Chapter 12 Review Quiz

Explanation
An animal that doesn't have a backbone is classified as an invertebrate. Invertebrates make up the majority of animal species on Earth and include organisms such as insects, worms, mollusks, and jellyfish. The absence of a backbone allows for greater flexibility and diversity in body structures and functions. Invertebrates have adapted various mechanisms to support and protect their bodies without the need for a rigid internal skeleton.

Explanation
An omnivore is a type of animal that has the ability to consume and digest both plants and animals. Unlike herbivores that only eat plants or carnivores that only eat animals, omnivores have a more flexible diet and can obtain nutrients from both sources. This allows them to adapt to different environments and have a wider range of food options. Some examples of omnivores include bears, raccoons, and humans.

Explanation
Radial symmetry refers to the arrangement of body parts around a central point, like the spokes of a wheel. In this case, the body parts are arranged in a circle, indicating radial symmetry. Bilateral symmetry, on the other hand, refers to the arrangement of body parts into two equal halves, while asymmetry refers to the absence of any symmetry.

Explanation
An animal that stays in one place is called sessile. This term refers to organisms that are permanently attached to a surface and do not move around freely. Sessile animals often have structures such as roots, adhesive discs, or hard shells that help them anchor themselves to their environment. Examples of sessile animals include barnacles, corals, and sponges.

Explanation
A hermaphrodite is an animal that has both male and female reproductive organs, allowing it to produce both sperm and eggs. This is advantageous as it enables the animal to reproduce with any other member of its species, increasing its chances of successful reproduction. This adaptation is commonly found in various invertebrates such as snails, worms, and some fish. By being able to produce both types of gametes, hermaphrodites have a higher reproductive potential and can maximize their chances of passing on their genes to the next generation.

Explanation
Cnidarians are a group of animals that possess stinging cells, which are used for defense and capturing prey. They include jellyfish, sea anemones, and corals. These animals have specialized cells called cnidocytes that contain nematocysts, which are capable of injecting venom into their targets. This unique characteristic of cnidarians sets them apart from sponges and mollusks, which do not possess stinging cells. Therefore, the correct answer is cnidarians.

Explanation
Tapeworms are classified as parasites because they live inside the intestines of their host organisms and obtain nutrients from them, causing harm and potentially leading to various health issues. They rely on the host for survival and reproduction, which is a characteristic of parasitic organisms.

Explanation
Heartworm is caused by roundworms. Tapeworms and flatworms are different types of parasites that can infect animals, but they do not cause heartworm. Heartworm disease is a serious condition that affects dogs and cats, and it is caused by a specific type of roundworm called Dirofilaria immitis. These roundworms are transmitted through mosquito bites and can live and reproduce in the heart, lungs, and blood vessels of infected animals, causing severe damage to the cardiovascular system. Therefore, the correct answer is roundworms.

Explanation
Sponges are classified as animals because they are multicellular, heterotrophic organisms that lack cell walls. They belong to the phylum Porifera and are characterized by their ability to filter feed using specialized cells called choanocytes. Sponges also have specialized cells for digestion, reproduction, and support. Although they may appear plant-like, sponges are considered animals due to their cellular structure, feeding mechanism, and lack of chlorophyll.

Explanation
The body of a sponge is covered by pores. Pores are small openings in the body of a sponge that allow water to enter and exit. These pores are surrounded by specialized cells called porocytes, which regulate the flow of water. The water that enters through the pores carries food particles and oxygen, while waste and carbon dioxide are expelled through the same openings. Pores also play a role in the reproduction of sponges, as they allow sperm and eggs to be released into the water for fertilization.

Explanation
Flatworms and roundworms have bilateral symmetry, which means that their bodies can be divided into two equal halves along a single plane. This type of symmetry is characterized by a distinct left and right side, with similar structures and organs on each side. This allows for efficient movement and coordination of body parts. In contrast, radial symmetry is seen in organisms like jellyfish, where body parts are arranged around a central axis, and asymmetrical organisms lack any specific symmetry.

Explanation
Sponges have the ability to reproduce both sexually and asexually. Sexual reproduction in sponges involves the fusion of gametes from two different individuals, resulting in the formation of a zygote. Asexual reproduction, on the other hand, occurs through budding or fragmentation, where new individuals are formed from a parent sponge without the involvement of gametes. This dual reproductive capability allows sponges to adapt to different environmental conditions and increase their chances of survival and propagation.