Download Study Guide Evolution of Animals Chapters 32-35

Study Guide Evolution of Animals Chapters 32-35
Animal General Development:
1. Most animals reproduce sexually, with the diploid stage usually dominating the life cycle.
2. In most animals, a small flagellated sperm fertilizes a larger, nonmotile egg.
3. The zygote undergoes cleavage, a succession of mitotic cell divisions, leading to the formation
of a multicellular stage called the blastula, which takes the shape of a hollow ball in many
animals.
4. During gastrulation, layers of embryonic tissues that will develop into adult body parts are
produced. The resulting development stage is called a gastrula.
5. Some animals develop directly through transient stages into adults, but most have a distinct
larval stage or stages.
6. A larva is a sexually immature stage that is morphologically distinct from the adult stage,
usually eats different foods, and may live in a different habitat from the adult.
7. Animal larvae eventually undergo metamorphosis, transforming the animal into an adult.
8. Animals share a unique homeobox-containing family of genes known as Hox genes.
9. Animal Evolution:
10. During this period (525-535mya), known as the Cambrian explosion, about half of extant
animal phyla arose, including the first arthropods, chordates, and echinoderms.
Body Symmetry:
11. Many sponges lack symmetry.
12. Some animals, such as sea anemones, have radial symmetry.
13. These animals have top (mouth) and bottom sides, but not front and back ends and no left and
right sides.
14. Many animals have bilateral symmetry. A bilateral animal has two axes of orientation: front to
back and top to bottom.
15. Bilaterally symmetrical animals have dorsal (top) and ventral (bottom) sides, left and right
sides, and anterior (front) and posterior (back) ends.
16. Germ Layers:
17. Ectoderm, the germ layer covering the surface of the embryo, gives rise to the outer covering
and, in some phyla, to the central nervous system.
18. Endoderm, the innermost germ layer, lines the pouch that forms during gastrulation (the
archenteron) and gives rise to the lining of the digestive tract or cavity and the organs derived
from it, such as the liver and lungs of vertebrates.
19. Animals with only two germ layers, such as cnidarians and comb jellies, are diploblastic.
20. Other animals are triploblastic and have three germ layers.
21. In these animals, a third germ layer, the mesoderm, lies between the endoderm and the
ectoderm.
22. The mesoderm develops into the muscles and most other organs between the digestive tube
and the outer covering of the animal.
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Body Cavity in Triploblastic animals:
23. Most triploblastic animals possess a body cavity (a fluid- or air-filled space located between
the digestive tract and the outer body wall) known as a coelom.
24. A “true” coelom forms from tissue derived from mesoderm.
25. The inner and outer layers of tissue that surround the coelom connect and form structures
that suspend the internal organs.
26. Animals that possess a true coelom are known as coelomates.
27. Some triploblastic animals have a cavity formed from mesoderm and endoderm.
28. Such a cavity is a “pseudocoelom,” and animals that have one are called pseudocoelomates.
29. A pseudocoelom is a fully functional body cavity, despite its name.
30. Some triploblastic animals lack a coelom.
31. These animals, known as acoelomates, have a solid body without a body cavity.
32. Prtostome and Deutrostome Development:
33. Most animals can be categorized as having one of two developmental modes: protostome
development or deuterostome development.
34. The differences between these modes of development center on cleavage pattern, coelom
formation, and blastopore fate.
35. Many protostomes undergo spiral cleavage, in which the planes of cell division are diagonal to
the vertical axis of the embryo.
36. Most protostomes also show determinate cleavage, whereby the developmental fate of each
embryonic cell is determined very early.
37. Most deuterostomes undergo radial cleavage, in which the cleavage planes are parallel or
perpendicular to the vertical axis of the embryo.
38. Most deuterostomes show indeterminate cleavage, whereby each cell in the early embryo
retains the capacity to develop into a complete embryo.
