Invertebrate Revision

Invertebrates Revision
Invertebrate: Animal without a backbone

Phylum
Annelids (little rings)
-most in water, some in soil
-segmented worms
-soft-bodies
-take in air through moist skin
e.g. leech, earthworm, fanworm, ragworm

Arthropods (jointed foot)
-found in land and water
-segmented bodies
-exoskeleton
-paired and jointed legs
-most have antennae and compound eyes
-on land, breathing through spiracles (tubes)
-in water, breathing through gills
e.g. ants, crayfish, scorpion, spiders, crabs, flies, butterflies, millipedes, damselflies

Cnidarians (stinging cells)
-most live in the sea, several in fresh water
-soft, hollow bodies
-only one body opening
-tentacles with stinging cells
-no body organs such as heart and lungs
e.g coral, sea anemone, hydra, bluebottle, jellyfish

Echinoderms (spiny skin)
-found only in the sea
-spiny skin
-arms that radiate from centre of body, based on five parts
-tube feet for movement
-mouth and anus
e.g. brittle-star, sea urchin, starfish, sea cucumber

Platyhelminthes (flat worms)
-flat body
-unsegmented
-head-like region
-mouth opening but no anus
e.g. tapeworm, fluke, planarian, flatworm

Poriferans (bearing/with pores)
-found in water
-sponge body with many holes
-food and water enter through tiny holes in body
-waste goes through single large opening
-usually fixed in one place to rocks/shells
-skeleton of glassy/chalky needles or spongy fibres
e.g. bath sponges, glass sponges (all sponges)

Molluscs (soft body)
-Soft, unsegmented bodies
-usually covered with a protective shell
-head with eyes and/or tentacles
-mouth and anus
-muscular foot for movement
e.g. snail, slug, octopus, limpet, clam, squid, oyster

Nematodes (thread form)
-round worms
-found in water, soil, plants and animals
-worm-like body with no segments
-mouth and anus
e.g. threadworm, pinworm, hookworm, whipworm, lungworm

Arthropods
-There are more arthropods than any other animal types on earth
-All have external skeletons
-All have jointed body
-All have paired and jointed legs
-5 Arthropod groups:
1. Crustaceans – at least 10 legs, more than 3 body segments, 2 pair of antennae
(Crabs, shrimps, lobsters, prawns)
2. Arachnids – 8 legs, 2 body segments, 1 pair of antennae (very small)
(spiders, scorpions, ticks, mites)
3. Insects – 6 legs, 3 body segments, 1pair antennae
(butterflies, damselflies, bees, beetles, crickets, ladybirds)
4. Millipedes (diplopods) – 2 pairs of legs per segment, many segments, 1 pair antennae
5. Centipedes (chilopods) – 1 pair legs per segment, many segments, 1 pair antennae
Note: Together, millipedes and centipedes are myriapods
-There are 3 ways to classify arthropods
1. Number of legs
2. Number of antennae
3. Number of body segments

