Transcript Chapter 23 Part I

Chapter 23 Part I
Animal Characteristics
Animal Characteristics
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Multicellular
Eat other organisms
Can move
Break down food for energy and to build
tissue
 Cells have no cell walls
Food getting
 Some animals hunt
 Some animals are sessile and wait for
food to come to them
 Movement is directly related to method of
getting food
Animal digestion
 Some digest food internally
 Some digest food inside individual cells
 Digested food is stored as fat or glycogen
and used for energy when food is scarce
 Digestive cavities can have one opening
(mouth) or two openings (mouth and
anus)
Animal development
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Blastula
Gastrula
Protostomes
Deuterostomes
Mesoderm
Blastula development
 Most animals develop from a single
fertilized egg (zygote)
 Zygote undergoes cell division to
produce a hollow ball of cells (blastula)
 Blastula – a single layer of cells
surrounding a fluid filled space
 Develops about 10 hours after
fertilization
Gastrula development
 Cells on one side of the blastula fold
inward to form the gastrula
 Outer surface is ectoderm (develops into
skin and nervous tissue)
 Inner surface is the endoderm (develops
into the digestive tract)
Protostomes
 The indented space in the gastrula
develops into the mouth
 Have one opening in their digestive tract
Deuterostomes
 The indented space in the gastrula
develops into the anus; mouth develops
from cells in another location
 Complex animals
 Two openings in the digestive tract
Mesoderm
 Third layer of cells that develops between
the endoderm and ectoderm
 Develops into muscles, reproductive
organs, and circulatory vessels
Body plans: symmetry
 Asymmetry
 Radial symmetry
 Bilateral symmetry
Asymmetry
 Irregular body shapes
 Usually sessile organisms
 Ex: sea sponge
Radial symmetry
 Can be divided along any plane, through
a central axis, and produce roughly equal
right and left halves
 Detect and capture prey from any
direction
 Ex: hydra, starfish
Bilateral symmetry
 Divided down the length into right and left
halves that form mirror images
 Anterior is head
 Posterior is tail
 Dorsal is the back
 Ventral is the belly
 Find food/mates more efficiently due to
better muscle control
Body Cavities
 Acoelom
 Pseudocoelom
 coelom
Acoelom
 Three cell layers (ectoderm, endoderm,
mesoderm)
 Digestive tract
 NO body cavity
 Organs embedded in tissues
 Water/digested food travel through body
by diffusion
 Ex: flatworms
Pseudocoelom
 Fluid-filled body cavity partially lined with
mesoderm
 Develops between endoderm and
mesoderm
 More efficient movement
 Two openings in digestive tract
 Ex: roundworms
Coelom
 Body cavity completely lined with
mesoderm
 Internal organs suspended in fluid-filled
space
 Allows space for complex organs
 Ex: humans
Adaptations
 Exoskeleton
 Endoskeleton
Exoskeleton
 Hard, waxy covering on outside of the
body
 Provides support, protection
 Prevents water loss
 Place for muscle attachment in
invertebrates
Endoskeleton
 Internal skeleton found in vertebrates
 Protects internal organs
 Place for muscle attachment
26.2 Sponges
 Phylum Porifera
 Sessile (attached to a single spot as
adults)
 Multicellular
 Heterotrophic
 No cell walls
 Few specialized cells
Sponge body plan
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No mouth, gut, tissues, or organs
Use only specialized cells
Asymmetrical
No dorsal, ventral, left or right sides
Body is tubular and arranged around a
central opening through which water
flows
Body plan cont.
