Download unit 1: introduction to biology

SAN DIEGO MESA COLLEGE
SCHOOL OF NATURAL SCIENCES
General Biology Lecture (BIOL107); Instructor: Elmar Schmid, Ph.D.
Chapter 18: ANIMAL KINGDOM & ANIMAL LIFE CYCLES
- Part II -
5. Earthworms (Phylum: ANNELIDA)
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the phylum Annelidae comprises the segmented worms (such as the earthworm)
about 15,000 species are known
 they differ in length from < 1mm till up to 3 meters (!!) (= Australian earthworm)

annelids were the first animals which showed for the first time a unique body feature
called segmentation (see Figure below) the development of segmented bodies
allowed the formation of specialized functions in different segments
 the body is along its axis subdivided into a series of repeated
functional body parts
 they consist of strings of almost identical body segments
 segmentation evolved as an evolutionary adaptation to movement
and increased motility
 segmentation gives annelidae a high flexibility and enabled novel
complex animal functions such as flying, perching and crawling

they have an enlarged “true” coelom to accommodate more complex internal
organs
 as a consequence of segmentation, the coelom is partitioned by walls
 in many species some of the anterior segments are fused and build
other more complex body features like a thorax or a head region

they have a closed circulatory system with blood vessels running the length of the
body and branching into every segment
 closed circulatory systems are more efficient than open ones for
moving materials within a body
 Earthworms have red blood which is moved by a dorsal blood vessel
and pumped by five pairs of hearts to a ventral vessel.
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they evolved a complete nervous system, which consists of a brain connected to a
ventral solid nerve cord, with a ganglion in each segment.
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annelids have a complete digestive system that includes a pharynx, stomach,
intestine, and accessory glands
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earthworms have a primitive excretory system, which consists of coiled nephridia
tubules in each segment
 it has two openings: one is a ciliated funnel that collects coelomic
fluid; the other is an exit in the body wall
 the coiled nephridia tubule allows removal of liquid waste materials from
blood vessels
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SAN DIEGO MESA COLLEGE
SCHOOL OF NATURAL SCIENCES
General Biology Lecture (BIOL107); Instructor: Elmar Schmid, Ph.D.
Overview of the animal kingdom
(Part II)
Coelomata
- have a true coelom
Embryonic
development
Protostomes
Deuterostomes
- blastopore becomes
the mouth
- coelom develops
from mesoderm
- determinate development
- blastopore becomes
the anus
- coelom develops
from alimentary canal
- indeterminate development
Endoskeleton
Segmentation
Mollusca
Echinodermat
(Mollusks)
> 100,000 species
- open circ. System
- ganglia, nerve cords
- some with eyes
Annelida
- 15,000 species
- closed circ. System
- nephridia
- brain, nerve cords
Chordata
- 6,000 species
- radial symmetry
- nerve cords
(Chordates
Vertebrata
Tunicata
Lancelets
> 50,000 species
- vertebral column
- skull, complex brains
- organs
- hinged jaws
Exoskeleton
Arthropoda
Pisces
Amphibia
(= Fishes)
- 4,000 species - 6,000
Reptili
Aves
(= Birds)
Mammalia
- 5,000 species
- 9,000 species
- 30,000 species
Homo sapiens
Graphic©E.Schmid/2001
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SAN DIEGO MESA COLLEGE
SCHOOL OF NATURAL SCIENCES
General Biology Lecture (BIOL107); Instructor: Elmar Schmid, Ph.D.
Life cycle and reproduction
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Earthworms are hermaphroditic, they have both, testes with seminal vesicles, and
ovaries with seminal receptacles
mating involves the worms lying parallel to each other facing opposite directions and
exchanging sperm
each worm possesses a clitellum that then secretes a mucus, protecting sperm and
eggs from drying out
embryonic development lacks a larval stage
Anatomy of an Earthworm (Phylum: ANNELIDAE)
Cross section of a typical segment
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SAN DIEGO MESA COLLEGE
SCHOOL OF NATURAL SCIENCES
General Biology Lecture (BIOL107); Instructor: Elmar Schmid, Ph.D.

3 large classes of annelids are known
11.. E
Eaarrtthhw
woorrm
mss ((ccllaassss:: O
Olliiggoocchhaaeettaa))
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the class Oligochaeta includes the earthworms, which thrive in moist soil
 there a moist body wall facilitates gas exchange
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Earthworms are scavengers that extract organic remains and nutrients from the
ingested soil
 they play an important ecological role in soil aerating and improvement
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Earthworms have poorly developed heads and parapodia; it is the so-called setae (=
bristles) which protrude in clusters directly from their body and which support
locomotion
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Earthworms move by coordinated movement of the body muscles and assistance of
their setae
 when longitudinal muscles contract, segments bulge and setae
protrude and anchor into the soil
 circular muscles contract, causing the worm to lengthen, setae are
withdrawn and the segment moves forward.
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e.g. LLuum
mbbrriiccuuss tteerrrreessttrriiaannss
 has a small brain which sits above the mouth region
 has a tube-like heart with ring-like blood vessel extensions
 has a ventral nerve chord which runs from the anterior mouth region
to the posterior (tail) end
22.. P
Poollyycchhaaeetteess ((ccllaassss:: P
Poollyycchhaaeettaa))
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the class Polychaeta contains marine species which mostly live on the ocean floors
 most marine species live in tubes which are made of a sticky protein
secreted from special mouth glands
 they trap surrounding food particles by extended feathery appendages
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they possess so-called parapodia and setae
 parapodia are paddlelike appendages which are used in swimming
and which also serve as respiratory organs

e.g. the ssaannddw
woorrm
m, the predatory ccllaam
mw
woorrm
m ““N
Neerreeiiss””
33.. LLeeeecchheess ((ccllaassss:: H
Hiirruuddiinneeaa))

