Biology 1407 Exam 2 Notes: The Evolution and Diversity of Animal Life Ch. 18, 19
Kingdom Animalia
18.1
- multicellular eukaryotes, chemoheterotrophs, ingestive feeding, lack cell wall
- 1.3 + million species; 35 + phyla (major groups)
- first appeared about 700 m.y.a.
- have specialized cells (tissue, organs, systems)
- reproduce sexually
- most have muscle and nerve cells
- diploid stage of life cycle dominates; haploid gametes
- characteristic embryonic development and genes that control development
- most major groups are marine, fewer are freshwater, only a few phyla have
become completely terrestrial (but many species)
- informally divided into “invertebrates” (animals without a bony spine, 34 phyla)
and “vertebrates” (animals with backbone, 1 phyla,  5% of the species)
Origin of multicellular species
18.2
- from Protista species about 1 billion years ago oldest animal fossils 575 m y a
- probably colonies of cooperating individuals
- size gave advantages:
- protection from predators
- feeding on smaller prey
- more stable in the environment (current, etc)
- multicellular body of genetically identical cells allowed cell
specialization and division of labor
- major adaptive radiation about 542 m.y.a. (the Cambrian “explosion” during 15
million year time period) Refer to Geological Time Scale
15.6(15.1)
- all major animal groups’ ancestors date to this time
- homeotic “HOX” genes and switch “tool kit” genes important in animal
body structure
- serially repeated structure
*Why didn’t individual cells just increase in size?
Trends in animal evolution:
18.3
1. Increased complexity of body: specialized cells > tissues -> organs -> organ
systems
2. Increased size
3. Increased activity (relates to symmetry)
4. Development of body cavity (coelom) and tissue germ layers (ectoderm,
mesoderm and endoderm)
All organisms face similar problems: capturing food, providing each cell with food and
oxygen, coordinating activity of cells, reproducing.
Parasites adapted to different environment, vary from trends.
Phylum Porifera - sponges
18.5
- mostly marine, few freshwater, no terrestrial : 9000 species
- most asymmetrical (have no body symmetry)
- specialized cells (no tissues, organs)
choanocytes (collar cells) - feeding
amoebocytes - distribution of materials to cells
pore cells - openings for water flow
spicules - skeletal components
- very primitive, lack muscle and nerve cells
Phylum Cnidaria - “coelenterates” (jellies, hydras, sea anemones, corals)
18.6
- mostly marine, some freshwater, no terrestrial
- 10,000 species
- radial symmetry
- tissues - only two tissue layers (endoderm, ectoderm)
- incomplete digestive, digestion in gastrovascular cavity (mouth, cavity, no anus)
- nerve tissue arranged into nerve net, simple muscle tissue, no circulatory tissue
- specialized stinging cells called cnidocytes
- 2 distinct body forms: attached polyp and free-floating medusa
- coral polyps secrete calcium carbonate (limestone) skeletons - build reefs,
form symbiotic relationship with algae
Bilateral symmetry:
18.3
cephalization - “forming a head” (head, tail, top, bottom, left, right)
nervous system (sensory organs, brain) directionally concentrated on side entering
new environment
bilateral symmetry is an adaptation for movement
Phylum Platyhelminthes - flatworms (planarians, tapeworms and flukes)
18.7
- marine, freshwater, some moist terrestrial, some parasitic - 20,000 species
- bilateral symmetry
- bodies made of tissues and organs (organ level of development)
- 3 embryonic tissue layers : endoderm, mesoderm and ectoderm
- no coelom (body cavity)
- incomplete digestive tract - mouth, branched gut, no anus
- simple brain and nerve cords, sensory cells
Planarians - free-living
Flukes and tapeworms - simpler body design - parasites, nervous and digestive
systems degenerate
Development of coelom (body cavity):
- space for internal organs
- movement and cushioning of organs
- internal circulation
18.3
Phylum Nematoda - nematodes or roundworms, 25,000 species, possibly 500,000
18.8
- marine, freshwater, soil (moist) - very numerous in most habitats
- bilateral symmetry
- 3 tissue layers (ectoderm, mesoderm, endoderm)
- organ systems
- complete digestive tract - (mouth, gut, anus)
- small brain and nerve cord
- pseudocoelom (internal cavity used for internal circulation)
- simple body design, many parasitic
Two main lines of evolution in higher animals
18.3
