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Animal structure and function
Invertebrates -Introduction
Invertebrates
•  Lectures –  Introduction –  Organ systems
•  Seminars
–  Reproduction: November 8
–  Morphological adaptation: November 11
–  Lab seminars
•  Laboratory practicals (print pdfs for Lab 1)
•  Final exam November 21
What is an animal ?
Definition:
–  Multicellular
–  Heterotrophic eukaryotes: ingestion
–  Lack cell wall: structural protein: collagen
–  Nerve and muscle cells
–  Most animals reproduce sexually
–  Embryonic development: zygote to blastula to gastrula
–  Regulatory genes: Hox gene
Animal classification
•  Body plan
–  Body symmetry
–  Tissue organization
–  Body cavities
•  Early embryonic development
Classification by characteristics
of body plan: symmetry
animals, no tissue)
PARAZOA
(near
•  asymmetry
EUMETAZOA (true animals, tissue)
• radial symmetry
=RADIATA
• bilateral symmetry
=BILATERA
Three polarity axes
Bilateria: cephalization
Evolutionary trend towards the concentration of
sensory equipment on the anterior end.
Body symmetry - lifestyle
Classification by characteristics
of body plan: Tissue organisation
TISSUE: Collection of specialized cells isolated
from other tissues by membranous layers
The embryo become layered through
the process of gastrulation
Germ layers
1. Ectoderm
-covering the surface of the embryo
-gives rise to the outer covering of the animal
-gives rise to central nervous system in some phyla
2. Endoderm
-the innermost layer which lines the archenteron
-gives rise to the lining of digestive tract -gives rise to the liver and lungs of vertebrates
=DIPLOBLASTIC (Cnidaria)
3. Mesoderm
-located between ectoderm and endoderm
-forms muscles and most of the organs
=TRIPLOBLASTIC (all bilaterians)
Triploblastic animals can be further classified into
three basic plan of body cavities
A. Coelomate- with a true body
cavity (coelom) that is
completely lined by tissues
derived from mesoderm
B. Pseudocoelomate-with a body
cavity but is not completely
lined by tissue derived from
mesoderm
C. Acoelomate-without a body
cavity
Triploblastic animals (coelomates) can be divided into two distinct grades
A. Protostomia
B. Deuterostomia
Two views of animal phylogeny. Which is right? Both are useful?
Tree based on morphological and Tree based mainly on molecular
developmental comparisons
data
Invertebrates
Life Without a Backbone
Invertebrates
–  Are animals that lack a backbone
–  Account for 95% of known animal species
–  >30 phyla
Figure
33.1
Figures are mainly from the book Biology (ch 32&33) by Campbell & Reece
Black&white figure are from Invertebrate zoology by Ruppert, Fox, & Barnes Phylum Porifera (Phyla Calcarea and Silicea)
“Porifera, sponges (svampdjur)”
•  Non-moving (sessile) animals
•  No nerves or muscles (no tissue differentiation)
•  Mostly marine
•  Most sponges are hermaphrodites.