39. The indeterminate cleavage of the human zygote makes identical twins possible.
40. In gastrulation, the developing digestive tube of an embryo initially forms as a blind pouch, the
archenteron, which becomes the gut.
41. As the archenteron forms in a protostome, initially solid masses of mesoderm split to form the
coelom.
42. In deuterostomes, mesoderm buds off from the wall of the archenteron and hollows to
become the coelom.
43. In protostomes blastopore develops into mouth but
44. In deuterostomes blastopore develops into anus.
45. Complete digestive system has mouth to feed and anus to defecate
46. Segmentation is the internal divisions of muscles, nervous tissue and excretory organs, also
depicted externally in most animals.
47. Phylum Porifera: basal animals, no true tissues, no nerve cells, diploblastic (2 germ layers
ectoderm and endoderm),
48. Porifera = Sponges are the simplest animals. Sponges may have asymmetric or radial symmetry.
No true tissues present. Epidermal cells line the surface. Collar cells line spongocoel or radial
canals and establish water current and capture food with flagella. It is called Filter Feeding.
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Amoebocytes lie in between the 2 layers and secrete Spicules – spine like skeletal structures
formed of lime or silica or sponging fibers. No nerve cells evolved yet.
49. Class Calcarea has simple marine sponges like Scypha and Grantia. Spicules are made of lime
(calcium carbonate) and are 2-4 rayed.
50. Glass Sponges have 6-rayed spicules of silica and look like glass in a dead organism, found in deep
water. Euplactella or Venus flower basket is famous example.
51. Class Demospongiae has about 7000 species and is the largest class of sponges. Spicules are
formed of protein sponging or silica or both. All large sponges belong to group. Most are marine
species but Spongilla is a fresh water sponge.
52. Phylum Ctenophora includes comb jellies have 8 comb rows of fused cilia for swimming, radial
symmetry, triploblastic (have 3 germ layers), most species live on other species. Taxonomic
position is not clear.
53. http://www.ucmp.berkeley.edu/cnidaria/ctenophora.html
54. Phylum Cnidaria: Diploblastic, radial symmetry, true tissues, no body cavity, cnidocytes for
capturing food and defense, body forms polyp and medusa, mouth leads to gastrovascular cavity,
intracellular and intercellular digestion, asexual reproduction by budding, sexual reproduction by
fertilization of egg by sperm produced in gonads, and planula larva
55. Phylum Cnidaria has 4 classes:
56. Hydrozoans: both polyp and medusa, simple polyp, Hydra (only polyp, solitary), Obelia (colonial),
Physalia
57. Scyphozoans: Adult has only medusa, polyp is scyphistoma larva, Jellies, Aurelia
58. Anthozoans: Only polyp no medusa form, polyp divided by vertical partitions – mesentries: Sea
anemone = Metridium is solitary, Corals are mostly colonial and deposit lime around polyps and
may form coral reef
59. Cubozoans: Box jelly has a cube like body with only 4 tentacles
60. Refer exercise 36 in lab manual for detail of classes or examples
61. Cnidarians (jelly fishes, corals) have a characteristic stinging cell cnidocyte. Most of the times, it
paralyses the prey but may trap it. 2 main body layers with a jelly layer in between. True tissues
and organs evolved including the nerve cells. Incomplete digestive system and radial symmetry is
observed in cnidarians.
62. Main Body Forms = Polyp and Medusa - Polyp – has a cylindrical body with a mouth and a ring
of tentacles armed with cnidocytes. Manubrium is a conical projection around the mouth.
Incomplete digestive system because no anus present. Mostly polyp is sessile and medusa is
motile. Medusa is bell shaped with mouth at the lower side. Manubrium is divided into oral
arms which lead to mouth. The gastrovascular cavity is divided into radial and circular canals.
Tentacles cover the rim of bell.
63.
Physalia = Portugese man of war – has an air sac to float and has both specialized
polyps and medusa in the colony. It can trap preys like fish and others with its long
tentacles.
