UNIT 6: ARTHROPODS AND ECHINODERMS

BIOLOGY II

  SECTION-1: CHARACTERISTICS OF

ARTHROPODS • -There are more species in the Phylum

Arthropoda than in all the other animal phylums combined. (There are over 1 million species of arthropods that have been described. However the total number of arthropods may be as high as 1 billion billion.)

Survival

• Adaptations are traits that makes an organism better able to survive in an environment.

• Arthropods have many adaptations that have helped them to survive in many environments.

CHARACTERISTICS

• -Three characteristics shared by all arthropods are1.      exoskeleton2.      segmented body 3.      jointed appendages (which includes walking legs, claws, antennae, and wings.)

 

1. Exoskeleton

• the rigid outer body covering of an arthropod.

EXOSKELETON

-(The exoskeleton is like a suit of armor made up of nonliving material that protects the body.)

EXOSKELETON

• The exoskeleton provides protection from being eaten by animals and from drying out.-The exoskeleton can bend at the joints.-The exoskeleton is nonliving and cannot grow, so the animals must molt.

MOLTING

• -Molting is the shedding of the exoskeleton that occurs at regular periods as the arthropod grows.-(Before the arthropod molts it forms a new, soft exoskeleton beneath the old one.

MOLTING

• When the new on is ready it sheds the old exoskeleton. The new exoskeleton must now harden so the animals will usually hide until it hardens because they are without protection.

Open Circulatory System

•a system in which the blood is not contained within small tubes.

CIRCULATION

-Blood is pumped from the heart into the space of the arthropods body.

-(The blood of arthropods carries food but not oxygen throughout the body.)

RESPIRATION

• -They have any of 3 special respiratory organs: gills (Crab), book lungs (spider), or tracheal tubes (grasshopper).

REPRODUCTION

• -They reproduce sexually.

BODY PARTS

• -They have 3 main body parts: 1. Head - first part of body and contains sense organs. 2. Thorax or chest - middle body part with walking legs attached. 3. Abdomen - last body part containing reproductive and digestive organs.

BODY PARTS

• -The three body parts can be divided into segments (centipede and millipede) and in some the segments may be fused, or joined (arachnids, crustaceans).-Arthropods have pairs of jointed legs (allowing the legs to bend.) used for walking, swimming, or hopping.

Five classes of arthropods:

• 1. Class Crustacea (lobster, shrimp) -5 pairs of legs

• 2. Class Arachnida (spiders) – 4 pairs of legs• 3. Class Insecta (fly) – 3 pairs of legs• 4. Class Diplopoda (Millipedes) – 2 pairs of legs

per segment• 5. Class Chilopoda (Centipedes) – 1 pair of legs

per segment 

SECTION-2: DIVERSITY OF ARTHROPODS

 

Class Crustacea

Crustacean

• -A crustacean is an arthropod that usually has five pairs of jointed legs, 2 pairs of antennae, and mouthparts used for crushing and grinding. Example: shrimp, lobster, crabs, crayfish, and barnacles.

Crustacean

• -In the Class Crustacea-Most found in ocean. (a few are freshwater: waterflea; and one class is found on land: pill bugs)-Have hard exoskeleton (contains calcium) and mandibles (for grinding).

Crustacean Body Parts

• -Two main body parts: 1. Cephalothorax - fused head and thorax. 2. Abdomen-2 pairs of antennae: short pair for touch, taste and balance and a long pair for touch, taste, and smell.

Crustacean Body Parts

-2 compound eyes on the end of short stalks.

-5 pairs of legs: First pair are adapted as claws (for food getting and defense), and other 4 pair are walking legs.

-Swimmerets are attached to the abdomen and function in reproduction.

Respiration

• -Breaths through gills.-Gills are structures that function in respiration. As water passes over the gills oxygen is absorbed. (Land dwelling crustaceans like the pill bug also have gills and require moisture for survival.)

Food Source

-Crustaceans are an important food source for humans, fish, and whales. (shrimp, lobsters, crabs, crayfish)

Centipedes

Class Chilopoda

-Ex: Centipedes

-A centipede is an arthropod that has one pair of jointed legs in each body segment and eats small animals (carnivore). 

Millipede

Class Diplopoda

-Ex: Millipede

-A millipede is an arthropod that has two pairs of jointed legs in each body segment and eats plants (herbivore).   

Arachnids

Class ARACHNIDA

-An arachnid is an arthropod that has four pairs of walking legs.

-Examples: spider, scorpions, ticks, mites, granddaddy long legs.

• Ticks and mites are parasites (feed on the blood of its host) and sometimes carry diseases (rocky mountain spotted fever).

ARACHNIDS

-A chigger is a type of mite which can cause severe inching when it affects humans.

ARACHNIDS

• -Scorpions have a sharp poisonous stinger at the end of the abdomen. The stinger is very painful but not usually fatal to humans.

• Most live on land.-2 body parts: a fused head and thorax called cephalothorax and an abdomen.-4 pairs of simple eyes.-No compound eyes or antennae.

RESPIRATION

• -Breaths through respiratory organs called book lungs.-Book lungs are a series of flat, air-filled plates that function in respiration in most arachnids. (Oxygen diffuses into the blood at the book lungs.)