Insects
Insect Body Structure:
-Divided into 3 parts – head, thorax, abdomen
-Head = antennae, eyes, mouthparts
-Antennae, contain organs for smell and touch:
-Long and thin for touch (distance between predator/prey)
-Feathery antennae for sensitivity help pick up scents (e.g. of females)
-Have compound eyes:
-good for seeing movement, escape from predators
-housefly processes 100 images per second to help flying
-Mouths shaped depending on food and eating method
-Sap-sucking = tiny head, pointed tube
-proboscis is a long tubular structure, unrolls to reach nectar (hawk moth, butterfly)
-Sharp proboscis= piercing/sucking blood (female mosquitoes, bedbugs – barbed structure for piercing and sawing, feed before dawn >13 degrees, may take 5mins or more to extract blood meal)
-Also inject saliva containing substance that stops blood clotting
-Proboscis can be blown up (butterfly) or uncoiled using muscles (hawk moth)
-Proboscis is kept coiled at rest, and uncoiled for feeding
-Plant/wood-eating = large head, strong muscles/jaws to bite through plant tissue (grasshoppers and cockroaches have hard, sharp, chewing jaws
-Houseflies and bees lick up their food
-For all insects, mouth connects to digestive system
-Thorax = where legs and wings attach
-These are hollow with exoskeleton like main body
-All have 6 Legs
-Often spurs with sharp claws
-Strong limbs for grasping/holding prey
-Strong hind leg for jumping (grasshoppers)
- Wings important for classification:
-may be one or two pairs (2 or 4)
-may be covered with hairs, scales, have long silky fringes
-In beetle, front pair is hard and thick to protect flying wings when not in use (allows digging)
-Long narrow wings with fringes for fast, accurate flight
-Front and back pairs of wings joined by hooks to beat in unison
-Abdomen = number of segments
-At the end are reproductive organs:
-female = often includes long ovipositor (long thin tube for placing eggs)
-e.g. female wasps lay eggs in paralysed spiders/caterpillars, damselflies within plants
-Sting also located near end of abdomen
-exoskeleton of insects made of substance called chitin
-Tough, waterproof, springy
-Insects have no lungs
-Use trachea, fine tubes, between segments of exoskeleton to transport oxygen around body
-hearing organ location depend on insect, mosquito= base of antennae, cricket=front legs, butterfly=on thorax, cicada=abdomen



Insect Life-cycles

-In all insects: males produce sperm and transfer to female when mating, eggs fertilized, eggs laid near food supply
-Three options after this
1. No change or no metamorphosis
-When born, it already looks like adult, only smaller
-moults exoskeleton several times to allow room for growth
-e.g. silverfish
2. Part change or incomplete metamorphosis
-Young look like adults, but with no wings, different colour and shape
-they moult, grow, and gradually develop these
- stages are egg --> nymph --> adult
e.g. green vegetable bug, dragonfly, damselfly, grasshoppers, termites
3. Complete change or complete metamorphosis
-Four growth stages in their life cycle, e.g. the butterfly, flies, beetles, wasps, bees, ants
-female butterfly lays eggs on leaf (milkweed or swan plant)
-eggs hatch into tiny larva or caterpillar, monarch butterfly caterpillars are green and white
striped. Grow to 3cm long over a few weeks
-the caterpillar hangs by its ‘tail’ from a twig, and changes to pupa form (takes a few hours)
Case of monarch butterfly pupa is glossy green with gold spots.
-most of caterpillar body dissolves, reforms to butterfly
-internal and external differences
-case splits down the side, and the adult emerges
-stages are egg --> larva(caterpillar) --> pupa --> adult

Dichotomous Keys

-Have 2 options at each level
-When making one, the options are never the name of any category/animal
-when reading them, note down each option that lies on the path to a category/animal



Food webs and chains

-Show 2 main things: Feeding relationships and flow of energy
-Carnivore: Animal that eats other animals only
-Herbivore: Animal that eats plants only (primary consumer)
-Omnivore: Animal that eats plants and animals
-food --> consumer
-sun is the source of energy, start of all food chains
-plant = producer
-consumers come after the plants
-first order/primary consumer
-second order/secondary consumer (usually carnivore)
-third order/ tertiary consumer (usually carnivore)
-top order consumer (not eaten by any other animal on the chain)
-in food webs, plants go on the bottom and the consumers generally go in order upward, with the top order animals on top
- When considering the effects of changes, think about
-increase/decrease in predators
-increase/decrease in prey
-maintaining/disrupting balance of food
-main food sources
-increase/decrease in producers
-Remember that food chains often do not develop past three consumer levels, as energy is lost at each level. There would have to be huge amounts of lower consumers/producers to sustain a higher order consumer.

Carbon – CO2

-Plants take in carbon from atmosphere through leaves
-Carbon returned to atmosphere through respiration, decomposition, combustion
-Respiration takes place in every cell of the body
-Animals obtain carbon by consuming plants
-Burning of fossil fuels disrupt natural balance of carbon
-Skeletal remains of aquatic creatures, such as shells and bones, is the source of carbon in limestone
-limestone=calcium carbonate=CaCO3

ihearthorses

(tell me if there's anything else on the test that I have missed!)