All **arthropod** species are characterized by their segmented body, strong exoskeleton, and jointed appendages. Hence, the correct answer is **B**

B

**Arthropods** is a group of animal species that have segmented bodies, a tough external exoskeleton that is used for protection and support, and joint appendages in the form of antennae, and legs. Examples of this species are insects, crabs, and spiders.

**Arthropods’** exoskeleton primarily functions in their protection, support, and homeostasis maintenance. Therefore, among the given choices, the production of the gametes is the correct answer because the exoskeleton is not responsible for this process, rather it is the responsibility of their reproductive system. The correct answer is **A**

A

**Arthropods** are animal species that have body segments and joint appendages. Arthropods are also known for having an exoskeleton that functions for protection and support.

Terrestrial arthropods respire through a network of tracheal tubes that extend all the way to the body. Some arthropods respire through an organ named **book lungs**. These are respiratory tissues that are stacked and piled up like pages of a book. Hence, the correct answer is **B**.

B

**Arthropods** are animal species that have body segments and joint appendages. **Arthropods** are also known for having an exoskeleton that functions for protection and support. Example species are spiders, crustaceans, and insects.

Most arthropods have **open circulatory system** in which the blood is pumped by the heart into the *hemocoel** of an organism, and the blood is being carried back to the circulatory system through the process of diffusion. *The hemocoel is a body cavity that bathes the organ with blood.*

Hence, the correct answer is **B**

B

Only members of the subphylum Crustacea have two pairs of antennae.

B. two pairs of antennae

**Chelicerates** are a group of arthropods that have mouthparts called *chelicerae*, they have dual body sections and almost all species have four pairs of walking legs. All chelicerate species do not have antennae. Example species are spiders, horseshoe crabs, ticks, and scorpions. Hence, the correct answer is **D**

D

Horseshoe crabs have ten legs and they lack an antennae and a segmented body.

D. ten legs

**Insects** is a group of arthropod species that has a body divided into three parts namely the **head, thorax,** and **abdomen**. Insects grow and develop through the process of metamorphosis. Example species are ants, bees, butterflies, and cockroaches. Hence, the correct answer is **D**

D

**Echinoderms** are animal species under the phylum Echinodermata. These species are characterized by having spiny skin, internal skeleton, water vascular system, and cuplike suction on the ventral portion of their body called tube feet. Most adult species appear to have five-part radial symmetry.

Hence, the correct answer is **C**.

C

**Echinoderms** are animal species under the phylum Echinodermata. These species are characterized by having spiny skin, internal skeleton, water vascular system, and cuplike suction on the ventral portion of their body called tube feet. Most adult species appear to have five-part radial symmetry.

The **water vascular system** functions to carry out important body processes including movement, nutrient circulation, and respiration. The system is filled with fluid, and it opens to the outside through a sievelike organ called madreporite. Hence, the correct answer is **B**.

B

Insects, such as grasshoppers, that live on land are able to breathe using the tracheal tubes inside their body. Spiders have book lungs for respiration, while horseshoe crabs use book gills to breathe underwater. Other aquatic arthropods use feathery gills to respire through the water.

The different respiratory structures of arthropods have allowed them to thrive in different habitats such as the ocean, freshwater, land, and air. Because of this, arthropods are considered as the most diverse animals since they cover a variety of organisms that live in the biosphere.

The different respiratory structures of arthropods have allowed them to thrive in different habitats such as the ocean, freshwater, land, and air. Because of this, arthropods are considered as the most diverse animals since they cover a variety of organisms that live in the biosphere.

**Arthropods** is a group of animal species that have segmented bodies, a tough external exoskeleton that is used for protection and support, and joint appendages in the form of antennae, and legs.

**Terrestrial arthropods** dispose of nitrogenous wastes through the malpighian tubules that move the wastes from the blood to the feces. On the other hand, **aquatic arthropods** move cellular waste by diffusion from the body into the water

Arthropods have a well-developed nervous system which consists of a brain and ganglia. The brain is connected with two nerve cords that are responsible for receiving information and sending instructions to the muscles. These cords are surrounded by ganglia that help coordinate the animal’s movements.

A carapace is a tough upper shell that covers the cephalothorax of crustaceans. It provides protection to the body of the animal. It also allows some crustaceans to use this shell as a disguise when a predator is around.

**Barnacles** are sessile arthropod species that attached themselves to a hard substrate or animal species such as whales and crabs. They do not have abdominal segments and their mandible is considered vestigial. On the hand, **decapods** are arthropods that have five pairs of legs which they utilize for locomotion. They have an abdominal segment that is fused with the pair of paddlelike appendages to form their flat tail in their posterior region. These organisms use their mandible for feeding.

A crustacean’s mouth has a mandible that allows an animal to bite and crush the food.