64. Aurelia = Jelly fish has a large medusa, mouth is surrounded by 4 arms, 4 horse-shoe shaped
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gonads having either eggs or sperms, can be seen through the bell. Polyp is reduced or absent in
the life c
65. Sea Anemone = Metridium has advanced popyp with several rows of tentacles and
gastrovascular cavity divided by partitions.
66. Corals are advanced polyps, mostly colonial, and deposit lime around them and look like stone
having pores. When living each pore has a single individual formed of a polyp. Most corals
harbor algae in them and can grow better in clear waters. Pollution of oceans is resulting in
elimination of corals from large areas of sea-beds.
67. Platyhelminthes = flat worms – Thin long bodies, bilateral symmetry, cephalization initiated,
incomplete digestive system with only mouth, space between internal organs and body wall
filled = Acoelomate, bisexual = monoecious animals.
68. Planaria – a member of free-living flat worms, head has 2 eye-spots, 2 auricles – lateral extensions
of head, mouth in the middle, branching gut (digestive system), slow moving bottom dwellers
which feed on small animals or dead animals.
69. Parsitic flat worms include flukes and tapeworms.
70. Flukes are parasites living in the liver, intestines, lungs or blood vessels of vertebrates. Oral
sucker around mouth and ventral sucker on ventral side help fluke to attach host and feed on
the tissues and blood. Fresh water snail is an intermediate host in life cycle of most flukes.
71. Tape worm - It does not have any digestive system, absorbs food through body surface (is
absorptive instead of normal Ingestive mode of animals). It is very long, has a very tiny scolex
with hooks and suckers to attach to intestine.
72. Nematoda = Round worms – are amongst most widely distributed and most abundant animals
found everywhere including soils, water, marine or fresh, animal and plant tissues. You observed
the vinegar eels in undistilled vinegar and some are found in undistilled beer. Most round worms
are free living but many are human parasites – Ascaris.
73. Complete digestive system – 1st to develop tube within tube body plant and a complete
digestive system. Pseudocoel – the false body cavity is present but is not lines by peritoneum
membranes. Parasitic round worms lack attaching organs like suckers or hooks found in
parasitic flat worms. Round worms are dioecious – sexes are separate, males are smaller and
narrow and females are longer and broader.
74. In Protostomes, Mouth (1st mouth) develops from blastopore. Protosomes include Flat
worms, Round worms, Rotifera, Mollusks, Annelids and Arthropods.
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75. Phylum Mollusca has animals with soft body dorsally covered by a skin fold called Mantle and
have a single ventral foot. In majority of mollusks mantle secretes a shell. Most have a tongue like
radula with rasping teeth
class
shell
Feed on
Foot
gastropods
Conical spiral
Most on
Extensible muscular
Body
parts
exampl
Head, tentacles,
radula, jaws
snails
bivalves
2 similar hinged parts
Planktons, filter feeder
Hatchet like, used for
burrowing
No head or tentacles or radula
cephalopods
Mostly reduced
predators
Divided into arms /
tentacles
Head, radula, eyes,
Clams, oysters, scallops
Squids, octopus, nautillus
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76. Phylum Annelida includes segmented animals with coelom the true body cavity. Annelids have
well developed digestive, circulatory, nervous and reproductive systems. But use skin as the
respiratory system. Some of them have external gills. They have stiff bristles called setae or
chaetae for locomotion.
class
Locomote
Live in
Feed on
character
Sexes
Neries (polychaetes)
parapodia
Marine water
Small animals, trap
planktons
Tentacles on head
separate
Earthworms (oligochates)
setae
Burrowing in land
Organic matter rich soil
Leeches (Hirudinea)
Oral and posterior sucker
Water or land
Blood, are ectoparasites
Permanent clitellum
bisexual
Temporary clitellum
bisexual
77. Phylum Arthropoda has animals with exoskeleton of hard plates of chitin and jointed appendages.
78. These are the largest group of animals and were 1st to colonize land. Most have a respiratory
system of cuticular tubes called Trachea which directly carry oxygen to the tissues.
