Notes for Quarter 4
Information Posted on 6/6/06
Notes for Chapter 17 – Birds and Mammals
Section 1 – Characteristics of Birds
One familiar characteristic of birds is their feathers – they help birds stay dry and warm, attract mates, and fly. In the act of preening, birds use their beaks to spread oil on their feathers. The oil is made by a gland near the bird’s tail. When feathers wear out, birds replace them by molting. Most birds shed their feathers this way at least once a year.
Birds have two main kinds of feathers – down feathers and contour feathers. Down feathers are fluffy, and lie next to the bird’s body, helping it stay warm. Contour feathers are stiff, and cover a bird’s body and wings. Contour feathers have a stiff central shaft with side branches called barbs.
Birds need a lot of energy to fly. To get the energy, their bodies must break down food quickly. This creates a lot of body heat. To cool off, birds lay their feathers flat and pant like dogs do. To sustain the energy needed to fly, birds must eat a lot. Birds have a unique digestive system (Fig. 3, p. 443) to help them get energy quickly. Since modern birds don’t have teeth, food goes from the mouth to the crop, where it’s stored until it moves to the gizzard. Many gizzards have small stones inside that grind food up so that it can be easily digested in the intestine.
Most birds can fly, and have adaptations such as large eyes, wing shape, a rapidly beating heart, air sacs, hollow bones, and powerful flight muscles (Fig. 4, p. 444-445). Birds are able to stay in the air because their wings cause lift – an upward force on a bird’s wings.
Most birds build nests in which to lay their eggs (Fig. 6, p. 446). They keep their eggs warm by brooding – the act of sitting on eggs and using body heat to keep them warm. Some birds, such as chickens and ducks, are active soon after they hatch. These active chicks are called precocial. Others, such as hawks and songbirds, are weak and helpless for a while after hatching. These weaker chicks are called altricial.
Section 2 – Kinds of Birds
There are about 10,000 species of birds on Earth. Songbirds, such as robins and bluebirds, make up the largest order – about 60%. Bird species can be grouped into four categories: flightless birds, water birds, perching birds, and birds of prey.
Flightless birds: Not all birds fly. Instead of flying, some flightless birds run quickly to move around. Fig. 1, p. 448 shows three flightless birds – the penguin, the kiwi, and the ostrich.
Water birds: Many flying birds are comfortable in the water. These include ducks, cranes, geese, pelicans, and loons. Many eat plants, invertebrates, or fish (Fig. 2, p. 449).
Perching birds: These birds have special adaptations for resting on branches (Fig. 3, p. 450). Songbirds, such as robins, warblers, and sparrows make up a large part of this group of birds. When a perching bird lands on a branch, its feet automatically close around a branch. Even while asleep, the bird’s feet still grip the branch, so that the bird doesn’t fall off.
Birds of Prey: These birds (Fig. 4, p. 451) hunt and eat other vertebrates, such as mammals, fish, reptiles, and birds. Birds of prey like owls and ospreys have good vision, sharp, curved beaks, and sharp talons on their feet. Most hunt during the day, like the osprey, but owls hunt at night.
Section 3 – Characteristics of Mammals
Mammals live in a wide variety of climates on Earth. There are approximately 5,000 modern species, all of which share certain characteristics, despite varying in many ways. Mammals appeared in the fossil record more than 225 million years ago, and were about the size of mice. When the dinosaurs died out, more land and food became available for the mammals.
Mammals share many common characteristics. These include:
Mammary glands – structures that make milk. All female mammals feed their young with this milk (Fig. 2, p. 453). Milk is made of water, proteins, fats, and sugars.
Like birds and reptiles, mammals use lungs to get oxygen from the air. But mammals have a diaphragm, a large muscle that helps bring air into the lungs. It lies at the bottom of the rib cage.
All mammals are endothermic. This means that internal chemical changes keep their body temperature constant.
Mammals have a few characteristics that keep them from losing heat. One way they stay warm is by having hair. Mammals are the only animals that have hair. Mammals that live in cold climates, such as the fox in Figure 3, p. 454, have thick coats of hair called fur. Most mammals also have a layer of fat under their skin to keep them warm.
Mammals have specialized teeth, with different shapes and sizes for different jobs. The three kinds of teeth are incisors – cutting teeth, in the front of your mouth; canines are stabbing teeth, and the flat, grinding back teeth are called molars.
All mammals reproduce sexually – sperm fertilizes eggs inside the female’s body. Most mammals give birth to live young, and newborn mammals stay with at least one parent until they are grown.
A mammal’s brain size is much larger than that of most other animals that are the same size. The larger brain size allows them to learn and think quickly, and also to respond quickly to events around them.
