Arthropods, Echinoderms

Phylum Arthropoda

• Characteristics– Largest group of animals– Have jointed appendages which include

legs, antennae, claws and pincers– Have bilateral symmetry, segmented

bodies, exoskeletons, a body cavity, a digestive system with two openings and a nervous system

– Most have separate sexes and reproduce sexually

Arthropods

• Body Segments– Bodies of these animals are divided into

segments similar to segmented worms– Some have many segments, others have

segments that are fused together to form body regions

• Exoskeleton– A hard outer covering that supports and protects

the internal body and provides places for muscle to attach.

– Doesn’t grow as the animals does, it is shed and replaced during a process called molting

Insects

• Have three body regions• Head

– Has a pair of antennae, eyes and a mouth• Thorax

– Three pairs of legs and one or two pairs of wings if present are attached here

• Abdomen– Where reproductive structures are found

Insects• Have an open circulatory system that

carries digestive food to cells and removes wastes

• Insect blood doesn’t carry O2 instead air enters and exits through openings called spiracles found on the abdomen and thorax

• Are the only invertebrate animals that can fly

Metamorphosis

• A series of changes that an insect goes through

• Two types– Complete

• Includes stages of egg, larva, pupa, and adult• Ex. Butterflies, bees, flies

– Incomplete• Includes stages of egg, nymph, adult• The nymph form molts several times before

becoming an adult• Ex. Grasshoppers, crickets

Insects & Food

• Feed on a number of things have different mouth parts to obtain food

• Grasshoppers and ants have large mandibles for chewing

• Butterflies and honey bees have siphons for lapping up nectar

• Aphids and mosquitoes have mouth parts that are adapted for piercing into plants or other organisms

Insects success

• Insects are extremely successful based these reasons– Tough flexible, waterproof

exoskeleton– Ability to fly– Rapid reproduction cycles– Small sizes

• Insects have other adaptations that allow them to be successful

What is the difference between a moth (1st picture) and a butterfly (2nd) ?

Moth antennae end in clubs, they’re bodies are often furrier and when at rest, their wings are flat (butterflies rest with the wings pointing up

ORDER LEPIDOPTERA

Arachnids

• Have two body regions– Cephalothorax and an abdomen

• Four pairs of legs and no antennae• Many are adapted to kill prey with

poison glands, stingers, or fangs• Some are parasites

Arachnids• Scorpions

– Have sharp, poison filled stinger at the end of abdomen.

– Have a well-developed appendages which they can grab their prey.

• Spiders– Can’t chew their food, release enzymes into

prey to digest it—then suck the predigest liquid into its mouth.

– Have book lungs where O2 and CO2 are exchanged.

Brown recluse bites cause necrosis (death of tissue).

Arachnids

• Mites & Ticks– Most are parasites– Ticks have specialized mouthparts to

remove blood from the host.– Ticks often carry disease such as

Lyme disease.

Centipedes & Millipedes

• Have long bodies and many segments, exoskeleton, jointed legs, antennae and simple eyes.

• Found in damp environments• Reproduce sexually• Make nests for eggs and stay with them

until they hatch.• Centipedes are predators• Millipedes feed on decaying plant matter.

Crustaceans• Have one or two pair of antennae

and mandibles, which are used for crushing food.

• Most live in water, but some live in moist environments on land—such as pill bug.

• Have five pair of legs, first pair of legs are claws for catching and holding food.

Crustaceans

• Swimmerets are appendages on the abdomen which help in movement and are used in reproduction; also force water over the gills used in O2 and CO2 exchange

• If a crustacean loses an appendage it can regenerate it

• Include crabs, crawfish, shrimp, lobster, and sowbugs (rolypolys)

Value of Arthropods

• A source of food• Agriculture would be impossible

without bees and other insects to pollinate crops

• Useful chemicals are obtain from some arthropods

• Important part of ecological community

Controlling Insects

• Not all arthropods are of value some are pests that carry disease or can damage crops

Controlling Insects

• Common ways to control insects– Insecticides, but these also kill non-

harmful insects– Biological controls

• Types of bacteria, fungi, and viruses can be used to control insects

• Natural predators being released to kill the harmful insect

• Some how interfere with reproduction of the particular insect

Origin of Arthropods

• Some fossils are more than 500 million years old

• Scientist hypothesized that arthropods probably evolved from an ancestor of segmented worms because they have body segments

• The hard exoskeleton and walking legs allowed arthropods to be among the first animals to live successfully on land

Phylum Enchinodermata

• Characteristics– Have an endoskeleton covered by a thin,

bumpy or spiny epidermis– Radial symmetrical—allowing them to sense

food, predators and other things in the environment from all directions

– Have mouth, stomach, intestines– Feed on a variety of plants and animals– Have no head or brain, but have a nerve ring

that surrounds the mouth– Also have cells that respond to light and touch

Water-Vascular System

• A characteristic unique to echinoderms• Allows them to move, exchange CO2 and

O2, capture food, and release wastes• It is a network of water-filled canals with

thousands of tube feet connected to it.• Tube feet—hollow, thin walled tubes that

ends in a suction cup.– As pressure in the tube feet changes the

animal is able to move along by pushing out and pulling in its tube feet

Types of Echinoderms

• Sea Stars– Echinoderms with at least 5 arms

arranged around a central point– Uses tube feet to open shells of prey,

once open pushes its stomach into shell and uses an enzyme to digest it

– Reproduce sexually– Can repair themselves by regeneration

Types of Echinoderms

• Brittle Stars– Have fragile, slender, branched arms

that break off easily– This adaptation allows them to survive– They can regenerate broken off body

parts– Use flexible arms for movement and

tube feet to get food into their mouths

Types of Echinoderms

• Sea Urchins & Sand Dollars– Disk or globe-shaped animals covered

in spines– Spines help in movement and in

burrowing– Also can protect them from predators – Sea Urchins have five tooth like

structures around their mouth

Types of Echinoderms

• Sea Cucumber– Soft bodied echinoderms– Have a leathery covering– Have tentacles around their mouth

and rows of tube feet on their upper and lower surfaces

– When threatened, they may expel their internal organs which will then be regenerated in a few weeks

Value of Echinoderms

• Feed on dead organisms in the marine environment

• Help recycle material• Used for food• Possible sources of medicine• Sea stars can help control the

population of other organisms

Origin of Echinoderms

• Date back more than 400 million years ago• Earliest echinoderms had bilateral

symmetry as adults• Scientists hypothesize that echinoderms

more closely resemble animals with backbones than any other group of invertebrates– Have similar embryos that develop similar to

vertebrates– Complex body systems