most species inhabit fresh water, but a few are marine or terrestrial
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SAN DIEGO MESA COLLEGE
SCHOOL OF NATURAL SCIENCES
General Biology Lecture (BIOL107); Instructor: Elmar Schmid, Ph.D.
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most leeches are fluid feeders, but some live as free-living carnivores, which eat
snails and small insects
the fluid feeders attach to mammals and suck their blood with the help of special
sucking devices in their mouth region
 leeches possess a small anterior sucker around the mouth and a larger posterior
sucker
the bloodsuckers secrete saliva, which contains a strong anaesthetic compound and
anticoagulant protein called Hirudin
 Hirudin keeps the blood from coagulating
 therefore leeches were commonly used in traditional medicine to
"bleed" the patient and to treat blood-borne diseases
 today, the anti-blood clotting activity of genetically engineered Hirudin
is widely used in medicinal treatment of humans which bear a high
risk for heart strokes
6. Phylum: ARTHROPODA
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the phylum Arthropoda contains animals with segmented appendages on their
body segments
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arthropods occupy every habitat and populate our planet in incredibly high numbers;
they are in many respects the most successful animal group on Earth
 biologists conservatively estimated over 1 million species of living
arthropods
 it is estimated that currently about one billion billion (= 10 18 !!)
arthropod individuals are populating our planet
 it is assumed that many more undiscovered and not classified
species are living in the vast tropical rain forests on our planet
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some scientists believe, that arthropods evolved from a segmented annelid
ancestor, which lived in the Cambrian era some 550 million years ago
 based on molecular genetic data, however, others assume that they
evolved from an earlier existing bilateral animal
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arthropods owe their evolutionary success a series of unique body features:
1. Exoskeleton
 the soft body parts are covered by a so-called exoskeleton, which is
made of chitin
 it has protective function and provides attachment points for muscles
and tendons
 in order to grow, arthropods periodically shed off their old skeleton
and replace it by a newly synthesized one; this process is called
molting
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SAN DIEGO MESA COLLEGE
SCHOOL OF NATURAL SCIENCES
General Biology Lecture (BIOL107); Instructor: Elmar Schmid, Ph.D.
2. Jointed appendages (‘walking legs’)
 arthropods have a pair of appendages on each body segment
 they are used for walking, swimming, reproduction, mating, etc.
3. Complex nervous system
 it consists of a brain, which is connected to a ventral solid nerve cord
 the head bears various sensory organs, e.g. compound eyes, which
consists of many complete visual units, each of which collects light
independently
4. Unique respiratory system
 marine arthropods use gills, which are composed of a vascularized, thinwalled tissue specialized for gas exchange
 terrestrial forms have either book lungs, which are body invaginations
(e.g., spiders) or tracheae, which are air tubes that serve as ways to
deliver oxygen directly to cells. (e.g., insects)
5. Metamorphosis
 metamorphosis is drastic change in form and physiology of an
arthropod animal, that occurs as an immature stage becomes an adult
 the immature, larval stage eats food and lives in environments
different from the adult
 this reduces competition between immature and adults of a species
and allows more members of the species to exist at the same time
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arthropods show distinct groups of segments and their body is divided into three
major regions
1. Head
2. Thorax
3. Abdomen
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 anterior (front)
 middle section
 posterior (“tail” region)
some species evolved a so-called cephalothorax (see section below)
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SAN DIEGO MESA COLLEGE
SCHOOL OF NATURAL SCIENCES
General Biology Lecture (BIOL107); Instructor: Elmar Schmid, Ph.D.
Anatomy of typical Arthropods (Phylum: ARTHROPODA)
(Subphylum: CRUSTACEA)
(Subphylum: UNIRAMA)
(Class: Insecta)
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due to their great diversity of appendages, lifestyles, and other features, arthropods
are usually separated into several subphyla
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3 subphyla including 7 major classes are known:
11.. S
Suubbpphhyylluum
m:: C
Chheelliicceerraattaa
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SAN DIEGO MESA COLLEGE
SCHOOL OF NATURAL SCIENCES
General Biology Lecture (BIOL107); Instructor: Elmar Schmid, Ph.D.
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this subphylum contains the horseshoe crabs, spiders, scorpions, ticks and
mites
they are named after their first pair of appendages, which are called chelicerae
 chelicerae are appendages that function as feeding organs
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the second pair are the pedipalps, and the next four pairs make up the walking legs
 pedipalps are feeding or sensory in function; although in scorpions,
they are large pincers
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all appendages attach to a cephalothorax, which is a fusion of the head and
thoracic regions
 the head lacks antennae, mandibles, or maxillae appendages
1.1.
Horseshoe crabs (Class: Merostomata)
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the class Merostomata contains the extinct "sea scorpions" (or eurypterids) and the
so-called “living fossils” horseshoe crabs
 the Eurypterids are extinct, but were important members of the
Earth’s faunas 200-500 million years ago during the Paleozoic Era
 some species were reaching a length of over 10 feet (!!)

of the ancient group of horseshoe crabs only 5 species still exists today
 LLiim
muulluuss, is a prominent member of this class
 it has a large shield that covers the cephalothorax
 the compound eyes are reduced and the second pair of appendages,
the pedipalps, resemble walking legs
 gas exchange happens via so-called book gills
1.2.
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Spiders, scorpions, mites and ticks (Class: Arachnida)
the class Arachnida includes over 60,000 described species
all species are terrestrial
they have a cephalothorax, covered with a carapace-like shield
the abdomen may be segmented or unsegmented
appendages on the abdomen are absent or modified
respiration occurs via tracheae or book lungs
S
Sccoorrppiioonnss
 from fossils findings we know, that the scorpions are the oldest terrestrial arthropods
 they are nocturnal hunters whose prey are herbivorous arthropods
 they have a poisonous stinger at their abdomen, which serves to paralyze the prey
and has protective function
S
Sppiiddeerrss
 spiders have numerous simple eyes rather than compound eyes
 the chelicerae are modified as fangs with ducts from poison glands
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SAN DIEGO MESA COLLEGE
SCHOOL OF NATURAL SCIENCES
General Biology Lecture (BIOL107); Instructor: Elmar Schmid, Ph.D.

the abdomen has silk glands used to spin a web to trap prey
 the gland produces an air-hardening, silk-like polymer
 the breathe via book lungs, which are formed by invaginations of the body wall
TTiicckkss
 ticks are parasites that suck blood of their host animal or sometimes humans
 since some ticks are the host for certain viruses they can transmit diseases to
humans, such as Lyme disease or tick encephalitis
22.. S
Suubbpphhyylluum
m:: C
Crruussttaacceeaa
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the subphylum Crustacea contains 30,000 mostly marine species, and only a few
species live in freshwater
typical crustacean are lobsters, crabs, crayfish, shrimp, copepods, barnacles
crustaceans possess two pairs of antennae, a pair of mandibles, a pair of
compound eyes and two pair of maxillae on their heads
they have a pair of appendages on each body segment
crustaceans use gills for gas exchange
22..11..
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LLoobbsstteerrss,, ccrraabbss,, ccrraayyffiisshh,, eettcc.. ((C
Cllaassss:: M
Maallaaccoossttrraaccaa))
the class Malacostraca is the largest taxonomic class of Crustaceans with over
20,000 primarily marine species
 only some members of this class are freshwater or occupy diverse
terrestrial habitats
typical malacostracans include also sowbugs, krill, and the many kinds of shrimp,
crabs, and crayfish
they typically possess a body with eight thoracic and six abdominal body segments,
each bearing a pair of appendages
this class of crustacean contains a number of economically significant species, such
as edible lobsters, shrimp, crayfish and crabs
many members of this class of crustacean contribute to plankton and play an
immensely important role in the marine food chain
33.. S
Suubbpphhyylluum
m:: U
Unniirraam
maa
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this subphylum contains arthropods that have unbranched appendages and many
abdominal segments
appendages in the head region include paired antennae and mandibles, and also
two pairs of maxillae
gas exchange is by means of tracheae and spiracles
this subphylum include the class of millipedes, centipedes, and insects
1. Millipedes (Class: Diplopoda)
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this class contains some 8000 species
the bodies of members of this class are made up of numerous segments
millipedes lack poisonous fangs and do not bite
9
SAN DIEGO MESA COLLEGE
SCHOOL OF NATURAL SCIENCES
General Biology Lecture (BIOL107); Instructor: Elmar Schmid, Ph.D.
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in case of danger, they roll into a defensive ball and produce poisonous or foulsmelling substances
 most millipedes are herbivores or scavengers
2. Centipedes (Class: Chilopoda)
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most centipedes are small, but a few can attain a length of up to 10 inches (25 cm)
they have a worm-like body, which is divided into multiple, identically looking
segments; this feature makes them look like annelids
 but they have one pair of short, jointed legs per body segment, which
clearly characterizes them as arthropods
 a centiped body can be made up to 177 flattened segments
with the exception of the segment behind the head and the last body segment, each
segment has a single pair of short appendages (legs)
the appendages of the first body segment have been modified to form large,
poisonous fangs
 they are usually used to capture prey, e.g. cockroaches and flies
 but the bite of a large centipede can become dangerous to a small
child
3. Insects (Class: Insecta)
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insects are the largest group of arthropods, with probably over one million
identified and named species
 but probably twice as much exists in the largely unexplored tropical
rain forests on our planet which haven’t classified yet!
insects live in almost all terrestrial and freshwater habitats
insects inhabited land already 400 million years ago when giant dragonflies
populated the vast swamps of the Carbonic era
many insects have thoracic appendages modified for flight, called wings
many insects are important pollinators of flowering plants, other, herbivorous insects
cause serious damage to agricultural crops or transmit fatal diseases, such as
malaria, encephalitis, Dengue Fever, etc.
the fruit fly D
Drroossoopphhiillaa m
meellaannooggaasstteerr plays an important role in modern genetic
research to study inheritance patterns and the role of genes in animal development
insects have a complete digestive system
gas exchange happens with the help of a tracheal system, with external openings
called spiracles
 the spiracles divide into finely branched tubules that carry gases
directly to metabolizing tissues
 aquatic forms exchange gases through the body wall or via gills
they have an excretory system, which is primarily formed by the so-called
Malpighian tubules
they have a complex nervous system, including a number of ganglia and a ventral,
double nerve cord
they possess complex and acute sense organs
 in addition to ocelli and compound eyes, some insects are quite
sensitive to sounds
10
SAN DIEGO MESA COLLEGE
SCHOOL OF NATURAL SCIENCES
General Biology Lecture (BIOL107); Instructor: Elmar Schmid, Ph.D.
 many insects have outstanding chemo-receptive abilities and are able
to sense and respond to sex hormones of a distant mating partner

