Transcript Unit 3 - Invertebrates

Unit 3 Invertebrates
The 9 Major Animal Phyla
• Phylum Porifera
• Phylum Cnidaria
• Phylum Platyhelminthes
• Phylum Nematoda
• Phylum Annelida
• Phylum Mollusca
• Phylum Echinodermata
• Phylum Arthropoda
• Phylum Chordata
Characteristics of Animals
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Multicellular
Eukaryotic
Cells lack cell walls
Heterotrophic- are consumers…they
get their energy from another food
source.
• Most animals have some sort of a
nervous system.
• Most animals use glycogen to store
energy
Symmetry (Pg. 684)
• All animals show some sort of
symmetry
1. Assymmetry
– Irregular shapes
– Do not move (Sessile)
– Sponges
2. Radial Symmetry
 Can divide into equal halves using
many planes.
 Cnidaria (stinging animals)
 Echinoderms (sea stars)
3. Bilateral Symmetry
• Can only divide into left &
right halves
• Most efficient for movement
– Flatworms
– Roundworms
– Mollusks
– Segmented Worms
– Chordates
The 3 Germ Layers
• After fertilization of the egg the new zygote
begins to divide to form the new
multicellular organism.
• During this process of cell division (called
embryogenesis), the cells of most organisms
differentiate into 3 different layers.
• The 3 germ layers are: ectoderm, mesoderm
and endoderm
Phylum Porifera (Sponges)
General Characteristics
Adults are sessile (attached to
one spot)
Asymmetrical or radial body plan
 Typical body form is hollow with
two layers of cells (no true tissues)
separated by a jelly like substance.
Sponges have a “skeleton” of
silicon or calcium carbonate
called Spicules or of fibrous
spongin
Food Capture & Digestion
• Water passes into the sponge through
openings called ostia.
• As the water is passing through the sponge,
specialized flagellated cells called collar
cells trap, ingest and then digest food
particles.
• Collar cells also create the current that
pulls the water through the ostia and out
through a larger opening in the top of the
sponge called the osculum.
Food Capture & Digestion
• Special cells in the middle layer called
amebocytes pick up the partly digested
food from the collar cells, complete the
digestion process and transport the
nutrients to other parts of the sponge.
Respiration
• Sponges do not have any specialized organs
or tissues for respiration.
• As water passes through the sponge gas
exchange is accomplished by diffusion.
• Waste products are also excreted through
diffusion.
Reproduction
• Asexual – Budding creates new small
sponges or gemmules in some groups (A
group of cells that are enclosed in a
tough outer covering that develop into a
sponge when conditions are favorable).
• Sexual – Collar cells change into
gametes. Sperm leave via the osculum
and are drawn into the ostia or pores of
other sponges where they enter eggs in
jelly like middle layer to form zygotes.
Cnidaria General Characteristics
• They are radially symmetrical
•Bodies are saclike with a central
gastrovascular cavity with one
opening. (Their mouth is their anus)
•They have 2 tissue layers
• Outer layer of cells - ectoderm
• Inner layer - endoderm
• In between these tissue layers is a
noncellular jelly-like material called
mesoglea. Cnidarians have no
true tissues, but have a “primitive”
nerve net. “A no brainer”
Cnidarians have 2 body plans:
Respiration & Waste Disposal
•There is no system of
internal transport, gas
exchange or excretion; all
these processes take place
via diffusion
Platyhelmintes (Flatworms) Gen. Characteristics
• They
exhibit bilateral symmetry: anterior and
posterior ends are different; so are the dorsal
and ventral surfaces
•Exhibit some degree of cephalization
•This phylum (and all remaining phyla)
possesses 3 germ layers (endoderm, ectoderm,
& mesoderm)
• The mesoderm (middle germ layer) gives rise
to muscles and various organ systems.
Organ Systems of Flatworms
Cells are organized into tissues
Diagrams on pg. 692 of text.
Digestive System
• Planaria are flatworms that possess a digestive
system, with a mouth, pharynx, and a branching
intestine from which the nutrients are absorbed.
The intestine, with only one opening, is a blind
system .
•Flukes and tapeworms are parasites that have
no digestive system so they absorb nutrients that
have already been digested from their host.
Excretory System
•A network of water collecting
tubules adjacent to flame cells.
These cells remove the wastes from
the body through pores in the skin.
• Parasites remove wastes via
diffusion.
Reproductive System
• Most are capable
of some form of asexual
reproduction (e.g., many turbellarians
reproduce by fission, many can regenerate lost
body parts)
• Most flatworms are hermaphroditic (have
both male & female sex organs); however, they
must pair with other individuals to exchange
gametes. They cannot self fertilize.