Section 4 – Placental Mammals
A placental mammal is a mammal whose embryos develop inside the mother’s body, growing inside an organ called the uterus. An organ called the placenta – which carries food and oxygen to the embryo - attaches the embryos to the uterus.
The time in which an embryo develops within the mother is called a gestation period, and lasts a different amount of time for each kind of placental mammal. It is 9 months for humans. The most common orders of placental mammals are:
Armadillos, Anteaters, and Sloths: This group of mammals have unique backbones that have special connections between the vertebrae. Most mammals in this group eat insects that they catch with their long, sticky tongues (Fig. 1, p. 456).
Insectivores: This group of mammals includes moles, shrews, and hedgehogs (Fig. 2, p. 457). Most are small, and have long, pointed noses that help them smell their food. They have small brains and simple teeth, and eat worms, fish, frogs, lizards, and small mammals in addition to insects.
Rodents: This group makes up one-third of mammal species (Fig. 3, p. 457). They include squirrels, chinchillas, porcupines, rats, mice, and guinea pigs. They have one set of incisors, which get worn down because of continual gnawing and chewing. They grow continuously, however.
Rabbits, Hares, and Pikas: Like rodents, this group of mammals (Fig. 4,p. 458) have sharp, gnawing teeth. However, unlike rodents, they have two sets of incisors and a shorter tail.
Flying Mammals: Bats are the only mammals that fly (Fig. 5, p. 458). Most eat insects or other small animals. Most bats use echolocation to find things. When flying, bats make clicking noises that echo off of trees, rocks, and insects.
Carnivores: This group of mammals (Fig. 6, p. 459) have large canine teeth and special molar teeth for slicing meat. Some are omnivores – like the black bear – and some are even herbivores that eat plants. Fish-eating ocean mammals such as walruses are called pinnipeds.
Trunk-Nosed Mammals: Elephants alone among the mammals possess a trunk – a combination of an upper lip and nose (Fig. 7, p. 459). It uses its trunk like we use our hands, to put food in its mouth. It also uses it to spray its back with water to cool off.
Hoofed Mammals: This group of mammals have at least one hoof – a thick, hard pad that covers the entire toe (Fig. 8, p. 460). Odd-toed hoofed mammals include horses and zebras, and even-toed hoofed mammals include pigs, deer, cattle, camels, and giraffes. Most are fast runner, and have large, flat molars to grind the plants they eat.
Cetaceans: This group of mammals are made up of whales, dolphins, and porpoises. All live in the water, have lungs, and nurse their young (Fig. 9, p. 461).
Manatees and Dugongs: This is the smallest group of mammals that live in the water. They use their front flippers and tails to swim, and eat seaweed and water plants (Fig. 10, p. 461).
Primates: This group of highly intelligent placental mammals (Fig. 11, p. 462) consist of prosimians, monkeys, apes, and humans. They have five fingers on each hand, and five toes on each foot. Most have flat fingernails, and have a larger brain than most other mammals their size. They have forward-facing eyes for focusing, and opposable thumbs for holding things. Many primates live in trees, aided by adaptations of flexible shoulder joints and grasping hands and feet.
Section 5 – Monotremes and Marsupials
A monotreme is a mammal that lays eggs. They have all the traits of other mammals, such as mammary glands, a diaphragm, and hair. They are also endothermic. The eggs laid by a monotreme have a thick, leathery shell. Monotremes don’t have nipples, so the babies lick milk from the skin and hair around the mother’s mammary glands.
There are three living species of monotremes. Two of these are echidnas. Their large claws and long snouts help them dig ants and termites out of nests (Fig. 1, p. 464). The other monotreme is the platypus, which lives in Australia. It has webbed feet and a flat tail to help it swim. It uses its flat, rubbery bill to search for food, and lays its eggs in tunnels that it digs out along riverbanks.
Marsupials are kangaroos and other mammals with pouches. Unlike monotremes, marsupials give birth to live young. Newborn marsupials continue their development in a mother’s pouch; newborns can stay in the pouch for several months. They’re born at an early stage of development, just days or weeks after fertilization (Fig. 3, p. 466).
Commonly known marsupials are kangaroos, koalas, and opossums (Fig. 4, p. 466). But less-well known marsupials include wallabies, bettongs, numbats, and Tasmanian devils. At least 22 of Australia’s native mammal species have become extinct in the last 400 years (Fig. 5, p. 467). Exotic species and habitat destruction continue to threaten marsupials in Australia.
Information Posted on 5/21/06
Notes for Chapter 16 – Fishes, Amphibians, and Reptiles
Section 1 – Fishes: The First Invertebrates
The skeletons of humans, fish, and dinosaurs all have something in common: they all have a backbone. Animals that have a backbone are called vertebrates. Vertebrates belong to the phylum Chordata; members of this phylum are called chordates.