insects have a characteristic three parted body, consisting of:
1. Head
 bears a pair of sensory antennae and a pair of
so-called facetted or compound eyes
 bears also several pairs of mouth parts which differ remarkably between
the different species and are highly adapted devices for biting, chewing,
sucking or lapping up
2. Thorax
 a typical insect has three pairs of legs extending out
from the ventral part
 has two pairs of dorsal attached wings; a pair of
forewings and one pair of hindwings
3. Abdomen
 the segmented abdomen of some species has a stinger
apparatus and bears special glands
 these glands produce and secrete an arsenal of
poisonous or irritating compounds
 it is highly contractible which is important for pumping air into the insect’s
tracheal system body via abdominal openings
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almost all insects are flying organisms
many insects undergo metamorphosis during their development
 they change their morphological (= body) appearance
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2 types of metamorphosis are known
1. Incomplete metamorphosis
 the young organism resembles the adult insect, but is
smaller
2. Complete metamorphosis
 the younger organism, which is called a larvae, looks very
different than the adult insect
 the larvae usually inhabits a different environment than
the adult animal
 e.g. aquatic larvae of the dragonfly, the maggots of flies or
the caterpillar of butterflies

the huge variety of the class insecta is further classified into different so-called
orders
11
SAN DIEGO MESA COLLEGE
SCHOOL OF NATURAL SCIENCES
General Biology Lecture (BIOL107); Instructor: Elmar Schmid, Ph.D.
A. Orthoptera
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about 30,000 species belong to this order of insecta
e.g. grasshoppers, crickets, locusts, cockroaches, praying mantis
they have biting and chewing mouth parts
most are herbivorous or live from organic matter
B. Odonata
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about 5,000 species are known
e.g. dragonfly, damselfly
they have biting mouth parts
they are carnivorous insect; especially the larvae, which live and hunt in fresh water
terrains
they have two pairs of similar transparent wings
C. Hemiptera (or “true bugs”)
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about 55,000 species are known
e.g. bed bugs, plant bugs, stink bugs and water striders
they have piercing, sucking mouth parts
they are herbivorous and suck the sap of plants
they have two pairs of different wings; forewings are thickened
D. Coleoptera (“Beetles”)
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about 500,000 species known (30,000 in the U.S.)
e.g. lady bug
they have biting and chewing mouth parts
this order comprises carnivores, herbivores and omnivores
they have two pairs of wings; one pair of mostly colorful, thick and hardened forewings that serve as a protective cover, one pair of transparent hind wings which are
used for flying
E. Lepidoptera
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about 140,000 species are known
e.g. moths, butterflies
they have a long, tube-like mouth part which is spirally coiled under the head region
 it is stretched out to reach hidden nectar sources in deep narrow
flower heads
 the food is ‘straw-like’ sucked up
they have two pairs of mostly colorful wings both for flying which are covered with
tiny scales
12
SAN DIEGO MESA COLLEGE
SCHOOL OF NATURAL SCIENCES
General Biology Lecture (BIOL107); Instructor: Elmar Schmid, Ph.D.

