Question

List the vertebrate groups that have each of the following. a. a skeleton of cartilage b. a two-chambered heart c. amniotic egg d. endothermy e. a four-chambered heart f. a placenta g. lungs supplemented by air sacs

Short answer

a. The class Chondrichthyes, including sharks, rays, and skates, have a skeleton of cartilage. b. The class Amphibia, including frogs, toads, and salamanders, have a two-chambered heart. c. The classes Reptilia (snakes, lizards, turtles) and Aves (eagles, pigeons, hummingbirds) lay amniotic eggs. d. The classes Aves (birds) and Mammalia (mammals) are endothermic. e. The classes Aves (birds) and Mammalia (mammals) have a four-chambered heart. f. The class Mammalia, including most mammals, have a placenta. g. The class Aves (birds) have lungs supplemented by air sacs.

Step-by-step solution

a. Skeleton of cartilage

The vertebrate group that possesses a skeleton made of cartilage is the class Chondrichthyes, which includes cartilaginous fishes such as sharks, rays, and skates.

b. Two-chambered heart

The vertebrate group with a two-chambered heart is the class Amphibia, which includes amphibians such as frogs, toads, and salamanders.

c. Amniotic egg

Vertebrae groups that lay amniotic eggs are reptiles (class Reptilia), which includes animals like snakes, lizards, and turtles, and birds (class Aves), which includes animals like eagles, pigeons, and hummingbirds.

d. Endothermy

The vertebrate groups that are endothermic, meaning they can regulate their body temperature internally, are the class Aves (birds) and class Mammalia (mammals).

e. Four-chambered heart

The vertebrate groups that have a four-chambered heart are the class Aves (birds) and class Mammalia (mammals).

f. Placenta

The vertebrate group that has a placenta is the class Mammalia, which includes animals like humans, dogs, and whales. However, it should be noted that not all mammals have placentas, such as monotremes (platypus and echidna), which lay eggs.

g. Lungs supplemented by air sacs

The vertebrate group that has lungs supplemented by air sacs is the class Aves (birds). This adaptation helps birds with efficient respiration for high-energy activities such as flying.

Key concepts

Cartilaginous Fishes

Cartilaginous fishes belong to the class Chondrichthyes. These fascinating creatures, which include sharks, rays, and skates, possess a unique adaptation in their skeletons. Unlike bony fishes, their skeletons are made entirely of cartilage, a flexible and lighter material. This adaptation gives them agility and speed in the water, crucial for their predatory lifestyle. Cartilage is softer and less dense, aiding buoyancy which is an advantage when hunting prey in marine environments.

Amniotic Egg

The amniotic egg is a crucial evolutionary development that allowed vertebrates such as reptiles and birds to lay eggs on land. This specialized egg contains several membranes that protect and nourish the developing embryo, minimizing reliance on aquatic environments for reproduction. The amniotic egg prevents desiccation and provides a stable environment, with features such as the amnion, yolk sac, and allantois catering to the needs of the embryo.

Endothermy

Endothermy is the ability to regulate internal body temperature through metabolic activity. This characteristic is common among birds (class Aves) and mammals (class Mammalia). Endothermy allows these animals to maintain a constant body temperature, ensuring optimal functioning irrespective of external conditions. This is particularly advantageous in adapting to various habitats and engaging in prolonged activities. Endothermic animals often have insulation such as feathers or fur to conserve heat.

Chambered Heart

One of nature's incredible innovations in vertebrates is the chambered heart. Different vertebrates have adapted their heart's structure to suit their lifestyles:

• Two-Chambered: Common in fishes, designed for simple circulation.
• Three-Chambered: Found in most reptiles and amphibians, facilitating more efficient circulation.
• Four-Chambered: Seen in birds and mammals, supports a highly efficient circulation system vital for endothermy.

This adaptation allows more efficient oxygenation of blood, crucial for sustained energy levels, especially in warm-blooded animals.

Placenta

The placenta is a distinctive organ present in most mammals that facilitates the exchange of nutrients and waste between the maternal body and the developing fetus. This adaptation allows the embryo to develop inside the mother, providing it with enhanced protection and a better supply of nutrients and oxygen. Although most mammals have a placenta, it's important to note that some, like monotremes (such as the platypus), do not and lay eggs instead.

Air Sacs in Birds

Birds have evolved an extraordinary respiratory system that includes lungs supplemented by air sacs. This adaptation provides them with a continuous supply of fresh air during both inhalation and exhalation, which is essential for sustaining high levels of flight activity. Air sacs also help to reduce the bird's body weight, aiding in flight. This system is highly efficient, allowing birds to thrive in diverse environments and engage in energy-demanding activities like migration.