**Chelicerae** are pair of appendages found in the front of the mount of arachnid species that usually functions as pincer-like claws. On the other hand, **pedipalps** are joint appendages that look like small legs but they rather function as antennae These structures are used by arachnids to sense objects that they encounter such as prey or danger. Moreover, pedipalps help spiders to shape their webs.

Most of mites and ticks are parasitic. The mouthparts of mites and ticks have special adaptations such as needle-like chelicerae, and pedipalps with claws that are used to attach themselves to the body of the host and draw blood from it.

**Centipedes** have one pair of legs per body segment while millipedes have two pairs of legs per segment. **Centipedes** are carnivores whose mouth parts have venomous claws while **millipedes** feed on decaying plants and animals. Unlike the **millipedes**, their spiracles cannot close and are not waterproof. Therefore, millipedes have to live in moist areas

Their evolution developing flight in order to span wide geographical systems and the fact that the young insects look and feed differently from the adults help the insects in surviving various habitats

Many insects produce saliva containing digestive enzymes that help break down food. Flies have spongelike mouth parts used to lap up foods. Ants use mandibles to saw and grind food

Ants, bees, and termites each have hierarchical rankings within their society. **Certain divisions of insects carry out specific functions in the society**. Each division works together to enable the survival of the species.

Echinoderms have an oral end or anus that releases nitrogen-containing wastes into the environment in the form of feces. In some echinoderms, the wastes in the form of ammonia are expelled into the environment using their skin gills and tissues in their tube feet.

**Sea stars** are the most commonly known echinoderms. These animal species move by creeping slowly along the floor of the ocean using their tube feet. Sea stars have the ability to regenerate and repair their damaged part as long as it has the central part of the body.

Sea stars reproduce sexually through *external fertilization*. The sperm produced in the testes and eggs produced in the ovaries are both released into an open water environment in which they will fertilize independently. The larvae will then grow from the fertilized egg and then eventually develop into an adult matured sea star.

A sea star called the crown-of-thorns preys on corals by absorbing the nutrients from the coral tissues. Because of this predation, some coral reef systems were affected and destroyed.

**Honeybees** are covered by body hairs which are extensions of their exoskeleton. These hairs act as a sensory organ that detects the flow of the air and the presence of any chemical substance in their environment. Moreover, these body hairs have the capability to collect pollen and other substances that the bees can carry as they move from one place to another.

This will be an advantage to the flowering plants because this phenomenon aids in their reproduction.

Blue crabs have soft shells during certain times of the year. It is because of molting. An exoskeleton does not grow as the animal grows. So when an animal grows, the exoskeleton undergoes a period of molting. During molting, an arthropod sheds its entire exoskeleton and replaces it with a larger one. The new exoskeleton is soft so that it can take the shape of an animal’s body and after that, it hardens to its usual toughness.

Chelicerates are a group of arthropods that have mouthparts called chelicerae, which they use to suck their prey. They have dual body sections and almost all species have four pairs of walking legs. All chelicerate species do not have antennae. Example species are spiders, horseshoe crabs, ticks, and scorpions.

Therefore, the unknown animal cannot be considered an insect as all of its observable characteristics fall into the descriptions of chelicerates.

Based on the given data, the relationship between the temperature and hatching time is inversely proportional–meaning as the temperature decreases, the greater the time needed for the eggs of the brine shrimp species to hatch. Therefore, it would be beneficial to have a higher temperature for the eggs to hatch immediately.

A crawfish can live out of water for days provided that their gills are always wet. When a crayfish lies on its side near the water surface, it exposes their specialized gills with oxygenated water. By moving its appendages, the water gets circulated over its gills. This behavior was caused by an external stimulus, which is the need for oxygen.

The variety of foods or substances that the insects feed on are allowing them to have more chances of survival when they are placed under unfavorable conditions. If a particular food source gets compromised, other species which feed on a different food can still survive.

**Arthropods** are a group of animal species that have segmented bodies, a tough external exoskeleton that is used for protection and support, and joint appendages in the form of antennae, and legs. Examples of this species are insects, crabs, and spiders.

**Echinoderms** are animal species under the phylum Echinodermata. These species are characterized by having spiny skin, internal skeleton, water vascular system, and cuplike suction on the ventral portion of their body called tube feet. Most adult species appear to have five-part radial symmetry.

Pheromones play an essential role in an insect’s survival by triggering a particular a behavior or a function in an individual. They serve as messengers that give out signals about any food source, potential harm or a call out for a mate.

When chitin is combined with other proteins, the exoskeleton of arthropods can evolve into different forms. This allowed arthropods to have different appendages such as wings, flippers, claws, and antennae. This is why some insects are able to crawl, swim, or fly. The different structures of arthropods have allowed them to thrive in different habitats such as the ocean, freshwater, land, and air. Because of this, arthropods are considered the most diverse animals since they cover a variety of organisms that live in the biosphere.