many butterflies developed strict mutual partnerships with certain plants in a process
called co-evolution
F. Diptera
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about 120,000 species are known
e.g. flies, houseflies, gnats, mosquitoes
they have piercing and sucking mouth parts
 female mosquitoes suck blood through the skin of their host
they have a single pair of transparent wings and one rudimented pair called halteres
many diptera, e.g. sand fly or Tse-tse fly, carry bacteria or protists over to other
animals hosts; they are potential transmitters of serious diseases, e.g. sleeping
disorder or malaria
flies digest their food outside of their body by secreting digestive enzymes; the
nutrients are lapped up and absorbed in the digestive tract
G. Hymenoptera
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about 110,000 species are known
e.g. ants, bees, wasps, hornisses
they have chewing and sucking mouth parts
this order comprises herbivores and carnivores
they have two pairs of transparent wings, which are both used during the flight; the
smaller hind-wings are hooked to the rear of the fore-wings which enables the
outstanding flight performances of these insects
the thorax and the abdomen are separated by a characteristic waist
many hymenoptera display complex behavioral patterns, including social
organization and hive construction
the honey bee communicates with their inmates by an intricate body language (=
“bee dance”)
D
Deeuutteerroossttoom
mee//P
Prroottoossttoom
mee aanniim
maallss
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the two other important branches of the so-called Coelerata are the phyla
echinodermata and vertebrata; both are the only phyla which belong to the group of
so-called Deuterostomes
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the Deuterostomes show unique features during early embryonic development,
which separates these two phyla from the rest of the Coelomates (= Annelids,
Mollusks and Arthropods), which are also called Protostomes
13
SAN DIEGO MESA COLLEGE
SCHOOL OF NATURAL SCIENCES
General Biology Lecture (BIOL107); Instructor: Elmar Schmid, Ph.D.
Comparison of the embryonic features of
the Deuterostomes and Protostomes
D
Deeuutteerroossttoom
meess
P
Prroottoossttoom
meess
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the first opening in the blastocyst
becomes the later anus; the mouth
forms at the other end of the embryo
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the first opening in the blastocyst
becomes the later mouth
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the embryonic cells show radial
cleavage during embryonic cell
division; the daughter cells sit on top of
previous cells.
the fate of cells is indeterminate; if
embryonic cells are separated, each
one develops into a complete organism
includes the animal phyla
echinodermata and vertebrata
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the embryonic cells show spiral
cleavage; the daughter cells are
arranged side-by-side
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the embryonic cells are determinate;
separated embryonic cells don’t
develop into a mature animal
includes the Annelids, Mollusks and
Arthropods
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before switching over to the phylum chordata and its major sub-phylum vertebrata
we will look at an unique evolutionary branch of (deuterostomic) animals called
Echinodermata
7. Echinoderms (Phylum: ECHINODERMATA)
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it is the only phylum of complex animals which (evolutionary) returned to radial
symmetry
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there are 6000 species of echinoderms; all living species are marine
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the phylum Echinodermata includes the sea urchins, sea stars, sea cucumbers,
and starfish
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they lack typical body segmentation
 most adults are radially symmetrical
 the larval stage is bilateral symmetrical
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they have a hard internal skeleton, called endoskeleton, which consists of calcified
plates bearing pointed spines
14
SAN DIEGO MESA COLLEGE
SCHOOL OF NATURAL SCIENCES
General Biology Lecture (BIOL107); Instructor: Elmar Schmid, Ph.D.
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they have a water vascular system, which is a network of water-filled channels; it
powers their multitude of tube feet
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adult echinoderms have no brain
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they are carnivores (eat oysters and clams) which perform external digestion
 digestion occurs within the prey by pushing the stomach out of the
own body and into the prey’s soft tissue
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echinoderms lack a complex respiratory and excretory system
 it is the fluids within the coelomic cavity which distributes substances
and gases; cilia on the peritoneum which line the coelom keep the
coelomic fluid moving
 gas exchange occurs across the skin gills and tube feet
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they have a strong capacity to regenerate damage or lost body parts
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sea stars show both, sexual and asexual reproduction
 if the body is fragmented, each fragment can regenerate a whole
animal
 in sexual reproduction, they spawn and release either eggs or sperm
at the same time
 after fertilization, a bilateral larvae develops via a intermediary
Gastrula stage
 the larvae undergoes a metamorphosis to become a radially
symmetrical adult
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despite their different body features they belong to the kingdom animals because the
digestive tract and the coelom develops from a similar Gastrula stage as in animals
15
SAN DIEGO MESA COLLEGE
SCHOOL OF NATURAL SCIENCES
General Biology Lecture (BIOL107); Instructor: Elmar Schmid, Ph.D.
Anatomy of an adult sea star (Phylum: Echinodermata)
C
Crroossss sseeccttiioonn tthhrroouugghh aann aarrm
m ooff aa sseeaa ssttaarr
8. Animals with chords (Phylum: CHORDATA)

the Phylum Chordata includes about 45,000 species that occupy nearly all
environments

the unifying body feature of all chordates is a characteristic tube-like structure, the
so-called chord, which early develops within their bodies in their bodies
 all chordates at some time during their life history develop a chord
 the chords are the result of massive cell motions and in-foldings of
the ectodermal layer early during embryogenesis
16
SAN DIEGO MESA COLLEGE
SCHOOL OF NATURAL SCIENCES
General Biology Lecture (BIOL107); Instructor: Elmar Schmid, Ph.D.

4 hallmark features which are seen only during embryonic development in
vertebrate chordates; not all chordates are vertebrates
1. they have a dorsal hollow nerve chord
2. they have a notochord
 the notochord is a long rod-shaped cell structure which is located
between the nerve cord and the central digestive tract
 it provides support and is replaced by the vertebral column in
vertebrates
3. they have 2 pharyngeal gill pouches
 openings that are located left and right-sided in the head region,
which function in feeding and/or gas exchange
 the pharyngeal gill pouches of invertebrate chordates, fish, and
amphibian larvae, become functioning gills
 the pouches in terrestrial vertebrates become modified for various
purposes
 in humans, the first pouches become the auditory tubes, the
second become tonsils, and the third and fourth pairs become the
thymus and parathyroid glands
4. they show a typical post-anal tail

the evolutionary origin of chordates remains a mystery, although biochemistry and
comparative embryology indicate a common ancestry of echinoderms and chordates

the most diverse group of chordata are called vertebrates, it describes animals with
a characteristic segmented backbone

the two other chordate groups which do not have a backbone are the:
11.. TTuunniiccaatteess ((S
Suubbpphhyylluum
m:: U
Urroocchhoorrddaattaa))




tunicates are marine animals
they often inhabit coral reefs
adult animals do not have a notochord, no nerve chord and no tail, but are equipped
with huge gills
the tadpole-like larvae, however, exhibit all 4 chordate hallmarks; they eat tiny
organic particles which enter the body through a mouth-like opening
22.. LLaanncceelleettss ((S
Suubbpphhyylluum
m:: C
Ceepphhaalloocchhoorrddaattaa))

are marine chordates which show all chordate characteristics and resemble the
tunicate larvae
17
SAN DIEGO MESA COLLEGE
SCHOOL OF NATURAL SCIENCES
General Biology Lecture (BIOL107); Instructor: Elmar Schmid, Ph.D.



they inhabit shallow coastal waters, where they lie partly buried in sandy substrates
and filter feed
 their gill apparatus traps fine food particles
they have segmented muscles and their dorsal hollow nerve cord has periodic
branches
they are the closest living relatives of all vertebrates (including us humans)
Anatomy of the lancelet “Amphioxus” (Phylum: Chordata)
Illustration of several Lampreys (Phylum: Chordata; Subphylum: Vertebrata)
3. V
Veerrtteebbrraatteess ((S
Suubbpphhyylluum
m:: V
Veerrtteebbrraattaa))

vertebrates are animals with backbones
 the embryonic notochord is replaced by a vertebral column in the adult
 the vertebral column is made of individual hard segments, called
vertebrae, which surround the dorsal hollow nerve cord

the subphylum Vertebrata consists of about 43,700 species
18
SAN DIEGO MESA COLLEGE
SCHOOL OF NATURAL SCIENCES
General Biology Lecture (BIOL107); Instructor: Elmar Schmid, Ph.D.

vertebrates exhibit all three of the chordate characteristics at some point during their
lives

vertebrates have distinguished body features
1. a skull
 is made of a calcified cell material called bone
 bone is a dead, porous and calcified biological structure
secreted by special body cells called osteoblasts and osteoclasts
 it encloses and protects the brain
2. a backbone (= vertebral column)
 is composed of a series of bony, hollow units called vertebrae
 it encloses the main parts of the nervous system, the nerve cord
 the vertebral column is evidence that vertebrates are
segmented animals
3. an endoskeleton
 made from a combination of hard, calcified bone and soft,
flexible cartilage
 the vertebrate skeleton is living tissue that grows as the animal develops
4. hinged jaws
 formed by two skeletal bone parts, which are hold
together by a hinge made of cartilage
 evolved from gill-supporting skeletal rods in the mouth
region of a hypothetical ancestor vertebrate

the oldest fossil of a jawed vertebrate is 450 million years old; the evolution of jaws
gave vertebrates a huge advantage and enabled them to catch and eat a wide
variety of large prey (with a high nutritional value)

vertebrates are subdivided into 4 different orders
11.. FFiisshheess ((O
Orrddeerr:: P
Piisscceess))




the first vertebrates were fish-like
fishes are aquatic, gill-breathing vertebrates that usually have fins and skin covered
with scales
the larval form of a modern-day llaam
mpprreeyy, which looks like a lancelet, may resemble
the first vertebrates
small, jawless and finless O
Ossttrraaccooddeerrm
mss were the earliest vertebrates
 they were filter feeders, but probably were also able to move water
through their gills by muscular action (see Image below)
 ostracoderms, which are extinct today, have been found as fossils
from the Cambrian through Devonian periods
19
SAN DIEGO MESA COLLEGE
SCHOOL OF NATURAL SCIENCES
General Biology Lecture (BIOL107); Instructor: Elmar Schmid, Ph.D.