class
Antenna
Body
regions
Walking legs
crustaceans
2 pairs
Cephalothor
ax
5 pairs
arachnids
absent
Cephalothor
ax
4 pairs
insects
1 pair
Head,
thorax
3 pairs
Live in
Respiration
example
water
gills
Cray fish,
crab,
lobster,
On land
Book-lungs
Spiders,
scorpion,
mites
On land
trachea
Butterfly,
wasp,
beetles,
millipedes
1 pair
Head, thorax
and
2 pair/
segments
On land
trachea
Cylindr
ical
body
centipedes
1 pair
Head and
long
1 pair /
segment
On land
trachea
Flat body
79. In Deuterostomes Anus (2nd mouth) develops from the blastopore. Deuterostome animals have
2 major animal Phyla – Echinoderms and Chordates.
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80. Echinoderm (spiny-skinned) – a) radial symmetry in adult but bilateral larva b) bone like
endoskeleton or test c) water vascular system of canals and tube-feet for locomotion and
capturing food d) regenerate broken arms and other body parts.
81.
Sea Stars – have 5 thick arms with viscera extended into them and feed on Clams
or Oysters.
82. Brittle Stars – have 5 thin arms without viscera. The arms show snake like movements and get
easily broken but help them swim.
83. Sea Urchins – have very large spines coming out of test and possess Aristotle’s Lantern a
feeding device to eat sea weeds or kelps. No arms are present
84. Sea Cucumbers – have cylindrical body and pick food with their tentacles or are filter feeders.
No arms present.
85. Feather Stars – have branched 5 arms and remain attached most of the time but can swim
freely when needed.
86. Chordates possess 4 characters at least once during their life time (in embryo or larva or
adult):
a)
Notochord – an elastic chord, is replaced by vertebrae in most chordates called
Vertebrates
b) Dorsal and hollow nerve tube – develops into brain and spinal cord in vertebrates
c) Pharyngeal Gill Clefts or pouches – are slit like openings in sides of pharynx and help in
respiration in lower chordates.
d) Post-anal Tail – is present in all chordates.
Urochordate – Sea Squirt
Notochord and nerve tube in
tail of larva. Uro = tail
Body covered by test with
spicules. No head or eyes.
Fixed to sea rocks
Filter feeder
Cephalochordate –
Notochord extends into
anterior end. Cephalo = head
Fish like body has no head.
Burrowed or free swimming
Filter feeder
Vertebrates –fish m amm al
Notochord of embryo or
larva
Distinct head, eyes, fins or
limbs
Free swimming
Mostly Predators or
87. Vertebrates have jawless fishes Cyclostomes or Agnatha and Gnathostomates the vertebrates
with jaws in mouth.
88. Agnatha – Cyclostomes are jawless fishes only having unpaired fins. The circular mouth act as a
sucker a rasping tongue helps in feeding. Lamprey is an ectoparasite of sharks. Hag fish is slimy
and usually enters dead or dying animals and feeds on the soft viscera. Cyclostomes lack jaws
and paired fins/limbs of other vertebrates.
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89. Gnathostomates include fishes – animals with paired fins and Tetrapods – animals with 2 pairs
of limbs. Fishes live in water, respire with gills, skin covered with scales, have 2 chambered
heart both paired and unpaired fins. Fishes have 2 main classes Cartilaginous fishes and Bony
fishes.