 Choanocytes (cells with flagella) keep steady
current of water flowing
 Water enters through pores in body wall but
flows out through osculum (hole at top of
sponge)
 Movement of water through sponge allows
feeding, respiration, circulation, and excretion
 Spicules-structure made of CaCO3 or silica
make up internal skeleton in some sponges
Sponge feeding
 Filter feeders – sift microscopic food from
water
 Intercellular digestion occurs in
choanocytes that take in the food and
then pass it to archaeocytes that
transport digested food throughout the
sponge
Sponge response
 No nervous system
 Protect themselves with toxins that make
them taste bad or make them poisonous
to predators
Sponge reproduction
 Sexual – figure 26-9
 Sperm release into water by one sponge are
carried on currents to another sponge
 Sperm are carried to egg by archeocytes
 After fertilization, zygote develops into a larva
(immature form; looks different)
 Larva are motile (usually use flagella) so
swimming and currents carry them to new
areas on sea floor
Sponge reproduction cont
 Asexual budding – a piece of a mature
sponge breaks off, settles on sea floor,
and develops into a new sponge
 Asexual gemmules – groups of
archeocytes surrounded with spicules;
used to withstand unfavorable conditions;
good conditions allow the gemmules to
develop into a new sponge
Ecology
 Sponges provide habitat for other
organisms (commensalism)
 Sponges pair up with photosynthetic
organisms providing their habitat, while
the photosynthetic organism gives food
(mutualism); also helps productivity at
coral reefs
26.3 Cnidarians
 Soft-bodied
 Carnivorous
 Stinging tentacles arranged in a circle
around the mouth (cnidocytes- stinging
cells that contain nematocysts or darts
with poison to kill prey)
 Simplest animals with symmetry and
specialized tissues
Cnidarian body plan
 Radial symmetry
 Central mouth surrounded with tentacles
 Life cycle includes the polyp (sessile) and
medusa (motile) stages
 Body wall surrounds the gastrovascular
cavity (digestion occurs in gastroderm)
 Outside layer is epidermis
 Middle layer is meoglea
Cnidarian feeding
 Paralyze prey before pulling it in to the
gastrovascular cavity
 Extracellular digestion (outside of cells)
 Digested food is absorbed by gastroderm
 Digestion completed inside cells of
gastroderm
 Undigested materials are expelled
through the mouth
Cnidarian response
 Use a nerve net – loosely organized network of
nerve cells that allow detection of stimuli
(touch)
 Usually distributed evenly throughout body but
can be centrally located around mouth
 Statocysts help determine direction of gravity
 Ocelli – are eyespots that help detect light
Cnidarian movement
 Some use hydrostatic skeleton – layer of
circular muscles and layer of longitudinal
muscles, with water in gastrovascular
cavity, enable movement
 Medusas use jet propulsion – muscle
contractions that force water out of the
“bell” of the organism which pushes the
organism forward
Cnidarian reproduction
 Sexual – figure 26-15
 Eggs and sperm released into water by
separate sexes
 External fertilization occurs producing the
zygote that grows into a free swimming larva
 Larva eventually attaches to hard surface to
develop into polyp
 Polyp buds and releases the medusa
Cnidarian reproduction
cont
 Asexual – budding
 Budding can occur in polyps, producing a
genetically identical organism
Jellyfishes
 Class Scyphozoa
 Live primarily as medusas
 Polyp is small larva stage that does NOT
produce colonies
 Reproduce sexually
Hydras and relatives
 Class Hydrozoa
 Polyps grow in branching colonies, can be
specialized for specific functions
 Portuguese man-of-war
 One polyp produces the “balloon” or float
 Others produce tentacles to catch prey
 Some also undergo digestion
 Hydras – freshwater, lack a medusa stage;
solitary; reproduce both sexually and asexually
and may have symbiotic relationship with
photosynthetic protists
Sea anemones and corals
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Class Anthozoa
Only a polyp stage
Central body surrounded by tentacles
Many are colonial
Sea anemones
 Live at all depths
 Usually solitary
 Can by symbionts with photosynthetic organisms
Corals
 Most colonial
 Hard corals develop after a motile larva
attaches to a solid surface
 New polyps produced by budding
 Produce skeleton of CaCO3 or limestone
 Can live for hundreds-thousands of years
 Sexual reproduction
 External fertilization (eggs and sperm are released
into water)
Ecology of corals
 Distribution determined by temperature,
water depth, light intensity
 Hard corals need high levels of light
 Rely on mutualistic relationships with
algae (provide 60% of energy needed by
corals)
 Corals provide habitat to a variety of
marine organisms (commensalism)
Damage to corals
 Human activity
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Logging
Divers that damage corals
Silt
Farming / mining
Release of chemicals
 High temperatures
 Kill algae and cause bleaching
 May be due to global warming