the first jawed vertebrates existed already more than 400 million years ago in form of
jawed fishes called P
Pllaaccooddeerrm
mss
 the extinct group of Placoderms were armored with heavy plates and
had strong jaws
30,000 – 45,000 species of fishes are known today
Reconstructed image of Ostracoderm fishes of the Ordovician period
(505 – 438 million years ago)
20
SAN DIEGO MESA COLLEGE
SCHOOL OF NATURAL SCIENCES
General Biology Lecture (BIOL107); Instructor: Elmar Schmid, Ph.D.
Reconstruction of Arandaspis prionotolepis
 one of the oldest known vertebrate animal
- Ostracoderm (= shell skin) fish
- jaw-less, lacked dorsal fins
- bone-like plates made of apatite


all modern fishes have hinged jaws and an organ called gills, with which fishes are
able to extract molecular oxygen from the surrounding water
they have developed fore- and hind fins
21
SAN DIEGO MESA COLLEGE
SCHOOL OF NATURAL SCIENCES
General Biology Lecture (BIOL107); Instructor: Elmar Schmid, Ph.D.

almost all fish are carnivores

2 major groups exist today
I. Cartilaginous fishes (Class: Chondrichthyes)






IIII..









the class Chondrichthyes contains approximately 850 species of skates, rays,
and sharks
they are characterized by pronounced jaws, lots of teeth, paired fins, and a
cartilage endoskeleton
they appeared first during the Devonian period and expanded in diversity during
the Carboniferous and Permian era
 during the great extinction at the end of the Permian they nearly
disappeared completely
 cartilaginous fish still exist today and play an important role in the
marine ecosysstem
they have five to seven gill slits on both sides of the pharynx, and lack the gill
covers found in bony fish
cartilaginous fishes, e.g. sharks, have a skeleton made of flexible cartilage
sshhaarrkkss are extremely fast swimming marine predators that evolved highly
developed senses and strong teeth jaws
 the head bears electro-sensors which enables them to
detect weak electrical fields caused by muscle
contractions of prey
 they also have a lateral line system which contains a row
of sensory organs
B
Boonnyy ffiisshheess ((C
Cllaassss:: O
Osstteeiicchhtthhyyeess))
the class Osteichthyes comprises about 29,000 species of bony fish, which are
found both, in marine and freshwater
prominent members of this class are trout, bass, perch, tuna
they have a stiff, bony skeleton, reinforced by calcium
most species in this class are ray-finned with thin, bony rays supporting the fins;
only a few are lobe-finned and are thought to be related to the ancestors of
amphibians.
they have a sensory lateral line system
they have highly developed eyes and a keen sense of smell
they have a characteristic protective flap on each side of the body, called
operculum; it covers the gills and enables them to breathe without swimming!
they evolved a so-called swim bladder, which is a gas-filled sac which enables
them to stay buoyant
2 types of bone fish exist today:
1. ray-finned
 have a fin with thin, flexible skeletal rays
22
SAN DIEGO MESA COLLEGE
SCHOOL OF NATURAL SCIENCES
General Biology Lecture (BIOL107); Instructor: Elmar Schmid, Ph.D.
2. lobe-finned
 have a muscular fin with supporting stout bone
 are all extinct with the exception of the living-fossil
C
Cooeellaaccaanntthh, which was found in the 1930s off the
coast of West Africa
 fresh water lobe-finned fish played a key role in
the colonization of land by animals

the lobe-finned C
Crroossssoopptteerryyggiiaann ffiisshh (represented by the marine deep sea-living
Coelacanth  see Images below) are regarded as ancestors of early amphibians
Image of the “living fossil” Coelacanth
Images of crossopterygian fishes
23
SAN DIEGO MESA COLLEGE
SCHOOL OF NATURAL SCIENCES
General Biology Lecture (BIOL107); Instructor: Elmar Schmid, Ph.D.
4- 5 ft
Modern Sarcopterygian fish
(often referred to as
Latimeria
“Living fossil”
Devonian Sarcopterygian fish
Holoptychus
 Devonian lobe-finned fish
 30 inches long
2. Amphibians (Order: Amphibia)
24
SAN DIEGO MESA COLLEGE
SCHOOL OF NATURAL SCIENCES
General Biology Lecture (BIOL107); Instructor: Elmar Schmid, Ph.D.

this group includes 4000 species of animals and accounts for only 8% of all existing
vertebrates

amphibians were the first land vertebrates on Earth and once dominated the
Carboniferous period (around 280 million years ago) where they found favorable
habitats in the huge swamps, wet lands and vast “coal forests”
 fossil evidence, e.g. the early amphibian ancestor Eusthenopteron (see Image
below), suggest that amphibians evolved from (a) fringe-finned fish ancestor(s)
 molecular biological evidence, however, supports the idea that the first
Amphibians evolved around 400 million years ago from so-called lung-fish and
not from lobe- finned fishes
 lung-fish, most of which are extinct today, have gills as well as saclike primitive lungs
 with the decline of the coal forests about 300 million years ago, most
amphibian species also disappeared and became extinct
 some surviving species gave rise to modern amphibians as we know
them today, e.g. frogs, toads, salamanders

prominent members of this transitional group are frogs, toads, salamander and
mud puppies

amphibians spend their larval/juvenile stages in water, and their adult life on land
 they must return to water to mate and lay the fragile, transparent
eggs
 the eggs are fertilized outside the body = external fertilization
 frogs develop into a water-prone larvae called tadpole which
undergoes metamorphosis into the adult animal

amphibians are ectothermic organisms; they depend upon external heat to regulate
their body temperatures
Amphibian features which enabled the march on land
1. limbs with girdles of bone
 skeletal adaptation for walking on land
2. development of a lung, permanently used for gas exchange in the adult form
 some amphibians supplement lung function by exchange of gases
across the skin
3. development of a three-chambered heart
 it pumps mixed blood before and after it has gone to the lungs
4. a larger brain than that of fish
 including a more developed cerebral cortex
5. a closed double-loop circulatory system
 it replaced the single-loop circulatory path of fish
25
SAN DIEGO MESA COLLEGE
SCHOOL OF NATURAL SCIENCES
General Biology Lecture (BIOL107); Instructor: Elmar Schmid, Ph.D.
6. a tongue
 used for catching prey as well as sensory input
7. eyelids
 help to keep the eyes moist and from dehydration
8. pair of ear drums
 adaptation to the thin medium ‘air’ to detect sound waves
9. a larynx
 body instrument for vocalization and communication
10. a thin, smooth and non-scaly skin with numerous mucous glands
 plays an active role in osmotic (= salt) balance and gas exchange
The evolution of amphibians
Comparison of body features and major skeletal parts of a lobe-finned fish
(crossopterygian) and an early amphibian
Reconstructed image of a fringe-finned amphibian ancestor
Late Devonian period (370 – 360 Mio. years ago)
26
SAN DIEGO MESA COLLEGE
SCHOOL OF NATURAL SCIENCES
General Biology Lecture (BIOL107); Instructor: Elmar Schmid, Ph.D.
Eusthenopteron
- rhipidistian (= fringe-finned) fish
- breathed air
- skull close to early amphibians
- complexly folded dentine
- internal nostril and lacrimal duct
- vertebrae similar to amphibians
- pectoral fins had large, humerus-like bone plus carpals
3. Reptiles (Order: Reptilia)

this class comprises about 6000 species, includes the snakes, lizards, turtles,
alligators, and crocodiles

reptiles that lay eggs lay an egg surrounded by a thick protective shell and a series
of internal membranes.