- distinguished by development of larva, method of forming coelom
1. “Protostomes” (first opening becomes mouth and second opening forms anus,
coelom forms from slit in mesoderm)
- molluscs, segmented worms, arthropods
2. “Deuterostomes” (first opening becomes anus and second opening forms
mouth, coelom forms from pockets off embryonic gut)
- echinoderms, chordates
Phylum Mollusca - gastropods (snails and slugs, chitons), bivalves (clams, oysters, 18.9
mussels), cephalopods (octopuses, squids, chambered nautilus)
93,000 specie
- marine, freshwater, terrestrial
- 3 embryonic tissue layers: endoderm, ectoderm and mesoderm
- body composed of organ systems
- bilateral symmetry, modified in some groups
- true coelom - body cavity formed by mesoderm; but coelom reduced to “heart
chamber”, part or open circulatory system
- protostome larva
- gills connected to circulatory system for gas exchange; gain oxygen, lose carbon
dioxide
- flow-through digestive system;
- complex anterior ganglia nervous system with complex sensory organs in some
(well developed eyes for example)
- body enclosed in mantle; mantle secretes shell in many species
- muscular foot used in movement
- larva similar to segmented worm larva; probably from primitive annelid; lack
segmentation
Phylum Annelida - segmented worms (earthworms, bristle worms, leeches)
- marine, freshwater, moist soil
15,000 species
- bilateral symmetry
- body made of organ systems
- 3 embryonic tissue layers with coelom,
- protostome larva
- complete digestive tract, complete closed circulatory system
- complex anterior ganglia nervous system
- body divided into segments, many organ systems segmented
18.10
Phylum Arthropoda - “jointed” foot - horseshoe crabs, arachnids( scorpions, spiders,
ticks, mites), millipedes and centipedes, crustaceans (lobsters, crayfish, shrimp, crabs,
barnacles, copepods), insects (most numerous, terrestrial)
18.11 -18.12
- very large and diverse group - 80% of all known animal species - 1,000,000+
species described, probably 4 times as many not yet described
- virtually every habitat on earth, most successful animal phylum
- body composed of organ systems
- bilateral symmetry
- 3 embryonic tissues, true coelom formed by mesoderm (but reduced to open
circulatory system)
- protostome larva
- advanced nervous system, complex anterior ganglia and highly developed sense
organs (compound eye)
- jointed appendages - limbs that have joints and can bend
- exoskeleton - tough, waterproof, outer covering - provides support and
protection - made of chitin
- highly specialized body segments with specialized appendages; modular body
design
- respiratory system very efficient for gas exchange allows active life style,
reduced water loss
- insects very successful terrestrial arthropods -air breathing, flight
phylum Echinodermata - “spiny skin” animals - starfish (sea stars), brittle stars, sea
urchins, sand dollars, sea cucumbers
7,000 species
18.13
- marine only
- organ systems
- 3 embryonic tissue layers (endoderm, mesoderm and ectoderm), with true
coelom
- deuterostome larva (bilateral larva)
- adults have special type radial symmetry called pentaradial symmetry (5 sided)
- complete digestive system, simple nervous system (no central ganglia)
- internal skeleton
- water vascular system - system of canals and tube feet filled with water; allows
movement and attachment
phylum Chordata - vertebrates and primitive relatives
50,000 species
18.14, 19
- organ systems
- 3 tissue layers with true coelom
- bilateral symmetry
- deuterostome larva
- all chordates have unique features, present at some time in their lives:
- notochord
- dorsal hollow nerve cord
- pharyngeal gill slits
- postanal tail
-two groups of primitive marine “invertebrate” chordates:
18.14
-tunicates (sea squirts) small marine filter feeders; free swimming larva
with typical chordate features adult “filter-feeding basket”
- lancelets small marine filter feeder that remains as larva, typical
chordate features and segmented muscles along body (typical of
vertebrate larva), most closely related to higher chordates
- eight groups (classes -7 living, 1 extinct) of vertebrate chordates:
19.1
internal skeleton of bone and cartilage including vertebral column;
have well developed cephalization
class Agnatha - “no jaws” - jawless fish
(18.16) 19.2
- 500 mya to 400 mya very common, only a few species alive to present, lampreys
and hagfish
