes, Aves evolution comes from reptiles
 Birds are warm-blooded vertebrates with feathers and
forelimbs modified as wings, jaws lacking teeth and with a
horny cover and they walk on their two hindlimbs
 There are a few kinds of birds that don't fly, but their
ancestors did, and these birds have secondarily lost the
ability to fly.
 All birds are oviparous

84. Thank you