reptiles evolved unique adaptations and body features which are not found in the
evolutionary older amphibians

the rise of the earliest animals with more and more reptilian features from an
amphibian ancestor timely co-incites with the completed formation of the supercontinent Pangaea on planet Earth (see Image below); a massive continental land
mass characterized with vast hot and dry inland areas
 the vaster dry land conditions on Pangaea may have created the necessary
“selective pressure” ( see evolutionary theory in Chapter 14) for the evolution of
an animal form well adapted to these changed climate conditions and habitats
Reconstructed image of the super-continent Pangaea
27
SAN DIEGO MESA COLLEGE
SCHOOL OF NATURAL SCIENCES
General Biology Lecture (BIOL107); Instructor: Elmar Schmid, Ph.D.
(Permian period: 286 – 248 million years ago)
Tectonic movements of the continental plates lead to the
Formation of the C-shaped super-continent Pangaea
Tethys sea
Panthalassa
Panthalassa
- vast interior land mass with dry, continental climate?
- decreased glaciations?
TThhee uunniiqquuee aaddaappttaattiioonnss aanndd bbooddyy ffeeaattuurreess ooff rreeppttiilleess
1. reptilian skin
 it is made up of multiple scales
 the scales are made of the water-proof protein keratin
2. reptiles have a nearly four-chambered heart
 the crocodile has a completely four-chambered heart that more efficiently
separates oxygen-rich blood from deoxygenated or oxygen-poor blood
3. more developed reptilian lung
 an expandable rib cage supports the movement of air moves in and out of the
lungs (all reptiles except turtles) Most. The well-developed kidneys excrete uric
acid; less water is lost in excretion
28
SAN DIEGO MESA COLLEGE
SCHOOL OF NATURAL SCIENCES
General Biology Lecture (BIOL107); Instructor: Elmar Schmid, Ph.D.
4.




they lay drought-resistant amniotic eggs
the embryo develops in a so-called amnion within the egg
an amnion is a fluid-filled sac within the egg
eggs have a protective parchment-like shell which prevents dehydration
eggs can be laid on land where they are hatched; reptiles are hatching animals
5. they are ectodermic
 reptiles warm their bodies up by absorbing external heat (e.g. sun)
 they do not use their metabolism to control their body temperature
6. they perform internal fertilization
 their gametes do not need to be released into water for fertilization
 e.g. snakes, lizards, turtles, crocodiles, alligators

due to these superb adaptation to life on land, reptiles were not as strongly tied to
moist environments and could truly expand into more arid land areas

reptiles once dominated on Earth in form of dinosaurs for more than 300 million
years

the first reptiles (often referred to as the stem reptiles) gave rise to several other
lineages, each of which perfectly adapted to a different way of life
 TThheeccooddoonnttss were the early reptilian ancestors that gave rise to most of the reptiles,
living and extinct
 P
Ptteerroossaauurrss were flying reptiles that dominated the Mesozoic skies

some reptile groups returned to aquatic environments, like the Ichthyosaurs
 IIcchhttyyoossaauurrss were large fishlike (or dolphin-like) freeswimming predators of the Mesozoic seas

about 250 million years ago (late Permian, early Triassic period) reptiles appear in
the fossil records, the so-called therapsids (cynodonts) with mammalian animal
features (e.g. Cynognathus, Dvinia prima: see Image below); one group of
reptiles, the P
Peellyyccoossaauurrss were mammal-like reptiles and are considered to be
ancestral to mammals

the “glorious, long era of the reptiles” suddenly ended at the end of the Cretaceous
period about 65 million years ago

according to a hypothesis by Luis and Walter Alvarez, a large, impacting meteorite
caused a catastrophic environmental collapse that led to the extinction of the
dinosaurs and nearly 50% of all species of life on (Alvarez hypothesis)
29
SAN DIEGO MESA COLLEGE
SCHOOL OF NATURAL SCIENCES
General Biology Lecture (BIOL107); Instructor: Elmar Schmid, Ph.D.

the surviving three groups of reptiles (turtles, snakes/lizards, and
crocodiles/alligators), together with the birds and mammals, reaped the spoils and
diversified during the following Cenozoic Era
Fossil find and reconstructed image of a reptile with mammalian features
(“transition animal”)
Skull fossil
Dvinia
Reconstruction
- Small therapsid reptile (cynodont) with mammalian features
- Late Permian, 250 Mio years ago
- still small brain case
- large dentary and reduced post-dentary jaw bones
- use of post-dentary bones for hearing?
- partially ossified secondary palate
- post-canine teeth with accessory cusps
- reduced or absent lumbar ribs  diaphragm formation?
- primitive insectivore?
30
SAN DIEGO MESA COLLEGE
SCHOOL OF NATURAL SCIENCES
General Biology Lecture (BIOL107); Instructor: Elmar Schmid, Ph.D.
Cynognathus
(Early Triassic, South Africa)
 mammal-like reptile
 has already secondary palate
Structural parts of an amniotic egg
(a defining characteristic for reptiles, birds, and mammals)
4. Birds (Order: Aves)

the class Aves (birds) contains about 9000 species

the evolution of birds is a (still) heavily disputed topic in science, but more recent
spectacular fossil findings in China (e.g. Microraptor gui: see Image below) begin
to shed more light on the natural history of this enormously successful form of
animal life

according to the dominating theory, the first birds evolved from a lineage of twolegged dinosaurs some 160-200 million years ago; others favor a reptilian group

the earliest bird fossils, such as the Jurassic A
Arrcchhaaeeoopptteerryyxx (see Image below) or
Triassic P
Prroottaavviiss, show a mosaic of reptilian and bird features, e.g. teeth in the
31
SAN DIEGO MESA COLLEGE
SCHOOL OF NATURAL SCIENCES
General Biology Lecture (BIOL107); Instructor: Elmar Schmid, Ph.D.
bill, a jointed tail, and claws on the wing are typical reptilian; feathers and hollow
bones are bird features
 despite his feathery coat, Archeopterix is not considered to be the
direct ancestor of modern birds
 it rather seems to reflect an extinct side-branch of birds
 the origin of modern birds is not clarified yet
The evolution of flight & of modern birds from (a) reptilian ancestor(s)
Time