• -Spiders build webs made of silk thread to trap insects. (Insects become trapped in the sticky threads.)-The silk web (made of liquid protein) is made in the abdomen and flows out through spinnerets. The web hardens when it comes in contact with the air.-Spiders have poison fangs near its mouth which paralyze or kill its prey.

•Spiders suck out the liquid part of its prey's body.

• -Most spiders are helpful to humans by eating insects that are harmful to humans or to crops. 

• Most spiders are helpful to humans by eating insects that are harmful to humans or to crops.

Insects: The most numerous Arthropods.

-Class insecta.-Its the largest class of arthropods

  -An insect is an arthropod with three pairs of jointed legs.-Contain 2/3 of all animal species.

•There are more than 300 million insects for every person on Earth.

STRUCTURE OF INSECTS-3 body parts: Head, thorax, and abdomen.

• -Head contains mouth parts called mandibles.-Mandibles are a pair of jaws used for chewing.-(Other insects may contain mandibles but it depends on the type of food they eat. Some insects eat plants and others eat meat.)

   -Head also contains antennae.-An antenna is a sense organ that functions in touch and smell.

-Insects have 2 types of eyes: 1. Simple eyes detect only light and dark. 2. Compound eyes senses movement, some colors, and unlike the human eye, it contains several thousand lenses. (A lens is a structure that focuses light.)

-(The compound eye forms many images with each image being a small part of the surroundings that the animal sees. The brain then combines all the images to show a complete picture.)

-The thorax has both legs and wings attached.-3 pairs of legs: 2 used for walking and 1which is much larger than the rest. (The large one is often used for jumping.)

-2 pairs of wings. (1 pair of long narrow wings protects the wider more fragile wings that are used for flying. When the insect is not flying the narrow wings lay on top of the flying wings.)

-Insects are the only invertebrates that can fly.-Insects breath through small openings called spiracles located on their abdomen.

-By moving the wings and abdomen the insect pumps air into the spiracles. (if you have ever seen a insect sit and slowly move its wings up and down then you have seen the insect breathing.)

-After air enters through the spiracles it travels through a system of tracheal tubes that branch throughout the insect body. (Oxygen is absorbed and carbon dioxide is released and pumped back out of the body.)

-Reproduction is sexual.-(The male deposits sperm in a special sac within the female's body. When the female is ready to lay her eggs, the eggs and sperm come into contact.)

-The female lays a large number of eggs making it possible for a large number of offspring which increases the chances of the species surviving.

Metamorphosis

-Metamorphosis is a series of distinct changes in form through which an organism passes as it develops from an egg to an adult.

-Two types of metamorphosis: 1. Incomplete metamorphosis is where insects pass through 3 stages of development (example: grasshopper, cricket, termites, dragonflies): a.       Egg (female lays eggs in a hole she has dug.)

b.      Nymph is an immature form that looks like a small adult.

c.       Adult is an animal that has grown and developed enough to reproduce.

2. Complete metamorphosis is where insects pass through 4 stages in its development (example: most insects, butterfly, ants, bees, moths): a.       Egg

b.      Larva is an insect in the worm like stage. Example: caterpillar, mealworm (Larva hatch from the egg and immediately begin eating a great deal and growing.)

c.       Pupa is the third stage that occurs inside a cocoon. (Within the cocoon the tissues of the larva reorganize to form the adult insect.)d.      Adult

TYPES OF INSECT BEHAVIOR

1. Pheromones are powerful chemicals only detected by insects that attracts mates from up to several kilometers downwind.

2. Social Insects live in colonies or hives and depend on the each other for survival. Example: bees, ants, termites.

DEFENSE MECHANISMS OF INSECTS 

1. Stingers of wasp or bees

2. Camouflage

SECTION-3: ECHINODERMS: THE “SPINY-SKINNED” ANIMALS

-Echinoderms are spiny skinned animals which have an internal skeleton, a five-part body, a water vascular system, and structures called tube feet.

-Includes starfish, sea lilies, feather stars, sea cucumbers, sea urchins, sand dollars, and brittle star.

• -In the Phylum Echinodermata.-The internal skeleton is bonylike calcium plates that are spiny.-The water vascular system is a system of fluid filled tubes that carry food and oxygen, remove wastes, and help in movement.

• Tube feet are suction cuplike structures that are connected to the water vascular system and allow echinoderms to walk.

STARFISHES

-Starfish (or sea stars) have 5 or more rays or arms extending from a central body.

-The underside of each arm contains hundreds of tube feet for movement and obtaining food.

• -(When a starfish passes over a clam, its favorite food, the tiny tube feet grasp the clam’s shell. The suction action of the hundreds of tube feet creates a tremendous force on the clam’s shell. Eventually the shell opens and the starfish enjoys a tasty meal.)

Regeneration

•Starfish are capable of regeneration.

OTHER ECHINODERMS

-Sea lilies and feather stars resemble flowers and stars with long feathery arms.

• Sea cucumbers resemble warty cucumbers. (Move by using five rows of tube feet on their body surface to wiggle back and forth on the ocean floor.)

-Sea urchins are round, dome shaped, and contain long spines for protection. (Some urchin’s contain spines with poison sacs found at the tip which can deliver poisonous stings.)

•Sand dollars are round and flat shaped.