Vertebrates make up the largest group of chordates, but there are two other groups as well – lancelets and tunicates (Fig. 1, p. 412). These two groups of chordates are much simpler than vertebrates, lacking a backbone and well-developed head. These three groups share certain characteristics; namely four particular body parts (pharyngeal pouches, hollow nerve cord, notochord, and tail) at some point in their life (Fig. 2, p. 413).
Fishes, amphibians, reptiles, birds, and mammals are vertebrates. One major difference between vertebrates and the other types of chordates is a strong, flexible column of bones called vertebrae. These vertebrae surround and protect the spinal cord, and help to support the rest of the body. Another major difference is the head – vertebrates have a well-developed head protected by a skull, which is made up of either cartilage or bone. Cartilage is a tough material that the flexible parts of our ears and nose are made of. Bone is much harder than cartilage, and so it can be easily fossilized. Fossil evidence shows that fishes were the first vertebrates on Earth, first appearing about 500 million years ago.
Some vertebrates are warm-blooded animals called endotherms – animals that have a stable body temperature. They use energy released by the chemical reactions in their cells to warm their bodies. Other animals depend on the surroundings to stay warm, since their body temperature changes as the temperature of the environment changes. These animals that do not control body temperature through activity in their cells are cold-blooded animals called ectotherms.
There are over 25,000 species of fishes, and many look different from each other. But all fishes share several characteristics: Fishes use fins – fan-shaped structures – to steer, stop, and balance. Many fishes also have bodies covered by bony structures called scales. Fishes have a brain to process information coming in from the senses of vision, hearing, and smell. Most also have a lateral line system – a row of tiny sense organs that detect water vibrations. Fishes use gills to breathe. A gill is an organ that removes oxygen from the water, and is also used to remove carbon dioxide from the blood. Most fish reproduce by external fertilization (where the female lays unfertilized eggs in the water, and the male drops sperm on them). But some species use internal fertilization, where the male deposits sperm inside the female.
There are five very different classes of fish. Two of these classes are extinct, and so we’ll focus only on the three that are living. These are: the jawless fishes, cartilaginous fishes, and bony fishes.
Jawless fishes, like the hagfish and lampreys (Fig. 6, p. 416), are eel-like. Hagfish eat dead fish on the ocean floor, and lampreys suck other animals’ blood and flesh using a tooth-lined suction cup mouth.
Cartilaginous fishes have skeletons that lack bone, their skeletons being made of cartilage alone. Sharks, skates, and rays are examples of this class of fish (Fig. 7, p. 417). They are strong swimmers and excellent predators, possessing fully functional jaws. They store oil in their liver to help stay afloat.
Bony fishes make up 95% of all fishes. They have skeletons made of bone, and their bodies are covered by bony scales. They possess a swim bladder, a balloon-like organ that is filled with oxygen and other gases. The bladder inflates to make the fish more buoyant (and rise up in the water), and deflates to allow the fish to sink to a deeper depth. There are two groups of bony fishes: ray-finned fishes and lobe-finned fishes (Fig. 8, p. 418).
Section 2 – Amphibians
Amphibians are animals that can live in water and have lungs and legs. A lung is a saclike organ that takes oxygen from the air and delivers oxygen to the blood. These fishes also had strong fins that could have evolved into legs.
The word “amphibian” means ‘double life.’ Most amphibians live part of their lives in water and part of their lives on land. Embryos must develop in a wet environment, since eggs do not have a shell or a membrane that prevents water loss. Most amphibians live in the water after hatching and then develop later into adults that can live on land.
Amphibians have thin, smooth, moist skin. The skin is so thin, in fact, that amphibians absorb water through it instead of drinking. But they can also lose water through their skin and become dehydrated. For this reason, most amphibians live in water or in damp habitats. Many amphibians also have brightly colored skin, which serves to warn predators that their skin contains poison glands.
A tadpole is an immature frog or toad that must live in water, getting oxygen through gills and using its long tail to swim. Later, the tadpole loses its gills and develops lungs and legs that allow it to live on land. The change from an immature form to an adult form is metamorphosis (Fig. 4, p. 422). A few amphibians don’t go through a full metamorphosis, rather hatching as tiny versions of adults.
There are more than 5,400 species of amphibians alive today, and these belong to three groups: caecilians, salamanders, and frogs and toads. Caecilians live in tropical areas of Asia, Africa, and South America. Looking like earthworms or snakes, they lack legs (Fig. 6, p. 423). Salamanders (Fig. 7, p. 423) live in wooded areas of North America. They don’t develop as tadpoles, but most of them lose gills and grow lungs during their development. Frogs and Toads make up about 90% of all amphibians. They are very similar to one another; in fact toads are a type of frog. They live all over the world, except for very cold places. Some frogs sing to communicate messages that help in attracting mates and marking territories.