Download 11-1 Mollusks • General - invertebrates

11-1
Mollusks
• General
- invertebrates
- soft body covered with shell
- mantle – thin tissue covers internal organs and produces shell
- foot – muscular and is for crawling, digging, catching prey
- found nearly everywhere
- bilateral symmetry
- organs: stomach, reproductive organs, kidneys that remove
wastes
- the water-living ones have gills to remove oxygen from water.
The gills have blood vessels and are covered with cilia.
- Radula – flexible ribbon of tiny teeth
• Types: based on presence of shell, type of shell, type of foot, radulae,
and complexity of nervous system
Gastropods: ex. snail, slug
- most numerous
- snail has 1 shell, slug has no shell
- creep with foot
- herbivores/scavengers/carnivores
- snails have trapdoor on foot used in case of danger or dry
conditions
Bivalves: ex. clam, oyster, scallop, mussels
- 2 shells held by hinges and muscles
- no radulae
- filter feeders
- gills to capture food
- live in water
- as adults stay in one place or move slowly
- pearl: mantle in oysters forms a pearly coat around sand when
sand enters the shell and mantle
Cephalopod: ex. octopus, squid, nautilus
- feet form tentacle around mouth to capture food and for
protection
- nautilus has external shell, squid has internal, octopus has none
- large eyes for excellent vision; large brain; they are intelligent
and can remember
- live in ocean and move by jet propulsion
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Arthropods
General
• invertebrates
• external skeleton called exoskeleton
- waxy/waterproof
- for protection
- made of chitin (tough/flexible)
- molts (sheds the old one to be replaced by a new one; during
this time the organism is soft and has less protection)
• segmented body
• jointed appendages (wing, leg, claw, mouth parts, antenna) for
flexibility and movement
• open circulatory system
• mostly sexual reproduction; either male or female; internal
fertilization
• live everywhere
Earthworms and Arthropods are both segmented but are not related as
shown through their DNA analysis.
Types
1. Crustaceans (shrimp, crab, barnacle, krill)
- 2 or 3 body sections
- 3 pairs of appendages for chewing
- 5 or more pairs of legs
- 2 pairs of antennae
- go through metamorphosis (body changes)
- live in watery environment; get oxygen through gills
- eat dead plants/animals; some are predators, others are herbivores
2. Arachnids (spiders, mites, ticks, scorpions)
- 2 body sections with the head and chest in the first and the
digestive/reproductive organs in the hind/back section (abdomen)
- 8 legs
- no antennae
- breathe with book lungs (tiny tubes leading into the exoskeleton)
Spiders
Mites
some
- predators/herbivores
- some spin webs to trap prey parasites
- hollow fangs, inject venom
Ticks
parasites, cause
diseases like
Lyme Disease
Scorpions
- live in hot climates
- nocturnal
- stingers
3. Centipedes and Millipedes
- both are highly segmented; centipedes have one pair of
legs/segment, millipedes have 2 pairs of legs/segment
- centipedes are predators with sharp jaws to inject venom,
millipedes are herbivores and curl up and squirt a bad-smelling
liquid when disturbed
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Insects (butterfly, cockroach, bee)
Body sections
- head (1 pair of antennae, simple eyes for light/dark, 2
compound eyes for movement)
- thorax (1-2 pairs of wings, 6 legs)
- abdomen (internal organs; get oxygen through tubes leading to
exoskeleton)
Metamorphosis (egg to adult)
- complete: egg, larva which does not resemble the adult, pupa
(cocoon), adult. Ex. most flies, ants
- gradual: egg, nymph which looks like the adult, adult. Ex.
grasshopper, termite, cockroach, dragonflies
Feeding
They eat animals, blood, animal droppings, decaying bodies
Defense
-
hard exoskeleton
run/fly fast
smell/taste bad
stings
camouflage
resemble other animals
Insects and Humans
- harmful
~ damage crops
~ carry disease-causing organisms, ex. mosquitoes carrying
malaria causing parasites
- helpful
~ bees make honey
~ silkworms make silk
~ help pollination
~ biological control; this a method of using natural insect
predators to get rid of harmful insects; it doesn’t harm the
helpful ones unlike pesticides and insects can’t become
resistant
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Communication
• Pheremones: chemicals released by one animal that affect the
behavior of another animal of the same species
• Pheremones are used to locate food, attract mates, distinguish
members of own kind.
• Pheremones are specific; each has different shape and therefore affect
the same species only.
• Some pheremones are made in the lab and used to eliminate pest
insects by trapping them and killing or destroying sperm with x-rays.
• Communication with light produced by the animal is called
bioluminescence. Ex. fireflies use it to attract mates.
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Echinoderms
• General
- invertebrate
- radial symmetry; 5-part
- on ocean floor
- water vascular system: tubes with fluid inside contract and
send the fluid to tube feet that act as suction cups for slow
movement
- internal skeleton called endoskeleton
- spiny skin
- external fertilization in water
- metamorphosis (egg-larva-adult)
- regeneration
• Types
a. sea stars
- eyespot on each arm to sense light
- reproduce by splitting
- use arms and tube feet to move and capture prey; partially
digests food outside then takes in
b. brittle stars
- arms to move; no suction cups so tube feet not used for moving
- get food by tube feet
c. sand dollar and sea urchin
- no arms; move by tube feet; burrow in sand
- teeth to scrape food
d. colorful sea cucumbers
- no arms; crawl with tube feet
- filter feeders; use tentacles to sweep food into mouth