Phylum Porifera
• Sponges are suspension feeders
-Capturing food particles suspended in the water
that passes through their body
• Choanocytes, flagellated collar cells
-Generate a water current through the sponge and
ingest suspended food
pinacoderm
Pinacoderm= “epithelioid tissue”
Pinacocytes and porocytes
Lab 1:I
Phylum Cnidaria
“corals, jellies, hydras, sea anemones… (nässeldjur)”
• One of the oldest groups in clade Eumetazoa
• Simple diploblastic
• epidermis
• gastrodermis • mesoglea (gelatinous extracellular matrix)
• Radial symmetry
Phylum Cnidaria
• Both sessile and floating forms (Polyp or medusa form)
• One opening in the gastrovascular cavity serves as both mouth
and anus. Phylum Cnidaria
• Carnivores
• Phylum name comes from specialized cells called
cnidocytes
• Cnidocytes are stinging cells used for defense and
to capture prey
Hydra
Phylum Cnidaria
Polyp and medusa
mainly medusa only as polyps Lab 1:II
Hydrozoa & Anthozoa
Phylum Acoela
• 
• 
• 
• 
• 
Basal bilaterians
A simple nervous system
No body cavity (coelom)
Lacks many organ systems
Were classified with other
flatworms in the phylum
Platyhelminthes
Phylum Platyhelminthes
“tapeworms, flukes and flatworms (plattmaskar)“
• Simple, sift, ribbon-like body
• Acoelomates with organ systems
• Inefficient gas exchange across body walls
• Gastrovascular cavity
• Asexual and sexual reproduction
• Marine, freshwater and damp terrestial
• Most free living but many parasites
• Eat microbes and invertebrates
Lab 1:III
Tapeworm
Planarians
Phylum Mollusca
“snails, slugs, clams, oysters, squids, octopuses (Blötdjur)”
• There are at least 93 000 known species
• All molluscs have similar body plan
• Muscular foot
• Visceral mass with organs
• Mantle (that secretes the shell)
• The life cycle of many molluscs includes a
ciliated larval stage called a trochophore
Lab1:IV
Gastropods
•  About three-quarters of all living species of molluscs
–  Belong to class Gastropoda
(a) A land snail
Figure 33.18a, b
(b) A sea slug. Nudibranchs, or sea slugs, lost their shell
during their evolution.
•  The most distinctive characteristic of this class
–  Is a developmental process known as torsion, which
causes the animal’s anus and mantle to end up above its
head
Mantle
cavity
Anus
Mouth
Figure 33.19
Stomach
Intestine
Cephalopods
•  Class Cephalopoda includes squids and octopuses and
nautiluses
–  Carnivores with beak-like jaws surrounded by tentacles
of their modified foot
(a) Octopuses are considered among the
most intelligent invertebrates.
(b) Squids are
speedy
carnivores with
beaklike jaws
and welldeveloped
eyes.
(c) Chambered nautiluses are the only
living cephalopods with an external shell.
Phylum Annelida
“Segmented worms (Ringmaskar)”
• Have bodies composed of a series of fused rings
• Divided into three classes: • Oligocheata - has bristles of chitin (earth worm)
• Polychaeta - has paddlelike parapodia
• Hirudinea- blood sucking parasites (leeches)
• Marine, freshwater and terrestrial
• Asexual and sexual reproduction
Parapodia
Figure 33.24
Figure 33.25
Lab 1:III,IV & 3
Segmentation
The annelid body is composed of three regions:
Prostomium-brain and sense organs
Truck-consists of a longitudinal series of similar body
units- the segments. First segmentlike part= peristomium
Growth zon:
teloblast cells that divide and differentiate
Pygidium- anus
Phylum Nematoda
“Roundworm (rundmask)”
• small
• Marine, freshwater and terrestrial
• Nonsegmented pseudocoelomates
• Covered by a tough coat-cuticle
• Eat microbes, predaceous, or parasitic on plants/animals
Encysted juvenilesMuscle tissue
50 µm
Phylum Arthropoda
“crustaceans, spiders, insects…(leddjur)”
• Three sub-phyla: Chelicerata, Crustacea and Tracheata
• Hard exoskeleton, segmented bodies, jointed appendages
• Arthropods are the most successful of all animal phyla based
on diversity, distribution, and numbers.
• More than one million species identified so far, mostly
insects.
• 1018
Phylum Arthropoda
“crustaceans, spiders, insects…(leddjur)”
•  The exoskeleton, or cuticle, is composed of
protein and chitin.
•  Molting of the cuticle is called ecdysis.
•  Open circulatory systems in which a heart pumps
hemolymph through short arteries and into open
spaces (sinuses). •  A variety of organs specialized for gas exchange
have evolved in arthropods
Lab 1:III,IV, 2, 4, 5
Arthropod body-segmented
Acron=anterior end (prostomium)
First segment-mouth
Growth zon
Telson= posterior end (post anal) (pygidium)
Evolution of the arthropod body
is characterised by tendencies to -tagmosis
-heteronomy
-fusion of segments
-cephalization
Tagmosis
Tagmosis: tendency to organize
segments into region having
similar structure.