the modern birds appeared during the early Tertiary, and have adapted to all modes
of life:
1. Flying birds:
condors, eagles, hummingbirds,
hawks, blackbirds, etc.
2. Flightless-running birds:
ostriches, emus
3. Swimming birds:
penguins
birds exhibit complex mating rituals as well as social structure
birds inherited a lot of reptile features, such as the
amniotic eggs
scales on their legs
but they also evolved some unique features
32
SAN DIEGO MESA COLLEGE
SCHOOL OF NATURAL SCIENCES
General Biology Lecture (BIOL107); Instructor: Elmar Schmid, Ph.D.
Fossil images & reconstruction of Archeopterix
(Jurassic period: 200 – 144 million years ago)
Archaeopteryx lithographica
 feathered (theropod-like) reptile of the late Jurassic
- bony tail with reduced tail vertebrae (short for theropods)
- reptilian teeth
- clawed fingers
- feathers
TThhee uunniiqquuee aaddaappttaattiioonnss aanndd bbooddyy ffeeaattuurreess ooff bbiirrddss
1. evolution of wings and feathers
 the feathers have a hollow shaft
 the feathers provide insulation, play a role in mating and aid in flight
 the wing structure enables birds to fly
2. most bones of their skeleton are hollow and contain air-sacs
3. they have large breast muscles anchored to a keel-like breast bone
33
SAN DIEGO MESA COLLEGE
SCHOOL OF NATURAL SCIENCES
General Biology Lecture (BIOL107); Instructor: Elmar Schmid, Ph.D.
4. evolved a bill, which lacks teeth
5. they show no wing claws anymore
6. have a high metabolic rate and are endothermic
7. have a highly efficient blood circulatory system and lungs
8. excrete nitrogen-containing metabolic waste in form of uric acid

today, birds are, together with bats (mammalia!), the only flying vertebrates on Earth
 the flying reptiles, e.g. P
Ptteerraannooddoonn, become extinct about 70 million
years ago

due to the powerful flight muscles and high metabolism modern birds are masterful
flyers
 e.g. the hummingbird wing beats 200 times per second in courtship!!
 e.g. albatrosses can fly thousands of miles to find food and can reach
top speeds in the air of 80 km/h!
55.. M
Maam
mm
maallss ((C
Cllaassss:: M
Maam
mm
maalliiaa))

the class Mammalia contains around 5000 species which are placed in 26 orders

the first mammals evolved from (a) synapsid reptilian ancestor(s) ( see:
Synapsida) about 225 million years ago and appeared before the great evolutionary
success and spread (= radiation) of the dinosaurs
 during the dinosaur era they only played a minor role and they lived
as small mouse-sized nocturnal animals (e.g. Eomeia, Hadrocodium wui: see
Image below)

after the extinction of the dominating dinosaurs at the end of the Cretaceous period,
they diversified, radiated and became the most successful animal group on our
planet

mammals have since occupied all important “ecological niches” on planet Earth,
which were once held by dinosaurs and their relatives; they are present by air, land
and sea!

today we know:
1.
2.
3.
4.
flying mammals:
swimming mammals:
large land predators:
large land herbivores:
e.g. bats
e.g. whales, dolphins
e.g. tigers, lions
e.g. elephants, rhinos, giraffes
34
SAN DIEGO MESA COLLEGE
SCHOOL OF NATURAL SCIENCES
General Biology Lecture (BIOL107); Instructor: Elmar Schmid, Ph.D.
5. as well as a new, almost omni-present, thinking and tool-making mammalian
species:
GUESS WHO?
Chart of the proposed mammalian evolution and important fossil findings
250
205
Million years
145
65
Dinosaur
Extinction
today
Kangaroo
Hadrocodium
Marsupialia
Early form 2?
Synapsida
Deltatheridium
Eutherians
Early form 1?
Ukhaatherium
Bats
Placentalia
Mammaliaformes
Vincelestes
Zhangaheotherium
Mammalia
Platypus
Monotremata
Morganucodon
Graphics©E.Schmid/2003

most mammals are land inhabitants and only some, e.g. whales and dolphins,
populate the oceans
 the blue whale is with a length reaching 30 meters the
largest ever existing animal on our planet

some 1000 species known as bats are flying mammals

mammalian animals are characterized by a series of unique body features, which
mostly account for their evolutionary success
35
SAN DIEGO MESA COLLEGE
SCHOOL OF NATURAL SCIENCES
General Biology Lecture (BIOL107); Instructor: Elmar Schmid, Ph.D.
The early mammalian animal ancestor Hadrocodium
(Reconstructed animal & Skull)
Hadrocodium wui
 Fossil find: Yunnan (China), Age: ~195 million yrs. old
 extinct close relative of living mammals
 insectivore; canines, premolars, molars
 separation of middle ear bone from mandible
 larger brain case than cynodont reptiles
I. Reconstructed body features (Science 292(5521): 1535ff (2001)
Weight: ~ 2g
II. Lateral view of restored skull
36
SAN DIEGO MESA COLLEGE
SCHOOL OF NATURAL SCIENCES
General Biology Lecture (BIOL107); Instructor: Elmar Schmid, Ph.D.
TThhee uunniiqquuee bbooddyy ffeeaattuurreess ooff m
maam
mm
maalliiaann aanniim
maallss
1. mammals different shaped (incisors, canines, pre-molars, molars), developed
teeth as highly specialized tools for cutting, shearing or grinding
 the tooth structure is protected by a hard and thick enamel, which
prevents wearing out
2. mammals are capable of rapid and agile locomotion
 the limbs are beneath the body, which provides increased agility
and body size
 mammals place more of the body weight on the long bones
instead on the elbows, ankles, or knees
3. they have a large brain
 the brain sizes are larger per pound of body weight than most
other animals
4. mammalians have hair
 hair provides better insulation, which enables mammals to thrive in
colder regions
 it has sensory function (e.g. whiskers of a cat)
 in form of a fur it serves as camouflage, as a warning system to
predators, or delivers some form of social information
(e.g. social status, age)
5. they show three middle ear bones within their skull
 they are modifications of the malleus, inceus and stapes bones
from the jaws of reptiles
 they allow mammals to hear sounds after they are transmitted
from the outside world to their inner part of the skull
 it triggered the development of sophisticated auditory organs (ears)
6. they produce milk by so-called mammary glands
 the secreted milk nourishes the young offspring
7. they give life birth and don’t hatch their eggs
8. embryos are develop protected inside the female (mother) animal and are
nourished by an organ called placenta (exception are the Monotremes in
Australia)
 embryos held within the mother's body for an
extended gestation period
 the embryo is nurtured by maternal blood which supplies
food and takes up metabolic waste via so-called placental
villi
37
SAN DIEGO MESA COLLEGE
SCHOOL OF NATURAL SCIENCES
General Biology Lecture (BIOL107); Instructor: Elmar Schmid, Ph.D.
9. mammals are endothermic animals
 they regulate their body temperature with the help of metabolic
heat energy

3 major groups of mammalia are known
11.. M
Moonnoottrreem
meess


the duck-billed P
Pllaattyyppuuss of eastern Australia
monotremes are the only egg-laying mammals
22.. M
Maarrssuuppiiaallss




e.g. kangaroos
they have tiny embryonic offspring which complete development outside the mother
at abdominal nipples
the nursing young are housed in an external pouch called marsupium
nearly all marsupials live in Australia, New Zealand and South America
33.. P
Pllaacceennttaall aanniim
maallss ((S
Suubb--ccllaassss:: E
Euutthheerriiaa))



this group makes up almost 95% of the 4500 living species of mammalia
eutherians stay relatively long within the placenta in the so-called amniotic sac
there are 12 orders of placental mammals; prominent orders include the:
1.
2.
3.
4.
5.