- pharyngeal gill slits, no jaws, funnel mouth for filter feeding
- skeleton made of notochord and cartilage, no bone
- no paired fins (no left and right on side of body); only dorsal and caudal fins
class Placodermi - placoderms , “armored skin”
(18.16) 19.3
- 470 mya to 350 mya - extinct by 350 mya
- paired fins on side of body - greatly increased swimming speed and stability
- jaws - movable flaps from modified pharyngeal gill supports - greatly increased
feeding ability
- gave rise to two other groups of fish
class Chondrichthyes - “cartilagenous fish” - sharks and rays
(18.17) 19.3
- 400 mya from placoderms to present
- almost all marine
- jaws
- paired fins, pectoral and pelvic - rigid, can not rotate
- skeleton made of cartilage
- pharyngeal gill slits open to surface, used for respiration - must swim to move
water over gills
class Osteichthyes - “bony fish”
(18.17) 19.3
- many species, in almost all aquatic habitats - 2/3 of all vertebrate species 27,000 species
- 400 mya from placoderms to present
- paired fins (pectoral and pelvic), can rotate for greater mobility
- jaws
- skeleton made of bone
- pharyngeal gill slits covered by bony plate called the operculum - forms gill
chamber - water can be pumped over gill without swimming
- swim bladder, air sac, can be filled with oxygen from blood or deflated to
regulate buoyancy - (from primitive lung)
lobe-finned fish (coelacanth, lung fish) gave rise to tetrapods (four leg land vertebrates) bones in pelvic and pectoral fins
19.3
(15.1) 15.3 and (18.19) 19.4
During the Devonian period, “the age of fishes” from about 416 mya to 360 mya the
aquatic environment was filled with many species of predatory fishes. The terrestrial
environments (land) contained plants and invertebrates but no large predators or
vertebrates.
Also the Devonian period was a time of fluctuating climate with frequent drying and
flooding of shallow lakes, bays and rivers. Some fish species, especially the lobe-finned
fish, were able to survive and take advantage of these conditions of shallow stagnant
habitats because they had 1)strong well supported paired fins that allowed them to move
in complex environment of ponds and 2) small lungs connected to their pharynx that
allowed them to gulp air and breath.
Terrestrial environment offered advantages: food, higher oxygen, reduced competition
and predation
But also posed problems: body support and movement, drying, reproduction, sense
organs in air.
The lobed-finned fish gave rise to tetrapods (four-leg) - early amphibians in
Carboniferous period, which gave rise to other land vertebrates.
class Amphibia - salamanders, frogs and toads, caecilians
(18.18) 19.5
- 350 mya to present from lobe-finned fish
- first terrestrial vertebrates but still dependent on aquatic environment
- thrived during Carboniferous period 360 to about 300 mya
- gas exchange though moist skin and small lungs
- aquatic egg
- legs to side of body, not good runners
class Reptilia - turtles, snakes and lizards, crocodiles, dinosaurs (extinct), birds
(18.19) 19.6
- 300 mya to present, from amphibians
- Permian period (300 to 250 mya) was much drier than Carboniferous
- adapted to dry terrestrial environment:
- gas exchange in lungs
- skin covered with waterproofing epidermal scales made of keratin
- legs more under body for better movement on land
- amniotic egg, can be laid on land away from water (with specialized
tissues)
- poikilotherms (body temp. changes) and ectotherms (heat from outside)
birds
(18.20) 19.7
- 150 mya from theropod dinosaurs, most species 65 mya to present
- specialized for flight - light weight hollow bones, no teeth, reduced tail vertebra
- feathers, made of keratin, make good flight surface and good insulation
- flight requires high metabolism - efficient lungs and cardiovascular system
- homeothermic (constant high temp) and endothermic (internal heat)
(requires much more food - 10 times food required for reptile)
The amniotic, or shelled egg, is formed from membranes that grow from the embryo and
a hard shell produced by the mother:
19.6
- yolk sac that stores food
(27.16F)
- amnion that forms a fluid filled sac for the embryo to live in
- allantois that forms a sac to store nitrogenous waste (urine)
- chorion - encloses the other membranes, prevents drying, allowing oxygen to
enter
The mother adds a hard shell over the membranes in her oviduct. The reptiles, therefore,
had to have internal fertilization.
