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Invertebrates
Chapter 33
• Most animals - invertebrates - do
not have backbone.
http://www.edsci-affiliates.com/images/invertebrates_divider.jpg
1Phylum
Porifera
• Sponges - lack nerves and muscles;
sessile (non-motile).
• Most marine, live in water.
• Most hermaphrodites - each
individual produces sperm and eggs.
• Can regenerate lost parts.
http://www.gcb.vic.gov.au/gallery/SEA%20SPONGE,%20PORIFERA.jpg
• Sponges perforated with holes so
water can flow through them
(suspension-feeding)
• Water drawn through pores into
central cavity (spongocoel) and
flows out through larger opening
(osculum)
2Phylum
Cnidaria
• 1st organisms to have true tissues.
• Basic body plan - sac with central
digestive compartment
(gastrovascular cavity)
• Jellyfish, corals, sea anemones, and
hydras.
• Have nerve nets - very primitive
nervous systems that move towards
stimuli.
• 2 body plans in cnidarians.
• 1Polyp stage - sessile; some live
whole life this way.
• 2Medusa stage - cnidarian can swim
freely.
• Can move through both stages
during lifetime.
http://library.thinkquest.org/26153/marine/sketch/613.jpg
• Cnidarians have nematocysts stinging cells.
• Phylum Cnidaria divided into 3
major classes: Hydrozoa (hydra),
Scyphozoa (true jellyfish), and
Anthozoa (sea anemones).
• Cnidarians - carnivores - use
tentacles to push food into
gastrovascular cavity.
3Phylum
Ctenophora
• Comb jellies named for fused cilia.
• Resemble medusa stage of
cnidarians.
• No stinging cells present.
4Phylum
Platyhelminthes
• Flatworms, both parasitic and nonparasitic.
• Flatworms have mesoderm - middle
layer of tissues - makes them
bilateral.
http://www.waterworxbali.com/Images/Photos/Large/pseudoceros-ferrugineus.jpg
• Gastrovascular cavity with only 1
opening; absorb materials across
tissue.
• Flatworms are divided into four
classes: Turbellaria,
Monogenia,Trematoda (flukes), and
Cestoidea (tapeworms).
Turbellaria
http://en.wikipedia.org/wiki/Turbellaria
Trematoda
http://en.wikipedia.org/wiki/Trematodes
Cestoidea
http://www.saudeanimal.com.br/imagens/platelmintos.jpg
• Planaria - scavengers found in
ponds.
• No organs specialized for
circulation or respiration; exchange
gases across membranes.
• Have eyespots for detecting light
and lateral flaps for smell.
• Nervous systems more advanced
than cnidarians; reproduce
asexually through regeneration (can
sexually reproduce).
Planaria
• Trematodes parasites with suckers
to attach to victims.
• Blood fluke - parasite of humans.
• Tapeworms have suckers and hooks
on head; anchor worm in digestive
tract of host.
Blood fluke
5Phylum
Rotifera
• Rotifers - complete digestive tract
with separate mouth and anus.
• Internal organs in pseudocoelom body cavity not completely lined
with mesoderm.
• Functions as circulatory system nutrients dissolved in cavity.
• Have hydrostatic skeleton movement.
http://planktonweb.ifas.ufl.edu/Asplanchna.jpg
• Some rotifers exist only as females
that produce more females from
unfertilized eggs - parthenogenesis.
6Phylum
Mollusca
• Snails, slugs, clams, squid, and
octopus.
• Mollusks soft-bodied animals - most
protected by hard shell of calcium
carbonate.
• All have similar body plan with
muscular foot (locomotion), visceral
mass with most of internal organs,
and mantle.
http://sps.k12.ar.us/massengale/clip0051.jpg
• Use radula to feed - allows them to
scrape up food.
• Most mollusks have separate sexes.
• 4 common classes - Polyplacophora
(chitons), Gastropoda (snails and
slugs), Bivalvia (clams, oysters, and
other bivalves), Cephalopoda
(squids, octopuses, and nautiluses).
Chiton
http://cache.eb.com/eb/image?id=65301&rendTypeId=4
Gastropod
http://www.marinefoundation.org/mussels_600.jpg
Bivalves
Cephalopod
http://home.earthlink.net/~snailstales/cephalopods.jpg
• Gastropods have shells that they
can retreat into (means stomachfoot)
• Lining of mantle acts like lungs allows them to live on land (garden
snails and slugs).
• Bivalves - 2-shelled - clams,
oysters, mussels, and scallops.
• Most bivalves - suspension feeders,
trapping fine particles in mucus
that coats gills.
• Usually sessile - cannot move during
lifetime.
• Cephalopods have reduced shell and
include nautilus, squid, and octopus.
• Nautilus - external shell.
• Have well-developed nervous
system with complex brain and welldeveloped sense organs.
• Cephalopods have closed circulatory
system.
Nautilus
7Phylum
Annelida
• Annelids - segmented worms.
• Digestive system - pharynx,
esophagus, crop, gizzard, and
intestine.
• Closed circulatory system with 5
chambers act as heart to pump
blood.
http://www.inhs.uiuc.edu/~sjtaylor/cave/cave_olig.jpg
• Each segment - pair of excretory
tubes, (metanephridia) - remove
wastes from blood and coelomic
fluid exits through pores.