Three tagmata: Head, Thorax,
Abdomen
Secondary tagma: cephalothorax:
some or all of the thoracic
segments unite with head
Evolution of the arthropod head (cephalization)
head ancestor Chelicerata
acron
1
A
0
2
L
C
3
L
P
4
L
L
5
L
L
6
L
L
7
L
L
truck
Crustacea Tracheata
A1
A2
A1
0
Mnd
Mx1
Mx2
Mnd
Mx1
Mx2
L
L
L
L
L
L
L
L
L
L
A: antenna
C:Chelicera
chelicerer
L:leg
Mnd:mandible
Mandibler, överkäkar
Mx: maxilla
Maxiller, underkäkar
P: pedipalp
maxillarpalper
0: lost segment
Each higher taxon of modern arhropods has a
characteristic set of head appendages Fig 16-3
Ecdysis (ömsning)
• Arthropoda and other animal taxa: Nematoda, Nematomorpha,
Kinorhyncha, Loricifera and Priapulida have a cuticle that is molted
under hormonal (ecdysone) control.
• Exoskeleton is incapable of stretching
Intermolt
Proecdysis
Ecdysis
Postecdysis
new instar
For Nematoda ecdysis see fig 22-9
Phylum Arthropoda
Sub-phylum
Classes Example
Chelicerata
Arachnida
spiders, scorpions, mites, ticks
Xiphosura
horseshoe crab
Pantopoda
sea spiders
Crustacea
Remipedia
elongated undersea caves crustaceans (10 species)
Cephalocarida “undifferentiated” crustacean(9 species)
Anostraca
fairy & brine shrimps
Phyllopoda
water fleas, clam shrimps
Malacostraca
crabs, lobster, crayfishes, shrimps, krill
Maxillopoda (SC) (8 classes Copepoda) small or micro crustaceans-krill
Tracheata Myriapoda (SC)
Chilipoda
centipedes
Diplopoda
millipedes
Pauropoda
small soft-bodied nocturnal animals
Symphyla
small white elongated animals found in litter
Hexapoda (SC) Insecta (C) (Entognatha (C)) insects
Sub-phyla Chelicerata
–  Are named for clawlike feeding appendages
called chelicerae
–  Include spiders, ticks, mites, scorpions, and
horseshoe crabs
Figure 33.30
Class Arachnida
50 µm
(a) Scorpions have pedipalps that are pincers (b) Dust mites are ubiquitous scavengers in (c) Web-building spiders are generally
specialized for defense and the capture of
human dwellings but are harmless except
most active during the daytime.
food. The tip of the tail bears a poisonous
to those people who are allergic to them
stinger.
(colorized SEM).
Figure 33.31a–c
•  Arachnids have an abdomen and a cephalothorax
–  Which has six pairs of appendages, the most anterior
of which are the chelicerae
Digestive
gland
Intestine
Stomach
Heart
Brain
Eyes
Poison
gland
Ovary
Anus
Book lung
Spinnerets
Figure 33.32
Silk gland
Sperm
Gonopore
(exit for eggs) receptacle
Chelicera
Pedipalp
Sub-phyla Crustacea
• Most diverse arthropod group
• Head, thorax and abdomen-may fuse these parts • 2 pairs of antennae, 1 pair of compound eyes, 3 pairs
of mouthparts (1 pair of mandibles+ 2 pair of
maxillae).
• Some breathe over body surface, but larger species
have gills
•  Decapods are all relatively large crustaceans
–  And include lobsters, crabs, crayfish, and shrimp
–  Three basic body shapes
–  Fig 19-24
•  Super-class Myriapoda (Tracheata)
•  Millipedes, class Diplopoda •  Centipedes, class Chilopoda
–  Have a large number of legs –  Are carnivores with jawlike mandibles
•  Each trunk segment
–  Have one pair of legs per
–  Has two pairs of legs
trunk segment
–  dubbelfotingar
–  enkelfotingar
Class Insecta (Hexapoda, Tracheata)
• Outnumber all other forms of animals.
• Flight was followed by an explosion of diversity.
• Coevolution of flowering plants and insects.