bats
horses
whales
mice, rats, rabbits
cats, dogs, mountain lions
(Order: Chiroptera)
(Order: Perissodactyla)
(Order: Cetacea)
(Order: Rodentia)
(Order: Carnivora)
we humans are eutherians, too, and belong together with the monkeys, lemurs and
apes to the order of Primates
33..11.. P
Prriim
maatteess ((O
Orrddeerr:: P
Prriim
maatteess))

evolved from tree-dwelling (= arboreal) ancestors, during a time when reptiles
and dinosaurs still dominated on Earth (see Image below)

primates have unique body features, which were shaped through natural
selection as an adaptation to arboreal life
1. limber shoulder and hip joints
 enabling climbing and graceful movement in trees
38
SAN DIEGO MESA COLLEGE
SCHOOL OF NATURAL SCIENCES
General Biology Lecture (BIOL107); Instructor: Elmar Schmid, Ph.D.
2. 5 digits of hands and feet; thumbs and big toes are opposite to other
digits
 enables efficient grasping and holding of branches
3. have a short snout and eyes are sitting close together
 leads to an overlapping of the field vision and improved
depth perception

2 major groups of primates are known:
1. Prosimian
 35 species are known, of which most live in the tropical rainforests
 many are threatened by extinction due to habitat destruction
by humans (deforestation!)
 e.g. loris, bushbabies, lemurs, tarsiers
 they are the oldest known primates
 65 million year old fossils have been found
 they expanded after the mass extinction of the dinosaurs about 70 million
years ago
 they have a good sense of smell
2. Anthropoids
 e.g. monkeys, apes and hhuum
maannss
 evolved about 40 million years ago in Africa and Asia from prosimian
ancestors
 they have a larger brain in relation to body size
 they rely more on eyesight than on smell
2.1. Monkeys

2 types of monkeys are known
2.1.1. Old world monkeys
 inhabit Africa and Eurasia
 e.g. Baboons, Langur
 are ground-dwelling animals
 they have narrow and close together nostrils
 have seat pads
2.1.2. New world monkeys
 are native to the Americas
 e.g. Golden lion tamarin, Geoffrey spider
monkey
 have wide open nostrils
 have no seat pads but some have long tail
39
SAN DIEGO MESA COLLEGE
SCHOOL OF NATURAL SCIENCES
General Biology Lecture (BIOL107); Instructor: Elmar Schmid, Ph.D.
2.2. Apes








e.g. gibbons, orangutans, gorillas, chimpanzees
are genetically closely related to humans
 about 97% of chimp and gorilla DNA is identical with human
genetic material
most apes live in the tropical rainforests of Africa or
Asia
are heavily threatened from extinction due to man-made deforestation and
human expansion into their habitats
they lack a tail
apes are chiefly vegetarians, but chimpanzees eat insect and occasionally
larger vertebrates
chimpanzees make and use simple tools and show complex social
behavior and group activities
domesticated chimps also show behavior of self-awareness, e.g. in front
of a mirror
2.3. Hominids



about 6-8 million years ago, an ape-like ancestor separated from the
primate tree to become the first hominid
fossil findings link the hominid evolution to regions in East-Africa
about 4 million years ago, the human evolution started from that hominoid
branch and 7 different hominoid species appeared in our lineage
1.




Australopithecus afarensis
lived about 4.0 – 3.0 million years ago
they were only about 3 feet tall
fossilized bones and foot prints were found in East Africa in the socalled Afar depression in todays Ethiopia and Tanzania
they were already upright walking (bipedals!) species
2. Australopithecus africanus
 lived about 3.0 –2.2 million years ago
3. Australopithecus boisei
 lived about 2.5 – 1.4 million years ago
 first evidence of the enlargement of the hominoid brain appears
4. Australopithecus robustus
 lived 2.2 – 1.4 million years ago
40
SAN DIEGO MESA COLLEGE
SCHOOL OF NATURAL SCIENCES
General Biology Lecture (BIOL107); Instructor: Elmar Schmid, Ph.D.
5. Homo habilis (‘handy man’)
 lived about 2.5 –1.6 million years ago
 coexisted on the African savanna with the Australopithecines for nearly
1 million years
 fossilized skulls suggest a larger brain than the Australopithecines
 first evidence of use of primitive tools
6.




Homo erectus
lived between 1. 8 million and 250,000 years ago
was taller than H. habilis and possessed a larger brain
was the first hominid that migrated out of Africa
used already fire, lived in huts and wear clothes
7.



Homo sapiens
is the only remaining member of the hominid family tree
the archaic H. sapiens appeared about 300,000 years ago in Africa
130,000 – 30,000 years ago, several archaic groups of H. sapiens,
e.g. H. neandertalensis, Cro Magnon appeared
throughout Europe, the Middle East and parts of
Asia
about 30,000 years ago these archaic groups died out and the modern
H. sapiens appeared on the scene
the oldest known fossils of the modern H. sapiens found in Africa date
back to about 100,000 years
the modern humans must have co-existed with the archaic types until
about 30,000 years ago; then the archaic humans suddenly
disappeared due to currently unknown reasons
there is still a heated debate about the question of when and where the
modern species of H. sapiens arose
some anthropologists favor the so-called multiregional hypothesis;
this hypothesis states, that the modern type H. sapiens evolved from
archaic populations which existed at different places around the globe
and which interbred with each other
another group of scientists, however, favors the so-called
monogenesis hypothesis, which is based on DNA homology studies
amongst different races of humankind and fossil DNA analysis
 since all living ethnic groups of H. sapiens are genetically
very similar, this hypothesis proposes that modern H.
sapiens arose from a single archaic group in North-East
Africa
 this group spread out of Africa and replaced the
Neandertals and other archaic groups outside of Africa
without mixing with them
 the archaic species H. sapiens simply got extinct and
became dead-ends of evolution






41
SAN DIEGO MESA COLLEGE
SCHOOL OF NATURAL SCIENCES
General Biology Lecture (BIOL107); Instructor: Elmar Schmid, Ph.D.


recently molecular biologists hardened this view and concluded from
mitochondrial DNA (mtDNA) analysis from Neandertal fossils, that the
Neandertal DNA is not closer to European sapiens mtDNA than to
mtDNA from any other human population

currently there is therefore no reason to believe, that archaic groups of
H. sapiens mixed with individuals of the modern type of H. sapiens
the modern type H. sapiens evolved several features which gained it important
advantages over other species and explain it’s tremendous evolutionary success
1. evolution of an erect stance
2. growth of the skull and enlargement of the brain
3. prolonged period of parental care
 the offspring have an extended time to learn from the
experience of parents and earlier generations
4. development of language and complex social behaviours
5. development and social transmission of technological,
scientific and cultural innovations
 e.g. Scavenging-gathering-hunting, tool making,
agriculture, industrialization and global communication
 e.g. establishment of educational institution like the
one you are just decided to attend
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