• Brainlike pair of cerebral ganglia lie
above and in front of pharynx.
• Some earthworms reproduce
asexually (regeneration), also
reproduce sexually.
• Hermaphrodites - exchange sperm
which are stored, then later
fertilize egg.
• Phylum Annelida divided into 3
classes: Oligochaeta (earthworms),
Polychaeta (bristle worms), and
Hirudinea (leeches).
http://www.pmel.noaa.gov/vents/nemo/explorer/bio_gallery/biogallery-ImageF.00049.jpeg
Polychaeta
http://kentsimmons.uwinnipeg.ca/16cm05/16labman05/lb6pg1_files/earthworm1.jpg
• Segmentation of worms allow for
specialization.
• Hirudinea - leeches – parasitic, suck
blood off hosts.
• Used in medicine because they
promote circulation in areas of
body.
Hirudinea
7Phylum
Nematoda
• Roundworms - found in wet
environments.
• Complete digestive tract - use fluid
in pseudocoelom to transport
nutrients (lack circulatory system)
• Reproduce sexually, can be parasitic
(trichinosis)
8Phylum
Arthropoda
• Characterized by body
segmentation, a hard exoskeleton,
jointed appendages.
• Body of arthropod completely
covered by cuticle - exoskeleton
constructed from layers of protein
and chitin.
• Have to molt in order to grow.
• Arthropods have well-developed
sense organs, including eyes for
vision, olfactory receptors for
smell, antennae for touch and smell.
• Arthropods - open circulatory
system - fluid pumped by heart
through short arteries into sinuses
surrounding tissues and organs.
http://www.geocities.com/SouthBeach/7648/internal.jpg
• Aquatic arthropods - gills for
breathing; terrestrial arthropods internal structures for breathing.
• Insects - tracheal tubes to
breathe.
http://www.dwm.ks.edu.tw/bio/activelearner/44/images/ch44c3.jpg
• Trilobites - extinct arthropods - no
specialization.
• Chelicerates mostly extinct; 4
species, (i.e. horseshoe crab) still
alive.
• Modern chelicerates members of
class Arachnida (scorpions, spiders,
ticks, and mites).
Trilobite
Horseshoe crab
• Most spiders - book lungs allow
them to breathe.
• Some can inject poison to kill prey.
• Millipedes - worm-like with 2 pairs
of walking legs on each segment.
• Centipedes - terrestrial carnivores.
• Insects (class Insecta) outnumber
all other forms of life combined 26 orders.
Millipede
• Insects - ability to fly.
• Metabolic wastes removed from
fluid by Malpighian tubules, pockets
of digestive tract.
• Respiration done by branched,
chitin-lined tracheal system carries O2 from spiracles directly
to cells.
• Nervous system - pair of ventral
nerve cords with several segmental
ganglia.
• Metamorphosis occurs in insects;
can be either incomplete
(grasshoppers) or complete
(butterflies).
• Reproduction in insects usually
sexual, with separate male and
females.
• Many arthropods live in water.
• Crustaceans include lobsters, crabs,
crayfish, shrimp, and barnacles.
• Small crustaceans exchange gases
across thin areas of cuticle; larger
species have gills.
• Circulatory system open - heart
pumps fluid into short arteries then
into sinuses that bathe organs.
• Nitrogenous wastes excreted by
diffusion through thin areas of
cuticle, glands regulate salt balance
of fluid (hemolymph).
http://limnology.wisc.edu/personnel/pieter/Hidden%20Stuff/Daphnia/SCDbody.jpg
• Crustaceans - different sexes.
• 3 groups of crustaceans: isopods
(pill bugs, or wood lice), copepods
(small crustaceans) and decapods
(lobsters, crayfish, crabs, and
shrimp).
• Barnacles also crustaceans.
http://farm1.static.flickr.com/1/380353_028542ead3.jpg
Phylum Echinodermata
• Most echinoderms sessile, or slowmoving.
• Most - prickly skin.
• Water vascular system - network of
hydraulic canals branching into
extensions (tube feet) used for
movement, feeding, gas exchange.
http://www.education.umd.edu/blt/pic/Echinoderm.jpg
• Sexual reproduction in echinoderms
- release of gametes by separate
males and females into seawater.
• 6 classes: Asteroidea (sea stars),
Ophiuroidea (brittle stars),
Echinoidea (sea urchins, sand
dollars), Crinoidea (sea lilies,
feather stars), Holothuroidea (sea
cucumbers), Concentricycloidea
(sea daisies)
http://www.arctic.noaa.gov/aro/russian-american/photo-gallery/brittle-stars-Photo-B-Bluhm.JPG
• Sea stars can attach to objects
with tube feet.
• Can regenerate lost parts.
• Brittle stars do not have suckers on
tube feet - have long and flexible
arms.
Sea star
Brittle star
• Sea urchins and sand dollars - no
arms, have 5 rows of tube feet
used for locomotion.
• Sea lilies attached to objects by
stalks, feather stars crawl using
their long, flexible arms.
• Sea cucumbers lack spines - have
tube feet.
Sea urchin
Sea lily
Sea cucumber