class Mammalia - mammals
(18.21) 19.8
-200 mya from stem-reptiles, most species 65 mya to present
- high metabolic rate, homeothermic and endothermic (nasal bones)
- hair, made of keratin, provides insulation
- efficient lungs and cardiovascular system
- amniotic egg, many develop inside mother’s body and via placenta in some
- long parental care, mammary glands to produce milk to nourish young
- large brain
- differentiation of teeth
Three groups of mammals are alive today:
- monotremes (duct-billed platypus and echidna) - only in Australia area
- lay shelled amniotic egg, poorly developed mammary glands- 3 species today
- marsupials (pouched mammals - opossums, kangaroos) mostly in Australia area
- born very immature and develop in pouch on mother’s abdomen
- evolved in southern hemisphere 100 mya, 240 species alive today
- eutherians (placental mammals) world wide except Australia
- young develop in mother’s uterus, exchange oxygen, food, carbon dioxide and
other waste with mother’s blood via placenta
- evolved in northern hemisphere 75 mya, 4,000+ sp
Primates - placental mammals - lorises and lemurs, tarsiers (35 species), anthropoids
(old and new world monkeys, apes)
(19.1) 19.9
-evolved about 65 mya. from small arboreal tree shrews, into arboreal (treedwelling) habitat
(this is an example of adaptive radiation into adaptive zone - a new habitat)
Primates adaptations for an arboreal environment:
- limber shoulder and hip joints increase climbing ability
- grasping hand with opposable thumb, flexible for manipulation, sensitive
- forward directed eyes, stereoscopic vision for depth perception; probably color
vision and visual acuity
- large brain for hand-eye coordination
- long period of parental care, learning
Anthropoids - from prosimians ancestor about 50 mya
- monkeys from anthropoid ancestor 30 mya
- new world monkeys (South America) - prehensile tail, wide nostrils open to the
side
-old world monkeys (Africa, Asia, Indonesia) - no prehensile tail, narrow nostrils
open downward
hominoids - from anthropoid ancestors 20 to 25 mya
gibbons, orangutans, gorillas, chimpanzees, humans
- lack tail
- larger brain than other primates compared to body size
hominids (human-like primates) 20 species, 1 living
- from hominoid ancestors 5 - 7 mya
- bipedal walking (upright on 2 legs)
- larger brain, capable of symbolic thought and speech
- long parental care
(19.2) 19.10
(19.3 - .4) 19.11 -116
- tropical rain forest drying to savanna grassland as Africa went through long
drying period - adapting to more terrestrial life
*Read module (19.9) 19.13 and explain how bipedal stance, brain size and parental care
are related.
- Australopithecus - several species of early humans - had bipedal (upright
walking on 2 legs), smaller brain; all extinct by 1.4 mya
- all in Africa
- Homo - several species - earliest fossils 2.4 mya - larger brain than Australopithecus and simple stone tools, home sites in
early species.
- later species with increasingly larger brain and more complex tool,
social structure
- spread out of Africa to Asia and Europe
- Homo sapiens (archaic) - 200,000 ya in Africa, spread to Europe and Asia larger brain, more complex social organizations
- Homo sapiens (modern) - 100,000 ya in Africa, spread throughout world
50,000 ya
- symbolic language, abstract rituals cultural development (cultural
evolution)
Requires prolong growth of skull and brain after birth, which requires long periods of
parental care. This allows culture to develop (learning experiences of earlier generations,
based on having symbolic language)
- cultural evolution is very plastic, can adapt technology quickly (biological
evolution, which requires genetic change, is slow)
- probably little biological change in this time period
*Read module (19.8) 19.16 and explain the importance of the FOXP2 gene to modern
humans.
Biology 1407 Exam 2 Review
Describe how multicellular organisms may have evolved.
List the distinguishing characteristics for Kingdom Animalia. Tell what each of these
characteristics is or what it means.
List several major trends within the evolutionary history of this group.
List the nine major groups of animals (phyla) discussed in class and list the following for
each:
type symmetry
level of development (specialized cells, tissues, organs)
number of tissue layers
presence of coelom
type digestive system
type larva
special features that are characteristic of each group
Tell what each of the terms used above is and why it is important (for example what is a
coelom and why is it important to animals that have it?).
Define the phylum Chordata listing their unique traits that they all share.
List the groups (invertebrate chordates, 8 classes) described in class. Give the key
features of each group and tell what these features do and why they are important.
Describe what structures the key features evolved from (legs, lungs, jaws, swim bladders,
feathers, hair, placenta, etc.)
List the parts of the amniotic egg and tell what each part does.
Where and when did the earliest primates evolve and what were their key adaptations to
this environment?
What was the first important trait that separated hominids (humans and their direct
ancestors) from other primates?
What environmental setting do biologists think this occurred in?
What important trait separates later hominids from earlier hominids?
Describe cultural development and the life style that lead to culture.