Arthropods have exoskeletons and joints!
What are they?
1. Flea
2. Housefly
3. Tarantula fangs
4. Horseshoe crab
5. Fruit Fly
6. Coconut Crab
An arthropod is an invertebrate that has a segmented body covered with a hard outer skeleton. The outer skeleton is called the exoskeleton. Arthropods can have many pairs of legs and other parts that extend from their body, like antennae.
Many arthropods live in water, but most live on land. The exoskeleton allows arthropods to live in any environment. It completely covers the body of an arthropod and acts like a suit of armor protecting their soft body. On land, the exoskeleton keeps cells, tissues and organs from drying out.
What is the picture below highlighting about insects?
What is the picture below highlighting about insects?
The arthropod's skeleton has joints, places where the exoskeleton is thin and flexible. An arthropod body typically has three sections: a head at one end, a thorax in the middle, and an abdomen at the other end. Legs are jointed, as are other parts attached to the body, such as antennae and claws. Muscles attach to the exoskeleton as it grows.
Exoskeletons do not grow. How do arthropods grow with a suit of armour on?
An arthopod must shed its exoskeleton as it grows. This process is called molting. For an arthropod, the times when it molts are dangerous because its soft body is exposed to predators.
Arthropods have well-developed body systems.
- A nervous system with a brain and many different sensory organs
- A digestive system with a stomach and intestines
- A circulatory system with an open circulation of blood. There are no blood vessels.
- A reproductive system that uses only sexual reproduction
Insects
Scientists have so far identified over 700,000 insect species.
- Included Are:
- beetles
- bees
- wasps
- ants
- butterflies
- moths
- grasshoppers
- beetles
- 3 pairs of legs
- 3 body segments
- 1 pair of antennae
- Most live on land
Insects show great diversity in appearance. Many species have adaptations in color and shape that allow them to blend into their environments.
Many insects have compound eyes and antennae, which are sensory organs. Compound eyes have poor image resolution, however, they provide a wide angled view and the ability to sense fast moving objects. This is why it is so hard to catch a fly. It's not that they see your hand...they perceive the sudden movement.
Many insects are herbivores. Some insects, for example, ants termites, and some bees, are social insects. They must live in groups in order to survive. Members of the group work together to gather food, maintain the nest, and care the offspring. Often with social insects, just one female, called the queen, produces and lays eggs.
During their life cycle, insects undergo a process in which their appearance and body systems many change dramatically. This process is called metamorphosis. There are three states to complete metamorphosis.
- larva
- pupa
- adult
Crustaceans
Crustaceans Include:
- Crabs
- Lobsters
- Crayfish
- Shrimp
- Krill
- Woodlice
- Barnacles
Most crustacean species live in the water. Atlantic lobster and the Dungeness crab, are used by people as a source of food. Crustaceans are important to the ocean food web. Tiny crustaceans such as krill and copepods are a food source for many other animals, including other invertebrates, fish, and whales.
Most crustaceans are free-living aquatic animals, but some are terrestrial like woodlice, some are parasitic such as fish lice and tongue worms and some are sessile such as barnacles.
Crustaceans have:
- 3 or more pair of legs
- two pairs of sensory antennae
- water-living crustaceans have gills
- open circulatory systems..no blood vessels
- reproduce sexually
- young hatch from eggs
The eating habits of crustaceans vary. Lobsters and shrimp eat plants and small animals. Many crustaceans are scavengers, feeding off the remains of other organisms. Some, such as barnacles, are filter feeders. The larval form of a barnacle is free swimming. However, as an adult this arthropod attaches itself to a rock or another hard surface, such as a mollusk's shell or the hull of a ship. It uses its tentacles to capture food from surrounding water.
While watching the video, answer the questions below.
- Legs that can bend are said to be ______________________________.
- What are two sensory objects that arthropods have______________________ _________________
- What is an appendage ______________________________
- What is an arthropods skeleton called ___________________________
- In order to grow an arthropod must _________________________
- How long does it take an arthropod to grow a new exoskeleton _________________________________
- Where do horseshoe crabs mate __________________ Where do they lay their eggs __________________
Draw a picture of a lobster. Label the following:
head
thorax
abdomen
appendages
head
thorax
abdomen
appendages
Arachnids
They include:
- Spiders
- Mites
- Ticks
- Scorpions
Mites
Ticks
Scorpions
Like all arthropods, arachnids have an exoskeleton, jointed limbs, and segmented bodies. But the bodies of arachnids have some characteristics that distinguish them from other arthropods.
Arachnids have:
4 pairs of legs
2 body segments (head is on the thorax)
No antennae
Arachnids have:
4 pairs of legs
2 body segments (head is on the thorax)
No antennae
Some arachnids, including ticks and most mites, are parasites. Other arachnids, such as spiders and scorpions, are predators. Predatory arachnids kill their prey by stinging them, biting them, or injecting them with venom.
Four signs of arachnid bites:
- lesion
- bulls eye
- fang marks
- ulceration
Spiders are the largest group of arachnids. Many spiders have a unique adaptation for capturing their prey. They produce an extremely strong material, called silk, inside their bodies and use the silk to make webs for capturing food. The spider spins strands of silk out from tubes called spinnerets at the rear of its abdomen. It weaves the strands into a nearly invisible web. The web serves as a net for catching insects and other small organism that the spider eats. This adaptation allows web-building spiders to wait for their prey to come to them. Other invertebrates, such as silkworms, produce silk, but they do not weave webs.
Millipedes and Centipedes are Arthropods
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Both centipedes and millipedes have long, segmented bodies and many legs. However, animals from these groups differ in their body features and their behavior.
Millipedes are:
- 2 pairs of walking legs on each body segment
- move slowly
- eat decaying leaves and plant matter
- when disturbed, many millipedes emit a foul odor that is harmful to predators
Centipedes are:
Fast movers
1 pair of walking legs per body segment
antennae
jawlike mouth parts
pinchers on their rears to paralyze prey and protect them from predators
Fast movers
1 pair of walking legs per body segment
antennae
jawlike mouth parts
pinchers on their rears to paralyze prey and protect them from predators