• Nematoda - The Roundworms
• Includes roundworms, Pinworms, Filaria,
Hookworms,Trichina, Ascaris
General Characteristics
• Bilaterally symmetrical cylindrical
bodies covered with a tough cuticle.
• Have all 3 germ layers.
Nematodes do not have a respiratory or
circulatory system; both are accomplished
by diffusion
• Body has 2 openings: a mouth and an anus
Reproduction
• Sexual reproduction only.
• Fertilization occurs inside the body of the
female. Fertilized eggs are covered by a
thick shell.
• Separate male and female worms.
Mollusca General characteristics:
•Bilaterally symmetrical & all have a coelom
•All have mantle with shell glands that secrete
calcareous epidermal spicules, shell plates, or
shells.
•Have large, well defined muscular foot, often
with a flattened creeping sole, in squids and
octopus, the foot is modified into tentacles/arms.
•All have soft fleshy bodies which may
be covered by a shell, etc.
General Characteristics
(cont.)
• A well developed open circulatory
system
• Well developed nervous system in
Cephalopods and Gastropods
• All have kidneys for excretion
• Only undergo sexual reproduction,
separate sexes, external fertilization
• Oyster Spawning
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Includes the Phyla:
Bivalvia – Clams, etc.
Gastropoda – Snails, Slugs, etc.
Cephalopoda – Octopus, Squid, Nautilus
• Know the characteristics of each class.
Kingdom Animalia – Phylum Echinodermata
Phylum Echinodermata (spiny skin) – sea stars, brittle stars, sea
cucumbers, sea urchins, sand dollars, etc. (~8,000 - 10,000 species)
General characteristics:
All echinoderms are marine
All echinoderm adults have radial symmetry derived from
bilaterally symmetrical larvae
Nervous system diffuse, decentralized, usually of a nerve
net, nerve ring, and radial nerves.
Have separate sexes, although hermaphroditic species do
exist
Have a water vascular system composed of a series of
fluid-filled canals, usually evident externally as muscular
podia
Kingdom Animalia – Phylum Echinodermata
The water vascular system:
Functions:
Walking
Gas exchange by
diffusion
Sensory
Food manipulation
Phylum Annelida
• This phylum includes the segmented
worms.
• The most commonly known worms in this
phylum are the Earthworm (class
Oligochaeta) and the Leech (class
Hirudinea)
• Annelids are bilaterally symmetrical.
General Characteristics
• Entire body is divided internally and
externally into segments.
• The segment rings are called annuli.
• The first segment is called the
prostomium and the second is called
the peristomium. These 2 segments
form the head of the worm
General Characteristics
• They have a tube within a tube body plan.
• Annelids have a fluid filled body cavity
called a coelom which is lined with
mesoderm.
• They are the simplest of animals that have
a true coelom.
• The body of annelids & the
remaining Phyla of animals
have 3 germ layers.
Characteristics of Arthropods
• Segmented
bodies divided
into 3 regions;
head, thorax &
abdomen.
• In some
arthropods, the
head and thorax
is fused into a
cephalothorax.
Characteristics of Arthropods
Jointed appendages that are always
found in pairs.
Exoskeleton is made of chitin.
• Because the exoskeleton does not
grow, young arthropods must
periodically shed and replace its
exoskeleton in a process called
molting.
• An exoskeleton limits the size of
arthropods
Characteristics of Arthropods
• Complex movement and locomotion
• Nervous system – Distinct dorsal brain
and ventral nerve cord.
• Adapted for land, water, and air
• Well developed sense organs
• Dorsal heart & open circulatory
system
• Terrestrial arthropods have holes in
their exoskeleton to allow for
breathing. These holes are called
spiracles
• There are many classes of arthropods but
we will focus on these 5:
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Crustacea
Chilopoda
Arachnida
Diplopoda
Insecta
– Know the distinct characteristics of these 5
classes.
Reproduction in Insects
• All fertilization is internal.
• Young develop in one of 2 ways.
1. Complete Metamorphosis
• Insects such as moths, butterflies, bees, flies,
beetles and ants.
• Eggs hatch into segmented larvae. After
several molts it passes into a resting stage
called a pupa.
• During this stage the tissues reorganize into
the adult stage.
• The 4 stages are egg → larva → pupa → adult.
Complete Metamorphosis
Incomplete Metamorphosis
• Egg hatches into a nymph which is a small
version of the adult with no wings.
• The nymph is not able to reproduce.
• The nymph goes through several molts until
it reaches adult size. The final molt is when
the wings and reproductive organs develop.
• 3 stages of development: egg→ nymph→
adult