Fish Class 
Position of mouth
Pharyngeal gill-slits
Scales
Tail fin
Swim bladder – to
regulate buoyancy
For example
Chondrichthyes=cartilaginous
Ventral, below the snout
Exposed and easily seen
Indistinct, small
Lobes asymmetrical
absent
Sharks and rays
Osteichthyes = bony fishes
terminal
Covered by gill cover
Distinct, large
Lobes symmetrical or unlobed
Present in many fishes, helps to
gain
Salmon, Tuna, and gold fish
90. Amphibians (amphi = both, bios = living, can breathe in air as well as water) are naked
vertebrates lacking scales/feathers / hair. They use skin as respiratory organ and developed
lungs. Amphibians moved freely on land but have to return to water to release eggs.
Fertilization is external and eggs hatch to form larva. The larva is the 1st feeding stage and is
fish like having gills. It undergoes metamorphosis to become adult amphibian. Frog  Egg
tadpole larva  Frog. For example
91. Frogs, Toads, Salamanders, and mud puppies.
Class 
Skin cover
heart
Fishes
Amphibians
Reptiles
Aves = birds
Mammals
scales
absent
scales
feathers
hair
3 chambers
4 chambered
2 chambered
3 chambered
4 chambered
Respiration by
gills
Skin, lungs
lungs
lungs
lungs
2 pairs of
fins
legs
legs
legs
legs
holding
holding
Teeth used for
Holding food
ears
absent
Eggs
Need water
Ear drum at
skin level
Ear drum in
Ear canal
Need water Laid on land
Absent replaced
by bill or beak
Chewing food
Ear drum in Ear
canal
Pinna outside
ear canal
Laid on land
Give birth
92. Reptiles developed the amniotic egg and became 1st true land vertebrates. Amnion is a fluid
filled sac and protects embryo from desiccation (drying up) on land. This eliminated the need of
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external water, like amphibians, for fertilization. They have scales on skin to prevent water loss,
and also have claws on digits and a 3-chambered heart. Eggs with lot of yolk and hatch into
adults. No larval stage present. Reptiles include turtles, lizards, snakes, alligators and crocodiles.
Dinosaurs, the most famous extinct animals, belonged to reptiles. Birds evolved as a direct line
from dinosaurs.
93. Birds are endotherms and maintain high body temperature and can live in extreme cold climates
like Antarctica. The bones are very light but strong. Body has feathers and wings. Feet are
covered with scales to indicate close relationship to reptiles. Birds also lay amniotic eggs with
large yolk and no larva needed. Due to marked parental care for the eggs and hatchlings most
birds lay only 2-3 eggs. The evolution of beak or bill helped them to specialize for different kinds
of food. Sternum developed a high flat vertical bone, keel, to accommodate bulky flight muscles.
Lungs are supported by air sacs to get oxygen even during expiration (breathing out). Due to
brilliance of colors Huxley called them ‘Glorified Reptiles’.
94. Mammals – body covered by hair, mammary glands to feed milk, specialized teeth (incisiors
for cutting; canines for tearing; premolars and molars for chewing), ear canal covered with
Pinna = auricle, and 7 vertebrae in neck.
95. Mammals include egg laying mammals, marsupials and placental mammals.
96. Monotremes = the egg laying (Oviparous) mammal – live only in Australia, lay eggs and
feed hatchlings with milk. Duck bill platypus and spiny ant eater are only 2 examples.
They are the connecting link between early reptiles and mammals.
97. Marsupials live only in Australian and South American regions. They give birth Viviparous) to
premature babies and many carry them in an abdominal pouch = marsupium. Mammary glands
are present in the pouch. Well known examples are Kangaroo, Koala and Opossum.
98. Placental Mammals – are most successful and most evolved animals including humans. Give
birth (viviparous) to mature babies. Endotherms – maintain body temperature. Most live on land.
Aquatic mammals include Whales, dolphins, seals etc and flying mammals are bats. In viviparous
animals developing embryo draws nutrition and oxygen from mother’s blood and pass out wastes
to it. Bear is omnivore but lion, tiger, wolf, cat and dog are carnivore mammals. Cattle, deer,
zebra , and giraffe are grazing animals. Monkeys, apes and humans are primate mammals.
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