• Well-adapted terrestrial organisms
• Many orders of insects
The external anatomy of an insect
• Truck divided into thorax (prothorax, mesothorax, metathorax) and abdomen
(9-11 segments)
• adults (imago) and usually immatures (juveniles) have 3 pairs of legs (6 parts)
(hexapods) (on thorax)
• 2 pair of wings (forewings and hindwings on meso- and metathorax,
respectively)
• 1 pair of antenna
The internal anatomy of an insect
–  Includes several complex organ systems
The insect body has three regions: head,
thorax, and abdomen. The segmentation
of the thorax and abdomen are obvious,
but the segments that form the head are fused.
Abdomen
Thorax Head
Compound eye
Antennae
Figure 33.35
Heart. The
insect heart
drives hemolymph
through an
open circulatory
system.
Ovary
Malpighian tubules.
Anus
Metabolic wastes are
removed from the
Vagina
hemolymph by excretory
organs called Malpighian
tubules, which are outpocketings of the
digestive tract.
Tracheal tubes. Gas exchange in insects is
Nerve cords. The insect
accomplished by a tracheal system of branched, nervous system
chitin-lined tubes that infiltrate the body and
consists of a pair of
carry oxygen directly to cells. The tracheal
ventral nerve cords
system opens to the outside of the body
with several
through spiracles, pores that can control air
segmental ganglia.
flow and water loss by opening or closing.
Cerebral ganglion. The two nerve
cords meet in the head, where the
ganglia of several anterior segments
are fused into a cerebral ganglion
(brain). The antennae, eyes, and
other sense organs are concentrated
on the head.
Dorsal
artery
Crop
Insect mouthparts are formed from
several pairs of modified appendages.
The mouthparts include mandibles,
which grasshoppers use for chewing.
In other insects, mouthparts are
specialized for lapping, piercing, or
sucking.
Development
• Basic life stages are: egg, juvenile and adult • Substages: instars-separated by molts
• Unually only one adult stage: imago (sexually mature,
wings)
• Life cycle of many hexapods includes a diapause
• 4 basic developmental pattern:
• A. Ametabolous development: young are identical to
adults except in size and sexual maturity.
silverfish
Development
B. Hemimetabolous development: aquatic juveniles
(nymphs) have wing pads that gradually increase in size
and become functional wings only with the final molt.
Adults (aerial) have wings and are sexually mature.
Mayfly dagslända
Development
C. Paurometabolous development (gradual or incomplete
metamorphosis):
Similar to hemimetabolous development except that adults and
juveniles (nymphs) are similar morphologically. The adult form is
reach gradually through a series of molts.
For ex. grasshopper, cockroaches, bugs…
Fig 21-13
Development
D. Holometabolous development (complete metamorphosis):
• The life cycle incudes an additional stage-the pupa
• Imagos are winged, sexually mature and do not molt
• The wormlike juveniles (larvae, maggots, grubs, or caterpillar) do
not resemble the adults.
• At the end of the sequence of larval instars, the juvenile becomes a
nonfeeding pupa- larva undergoes metamorphosis: larval organs are
destroyed and adult structures develop anew from clusters of
embryonic reserve cells known as imaginal discs
Fig 21-14
(a) (caterpillar)
Larva
(b) Pupa (c) Pupa
(d) Emerging adult
Figure 33.6a–e
(e) Adult
Phylum Chordata
“vertebrater, lancettfiskar, manteldjur (urochordater) (ryggsträngsdjur)”
• Consists of two subphyla of invertebrates, Cephalochordata and
Tunicata (Urochordata), as well as the hagfishes (pirål) and the
vertebrates.
• Shares many features of embryonic development with echinoderms
• having, at some time in their life cycle, A) a notochord korda (fexible
londitudial axial rod), B) a hollow dorsal nerve cord, nervrör C) a filterfeeding pharynx with gill slit (organ for feeding and gas exchange) and
an endostyle (mucous net cast) gältarm D) a post-anal tail. svans
• Vertebrata: the dorsal hollow nerve cord has been surrounded with
cartilaginous or bony vertebrae Fig 29-1
Lab1:III