Growing old is part of being a living thing. Every plant and animal must go through a cycle of life that involves a beginning, a middle, and an end. Actually, as soon as we are born we begin aging or growing older. But when we talk of growing old we think of the physical changes that occur when bodies cannot grow and repair themselves as they once did.
At about age 30 the signs of aging start to appear, though for most people the physical changes are not really obvious until many years later.
The hours in a school day and the amount of time a teacher can spend individually with students are limited. As a result, teachers need the understanding and help of their students, parents, and families in supporting classroom instruction and learning outside school hours. Homework has been part of school life since the beginning of formal schooling in the United States. It is important because it can improve your thinking and memory.
It can help you develop positive study habits and skills that will serve you well throughout your life. Homework also can encourage you to use time well, learn independently, and take responsibility for your work. And if you have an adult supervise you, it benefits them as well. It helps your mom and dad see what you are learning in school and helps your family communicate with you and your teachers.
Any group of birds, goats, or sheep can be referred to as a flock, but each feathered breed has its own proper title. Hawks travel in casts, while it’s a bevy of quail, a host of sparrows, and a covey of partridges.
Swans move in herds, and peacocks in musters, while a flock of herons is called a siege. A group of geese is properly called a gaggle, but only When they’re on the ground. In the air they are a skein.
The phrase charley horse has its roots in baseball. At the beginning of the twentieth century, groundskeepers often used old and lame horses to pull the equipment used to keep the playing field in top condition.
The Baltimore Orioles had a player named Charley Esper, who, after years of injuries, walked with pain. Because his limp reminded his teammates of the groundskeeper’s lame horse, they called Esper “Charley Horse.”
The coco de mer tree, a palm that only grows today on two islands in the Seychelles, produces both the largest seed (each weighs about 44 pounds [20 kilograms]) and the largest nut in the world. The nut, which takes six to seven years to mature and another two years to germinate, is sometimes called the sea coconut or Seychelles nut. When early explorers first discovered the nut, they thought it came from a mythical tree at the bottom of the sea.
Sixteenth-century European nobles decorated the nut with jewels as collectibles for their private galleries. Today, the coco de mer is a rare protected species.
Once seeds are fully developed, they need a good place to grow. If they just fell to the ground beneath their parent plant, they would struggle, competing against each other for sunlight, water, and minerals. Most seeds need to travel—by wind, water, or with the help of insects and other animals—to better places to germinate, or start to grow into new plants. Some seeds, like those from conifer and maple trees, have wings attached. Others, like those of dandelions, have parachutes made of tiny hairs. Both features allow the seeds to be carried great distances by the wind, and they sometimes land in spots that are good for germination. Water carries other seeds to good growing places; the hard, watertight shell of a coconut, for instance, allows it to travel many miles at sea before finding a beach where conditions are suitable for growth.
Seeds sometimes have to wait a long time before they find good places to grow, places where the sun, moisture, and temperature are right. Most seeds are designed for the wait, protected by a hard outer pod (except those of conifers). Some seeds wait years to germinate, and some just never do. But inside each seed pod is a baby plant, or embryo, and endosperm, a supply of starchy food that will be used for early growth if germination takes place. Then a tiny root will reach down into the soil, and a tiny green shoot will reach up, toward the light.
Indeed, it does. A Venus flytrap is a carnivorous plant that attracts, captures, and kills insects and digests and absorbs their nutrients. The leaves of the Venus flytrap, Which can open wide, have short, stiff hairs called trigger hairs. When anything touches these hairs enough to bend them, the two lobes of the leaves snap shut, trapping whatever is inside. The “trap” will shut in less than a second, capturing flies and other insects.
When the trap closes over its prey, finger-like projections called cilia keep larger insects inside. In a few minutes the trap shuts tightly and forms an air-tight seal in order to keep its digestive fluids inside. These fluids help the plant digest prey. At the end of the digestive process, which takes from 5 to 12 days, the trap reabsorbs the digestive fluid and reopens. The leftover parts of the insect blow away in the wind or are washed away by rain.
Frogs are able to make their croaking noises because they have simple vocal cords that have two slits in the bottom of the mouth. These slits open into what is called a vocal pouch. When air passes from the lungs through the vocal cords, a sound is produced. The inflating and deflating vocal pouch makes the sound louder or quieter.
That sound changes depending on the kind of frog there are as many different kinds of croaks as there are frogs! Frogs croak for the same reasons that many animals make noises: to track down and then select a mate, and to protect their territory from other male frogs.
Dams, which are structures that hold back water, have been built since ancient times. They are usually made of earth, rock, brick, or concrete—or a combination of these things. They are constructed to control the flow of water in a river, and they are built for a number of reasons. One reason is to prevent flooding. Heavy rains in high country may cause water levels in a river to rise. As the river flows downhill, it may overflow its banks, flooding communities located downstream. A dam can prevent this by stopping or slowing rushing water, allowing it to be released at a controlled rate. Dams are also frequently used to store water for general use and farming. When a river’s flow is restricted by a dam, water often spreads out behind the dam to form a lake or reservoir in the river valley. That water can then be used as needed, preventing water shortages and crop damage during long periods of dry weather.
A great number of dams today are used to make electricity. Such hydroelectric dams are built very tall, to create a great difference in the height of the water level behind and in front of it. High water behind a dam passes through gates in the dam wall that allow it to fall to the river far below. As the water falls, it flows past huge blades called turbines; the turbines run generators that make electricity. One of the world’s largest and most productive hydroelectric dams is the Hoover Dam, located on the Colorado River between Nevada and Arizona. Built in the 1930s, it is 726 feet (221 meters) high and 1,244 feet (379 meters) long. Its reservoir (Lake Mead)—the world’s largest— supplies water to several states, allowing huge regions of naturally dry terrain in southern California, Arizona, and Mexico to flourish. Many modern dams are used for all three purposes: flood control, water storage, and hydroelectric power.
Birds migrate—or move regularly from one place to another—for several reasons, including warmth and the availability of food and water. Many species of birds mate and nest in specific areas of the world. Most of these areas are only comfortable during the warmer months of the year, so when the cold weather arrives birds migrate to warmer climates. These trips can be as long as thousands of miles. For example, the American golden plover breeds north of Canada and Alaska during the Northern Hemisphere’s spring and summer.
In the Northern Hemisphere’s fall, the plovers travel to southeastern South America to spend the “winter”—which is the summer season in the Southern Hemisphere—allowing the birds to find plenty of food. When spring arrives again in the Northern Hemisphere, the trip is reversed, and the plovers migrate back to the northern nesting grounds to breed.